Materials

9 pages, 197 KiB

Open AccessReview

Translucency of Dental Ceramic, Post and Bracket

by Yong-Keun Lee

Materials 2015, 8(11), 7241-7249; https://doi.org/10.3390/ma8115379 - 28 Oct 2015

Cited by 22 | Viewed by 5858

Translucency of dental ceramics, esthetic posts and orthodontic brackets was reviewed. Translucency parameter (TP) and contrast ratio (CR) are generally used for translucency evaluation. For the evaluation of translucency, two criteria such as the translucency of human teeth ( [...] Read more.

Translucency of dental ceramics, esthetic posts and orthodontic brackets was reviewed. Translucency parameter (TP) and contrast ratio (CR) are generally used for translucency evaluation. For the evaluation of translucency, two criteria such as the translucency of human teeth (TP = 15–19, 1 mm thick) and the visual perceptibility threshold for the translucency difference (∆CR > 0.07 or ∆TP > 2) were used. In ceramics, translucency differences were in the perceptible range depending on the type of material and the thickness. However, variations caused by the difference in the required thickness for each layer by the material and also by the measurement protocols should be considered. As to the translucency of esthetic posts, a significant difference was found among the post systems. Translucency was influenced by the bracket composition and brand, and the differences by the brand were visually perceptible. Full article

(This article belongs to the Section Biomaterials)

7 pages, 2249 KiB

Open AccessCommunication

1-(Triethoxysilyl)buta-1,3-dienes—New Building Blocks for Stereoselective Synthesis of Unsymmetrical (E,E)-1,4-Disubstituted 1,3-dienes

by Justyna Szudkowska-Frątczak, Mariusz Taczała and Piotr Pawluć

Materials 2015, 8(11), 7250-7256; https://doi.org/10.3390/ma8115378 - 28 Oct 2015

Cited by 4 | Viewed by 5241

Abstract

A convenient methodology for the highly stereoselective synthesis of unsymmetrical (1E,3E)-1,4-disubstituted 1,3-dienes based on palladium-catalyzed Hiyama cross-coupling reaction of 1-(triethoxysilyl)-substituted buta-1,3-dienes with aryl iodides is reported. Full article

(This article belongs to the Special Issue Organometallic Compounds 2015)

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12 pages, 1689 KiB

Open AccessArticle

Molecular Dynamics Simulation of the Effect of Angle Variation on Water Permeability through Hourglass-Shaped Nanopores

by Dai Tang, Longnan Li, Majid Shahbabaei, Yeong-Eun Yoo and Daejoong Kim

Materials 2015, 8(11), 7257-7268; https://doi.org/10.3390/ma8115380 - 29 Oct 2015

Cited by 18 | Viewed by 8401

Abstract

Water transport through aquaporin water channels occurs extensively in cell membranes. Hourglass-shaped (biconical) pores resemble the geometry of these aquaporin channels and therefore attract much research attention. We assumed that hourglass-shaped nanopores are capable of high water permeation like biological aquaporins. In order [...] Read more.

Water transport through aquaporin water channels occurs extensively in cell membranes. Hourglass-shaped (biconical) pores resemble the geometry of these aquaporin channels and therefore attract much research attention. We assumed that hourglass-shaped nanopores are capable of high water permeation like biological aquaporins. In order to prove the assumption, we investigated nanoscale water transport through a model hourglass-shaped pore using molecular dynamics simulations while varying the angle of the conical entrance and the total nanopore length. The results show that a minimal departure from optimized cone angle (e.g., 9° for 30 Å case) significantly increases the osmotic permeability and that there is a non-linear relationship between permeability and the cone angle. The analysis of hydrodynamic resistance proves that the conical entrance helps to reduce the hydrodynamic entrance hindrance. Our numerical and analytical results thus confirm our initial assumption and suggest that fast water transport can be achieved by adjusting the cone angle and length of an hourglass-shaped nanopore. Full article

(This article belongs to the Special Issue Selected Papers from ICBEI2015)

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9 pages, 1457 KiB

Open AccessArticle

Biocompatibility Evaluation of Dental Luting Cements Using Cytokine Released from Human Oral Fibroblasts and Keratinocytes

by Jae-Sung Kwon, Yin-Zhu Piao, Sun-A Cho, Song-Yi Yang, Ji Hoon Kim, Susun An and Kwang-Mahn Kim

Materials 2015, 8(11), 7269-7277; https://doi.org/10.3390/ma8115372 - 29 Oct 2015

Cited by 6 | Viewed by 6759

Abstract

Dental luting cements are commonly used in dentistry for cementation of prosthetic restoration. Many previous studies focused on the measurement of the cell viability as the method of cytotoxicity evaluation during biocompatibility study for the material. In this study, the biocompatibility of various [...] Read more.

Dental luting cements are commonly used in dentistry for cementation of prosthetic restoration. Many previous studies focused on the measurement of the cell viability as the method of cytotoxicity evaluation during biocompatibility study for the material. In this study, the biocompatibility of various dental luting cements were evaluated using the new method of cytokine release measurement in order to better simulate inflammatory reactions in animal or clinical model using two different oral cells; immortalized human gingival fibroblast and immortalized human oral keratinocytes. Cells were exposed to extractions of various commercially available dental luting cements for different durations. Cytokines of IL-1α and IL-8 were measured from the supernatants of the cells and the results were then compared to the conventional MTT viability test. The result from the conventional cell viability study showed a relatively simple and straight forward indication that only one of the dental luting cements tested in this study was cytotoxic with increasing duration of exposure for both cells. Meanwhile, the result from the cytokine measurement study was much more complex at the time point they were measured, type of cells used for the study and the type of cytokines measured, all of which influenced the interpretation of the results. Hence, the better understanding of the cytokine release would be required for the application in biocompatibility evaluation. Full article

(This article belongs to the Section Biomaterials)

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31 pages, 862 KiB

Open AccessReview

Green Synthesis of Metallic Nanoparticles via Biological Entities

by Monaliben Shah, Derek Fawcett, Shashi Sharma, Suraj Kumar Tripathy and Gérrard Eddy Jai Poinern

Materials 2015, 8(11), 7278-7308; https://doi.org/10.3390/ma8115377 - 29 Oct 2015

Cited by 1042 | Viewed by 49438

Abstract

Nanotechnology is the creation, manipulation and use of materials at the nanometre size scale (1 to 100 nm). At this size scale there are significant differences in many material properties that are normally not seen in the same materials at larger scales. Although [...] Read more.

Nanotechnology is the creation, manipulation and use of materials at the nanometre size scale (1 to 100 nm). At this size scale there are significant differences in many material properties that are normally not seen in the same materials at larger scales. Although nanoscale materials can be produced using a variety of traditional physical and chemical processes, it is now possible to biologically synthesize materials via environment-friendly green chemistry based techniques. In recent years, the convergence between nanotechnology and biology has created the new field of nanobiotechnology that incorporates the use of biological entities such as actinomycetes algae, bacteria, fungi, viruses, yeasts, and plants in a number of biochemical and biophysical processes. The biological synthesis via nanobiotechnology processes have a significant potential to boost nanoparticles production without the use of harsh, toxic, and expensive chemicals commonly used in conventional physical and chemical processes. The aim of this review is to provide an overview of recent trends in synthesizing nanoparticles via biological entities and their potential applications. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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13 pages, 3430 KiB

Open AccessArticle

Mechanical Properties and Eco-Efficiency of Steel Fiber Reinforced Alkali-Activated Slag Concrete

by Sun-Woo Kim, Seok-Joon Jang, Dae-Hyun Kang, Kyung-Lim Ahn and Hyun-Do Yun

Materials 2015, 8(11), 7309-7321; https://doi.org/10.3390/ma8115383 - 30 Oct 2015

Cited by 59 | Viewed by 6322

Abstract

Conventional concrete production that uses ordinary Portland cement (OPC) as a binder seems unsustainable due to its high energy consumption, natural resource exhaustion and huge carbon dioxide (CO₂) emissions. To transform the conventional process of concrete production to a more sustainable [...] Read more.

Conventional concrete production that uses ordinary Portland cement (OPC) as a binder seems unsustainable due to its high energy consumption, natural resource exhaustion and huge carbon dioxide (CO₂) emissions. To transform the conventional process of concrete production to a more sustainable process, the replacement of high energy-consumptive PC with new binders such as fly ash and alkali-activated slag (AAS) from available industrial by-products has been recognized as an alternative. This paper investigates the effect of curing conditions and steel fiber inclusion on the compressive and flexural performance of AAS concrete with a specified compressive strength of 40 MPa to evaluate the feasibility of AAS concrete as an alternative to normal concrete for CO₂ emission reduction in the concrete industry. Their performances are compared with reference concrete produced using OPC. The eco-efficiency of AAS use for concrete production was also evaluated by binder intensity and CO₂ intensity based on the test results and literature data. Test results show that it is possible to produce AAS concrete with compressive and flexural performances comparable to conventional concrete. Wet-curing and steel fiber inclusion improve the mechanical performance of AAS concrete. Also, the utilization of AAS as a sustainable binder can lead to significant CO₂ emissions reduction and resources and energy conservation in the concrete industry. Full article

(This article belongs to the Section Advanced Composites)

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20 pages, 4099 KiB

Open AccessArticle

Damage Characterization of Bio and Green Polyethylene–Birch Composites under Creep and Cyclic Testing with Multivariable Acoustic Emissions

by Alencar Bravo, Lotfi Toubal, Demagna Koffi and Fouad Erchiqui

Materials 2015, 8(11), 7322-7341; https://doi.org/10.3390/ma8115382 - 2 Nov 2015

Cited by 24 | Viewed by 8593

Abstract

Despite the knowledge gained in recent years regarding the use of acoustic emissions (AEs) in ecologically friendly, natural fiber-reinforced composites (including certain composites with bio-sourced matrices), there is still a knowledge gap in the understanding of the difference in damage behavior between green [...] Read more.

Despite the knowledge gained in recent years regarding the use of acoustic emissions (AEs) in ecologically friendly, natural fiber-reinforced composites (including certain composites with bio-sourced matrices), there is still a knowledge gap in the understanding of the difference in damage behavior between green and biocomposites. Thus, this article investigates the behavior of two comparable green and biocomposites with tests that better reflect real-life applications, i.e., load-unloading and creep testing, to determine the evolution of the damage process. Comparing the mechanical results with the AE, it can be concluded that the addition of a coupling agent (CA) markedly reduced the ratio of AE damage to mechanical damage. CA had an extremely beneficial effect on green composites because the Kaiser effect was dominant during cyclic testing. During the creep tests, the use of a CA also avoided the transition to new damaging phases in both composites. The long-term applications of PE green material must be chosen carefully because bio and green composites with similar properties exhibited different damage processes in tests such as cycling and creep that could not be previously understood using only monotonic testing. Full article

(This article belongs to the Special Issue Green Composites)

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12 pages, 4514 KiB

Open AccessArticle

Microstructure Investigation of 13Cr-2Mo ODS Steel Components Obtained by High Voltage Electric Discharge Compaction Technique

by Igor Bogachev, Artem Yudin, Evgeniy Grigoryev, Ivan Chernov, Maxim Staltsov, Oleg Khasanov and Eugene Olevsky

Materials 2015, 8(11), 7342-7353; https://doi.org/10.3390/ma8115381 - 2 Nov 2015

Cited by 9 | Viewed by 6528

Abstract

Refractory oxide dispersion strengthened 13Cr-2Mo steel powder was successfully consolidated to near theoretical density using high voltage electric discharge compaction. Cylindrical samples with relative density from 90% to 97% and dimensions of 10 mm in diameter and 10–15 mm in height were obtained. [...] Read more.

Refractory oxide dispersion strengthened 13Cr-2Mo steel powder was successfully consolidated to near theoretical density using high voltage electric discharge compaction. Cylindrical samples with relative density from 90% to 97% and dimensions of 10 mm in diameter and 10–15 mm in height were obtained. Consolidation conditions such as pressure and voltage were varied in some ranges to determine the optimal compaction regime. Three different concentrations of yttria were used to identify its effect on the properties of the samples. It is shown that the utilized ultra-rapid consolidation process in combination with high transmitted energy allows obtaining high density compacts, retaining the initial structure with minimal grain growth. The experimental results indicate some heterogeneity of the structure which may occur in the external layers of the tested samples due to various thermal and electromagnetic in-processing effects. The choice of the optimal parameters of the consolidation enables obtaining samples of acceptable quality. Full article

(This article belongs to the Collection Spark-Plasma Sintering and Related Field-Assisted Powder Consolidation Technologies)

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17 pages, 3218 KiB

Open AccessArticle

Light Steel-Timber Frame with Composite and Plaster Bracing Panels

by Roberto Scotta, Davide Trutalli, Laura Fiorin, Luca Pozza, Luca Marchi and Lorenzo De Stefani

Materials 2015, 8(11), 7354-7370; https://doi.org/10.3390/ma8115386 - 3 Nov 2015

Cited by 13 | Viewed by 12557

Abstract

The proposed light-frame structure comprises steel columns for vertical loads and an innovative bracing system to efficiently resist seismic actions. This seismic force resisting system consists of a light timber frame braced with an Oriented Strand Board (OSB) sheet and an external technoprene [...] Read more.

