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Materials, Volume 9, Issue 9 (September 2016)

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Cover Story (view full-size image) The relatively limited number of efficient energy conversion materials has driven many scientists [...] Read more.
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Open AccessArticle Highly Absorbent Antibacterial Hemostatic Dressing for Healing Severe Hemorrhagic Wounds
Materials 2016, 9(9), 793; https://doi.org/10.3390/ma9090793
Received: 7 June 2016 / Revised: 28 July 2016 / Accepted: 9 September 2016 / Published: 21 September 2016
Cited by 4 | Viewed by 2047 | PDF Full-text (3689 KB) | HTML Full-text | XML Full-text
Abstract
To accelerate healing of severe hemorrhagic wounds, a novel highly absorbent hemostatic dressing composed of a Tencel®/absorbent-cotton/polylactic acid nonwoven base and chitosan/nanosilver antibacterial agent was fabricated by using a nonwoven processing technique and a freeze-drying technique. This study is the first [...] Read more.
To accelerate healing of severe hemorrhagic wounds, a novel highly absorbent hemostatic dressing composed of a Tencel®/absorbent-cotton/polylactic acid nonwoven base and chitosan/nanosilver antibacterial agent was fabricated by using a nonwoven processing technique and a freeze-drying technique. This study is the first to investigate the wicking and water-absorbing properties of a nonwoven base by measuring the vertical wicking height and water absorption ratio. Moreover, blood agglutination and hemostatic second tests were conducted to evaluate the hemostatic performance of the resultant wound dressing. The blending ratio of fibers, areal weight, punching density, and fiber orientation, all significantly influenced the vertical moisture wicking property. However, only the first two parameters markedly affected the water absorption ratio. After the nonwoven base absorbed blood, scanning electron microscope (SEM) observation showed that erythrocytes were trapped between the fibrin/clot network and nonwoven fibers when coagulation pathways were activated. Prothrombin time (PT) and activated partial thromboplastin time (APTT) blood agglutination of the resultant dressing decreased to 14.34 and 50.94 s, respectively. In the femoral artery of the rate bleeding model, hemostatic time was saved by 87.2% compared with that of cotton cloth. Therefore, the resultant antibacterial wound dressing demonstrated greater water and blood absorption, as well as hemostatic performance, than the commercially available cotton cloth, especially for healing severe hemorrhagic wounds. Full article
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Open AccessArticle The Effect of 4-Octyldecyloxybenzoic Acid on Liquid-Crystalline Polyurethane Composites with Triple-Shape Memory and Self-Healing Properties
Materials 2016, 9(9), 792; https://doi.org/10.3390/ma9090792
Received: 16 August 2016 / Revised: 8 September 2016 / Accepted: 12 September 2016 / Published: 21 September 2016
Cited by 3 | Viewed by 1937 | PDF Full-text (10122 KB) | HTML Full-text | XML Full-text
Abstract
To better understand shape memory materials and self-healing materials, a new series of liquid-crystalline shape memory polyurethane (LC-SMPU) composites, named SMPU-OOBAm, were successfully prepared by incorporating 4-octyldecyloxybenzoic acid (OOBA) into the PEG-based SMPU. The effect of OOBA on the structure, morphology, and properties [...] Read more.
To better understand shape memory materials and self-healing materials, a new series of liquid-crystalline shape memory polyurethane (LC-SMPU) composites, named SMPU-OOBAm, were successfully prepared by incorporating 4-octyldecyloxybenzoic acid (OOBA) into the PEG-based SMPU. The effect of OOBA on the structure, morphology, and properties of the material has been carefully investigated. The results demonstrate that SMPU-OOBAm has liquid crystalline properties, triple-shape memory properties, and self-healing properties. The incorporated OOBA promotes the crystallizability of both soft and hard segments of SMPU, and the crystallization rate of the hard segment of SMPU decreases when the OOBA-content increases. Additionally, the SMPU-OOBAm forms a two-phase separated structure (SMPU phase and OOBA phase), and it shows two-step modulus changes upon heating. Therefore, the SMPU-OOBAm exhibits triple-shape memory behavior, and the shape recovery ratio decreases with an increase in the OOBA content. Finally, SMPU-OOBAm exhibits self-healing properties. The new mechanism can be ascribed to the heating-induced “bleeding” of OOBA in the liquid crystalline state and the subsequent re-crystallization upon cooling. This successful combination of liquid crystalline properties, triple-shape memory properties, and self-healing properties make the SMPU-OOBAm composites ideal for many promising applications in smart optical devices, smart electronic devices, and smart sensors. Full article
(This article belongs to the Section Advanced Composites)
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Open AccessArticle Pickering Particles Prepared from Food Waste
Materials 2016, 9(9), 791; https://doi.org/10.3390/ma9090791
Received: 9 August 2016 / Revised: 12 September 2016 / Accepted: 14 September 2016 / Published: 21 September 2016
Cited by 6 | Viewed by 2184 | PDF Full-text (5681 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we demonstrate the functionality and functionalisation of waste particles as an emulsifier for oil-in-water (o/w) and water-in-oil (w/o) emulsions. Ground coffee waste was chosen as a candidate waste material due to its naturally high content of lignin, a chemical component [...] Read more.
In this paper, we demonstrate the functionality and functionalisation of waste particles as an emulsifier for oil-in-water (o/w) and water-in-oil (w/o) emulsions. Ground coffee waste was chosen as a candidate waste material due to its naturally high content of lignin, a chemical component imparting emulsifying ability. The waste coffee particles readily stabilised o/w emulsions and following hydrothermal treatment adapted from the bioenergy field they also stabilised w/o emulsions. The hydrothermal treatment relocated the lignin component of the cell walls within the coffee particles onto the particle surface thereby increasing the surface hydrophobicity of the particles as demonstrated by an emulsion assay. Emulsion droplet sizes were comparable to those found in processed foods in the case of hydrophilic waste coffee particles stabilizing o/w emulsions. These emulsions were stable against coalescence for at least 12 weeks, flocculated but stable against coalescence in shear and stable to pasteurisation conditions (10 min at 80 °C). Emulsion droplet size was also insensitive to pH of the aqueous phase during preparation (pH 3–pH 9). Stable against coalescence, the water droplets in w/o emulsions prepared with hydrothermally treated waste coffee particles were considerably larger and microscopic examination showed evidence of arrested coalescence indicative of particle jamming at the surface of the emulsion droplets. Refinement of the hydrothermal treatment and broadening out to other lignin-rich plant or plant based food waste material are promising routes to bring closer the development of commercially relevant lignin based food Pickering particles applicable to emulsion based processed foods ranging from fat continuous spreads and fillings to salad dressings. Full article
(This article belongs to the Special Issue Pickering Emulsion and Derived Materials) Printed Edition available
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Open AccessArticle A Multi-Level Decision Fusion Strategy for Condition Based Maintenance of Composite Structures
Materials 2016, 9(9), 790; https://doi.org/10.3390/ma9090790
Received: 11 August 2016 / Revised: 5 September 2016 / Accepted: 13 September 2016 / Published: 21 September 2016
Cited by 12 | Viewed by 1673 | PDF Full-text (5656 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a multi-level decision fusion strategy is proposed which weighs the Value of Information (VoI) against the intended functions of a Structural Health Monitoring (SHM) system. This paper presents a multi-level approach for three different maintenance strategies in which the performance [...] Read more.
