Next Issue
Previous Issue

E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Table of Contents

Materials, Volume 8, Issue 12 (December 2015), Pages 7997-8889

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-63
Export citation of selected articles as:

Research

Jump to: Review, Other

Open AccessFeature PaperArticle Investigation of Supported Pd-Based Electrocatalysts for the Oxygen Reduction Reaction: Performance, Durability and Methanol Tolerance
Materials 2015, 8(12), 7997-8008; doi:10.3390/ma8125438
Received: 12 October 2015 / Revised: 9 November 2015 / Accepted: 16 November 2015 / Published: 25 November 2015
Cited by 9 | PDF Full-text (2345 KB) | HTML Full-text | XML Full-text
Abstract
Next generation cathode catalysts for direct methanol fuel cells (DMFCs) must have high catalytic activity for the oxygen reduction reaction (ORR), a lower cost than benchmark Pt catalysts, and high stability and high tolerance to permeated methanol. In this study, palladium catalysts supported
[...] Read more.
Next generation cathode catalysts for direct methanol fuel cells (DMFCs) must have high catalytic activity for the oxygen reduction reaction (ORR), a lower cost than benchmark Pt catalysts, and high stability and high tolerance to permeated methanol. In this study, palladium catalysts supported on titanium suboxides (Pd/TinO2n–1) were prepared by the sulphite complex route. The aim was to improve methanol tolerance and lower the cost associated with the noble metal while enhancing the stability through the use of titanium-based support; 30% Pd/Ketjenblack (Pd/KB) and 30% Pd/Vulcan (Pd/Vul) were also synthesized for comparison, using the same methodology. The catalysts were ex-situ characterized by physico-chemical analysis and investigated for the ORR to evaluate their activity, stability, and methanol tolerance properties. The Pd/KB catalyst showed the highest activity towards the ORR in perchloric acid solution. All Pd-based catalysts showed suitable tolerance to methanol poisoning, leading to higher ORR activity than a benchmark Pt/C catalyst in the presence of low methanol concentration. Among them, the Pd/TinO2n–1 catalyst showed a very promising stability compared to carbon-supported Pd samples in an accelerated degradation test of 1000 potential cycles. These results indicate good perspectives for the application of Pd/TinO2n–1 catalysts in DMFC cathodes. Full article
(This article belongs to the Special Issue Electrode Materials)
Figures

Open AccessArticle Development of β Type Ti23Mo-45S5 Bioglass Nanocomposites for Dental Applications
Materials 2015, 8(12), 8032-8046; doi:10.3390/ma8125441
Received: 17 September 2015 / Revised: 13 November 2015 / Accepted: 16 November 2015 / Published: 25 November 2015
Cited by 1 | PDF Full-text (4785 KB) | HTML Full-text | XML Full-text
Abstract
Titanium β-type alloys attract attention as biomaterials for dental applications. The aim of this work was the synthesis of nanostructured β type Ti23Mo-x wt % 45S5 Bioglass (x = 0, 3 and 10) composites by mechanical alloying and powder metallurgy methods
[...] Read more.
Titanium β-type alloys attract attention as biomaterials for dental applications. The aim of this work was the synthesis of nanostructured β type Ti23Mo-x wt % 45S5 Bioglass (x = 0, 3 and 10) composites by mechanical alloying and powder metallurgy methods and their characterization. The crystallization of the amorphous material upon annealing led to the formation of a nanostructured β type Ti23Mo alloy with a grain size of approximately 40 nm. With the increase of the 45S5 Bioglass contents in Ti23Mo, nanocomposite increase of the α-phase is noticeable. The electrochemical treatment in phosphoric acid electrolyte resulted in a porous surface, followed by bioactive ceramic Ca-P deposition. Corrosion resistance potentiodynamic testing in Ringer solution at 37 °C showed a positive effect of porosity and Ca-P deposition on nanostructured Ti23Mo 3 wt % 45S5 Bioglass nanocomposite. The contact angles of glycerol on the nanostructured Ti23Mo alloy were determined and show visible decrease for bulk Ti23Mo 3 wt % 45S5 Bioglass and etched Ti23Mo 3 wt % 45S5 Bioglass nanocomposites. In vitro tests culture of normal human osteoblast cells showed very good cell proliferation, colonization, and multilayering. The present study demonstrated that porous Ti23Mo 3 wt % 45S5 Bioglass nanocomposite is a promising biomaterial for bone tissue engineering. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle Experimental Analysis of Dynamic Effects of FRP Reinforced Masonry Vaults
Materials 2015, 8(12), 8059-8071; doi:10.3390/ma8125445
Received: 2 November 2015 / Revised: 23 November 2015 / Accepted: 24 November 2015 / Published: 27 November 2015
Cited by 2 | PDF Full-text (3821 KB) | HTML Full-text | XML Full-text
Abstract
An increasing interest in the preservation of historic structures has produced a need for new methods for reinforcing curved masonry structures, such as arches and vaults. These structures are generally very ancient, have geometries and materials which are poorly defined and have been
[...] Read more.
An increasing interest in the preservation of historic structures has produced a need for new methods for reinforcing curved masonry structures, such as arches and vaults. These structures are generally very ancient, have geometries and materials which are poorly defined and have been exposed to long-term historical movements and actions. Consequently, they are often in need of repair or reinforcement. This article presents the results of an experimental study carried out in the laboratory and during on-site testing to investigate the behaviour of brick masonry vaults under dynamic loading strengthened with FRPs (Fiber Reinforced Polymers). For the laboratory tests, the brick vaults were built with solid sanded clay bricks and weak mortar and were tested under dynamic loading. The experimental tests were designed to facilitate analysis of the dynamic behaviour of undamaged, damaged and reinforced vaulted structures. On-site tests were carried out on an earthquake-damaged thin brick vault of an 18th century aristocratic residence in the city of L’Aquila, Italy. The provision of FRP reinforcement is shown to re-establish elastic behavior previously compromised by time induced damage in the vaults. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Order Reconstruction in a Nanoconfined Nematic Liquid Crystal between Two Coaxial Cylinders
Materials 2015, 8(12), 8072-8086; doi:10.3390/ma8125446
Received: 8 October 2015 / Revised: 13 November 2015 / Accepted: 16 November 2015 / Published: 30 November 2015
Cited by 1 | PDF Full-text (2882 KB) | HTML Full-text | XML Full-text
Abstract
The dynamics of a disclination loop (s = ±1/2) in nematic liquid crystals constrained between two coaxial cylinders were investigated based on two-dimensional Landau–de Gennes tensorial formalism by using a finite-difference iterative method. The effect of thickness (d = R2
[...] Read more.
The dynamics of a disclination loop (s = ±1/2) in nematic liquid crystals constrained between two coaxial cylinders were investigated based on two-dimensional Landau–de Gennes tensorial formalism by using a finite-difference iterative method. The effect of thickness (d = R2R1, where R1 and R2 represent the internal and external radii of the cylindrical cavity, respectively) on the director distribution of the defect was simulated using different R1 values. The results show that the order reconstruction occurs at a critical value of dc, which decreases with increasing inner ratio R1. The loop also shrinks, and the defect center deviates from the middle of the system, which is a non-planar structure. The deviation decreases with decreasing d or increasing R1, implying that the system tends to be a planar cell. Two models were then established to analyze the combined effect of non-planar geometry and electric field. The common action of these parameters facilitates order reconstruction, whereas their opposite action complicates the process. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Influence of Hot-Etching Surface Treatment on Zirconia/Resin Shear Bond Strength
Materials 2015, 8(12), 8087-8096; doi:10.3390/ma8125409
Received: 9 September 2015 / Revised: 20 October 2015 / Accepted: 2 November 2015 / Published: 30 November 2015
PDF Full-text (1982 KB) | HTML Full-text | XML Full-text
Abstract
This study was designed to evaluate the effect of hot-etching surface treatment on the shear bond strength between zirconia ceramics and two commercial resin cements. Ceramic cylinders (120 units; length: 2.5 mm; diameter: 4.7 mm) were randomly divided into 12 groups (n
[...] Read more.
This study was designed to evaluate the effect of hot-etching surface treatment on the shear bond strength between zirconia ceramics and two commercial resin cements. Ceramic cylinders (120 units; length: 2.5 mm; diameter: 4.7 mm) were randomly divided into 12 groups (n = 10) according to different surface treatments (blank control; airborne-particle-abrasion; hot-etching) and different resin cements (Panavia F2.0; Superbond C and B) and whether or not a thermal cycling fatigue test (5°–55° for 5000 cycles) was performed. Flat enamel surfaces, mounted in acrylic resin, were bonded to the zirconia discs (diameter: 4.7 mm). All specimens were subjected to shear bond strength testing using a universal testing machine with a crosshead speed of 1 mm/min. All data were statistically analyzed using one-way analysis of variance and multiple-comparison least significant difference tests (α = 0.05). Hot-etching treatment produced higher bond strengths than the other treatment with both resin cements. The shear bond strength of all groups significantly decreased after the thermal cycling test; except for the hot-etching group that was cemented with Panavia F2.0 (p < 0.05). Surface treatment of zirconia with hot-etching solution enhanced the surface roughness and bond strength between the zirconia and the resin cement. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Open AccessArticle Synthesis of Biocompatible Hydroxyapatite Using Chitosan Oligosaccharide as a Template
Materials 2015, 8(12), 8097-8105; doi:10.3390/ma8125440
Received: 26 October 2015 / Revised: 16 November 2015 / Accepted: 20 November 2015 / Published: 30 November 2015
Cited by 3 | PDF Full-text (4735 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a novel biocompatible hydroxyapatite (HA) was synthesized by using chitosan oligosaccharide (COS) as a template. These HA samples were studied by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The biocompatibility
[...] Read more.
In this study, a novel biocompatible hydroxyapatite (HA) was synthesized by using chitosan oligosaccharide (COS) as a template. These HA samples were studied by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The biocompatibility of HA samples was evaluated via cell viability, cell morphology and alkaline phosphatase staining of MG-63 cell lines. The results show that HA synthesized in the presence of COS was favorable to proliferation and osteogenic differentiation of MG-63 cells. These hydroxyapatites are potentially attractive biomaterials for bone tissue engineering applications. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle Processing and Characterization of Cellulose Nanocrystals/Polylactic Acid Nanocomposite Films
Materials 2015, 8(12), 8106-8116; doi:10.3390/ma8125447
Received: 30 September 2015 / Revised: 30 October 2015 / Accepted: 23 November 2015 / Published: 1 December 2015
Cited by 14 | PDF Full-text (2836 KB) | HTML Full-text | XML Full-text
Abstract
The focus of this study is to examine the effect of cellulose nanocrystals (CNC) on the properties of polylactic acid (PLA) films. The films are fabricated via melt compounding and melt fiber spinning followed by compression molding. Film fracture morphology, thermal properties, crystallization
[...] Read more.
The focus of this study is to examine the effect of cellulose nanocrystals (CNC) on the properties of polylactic acid (PLA) films. The films are fabricated via melt compounding and melt fiber spinning followed by compression molding. Film fracture morphology, thermal properties, crystallization behavior, thermo-mechanical behavior, and mechanical behavior were determined as a function of CNC content using scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, dynamic mechanical analysis, and tensile testing. Film crystallinity increases with increasing CNC content indicating CNC act as nucleating agents, promoting crystallization. Furthermore, the addition of CNC increased the film storage modulus and slightly broadened the glass transition region. Full article
(This article belongs to the Special Issue Green Composites)
Open AccessArticle Physical Characteristics of Medical Textile Prostheses Designed for Hernia Repair: A Comprehensive Analysis of Select Commercial Devices
Materials 2015, 8(12), 8148-8168; doi:10.3390/ma8125453
Received: 15 October 2015 / Revised: 17 November 2015 / Accepted: 25 November 2015 / Published: 2 December 2015
Cited by 2 | PDF Full-text (19583 KB) | HTML Full-text | XML Full-text
Abstract
Inguinal hernia repairs are among the most frequent operations performed worldwide. This study aims to provide further understanding of structural characteristics of hernia prostheses, and better comprehensive evaluation. Weight, porosity, pore size and other physical characteristics were evaluated; warp knitting structures were thoroughly
[...] Read more.
Inguinal hernia repairs are among the most frequent operations performed worldwide. This study aims to provide further understanding of structural characteristics of hernia prostheses, and better comprehensive evaluation. Weight, porosity, pore size and other physical characteristics were evaluated; warp knitting structures were thoroughly discussed. Two methods referring to ISO 7198:1998, i.e., weight method and area method, were employed to calculate porosity. Porosity ranged from 37.3% to 69.7% measured by the area method, and 81.1% to 89.6% by the weight method. Devices with two-guide bar structures displayed both higher porosity (57.7%–69.7%) and effective porosity (30.8%–60.1%) than single-guide bar structure (37.3%–62.4% and 0%–5.9%, respectively). Filament diameter, stitch density and loop structure combined determined the thickness, weight and characteristics of pores. They must be well designed to avoid zero effective porosity regarding a single-bar structure. The area method was more effective in characterizing flat sheet meshes while the weight method was perhaps more accurate in describing stereoscopic void space for 3D structure devices. This article will give instructive clues for engineers to improve mesh structures, and better understanding of warp knitting meshes for surgeons. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Figures