The proposed light-frame structure comprises steel columns for vertical loads and an innovative bracing system to efficiently resist seismic actions. This seismic force resisting system consists of a light timber frame braced with an Oriented Strand Board (OSB) sheet and an external technoprene plaster-infilled slab. Steel brackets are used as foundation and floor connections. Experimental cyclic-loading tests were conduced to study the seismic response of two shear-wall specimens. A numerical model was calibrated on experimental results and the dynamic non-linear behavior of a case-study building was assessed. Numerical results were then used to estimate the proper behavior factor value, according to European seismic codes. Obtained results demonstrate that this innovative system is suitable for the use in seismic-prone areas thanks to the high ductility and dissipative capacity achieved by the bracing system. This favorable behavior is mainly due to the fasteners and materials used and to the correct application of the capacity design approach. Full article

(This article belongs to the Section Advanced Materials Characterization)

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18 pages, 6832 KiB

Open AccessArticle

Thermo-Mechanical Behaviour of Flax-Fibre Reinforced Epoxy Laminates for Industrial Applications

by Giuseppe Pitarresi, Davide Tumino and Antonio Mancuso

Materials 2015, 8(11), 7371-7388; https://doi.org/10.3390/ma8115384 - 3 Nov 2015

Cited by 27 | Viewed by 7274

Abstract

The present work describes the experimental mechanical characterisation of a natural flax fibre reinforced epoxy polymer composite. A commercial plain woven quasi-unidirectional flax fabric with spun-twisted yarns is employed in particular, as well as unidirectional composite panels manufactured with three techniques: hand-lay-up, vacuum [...] Read more.

The present work describes the experimental mechanical characterisation of a natural flax fibre reinforced epoxy polymer composite. A commercial plain woven quasi-unidirectional flax fabric with spun-twisted yarns is employed in particular, as well as unidirectional composite panels manufactured with three techniques: hand-lay-up, vacuum bagging and resin infusion. The stiffness and strength behaviours are investigated under both monotonic and low-cycle fatigue loadings. The analysed material has, in particular, shown a typical bilinear behaviour under pure traction, with a knee yield point occurring at a rather low stress value, after which the material tensile stiffness is significantly reduced. In the present work, such a mechanism is investigated by a phenomenological approach, performing periodical loading/unloading cycles, and repeating tensile tests on previously “yielded” samples to assess the evolution of stiffness behaviour. Infrared thermography is also employed to measure the temperature of specimens during monotonic and cyclic loading. In the first case, the thermal signal is monitored to correlate departures from the thermoelastic behaviour with the onset of energy loss mechanisms. In the case of cyclic loading, the thermoelastic signal and the second harmonic component are both determined in order to investigate the extent of elastic behaviour of the material. Full article

(This article belongs to the Special Issue Green Composites)

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12 pages, 4170 KiB

Open AccessArticle

Fabrication of Solid State Nanopore in Thin Silicon Membrane Using Low Cost Multistep Chemical Etching

by Muhammad Shuja Khan and John Dalton Williams

Materials 2015, 8(11), 7389-7400; https://doi.org/10.3390/ma8115390 - 3 Nov 2015

Cited by 14 | Viewed by 7887

Abstract

Nanopore-based analysis is currently an area of great interest in many disciplines with the potential for exceptionally versatile applications in medicine. This work presents a novel step towards fabrication of a single solid-state nanopore (SSSN) in a thin silicon membrane. Silicon nanopores are [...] Read more.

Nanopore-based analysis is currently an area of great interest in many disciplines with the potential for exceptionally versatile applications in medicine. This work presents a novel step towards fabrication of a single solid-state nanopore (SSSN) in a thin silicon membrane. Silicon nanopores are realized using multistep processes on both sides of n-type silicon-on-insulator (SOI) <100> wafer with resistivity 1–4 Ω·cm. An electrochemical HF etch with low current density (0.47 mA/cm²) is employed to produce SSSN. Blue LED is considered to emit light in a narrow band region which facilitates the etching procedure in a unilateral direction. This helps in production of straight nanopores in n-type Si. Additionally, a variety of pore diameters are demonstrated using different HF concentrations. Atomic force microscopy is used to demonstrate the surface morphology of the fabricated pores in non-contact mode. Pore edges exhibit a pronounced rounded shape and can offer high stability to fluidic artificial lipid bilayer to study membrane proteins. Electrochemically-fabricated SSSN has excellent smoothness and potential applications in diagnostics and pharmaceutical research on transmembrane proteins and label free detection. Full article

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22 pages, 4366 KiB

Open AccessArticle

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material

by Jan Valíček, Marta Harničárová, Andreas Öchsner, Zuzana Hutyrová, Milena Kušnerová, Hakan Tozan, Vít Michenka, Vladimír Šepelák, Dušan Mitaľ and Jozef Zajac

Materials 2015, 8(11), 7401-7422; https://doi.org/10.3390/ma8115385 - 3 Nov 2015

Cited by 27 | Viewed by 8032

Abstract

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by [...] Read more.

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ. Full article

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16 pages, 3074 KiB

Open AccessFeature PaperReview

Potassium Sodium Niobate-Based Lead-Free Piezoelectric Multilayer Ceramics Co-Fired with Nickel Electrodes

by Shinichiro Kawada, Hiroyuki Hayashi, Hideki Ishii, Masahiko Kimura, Akira Ando, Suetake Omiya and Noriyuki Kubodera

Materials 2015, 8(11), 7423-7438; https://doi.org/10.3390/ma8115389 - 3 Nov 2015

Cited by 22 | Viewed by 8990

Abstract

Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer [...] Read more.

Although lead-free piezoelectric ceramics have been extensively studied, many problems must still be overcome before they are suitable for practical use. One of the main problems is fabricating a multilayer structure, and one solution attracting growing interest is the use of lead-free multilayer piezoelectric ceramics. The paper reviews work that has been done by the authors on lead-free alkali niobate-based multilayer piezoelectric ceramics co-fired with nickel inner electrodes. Nickel inner electrodes have many advantages, such as high electromigration resistance, high interfacial strength with ceramics, and greater cost effectiveness than silver palladium inner electrodes. However, widely used lead zirconate titanate-based ceramics cannot be co-fired with nickel inner electrodes, and silver palladium inner electrodes are usually used for lead zirconate titanate-based piezoelectric ceramics. A possible alternative is lead-free ceramics co-fired with nickel inner electrodes. We have thus been developing lead-free alkali niobate-based multilayer ceramics co-fired with nickel inner electrodes. The normalized electric-field-induced thickness strain (S_max/E_max) of a representative alkali niobate-based multilayer ceramic structure with nickel inner electrodes was 360 pm/V, where S_max denotes the maximum strain and E_max denotes the maximum electric field. This value is about half that for the lead zirconate titanate-based ceramics that are widely used. However, a comparable value can be obtained by stacking more ceramic layers with smaller thicknesses. In the paper, the compositional design and process used to co-fire lead-free ceramics with nickel inner electrodes are introduced, and their piezoelectric properties and reliabilities are shown. Recent advances are introduced, and future development is discussed. Full article

(This article belongs to the Special Issue Piezoelectric Materials)

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8 pages, 7379 KiB

Open AccessArticle

Analysis of Fatigue Crack Paths in Cold Drawn Pearlitic Steel

by Jesús Toribio, Beatriz González and Juan-Carlos Matos

Materials 2015, 8(11), 7439-7446; https://doi.org/10.3390/ma8115388 - 4 Nov 2015

Cited by 18 | Viewed by 8300

Abstract

In this paper, a fracto-metallographic analysis was performed on the cracked specimens of cold drawn pearlitic steel subjected to fatigue tests. Fatigue cracks are transcollonial and exhibit a preference for fracturing pearlitic lamellae, with non-uniform crack opening displacement values, micro-discontinuities, branchings, bifurcations and [...] Read more.

In this paper, a fracto-metallographic analysis was performed on the cracked specimens of cold drawn pearlitic steel subjected to fatigue tests. Fatigue cracks are transcollonial and exhibit a preference for fracturing pearlitic lamellae, with non-uniform crack opening displacement values, micro-discontinuities, branchings, bifurcations and frequent local deflections that create microstructural roughness. At the micro-level, the cold drawn pearlitic steel exhibits higher micro-roughness than the hot rolled bar (this is a consequence of the manufacturing process by cold drawing), so that the actual fractured surface in the cold drawn wire is greater than that in the hot rolled bar, due to the fact that the crack deflection events are more frequent and with higher angle in the former (the heavily drawn prestressing steel wire). These findings show the relevant role on the manufacturing process by cold drawing in the fatigue crack propagation in pearlitic steel. Full article

(This article belongs to the Special Issue Surface Modification Methods to Improve Fatigue, Fretting Fatigue, and Fretting Wear Behavior of Materials)

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14 pages, 6952 KiB

Open AccessArticle

Microstructural Evolution at Micro/Meso-Scale in an Ultrafine-Grained Pure Aluminum Processed by Equal-Channel Angular Pressing with Subsequent Annealing Treatment

by Jie Xu, Jianwei Li, Xiaocheng Zhu, Guohua Fan, Debin Shan and Bin Guo

Materials 2015, 8(11), 7447-7460; https://doi.org/10.3390/ma8115391 - 4 Nov 2015

Cited by 11 | Viewed by 6367

Abstract

Micro-forming with ultrafine-grained (UFG) materials is a promising direction for the fabrication of micro-electro-mechanical systems (MEMS) components due to the improved formability, good surface quality, and excellent mechanical properties it provides. In this paper, micro-compression tests were performed using UFG pure aluminum processed [...] Read more.

Micro-forming with ultrafine-grained (UFG) materials is a promising direction for the fabrication of micro-electro-mechanical systems (MEMS) components due to the improved formability, good surface quality, and excellent mechanical properties it provides. In this paper, micro-compression tests were performed using UFG pure aluminum processed by equal-channel angular pressing (ECAP) with subsequent annealing treatment. Microstructural evolution was investigated by electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that microstructural evolutions during compression tests at the micro/meso-scale in UFG pure Al are absolutely different from the coarse-grained (CG) materials. A lot of low-angle grain boundaries (LAGBs) and recrystallized fine grains are formed inside of the original large grains in CG pure aluminum after micro-compression. By contrast, ultrafine grains are kept with few sub-grain boundaries inside the grains in UFG pure aluminum, which are similar to the original microstructure before micro-compression. The surface roughness and coordinated deformation ability can be signmicrostructure; micro/meso-forming; ultrafine grains; ECAP; aluminumificantly improved with UFG pure aluminum, which demonstrates that the UFG materials have a strong potential application in micro/meso-forming. Full article

(This article belongs to the Section Advanced Materials Characterization)

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11 pages, 1529 KiB

Open AccessReview

Active Nanomaterials to Meet the Challenge of Dental Pulp Regeneration

by Laetitia Keller, Damien Offner, Pascale Schwinté, David Morand, Quentin Wagner, Catherine Gros, Fabien Bornert, Sophie Bahi, Anne-Marie Musset, Nadia Benkirane-Jessel and Florence Fioretti

Materials 2015, 8(11), 7461-7471; https://doi.org/10.3390/ma8115387 - 5 Nov 2015

Cited by 28 | Viewed by 10742

Abstract

The vitality of the pulp is fundamental to the functional life of the tooth. For this aim, active and living biomaterials are required to avoid the current drastic treatment, which is the removal of all the cellular and molecular content regardless of its [...] Read more.