In this work, a multi-level decision fusion strategy is proposed which weighs the Value of Information (VoI) against the intended functions of a Structural Health Monitoring (SHM) system. This paper presents a multi-level approach for three different maintenance strategies in which the performance of the SHM systems is evaluated against its intended functions. Level 1 diagnosis results in damage existence with minimum sensors covering a large area by finding the maximum energy difference for the guided waves propagating in pristine structure and the post-impact state; Level 2 diagnosis provides damage detection and approximate localization using an approach based on Electro-Mechanical Impedance (EMI) measures, while Level 3 characterizes damage (exact location and size) in addition to its detection by utilising a Weighted Energy Arrival Method (WEAM). The proposed multi-level strategy is verified and validated experimentally by detection of Barely Visible Impact Damage (BVID) on a curved composite fuselage panel. Full article
(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)
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Open AccessArticle Photocatalytic, Antimicrobial and Biocompatibility Features of Cotton Knit Coated with Fe-N-Doped Titanium Dioxide Nanoparticles
Materials 2016, 9(9), 789; https://doi.org/10.3390/ma9090789
Received: 1 August 2016 / Revised: 29 August 2016 / Accepted: 1 September 2016 / Published: 21 September 2016
Cited by 9 | Viewed by 2082 | PDF Full-text (3664 KB) | HTML Full-text | XML Full-text
Abstract
Our research was focused on the evaluation of the photocatalytic and antimicrobial properties, as well as biocompatibility of cotton fabrics coated with fresh and reused dispersions of nanoscaled TiO2-1% Fe-N particles prepared by the hydrothermal method and post-annealed at 400 °C. [...] Read more.
Our research was focused on the evaluation of the photocatalytic and antimicrobial properties, as well as biocompatibility of cotton fabrics coated with fresh and reused dispersions of nanoscaled TiO2-1% Fe-N particles prepared by the hydrothermal method and post-annealed at 400 °C. The powders were characterized by X-ray diffraction (XRD), Mössbauer spectroscopy and X-ray photoelectron spectroscopy. The textiles coated with doped TiO2 were characterized by scanning electron microscopy and energy dispersive X-ray analyses, and their photocatalytic effect by trichromatic coordinates of the materials stained with methylene blue and coffee and exposed to UV, visible and solar light. The resulting doped TiO2 consists of a mixture of prevailing anatase phase and a small amount (~15%–20%) of brookite, containing Fe3+ and nitrogen. By reusing dispersions of TiO2-1% Fe-N, high amounts of photocatalysts were deposited on the fabrics, and the photocatalytic activity was improved, especially under visible light. The treated fabrics exhibited specific antimicrobial features, which were dependent on their composition, microbial strain and incubation time. The in vitro biocompatibility evaluation on CCD-1070Sk dermal fibroblasts confirmed the absence of cytotoxicity after short-term exposure. These results highlight the potential of TiO2-1% Fe-N nanoparticles for further use in the development of innovative self-cleaning and antimicrobial photocatalytic cotton textiles. However, further studies are required in order to assess the long-term skin exposure effects and the possible particle release due to wearing. Full article
(This article belongs to the Special Issue Materials for Hard and Soft Tissue Engineering: Novel Approaches)
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Open AccessArticle Characteristics of Ceramic Fiber Modified Asphalt Mortar
Materials 2016, 9(9), 788; https://doi.org/10.3390/ma9090788
Received: 5 June 2016 / Revised: 16 August 2016 / Accepted: 12 September 2016 / Published: 21 September 2016
Cited by 4 | Viewed by 2098 | PDF Full-text (4263 KB) | HTML Full-text | XML Full-text
Abstract
Ceramic fiber, with a major composition of Al2O3 and SiO2, has advantages of stability at relatively high temperature, big specific surface area and resistance to external mechanical vibration. It has the potential contribution of improving the rutting resistance [...] Read more.
Ceramic fiber, with a major composition of Al2O3 and SiO2, has advantages of stability at relatively high temperature, big specific surface area and resistance to external mechanical vibration. It has the potential contribution of improving the rutting resistance and temperature sensitivity of modified asphalt binder by proper modification design. In this research, ceramic fiber was introduced into both pen 60/80 and pen 80/100 asphalt binder by different weight ratios. An asphalt penetration test, softening point test, ductility test and dynamic viscoelastic behavior were conducted to characterize and predict the ceramic fiber modified asphalt mortar (CFAM). Research results indicated that the ceramic fiber has a great effect on reinforcement of asphalt, which makes the asphalt stiffer so that the asphalt can only undertake less strain under the same stress. The heat insulation effect of the ceramic fiber will improve the temperature stability. Complex modulus and phase angle results indicate that the ceramic fiber can significantly enhance the high temperature resistance of soft binder. Full article
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Open AccessArticle Imperfection Sensitivity of Nonlinear Vibration of Curved Single-Walled Carbon Nanotubes Based on Nonlocal Timoshenko Beam Theory
Materials 2016, 9(9), 786; https://doi.org/10.3390/ma9090786
Received: 2 August 2016 / Revised: 29 August 2016 / Accepted: 6 September 2016 / Published: 21 September 2016
Cited by 2 | Viewed by 1768 | PDF Full-text (6575 KB) | HTML Full-text | XML Full-text
Abstract
Imperfection sensitivity of large amplitude vibration of curved single-walled carbon nanotubes (SWCNTs) is considered in this study. The SWCNT is modeled as a Timoshenko nano-beam and its curved shape is included as an initial geometric imperfection term in the displacement field. Geometric nonlinearities [...] Read more.