Open AccessArticle Electrical Properties and Interfacial Studies of HfxTi1–xO2 High Permittivity Gate Insulators Deposited on Germanium Substrates
Materials 2015, 8(12), 8169-8182; doi:10.3390/ma8125454
Received: 24 September 2015 / Revised: 17 November 2015 / Accepted: 24 November 2015 / Published: 2 December 2015
Cited by 1 | PDF Full-text (4012 KB) | HTML Full-text | XML Full-text
Abstract
In this research, the hafnium titanate oxide thin films, TixHf1–xO2, with titanium contents of x = 0, 0.25, 0.9, and 1 were deposited on germanium substrates by atomic layer deposition (ALD) at 300 °C. The approximate
[...] Read more.
In this research, the hafnium titanate oxide thin films, TixHf1–xO2, with titanium contents of x = 0, 0.25, 0.9, and 1 were deposited on germanium substrates by atomic layer deposition (ALD) at 300 °C. The approximate deposition rates of 0.2 Å and 0.17 Å per cycle were obtained for titanium oxide and hafnium oxide, respectively. X-ray Photoelectron Spectroscopy (XPS) indicates the formation of GeOx and germanate at the interface. X-ray diffraction (XRD) indicates that all the thin films remain amorphous for this deposition condition. The surface roughness was analyzed using an atomic force microscope (AFM) for each sample. The electrical characterization shows very low hysteresis between ramp up and ramp down of the Capacitance-Voltage (CV) and the curves are indicative of low trap densities. A relatively large leakage current is observed and the lowest leakage current among the four samples is about 1 mA/cm2 at a bias of 0.5 V for a Ti0.9Hf0.1O2 sample. The large leakage current is partially attributed to the deterioration of the interface between Ge and TixHf1–xO2 caused by the oxidation source from HfO2. Consideration of the energy band diagrams for the different materials systems also provides a possible explanation for the observed leakage current behavior. Full article
(This article belongs to the Special Issue Atomic Layer Deposition of Functional Materials)
Figures

Open AccessFeature PaperArticle The Effect of Niobium Doping on the Electrical Properties of 0.4(Bi0.5K0.5)TiO3-0.6BiFeO3 Lead-Free Piezoelectric Ceramics
Materials 2015, 8(12), 8183-8194; doi:10.3390/ma8125457
Received: 1 October 2015 / Revised: 13 November 2015 / Accepted: 19 November 2015 / Published: 2 December 2015
Cited by 3 | PDF Full-text (4017 KB) | HTML Full-text | XML Full-text
Abstract
Ceramics in the system (Bi0.5K0.5)TiO3-BiFeO3 have good electromechanical properties and temperature stability. However, the high conductivity inherent in BiFeO3-based ceramics complicates measurement of the ferroelectric properties. In the present work, doping with niobium (Nb)
[...] Read more.
Ceramics in the system (Bi0.5K0.5)TiO3-BiFeO3 have good electromechanical properties and temperature stability. However, the high conductivity inherent in BiFeO3-based ceramics complicates measurement of the ferroelectric properties. In the present work, doping with niobium (Nb) is carried out to reduce the conductivity of (Bi0.5K0.5)TiO3-BiFeO3. Powders of composition 0.4(K0.5Bi0.5)Ti1−xNbxO3-0.6BiFe1−xNbxO3 (x = 0, 0.01 and 0.03) are prepared by the mixed oxide method and sintered at 1050 °C for 1 h. The effect of Nb doping on the structure is examined by X-ray diffraction. The microstructure is examined by scanning electron microscopy. The variation in relative permittivity with temperature is measured using an impedance analyzer. Ferroelectric properties are measured at room temperature using a Sawyer Tower circuit. Piezoelectric properties are measured using a d33 meter and a contact type displacement sensor. All the samples have high density, a rhombohedral unit cell and equiaxed, micron-sized grains. All the samples show relaxor-like behavior. Nb doping causes a reduction in conductivity by one to two orders of magnitude at 200 °C. The samples have narrow P-E loops reminiscent of a linear dielectric. The samples all possess bipolar butterfly S-E loops characteristic of a classic ferroelectric material. Nb doping causes a decrease in d33 and Smax/Emax. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
Figures

Open AccessArticle An Investigation of the Microstructure of an Intermetallic Layer in Welding Aluminum Alloys to Steel by MIG Process
Materials 2015, 8(12), 8246-8254; doi:10.3390/ma8125444
Received: 27 August 2015 / Revised: 8 November 2015 / Accepted: 17 November 2015 / Published: 2 December 2015
Cited by 5 | PDF Full-text (4645 KB) | HTML Full-text | XML Full-text
Abstract
Butt joints of A5052 aluminum alloy and SS400 steel, with a new type of chamfered edge, are welded by means of metal inert gas welding and ER4043 Al-Si filler metal. The microhardness and microstructure of the joint are investigated. An intermetallic layer is
[...] Read more.
Butt joints of A5052 aluminum alloy and SS400 steel, with a new type of chamfered edge, are welded by means of metal inert gas welding and ER4043 Al-Si filler metal. The microhardness and microstructure of the joint are investigated. An intermetallic layer is found on the surface of the welding seam and SS400 steel sheet. The hardness of the intermetallic layer is examined using the Vickers hardness test. The average hardness values at the Intermetallic (IMC) layer zone and without the IMC layer zone were higher than that of the welding wire ER4043. The tensile strength test showed a fracture at the intermetallic layer when the tensile strength is 225.9 MPa. The tensile value test indicated the average of welds was equivalent to the 85% tensile strength of the A5052 aluminum alloy. The thickness of the intermetallic layers is non-uniform at different positions with the ranges from 1.95 to 5 μm. The quality of the butt joint is better if the intermetallic layer is minimized. The Si crystals which appeared at the welding seam, indicating that this element participated actively during the welding process, also contributed to the IMC layer’s formation. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Advances on the Failure Analysis of the Dam—Foundation Interface of Concrete Dams
Materials 2015, 8(12), 8255-8278; doi:10.3390/ma8125442
Received: 10 October 2015 / Revised: 9 November 2015 / Accepted: 13 November 2015 / Published: 2 December 2015
Cited by 1 | PDF Full-text (1722 KB) | HTML Full-text | XML Full-text
Abstract
Failure analysis of the dam-foundation interface in concrete dams is characterized by complexity, uncertainties on models and parameters, and a strong non-linear softening behavior. In practice, these uncertainties are dealt with a well-structured mixture of experience, best practices and prudent, conservative design approaches
[...] Read more.
Failure analysis of the dam-foundation interface in concrete dams is characterized by complexity, uncertainties on models and parameters, and a strong non-linear softening behavior. In practice, these uncertainties are dealt with a well-structured mixture of experience, best practices and prudent, conservative design approaches based on the safety factor concept. Yet, a sound, deep knowledge of some aspects of this failure mode remain unveiled, as they have been offset in practical applications by the use of this conservative approach. In this paper we show a strategy to analyse this failure mode under a reliability-based approach. The proposed methodology of analysis integrates epistemic uncertainty on spatial variability of strength parameters and data from dam monitoring. The purpose is to produce meaningful and useful information regarding the probability of occurrence of this failure mode that can be incorporated in risk-informed dam safety reviews. In addition, relationships between probability of failure and factors of safety are obtained. This research is supported by a more than a decade of intensive professional practice on real world cases and its final purpose is to bring some clarity, guidance and to contribute to the improvement of current knowledge and best practices on such an important dam safety concern. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
Figures

Open AccessArticle Polypropylene/Short Glass Fibers Composites: Effects of Coupling Agents on Mechanical Properties, Thermal Behaviors, and Morphology
Materials 2015, 8(12), 8279-8291; doi:10.3390/ma8125451
Received: 13 October 2015 / Revised: 16 November 2015 / Accepted: 20 November 2015 / Published: 2 December 2015
Cited by 5 | PDF Full-text (8315 KB) | HTML Full-text | XML Full-text
Abstract
This study uses the melt compounding method to produce polypropylene (PP)/short glass fibers (SGF) composites. PP serves as matrix while SGF serves as reinforcement. Two coupling agents, maleic anhydride grafted polypropylene, (PP-g-MA) and maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MA) are incorporated in
[...] Read more.
This study uses the melt compounding method to produce polypropylene (PP)/short glass fibers (SGF) composites. PP serves as matrix while SGF serves as reinforcement. Two coupling agents, maleic anhydride grafted polypropylene, (PP-g-MA) and maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MA) are incorporated in the PP/SGF composites during the compounding process, in order to improve the interfacial adhesion and create diverse desired properties of the composites. According to the mechanical property evaluations, increasing PP-g-MA as a coupling agent provides the composites with higher tensile, flexural, and impact properties. In contrast, increasing SEBS-g-MA as a coupling agent provides the composites with decreasing tensile and flexural strengths, but also increasing impact strength. The DSC results indicate that using either PP-g-MA or SEBS-g-MA as the coupling agent increases the crystallization temperature. However, the melting temperature of PP barely changes. The spherulitic morphology results show that PP has a smaller spherulite size when it is processed with PP-g-MA or SEBS-g-MA as the coupling agent. The SEM results indicate that SGF is evenly distributed in PP matrices, but there are distinct voids between these two materials, indicating a poor interfacial adhesion. After PP-g-MA or SEBS-g-MA is incorporated, SGF can be encapsulated by PP, and the voids between them are fewer and indistinctive. This indicates that the coupling agents can effectively improve the interfacial compatibility between PP and SGF, and as a result improves the diverse properties of PP/SGF composites. Full article
(This article belongs to the Special Issue Selected Papers from ICETI2014)
Open AccessArticle Microstructural Changes Due to Alkali-Silica Reaction during Standard Mortar Test
Materials 2015, 8(12), 8292-8303; doi:10.3390/ma8125450
Received: 5 August 2015 / Revised: 16 November 2015 / Accepted: 17 November 2015 / Published: 2 December 2015
Cited by 1 | PDF Full-text (5773 KB) | HTML Full-text | XML Full-text
Abstract
The microstructural development of mortar bars with silica glass aggregate undergoing alkali-silica reaction (ASR) under the conditions of American Society for Testing and Materials (ASTM) Standard Test C1260 was analyzed using scanning electron microscopy and qualitative X-ray microanalysis. Cracking in the aggregate, the
[...] Read more.
The microstructural development of mortar bars with silica glass aggregate undergoing alkali-silica reaction (ASR) under the conditions of American Society for Testing and Materials (ASTM) Standard Test C1260 was analyzed using scanning electron microscopy and qualitative X-ray microanalysis. Cracking in the aggregate, the hydrated paste, and the paste-aggregate interface was important in the development of the microstructure. Cracks were characterized according to their location, their relationship to other cracks, and whether they are filled with ASR gel. Expansion of the bars was approximately 1% at 12 days and 2% at 53 days. They fell apart by 63 days. The bars contained two zones, an inner region that was undergoing ASR and an outer and much more highly damaged zone that extended further inward over time. Evidence of ASR was present even during the period when specimens were immersed in water, prior to immersion in NaOH solution. Full article
Open AccessFeature PaperArticle Functional Piezocrystal Characterisation under Varying Conditions
Materials 2015, 8(12), 8304-8326; doi:10.3390/ma8125456
Received: 29 September 2015 / Revised: 18 November 2015 / Accepted: 20 November 2015 / Published: 2 December 2015
Cited by 5 | PDF Full-text (4235 KB) | HTML Full-text | XML Full-text
Abstract
Piezocrystals, especially the relaxor-based ferroelectric crystals, have been subject to intense investigation and development within the past three decades, motivated by the performance advantages offered by their ultrahigh piezoelectric coefficients and higher electromechanical coupling coefficients than piezoceramics. Structural anisotropy of piezocrystals also provides
[...] Read more.
Piezocrystals, especially the relaxor-based ferroelectric crystals, have been subject to intense investigation and development within the past three decades, motivated by the performance advantages offered by their ultrahigh piezoelectric coefficients and higher electromechanical coupling coefficients than piezoceramics. Structural anisotropy of piezocrystals also provides opportunities for devices to operate in novel vibration modes, such as the d36 face shear mode, with domain engineering and special crystal cuts. These piezocrystal characteristics contribute to their potential usage in a wide range of low- and high-power ultrasound applications. In such applications, conventional piezoelectric materials are presently subject to varying mechanical stress/pressure, temperature and electric field conditions. However, as observed previously, piezocrystal properties are significantly affected by a single such condition or a combination of conditions. Laboratory characterisation of the piezocrystal properties under these conditions is therefore essential to fully understand these materials and to allow electroacoustic transducer design in realistic scenarios. This will help to establish the extent to which these high performance piezocrystals can replace conventional piezoceramics in demanding applications. However, such characterisation requires specific experimental arrangements, examples of which are reported here, along with relevant results. The measurements include high frequency-resolution impedance spectroscopy with the piezocrystal material under mechanical stress 0–60 MPa, temperature 20–200 °C, high electric AC drive and DC bias. A laser Doppler vibrometer and infrared thermal camera are also integrated into the measurement system for vibration mode shape scanning and thermal conditioning with high AC drive. Three generations of piezocrystal have been tested: (I) binary, PMN-PT; (II) ternary, PIN-PMN-PT; and (III) doped ternary, Mn:PIN-PMN-PT. Utilising resonant mode analysis, variations in elastic, dielectric and piezoelectric constants and coupling coefficients have been analysed, and tests with thermal conditioning have been carried out to assess the stability of the piezocrystals under high power conditions. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
Open AccessArticle Phononic Band Gaps in 2D Quadratic and 3D Cubic Cellular Structures
Materials 2015, 8(12), 8327-8337; doi:10.3390/ma8125463
Received: 22 September 2015 / Revised: 26 November 2015 / Accepted: 27 November 2015 / Published: 2 December 2015
Cited by 6 | PDF Full-text (1990 KB) | HTML Full-text | XML Full-text
Abstract
The static and dynamic mechanical behaviour of cellular materials can be designed by the architecture of the underlying unit cell. In this paper, the phononic band structure of 2D and 3D cellular structures is investigated. It is shown how the geometry of the
[...] Read more.
The static and dynamic mechanical behaviour of cellular materials can be designed by the architecture of the underlying unit cell. In this paper, the phononic band structure of 2D and 3D cellular structures is investigated. It is shown how the geometry of the unit cell influences the band structure and eventually leads to full band gaps. The mechanism leading to full band gaps is elucidated. Based on this knowledge, a 3D cellular structure with a broad full band gap is identified. Furthermore, the dependence of the width of the gap on the geometry parameters of the unit cell is presented. Full article
(This article belongs to the Special Issue Cellular Materials: Design and Optimisation)
Figures