The vitality of the pulp is fundamental to the functional life of the tooth. For this aim, active and living biomaterials are required to avoid the current drastic treatment, which is the removal of all the cellular and molecular content regardless of its regenerative potential. The regeneration of the pulp tissue is the dream of many generations of dental surgeons and will revolutionize clinical practices. Recently, the potential of the regenerative medicine field suggests that it would be possible to achieve such complex regeneration. Indeed, three crucial steps are needed: the control of infection and inflammation and the regeneration of lost pulp tissues. For regenerative medicine, in particular for dental pulp regeneration, the use of nano-structured biomaterials becomes decisive. Nano-designed materials allow the concentration of many different functions in a small volume, the increase in the quality of targeting, as well as the control of cost and delivery of active molecules. Nanomaterials based on extracellular mimetic nanostructure and functionalized with multi-active therapeutics appear essential to reverse infection and inflammation and concomitantly to orchestrate pulp cell colonization and differentiation. This novel generation of nanomaterials seems very promising to meet the challenge of the complex dental pulp regeneration. Full article

(This article belongs to the Special Issue Therapeutics Delivery Systems for Regenerative Nanomedicine)

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14 pages, 4148 KiB

Open AccessArticle

Reconstituted Keratin Biomaterial with Enhanced Ductility

by Halleh Atri, Elham Bidram and David E. Dunstan

Materials 2015, 8(11), 7472-7485; https://doi.org/10.3390/ma8115392 - 5 Nov 2015

Cited by 11 | Viewed by 6298

Abstract

Nowadays the waste from protein fibres represents an important renewable source for a new generation of biomaterials and promising competitors for carbohydrate based biomaterials. Regenerated keratin biomaterials are biodegradable in vivo and in vitro, biocompatible, and support cell attachment and proliferation; however, [...] Read more.

Nowadays the waste from protein fibres represents an important renewable source for a new generation of biomaterials and promising competitors for carbohydrate based biomaterials. Regenerated keratin biomaterials are biodegradable in vivo and in vitro, biocompatible, and support cell attachment and proliferation; however, their major drawback has been their weak mechanical properties such as ductility. The following study was conducted in an attempt to improve the ductility of reconstituted keratin films obtained from Australian merino wool fibres. Keratin was extracted from wool fibres according to an established protocol proposed by Yamauchi, and then dialyzed and desalted by multiple diafiltration wash cycles. The resulting keratin film was transparent, biodegradable, and, opposite to its predecessors, mechanically durable, possessing a Young modulus about 12.5 MPa with 35% extensibility. The polypeptide chains were found to rearrange themselves in the β-sheet state in this keratin film, which was shown to be semi-crystalline. This film, unlike its predecessors, did not support human cell proliferation. These properties of the diafiltered keratin film have led us to think that diafiltration resulted in producing a totally new keratin film, which is envisaged to find applications in various areas. Full article

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12 pages, 1382 KiB

Open AccessArticle

Retention Strength of PMMA/UDMA-Based Crowns Bonded to Dentin: Impact of Different Coupling Agents for Pretreatment

by Bogna Stawarczyk, Simona Teuss, Marlis Eichberger, Malgorzata Roos and Christine Keul

Materials 2015, 8(11), 7486-7497; https://doi.org/10.3390/ma8115396 - 6 Nov 2015

Cited by 9 | Viewed by 5809

Abstract

Computer aided design/computer aided manufacturing (CAD/CAM) polymers for long-term dental restorations benefit from enhanced mechanical properties. However, the quantification of their bonding properties on teeth is lacking. Therefore, the aim of this study was to determine the retention strength (RS) of differently pretreated [...] Read more.

Computer aided design/computer aided manufacturing (CAD/CAM) polymers for long-term dental restorations benefit from enhanced mechanical properties. However, the quantification of their bonding properties on teeth is lacking. Therefore, the aim of this study was to determine the retention strength (RS) of differently pretreated new developed polymethylmethacrylate/ urethanedimethacrylate-based CAD/CAM polymer bonded on dentin. In summary, 120 human caries-free molars were prepared, and polymeric crowns were milled and pretreated (n = 20): visio.link (VL), Scotchbond Universal (SU), Monobond Plus/Heliobond (MH), Margin Bond (MB), Margin Bond mixed with acetone (1:1) (MBA) or not pretreated (CG). Half of the specimens were cemented using Variolink II and the other half with RelyX Ultimate. Specimens were stored for 24 h in distilled water and thermal cycled (5000 ×, 5 °C/55 °C). The retention load was measured and failure types were defined. RS was calculated and analyzed using both two- and one-way ANOVA with a post-hoc Scheffé-test, unpaired t-test, Kaplan–Meier with Breslow–Gehan test and chi-squared test (p < 0.05). Crowns bonded using RelyX Ultimate showed higher RS than those bonded using Variolink II. The pretreatment showed no impact on the RS. However, survival analysis within Variolink II found an impact of pretreatment. The median RS for MH was the lowest and statistically different from MB, MBA and CG. For Variolink II MH had the poorest survival as the estimated cumulative failure function of the debonded crown increased very quickly with increasing TBS. Within the RelyX Ultimate groups, no significant differences were determined. The newly developed CAD/CAM polymer showed the highest bonding properties after cementation using RelyX Ultimate. Full article

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13 pages, 6299 KiB

Open AccessArticle

Enhanced Stability of Calcium Sulfate Scaffolds with 45S5 Bioglass for Bone Repair

by Cijun Shuai, Jianhua Zhou, Ping Wu, Chengde Gao, Pei Feng, Tao Xiao, Youwen Deng and Shuping Peng

Materials 2015, 8(11), 7498-7510; https://doi.org/10.3390/ma8115398 - 6 Nov 2015

Cited by 18 | Viewed by 6793

Abstract

Calcium sulfate (CaSO₄), as a promising tissue repair material, has been applied widely due to its outstanding bioabsorbability and osteoconduction. However, fast disintegration, insufficient mechanical strength and poor bioactivity have limited its further application. In the study, CaSO₄ scaffolds fabricated [...] Read more.

Calcium sulfate (CaSO₄), as a promising tissue repair material, has been applied widely due to its outstanding bioabsorbability and osteoconduction. However, fast disintegration, insufficient mechanical strength and poor bioactivity have limited its further application. In the study, CaSO₄ scaffolds fabricated by using selective laser sintering were improved by adding 45S5 bioglass. The 45S5 bioglass enhanced stability significantly due to the bond effect of glassy phase between the CaSO₄ grains. After immersing for four days in simulated body fluid (SBF), the specimens with 45S5 bioglass could still retain its original shape compared as opposed to specimens without 45S5 bioglass who experienced disintegration. Meanwhile, its compressive strength and fracture toughness increased by 80% and 37%, respectively. Furthermore, the apatite layer was formed on the CaSO₄ scaffolds with 45S5 bioglass in SBF, indicating good bioactivity of the scaffolds. In addition, the scaffolds showed good ability to support the osteoblast-like cell adhesion and proliferation. Full article

(This article belongs to the Section Biomaterials)

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8 pages, 8413 KiB

Open AccessArticle

Sound Absorption Characteristics of Aluminum Foams Treated by Plasma Electrolytic Oxidation

by Wei Jin, Jiaan Liu, Zhili Wang, Yonghua Wang, Zheng Cao, Yaohui Liu and Xianyong Zhu

Materials 2015, 8(11), 7511-7518; https://doi.org/10.3390/ma8115395 - 9 Nov 2015

Cited by 21 | Viewed by 7828

Abstract

Open-celled aluminum foams with different pore sizes were fabricated. A plasma electrolytic oxidation (PEO) treatment was applied on the aluminum foams to create a layer of ceramic coating. The sound absorption coefficients of the foams were measured by an impedance tube and they [...] Read more.

Open-celled aluminum foams with different pore sizes were fabricated. A plasma electrolytic oxidation (PEO) treatment was applied on the aluminum foams to create a layer of ceramic coating. The sound absorption coefficients of the foams were measured by an impedance tube and they were calculated by a transfer function method. The experimental results show that the sound absorption coefficient of the foam increases gradually with the decrease of pore size. Additionally, when the porosity of the foam increases, the sound absorption coefficient also increases. The PEO coating surface is rough and porous, which is beneficial for improvement in sound absorption. After PEO treatment, the maximum sound absorption of the foam is improved to some extent. Full article

(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)

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5 pages, 2907 KiB

Open AccessArticle

Microwave Annealing for NiSiGe Schottky Junction on SiGe P-Channel

by Yu-Hsien Lin, Yi-He Tsai, Chung-Chun Hsu, Guang-Li Luo, Yao-Jen Lee and Chao-Hsin Chien

Materials 2015, 8(11), 7519-7523; https://doi.org/10.3390/ma8115403 - 10 Nov 2015

Cited by 2 | Viewed by 5659

Abstract

In this paper, we demonstrated the shallow NiSiGe Schottky junction on the SiGe P-channel by using low-temperature microwave annealing. The NiSiGe/n-Si Schottky junction was formed for the Si-capped/SiGe multi-layer structure on an n-Si substrate (Si/Si_0.57Ge_0.43/Si) through microwave annealing (MWA) [...] Read more.

In this paper, we demonstrated the shallow NiSiGe Schottky junction on the SiGe P-channel by using low-temperature microwave annealing. The NiSiGe/n-Si Schottky junction was formed for the Si-capped/SiGe multi-layer structure on an n-Si substrate (Si/Si_0.57Ge_0.43/Si) through microwave annealing (MWA) ranging from 200 to 470 °C for 150 s in N₂ ambient. MWA has the advantage of being diffusion-less during activation, having a low-temperature process, have a lower junction leakage current, and having low sheet resistance (Rs) and contact resistivity. In our study, a 20 nm NiSiGe Schottky junction was formed by TEM and XRD analysis at MWA 390 °C. The NiSiGe/n-Si Schottky junction exhibits the highest forward/reverse current (I_ON/I_OFF) ratio of ~3 × 10⁵. The low temperature MWA is a very promising thermal process technology for NiSiGe Schottky junction manufacturing. Full article

(This article belongs to the Section Advanced Materials Characterization)

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12 pages, 5563 KiB

Open AccessArticle

Surface Irregularity Factor as a Parameter to Evaluate the Fatigue Damage State of CFRP

by Pablo Zuluaga-Ramírez, Malte Frövel, Tomás Belenguer and Félix Salazar

Materials 2015, 8(11), 7524-7535; https://doi.org/10.3390/ma8115407 - 11 Nov 2015

Cited by 6 | Viewed by 7771

Abstract

This work presents an optical non-contact technique to evaluate the fatigue damage state of CFRP structures measuring the irregularity factor of the surface. This factor includes information about surface topology and can be measured easily on field, by techniques such as optical perfilometers. [...] Read more.

This work presents an optical non-contact technique to evaluate the fatigue damage state of CFRP structures measuring the irregularity factor of the surface. This factor includes information about surface topology and can be measured easily on field, by techniques such as optical perfilometers. The surface irregularity factor has been correlated with stiffness degradation, which is a well-accepted parameter for the evaluation of the fatigue damage state of composite materials. Constant amplitude fatigue loads (CAL) and realistic variable amplitude loads (VAL), representative of real in- flight conditions, have been applied to “dog bone” shaped tensile specimens. It has been shown that the measurement of the surface irregularity parameters can be applied to evaluate the damage state of a structure, and that it is independent of the type of fatigue load that has caused the damage. As a result, this measurement technique is applicable for a wide range of inspections of composite material structures, from pressurized tanks with constant amplitude loads, to variable amplitude loaded aeronautical structures such as wings and empennages, up to automotive and other industrial applications. Full article

(This article belongs to the Special Issue Failure Analysis in Materials)

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13 pages, 5971 KiB

Open AccessArticle

Mechanical, Thermomechanical and Reprocessing Behavior of Green Composites from Biodegradable Polymer and Wood Flour

by Marco Morreale, Antonio Liga, Maria Chiara Mistretta, Laura Ascione and Francesco Paolo La Mantia

Materials 2015, 8(11), 7536-7548; https://doi.org/10.3390/ma8115406 - 11 Nov 2015

Cited by 72 | Viewed by 7187

Abstract

The rising concerns in terms of environmental protection and the search for more versatile polymer-based materials have led to an increasing interest in the use of polymer composites filled with natural organic fillers (biodegradable and/or coming from renewable resources) as a replacement for [...] Read more.