Imperfection sensitivity of large amplitude vibration of curved single-walled carbon nanotubes (SWCNTs) is considered in this study. The SWCNT is modeled as a Timoshenko nano-beam and its curved shape is included as an initial geometric imperfection term in the displacement field. Geometric nonlinearities of von Kármán type and nonlocal elasticity theory of Eringen are employed to derive governing equations of motion. Spatial discretization of governing equations and associated boundary conditions is performed using differential quadrature (DQ) method and the corresponding nonlinear eigenvalue problem is iteratively solved. Effects of amplitude and location of the geometric imperfection, and the nonlocal small-scale parameter on the nonlinear frequency for various boundary conditions are investigated. The results show that the geometric imperfection and non-locality play a significant role in the nonlinear vibration characteristics of curved SWCNTs. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Elastic Modulus of the Alkali-Silica Reaction Rim in a Simplified Calcium-Alkali-Silicate System Determined by Nano-Indentation
Materials 2016, 9(9), 787; https://doi.org/10.3390/ma9090787
Received: 26 July 2016 / Revised: 31 August 2016 / Accepted: 12 September 2016 / Published: 20 September 2016
Cited by 4 | Viewed by 1687 | PDF Full-text (6229 KB) | HTML Full-text | XML Full-text
Abstract
This work aims at providing a better understanding of the mechanical properties of the reaction rim in the alkali-silica reaction. The elastic modulus of the calcium alkali silicate constituting the reaction rim, which is formed at the interface between alkali silicate and Ca(OH) [...] Read more.
This work aims at providing a better understanding of the mechanical properties of the reaction rim in the alkali-silica reaction. The elastic modulus of the calcium alkali silicate constituting the reaction rim, which is formed at the interface between alkali silicate and Ca(OH)2 in a chemically-idealized system of the alkali-silica reaction, was studied using nano-indentation. In addition, the corresponding calcium to silica mole ratio of the calcium alkali silicate was investigated. The results show that the elastic modulus of the calcium alkali silicate formed at the interface increased with the increase of the calcium to silica mole ratio and vice versa. Furthermore, the more calcium that was available for interaction with alkali silicate to form calcium alkali silicate, the higher the calcium to silica mole ratio and, consequently, the higher the elastic modulus of the formed calcium alkali silicate. This work provides illustrative evidence from a mechanical point of view on how the occurrence of cracks due to the alkali-silica reaction (ASR) is linked to the formation of the reaction rim. It has to be highlighted, however, that the simplified calcium-alkali-silicate system in this study is far from the real condition in concrete. Full article
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Open AccessArticle Novel Resorbable and Osteoconductive Calcium Silicophosphate Scaffold Induced Bone Formation
Materials 2016, 9(9), 785; https://doi.org/10.3390/ma9090785
Received: 25 July 2016 / Revised: 6 September 2016 / Accepted: 12 September 2016 / Published: 20 September 2016
Cited by 11 | Viewed by 1623 | PDF Full-text (11470 KB) | HTML Full-text | XML Full-text
Abstract
This aim of this research was to develop a novel ceramic scaffold to evaluate the response of bone after ceramic implantation in New Zealand (NZ) rabbits. Ceramics were prepared by the polymer replication method and inserted into NZ rabbits. Macroporous scaffolds with interconnected [...] Read more.
This aim of this research was to develop a novel ceramic scaffold to evaluate the response of bone after ceramic implantation in New Zealand (NZ) rabbits. Ceramics were prepared by the polymer replication method and inserted into NZ rabbits. Macroporous scaffolds with interconnected round-shaped pores (0.5–1.5 mm = were prepared). The scaffold acted as a physical support where cells with osteoblastic capability were found to migrate, develop processes, and newly immature and mature bone tissue colonized on the surface (initially) and in the material’s interior. The new ceramic induced about 62.18% ± 2.28% of new bone and almost complete degradation after six healing months. An elemental analysis showed that the gradual diffusion of Ca and Si ions from scaffolds into newly formed bone formed part of the biomaterial’s resorption process. Histological and radiological studies demonstrated that this porous ceramic scaffold showed biocompatibility and excellent osteointegration and osteoinductive capacity, with no interposition of fibrous tissue between the implanted material and the hematopoietic bone marrow interphase, nor any immune response after six months of implantation. No histological changes were observed in the various organs studied (para-aortic lymph nodes, liver, kidney and lung) as a result of degradation products being released. Full article
(This article belongs to the Special Issue Smart Biomaterials and Biointerfaces)
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Open AccessCorrection Correction: Ono, K. Calibration Methods of Acoustic Emission Sensors. Materials 2016, 9, 508
Materials 2016, 9(9), 784; https://doi.org/10.3390/ma9090784
Received: 10 September 2016 / Revised: 13 September 2016 / Accepted: 13 September 2016 / Published: 20 September 2016
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Abstract
The author wishes to make the following corrections to this paper [1].[...] Full article
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Open AccessArticle Simple Synthesis of Molybdenum Disulfide/Reduced Graphene Oxide Composite Hollow Microspheres as Supercapacitor Electrode Material
Materials 2016, 9(9), 783; https://doi.org/10.3390/ma9090783
Received: 22 August 2016 / Revised: 8 September 2016 / Accepted: 12 September 2016 / Published: 20 September 2016
Cited by 18 | Viewed by 2865 | PDF Full-text (3086 KB) | HTML Full-text | XML Full-text
Abstract
MoS2/RGO composite hollow microspheres were hydrothermally synthesized by using SiO2/GO microspheres as a template, which were obtained via the sonication-assisted interfacial self-assembly of tiny GO sheets on positively charged SiO2 microspheres. The structure, morphology, phase, and chemical composition [...] Read more.