Open AccessArticle Very High Cycle Fatigue Failure Analysis and Life Prediction of Cr-Ni-W Gear Steel Based on Crack Initiation and Growth Behaviors
Materials 2015, 8(12), 8338-8354; doi:10.3390/ma8125459
Received: 10 October 2015 / Revised: 17 November 2015 / Accepted: 18 November 2015 / Published: 2 December 2015
Cited by 1 | PDF Full-text (4185 KB) | HTML Full-text | XML Full-text
Abstract
The unexpected failures of structural materials in very high cycle fatigue (VHCF) regime have been a critical issue in modern engineering design. In this study, the VHCF property of a Cr-Ni-W gear steel was experimentally investigated under axial loading with the stress ratio
[...] Read more.
The unexpected failures of structural materials in very high cycle fatigue (VHCF) regime have been a critical issue in modern engineering design. In this study, the VHCF property of a Cr-Ni-W gear steel was experimentally investigated under axial loading with the stress ratio of R = −1, and a life prediction model associated with crack initiation and growth behaviors was proposed. Results show that the Cr-Ni-W gear steel exhibits the constantly decreasing S-N property without traditional fatigue limit, and the fatigue strength corresponding to 109 cycles is around 485 MPa. The inclusion-fine granular area (FGA)-fisheye induced failure becomes the main failure mechanism in the VHCF regime, and the local stress around the inclusion play a key role. By using the finite element analysis of representative volume element, the local stress tends to increase with the increase of elastic modulus difference between inclusion and matrix. The predicted crack initiation life occupies the majority of total fatigue life, while the predicted crack growth life is only accounts for a tiny fraction. In view of the good agreement between the predicted and experimental results, the proposed VHCF life prediction model involving crack initiation and growth can be acceptable for inclusion-FGA-fisheye induced failure. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
Open AccessArticle Polar Order Evolutions near the Rhombohedral to Pseudocubic and Tetragonal to Pseudocubic Phase Boundaries of the BiFeO3-BaTiO3 System
Materials 2015, 8(12), 8355-8365; doi:10.3390/ma8125462
Received: 31 July 2015 / Revised: 23 October 2015 / Accepted: 27 October 2015 / Published: 2 December 2015
Cited by 2 | PDF Full-text (1844 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Solid solutions of (1-x)BiFeO3-xBaTiO3 (BF-BT, 0.05 ≤ x ≤ 0.98) were prepared and characterized. It was found that the dielectric constant εm, remnant polarization Pr and piezoelectric coefficient d33 reach their maximum
[...] Read more.
Solid solutions of (1-x)BiFeO3-xBaTiO3 (BF-BT, 0.05 ≤ x ≤ 0.98) were prepared and characterized. It was found that the dielectric constant εm, remnant polarization Pr and piezoelectric coefficient d33 reach their maximum values near the rhombohedral–pseudocubic phase boundary. In particular, the 0.7BF-0.3BT composition shows large polarization (Pr > 20 μC/cm2) and a temperature-stable piezoelectric property (d33 > 100 pC/N when the annealing temperature is lower than ~400 °C). Near the tetragonal–pseudocubic phase boundary, εm and Pr decrease, and the piezoelectric property vanishes when the BF content reaches 4 mol %. Full article
(This article belongs to the Section Materials for Energy Applications)
Open AccessArticle Formation of Micro- and Nanostructures on the Nanotitanium Surface by Chemical Etching and Deposition of Titania Films by Atomic Layer Deposition (ALD)
Materials 2015, 8(12), 8366-8377; doi:10.3390/ma8125460
Received: 9 October 2015 / Revised: 19 November 2015 / Accepted: 24 November 2015 / Published: 2 December 2015
Cited by 5 | PDF Full-text (8787 KB) | HTML Full-text | XML Full-text
Abstract
In this study, an integrated approach was used for the preparation of a nanotitanium-based bioactive material. The integrated approach included three methods: severe plastic deformation (SPD), chemical etching and atomic layer deposition (ALD). For the first time, it was experimentally shown that the
[...] Read more.
In this study, an integrated approach was used for the preparation of a nanotitanium-based bioactive material. The integrated approach included three methods: severe plastic deformation (SPD), chemical etching and atomic layer deposition (ALD). For the first time, it was experimentally shown that the nature of the etching medium (acidic or basic Piranha solutions) and the etching time have a significant qualitative impact on the nanotitanium surface structure both at the nano- and microscale. The etched samples were coated with crystalline biocompatible TiO2 films with a thickness of 20 nm by Atomic Layer Deposition (ALD). Comparative study of the adhesive and spreading properties of human osteoblasts MG-63 has demonstrated that presence of nano- and microscale structures and crystalline titanium oxide on the surface of nanotitanium improve bioactive properties of the material. Full article
(This article belongs to the Special Issue Atomic Layer Deposition of Functional Materials)
Open AccessArticle Removal of Chromium(VI) from Aqueous Solutions Using Fe3O4 Magnetic Polymer Microspheres Functionalized with Amino Groups
Materials 2015, 8(12), 8378-8391; doi:10.3390/ma8125461
Received: 5 September 2015 / Revised: 23 November 2015 / Accepted: 25 November 2015 / Published: 3 December 2015
Cited by 5 | PDF Full-text (3279 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Magnetic polymer microspheres (MPMs) using glycidylmethacrylate (GMA) as a functional monomer were synthesized in the presence of Fe3O4 nanoparticles via dispersion polymerization. After polymerization, the magnetic polymer microbeads were modified with ethylenediamine (EDA). The obtained ethylenediamine-functionalized magnetic microspheres (EDA-MPMs) were
[...] Read more.
Magnetic polymer microspheres (MPMs) using glycidylmethacrylate (GMA) as a functional monomer were synthesized in the presence of Fe3O4 nanoparticles via dispersion polymerization. After polymerization, the magnetic polymer microbeads were modified with ethylenediamine (EDA). The obtained ethylenediamine-functionalized magnetic microspheres (EDA-MPMs) were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), vibrating-sample magnetometer (VSM) and Fourier transform infrared (FT-IR) spectroscopy. Then the EDA-MPMs were applied as adsorbents for the removal of Cr(VI) from aqueous solution. Langmuir equation was appropriate to describe the experimental data. The maximum adsorption capacities obtained from the Langmuir model were 236.9, 242.1 and 253.2 mg/g at 298, 308 and 318 K, respectively. The Cr(VI) adsorption equilibrium was established within 120 min and the adsorption kinetics was compatibly described by the pseudo-second order equation. The thermodynamic parameters (ΔG°, ΔH°, ΔS°) of the sorption process revealed that the adsorption was spontaneous and was an endothermic process. The regeneration study demonstrated that the EDA-MPMs could be repeatedly utilized with no significant loss of adsorption efficiency. Full article
(This article belongs to the Section Advanced Composites)
Figures

Open AccessArticle Ultrasound Elasticity Imaging System with Chirp-Coded Excitation for Assessing Biomechanical Properties of Elasticity Phantom
Materials 2015, 8(12), 8392-8413; doi:10.3390/ma8125458
Received: 31 August 2015 / Revised: 3 November 2015 / Accepted: 24 November 2015 / Published: 3 December 2015
PDF Full-text (13533 KB) | HTML Full-text | XML Full-text
Abstract
The biomechanical properties of soft tissues vary with pathological phenomenon. Ultrasound elasticity imaging is a noninvasive method used to analyze the local biomechanical properties of soft tissues in clinical diagnosis. However, the echo signal-to-noise ratio (eSNR) is diminished because of the attenuation of
[...] Read more.
The biomechanical properties of soft tissues vary with pathological phenomenon. Ultrasound elasticity imaging is a noninvasive method used to analyze the local biomechanical properties of soft tissues in clinical diagnosis. However, the echo signal-to-noise ratio (eSNR) is diminished because of the attenuation of ultrasonic energy by soft tissues. Therefore, to improve the quality of elastography, the eSNR and depth of ultrasound penetration must be increased using chirp-coded excitation. Moreover, the low axial resolution of ultrasound images generated by a chirp-coded pulse must be increased using an appropriate compression filter. The main aim of this study is to develop an ultrasound elasticity imaging system with chirp-coded excitation using a Tukey window for assessing the biomechanical properties of soft tissues. In this study, we propose an ultrasound elasticity imaging system equipped with a 7.5-MHz single-element transducer and polymethylpentene compression plate to measure strains in soft tissues. Soft tissue strains were analyzed using cross correlation (CC) and absolution difference (AD) algorithms. The optimal parameters of CC and AD algorithms used for the ultrasound elasticity imaging system with chirp-coded excitation were determined by measuring the elastographic signal-to-noise ratio (SNRe) of a homogeneous phantom. Moreover, chirp-coded excitation and short pulse excitation were used to measure the elasticity properties of the phantom. The elastographic qualities of the tissue-mimicking phantom were assessed in terms of Young’s modulus and elastographic contrast-to-noise ratio (CNRe). The results show that the developed ultrasound elasticity imaging system with chirp-coded excitation modulated by a Tukey window can acquire accurate, high-quality elastography images. Full article
(This article belongs to the Special Issue Selected Papers from ICBEI2015)
Open AccessArticle On the Passivity of Hysteretic Systems with Double Hysteretic Loops
Materials 2015, 8(12), 8414-8422; doi:10.3390/ma8125465
Received: 5 October 2015 / Revised: 19 November 2015 / Accepted: 20 November 2015 / Published: 3 December 2015
PDF Full-text (831 KB) | HTML Full-text | XML Full-text
Abstract
The Bouc–Wen hysteresis model is widely employed to mathematically represent the dynamical behavior of several physical devices, materials and systems such as magnetorheological dampers, lanthanide zirconium or aluminum oxides, mechanical structures or biomedical systems. However, these mathematical models must account for different properties
[...] Read more.
The Bouc–Wen hysteresis model is widely employed to mathematically represent the dynamical behavior of several physical devices, materials and systems such as magnetorheological dampers, lanthanide zirconium or aluminum oxides, mechanical structures or biomedical systems. However, these mathematical models must account for different properties such as the bounded-input bounded-output stability, asymptotic motion, thermodynamic admissibility or passivity in order to be physically consistent with the systems they represent. The passivity of a system is related to energy dissipation. More precisely, a system is passive if it does not generate energy but only dissipates it. The objective of this paper is to prove that two different double-loop Bouc–Wen models are passive under a particular set of model parameters. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Figures