The rising concerns in terms of environmental protection and the search for more versatile polymer-based materials have led to an increasing interest in the use of polymer composites filled with natural organic fillers (biodegradable and/or coming from renewable resources) as a replacement for traditional mineral inorganic fillers. At the same time, the recycling of polymers is still of fundamental importance in order to optimize the utilization of available resources, reducing the environmental impact related to the life cycle of polymer-based items. Green composites from biopolymer matrix and wood flour were prepared and the investigation focused on several issues, such as the effect of reprocessing on the matrix properties, wood flour loading effects on virgin and reprocessed biopolymer, and wood flour effects on material reprocessability. Tensile, Dynamic-mechanical thermal (DMTA), differential scanning calorimetry (DSC) and creep tests were performed, pointing out that wood flour leads to an improvement of rigidity and creep resistance in comparison to the pristine polymer, without compromising other properties such as the tensile strength. The biopolymer also showed a good resistance to multiple reprocessing; the latter even allowed for improving some properties of the obtained green composites. Full article

(This article belongs to the Special Issue Green Composites)

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14 pages, 4906 KiB

Open AccessArticle

Oxidation of Ca-α-SiAlON Powders Prepared by Combustion Synthesis

by Jinfu Li, Zhongmin Li, Enhui Wang, Zhanjun Wang, Xiaowei Yin and Zuotai Zhang

Materials 2015, 8(11), 7549-7562; https://doi.org/10.3390/ma8115394 - 11 Nov 2015

Cited by 3 | Viewed by 4973

Abstract

The oxidation of Ca-α-SiAlON synthesized by the combustion synthesis (CS) method with different additives was investigated in air atmosphere using thermogravimetric (TG) analysis in a temperature range from 1453 K to 1653 K. The experimental results indicated that oxidation was controlled by mixed [...] Read more.

The oxidation of Ca-α-SiAlON synthesized by the combustion synthesis (CS) method with different additives was investigated in air atmosphere using thermogravimetric (TG) analysis in a temperature range from 1453 K to 1653 K. The experimental results indicated that oxidation was controlled by mixed chemical and diffusion steps. The oxidation products by XRD analysis were composed of SiO₂ and CaAl₂Si₂O₈ at low oxidation temperature, whereas the SiO₂-Al₂O₃-CaO ternary glassy phase was formed at elevated temperature. The deviation of oxidation resistance from each sample may be due to the morphological difference brought about by different additive additions. This study reveals the effects of additives on the oxidation resistance of synthesized Ca-α-SiAlON powders. Full article

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15 pages, 2903 KiB

Open AccessArticle

Intelligent Optimization of the Film-to-Fiber Ratio of a Degradable Braided Bicomponent Ureteral Stent

by Xiaoyan Liu, Feng Li, Yongsheng Ding, Ting Zou, Lu Wang and Kuangrong Hao

Materials 2015, 8(11), 7563-7577; https://doi.org/10.3390/ma8115397 - 11 Nov 2015

Cited by 5 | Viewed by 4599

Abstract

A hierarchical support vector regression (SVR) model (HSVRM) was employed to correlate the compositions and mechanical properties of bicomponent stents composed of poly(lactic-co-glycolic acid) (PGLA) film and poly(glycolic acid) (PGA) fibers for urethral repair for the first time. PGLA film and [...] Read more.

A hierarchical support vector regression (SVR) model (HSVRM) was employed to correlate the compositions and mechanical properties of bicomponent stents composed of poly(lactic-co-glycolic acid) (PGLA) film and poly(glycolic acid) (PGA) fibers for urethral repair for the first time. PGLA film and PGA fibers could provide ureteral stents with good compressive and tensile properties, respectively. In bicomponent stents, high film content led to high stiffness, while high fiber content resulted in poor compressional properties. To simplify the procedures to optimize the ratio of PGLA film and PGA fiber in the stents, a hierarchical support vector regression model (HSVRM) and particle swarm optimization (PSO) algorithm were used to construct relationships between the film-to-fiber weight ratio and the measured compressional/tensile properties of the stents. The experimental data and simulated data fit well, proving that the HSVRM could closely reflect the relationship between the component ratio and performance properties of the ureteral stents. Full article

(This article belongs to the Section Biomaterials)

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9 pages, 5001 KiB

Open AccessArticle

Experimental Characterization of the Properties of Double-Lap Needled and Hybrid Joints of Carbon/Epoxy Composites

by A. Arnautov, A. Nasibullins, V. Gribniak, I. Blumbergs and M. Hauka

Materials 2015, 8(11), 7578-7586; https://doi.org/10.3390/ma8115410 - 11 Nov 2015

Cited by 28 | Viewed by 5580

Abstract

The effect of through-thickness reinforcement by thin 1 mm steel needles (z-pins) on the static tensile strength of double-lap joints of a carbon/epoxy composite was investigated. Two types of joints—z-pinned and hybrid (including glued ones)—were considered. The joints were reinforced in the overlap [...] Read more.

The effect of through-thickness reinforcement by thin 1 mm steel needles (z-pins) on the static tensile strength of double-lap joints of a carbon/epoxy composite was investigated. Two types of joints—z-pinned and hybrid (including glued ones)—were considered. The joints were reinforced in the overlap region with 9, 25, or 36 z-pins. Comparing mechanical properties of the double-lap joints with the corresponding characteristics of their unpinned counterparts, the z-pins were found to be highly effective: the strength and stiffness of the pinned joints increased up to 300% and 280%, respectively. These improvements were due to a transition in the failure mechanism from debonding of the joint in the absence of z-pins to pullout or shear rupture of z-pins or to the tensile failure of laminate adherends, depending on the volume content of the pins. Full article

(This article belongs to the Section Advanced Composites)

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2 pages, 159 KiB

Open AccessCorrection

Correction: McKinnon M.B. and Stoliarov S.I. Pyrolysis Model Development for a Multilayer Floor Covering. Materials 2015, 8, 6117–6153

by Mark B. McKinnon and Stanislav I. Stoliarov

Materials 2015, 8(11), 7587-7588; https://doi.org/10.3390/ma8115402 - 11 Nov 2015

Viewed by 4019

Abstract

The authors wish to make the following corrections to this manuscript [1]. During the publishing process, symbols that represented the absorption coefficient in Table 4 and thermal conductivity in Table 5 were changed such that they were inconsistent with the rest of the [...] Read more.

The authors wish to make the following corrections to this manuscript [1]. During the publishing process, symbols that represented the absorption coefficient in Table 4 and thermal conductivity in Table 5 were changed such that they were inconsistent with the rest of the manuscript. [...] Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

9 pages, 1557 KiB

Open AccessArticle

Influence of Residual Stress Field on the Fatigue Crack Propagation in Prestressing Steel Wires

by Jesús Toribio, Juan-Carlos Matos, Beatriz González and José Escuadra

Materials 2015, 8(11), 7589-7597; https://doi.org/10.3390/ma8115400 - 11 Nov 2015

Cited by 9 | Viewed by 4684

Abstract

This paper deals with the effect of several residual stress profiles on the fatigue crack propagation in prestressing steel wires subjected to tension loading or bending moment. To this end, a computer program was developed to evaluate the crack front evolution on the [...] Read more.

This paper deals with the effect of several residual stress profiles on the fatigue crack propagation in prestressing steel wires subjected to tension loading or bending moment. To this end, a computer program was developed to evaluate the crack front evolution on the basis of the Walker law. Results demonstrate that the absence of residual stresses makes the crack propagate towards a preferential crack path. When surface residual stresses are tensile and, correspondingly, core residual stresses are compressive, the fatigue crack fronts rapidly converge towards a quasi-straight shape. When surface residual stresses are compressive, with their corresponding tensile stresses in the core area, a preferential crack path also appears. Full article

(This article belongs to the Special Issue Surface Modification Methods to Improve Fatigue, Fretting Fatigue, and Fretting Wear Behavior of Materials)

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6 pages, 2130 KiB

Open AccessArticle

Temperature-Dependent Photoluminescence Property of Self-Assembly ZnO Nanowires via Chemical Vapor Deposition Combined with Hydrothermal Pretreatment

by Zongxiao Li and Xiangli Liu

Materials 2015, 8(11), 7598-7603; https://doi.org/10.3390/ma8115393 - 11 Nov 2015

Cited by 4 | Viewed by 5635

Abstract

Vertically aligned ZnO nanowires with high aspect ratio were prepared by chemical vapor deposition on Si substrate, which had been catalyzed by the polar plane in [0001] direction of ZnO nanorods prepared by the hydrothermal method. Morphology and structure characterizations showed that the [...] Read more.

Vertically aligned ZnO nanowires with high aspect ratio were prepared by chemical vapor deposition on Si substrate, which had been catalyzed by the polar plane in [0001] direction of ZnO nanorods prepared by the hydrothermal method. Morphology and structure characterizations showed that the as-grown nanowires had the single-crystal hexagonal wurtzite structure with a [0001] growth direction. Energy Dispersive X-ray (EDX) measurement indicated the as-grown ZnO nanowires had a good deal of oxygen vacancies owing to the high operation temperature. Temperature-dependent photoluminescence measurement revealed that the peak of near-band-edge emission shifted from 380 to 387 nm with the increase of temperature from 150 to 300 K. The high intensity of the green peak at 525 nm highlighted the potential application in visible light emitting diodes. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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11 pages, 2816 KiB

Open AccessReview

Patchwork Coating of Fragmented Ultra-Thin Films and Their Biomedical Applications in Burn Therapy and Antithrombotic Coating

by Yosuke Okamura, Yu Nagase and Shinji Takeoka

Materials 2015, 8(11), 7604-7614; https://doi.org/10.3390/ma8115404 - 11 Nov 2015

Cited by 7 | Viewed by 5543

Abstract

We have proposed free-standing centimeter-sized ultra-thin films (nanosheets) for biomedical applications. Such nanosheets exhibit unique properties such as transparency, flexibility, and good adhesiveness. However, they are only easily adhered to broad and flat surfaces due to their dimensions. To this end, we recently [...] Read more.

We have proposed free-standing centimeter-sized ultra-thin films (nanosheets) for biomedical applications. Such nanosheets exhibit unique properties such as transparency, flexibility, and good adhesiveness. However, they are only easily adhered to broad and flat surfaces due to their dimensions. To this end, we recently proposed an innovative nanomaterial: the nanosheets fragmented into submillimeter-size pieces. Intriguingly, such fragmented nanosheets could be adhered to uneven and irregular surfaces in addition to flat surfaces in a spread-out “patchwork” manner. We herein review the fabrication procedure and characterization of fragmented nanosheets composed of biodegradable polyesters and thermostable bio-friendly polymers, and their biomedical applications in burn therapy and antithrombotic coating using a “patchwork coating”. Full article

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7 pages, 985 KiB

Open AccessArticle

Evaluation of the Adsorption Performance and Sustainability of Exfoliated Graphite Nanoplatelets (xGnP) for VOCs

by Seong Jin Chang, Seunghwan Wi, Su-Gwang Jeong and Sumin Kim

Materials 2015, 8(11), 7615-7621; https://doi.org/10.3390/ma8115412 - 11 Nov 2015

Cited by 6 | Viewed by 5393

Abstract

Exfoliated graphite nanoplatelets (xGnP), which combine the layered structure and low price of nanoclays with the superior mechanical, electrical, and thermal properties of carbon nanotubes, are very cost-effective, and can simultaneously provide a multitude of physical and chemical property enhancements. In this study, [...] Read more.

Exfoliated graphite nanoplatelets (xGnP), which combine the layered structure and low price of nanoclays with the superior mechanical, electrical, and thermal properties of carbon nanotubes, are very cost-effective, and can simultaneously provide a multitude of physical and chemical property enhancements. In this study, we evaluated xGnP’s adsorption performance of volatile organic compounds (VOCs) according to thermal extractor (TE) analysis for seven days in order to use the xGnP as an adsorption material of pollutants. In addition, we carried out a sustainability evaluation in order to evaluate its adsorption capacity over 28 days. The results indicate that the adsorption performance of xGnP is higher than for other adsorption materials such as zeolite. Also, we determined that the adsorption performance of xGnP is maintained continuously for 28 days and that its adsorption capacity is large. Full article

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12 pages, 2401 KiB

Open AccessArticle

Modulating the Optoelectronic Properties of Silver Nanowires Films: Effect of Capping Agent and Deposition Technique

by D. Lopez-Diaz, C. Merino and M. M. Velázquez

Materials 2015, 8(11), 7622-7633; https://doi.org/10.3390/ma8115405 - 11 Nov 2015

Cited by 15 | Viewed by 6422

Abstract

Silver nanowires 90 nm in diameter and 9 µm in length have been synthesized using different capping agents: polyvinyl pyrrolidone (PVP) and alkyl thiol of different chain lengths. The nanowire structure is not influenced by the displacement of PVP by alkyl thiols, although [...] Read more.

