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Materials, Volume 4, Issue 12 (December 2011), Pages 2061-2243

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Research

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Open AccessArticle Characterization of the Materials Synthesized by High Pressure-High Temperature Treatment of a Polymer Derived t-BC2N Ceramic
Materials 2011, 4(12), 2061-2072; doi:10.3390/ma4122061
Received: 11 October 2011 / Accepted: 10 November 2011 / Published: 29 November 2011
Cited by 3 | PDF Full-text (584 KB) | HTML Full-text | XML Full-text
Abstract
Bulk B-C-N materials were synthesized under static high thermobaric conditions (20 GPa and 2,000 °C) in a multianvil apparatus from a polymer derived t-BC1.97N ceramic. The bulk samples were characterised using X-ray synchrotron radiation and analytical transmission electron microscopy in combination
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Bulk B-C-N materials were synthesized under static high thermobaric conditions (20 GPa and 2,000 °C) in a multianvil apparatus from a polymer derived t-BC1.97N ceramic. The bulk samples were characterised using X-ray synchrotron radiation and analytical transmission electron microscopy in combination with electron energy loss spectroscopy. Polycrystalline B-C-N materials with a cubic type structure were formed under the applied reaction conditions, but the formation of a ternary cubic diamond-like c-BC2N compound, could not be unambiguously confirmed. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)
Open AccessArticle Arsenic-Doped High-Resistivity-Silicon Epitaxial Layers for Integrating Low-Capacitance Diodes
Materials 2011, 4(12), 2092-2107; doi:10.3390/ma4122092
Received: 6 October 2011 / Revised: 14 November 2011 / Accepted: 24 November 2011 / Published: 6 December 2011
Cited by 5 | PDF Full-text (1133 KB) | HTML Full-text | XML Full-text
Abstract
An arsenic doping technique for depositing up to 40-μm-thick high-resistivity layers is presented for fabricating diodes with low RC constants that can be integrated in closely-packed configurations. The doping of the as-grown epi-layers is controlled down to 5 × 1011 cm−3
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An arsenic doping technique for depositing up to 40-μm-thick high-resistivity layers is presented for fabricating diodes with low RC constants that can be integrated in closely-packed configurations. The doping of the as-grown epi-layers is controlled down to 5 × 1011 cm−3, a value that is solely limited by the cleanness of the epitaxial reactor chamber. To ensure such a low doping concentration, first an As-doped Si seed layer is grown with a concentration of 1016 to 1017 cm−3, after which the dopant gas arsine is turned off and a thick lightly-doped epi-layer is deposited. The final doping in the thick epi-layer relies on the segregation and incorporation of As from the seed layer, and it also depends on the final thickness of the layer, and the exact growth cycles. The obtained epi-layers exhibit a low density of stacking faults, an over-the-wafer doping uniformity of 3.6%, and a lifetime of generated carriers of more than 2.5 ms. Furthermore, the implementation of a segmented photodiode electron detector is demonstrated, featuring a 30 pF capacitance and a 90 Ω series resistance for a 7.6 mm2 anode area. Full article
(This article belongs to the Special Issue Epitaxial Materials)
Open AccessArticle Heat Conduction in a Functionally Graded Plate Subjected to Finite Cooling/Heating Rates: An Asymptotic Solution
Materials 2011, 4(12), 2108-2118; doi:10.3390/ma4122108
Received: 19 October 2011 / Revised: 2 December 2011 / Accepted: 5 December 2011 / Published: 8 December 2011
Cited by 1 | PDF Full-text (318 KB) | HTML Full-text | XML Full-text
Abstract
This work investigates transient heat conduction in a functionally graded plate (FGM plate) subjected to gradual cooling/heating at its boundaries. The thermal properties of the FGM are assumed to be continuous and piecewise differentiable functions of the coordinate in the plate thickness direction.