Open AccessArticle An Evaluation of Global and Local Tensile Properties of Friction-Stir Welded DP980 Dual-Phase Steel Joints Using a Digital Image Correlation Method
Materials 2015, 8(12), 8424-8436; doi:10.3390/ma8125467
Received: 25 August 2015 / Revised: 18 November 2015 / Accepted: 25 November 2015 / Published: 4 December 2015
Cited by 4 | PDF Full-text (4806 KB) | HTML Full-text | XML Full-text
Abstract
The effect of the microstructure heterogeneity on the tensile plastic deformation characteristic of friction-stir-welded (FSW) dual-phase (DP) steel was investigated for the potential applications on the lightweight design of vehicles. Friction-stir-welded specimens with a butt joint configuration were prepared, and quasi-static tensile tests
[...] Read more.
The effect of the microstructure heterogeneity on the tensile plastic deformation characteristic of friction-stir-welded (FSW) dual-phase (DP) steel was investigated for the potential applications on the lightweight design of vehicles. Friction-stir-welded specimens with a butt joint configuration were prepared, and quasi-static tensile tests were conducted, to evaluate the tensile properties of DP980 dual-phase steels. The friction-stir welding led to the formation of martensite and a significant hardness rise in the stir zone (SZ), but the presence of a soft zone in the heat-affected zone (HAZ) was caused by tempering of the pre-existing martensite. Owing to the appearance of severe soft zone, DP980 FSW joint showed almost 93% joint efficiency with the view-point of ultimate tensile strength and relatively low ductility than the base metal (BM). The local tensile deformation characteristic of the FSW joints was also examined using the digital image correlation (DIC) methodology by mapping the global and local strain distribution, and was subsequently analyzed by mechanics calculation. It is found that the tensile deformation of the FSW joints is highly heterogeneous, leading to a significant decrease in global ductility. The HAZ of the joints is the weakest region where the strain localizes early, and this localization extends until fracture with a strain near 30%, while the strain in the SZ and BM is only 1% and 4%, respectively. Local constitutive properties in different heterogeneous regions through the friction-stir-welded joint was also briefly evaluated by assuming iso-stress conditions. The local stress-strain curves of individual weld zones provide a clear indication of the heterogeneity of the local mechanical properties. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Prediction Surface Morphology of Nanostructure Fabricated by Nano-Oxidation Technology
Materials 2015, 8(12), 8437-8451; doi:10.3390/ma8125468
Received: 9 September 2015 / Revised: 30 November 2015 / Accepted: 30 November 2015 / Published: 4 December 2015
PDF Full-text (4651 KB) | HTML Full-text | XML Full-text
Abstract
Atomic force microscopy (AFM) was used for visualization of a nano-oxidation technique performed on diamond-like carbon (DLC) thin film. Experiments of the nano-oxidation technique of the DLC thin film include those on nano-oxidation points and nano-oxidation lines. The feature sizes of the DLC
[...] Read more.
Atomic force microscopy (AFM) was used for visualization of a nano-oxidation technique performed on diamond-like carbon (DLC) thin film. Experiments of the nano-oxidation technique of the DLC thin film include those on nano-oxidation points and nano-oxidation lines. The feature sizes of the DLC thin film, including surface morphology, depth, and width, were explored after application of a nano-oxidation technique to the DLC thin film under different process parameters. A databank for process parameters and feature sizes of thin films was then established, and multiple regression analysis (MRA) and a back-propagation neural network (BPN) were used to carry out the algorithm. The algorithmic results are compared with the feature sizes acquired from experiments, thus obtaining a prediction model of the nano-oxidation technique of the DLC thin film. The comparative results show that the prediction accuracy of BPN is superior to that of MRA. When the BPN algorithm is used to predict nano-point machining, the mean absolute percentage errors (MAPE) of depth, left side, and right side are 8.02%, 9.68%, and 7.34%, respectively. When nano-line machining is being predicted, the MAPEs of depth, left side, and right side are 4.96%, 8.09%, and 6.77%, respectively. The obtained data can also be used to predict cross-sectional morphology in the DLC thin film treated with a nano-oxidation process. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Progress in Mirror-Based Fusion Neutron Source Development
Materials 2015, 8(12), 8452-8459; doi:10.3390/ma8125471
Received: 30 October 2015 / Revised: 22 November 2015 / Accepted: 27 November 2015 / Published: 4 December 2015
Cited by 15 | PDF Full-text (969 KB) | HTML Full-text | XML Full-text
Abstract
The Budker Institute of Nuclear Physics in worldwide collaboration has developed a project of a 14 MeV neutron source for fusion material studies and other applications. The projected neutron source of the plasma type is based on the gas dynamic trap (GDT), which
[...] Read more.
The Budker Institute of Nuclear Physics in worldwide collaboration has developed a project of a 14 MeV neutron source for fusion material studies and other applications. The projected neutron source of the plasma type is based on the gas dynamic trap (GDT), which is a special magnetic mirror system for plasma confinement. Essential progress in plasma parameters has been achieved in recent experiments at the GDT facility in the Budker Institute, which is a hydrogen (deuterium) prototype of the source. Stable confinement of hot-ion plasmas with the relative pressure exceeding 0.5 was demonstrated. The electron temperature was increased up to 0.9 keV in the regime with additional electron cyclotron resonance heating (ECRH) of a moderate power. These parameters are the record for axisymmetric open mirror traps. These achievements elevate the projects of a GDT-based neutron source on a higher level of competitive ability and make it possible to construct a source with parameters suitable for materials testing today. The paper presents the progress in experimental studies and numerical simulations of the mirror-based fusion neutron source and its possible applications including a fusion material test facility and a fusion-fission hybrid system. Full article
(This article belongs to the Special Issue Nuclear Materials 2015)
Open AccessArticle Raman Spectra of Luminescent Graphene Oxide (GO)-Phosphor Hybrid Nanoscrolls
Materials 2015, 8(12), 8460-8466; doi:10.3390/ma8125470
Received: 20 October 2015 / Revised: 27 November 2015 / Accepted: 30 November 2015 / Published: 4 December 2015
Cited by 1 | PDF Full-text (2773 KB) | HTML Full-text | XML Full-text
Abstract
Graphene oxide (GO)-phosphor hybrid nanoscrolls were synthesized using a simple chemical method. The GO-phosphor ratio was varied to find the optimum ratio for enhanced optical characteristics of the hybrid. A scanning electron microscope analysis revealed that synthesized GO scrolls achieved a length of
[...] Read more.
Graphene oxide (GO)-phosphor hybrid nanoscrolls were synthesized using a simple chemical method. The GO-phosphor ratio was varied to find the optimum ratio for enhanced optical characteristics of the hybrid. A scanning electron microscope analysis revealed that synthesized GO scrolls achieved a length of over 20 μm with interior cavities. The GO-phosphor hybrid is extensively analyzed using Raman spectroscopy, suggesting that various Raman combination modes are activated with the appearance of a low-frequency radial breathing-like mode (RBLM) of the type observed in carbon nanotubes. All of the synthesized GO-phosphor hybrids exhibit an intense luminescent emission around 540 nm along with a broad emission at approximately 400 nm, with the intensity ratio varying with the GO-phosphor ratio. The photoluminescence emissions were gauged using Commission Internationale d'Eclairage (CIE) coordinates and at an optimum ratio. The coordinates shift to the white region of the color spectra. Our study suggests that the GO-phosphor hybrid nanoscrolls are suitable candidates for light-emitting applications. Full article
(This article belongs to the Special Issue Graphene)
Open AccessArticle Polyols from Microwave Liquefied Bagasse and Its Application to Rigid Polyurethane Foam
Materials 2015, 8(12), 8496-8509; doi:10.3390/ma8125472
Received: 13 October 2015 / Revised: 28 November 2015 / Accepted: 1 December 2015 / Published: 8 December 2015
Cited by 4 | PDF Full-text (1527 KB) | HTML Full-text | XML Full-text
Abstract
Bagasse flour (BF) was liquefied using bi-component polyhydric alcohol (PA) as a solvent and phosphoric acid as a catalyst in a microwave reactor. The effect of BF to solvent ratio and reaction temperatures on the liquefaction extent and characteristics of liquefied products were
[...] Read more.
Bagasse flour (BF) was liquefied using bi-component polyhydric alcohol (PA) as a solvent and phosphoric acid as a catalyst in a microwave reactor. The effect of BF to solvent ratio and reaction temperatures on the liquefaction extent and characteristics of liquefied products were evaluated. The results revealed that almost 75% of the raw bagasse was converted into liquid products within 9 min at 150 °C with a BF to solvent ratio of 1/4. The hydroxyl and acid values of the liquefied bagasse (LB) varied with the liquefied conditions. High reaction temperature combining with low BF to solvent ratio resulted in a low hydroxyl number for the LB. The molecular weight and polydispersity of the LB from reactions of 150 °C was lower compared to that from 125 °C. Rigid polyurethane (PU) foams were prepared from LB and methylene diphenyl diisocyanate (MDI), and the structural, mechanical and thermal properties of the PU foam were evaluated. The PU foams prepared using the LB from high reaction temperature showed better physical and mechanical performance in comparison to those from low reaction temperature. The amount of PA in the LB has the ability of increasing thermal stability of LB-PU foams. The results in this study may provide fundamental information on integrated utilizations of sugarcane bagasse via microwave liquefaction process. Full article
(This article belongs to the Special Issue Advances in Renewable Energy Conversion Materials)
Open AccessArticle Effect of Hybrid Talc-Basalt Fillers in the Shell Layer on Thermal and Mechanical Performance of Co-Extruded Wood Plastic Composites
Materials 2015, 8(12), 8510-8523; doi:10.3390/ma8125473
Received: 2 October 2015 / Revised: 29 November 2015 / Accepted: 1 December 2015 / Published: 8 December 2015
PDF Full-text (3187 KB) | HTML Full-text | XML Full-text
Abstract
Hybrid basalt fiber (BF) and Talc filled high density polyethylene (HDPE) and co-extruded wood-plastic composites (WPCs) with different BF/Talc/HDPE composition levels in the shell were prepared and their mechanical, morphological and thermal properties were characterized. Incorporating BFs into the HDPE-Talc composite substantially enhanced
[...] Read more.
Hybrid basalt fiber (BF) and Talc filled high density polyethylene (HDPE) and co-extruded wood-plastic composites (WPCs) with different BF/Talc/HDPE composition levels in the shell were prepared and their mechanical, morphological and thermal properties were characterized. Incorporating BFs into the HDPE-Talc composite substantially enhanced the thermal expansion property, flexural, tensile and dynamic modulus without causing a significant decrease in the tensile and impact strength of the composites. Strain energy estimation suggested positive and better interfacial interactions of HDPE with BFs than that with talc. The co-extruded structure design improved the mechanical properties of WPC due to the protective shell layer. The composite flexural and impact strength properties increased, and the thermal expansion decreased as BF content increased in the hybrid BF/Talc filled shells. The cone calorimetry data demonstrated that flame resistance of co-extruded WPCs was improved with the use of combined fillers in the shell layer, especially with increased loading of BFs. The combined shell filler system with BFs and Talc could offer a balance between cost and performance for co-extruded WPCs. Full article
(This article belongs to the Special Issue Bio- and Natural-Fiber Composites)
Figures