MoS2/RGO composite hollow microspheres were hydrothermally synthesized by using SiO2/GO microspheres as a template, which were obtained via the sonication-assisted interfacial self-assembly of tiny GO sheets on positively charged SiO2 microspheres. The structure, morphology, phase, and chemical composition of MoS2/RGO hollow microspheres were systematically investigated by a series of techniques such as FE-SEM, TEM, XRD, TGA, BET, and Raman characterizations, meanwhile, their electrochemical properties were carefully evaluated by CV, GCD, and EIS measurements. It was found that MoS2/RGO hollow microspheres possessed unique porous hollow architecture with high-level hierarchy and large specific surface area up to 63.7 m2·g−1. When used as supercapacitor electrode material, MoS2/RGO hollow microspheres delivered a maximum specific capacitance of 218.1 F·g−1 at the current density of 1 A·g−1, which was much higher than that of contrastive bare MoS2 microspheres developed in the present work and most of other reported MoS2-based materials. The enhancement of supercapacitive behaviors of MoS2/RGO hollow microspheres was likely due to the improved conductivity together with their distinct structure and morphology, which not only promoted the charge transport but also facilitated the electrolyte diffusion. Moreover, MoS2/RGO hollow microsphere electrode displayed satisfactory long-term stability with 91.8% retention of the initial capacitance after 1000 charge/discharge cycles at the current density of 3 A·g−1, showing excellent application potential. Full article
(This article belongs to the Section Energy Materials)
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Open AccessArticle Deformation Behavior of Recycled Concrete Aggregate during Cyclic and Dynamic Loading Laboratory Tests
Materials 2016, 9(9), 780; https://doi.org/10.3390/ma9090780
Received: 29 July 2016 / Revised: 6 September 2016 / Accepted: 8 September 2016 / Published: 20 September 2016
Cited by 7 | Viewed by 1657 | PDF Full-text (5470 KB) | HTML Full-text | XML Full-text
Abstract
Recycled concrete aggregate (RCA) is a relatively new construction material, whose applications can replace natural aggregates. To do so, extensive studies on its mechanical behavior and deformation characteristics are still necessary. RCA is currently used as a subbase material in the construction of [...] Read more.
Recycled concrete aggregate (RCA) is a relatively new construction material, whose applications can replace natural aggregates. To do so, extensive studies on its mechanical behavior and deformation characteristics are still necessary. RCA is currently used as a subbase material in the construction of roads, which are subject to high settlements due to traffic loading. The deformation characteristics of RCA must, therefore, be established to find the possible fatigue and damage behavior for this new material. In this article, a series of triaxial cyclic loading and resonant column tests is used to characterize fatigue in RCA as a function of applied deviator stress after long-term cyclic loading. A description of the shakedown phenomenon occurring in the RCA and calculations of its resilient modulus (Mr) as a function of fatigue are also presented. Test result analysis with the stress-life method on the Wohler S-N diagram shows the RCA behavior in accordance with the Basquin law. Full article
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Open AccessArticle Three-Dimensional Network Model for Coupling of Fracture and Mass Transport in Quasi-Brittle Geomaterials
Materials 2016, 9(9), 782; https://doi.org/10.3390/ma9090782
Received: 9 August 2016 / Revised: 12 September 2016 / Accepted: 14 September 2016 / Published: 19 September 2016
Cited by 17 | Viewed by 2310 | PDF Full-text (1074 KB) | HTML Full-text | XML Full-text
Abstract
Dual three-dimensional networks of structural and transport elements were combined to model the effect of fracture on mass transport in quasi-brittle geomaterials. Element connectivity of the structural network, representing elasticity and fracture, was defined by the Delaunay tessellation of a random set of [...] Read more.
Dual three-dimensional networks of structural and transport elements were combined to model the effect of fracture on mass transport in quasi-brittle geomaterials. Element connectivity of the structural network, representing elasticity and fracture, was defined by the Delaunay tessellation of a random set of points. The connectivity of transport elements within the transport network was defined by the Voronoi tessellation of the same set of points. A new discretisation strategy for domain boundaries was developed to apply boundary conditions for the coupled analyses. The properties of transport elements were chosen to evolve with the crack opening values of neighbouring structural elements. Through benchmark comparisons involving non-stationary transport and fracture, the proposed dual network approach was shown to be objective with respect to element size and orientation. Full article
(This article belongs to the Special Issue Numerical Analysis of Concrete using Discrete Elements)
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Open AccessArticle Monitoring Poisson’s Ratio Degradation of FRP Composites under Fatigue Loading Using Biaxially Embedded FBG Sensors
Materials 2016, 9(9), 781; https://doi.org/10.3390/ma9090781
Received: 20 May 2016 / Revised: 27 August 2016 / Accepted: 3 September 2016 / Published: 19 September 2016
Cited by 3 | Viewed by 2046 | PDF Full-text (3865 KB) | HTML Full-text | XML Full-text
Abstract
The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to [...] Read more.
The significance of strain measurement is obvious for the analysis of Fiber-Reinforced Polymer (FRP) composites. Conventional strain measurement methods are sufficient for static testing in general. Nevertheless, if the requirements exceed the capabilities of these conventional methods, more sophisticated techniques are necessary to obtain strain data. Fiber Bragg Grating (FBG) sensors have many advantages for strain measurement over conventional ones. Thus, the present paper suggests a novel method for biaxial strain measurement using embedded FBG sensors during the fatigue testing of FRP composites. Poisson’s ratio and its reduction were monitored for each cyclic loading by using embedded FBG sensors for a given specimen and correlated with the fatigue stages determined based on the variations of the applied fatigue loading and temperature due to the autogenous heating to predict an oncoming failure of the continuous fiber-reinforced epoxy matrix composite specimens under fatigue loading. The results show that FBG sensor technology has a remarkable potential for monitoring the evolution of Poisson’s ratio on a cycle-by-cycle basis, which can reliably be used towards tracking the fatigue stages of composite for structural health monitoring purposes. Full article
(This article belongs to the Special Issue Advances in Structural Health Monitoring for Aerospace Structures)
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Open AccessArticle Multichromic Polymers Containing Alternating Bi(3-Methoxythiophene) and Triphenylamine Based Units with Para-Protective Substituents
Materials 2016, 9(9), 779; https://doi.org/10.3390/ma9090779
Received: 11 August 2016 / Revised: 7 September 2016 / Accepted: 12 September 2016 / Published: 19 September 2016
Cited by 3 | Viewed by 1832 | PDF Full-text (11394 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Two novel triphenylamine-based thiophene derivative monomers, 4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine and 4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine, were successfully synthesized. The corresponding polymers including poly (4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) and poly (4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) were electrochemically synthesized and characterized by multiple test method. The electrochemical measurements and spectroelectrochemical analyses revealed that both of the two polymers [...] Read more.
Two novel triphenylamine-based thiophene derivative monomers, 4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine and 4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine, were successfully synthesized. The corresponding polymers including poly (4-cyano-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) and poly (4-methoxy-4′,4″-di(4-methoxythiophen-2-yl)triphenylamine) were electrochemically synthesized and characterized by multiple test method. The electrochemical measurements and spectroelectrochemical analyses revealed that both of the two polymers had quasi-reversible redox behavior and multi-electrochromic properties. The two polymer films showed reversible electrochemical oxidation, excellent optical contrasts in NIR region (62% at 1070 nm for the first polymer, and 86% at 1255 nm for the second polymer), satisfactory coloration efficiencies and fast switching times. The research on the application of the as prepared polymer in the fabrication of electrochromic device was also conducted, employing PCMTPA or PMMTPA as the anodically coloring materials. Full article
(This article belongs to the Section Structure Analysis and Characterization)
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Open AccessArticle Evaluation of the Antimicrobial Activity of Different Antibiotics Enhanced with Silver-Doped Hydroxyapatite Thin Films
Materials 2016, 9(9), 778; https://doi.org/10.3390/ma9090778
Received: 4 August 2016 / Revised: 1 September 2016 / Accepted: 8 September 2016 / Published: 16 September 2016
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Abstract
The inhibitory and antimicrobial effects of silver particles have been known since ancient times. In the last few years, a major health problem has arisen due to pathogenic bacteria resistance to antimicrobial agents. The antibacterial activities of new materials including hydroxyapatite (HAp), silver-doped [...] Read more.