Silver nanowires 90 nm in diameter and 9 µm in length have been synthesized using different capping agents: polyvinyl pyrrolidone (PVP) and alkyl thiol of different chain lengths. The nanowire structure is not influenced by the displacement of PVP by alkyl thiols, although alkyl thiols modify the lateral aggregation of nanowires. We examined the effect of the capping agent and the deposition method on the optical and electrical properties of films prepared by Spray and the Langmuir-Schaefer methodologies. Our results revealed that nanowires capped with PVP and C8-thiol present the best optoelectronic properties. By using different deposition techniques and by modifying the nanowire surface density, we can modulate the optoelectronic properties of films. This strategy allows obtaining films with the optoelectronic properties required to manufacture touch screens and electromagnetic shielding. Full article

(This article belongs to the Section Advanced Materials Characterization)

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16 pages, 6233 KiB

Open AccessArticle

Reduction of Adipose Tissue Formation by the Controlled Release of BMP-2 Using a Hydroxyapatite-Coated Collagen Carrier System for Sinus-Augmentation/Extraction-Socket Grafting

by Jung-Seok Lee, Tae-Wan Kim, Soyon Park, Byung-Soo Kim, Gun-Il Im, Kyoo-Sung Cho and Chang-Sung Kim

Materials 2015, 8(11), 7634-7649; https://doi.org/10.3390/ma8115411 - 11 Nov 2015

Cited by 14 | Viewed by 6512

Abstract

The effects of hydroxyapatite (HA)-coating onto collagen carriers for application of recombinant human bone morphogenetic protein 2 (rhBMP-2) on cell differentiation in vitro, and on in vivo healing patterns after sinus-augmentation and alveolar socket-grafting were evaluated. In vitro induction of osteogenic/adipogenic differentiation [...] Read more.

The effects of hydroxyapatite (HA)-coating onto collagen carriers for application of recombinant human bone morphogenetic protein 2 (rhBMP-2) on cell differentiation in vitro, and on in vivo healing patterns after sinus-augmentation and alveolar socket-grafting were evaluated. In vitro induction of osteogenic/adipogenic differentiation was compared between the culture media with rhBMP-2 solution and with the released rhBMP-2 from the control collagen and from the HA-coated collagen. Demineralized bovine bone and collagen/HA-coated collagen were grafted with/without rhBMP-2 in sinus-augmentation and tooth-extraction-socket models. Adipogenic induction by rhBMP-2 released from HA-coated collagen was significantly reduced compared to collagen. In the sinus-augmentation model, sites that received rhBMP-2 exhibited large amounts of vascular tissue formation at two weeks and increased adipose tissue formation at eight weeks; this could be significantly reduced by using HA-coated collagen as a carrier for rhBMP-2. In extraction-socket grafting, dimensional reduction of alveolar ridge was significantly decreased at sites received rhBMP-2 compared to control sites, but adipose tissue was increased within the regenerated socket area. In conclusion, HA-coated collagen carrier for Escherichia coli-derived rhBMP-2 (ErhBMP-2) may reduce in vitro induction of adipogenic differentiation and in vivo adipose bone marrow tissue formation in bone tissue engineering by ErhBMP-2. Full article

(This article belongs to the Special Issue Selected Papers from ICBEI2015)

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13 pages, 7196 KiB

Open AccessArticle

High Temperature Deformation of Twin-Roll Cast Al-Mn-Based Alloys after Equal Channel Angular Pressing

by Přemysl Málek, Michaela Šlapáková Poková and Miroslav Cieslar

Materials 2015, 8(11), 7650-7662; https://doi.org/10.3390/ma8115401 - 12 Nov 2015

Cited by 6 | Viewed by 5228

Abstract

Twin roll cast Al-Mn- and Al-Mn-Zr-based alloys were subjected to four passes of equal channel angular pressing. The resulting grain size of 400 nm contributes to a significant strengthening at room temperature. This microstructure is not fully stable at elevated temperatures and recrystallization [...] Read more.

Twin roll cast Al-Mn- and Al-Mn-Zr-based alloys were subjected to four passes of equal channel angular pressing. The resulting grain size of 400 nm contributes to a significant strengthening at room temperature. This microstructure is not fully stable at elevated temperatures and recrystallization and vast grain growth occur at temperatures between 350 and 450 °C. The onset of these microstructure changes depends on chemical and phase composition. Better stability is observed in the Al-Mn-Zr-based alloy. High temperature tensile tests reveal that equal channel angular pressing results in a softening of all studied materials at high temperatures. This can be explained by an active role of grain boundaries in the deformation process. The maximum values of ductility and strain rate sensitivity parameter m found in the Al-Mn-Zr-based alloy are below the bottom limit of superplasticity (155%, m = 0.25). However, some features typical for superplastic behavior were observed—the strain rate dependence of the parameter m, the strengthening with increasing grain size, and the fracture by diffuse necking. Grain boundary sliding is believed to contribute partially to the overall strain in specimens where the grain size remained in the microcrystalline range. Full article

(This article belongs to the Section Advanced Materials Characterization)

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10 pages, 2979 KiB

Open AccessArticle

Enhanced Erbium-Doped Ceria Nanostructure Coating to Improve Solar Cell Performance

by Nader Shehata, Michael Clavel, Kathleen Meehan, Effat Samir, Soha Gaballah and Mohammed Salah

Materials 2015, 8(11), 7663-7672; https://doi.org/10.3390/ma8115399 - 12 Nov 2015

Cited by 26 | Viewed by 7085

Abstract

This paper discusses the effect of adding reduced erbium-doped ceria nanoparticles (REDC NPs) as a coating on silicon solar cells. Reduced ceria nanoparticles doped with erbium have the advantages of both improving conductivity and optical conversion of solar cells. Oxygen vacancies in ceria [...] Read more.

This paper discusses the effect of adding reduced erbium-doped ceria nanoparticles (REDC NPs) as a coating on silicon solar cells. Reduced ceria nanoparticles doped with erbium have the advantages of both improving conductivity and optical conversion of solar cells. Oxygen vacancies in ceria nanoparticles reduce Ce⁴⁺ to Ce³⁺ which follow the rule of improving conductivity of solar cells through the hopping mechanism. The existence of Ce³⁺ helps in the down-conversion from 430 nm excitation to 530 nm emission. The erbium dopant forms energy levels inside the low-phonon ceria host to up-convert the 780 nm excitations into green and red emissions. When coating reduced erbium-doped ceria nanoparticles on the back side of a solar cell, a promising improvement in the solar cell efficiency has been observed from 15% to 16.5% due to the mutual impact of improved electric conductivity and multi-optical conversions. Finally, the impact of the added coater on the electric field distribution inside the solar cell has been studied. Full article

(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices)

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17 pages, 5641 KiB

Open AccessArticle

Chitosan-Coated Collagen Membranes Promote Chondrocyte Adhesion, Growth, and Interleukin-6 Secretion

by Nabila Mighri, Jifu Mao, Frej Mighri, Abdallah Ajji and Mahmoud Rouabhia

Materials 2015, 8(11), 7673-7689; https://doi.org/10.3390/ma8115413 - 13 Nov 2015

Cited by 21 | Viewed by 7254

Abstract

Designing scaffolds made from natural polymers may be highly attractive for tissue engineering strategies. We sought to produce and characterize chitosan-coated collagen membranes and to assess their efficacy in promoting chondrocyte adhesion, growth, and cytokine secretion. Porous collagen membranes were placed in chitosan [...] Read more.

Designing scaffolds made from natural polymers may be highly attractive for tissue engineering strategies. We sought to produce and characterize chitosan-coated collagen membranes and to assess their efficacy in promoting chondrocyte adhesion, growth, and cytokine secretion. Porous collagen membranes were placed in chitosan solutions then crosslinked with glutaraldehyde vapor. Fourier transform infrared (FTIR) analyses showed elevated absorption at 1655 cm^-1 of the carbon–nitrogen (N=C) bonds formed by the reaction between the (NH₂) of the chitosan and the (C=O) of the glutaraldehyde. A significant peak in the amide II region revealed a significant deacetylation of the chitosan. Scanning electron microscopy (SEM) images of the chitosan-coated membranes exhibited surface variations, with pore size ranging from 20 to 50 µm. X-ray photoelectron spectroscopy (XPS) revealed a decreased C–C groups and an increased C–N/C–O groups due to the reaction between the carbon from the collagen and the NH2 from the chitosan. Increased rigidity of these membranes was also observed when comparing the chitosan-coated and uncoated membranes at dried conditions. However, under wet conditions, the chitosan coated collagen membranes showed lower rigidity as compared to dried conditions. Of great interest, the glutaraldehyde-crosslinked chitosan-coated collagen membranes promoted chondrocyte adhesion, growth, and interleukin (IL)-6 secretion. Overall results confirm the feasibility of using designed chitosan-coated collagen membranes in future applications, such as cartilage repair. Full article

(This article belongs to the Special Issue Cellular Materials: Design and Optimisation)

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1 pages, 175 KiB

Open AccessErratum

Erratum: Jarý, V.; et al. Optical, Structural and Paramagnetic Properties of Eu-Doped Ternary Sulfides ALnS₂ (A = Na, K, Rb; Ln = La, Gd, Lu, Y). Materials 2015, 8, 6978–6998

by Materials Editorial Office

Materials 2015, 8(11), 7690; https://doi.org/10.3390/ma8115420 - 13 Nov 2015

Viewed by 3288

Abstract

The Materials Editorial Office wishes to make the following erratum to this paper [1]. [...] Full article

11 pages, 4976 KiB

Open AccessArticle

Preparation of SiO₂-Protecting Metallic Fe Nanoparticle/SiO₂ Composite Spheres for Biomedical Application

by Pin-Wei Hsieh, Ching-Li Tseng and Dong-Hau Kuo

Materials 2015, 8(11), 7691-7701; https://doi.org/10.3390/ma8115416 - 13 Nov 2015

Cited by 8 | Viewed by 9045

Abstract

Functionalized Fe nanoparticles (NPs) have played an important role in biomedical applications. In this study, metallic Fe NPs were deposited on SiO₂ spheres to form a Fe/SiO₂ composite. To protect the Fe from oxidation, a thin SiO₂ layer was coated [...] Read more.

Functionalized Fe nanoparticles (NPs) have played an important role in biomedical applications. In this study, metallic Fe NPs were deposited on SiO₂ spheres to form a Fe/SiO₂ composite. To protect the Fe from oxidation, a thin SiO₂ layer was coated on the Fe/SiO₂ spheres thereafter. The size and morphology of the SiO₂@Fe/SiO₂ composite spheres were examined by transmission electron microscopy (TEM). The iron form and its content and magnetic properties were examined by X-ray diffraction (XRD), inductively-coupled plasma mass spectrometry (ICP-MS) and a superconducting quantum interference device (SQUID). The biocompatibility of the SiO₂@Fe/SiO₂ composite spheres was examined by Cell Counting Kit-8 (CCK-8) and lactate dehydrogenase (LDH) tests. The intracellular distribution of the SiO₂@Fe/SiO₂ composite spheres was observed using TEM. XRD analysis revealed the formation of metallic iron on the surface of the SiO₂ spheres. According to the ICP-MS and SQUID results, using 0.375 M FeCl₃·6H₂O for Fe NPs synthesis resulted in the highest iron content and magnetization of the SiO₂@Fe/SiO₂ spheres. Using a dye loading experiment, a slow release of a fluorescence dye from SiO₂@Fe/SiO₂ composite spheres was confirmed. The SiO₂@Fe/SiO₂ composite spheres co-cultured with L929 cells exhibit biocompatibility at concentrations <16.25 µg/mL. The TEM images show that the SiO₂@Fe/SiO₂ composite spheres were uptaken into the cytoplasm and retained in the endosome. The above results demonstrate that the SiO₂@Fe/SiO₂ composite spheres could be used as a multi-functional agent, such as a magnetic resonance imaging (MRI) contrast agent or drug carriers in biomedical applications. Full article

(This article belongs to the Section Biomaterials)

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12 pages, 2644 KiB

Open AccessArticle

Preparation, Mechanical and Thermal Properties of Cement Board with Expanded Perlite Based Composite Phase Change Material for Improving Buildings Thermal Behavior

by Rongda Ye, Xiaoming Fang, Zhengguo Zhang and Xuenong Gao

Materials 2015, 8(11), 7702-7713; https://doi.org/10.3390/ma8115408 - 13 Nov 2015

Cited by 37 | Viewed by 7154

Abstract

Here we demonstrate the mechanical properties, thermal conductivity, and thermal energy storage performance of construction elements made of cement and form-stable PCM-Rubitherm® RT 28 HC (RT28)/expanded perlite (EP) composite phase change materials (PCMs). The composite PCMs were prepared by adsorbing RT28 into the [...] Read more.