Open AccessArticle Process Design of Aluminum Tailor Heat Treated Blanks
Materials 2015, 8(12), 8524-8538; doi:10.3390/ma8125476
Received: 31 October 2015 / Revised: 27 November 2015 / Accepted: 1 December 2015 / Published: 9 December 2015
Cited by 1 | PDF Full-text (5276 KB) | HTML Full-text | XML Full-text
Abstract
In many industrials field, especially in the automotive sector, there is a trend toward lightweight constructions in order to reduce the weight and thereby the CO2 and NOx emissions of the products. An auspicious approach within this context is the substitution
[...] Read more.
In many industrials field, especially in the automotive sector, there is a trend toward lightweight constructions in order to reduce the weight and thereby the CO2 and NOx emissions of the products. An auspicious approach within this context is the substitution of conventional deep drawing steel by precipitation hardenable aluminum alloys. However, based on the low formability, the application for complex stamping parts is challenging. Therefore, at the Institute of Manufacturing Technology, an innovative technology to enhance the forming limit of these lightweight materials was invented. The key idea of the so-called Tailor Heat Treated Blanks (THTB) is optimization of the mechanical properties by local heat treatment before the forming operation. An accurate description of material properties is crucial to predict the forming behavior of tailor heat treated blanks by simulation. Therefore, within in this research project, a holistic approach for the design of the THTB process in dependency of the main influencing parameters is presented and discussed in detail. The capability of the approach for the process development of complex forming operations is demonstrated by a comparison of local blank thickness of a tailgate with the corresponding results from simulation. Full article
(This article belongs to the Special Issue Forming of Light Weight Materials)
Open AccessArticle Damage Evolution and Life Prediction of Cross-Ply C/SiC Ceramic-Matrix Composite under Cyclic Fatigue Loading at Room Temperature and 800 °C in Air
Materials 2015, 8(12), 8539-8560; doi:10.3390/ma8125474
Received: 25 September 2015 / Revised: 21 November 2015 / Accepted: 3 December 2015 / Published: 9 December 2015
Cited by 2 | PDF Full-text (19009 KB) | HTML Full-text | XML Full-text
Abstract
The damage evolution and life prediction of cross-ply C/SiC ceramic-matrix composite (CMC) under cyclic-fatigue loading at room temperature and 800 °C in air have been investigated using damage parameters derived from fatigue hysteresis loops, i.e., fatigue hysteresis modulus and fatigue hysteresis loss
[...] Read more.
The damage evolution and life prediction of cross-ply C/SiC ceramic-matrix composite (CMC) under cyclic-fatigue loading at room temperature and 800 °C in air have been investigated using damage parameters derived from fatigue hysteresis loops, i.e., fatigue hysteresis modulus and fatigue hysteresis loss energy. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy degrade with increasing applied cycles attributed to transverse cracks in the 90° plies, matrix cracks and fiber/matrix interface debonding in the 0° plies, interface wear at room temperature, and interface and carbon fibers oxidation at 800 °C in air. The relationships between fatigue hysteresis loops, fatigue hysteresis modulus and fatigue hysteresis loss energy have been established. Comparing experimental fatigue hysteresis loss energy with theoretical computational values, the fiber/matrix interface shear stress corresponding to different cycle numbers has been estimated. It was found that the degradation rate at 800 °C in air is much faster than that at room temperature due to serious oxidation in the pyrolytic carbon (PyC) interphase and carbon fibers. Combining the fiber fracture model with the interface shear stress degradation model and the fibers strength degradation model, the fraction of broken fibers versus the cycle number can be determined for different fatigue peak stresses. The fatigue life S-N curves of cross-ply C/SiC composite at room temperature and 800 °C in air have been predicted. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle The Corrosion Characteristics and Tensile Behavior of Reinforcement under Coupled Carbonation and Static Loading
Materials 2015, 8(12), 8561-8577; doi:10.3390/ma8125479
Received: 16 September 2015 / Revised: 20 November 2015 / Accepted: 3 December 2015 / Published: 9 December 2015
Cited by 2 | PDF Full-text (7850 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the non-uniform corrosion characteristics and mechanical properties of reinforcement under coupled action of carbonation and static loading. The two parameters, namely area-box (AB) value and arithmetical mean deviation (Ra), are adopted to characterize the corrosion morphology and
[...] Read more.
This paper describes the non-uniform corrosion characteristics and mechanical properties of reinforcement under coupled action of carbonation and static loading. The two parameters, namely area-box (AB) value and arithmetical mean deviation (Ra), are adopted to characterize the corrosion morphology and pitting distribution from experimental observations. The results show that the static loading affects the corrosion characteristics of reinforcement. Local stress concentration in corroded reinforcement caused by tensile stress drives the corrosion pit pattern to be more irregular. The orthogonal test results from finite element simulations show that pit shape and pit depth are the two significant factors affecting the tensile behavior of reinforcement. Under the condition of similar corrosion mass loss ratio, the maximum plastic strain of corroded reinforcement increases with the increase of Ra and load time-history significantly. Full article
Open AccessArticle Piezoelectric, Mechanical and Acoustic Properties of KNaNbOF5 from First-Principles Calculations
Materials 2015, 8(12), 8578-8589; doi:10.3390/ma8125477
Received: 24 September 2015 / Revised: 13 October 2015 / Accepted: 12 November 2015 / Published: 9 December 2015
Cited by 3 | PDF Full-text (1837 KB) | HTML Full-text | XML Full-text
Abstract
Recently, a noncentrosymmetric crystal, KNaNbOF5, has attracted attention due to its potential to present piezoelectric properties. Although α- and β-KNaNbOF5 are similar in their stoichiometries, their structural frameworks, and their synthetic routes, the two phases exhibit very different properties. This
[...] Read more.
Recently, a noncentrosymmetric crystal, KNaNbOF5, has attracted attention due to its potential to present piezoelectric properties. Although α- and β-KNaNbOF5 are similar in their stoichiometries, their structural frameworks, and their synthetic routes, the two phases exhibit very different properties. This paper presents, from first-principles calculations, comparative studies of the structural, electronic, piezoelectric, and elastic properties of the α and the β phase of the material. Based on the Christoffel equation, the slowness surface of the acoustic waves is obtained to describe its acoustic prosperities. These results may benefit further applications of KNaNbOF5. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
Figures

Open AccessArticle Effects of Medium Temperature and Industrial By-Products on the Key Hardened Properties of High Performance Concrete
Materials 2015, 8(12), 8608-8623; doi:10.3390/ma8125464
Received: 10 October 2015 / Revised: 10 November 2015 / Accepted: 25 November 2015 / Published: 10 December 2015
Cited by 2 | PDF Full-text (1815 KB) | HTML Full-text | XML Full-text
Abstract
The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial
[...] Read more.
The aim of the work reported in this article was to investigate the effects of medium temperature and industrial by-products on the key hardened properties of high performance concrete. Four concrete mixes were prepared based on a water-to-binder ratio of 0.35. Two industrial by-products, silica fume and Class F fly ash, were used separately and together with normal portland cement to produce three concrete mixes in addition to the control mix. The properties of both fresh and hardened concretes were examined in the laboratory. The freshly mixed concrete mixes were tested for slump, slump flow, and V-funnel flow. The hardened concretes were tested for compressive strength and dynamic modulus of elasticity after exposing to 20, 35 and 50 °C. In addition, the initial surface absorption and the rate of moisture movement into the concretes were determined at 20 °C. The performance of the concretes in the fresh state was excellent due to their superior deformability and good segregation resistance. In their hardened state, the highest levels of compressive strength and dynamic modulus of elasticity were produced by silica fume concrete. In addition, silica fume concrete showed the lowest level of initial surface absorption and the lowest rate of moisture movement into the interior of concrete. In comparison, the compressive strength, dynamic modulus of elasticity, initial surface absorption, and moisture movement rate of silica fume-fly ash concrete were close to those of silica fume concrete. Moreover, all concretes provided relatively low compressive strength and dynamic modulus of elasticity when they were exposed to 50 °C. However, the effect of increased temperature was less detrimental for silica fume and silica fume-fly ash concretes in comparison with the control concrete. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
Open AccessCommunication Drastic Dependence of the pH Sensitivity of Fe2O3-Bi2O3-B2O3 Hydrophobic Glasses with Composition
Materials 2015, 8(12), 8624-8629; doi:10.3390/ma8125480
Received: 24 November 2015 / Revised: 7 December 2015 / Accepted: 7 December 2015 / Published: 10 December 2015
Cited by 1 | PDF Full-text (918 KB) | HTML Full-text | XML Full-text
Abstract
Fe2O3-Bi2O3-B2O3 (FeBiB) glasses were developed as novel pH responsive hydrophobic glasses. The influence of the glass composition on the pH sensitivity of FeBiB glasses was investigated. The pH sensitivity drastically decreased with
[...] Read more.
Fe2O3-Bi2O3-B2O3 (FeBiB) glasses were developed as novel pH responsive hydrophobic glasses. The influence of the glass composition on the pH sensitivity of FeBiB glasses was investigated. The pH sensitivity drastically decreased with decreasing B2O3 content. A moderate amount of Fe2O3 and a small amount of B2O3 respectively produces bulk electronic conduction and a pH response on glass surfaces. Because the remaining components of the glass can be selected freely, this discovery could prove very useful in developing novel pH glass electrodes that are self-cleaning and resist fouling. Full article
(This article belongs to the Special Issue Self-Cleaning and Antimicrobial Surfaces)
Figures

Open AccessArticle Synthesis and Characterization of Biopolymeric Chitosan Derived from Land Snail Shells and Its Potential for Pb2+ Removal from Aqueous Solution
Materials 2015, 8(12), 8630-8640; doi:10.3390/ma8125482
Received: 15 November 2015 / Revised: 2 December 2015 / Accepted: 3 December 2015 / Published: 10 December 2015
Cited by 4 | PDF Full-text (3120 KB) | HTML Full-text | XML Full-text
Abstract
Pb2+ is considered to be a very toxic pollutant in the aquatic environmental media. Biopolymeric chitosan synthesized from snail shell has been studied for its potential to remove heavy metals from aqueous solution. The experiments were conducted in the range of 1–50
[...] Read more.
Pb2+ is considered to be a very toxic pollutant in the aquatic environmental media. Biopolymeric chitosan synthesized from snail shell has been studied for its potential to remove heavy metals from aqueous solution. The experiments were conducted in the range of 1–50 mg/L initial Pb2+ concentration at 298 K. The effects of pH, adsorbent dosage and contact time on the adsorptive property of the adsorbent were investigated and optimized. The derived chitosan was characterized using Fourier transform infrared spectrometer (FT-IR) and X-ray florescence (XRF). The experimental data obtained were analysed using the Langmuir and Freundlich adsorption isotherm models. The Langmuir model and pseudo second order kinetic model suitably described the adsorption and kinetics of the process with regression coefficient of 0.99 and 1.00, respectively. Sodium hydroxide was a better desorbing agent than hydrochloric acid and de-ionized water. From the results obtained, it is concluded that synthesized biopolymers from land snail shells has the potential for the removal of Pb2+ from aqueous solutions. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle High-Temperature Storage Testing of ACF Attached Sensor Structures
Materials 2015, 8(12), 8641-8660; doi:10.3390/ma8125455
Received: 22 October 2015 / Accepted: 24 November 2015 / Published: 10 December 2015
Cited by 2 | PDF Full-text (18761 KB) | HTML Full-text | XML Full-text
Abstract
Several electronic applications must withstand elevated temperatures during their lifetime. Materials and packages for use in high temperatures have been designed, but they are often very expensive, have limited compatibility with materials, structures, and processing techniques, and are less readily available than traditional
[...] Read more.
Several electronic applications must withstand elevated temperatures during their lifetime. Materials and packages for use in high temperatures have been designed, but they are often very expensive, have limited compatibility with materials, structures, and processing techniques, and are less readily available than traditional materials. Thus, there is an increasing interest in using low-cost polymer materials in high temperature applications. This paper studies the performance and reliability of sensor structures attached with anisotropically conductive adhesive film (ACF) on two different organic printed circuit board (PCB) materials: FR-4 and Rogers. The test samples were aged at 200 °C and 240 °C and monitored electrically during the test. Material characterization techniques were also used to analyze the behavior of the materials. Rogers PCB was observed to be more stable at high temperatures in spite of degradation observed, especially during the first 120 h of aging. The electrical reliability was very good with Rogers. At 200 °C, the failures occurred after 2000 h of testing, and even at 240 °C the interconnections were functional for 400 h. The study indicates that, even though these ACFs were not designed for use in high temperatures, with stable PCB material they are promising interconnection materials at elevated temperatures, especially at 200 °C. However, the fragility of the structure due to material degradation may cause reliability problems in long-term high temperature exposure. Full article
Open AccessArticle A Photolithographic Approach to Polymeric Microneedles Array Fabrication
Materials 2015, 8(12), 8661-8673; doi:10.3390/ma8125484
Received: 2 October 2015 / Revised: 2 December 2015 / Accepted: 3 December 2015 / Published: 11 December 2015
Cited by 7 | PDF Full-text (6037 KB) | HTML Full-text | XML Full-text
Abstract
In this work, two procedures for fabrication of polymeric microneedles based on direct photolithography, without any etching or molding process, are reported. Polyethylene glycol (average molecular weight 250 Da), casted into a silicone vessel and exposed to ultraviolet light (365 nm) through a
[...] Read more.
In this work, two procedures for fabrication of polymeric microneedles based on direct photolithography, without any etching or molding process, are reported. Polyethylene glycol (average molecular weight 250 Da), casted into a silicone vessel and exposed to ultraviolet light (365 nm) through a mask, cross-links when added by a commercial photocatalyzer. By changing the position of the microneedles support with respect to the vessel, different shapes and lengths can be achieved. Microneedles from a hundred microns up to two millimeters have been obtained just tuning the radiation dose, by changing the exposure time (5–15 s) and/or the power density (9–18 mW/cm2) during photolithography. Different microneedle shapes, such as cylindrical, conic or lancet-like, for specific applications such as micro-indentation or drug delivery, are demonstrated. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Open AccessArticle Properties of Cadmium-(bis)dodecylthiolate and Polymeric Composites Based on It
Materials 2015, 8(12), 8691-8700; doi:10.3390/ma8125487
Received: 20 October 2015 / Revised: 23 November 2015 / Accepted: 4 December 2015 / Published: 11 December 2015
Cited by 1 | PDF Full-text (1979 KB) | HTML Full-text | XML Full-text
Abstract
We study the thermo-physical and photoluminescence (PL) properties of cadmium-(bis)dodecylthiolate (Cd(C12H25S)2). Significant attention is drawn to characterization of Cd(C12H25S)2 by different methods. The laser-induced PLs of Cd(C12H25
[...] Read more.
We study the thermo-physical and photoluminescence (PL) properties of cadmium-(bis)dodecylthiolate (Cd(C12H25S)2). Significant attention is drawn to characterization of Cd(C12H25S)2 by different methods. The laser-induced PLs of Cd(C12H25S)2 and Cd(C12H25S)2/(polymethyl methacrylate) (PMMA) composites are studied. Samples of Cd(C12H25S)2/PMMA are synthesized by the polymerization method. Ultraviolet (UV)-pulsed laser irradiation of the samples under relatively small fluences leads to the formation of induced PL with the maximum near the wavelength of 600 nm. This process can be attributed to the transformation of Cd(C12H25S)2 within the precursor grains. Another PL peak at 450–500 nm, which appears under the higher fluences, relies on the formation of CdS complexes with a significant impact of the polymer matrix. Full article
(This article belongs to the Section Advanced Composites)
Figures