The inhibitory and antimicrobial effects of silver particles have been known since ancient times. In the last few years, a major health problem has arisen due to pathogenic bacteria resistance to antimicrobial agents. The antibacterial activities of new materials including hydroxyapatite (HAp), silver-doped hydroxyapatite (Ag:HAp) and various types of antibiotics such as tetracycline (T-HAp and T-Ag:HAp) or ciprofloxacin (C-HAp and C-Ag:HAp) have not been studied so far. In this study we reported, for the first time, the preparation and characterization of various thin films based on hydroxyapatite and silver-doped hydroxyapatite combined with tetracycline or ciprofloxacin. The structural and chemical characterization of hydroxyapatite and silver-doped hydroxyapatite thin films has been evaluated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The morphological studies of the HAp, Ag:HAp, T-HAp, T-Ag:HAp, C-HAp and C-Ag:HAp thin solid films were performed using scanning electron microscopy (SEM). In order to study the chemical composition of the coatings, energy dispersive X-ray analysis (EDX) and glow discharge optical emission spectroscopy (GDOES) measurements have been used, obtaining information on the distribution of the elements throughout the film. These studies have confirmed the purity of the prepared hydroxyapatite and silver-doped hydroxyapatite thin films obtained from composite targets containing Ca10−xAgx(PO4)6(OH)2 with xAg = 0 (HAp) and xAg = 0.2 (Ag:HAp). On the other hand, the major aim of this study was the evaluation of the antibacterial activities of ciprofloxacin and tetracycline in the presence of HAp and Ag:HAp thin layers against Staphylococcus aureus and Escherichia coli strains. The antibacterial activities of ciprofloxacin and tetracycline against Staphylococcus aureus and Escherichia coli test strains increased in the presence of HAp and Ag:HAp thin layers. Full article
(This article belongs to the Special Issue Bioceramics 2016)
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Open AccessArticle Effects of the CO2 Guest Molecule on the sI Clathrate Hydrate Structure
Materials 2016, 9(9), 777; https://doi.org/10.3390/ma9090777
Received: 11 July 2016 / Revised: 15 August 2016 / Accepted: 8 September 2016 / Published: 15 September 2016
Cited by 4 | Viewed by 2083 | PDF Full-text (5104 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper analyzes the structural, energetic and mechanical properties of carbon dioxide hydrate clathrates calculated using finite cluster and periodic ab initio density-functional theory methodologies. Intermolecular interactions are described by the exchange-hole dipole moment method. The stability, gas saturation energetics, guest–host interactions, cage [...] Read more.
This paper analyzes the structural, energetic and mechanical properties of carbon dioxide hydrate clathrates calculated using finite cluster and periodic ab initio density-functional theory methodologies. Intermolecular interactions are described by the exchange-hole dipole moment method. The stability, gas saturation energetics, guest–host interactions, cage deformations, vibrational frequencies, and equation of state parameters for the low-pressure sI cubic phase of the CO2@H2O clathrate hydrate are presented. Our results reveal that: (i) the gas saturation process energetically favors complete filling; (ii) carbon dioxide molecules prefer to occupy the larger of the two cages in the sI structure; (iii) blue shifts occur in both the symmetric and antisymmetric stretching frequencies of CO2 upon encapsulation; and (iv) free rotation of guest molecules is restricted to a plane parallel to the hexagonal faces of the large cages. In addition, we calculate the librational frequency of the hindered rotation of the guest molecule in the plane perpendicular to the hexagonal faces. Our calculated spectroscopic data can be used as signatures for the detection of clathrate hydrates in planetary environments. Full article
(This article belongs to the Special Issue Inorganic Clathrate Materials)
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Open AccessCommunication High-Surface-Area, Emulsion-Templated Carbon Foams by Activation of polyHIPEs Derived from Pickering Emulsions
Materials 2016, 9(9), 776; https://doi.org/10.3390/ma9090776
Received: 30 June 2016 / Revised: 31 August 2016 / Accepted: 9 September 2016 / Published: 14 September 2016
Cited by 7 | Viewed by 2300 | PDF Full-text (3295 KB) | HTML Full-text | XML Full-text
Abstract
Carbon foams displaying hierarchical porosity and excellent surface areas of >1400 m2/g can be produced by the activation of macroporous poly(divinylbenzene). Poly(divinylbenzene) was synthesized from the polymerization of the continuous, but minority, phase of a simple high internal phase Pickering emulsion. [...] Read more.
Carbon foams displaying hierarchical porosity and excellent surface areas of >1400 m2/g can be produced by the activation of macroporous poly(divinylbenzene). Poly(divinylbenzene) was synthesized from the polymerization of the continuous, but minority, phase of a simple high internal phase Pickering emulsion. By the addition of KOH, chemical activation of the materials is induced during carbonization, producing Pickering-emulsion-templated carbon foams, or carboHIPEs, with tailorable macropore diameters and surface areas almost triple that of those previously reported. The retention of the customizable, macroporous open-cell structure of the poly(divinylbenzene) precursor and the production of a large degree of microporosity during activation leads to tailorable carboHIPEs with excellent surface areas. Full article
(This article belongs to the Special Issue Pickering Emulsion and Derived Materials) Printed Edition available
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Open AccessArticle Extensive Characterization of Oxide-Coated Colloidal Gold Nanoparticles Synthesized by Laser Ablation in Liquid
Materials 2016, 9(9), 775; https://doi.org/10.3390/ma9090775
Received: 17 August 2016 / Revised: 5 September 2016 / Accepted: 12 September 2016 / Published: 14 September 2016
Cited by 4 | Viewed by 2035 | PDF Full-text (1676 KB) | HTML Full-text | XML Full-text
Abstract
Colloidal gold nanoparticles are a widespread nanomaterial with many potential applications, but their aggregation in suspension is a critical issue which is usually prevented by organic surfactants. This solution has some drawbacks, such as material contamination and modifications of its functional properties. The [...] Read more.