Here we demonstrate the mechanical properties, thermal conductivity, and thermal energy storage performance of construction elements made of cement and form-stable PCM-Rubitherm® RT 28 HC (RT28)/expanded perlite (EP) composite phase change materials (PCMs). The composite PCMs were prepared by adsorbing RT28 into the pores of EP, in which the mass fraction of RT28 should be limited to be no more than 40 wt %. The adsorbed RT28 is observed to be uniformly confined into the pores of EP. The phase change temperatures of the RT28/EP composite PCMs are very close to that of the pure RT28. The apparent density and compression strength of the composite cubes increase linearly with the mass fraction of RT28. Compared with the thermal conductivity of the boards composed of cement and EP, the thermal conductivities of the composite boards containing RT28 increase by 15%–35% with the mass fraction increasing of RT28. The cubic test rooms that consist of six boards were built to evaluate the thermal energy storage performance, it is found that the maximum temperature different between the outside surface of the top board with the indoor temperature using the composite boards is 13.3 °C higher than that of the boards containing no RT28. The thermal mass increase of the built environment due to the application of composite boards can contribute to improving the indoor thermal comfort and reducing the energy consumption in the buildings. Full article

(This article belongs to the Special Issue Development and Characterisation of Encapsulated PCM: Nano-, Micro-, and Macro-Encapsulation)

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9 pages, 2314 KiB

Open AccessArticle

A Novel Biodegradable Polycaprolactone Fixator for Osteosynthesis Surgery of Rib Fracture: In Vitro and in Vivo Study

by Yi-Hsun Yu, Chin-Lung Fan, Yung-Heng Hsu, Ying-Chao Chou, Steve W. N. Ueng and Shih-Jung Liu

Materials 2015, 8(11), 7714-7722; https://doi.org/10.3390/ma8115415 - 13 Nov 2015

Cited by 11 | Viewed by 6159

Abstract

Osteosynthesis surgery for rib fractures is controversial and challenging. This study developed a noval poly(ε-caprolactone) (PCL)-based biodegradable “cable-tie” fixator for osteosynthesis surgery for rib fractures. A biodegradable fixator specifically for fractured ribs was designed and fabricated by a micro-injection molding machine in our [...] Read more.

Osteosynthesis surgery for rib fractures is controversial and challenging. This study developed a noval poly(ε-caprolactone) (PCL)-based biodegradable “cable-tie” fixator for osteosynthesis surgery for rib fractures. A biodegradable fixator specifically for fractured ribs was designed and fabricated by a micro-injection molding machine in our laboratory. The fixator has three belts that could be passed through matching holes individually. The locking mechanism allows the belt movement to move in only one direction. To examine the in vitro biomechanical performance, ribs 3–7 from four fresh New Zealand rabbits were employed. The load to failure and stress-strain curve was compared in the three-point bending test among native ribs, titanium plate-fixed ribs, and PCL fixator-fixed ribs. In the in vivo animal study, the sixth ribs of New Zealand rabbits were osteotomized and osteosynthesis surgery was performed using the PCL fixator. Outcomes were assessed by monthly X-ray examinations, a final micro-computed tomography (CT) scan, and histological analysis. The experimental results suggested that the ribs fixed with the PCL fixator were significantly less stiff than those fixed with titanium plates (p < 0.05). All ribs fixed with the PCL fixators exhibited union. The bridging callus was confirmed by gross, radiographic micro-three-dimensional (3D) CT, and histological examinations. In addition, there was no significant inflammatory response of the osteotomized ribs or the PCL-rib interface during application. The novel PCL fixator developed in this work achieves satisfactory results in osteosynthesis surgery for rib fractures, and may provide potential applications in other orthopedic surgeries. Full article

(This article belongs to the Section Biomaterials)

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15 pages, 244 KiB

Open AccessArticle

Ferrocene Orientation Determined Intramolecular Interactions Using Energy Decomposition Analysis

by Feng Wang, Shawkat Islam and Vladislav Vasilyev

Materials 2015, 8(11), 7723-7737; https://doi.org/10.3390/ma8115419 - 16 Nov 2015

Cited by 14 | Viewed by 6865

Abstract

Two very different quantum mechanically based energy decomposition analyses (EDA) schemes are employed to study the dominant energy differences between the eclipsed and staggered ferrocene conformers. One is the extended transition state (ETS) based on the Amsterdam Density Functional (ADF) package and the [...] Read more.

Two very different quantum mechanically based energy decomposition analyses (EDA) schemes are employed to study the dominant energy differences between the eclipsed and staggered ferrocene conformers. One is the extended transition state (ETS) based on the Amsterdam Density Functional (ADF) package and the other is natural EDA (NEDA) based in the General Atomic and Molecular Electronic Structure System (GAMESS) package. It reveals that in addition to the model (theory and basis set), the fragmentation channels more significantly affect the interaction energy terms (ΔE) between the conformers. It is discovered that such an interaction energy can be absorbed into the pre-partitioned fragment channels so that to affect the interaction energies in a particular conformer of Fc. To avoid this, the present study employs a complete fragment channel—the fragments of ferrocene are individual neutral atoms. It therefore discovers that the major difference between the ferrocene conformers is due to the quantum mechanical Pauli repulsive energy and orbital attractive energy, leading to the eclipsed ferrocene the energy preferred structure. The NEDA scheme further indicates that the sum of attractive (negative) polarization (POL) and charge transfer (CL) energies prefers the eclipsed ferrocene. The repulsive (positive) deformation (DEF) energy, which is dominated by the cyclopentadienyle (Cp) rings, prefers the staggered ferrocene. Again, the cancellation results in a small energy residue in favour of the eclipsed ferrocene, in agreement with the ETS scheme. Further Natural Bond Orbital (NBO) analysis indicates that all NBO energies, total Lewis (no Fe) and lone pair (LP) deletion all prefer the eclipsed Fc conformer. The most significant energy preferring the eclipsed ferrocene without cancellation is the interactions between the donor lone pairs (LP) of the Fe atom and the acceptor antibond (BD*) NBOs of all C–C and C–H bonds in the ligand, LP(Fe)-BD*(C–C & C–H), which strongly stabilizes the eclipsed (D_5h) conformation by −457.6 kcal·mol⁻¹. Full article

(This article belongs to the Special Issue Organometallic Compounds 2015)

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7 pages, 3292 KiB

Open AccessArticle

Effect of Oxide Coating on Performance of Copper-Zinc Oxide-Based Catalyst for Methanol Synthesis via Hydrogenation of Carbon Dioxide

by Tetsuo Umegaki, Yoshiyuki Kojima and Kohji Omata

Materials 2015, 8(11), 7738-7744; https://doi.org/10.3390/ma8115414 - 16 Nov 2015

Cited by 13 | Viewed by 5800

Abstract

The effect of oxide coating on the activity of a copper-zinc oxide–based catalyst for methanol synthesis via the hydrogenation of carbon dioxide was investigated. A commercial catalyst was coated with various oxides by a sol-gel method. The influence of the types of promoters [...] Read more.

The effect of oxide coating on the activity of a copper-zinc oxide–based catalyst for methanol synthesis via the hydrogenation of carbon dioxide was investigated. A commercial catalyst was coated with various oxides by a sol-gel method. The influence of the types of promoters used in the sol-gel reaction was investigated. Temperature-programmed reduction-thermogravimetric analysis revealed that the reduction peak assigned to the copper species in the oxide-coated catalysts prepared using ammonia shifts to lower temperatures than that of the pristine catalyst; in contrast, the reduction peak shifts to higher temperatures for the catalysts prepared using L(+)-arginine. These observations indicated that the copper species were weakly bonded with the oxide and were easily reduced by using ammonia. The catalysts prepared using ammonia show higher CO₂ conversion than the catalysts prepared using L(+)-arginine. Among the catalysts prepared using ammonia, the silica-coated catalyst displayed a high activity at high temperatures, while the zirconia-coated catalyst and titania-coated catalyst had high activity at low temperatures. At high temperature the conversion over the silica-coated catalyst does not significantly change with reaction temperature, while the conversion over the zirconia-coated catalyst and titania-coated catalyst decreases with reaction time. From the results of FTIR, the durability depends on hydrophilicity of the oxides. Full article

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12 pages, 1742 KiB

Open AccessArticle

Origin of the Electroluminescence from Annealed-ZnO/GaN Heterojunction Light-Emitting Diodes

by Kai-Chiang Hsu, Wei-Hua Hsiao, Ching-Ting Lee, Yan-Ting Chen and Day-Shan Liu

Materials 2015, 8(11), 7745-7756; https://doi.org/10.3390/ma8115417 - 16 Nov 2015

Cited by 5 | Viewed by 5830

Abstract

This paper addressed the effect of post-annealed treatment on the electroluminescence (EL) of an n-ZnO/p-GaN heterojunction light-emitting diode (LED). The bluish light emitted from the 450 °C-annealed LED became reddish as the LED annealed at a temperature of 800 °C [...] Read more.

This paper addressed the effect of post-annealed treatment on the electroluminescence (EL) of an n-ZnO/p-GaN heterojunction light-emitting diode (LED). The bluish light emitted from the 450 °C-annealed LED became reddish as the LED annealed at a temperature of 800 °C under vacuum atmosphere. The origins of the light emission for these LEDs annealed at various temperatures were studied using measurements of electrical property, photoluminescence, and Auger electron spectroscopy (AES) depth profiles. A blue-violet emission located at 430 nm was associated with intrinsic transitions between the bandgap of n-ZnO and p-GaN, the green-yellow emission at 550 nm mainly originating from the deep-level transitions of native defects in the n-ZnO and p-GaN surfaces, and the red emission at 610 nm emerging from the Ga-O interlayer due to interdiffusion at the n-ZnO/p-GaN interface. The above-mentioned emissions also supported the EL spectra of LEDs annealed at 700 °C under air, nitrogen, and oxygen atmospheres, respectively. Full article

(This article belongs to the Special Issue Selected Papers from ICASI 2015)

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13 pages, 9171 KiB

Open AccessReview

Creep-Fatigue Failure Diagnosis

by Stuart Holdsworth

Materials 2015, 8(11), 7757-7769; https://doi.org/10.3390/ma8115418 - 16 Nov 2015

Cited by 53 | Viewed by 14350

Abstract

Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of [...] Read more.

Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of loading conditions ranging from pure cyclic to mainly steady loading with infrequent off-load transients. These require a range of mechanical analysis approaches, a number of which are reviewed. The microstructural information revealing material condition can vary with alloy class. In practice, the detail of the consequent cracking mechanism(s) can be camouflaged by oxidation at high temperatures, although the presence of oxide on fracture surfaces can be used to date events leading to failure. Routine laboratory specimen post-test examination is strongly recommended to characterise the detail of deformation and damage accumulation under known and well-controlled loading conditions to improve the effectiveness and efficiency of failure diagnosis. Full article

(This article belongs to the Special Issue Failure Analysis in Materials)

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10 pages, 5346 KiB

Open AccessArticle

New Polylactic Acid Composites Reinforced with Artichoke Fibers

by Luigi Botta, Vincenzo Fiore, Tommaso Scalici, Antonino Valenza and Roberto Scaffaro

Materials 2015, 8(11), 7770-7779; https://doi.org/10.3390/ma8115422 - 16 Nov 2015

Cited by 52 | Viewed by 7116

Abstract

In this work, artichoke fibers were used for the first time to prepare poly(lactic acid) (PLA)-based biocomposites. In particular, two PLA/artichoke composites with the same fiber loading (10% w/w) were prepared by the film-stacking method: the first one (UNID) reinforced [...] Read more.

In this work, artichoke fibers were used for the first time to prepare poly(lactic acid) (PLA)-based biocomposites. In particular, two PLA/artichoke composites with the same fiber loading (10% w/w) were prepared by the film-stacking method: the first one (UNID) reinforced with unidirectional long artichoke fibers, the second one (RANDOM) reinforced by randomly-oriented long artichoke fibers. Both composites were mechanically characterized in tensile mode by quasi-static and dynamic mechanical tests. The morphology of the fracture surfaces was analyzed through scanning electron microscopy (SEM). Moreover, a theoretical model, i.e., Hill’s method, was used to fit the experimental Young’s modulus of the biocomposites. The quasi-static tensile tests revealed that the modulus of UNID composites is significantly higher than that of the neat PLA (i.e., ~40%). Moreover, the tensile strength is slightly higher than that of the neat matrix. The other way around, the stiffness of RANDOM composites is not significantly improved, and the tensile strength decreases in comparison to the neat PLA. Full article

(This article belongs to the Special Issue Green Composites)

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15 pages, 4439 KiB

Open AccessArticle

Variation of Shrinkage Strain within the Depth of Concrete Beams

by Jong-Hyun Jeong, Yeong-Seong Park and Yong-Hak Lee

Materials 2015, 8(11), 7780-7794; https://doi.org/10.3390/ma8115421 - 16 Nov 2015

Cited by 8 | Viewed by 7235

Abstract

The variation of shrinkage strain within beam depth was examined through four series of time-dependent laboratory experiments on unreinforced concrete beam specimens. Two types of beam specimens, horizontally cast and vertically cast, were tested; shrinkage variation was observed in the horizontally cast specimens. [...] Read more.