Open AccessArticle Acid Denaturation Inducing Self-Assembly of Curcumin-Loaded Hemoglobin Nanoparticles
Materials 2015, 8(12), 8701-8713; doi:10.3390/ma8125486
Received: 10 October 2015 / Revised: 23 November 2015 / Accepted: 4 December 2015 / Published: 11 December 2015
Cited by 3 | PDF Full-text (2655 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hemoglobin is a promising drug carrier but lacks extensive investigation. The chemical conjugation of hemoglobin and drugs is costly and complex, so we have developed curcumin-loaded hemoglobin nanoparticles (CCM-Hb-NPs) via self-assembly for the first time. Using the acid-denaturing method, we avoid introducing denaturants
[...] Read more.
Hemoglobin is a promising drug carrier but lacks extensive investigation. The chemical conjugation of hemoglobin and drugs is costly and complex, so we have developed curcumin-loaded hemoglobin nanoparticles (CCM-Hb-NPs) via self-assembly for the first time. Using the acid-denaturing method, we avoid introducing denaturants and organic solvents. The nanoparticles are stable with uniform size. We have conducted a series of experiments to examine the interaction of hemoglobin and CCM, including hydrophobic characterization, SDS-PAGE. These experiments substantiate that this self-assembly process is mainly driven by hydrophobic forces. Our nanoparticles achieve much higher cell uptake efficiency and cytotoxicity than free CCM solution in vitro. The uptake inhibition experiments also demonstrate that our nanoparticles were incorporated via the classic clathrin-mediated endocytosis pathway. These results indicate that hemoglobin nanoparticles formed by self-assembly are a promising drug delivery system for cancer therapy. Full article
Open AccessArticle Prediction of the Chloride Resistance of Concrete Modified with High Calcium Fly Ash Using Machine Learning
Materials 2015, 8(12), 8714-8727; doi:10.3390/ma8125483
Received: 9 October 2015 / Revised: 16 November 2015 / Accepted: 30 November 2015 / Published: 11 December 2015
Cited by 1 | PDF Full-text (519 KB) | HTML Full-text | XML Full-text
Abstract
The aim of the study was to generate rules for the prediction of the chloride resistance of concrete modified with high calcium fly ash using machine learning methods. The rapid chloride permeability test, according to the Nordtest Method Build 492, was used for
[...] Read more.
The aim of the study was to generate rules for the prediction of the chloride resistance of concrete modified with high calcium fly ash using machine learning methods. The rapid chloride permeability test, according to the Nordtest Method Build 492, was used for determining the chloride ions’ penetration in concrete containing high calcium fly ash (HCFA) for partial replacement of Portland cement. The results of the performed tests were used as the training set to generate rules describing the relation between material composition and the chloride resistance. Multiple methods for rule generation were applied and compared. The rules generated by algorithm J48 from the Weka workbench provided the means for adequate classification of plain concretes and concretes modified with high calcium fly ash as materials of good, acceptable or unacceptable resistance to chloride penetration. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
Figures