Colloidal gold nanoparticles are a widespread nanomaterial with many potential applications, but their aggregation in suspension is a critical issue which is usually prevented by organic surfactants. This solution has some drawbacks, such as material contamination and modifications of its functional properties. The gold nanoparticles presented in this work have been synthesized by ultra-fast laser ablation in liquid, which addresses the above issues by overcoating the metal nanoparticles with an oxide layer. The main focus of the work is in the characterization of the oxidized gold nanoparticles, which were made first in solution by means of dynamic light scattering and optical spectroscopy, and then in dried form by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and finally by surface potential measurements with atomic force microscopy. The light scattering assessed the nanoscale size of the formed particles and provided insight in their stability. The nanoparticles’ size was confirmed by direct imaging in transmission electron microscopy, and their crystalline nature was disclosed by X-ray diffraction. The X-ray photoelectron spectroscopy showed measurements compatible with the presence of surface oxide, which was confirmed by the surface potential measurements, which are the novel point of the present work. In conclusion, the method of laser ablation in liquid for the synthesis of gold nanoparticles has been presented, and the advantage of this physical approach, consisting of coating the nanoparticles in situ with gold oxide which provides the required morphological and chemical stability without organic surfactants, has been confirmed by using scanning Kelvin probe microscopy for the first time. Full article
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Open AccessArticle Investigation on the Effect of Drill Geometry and Pilot Holes on Thrust Force and Burr Height When Drilling an Aluminium/PE Sandwich Material
Materials 2016, 9(9), 774; https://doi.org/10.3390/ma9090774
Received: 14 July 2016 / Revised: 10 August 2016 / Accepted: 25 August 2016 / Published: 13 September 2016
Cited by 7 | Viewed by 1890 | PDF Full-text (14161 KB) | HTML Full-text | XML Full-text
Abstract
Composite materials are widely employed in the naval, aerospace and transportation industries owing to the combination of being lightweight and having a high modulus of elasticity, strength and stiffness. Drilling is an operation generally used in composite materials to assemble the final product. [...] Read more.
Composite materials are widely employed in the naval, aerospace and transportation industries owing to the combination of being lightweight and having a high modulus of elasticity, strength and stiffness. Drilling is an operation generally used in composite materials to assemble the final product. Damages such as the burr at the drill entrance and exit, geometric deviations and delamination are typically found in composites subjected to drilling. Drills with special geometries and pilot holes are alternatives used to improve hole quality as well as to increase tool life. The present study is focused on the drilling of a sandwich composite material (two external aluminum plates bound to a polyethylene core). In order to minimize thrust force and burr height, the influence of drill geometry, the pilot hole and the cutting parameters was assessed. Thrust force and burr height values were collected and used to perform an analysis of variance. The results indicated that the tool and the cutting speed were the parameters with more weight on the thrust force and for burr height they were the tool and the interaction between tool and feed. The results indicated that drilling with a pilot hole of Ø4 mm exhibited the best performance with regard to thrust force but facilitated plastic deformation, thus leading to the elevation of burr height, while the lowest burr height was obtained using the Brad and Spur drill geometry. Full article
(This article belongs to the Special Issue Machining of Composites and Multi-Stacks of Aerospace Materials)
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Open AccessArticle Study on Stress Development in the Phase Transition Layer of Thermal Barrier Coatings
Materials 2016, 9(9), 773; https://doi.org/10.3390/ma9090773
Received: 23 May 2016 / Revised: 7 September 2016 / Accepted: 7 September 2016 / Published: 13 September 2016
Cited by 1 | Viewed by 1481 | PDF Full-text (8537 KB) | HTML Full-text | XML Full-text
Abstract
Stress development is one of the significant factors leading to the failure of thermal barrier coating (TBC) systems. In this work, stress development in the two phase mixed zone named phase transition layer (PTL), which grows between the thermally grown oxide (TGO) and [...] Read more.
Stress development is one of the significant factors leading to the failure of thermal barrier coating (TBC) systems. In this work, stress development in the two phase mixed zone named phase transition layer (PTL), which grows between the thermally grown oxide (TGO) and the bond coat (BC), is investigated by using two different homogenization models. A constitutive equation of the PTL based on the Reuss model is proposed to study the stresses in the PTL. The stresses computed with the proposed constitutive equation are compared with those obtained with Voigt model-based equation in detail. The stresses based on the Voigt model are slightly higher than those based on the Reuss model. Finally, a further study is carried out to explore the influence of phase transition proportions on the stress difference caused by homogenization models. Results show that the stress difference becomes more evident with the increase of the PTL thickness ratio in the TGO. Full article
(This article belongs to the Special Issue Multiscale Methods and Application to Computational Materials Design)
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Open AccessArticle Electrochemical Corrosion Behavior of Ta2N Nanoceramic Coating in Simulated Body Fluid
Materials 2016, 9(9), 772; https://doi.org/10.3390/ma9090772
Received: 2 August 2016 / Revised: 1 September 2016 / Accepted: 3 September 2016 / Published: 10 September 2016
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Abstract
In order to improve the corrosion and wear resistance of biomedical Ti-6Al-4V implants, a Ta2N nanoceramic coating was synthesized on a Ti-6Al-4V substrate by the double glow discharge plasma process. The Ta2N coating, composed of fine nanocrystals, with an [...] Read more.
In order to improve the corrosion and wear resistance of biomedical Ti-6Al-4V implants, a Ta2N nanoceramic coating was synthesized on a Ti-6Al-4V substrate by the double glow discharge plasma process. The Ta2N coating, composed of fine nanocrystals, with an average grain size of 12.8 nm, improved the surface hardness of Ti-6Al-4V and showed good contact damage tolerance and good adhesion strength to the substrate. The corrosion resistance of the Ta2N coating in Ringer’s physiological solution at 37 °C was evaluated by different electrochemical techniques: potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), potentiostatic polarization and capacitance measurements (Mott-Schottky approach). The evolution of the surface composition of the passive films at different applied potentials was determined by X-ray photoelectron spectroscopy (XPS). The results indicated that the Ta2N coating showed higher corrosion resistance than both commercially pure Ta and uncoated Ti-6Al-4V in this solution, because of the formed oxide film on the Ta2N coating having a smaller carrier density (Nd) and diffusivity (Do) of point defects. The composition of the surface passive film formed on the Ta2N coating changed with the applied potential. At low applied potentials, the oxidation of the Ta2N coating led to the formation of tantalum oxynitride (TaOxNy) but, subsequently, the tantalum oxynitride (TaOxNy) could be chemically converted to Ta2O5 at higher applied potentials. Full article
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Open AccessFeature PaperArticle Enhancement of TiO2 NPs Activity by Fe3O4 Nano-Seeds for Removal of Organic Pollutants in Water
Materials 2016, 9(9), 771; https://doi.org/10.3390/ma9090771
Received: 28 July 2016 / Revised: 30 August 2016 / Accepted: 5 September 2016 / Published: 10 September 2016
Cited by 8 | Viewed by 2062 | PDF Full-text (1463 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The enhancement of the photocatalytic activity of TiO2 nanoparticles (NPs), synthesized in the presence of a very small amount of magnetite (Fe3O4) nanoparticles, is here presented and discussed. From X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses, [...] Read more.