The variation of shrinkage strain within beam depth was examined through four series of time-dependent laboratory experiments on unreinforced concrete beam specimens. Two types of beam specimens, horizontally cast and vertically cast, were tested; shrinkage variation was observed in the horizontally cast specimens. This indicated that the shrinkage variation within the beam depth was due to water bleeding and tamping during the placement of the fresh concrete. Shrinkage strains were measured within the beam depth by two types of strain gages, surface-attached and embedded. The shrinkage strain distribution within the beam depth showed a consistent tendency for the two types of gages. The test beams were cut into four sections after completion of the test, and the cutting planes were divided into four equal sub-areas to measure the aggregate concentration for each sub-area of the cutting plane. The aggregate concentration increased towards the bottom of the beam. The shrinkage strain distribution was estimated by Hobbs’ equation, which accounts for the change of aggregate volume concentration. Full article

(This article belongs to the Section Advanced Materials Characterization)

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10 pages, 1775 KiB

Open AccessArticle

Preparation and Preliminary Dielectric Characterization of Structured C₆₀-Thiol-Ene Polymer Nanocomposites Assembled Using the Thiol-Ene Click Reaction

by Hanaa M. Ahmed, Amber D. Windham, Maryam M. Al-Ejji, Noora H. Al-Qahtani, Mohammad K. Hassan, Kenneth A. Mauritz, Randy K. Buchanan and J. Paige Buchanan

Materials 2015, 8(11), 7795-7804; https://doi.org/10.3390/ma8115424 - 18 Nov 2015

Cited by 16 | Viewed by 6630

Abstract

Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high [...] Read more.

Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high volume resistivity. A series of structured fullerene (C₆₀) polymer nanocomposites were assembled using the thiol-ene click reaction, between alkyl thiols and allyl functionalized C₆₀ derivatives. The resulting high-density C₆₀-urethane-thiol-ene (C₆₀-Thiol-Ene) networks possessed excellent mechanical properties. These novel networks were characterized using standard techniques, including infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermal gravimetric analysis (TGA). The dielectric spectra for the prepared samples were determined over a broad frequency range at room temperature using a broadband dielectric spectrometer and a semiconductor characterization system. The changes in thermo-mechanical and electrical properties of these novel fullerene-thiol-ene composite films were measured as a function of the C₆₀ content, and samples characterized by high dielectric permittivity and low dielectric loss were produced. In this process, variations in chemical composition of the networks were correlated to performance characteristics. Full article

(This article belongs to the Special Issue Polymer Nanocomposites)

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8 pages, 3967 KiB

Open AccessArticle

Inhibition of Crystal Growth during Plasma Enhanced Atomic Layer Deposition by Applying BIAS

by Stephan Ratzsch, Ernst-Bernhard Kley, Andreas Tünnermann and Adriana Szeghalmi

Materials 2015, 8(11), 7805-7812; https://doi.org/10.3390/ma8115425 - 18 Nov 2015

Cited by 13 | Viewed by 6472

Abstract

In this study, the influence of direct current (DC) biasing on the growth of titanium dioxide (TiO₂) layers and their nucleation behavior has been investigated. Titania films were prepared by plasma enhanced atomic layer deposition (PEALD) using Ti(OiPr)₄ as metal [...] Read more.

In this study, the influence of direct current (DC) biasing on the growth of titanium dioxide (TiO₂) layers and their nucleation behavior has been investigated. Titania films were prepared by plasma enhanced atomic layer deposition (PEALD) using Ti(OiPr)₄ as metal organic precursor. Oxygen plasma, provided by remote inductively coupled plasma, was used as an oxygen source. The TiO₂ films were deposited with and without DC biasing. A strong dependence of the applied voltage on the formation of crystallites in the TiO₂ layer is shown. These crystallites form spherical hillocks on the surface which causes high surface roughness. By applying a higher voltage than the plasma potential no hillock appears on the surface. Based on these results, it seems likely, that ions are responsible for the nucleation and hillock growth. Hence, the hillock formation can be controlled by controlling the ion energy and ion flux. The growth per cycle remains unchanged, whereas the refractive index slightly decreases in the absence of energetic oxygen ions. Full article

(This article belongs to the Special Issue Atomic Layer Deposition of Functional Materials)

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8 pages, 3836 KiB

Open AccessArticle

Magnetic Control of Fe₃O₄ Nanomaterial for Fat Ablation in Microchannel

by Ming Chang, Ming-Yi Chang, Wei-Siou Lin and Jacque Lynn Gabayno

Materials 2015, 8(11), 7813-7820; https://doi.org/10.3390/ma8115429 - 19 Nov 2015

Cited by 7 | Viewed by 5268

Abstract

In this study, surface modification of iron (II, III) oxide Fe₃O₄ nanoparticles by oleic acid (OA) coating is investigated for the microablation of fat in a microchannel. The nanoparticles are synthesized by the co-precipitation method and then dispersed in organic [...] Read more.

In this study, surface modification of iron (II, III) oxide Fe₃O₄ nanoparticles by oleic acid (OA) coating is investigated for the microablation of fat in a microchannel. The nanoparticles are synthesized by the co-precipitation method and then dispersed in organic solvent prior to mixing with the OA. The magnetization, agglomeration, and particle size distribution properties of the OA-coated Fe₃O₄ nanoparticles are characterized. The surface modification of the Fe₃O₄ nanoparticles reveals that upon injection into a microchannel, the lipophilicity of the OA coating influences the movement of the nanoparticles across an oil-phase barrier. The motion of the nanoparticles is controlled using an AC magnetic field to induce magnetic torque and a static gradient field to control linear translation. The fat microablation process in a microchannel is demonstrated using an oscillating driving field of less than 1200 Am⁻¹. Full article

(This article belongs to the Special Issue Selected Papers from ICETI2014)

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16 pages, 1718 KiB

Open AccessFeature PaperReview

Extrinsic Contribution and Instability Properties in Lead-Based and Lead-Free Piezoceramics

by José Eduardo García

Materials 2015, 8(11), 7821-7836; https://doi.org/10.3390/ma8115426 - 19 Nov 2015

Cited by 12 | Viewed by 6069

Abstract

Piezoceramic materials generally exhibit a notable instability of their functional properties when they work under real external conditions. This undesirable effect, known as nonlinear behavior, is mostly associated with the extrinsic contribution to material response. In this article, the role of the ferroelectric [...] Read more.

Piezoceramic materials generally exhibit a notable instability of their functional properties when they work under real external conditions. This undesirable effect, known as nonlinear behavior, is mostly associated with the extrinsic contribution to material response. In this article, the role of the ferroelectric domain walls’ motion in the nonlinear response in the most workable lead-based and lead-free piezoceramics is reviewed. Initially, the extrinsic origin of the nonlinear response is discussed in terms of the temperature dependence of material response. The influence of the crystallographic phase and of the phase boundaries on the material response are then reviewed. Subsequently, the impact of the defects created by doping in order to control the extrinsic contribution is discussed as a way of tuning material properties. Finally, some aspects related to the grain-size effect on the nonlinear response of piezoceramics are surveyed. Full article

(This article belongs to the Special Issue Piezoelectric Materials)

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27 pages, 5769 KiB

Open AccessArticle

Characterization of Thermo-Physical Properties of EVA/ATH: Application to Gasification Experiments and Pyrolysis Modeling

by Bertrand Girardin, Gaëlle Fontaine, Sophie Duquesne, Michael Försth and Serge Bourbigot

Materials 2015, 8(11), 7837-7863; https://doi.org/10.3390/ma8115428 - 20 Nov 2015

Cited by 30 | Viewed by 7823

Abstract

The pyrolysis of solid polymeric materials is a complex process that involves both chemical and physical phenomena such as phase transitions, chemical reactions, heat transfer, and mass transport of gaseous components. For modeling purposes, it is important to characterize and to quantify the [...] Read more.

The pyrolysis of solid polymeric materials is a complex process that involves both chemical and physical phenomena such as phase transitions, chemical reactions, heat transfer, and mass transport of gaseous components. For modeling purposes, it is important to characterize and to quantify the properties driving those phenomena, especially in the case of flame-retarded materials. In this study, protocols have been developed to characterize the thermal conductivity and the heat capacity of an ethylene-vinyl acetate copolymer (EVA) flame retarded with aluminum tri-hydroxide (ATH). These properties were measured for the various species identified across the decomposition of the material. Namely, the thermal conductivity was found to decrease as a function of temperature before decomposition whereas the ceramic residue obtained after the decomposition at the steady state exhibits a thermal conductivity as low as 0.2 W/m/K. The heat capacity of the material was also investigated using both isothermal modulated Differential Scanning Calorimetry (DSC) and the standard method (ASTM E1269). It was shown that the final residue exhibits a similar behavior to alumina, which is consistent with the decomposition pathway of EVA/ATH. Besides, the two experimental approaches give similar results over the whole range of temperatures. Moreover, the optical properties before decomposition and the heat capacity of the decomposition gases were also analyzed. Those properties were then used as input data for a pyrolysis model in order to predict gasification experiments. Mass losses of gasification experiments were well predicted, thus validating the characterization of the thermo-physical properties of the material. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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9 pages, 6795 KiB

Open AccessArticle

Hydrogenation Properties of TiFe Doped with Zirconium

by Catherine Gosselin and Jacques Huot

Materials 2015, 8(11), 7864-7872; https://doi.org/10.3390/ma8115423 - 20 Nov 2015

Cited by 42 | Viewed by 6021

Abstract

The goal of this study was to optimize the activation behaviour of hydrogen storage alloy TiFe. We found that the addition of a small amount of Zr in TiFe alloy greatly reduces the hydrogenation activation time. Two different procedural synthesis methods were applied: [...] Read more.

The goal of this study was to optimize the activation behaviour of hydrogen storage alloy TiFe. We found that the addition of a small amount of Zr in TiFe alloy greatly reduces the hydrogenation activation time. Two different procedural synthesis methods were applied: co-melt, where the TiFe was melted and afterward re-melted with the addition of Zr, and single-melt, where Ti, Fe and Zr were melted together in one single operation. The co-melted sample absorbed hydrogen at its maximum capacity in less than three hours without any pre-treatment. The single-melted alloy absorbed its maximum capacity in less than seven hours, also without pre-treatment. The reason for discrepancies between co-melt and single-melt alloys was found to be the different microstructure. The effect of air exposure was also investigated. We found that the air-exposed samples had the same maximum capacity as the argon protected samples but with a slightly longer incubation time, which is probably due to the presence of a dense surface oxide layer. Scanning electron microscopy revealed the presence of a rich Zr intergranular phase in the TiFe matrix, which is responsible for the enhanced hydrogenation properties of these Zr-doped TiFe alloys. Full article

(This article belongs to the Special Issue Hydrogen Storage Materials)

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16 pages, 9971 KiB

Open AccessArticle

Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy

by Derek G. Gray and Xiaoyue Mu

Materials 2015, 8(11), 7873-7888; https://doi.org/10.3390/ma8115427 - 18 Nov 2015

Cited by 98 | Viewed by 13484

Abstract

Cellulosic liquid crystalline solutions and suspensions form chiral nematic phases that show a rich variety of optical textures in the liquid crystalline state. These ordered structures may be preserved in solid films prepared by evaporation of solvent or suspending medium. Film formation from [...] Read more.