Open AccessArticle Experimental Characteristics of Dry Stack Masonry under Compression and Shear Loading
Materials 2015, 8(12), 8731-8744; doi:10.3390/ma8125489
Received: 11 October 2015 / Revised: 6 December 2015 / Accepted: 8 December 2015 / Published: 12 December 2015
Cited by 3 | PDF Full-text (5718 KB) | HTML Full-text | XML Full-text
Abstract
The behavior of dry stack masonry (DSM) is influenced by the interaction of the infill with the frame (especially the joints between bricks), which requires further research. This study investigates the compression and shear behaviors of DSM. First, a series of compression tests
[...] Read more.
The behavior of dry stack masonry (DSM) is influenced by the interaction of the infill with the frame (especially the joints between bricks), which requires further research. This study investigates the compression and shear behaviors of DSM. First, a series of compression tests were carried out on both masonry prism with mortar (MP_m) and DSM prism (MP_ds). The failure mode of each prism was determined. Different from the MP_m, the stress-strain relationship of the MP_ds was characterized by an upward concavity at the initial stage. The compression strength of the MP_ds was slightly reduced by 15%, while the elastic modulus was reduced by over 62%. In addition, 36 shear-compression tests were carried out under cyclic loads to emphasize the influence of various loads on the shear-compression behavior of DSM. The results showed that the Mohr-Coulomb friction law adequately represents the failure of dry joints at moderate stress levels, and the varying friction coefficients under different load amplitudes cannot be neglected. The experimental setup and results are valuable for further research. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessCommunication The ZrO2 Formation in ZrB2/SiC Composite Irradiated by Laser
Materials 2015, 8(12), 8745-8750; doi:10.3390/ma8125475
Received: 3 November 2015 / Revised: 30 November 2015 / Accepted: 3 December 2015 / Published: 14 December 2015
PDF Full-text (3685 KB) | HTML Full-text | XML Full-text
Abstract
In order to clearly understand the details of ZrO2 formation during ablation, high intensity continuous laser was chosen to irradiate ZrB2/SiC. The results reveal that there are two different modes of ZrO2 formation depending on whether liquid SiO2
[...] Read more.
In order to clearly understand the details of ZrO2 formation during ablation, high intensity continuous laser was chosen to irradiate ZrB2/SiC. The results reveal that there are two different modes of ZrO2 formation depending on whether liquid SiO2 is present. When liquid SiO2 is present, ZrO2 generated by the oxidation of ZrB2 is firstly dissolved into SiO2. Then, ZrO2 will precipitate again, the temperature will decrease and the SiO2 will evaporate. Otherwise, the ZrB2 will be oxidized to ZrO2 directly. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle Failure Progress of 3D Reinforced GFRP Laminate during Static Bending, Evaluated by Means of Acoustic Emission and Vibrations Analysis
Materials 2015, 8(12), 8751-8767; doi:10.3390/ma8125490
Received: 9 October 2015 / Revised: 29 November 2015 / Accepted: 3 December 2015 / Published: 14 December 2015
PDF Full-text (5849 KB) | HTML Full-text | XML Full-text
Abstract
The work aimed to assess the failure progress in a glass fiber-reinforced polymer laminate with a 3D-woven and (as a comparison) plain-woven reinforcement, during static bending, using acoustic emission signals. The innovative method of the separation of the signal coming from the fiber
[...] Read more.
The work aimed to assess the failure progress in a glass fiber-reinforced polymer laminate with a 3D-woven and (as a comparison) plain-woven reinforcement, during static bending, using acoustic emission signals. The innovative method of the separation of the signal coming from the fiber fracture and the one coming from the matrix fracture with the use of the acoustic event’s energy as a criterion was applied. The failure progress during static bending was alternatively analyzed by evaluation of the vibration signal. It gave a possibility to validate the results of the acoustic emission. Acoustic emission, as well as vibration signal analysis proved to be good and effective tools for the registration of failure effects in composite laminates. Vibration analysis is more complicated methodologically, yet it is more precise. The failure progress of the 3D laminate is “safer” and more beneficial than that of the plain-woven laminate. It exhibits less rapid load capacity drops and a higher fiber effort contribution at the moment of the main laminate failure. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
Open AccessArticle Effect of Different Manufacturing Methods on the Conflict between Porosity and Mechanical Properties of Spiral and Porous Polyethylene Terephthalate/Sodium Alginate Bone Scaffolds
Materials 2015, 8(12), 8768-8779; doi:10.3390/ma8125488
Received: 16 September 2015 / Revised: 3 December 2015 / Accepted: 7 December 2015 / Published: 14 December 2015
Cited by 3 | PDF Full-text (7194 KB) | HTML Full-text | XML Full-text
Abstract
In order to solve the incompatibility between high porosity and mechanical properties, this study fabricates bone scaffolds by combining braids and sodium alginate (SA) membranes. Polyethylene terephthalate (PET) plied yarns are braided into hollow, porous three dimensional (3D) PET braids, which are then
[...] Read more.
In order to solve the incompatibility between high porosity and mechanical properties, this study fabricates bone scaffolds by combining braids and sodium alginate (SA) membranes. Polyethylene terephthalate (PET) plied yarns are braided into hollow, porous three dimensional (3D) PET braids, which are then immersed in SA solution, followed by cross-linking with calcium chloride (CaCl2) and drying, to form PET bone scaffolds. Next, SA membranes are rolled and then inserted into the braids to form the spiral and porous PET/SA bone scaffolds. Samples are finally evaluated for surface observation, porosity, water contact angle, compressive strength, and MTT assay. The test results show that the PET bone scaffolds and PET/SA bone scaffolds both have good hydrophilicity. An increasing number of layers and an increasing CaCl2 concentration cause the messy, loose surface structure to become neat and compact, which, in turn, decreases the porosity and increases the compressive strength. The MTT assay results show that the cell viability of differing SA membranes is beyond 100%, indicating that the PET/SA bone scaffolds containing SA membranes are biocompatible for cell attachment and proliferation. Full article
(This article belongs to the Special Issue Selected Papers from ICBEI2015)
Open AccessArticle Investigation on the Mechanical Properties of a Cement-Based Material Containing Carbon Nanotube under Drying and Freeze-Thaw Conditions
Materials 2015, 8(12), 8780-8792; doi:10.3390/ma8125491
Received: 8 October 2015 / Revised: 23 November 2015 / Accepted: 30 November 2015 / Published: 14 December 2015
Cited by 7 | PDF Full-text (2741 KB) | HTML Full-text | XML Full-text
Abstract
This paper aimed to explore the mechanical properties of a cement-based material with carbon nanotube (CNT) under drying and freeze-thaw environments. Mercury Intrusion Porosimetry and Scanning Electron Microscopy were used to analyze the pore structure and microstructure of CNT/cement composite, respectively. The experimental
[...] Read more.
This paper aimed to explore the mechanical properties of a cement-based material with carbon nanotube (CNT) under drying and freeze-thaw environments. Mercury Intrusion Porosimetry and Scanning Electron Microscopy were used to analyze the pore structure and microstructure of CNT/cement composite, respectively. The experimental results showed that multi-walled CNT (MWCNT) could improve to different degrees the mechanical properties (compressive and flexural strengths) and physical performances (shrinkage and water loss) of cement-based materials under drying and freeze-thaw conditions. This paper also demonstrated that MWCNT could interconnect hydration products to enhance the performance of anti-microcracks for cement-based materials, as well as the density of materials due to CNT’s filling action. Full article
Open AccessArticle Improvement of Bearing Capacity in Recycled Aggregates Suitable for Use as Unbound Road Sub-Base
Materials 2015, 8(12), 8804-8816; doi:10.3390/ma8125493
Received: 25 September 2015 / Revised: 2 December 2015 / Accepted: 4 December 2015 / Published: 16 December 2015
Cited by 1 | PDF Full-text (2436 KB) | HTML Full-text | XML Full-text
Abstract
Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates with lower densities, higher water absorption capacities, and lower mechanical strength than natural aggregates. In this paper, the mechanical behaviour and microstructural properties of natural aggregates, recycled concrete aggregates and
[...] Read more.
Recycled concrete aggregates and mixed recycled aggregates are specified as types of aggregates with lower densities, higher water absorption capacities, and lower mechanical strength than natural aggregates. In this paper, the mechanical behaviour and microstructural properties of natural aggregates, recycled concrete aggregates and mixed recycled aggregates were compared. Different specimens of unbound recycled mixtures demonstrated increased resistance properties. The formation of new cement hydrated particles was observed, and pozzolanic reactions were discovered by electronon microscopy in these novel materials. The properties of recycled concrete aggregates and mixed recycled aggregates suggest that these recycled materials can be used in unbound road layers to improve their mechanical behaviour in the long term. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
Open AccessArticle Utilization of Palm Oil Clinker as Cement Replacement Material
Materials 2015, 8(12), 8817-8838; doi:10.3390/ma8125494
Received: 28 July 2015 / Revised: 2 December 2015 / Accepted: 7 December 2015 / Published: 16 December 2015
Cited by 9 | PDF Full-text (6935 KB) | HTML Full-text | XML Full-text
Abstract
The utilization of waste materials from the palm oil industry provides immense benefit to various sectors of the construction industry. Palm oil clinker is a by-product from the processing stages of palm oil goods. Channelling this waste material into the building industry helps
[...] Read more.
The utilization of waste materials from the palm oil industry provides immense benefit to various sectors of the construction industry. Palm oil clinker is a by-product from the processing stages of palm oil goods. Channelling this waste material into the building industry helps to promote sustainability besides overcoming waste disposal problems. Environmental pollution due to inappropriate waste management system can also be drastically reduced. In this study, cement was substituted with palm oil clinker powder as a binder material in self-compacting mortar. The fresh, hardened and microstructure properties were evaluated throughout this study. In addition, sustainability component analysis was also carried out to assess the environmental impact of introducing palm oil clinker powder as a replacement material for cement. It can be inferred that approximately 3.3% of cement production can be saved by substituting palm oil clinker powder with cement. Reducing the utilization of cement through a high substitution level of this waste material will also help to reduce carbon emissions by 52%. A cleaner environment free from pollutants can be created to ensure healthier living. Certain industries may benefit through the inclusion of this waste material as the cost and energy consumption of the product can be minimized. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
Open AccessArticle A Novel Approach of Using Ground CNTs as the Carbon Source to Fabricate Uniformly Distributed Nano-Sized TiCx/2009Al Composites
Materials 2015, 8(12), 8839-8849; doi:10.3390/ma8125495
Received: 2 November 2015 / Revised: 7 December 2015 / Accepted: 9 December 2015 / Published: 17 December 2015
Cited by 9 | PDF Full-text (4057 KB) | HTML Full-text | XML Full-text
Abstract
Nano-sized TiCx/2009Al composites (with 5, 7, and 9 vol% TiCx) were fabricated via the combustion synthesis of the 2009Al-Ti-CNTs system combined with vacuum hot pressing followed by hot extrusion. In the present study, CNTs were used as the carbon
[...] Read more.
Nano-sized TiCx/2009Al composites (with 5, 7, and 9 vol% TiCx) were fabricated via the combustion synthesis of the 2009Al-Ti-CNTs system combined with vacuum hot pressing followed by hot extrusion. In the present study, CNTs were used as the carbon source to synthesize nano-sized TiCx particles. An attempt was made to correlate the effect of ground CNTs by milling and the distribution of synthesized nano-sized TiCx particles in 2009Al as well as the tensile properties of nano-sized TiCx/2009Al composites. Microstructure analysis showed that when ground CNTs were used, the synthesized nano-sized TiCx particles dispersed more uniformly in the 2009Al matrix. Moreover, when 2 h-milled CNTs were used, the 5, 7, and 9 vol% nano-sized TiCx/2009Al composites had the highest tensile properties, especially, the 9 vol% nano-sized TiCx/2009Al composites. The results offered a new approach to improve the distribution of in situ nano-sized TiCx particles and tensile properties of composites. Full article
Open AccessArticle Preparation and Compatibility Evaluation of Polypropylene/High Density Polyethylene Polyblends
Materials 2015, 8(12), 8850-8859; doi:10.3390/ma8125496
Received: 23 September 2015 / Revised: 8 December 2015 / Accepted: 11 December 2015 / Published: 17 December 2015
Cited by 9 | PDF Full-text (4123 KB) | HTML Full-text | XML Full-text
Abstract
This study proposes melt-blending polypropylene (PP) and high density polyethylene (HDPE) that have a similar melt flow index (MFI) to form PP/HDPE polyblends. The influence of the content of HDPE on the properties and compatibility of polyblends is examined by using a tensile
[...] Read more.
This study proposes melt-blending polypropylene (PP) and high density polyethylene (HDPE) that have a similar melt flow index (MFI) to form PP/HDPE polyblends. The influence of the content of HDPE on the properties and compatibility of polyblends is examined by using a tensile test, flexural test, Izod impact test, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), polarized light microscopy (PLM), and X-ray diffraction (XRD). The SEM results show that PP and HDPE are incompatible polymers with PP being a continuous phase and HDPE being a dispersed phase. The FTIR results show that the combination of HDPE does not influence the chemical structure of PP, indicating that the polyblends are made of a physical blending. The DSC and XRD results show that PP and HDPE are not compatible, and the combination of HDPE is not correlated with the crystalline structure and stability of PP. The PLM results show that the combination of HDPE causes stacking and incompatibility between HDPE and PP spherulites, and PP thus has incomplete spherulite morphology and a smaller spherulite size. However, according to mechanical property test results, the combination of HDPE improves the impact strength of PP. Full article
(This article belongs to the Special Issue Selected Papers from ICBEI2015)
Open AccessArticle Efficiency Enhancement of Dye-Sensitized Solar Cells’ Performance with ZnO Nanorods Grown by Low-Temperature Hydrothermal Reaction
Materials 2015, 8(12), 8860-8867; doi:10.3390/ma8125499
Received: 5 September 2015 / Revised: 9 December 2015 / Accepted: 10 December 2015 / Published: 19 December 2015
Cited by 8 | PDF Full-text (2377 KB) | HTML Full-text | XML Full-text
Abstract
In this study, aligned zinc oxide (ZnO) nanorods (NRs) with various lengths (1.5–5 µm) were deposited on ZnO:Al (AZO)-coated glass substrates by using a solution phase deposition method; these NRs were prepared for application as working electrodes to increase the photovoltaic conversion efficiency
[...] Read more.
In this study, aligned zinc oxide (ZnO) nanorods (NRs) with various lengths (1.5–5 µm) were deposited on ZnO:Al (AZO)-coated glass substrates by using a solution phase deposition method; these NRs were prepared for application as working electrodes to increase the photovoltaic conversion efficiency of solar cells. The results were observed in detail by using X-ray diffraction, field-emission scanning electron microscopy, UV-visible spectrophotometry, electrochemical impedance spectroscopy, incident photo-to-current conversion efficiency, and solar simulation. The results indicated that when the lengths of the ZnO NRs increased, the adsorption of D-719 dyes through the ZnO NRs increased along with enhancing the short-circuit photocurrent and open-circuit voltage of the cell. An optimal power conversion efficiency of 0.64% was obtained in a dye-sensitized solar cell (DSSC) containing the ZnO NR with a length of 5 µm. The objective of this study was to facilitate the development of a ZnO-based DSSC. Full article
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices) Printed Edition available
Open AccessArticle Surface Effects and Challenges for Application of Piezoelectric Langasite Substrates in Surface Acoustic Wave Devices Caused by High Temperature Annealing under High Vacuum
Materials 2015, 8(12), 8868-8876; doi:10.3390/ma8125497
Received: 14 October 2015 / Revised: 8 December 2015 / Accepted: 14 December 2015 / Published: 19 December 2015
Cited by 3 | PDF Full-text (16491 KB) | HTML Full-text | XML Full-text
Abstract
Substrate materials that are high-temperature stable are essential for sensor devices which are applied at high temperatures. Although langasite is suggested as such a material, severe O and Ga diffusion into an O-affine deposited film was observed during annealing at high temperatures under
[...] Read more.
Substrate materials that are high-temperature stable are essential for sensor devices which are applied at high temperatures. Although langasite is suggested as such a material, severe O and Ga diffusion into an O-affine deposited film was observed during annealing at high temperatures under vacuum conditions, leading to a damage of the metallization as well as a change of the properties of the substrate and finally to a failure of the device. Therefore, annealing of bare LGS (La 3 Ga 5 SiO 14 ) substrates at 800 ∘ C under high vacuum conditions is performed to analyze whether this pretreatment improves the suitability and stability of this material for high temperature applications in vacuum. To reveal the influence of the pretreatment on the subsequently deposited metallization, RuAl thin films are used as they are known to oxidize on LGS at high temperatures. A local study of the pretreated and metallized substrates using transmission electron microscopy reveals strong modification of the substrate surface. Micro cracks are visible. The composition of the substrate is strongly altered at those regions. Severe challenges for the application of LGS substrates under high-temperature vacuum conditions arise from these substrate damages, revealing that the pretreatment does not improve the applicability. Full article
(This article belongs to the Section Advanced Composites)
Figures

Open AccessFeature PaperArticle Development of Porous Piezoceramics for Medical and Sensor Applications
Materials 2015, 8(12), 8877-8889; doi:10.3390/ma8125498
Received: 4 November 2015 / Revised: 4 December 2015 / Accepted: 10 December 2015 / Published: 21 December 2015
Cited by 3 | PDF Full-text (2899 KB) | HTML Full-text | XML Full-text
Abstract
The use of porosity to modify the functional properties of piezoelectric ceramics is well known in the scientific literature as well as by the industry, and porous ceramic can be seen as a 2-phase composite. In the present work, examples are given of
[...] Read more.
The use of porosity to modify the functional properties of piezoelectric ceramics is well known in the scientific literature as well as by the industry, and porous ceramic can be seen as a 2-phase composite. In the present work, examples are given of applications where controlled porosity is exploited in order to optimise the dielectric, piezoelectric and acoustic properties of the piezoceramics. For the optimisation efforts it is important to note that the thickness coupling coefficient kt will be maximised for some non-zero value of the porosity that could be above 20%. On the other hand, with a good approximation, the acoustic velocity decreases linearly with increasing porosity, which is obviously also the case for the density. Consequently, the acoustic impedance shows a rather strong decrease with porosity, and in practice a reduction of more than 50% may be obtained for an engineered porous ceramic. The significance of the acoustic impedance is associated with the transmission of acoustic signals through the interface between the piezoceramic and some medium of propagation, but when the porous ceramic is used as a substrate for a piezoceramic thick film, the attenuation may be equally important. In the case of open porosity it is possible to introduce a liquid into the pores, and examples of modifying the properties in this way are given. Full article
(This article belongs to the Special Issue Piezoelectric Materials)