The enhancement of the photocatalytic activity of TiO2 nanoparticles (NPs), synthesized in the presence of a very small amount of magnetite (Fe3O4) nanoparticles, is here presented and discussed. From X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses, the crystallinity of TiO2 nanoparticles (NPs) seems to be affected by Fe3O4, acting as nano-seeds to improve the tetragonal TiO2 anatase structure with respect to the amorphous one. Photocatalytic activity data, i.e., the degradation of methylene blue and the Ofloxacin fluoroquinolone emerging pollutant, give evidence that the increased crystalline structure of the NPs, even if correlated to a reduced surface to mass ratio (with respect to commercial TiO2 NPs), enhances the performance of this type of catalyst. The achievement of a relatively well-defined crystal structure at low temperatures (Tmax = 150 °C), preventing the sintering of the TiO2 NPs and, thus, preserving the high density of active sites, seems to be the keystone to understand the obtained results. Full article
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Open AccessArticle Flow Chamber System for the Statistical Evaluation of Bacterial Colonization on Materials
Materials 2016, 9(9), 770; https://doi.org/10.3390/ma9090770
Received: 14 July 2016 / Revised: 1 September 2016 / Accepted: 2 September 2016 / Published: 10 September 2016
Cited by 2 | Viewed by 1646 | PDF Full-text (5508 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Biofilm formation on materials leads to high costs in industrial processes, as well as in medical applications. This fact has stimulated interest in the development of new materials with improved surfaces to reduce bacterial colonization. Standardized tests relying on statistical evidence are indispensable [...] Read more.
Biofilm formation on materials leads to high costs in industrial processes, as well as in medical applications. This fact has stimulated interest in the development of new materials with improved surfaces to reduce bacterial colonization. Standardized tests relying on statistical evidence are indispensable to evaluate the quality and safety of these new materials. We describe here a flow chamber system for biofilm cultivation under controlled conditions with a total capacity for testing up to 32 samples in parallel. In order to quantify the surface colonization, bacterial cells were DAPI (4`,6-diamidino-2-phenylindole)-stained and examined with epifluorescence microscopy. More than 100 images of each sample were automatically taken and the surface coverage was estimated using the free open source software g’mic, followed by a precise statistical evaluation. Overview images of all gathered pictures were generated to dissect the colonization characteristics of the selected model organism Escherichia coli W3310 on different materials (glass and implant steel). With our approach, differences in bacterial colonization on different materials can be quantified in a statistically validated manner. This reliable test procedure will support the design of improved materials for medical, industrial, and environmental (subaquatic or subaerial) applications. Full article
(This article belongs to the Special Issue Advances in Biointerfaces)
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Open AccessArticle Comprehensive Numerical Simulation of Filling and Solidification of Steel Ingots
Materials 2016, 9(9), 769; https://doi.org/10.3390/ma9090769
Received: 4 July 2016 / Revised: 2 August 2016 / Accepted: 5 September 2016 / Published: 9 September 2016
Cited by 2 | Viewed by 1423 | PDF Full-text (6294 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a complete three-dimensional numerical model of mold filling and solidification of steel ingots is presented. The risk of powder entrapment and defects formation during filling is analyzed in detail, demonstrating the importance of using a comprehensive geometry, with trumpet and [...] Read more.
In this paper, a complete three-dimensional numerical model of mold filling and solidification of steel ingots is presented. The risk of powder entrapment and defects formation during filling is analyzed in detail, demonstrating the importance of using a comprehensive geometry, with trumpet and runner, compared to conventional simplified models. By using a case study, it was shown that the simplified model significantly underestimates the defects sources, reducing the utility of simulations in supporting mold and process design. An experimental test was also performed on an instrumented mold and the measurements were compared to the calculation results. The good agreement between calculation and trial allowed validating the simulation. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Compact Holographic Projection Display Using Liquid-Crystal-on-Silicon Spatial Light Modulator
Materials 2016, 9(9), 768; https://doi.org/10.3390/ma9090768
Received: 30 July 2016 / Revised: 29 August 2016 / Accepted: 5 September 2016 / Published: 9 September 2016
Cited by 4 | Viewed by 2440 | PDF Full-text (4906 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a holographic projection display in which a phase-only spatial light modulator (SLM) performs three functions: beam shaping, image display, and speckle reduction. The functions of beam shaping and image display are performed by dividing the SLM window into four sub-windows [...] Read more.
This paper presents a holographic projection display in which a phase-only spatial light modulator (SLM) performs three functions: beam shaping, image display, and speckle reduction. The functions of beam shaping and image display are performed by dividing the SLM window into four sub-windows loaded with different diffractive phase elements (DPEs). The DPEs are calculated using a modified iterative Fourier transform algorithm (IFTA). The function of speckle reduction is performed using temporal integration of display images containing speckles. The speckle contrast ratio of the display image is 0.39 due to the integration of eight speckled images. The system can be extended to display full-color images also by using temporal addition of elementary color images. Because the system configuration needs only an SLM, a Fourier transform lens, and two mirrors, the system volume is very small, becoming a potential candidate for micro projectors. Full article
(This article belongs to the Special Issue Silicon Nanophotonics)
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Open AccessArticle Preparation and Properties of Alkali Activated Metakaolin-Based Geopolymer
Materials 2016, 9(9), 767; https://doi.org/10.3390/ma9090767
Received: 14 May 2016 / Revised: 30 August 2016 / Accepted: 2 September 2016 / Published: 8 September 2016
Cited by 10 | Viewed by 1829 | PDF Full-text (2346 KB) | HTML Full-text | XML Full-text
Abstract
The effective activation and utilization of metakaolin as an alkali activated geopolymer precursor and its use in concrete surface protection is of great interest. In this paper, the formula of alkali activated metakaolin-based geopolymers was studied using an orthogonal experimental design. It was [...] Read more.