Cellulosic liquid crystalline solutions and suspensions form chiral nematic phases that show a rich variety of optical textures in the liquid crystalline state. These ordered structures may be preserved in solid films prepared by evaporation of solvent or suspending medium. Film formation from aqueous suspensions of cellulose nanocrystals (CNC) was investigated by polarized light microscopy, optical profilometry and atomic force microscopy (AFM). An attempt is made to interpret qualitatively the observed textures in terms of the orientation of the cellulose nanocrystals in the suspensions and films, and the changes in orientation caused by the evaporative process. Mass transfer within the evaporating droplet resulted in the formation of raised rings whose magnitude depended on the degree of pinning of the receding contact line. AFM of dry films at short length scales showed a radial orientation of the CNC at the free surface of the film, along with a radial height variation with a period of approximately P/2, ascribed to the anisotropic shrinkage of the chiral nematic structure. Full article

(This article belongs to the Section Biomaterials)

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11 pages, 8946 KiB

Open AccessArticle

A Direct Electric Field-Aided Biomimetic Mineralization System for Inducing the Remineralization of Dentin Collagen Matrix

by Xiao-Ting Wu, May Lei Mei, Quan-Li Li, Chris Ying Cao, Jia-Long Chen, Rong Xia, Zhi-Hong Zhang and Chun Hung Chu

Materials 2015, 8(11), 7889-7899; https://doi.org/10.3390/ma8115433 - 20 Nov 2015

Cited by 25 | Viewed by 8783

Abstract

This in vitro study aimed to accelerate the remineralization of a completely demineralized dentine collagen block in order to regenerate the dentinal microstructure of calcified collagen fibrils by a novel electric field-aided biomimetic mineralization system in the absence of non-collagenous proteins. Completely demineralized [...] Read more.

This in vitro study aimed to accelerate the remineralization of a completely demineralized dentine collagen block in order to regenerate the dentinal microstructure of calcified collagen fibrils by a novel electric field-aided biomimetic mineralization system in the absence of non-collagenous proteins. Completely demineralized human dentine slices were prepared using ethylene diamine tetraacetic acid (EDTA) and treated with guanidine hydrochloride to extract the bound non-collagenous proteins. The completely demineralized dentine collagen blocks were then remineralized in a calcium chloride agarose hydrogel and a sodium hydrogen phosphate and fluoride agarose hydrogel. This process was accelerated by subjecting the hydrogels to electrophoresis at 20 mA for 4 and 12 h. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) were used to evaluate the resultant calcification of the dentin collagen matrix. SEM indicated that mineral particles were precipitated on the intertubular dentin collagen matrix; these densely packed crystals mimicked the structure of the original mineralized dentin. However, the dentinal tubules were not occluded by the mineral crystals. XRD and EDX both confirmed that the deposited crystals were fluorinated hydroxyapatite. TEM revealed the existence of intrafibrillar and interfibrillar mineralization of the collagen fibrils. A novel electric field-aided biomimetic mineralization system was successfully developed to remineralize a completely demineralized dentine collagen matrix in the absence of non-collagenous proteins. This study developed an accelerated biomimetic mineralization system which can be a potential protocol for the biomineralization of dentinal defects. Full article

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13 pages, 3615 KiB

Open AccessArticle

Ultrasound-Assist Extrusion Methods for the Fabrication of Polymer Nanocomposites Based on Polypropylene/Multi-Wall Carbon Nanotubes

by Carlos A. Ávila-Orta, Zoe V. Quiñones-Jurado, Miguel A. Waldo-Mendoza, Erika A. Rivera-Paz, Víctor J. Cruz-Delgado, José M. Mata-Padilla, Pablo González-Morones and Ronald F. Ziolo

Materials 2015, 8(11), 7900-7912; https://doi.org/10.3390/ma8115431 - 23 Nov 2015

Cited by 20 | Viewed by 6642

Abstract

Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the [...] Read more.

Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the NCs. Three different types of iPPs were used with MFIs of 2.5, 34 and 1200 g/10 min. Four different NC fabrication methods based on melt extrusion were used. In the first method melt extrusion fabrication without ultrasound assistance was used. In the second and third methods, an ultrasound probe attached to a hot chamber located at the exit of the die was used to subject the sample to fixed frequency and variable frequency, respectively. The fourth method is similar to the first method, with the difference being that the carbon nanotubes were treated in a fluidized air-bed with an ultrasound probe before being used in the fabrication of the NCs with no ultrasound assistance during extrusion. The samples were characterized by MFI, Optical microscopy (OM), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), electrical surface resistivity, and electric charge. MFI decreases in all cases with addition of MWCNTs with the largest decrease observed for samples with the highest MFI. The surface resistivity, which ranged from 10¹³ to 10⁵ Ω/sq, and electric charge, were observed to depend on the ultrasound-assisted fabrication method as well as on the melt flow index of the iPP. A relationship between agglomerate size and area ratio with electric charge was found. Several trends in the overall data were identified and are discussed in terms of MFI and the different fabrication methods. Full article

(This article belongs to the Special Issue Polymer Nanocomposites)

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13 pages, 2154 KiB

Open AccessReview

Mechanisms of in Vivo Degradation and Resorption of Calcium Phosphate Based Biomaterials

by Zeeshan Sheikh, Mohamed-Nur Abdallah, Ahmed Abdalla Hanafi, Syed Misbahuddin, Haroon Rashid and Michael Glogauer

Materials 2015, 8(11), 7913-7925; https://doi.org/10.3390/ma8115430 - 23 Nov 2015

Cited by 194 | Viewed by 14492

Abstract

Calcium phosphate ceramic materials are extensively used for bone replacement and regeneration in orthopedic, dental, and maxillofacial surgical applications. In order for these biomaterials to work effectively it is imperative that they undergo the process of degradation and resorption in vivo. This [...] Read more.

Calcium phosphate ceramic materials are extensively used for bone replacement and regeneration in orthopedic, dental, and maxillofacial surgical applications. In order for these biomaterials to work effectively it is imperative that they undergo the process of degradation and resorption in vivo. This allows for the space to be created for the new bone tissue to form and infiltrate within the implanted graft material. Several factors affect the biodegradation and resorption of calcium phosphate materials after implantation. Various cell types are involved in the degradation process by phagocytic mechanisms (monocytes/macrophages, fibroblasts, osteoblasts) or via an acidic mechanism to reduce the micro-environmental pH which results in demineralization of the cement matrix and resorption via osteoclasts. These cells exert their degradation effects directly or indirectly through the cytokine growth factor secretion and their sensitivity and response to these biomolecules. This article discusses the mechanisms of calcium phosphate material degradation in vivo. Full article

(This article belongs to the Special Issue Regenerative Materials)

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12 pages, 4153 KiB

Open AccessArticle

Compressive Behavior and Microstructural Characteristics of Iron Hollow Sphere Filled Aluminum Matrix Syntactic Foams

by Attila Szlancsik, Bálint Katona, Kornél Májlinger and Imre Norbert Orbulov

Materials 2015, 8(11), 7926-7937; https://doi.org/10.3390/ma8115432 - 23 Nov 2015

Cited by 44 | Viewed by 7413

Abstract

Iron hollow sphere filled aluminum matrix syntactic foams (AMSFs) were produced by low pressure, inert gas assisted infiltration. The microstructure of the produced AMSFs was investigated by light and electron microscopy, extended by energy dispersive X-ray spectroscopy and electron back-scattered diffraction. The investigations [...] Read more.

Iron hollow sphere filled aluminum matrix syntactic foams (AMSFs) were produced by low pressure, inert gas assisted infiltration. The microstructure of the produced AMSFs was investigated by light and electron microscopy, extended by energy dispersive X-ray spectroscopy and electron back-scattered diffraction. The investigations revealed almost perfect infiltration and a slight gradient in the grain size of the matrix. A very thin interface layer that ensures good bonding between the hollow spheres and the matrix was also observed. Compression tests were performed on cylindrical specimens to explore the characteristic mechanical properties of the AMSFs. Compared to other (conventional) metallic foams, the investigated AMSFs proved to have outstanding mechanical properties (yield strength, plateau strength, etc.) and energy absorbing capability. Full article

(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)

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24 pages, 10491 KiB

Open AccessReview

Fiber-Embedded Metallic Materials: From Sensing towards Nervous Behavior

by Nouari Saheb and Samir Mekid

Materials 2015, 8(11), 7938-7961; https://doi.org/10.3390/ma8115435 - 24 Nov 2015

Cited by 36 | Viewed by 8462

Abstract

Embedding of fibers in materials has attracted serious attention from researchers and has become a new research trend. Such material structures are usually termed “smart” or more recently “nervous”. Materials can have the capability of sensing and responding to the surrounding environmental stimulus, [...] Read more.

Embedding of fibers in materials has attracted serious attention from researchers and has become a new research trend. Such material structures are usually termed “smart” or more recently “nervous”. Materials can have the capability of sensing and responding to the surrounding environmental stimulus, in the former, and the capability of feeling multiple structural and external stimuli, while feeding information back to a controller for appropriate real-time action, in the latter. In this paper, embeddable fibers, embedding processes, and behavior of fiber-embedded metallic materials are reviewed. Particular emphasis has been given to embedding fiber Bragg grating (FBG) array sensors and piezo wires, because of their high potential to be used in nervous materials for structural health monitoring. Ultrasonic consolidation and laser-based layered manufacturing processes are discussed in detail because of their high potential to integrate fibers without disruption. In addition, current challenges associated with embedding fibers in metallic materials are highlighted and recommendations for future research work are set. Full article

(This article belongs to the Special Issue Bioinspired and Biomimetic Materials)

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17 pages, 4796 KiB

Open AccessFeature PaperArticle

Growth and Characterization of Lead-free Piezoelectric Single Crystals

by Philippe Veber, Feres Benabdallah, Hairui Liu, Gabriel Buse, Michael Josse and Mario Maglione

Materials 2015, 8(11), 7962-7978; https://doi.org/10.3390/ma8115436 - 24 Nov 2015

Cited by 14 | Viewed by 6852

Abstract

Lead-free piezoelectric materials attract more and more attention owing to the environmental toxicity of lead-containing materials. In this work, we review our first attempts of single crystal grown by the top-seeded solution growth method of BaTiO₃ substituted with zirconium and calcium (BCTZ) [...] Read more.

Lead-free piezoelectric materials attract more and more attention owing to the environmental toxicity of lead-containing materials. In this work, we review our first attempts of single crystal grown by the top-seeded solution growth method of BaTiO₃ substituted with zirconium and calcium (BCTZ) and (K_0.5Na_0.5)NbO₃ substituted with lithium, tantalum, and antimony (KNLSTN). The growth methodology is optimized in order to reach the best compositions where enhanced properties are expected. Chemical analysis and electrical characterizations are presented for both kinds of crystals. The compositionally-dependent electrical performance is investigated for a better understanding of the relationship between the composition and electrical properties. A cross-over from relaxor to ferroelectric state in BCTZ solid solution is evidenced similar to the one reported in ceramics. In KNLSTN single crystals, we observed a substantial evolution of the orthorhombic-to-tetragonal phase transition under minute composition changes. Full article

(This article belongs to the Special Issue Piezoelectric Materials)

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9 pages, 4952 KiB

Open AccessArticle

Preparation of Cotton-Wool-Like Poly(lactic acid)-Based Composites Consisting of Core-Shell-Type Fibers

by Jian Wang, Pin Zhou, Akiko Obata, Julian R. Jones and Toshihiro Kasuga

Materials 2015, 8(11), 7979-7987; https://doi.org/10.3390/ma8115434 - 24 Nov 2015

Cited by 5 | Viewed by 8501

Abstract

In previous works, we reported the fabrication of cotton-wool-like composites consisting of siloxane-doped vaterite and poly(l-lactic acid) (SiVPCs). Various irregularly shaped bone voids can be filled with the composite, which effectively supplies calcium and silicate ions, enhancing the bone formation by stimulating the [...] Read more.

In previous works, we reported the fabrication of cotton-wool-like composites consisting of siloxane-doped vaterite and poly(l-lactic acid) (SiVPCs). Various irregularly shaped bone voids can be filled with the composite, which effectively supplies calcium and silicate ions, enhancing the bone formation by stimulating the cells. The composites, however, were brittle and showed an initial burst release of ions. In the present work, to improve the mechanical flexibility and ion release, the composite fiber was coated with a soft, thin layer consisting of poly(d,l-lactic-co-glycolic acid) (PLGA). A coaxial electrospinning technique was used to prepare a cotton-wool-like material comprising “core-shell”-type fibers with a diameter of ~12 µm. The fibers, which consisted of SiVPC coated with a ~2-µm-thick PLGA layer, were mechanically flexible; even under a uniaxial compressive load of 1.5 kPa, the cotton-wool-like material did not exhibit fracture of the fibers and, after removing the load, showed a ~60% recovery. In Tris buffer solution, the initial burst release of calcium and silicate ions from the “core-shell”-type fibers was effectively controlled, and the ions were slowly released after one day. Thus, the mechanical flexibility and ion-release behavior of the composites were drastically improved by the thin PLGA coating. Full article

(This article belongs to the Section Advanced Composites)

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Materials, Volume 8, Issue 11 (November 2015) – 61 articles

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