Review

Jump to: Research, Other

Open AccessFeature PaperReview Anti-Ferroelectric Ceramics for High Energy Density Capacitors
Materials 2015, 8(12), 8009-8031; doi:10.3390/ma8125439
Received: 29 September 2015 / Revised: 2 November 2015 / Accepted: 11 November 2015 / Published: 25 November 2015
Cited by 24 | PDF Full-text (3361 KB) | HTML Full-text | XML Full-text
Abstract
With an ever increasing dependence on electrical energy for powering modern equipment and electronics, research is focused on the development of efficient methods for the generation, storage and distribution of electrical power. In this regard, the development of suitable dielectric based solid-state capacitors
[...] Read more.
With an ever increasing dependence on electrical energy for powering modern equipment and electronics, research is focused on the development of efficient methods for the generation, storage and distribution of electrical power. In this regard, the development of suitable dielectric based solid-state capacitors will play a key role in revolutionizing modern day electronic and electrical devices. Among the popular dielectric materials, anti-ferroelectrics (AFE) display evidence of being a strong contender for future ceramic capacitors. AFE materials possess low dielectric loss, low coercive field, low remnant polarization, high energy density, high material efficiency, and fast discharge rates; all of these characteristics makes AFE materials a lucrative research direction. However, despite the evident advantages, there have only been limited attempts to develop this area. This article attempts to provide a focus to this area by presenting a timely review on the topic, on the relevant scientific advancements that have been made with respect to utilization and development of anti-ferroelectric materials for electric energy storage applications. The article begins with a general introduction discussing the need for high energy density capacitors, the present solutions being used to address this problem, and a brief discussion of various advantages of anti-ferroelectric materials for high energy storage applications. This is followed by a general description of anti-ferroelectricity and important anti-ferroelectric materials. The remainder of the paper is divided into two subsections, the first of which presents various physical routes for enhancing the energy storage density while the latter section describes chemical routes for enhanced storage density. This is followed by conclusions and future prospects and challenges which need to be addressed in this particular field. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
Open AccessFeature PaperReview Effect of Water Nutrient Pollution on Long-Term Corrosion of 90:10 Copper Nickel Alloy
Materials 2015, 8(12), 8047-8058; doi:10.3390/ma8125443
Received: 26 September 2015 / Revised: 17 November 2015 / Accepted: 20 November 2015 / Published: 27 November 2015
PDF Full-text (3554 KB) | HTML Full-text | XML Full-text
Abstract
Due to their good corrosion resistance, copper and copper alloys such as 90:10 Cu-Ni are used extensively in high-quality marine and industrial piping systems and also in marine, urban, and industrial environments. Their corrosion loss and pitting behaviour tends to follow a bi-modal
[...] Read more.
Due to their good corrosion resistance, copper and copper alloys such as 90:10 Cu-Ni are used extensively in high-quality marine and industrial piping systems and also in marine, urban, and industrial environments. Their corrosion loss and pitting behaviour tends to follow a bi-modal trend rather than the classic power law. Field data for 90:10 copper nickel immersed in natural seawater are used to explore the effect of water pollution and in particular the availability of critical nutrients for microbiologically induced corrosion. It is shown, qualitatively, that increased dissolved inorganic nitrogen increases corrosion predominantly in the second, long-term, mode of the model. Other, less pronounced, influences are salinity and dissolved oxygen concentration. Full article
Open AccessFeature PaperReview Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics
Materials 2015, 8(12), 8117-8146; doi:10.3390/ma8125449
Received: 16 October 2015 / Revised: 16 November 2015 / Accepted: 20 November 2015 / Published: 1 December 2015
Cited by 31 | PDF Full-text (8599 KB) | HTML Full-text | XML Full-text
Abstract
The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining
[...] Read more.
The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na)/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions) and different atmospheres (i.e., defect chemistry) on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT). Full article
(This article belongs to the Special Issue Piezoelectric Materials)
Figures

Open AccessFeature PaperReview Elastic Properties and Enhanced Piezoelectric Response at Morphotropic Phase Boundaries
Materials 2015, 8(12), 8195-8245; doi:10.3390/ma8125452
Received: 2 October 2015 / Revised: 13 November 2015 / Accepted: 18 November 2015 / Published: 2 December 2015
Cited by 10 | PDF Full-text (1973 KB) | HTML Full-text | XML Full-text
Abstract
The search for improved piezoelectric materials is based on the morphotropic phase boundaries (MPB) between ferroelectric phases with different crystal symmetry and available directions for the spontaneous polarization. Such regions of the composition x − T phase diagrams provide the conditions for minimal
[...] Read more.
The search for improved piezoelectric materials is based on the morphotropic phase boundaries (MPB) between ferroelectric phases with different crystal symmetry and available directions for the spontaneous polarization. Such regions of the composition x − T phase diagrams provide the conditions for minimal anisotropy with respect to the direction of the polarization, so that the polarization can easily rotate maintaining a substantial magnitude, while the near verticality of the TMPB(x) boundary extends the temperature range of the resulting enhanced piezoelectricity. Another consequence of the quasi-isotropy of the free energy is a reduction of the domain walls energies, with consequent formation of domain structures down to nanoscale. Disentangling the extrinsic and intrinsic contributions to the piezoelectricity in such conditions requires a high level of sophistication from the techniques and analyses for studying the structural, ferroelectric and dielectric properties. The elastic characterization is extremely useful in clarifying the phenomenology and mechanisms related to ferroelectric MPBs. The relationship between dielectric, elastic and piezoelectric responses is introduced in terms of relaxation of defects with electric dipole and elastic quadrupole, and extended to the response near phase transitions in the framework of the Landau theory. An account is provided of the anelastic experiments, from torsional pendulum to Brillouin scattering, that provided new important information on ferroelectric MPBs, including PZT, PMN-PT, NBT-BT, BCTZ, and KNN-based systems. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
Figures

Open AccessFeature PaperReview Bismuth Sodium Titanate Based Materials for Piezoelectric Actuators
Materials 2015, 8(12), 8467-8495; doi:10.3390/ma8125469
Received: 19 October 2015 / Revised: 13 November 2015 / Accepted: 23 November 2015 / Published: 4 December 2015
Cited by 14 | PDF Full-text (5759 KB) | HTML Full-text | XML Full-text
Abstract
The ban of lead in many electronic products and the expectation that, sooner or later, this ban will include the currently exempt piezoelectric ceramics based on Lead-Zirconate-Titanate has motivated many research groups to look for lead-free substitutes. After a short overview on different
[...] Read more.
The ban of lead in many electronic products and the expectation that, sooner or later, this ban will include the currently exempt piezoelectric ceramics based on Lead-Zirconate-Titanate has motivated many research groups to look for lead-free substitutes. After a short overview on different classes of lead-free piezoelectric ceramics with large strain, this review will focus on Bismuth-Sodium-Titanate and its solid solutions. These compounds exhibit extraordinarily high strain, due to a field induced phase transition, which makes them attractive for actuator applications. The structural features of these materials and the origin of the field-induced strain will be revised. Technologies for texturing, which increases the useable strain, will be introduced. Finally, the features that are relevant for the application of these materials in a multilayer design will be summarized. Full article
(This article belongs to the Special Issue Piezoelectric Materials)
Open AccessReview Recent Progress in Lectin-Based Biosensors
Materials 2015, 8(12), 8590-8607; doi:10.3390/ma8125478
Received: 23 October 2015 / Revised: 25 November 2015 / Accepted: 2 December 2015 / Published: 9 December 2015
Cited by 8 | PDF Full-text (1543 KB) | HTML Full-text | XML Full-text
Abstract
This article reviews recent progress in the development of lectin-based biosensors used for the determination of glucose, pathogenic bacteria and toxins, cancer cells, and lectins. Lectin proteins have been widely used for the construction of optical and electrochemical biosensors by exploiting the specific
[...] Read more.
This article reviews recent progress in the development of lectin-based biosensors used for the determination of glucose, pathogenic bacteria and toxins, cancer cells, and lectins. Lectin proteins have been widely used for the construction of optical and electrochemical biosensors by exploiting the specific binding affinity to carbohydrates. Among lectin proteins, concanavalin A (Con A) is most frequently used for this purpose as glucose- and mannose-selective lectin. Con A is useful for immobilizing enzymes including glucose oxidase (GOx) and horseradish peroxidase (HRP) on the surface of a solid support to construct glucose and hydrogen peroxide sensors, because these enzymes are covered with intrinsic hydrocarbon chains. Con A-modified electrodes can be used as biosensors sensitive to glucose, cancer cells, and pathogenic bacteria covered with hydrocarbon chains. The target substrates are selectively adsorbed to the surface of Con A-modified electrodes through strong affinity of Con A to hydrocarbon chains. A recent topic in the development of lectin-based biosensors is a successful use of nanomaterials, such as metal nanoparticles and carbon nanotubes, for amplifying output signals of the sensors. In addition, lectin-based biosensors are useful for studying glycan expression on living cells. Full article
Open AccessReview Graphene-Based Materials for Stem Cell Applications
Materials 2015, 8(12), 8674-8690; doi:10.3390/ma8125481
Received: 30 September 2015 / Revised: 18 November 2015 / Accepted: 1 December 2015 / Published: 11 December 2015
Cited by 7 | PDF Full-text (5460 KB) | HTML Full-text | XML Full-text
Abstract
Although graphene and its derivatives have been proven to be suitable for several biomedical applications such as for cancer therapy and biosensing, the use of graphene for stem cell research is a relatively new area that has only recently started to be investigated.
[...] Read more.
Although graphene and its derivatives have been proven to be suitable for several biomedical applications such as for cancer therapy and biosensing, the use of graphene for stem cell research is a relatively new area that has only recently started to be investigated. For stem cell applications, graphene has been utilized by itself or in combination with other types of materials such as nanoparticles, nanofibers, and polymer scaffolds to take advantage of the several unique properties of graphene, such as the flexibility in size, shape, hydrophilicity, as well as its excellent biocompatibility. In this review, we will highlight a number of previous studies that have investigated the potential of graphene or its derivatives for stem cell applications, with a particular focus on guiding stem cell differentiation into specific lineages (e.g., osteogenesis, neurogenesis, and oligodendrogenesis), promoting stem cell growth, stem cell delivery/transplantation, and effective monitoring of their differentiation. We hope that this review promotes and accelerates the use of graphene-based materials for regenerative therapies, especially for stem cell-based approaches to cure various incurable diseases/disorders such as neurological diseases (e.g., Alzheimer’s disease and Parkinson’s disease), stroke, spinal cord injuries, bone/cartilage defects, and cardiovascular diseases. Full article
(This article belongs to the Special Issue Graphene)
Open AccessReview Melt-Flow Behaviours of Thermoplastic Materials under Fire Conditions: Recent Experimental Studies and Some Theoretical Approaches
Materials 2015, 8(12), 8793-8803; doi:10.3390/ma8125492
Received: 16 September 2015 / Revised: 26 October 2015 / Accepted: 8 December 2015 / Published: 15 December 2015
PDF Full-text (681 KB) | HTML Full-text | XML Full-text
Abstract
Polymeric materials often exhibit complex combustion behaviours encompassing several stages and involving solid phase, gas phase and interphase. A wide range of qualitative, semi-quantitative and quantitative testing techniques are currently available, both at the laboratory scale and for commercial purposes, for evaluating the
[...] Read more.
Polymeric materials often exhibit complex combustion behaviours encompassing several stages and involving solid phase, gas phase and interphase. A wide range of qualitative, semi-quantitative and quantitative testing techniques are currently available, both at the laboratory scale and for commercial purposes, for evaluating the decomposition and combustion behaviours of polymeric materials. They include, but are not limited to, techniques such as: thermo-gravimetric analysis (TGA), oxygen bomb calorimetry, limiting oxygen index measurements (LOI), Underwriters Laboratory 94 (UL-94) tests, cone calorimetry, etc. However, none of the above mentioned techniques are capable of quantitatively deciphering the underpinning physiochemical processes leading to the melt flow behaviour of thermoplastics. Melt-flow of polymeric materials can constitute a serious secondary hazard in fire scenarios, for example, if they are present as component parts of a ceiling in an enclosure. In recent years, more quantitative attempts to measure the mass loss and melt-drip behaviour of some commercially important chain- and step-growth polymers have been accomplished. The present article focuses, primarily, on the experimental and some theoretical aspects of melt-flow behaviours of thermoplastics under heat/fire conditions. Full article

Other

Jump to: Research, Review

Open AccessCorrection Correction: Preparation, Characterization and Evaluation of α-Tocopherol Succinate-Modified Dextran Micelles as Potential Drug Carriers. Materials 2015, 8, 6685–6696
Materials 2015, 8(12), 8147; doi:10.3390/ma8125448
Received: 24 November 2015 / Accepted: 24 November 2015 / Published: 1 December 2015
Cited by 1 | PDF Full-text (143 KB) | HTML Full-text | XML Full-text
Abstract
The authors wish to make the following correction to their paper [1]. [...] Full article
(This article belongs to the Section Biomaterials)
Open AccessAddendum Addendum: Keller, L.; et al. Integrating Microtissues in Nanofiber Scaffolds for Regenerative Nanomedicine. Materials 2015, 8, 6863–6867
Materials 2015, 8(12), 8423; doi:10.3390/ma8125466
Received: 2 December 2015 / Accepted: 2 December 2015 / Published: 3 December 2015
PDF Full-text (138 KB) | HTML Full-text | XML Full-text
Abstract
The Materials Editorial Office wishes to make the following erratum to this paper. Full article
Open AccessCorrection Correction: Electrochemical Investigation of the Corrosion of Different Microstructural Phases of X65 Pipeline Steel under Saturated Carbon Dioxide Conditions. Materials 2015, 8, 2635–2649
Materials 2015, 8(12), 8728-8730; doi:10.3390/ma8125485
Received: 26 November 2015 / Accepted: 10 December 2015 / Published: 11 December 2015
PDF Full-text (147 KB) | HTML Full-text | XML Full-text
Abstract
In the published manuscript “Electrochemical Investigation of the Corrosion of Different Microstructural Phases of X65 Pipeline Steel under Saturated Carbon Dioxide Conditions. [...] Full article

Journal Contact

MDPI AG
Materials Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
E-Mail: 
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Materials Edit a special issue Review for Materials
logo
loading...
Back to Top