The effective activation and utilization of metakaolin as an alkali activated geopolymer precursor and its use in concrete surface protection is of great interest. In this paper, the formula of alkali activated metakaolin-based geopolymers was studied using an orthogonal experimental design. It was found that the optimal geopolymer was prepared with metakaolin, sodium hydroxide, sodium silicate and water, with the molar ratio of SiO2:Al2O3:Na2O:NaOH:H2O being 3.4:1.1:0.5:1.0:11.8. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were adopted to investigate the influence of curing conditions on the mechanical properties and microstructures of the geopolymers. The best curing condition was 60 °C for 168 h, and this alkali activated metakaolin-based geopolymer showed the highest compression strength at 52.26 MPa. In addition, hollow micro-sphere glass beads were mixed with metakaolin particles to improve the thermal insulation properties of the alkali activated metakaolin-based geopolymer. These results suggest that a suitable volume ratio of metakaolin to hollow micro-sphere glass beads in alkali activated metakaolin-based geopolymers was 6:1, which achieved a thermal conductivity of 0.37 W/mK and compressive strength of 50 MPa. By adjusting to a milder curing condition, as-prepared alkali activated metakaolin-based geopolymers could find widespread applications in concrete thermal protection. Full article
(This article belongs to the Special Issue Advances in Geopolymers and Alkali-Activated Materials)
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Open AccessArticle The Synthesis of LiMnxFe1−xPO4/C Cathode Material through Solvothermal Jointed with Solid-State Reaction
Materials 2016, 9(9), 766; https://doi.org/10.3390/ma9090766
Received: 6 June 2016 / Revised: 1 August 2016 / Accepted: 29 August 2016 / Published: 8 September 2016
Cited by 1 | Viewed by 1588 | PDF Full-text (4043 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
LiMnxFe1−xPO4/C material has been synthesized through a facile solid-state reaction under the condition of carbon coating, using solvothermal-prepared LiMnPO4 and LiFePO4 as precursors and sucrose as a carbon resource. XRD and element distribution analysis [...] Read more.
LiMnxFe1−xPO4/C material has been synthesized through a facile solid-state reaction under the condition of carbon coating, using solvothermal-prepared LiMnPO4 and LiFePO4 as precursors and sucrose as a carbon resource. XRD and element distribution analysis reveal completed solid-state reaction of precursors. LiMnxFe1−xPO4/C composites inherit the morphology of precursors after heat treatment without obvious agglomeration and size increase. LiMnxFe1−xPO4 solid solution forms at low temperature around 350 °C, and Mn2+/Fe2+ diffuse completely within 1 h at 650 °C. The LiMnxFe1−xPO4/C (x < 0.8) composite exhibits a high-discharge capacity of over 120 mAh·g−1 (500 Wh·kg−1) at low C-rates. This paves a way to synthesize the crystal-optimized LiMnxFe1−xPO4/C materials for high performance Li-ion batteries. Full article
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Open AccessArticle Influence of the Conditioning Method for Pre-Sintered Zirconia on the Shear Bond Strength of Bilayered Porcelain/Zirconia
Materials 2016, 9(9), 765; https://doi.org/10.3390/ma9090765
Received: 3 August 2016 / Revised: 25 August 2016 / Accepted: 2 September 2016 / Published: 8 September 2016
Cited by 1 | Viewed by 1517 | PDF Full-text (2115 KB) | HTML Full-text | XML Full-text
Abstract
This study evaluated the bond strength of veneering porcelain with an experimental conditioner-coated zirconia. Pre-sintered Y-TZP specimens (n = 44) were divided in two groups based on conditioning type. After sintering, all sample surfaces were sandblasted and layered with veneering porcelain. Additionally, [...] Read more.
This study evaluated the bond strength of veneering porcelain with an experimental conditioner-coated zirconia. Pre-sintered Y-TZP specimens (n = 44) were divided in two groups based on conditioning type. After sintering, all sample surfaces were sandblasted and layered with veneering porcelain. Additionally, half of the specimens in each group underwent thermal cycling (10,000 cycles, 5–55 °C), and all shear bond strengths were measured. After testing, the failure mode of each fractured specimen was determined. Differences were tested by parametric and Fisher’s exact tests (α = 0.05). The differences in bond strength were not statistically significant. Adhesive fractures were dominantly observed for the non-thermal cycled specimens. After thermal cycling, the conditioner-coated group showed cohesive and mixed fractures (p = 0.0021), whereas the uncoated group showed more adhesive fractures (p = 0.0021). Conditioning of the pre-sintered Y-TZP did not change the shear bond strength of the veneering porcelain, but did improve the failure mode after thermal cycling. Full article
(This article belongs to the Section Biomaterials)
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Open AccessArticle Fatigue and Fracture Behavior of a Cold-Drawn Commercially Pure Aluminum Wire
Materials 2016, 9(9), 764; https://doi.org/10.3390/ma9090764
Received: 12 July 2016 / Revised: 5 September 2016 / Accepted: 5 September 2016 / Published: 8 September 2016
Cited by 1 | Viewed by 1972 | PDF Full-text (3463 KB) | HTML Full-text | XML Full-text
Abstract
Fatigue properties and cracking behavior of cold-drawn commercially pure aluminum wires (CPAWs) widely used as the overhead transmission conductors were investigated. It was found that the fracture surface of the CPAWs shows an obvious four-stage fracture characteristic, i.e., crack initiation, planar crack propagation, [...] Read more.
Fatigue properties and cracking behavior of cold-drawn commercially pure aluminum wires (CPAWs) widely used as the overhead transmission conductors were investigated. It was found that the fracture surface of the CPAWs shows an obvious four-stage fracture characteristic, i.e., crack initiation, planar crack propagation, 45°-inclined crack propagation and final rapid fracture. The crack growth mechanisms for the CPAWs were found quite different from those for the conventional coarse-grained materials. The cracks in the CPAWs firstly grow along the grain boundaries (Stage I crack growth), and then grow along the plane of maximum shear stress during the last stage of cycling (Stage II crack growth), leading to the distinctive fracture surfaces, i.e., the granular surface in the planar crack propagation region and the coarse fatigue striations in the 45°-inclined crack propagation region. The grain boundary migration was observed in the fatigued CPAWs. The increase in fatigue load enhances the dislocation recovery, increases the grain boundary migration rate, and thus promotes the occurrence of softening and damage localization up to the final failure. Full article
(This article belongs to the Special Issue Fracture and Fatigue Mechanics of Materials)
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