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This work investigates transient heat conduction in a functionally graded plate (FGM plate) subjected to gradual cooling/heating at its boundaries. The thermal properties of the FGM are assumed to be continuous and piecewise differentiable functions of the coordinate in the plate thickness direction. A linear ramp function describes the cooling/heating rates at the plate boundaries. A multi-layered material model and Laplace transform are employed to obtain the transformed temperatures at the interfaces between the layers. An asymptotic analysis and an integration technique are then used to obtain a closed form asymptotic solution of the temperature field in the FGM plate for short times. The thermal stress intensity factor (TSIF) for an edge crack in the FGM plate calculated based on the asymptotic temperature solution shows that the asymptotic solution can capture the peak TSIFs under the finite cooling rate conditions. Full article
(This article belongs to the Special Issue Advances in Functionally Graded Materials)
Open AccessArticle Formulation Optimization of Gluten-Free Functional Spaghetti Based on Maize Flour and Oat Bran Enriched in b-Glucans
Materials 2011, 4(12), 2119-2135; doi:10.3390/ma4122119
Received: 4 October 2011 / Accepted: 2 December 2011 / Published: 8 December 2011
Cited by 11 | PDF Full-text (213 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this work concerns the manufacturing process of gluten-free functional spaghetti based on maize flour and oat bran, enriched with b-glucans (22%). More specifically, the goal of the study was to obtain oat bran-loaded maize spaghetti with sensory properties close to
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The aim of this work concerns the manufacturing process of gluten-free functional spaghetti based on maize flour and oat bran, enriched with b-glucans (22%). More specifically, the goal of the study was to obtain oat bran-loaded maize spaghetti with sensory properties close to unloaded pasta. To this aim, the study has been organized in two subsequent trials. In the first one, the oat bran amount added to spaghetti was continuously increased until the overall sensory quality of pasta reached the set sensory threshold (oat bran concentration = 20%). The second experimental step was aimed to improve the overall sensory quality of oat bran loaded maize spaghetti. In particular, an attempt was made to increase the sensory quality of spaghetti added with 20% oat bran by means of structuring agents. To this aim, the effects of different kinds of some hydrocolloids and egg white powder on the rheological properties of dough, as well as on quality attributes of pasta were examined. The rheological analysis showed that the addition of hydrocolloids and white egg to the dough enriched with 20% oat bran did not cause any substantial difference in the viscoelastic properties, compared to samples without any structuring agents. The best overall quality for both fresh and dry spaghetti was obtained by the addition of carboxymethylcellulose and chitosan at a concentration of 2%. Full article
(This article belongs to the Special Issue Carbohydrate Polymers)
Open AccessArticle Transient Thermal Stress Problem of a Functionally Graded Magneto-Electro-Thermoelastic Hollow Sphere
Materials 2011, 4(12), 2136-2150; doi:10.3390/ma4122136
Received: 2 November 2011 / Revised: 4 December 2011 / Accepted: 7 December 2011 / Published: 12 December 2011
Cited by 1 | PDF Full-text (332 KB) | HTML Full-text | XML Full-text
Abstract
This article is concerned with the theoretical analysis of the functionally graded magneto-electro-thermoelastic hollow sphere due to uniform surface heating. We analyze the transient thermoelastic problem for a functionally graded hollow sphere constructed of the spherical isotropic and linear magneto-electro-thermoelastic materials using a
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This article is concerned with the theoretical analysis of the functionally graded magneto-electro-thermoelastic hollow sphere due to uniform surface heating. We analyze the transient thermoelastic problem for a functionally graded hollow sphere constructed of the spherical isotropic and linear magneto-electro-thermoelastic materials using a laminated composite mode as one of theoretical approximation in the spherically symmetric state. As an illustration, we carry out numerical calculations for a functionally graded hollow sphere constructed of piezoelectric and magnetostrictive materials and examine the behaviors in the transient state. The effects of the nonhomogeneity of material on the stresses, electric potential, and magnetic potential are investigated. Full article
(This article belongs to the Special Issue Advances in Functionally Graded Materials)
Open AccessArticle Thermo-Electro-Mechanical Analysis of a Curved Functionally Graded Piezoelectric Actuator with Sandwich Structure
Materials 2011, 4(12), 2151-2170; doi:10.3390/ma4122151
Received: 1 November 2011 / Revised: 28 November 2011 / Accepted: 6 December 2011 / Published: 12 December 2011
Cited by 5 | PDF Full-text (501 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the problem of a curved functionally graded piezoelectric (FGP) actuator with sandwich structure under electrical and thermal loads is investigated. The middle layer in the sandwich structure is functionally graded with the piezoelectric coefficient g31 varying continuously along the
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In this work, the problem of a curved functionally graded piezoelectric (FGP) actuator with sandwich structure under electrical and thermal loads is investigated. The middle layer in the sandwich structure is functionally graded with the piezoelectric coefficient g31 varying continuously along the radial direction of the curved actuator. Based on the theory of linear piezoelectricity, analytical solutions are obtained by using Airy stress function to examine the effects of material gradient and heat conduction on the performance of the curved actuator. It is found that the material gradient and thermal load have significant influence on the electroelastic fields and the mechanical response of the curved FGP actuator. Without the sacrifice of actuation deflection, smaller internal stresses are generated by using the sandwich actuator with functionally graded piezoelectric layer instead of the conventional bimorph actuator. This work is very helpful for the design and application of curved piezoelectric actuators under thermal environment. Full article
(This article belongs to the Special Issue Advances in Functionally Graded Materials)
Open AccessArticle Electrochromic Type E-Paper Using Poly(1H-Thieno[3,4-d]Imidazol-2(3H)-One) Derivatives by a Novel Printing Fabrication Process
Materials 2011, 4(12), 2171-2182; doi:10.3390/ma4122171
Received: 8 October 2011 / Revised: 8 December 2011 / Accepted: 9 December 2011 / Published: 14 December 2011
Cited by 11 | PDF Full-text (452 KB) | HTML Full-text | XML Full-text
Abstract
In this study, we report poly(1H-thieno[3,4-d]imidazol-2(3H)-one) (pTIO) derivatives for an electrochromic (EC) type e-paper and its novel printing fabrication process. pTIO is a kind of conductive polymer (CP) s which are known as one of the EC materials. The electrochromism of pTIO is
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In this study, we report poly(1H-thieno[3,4-d]imidazol-2(3H)-one) (pTIO) derivatives for an electrochromic (EC) type e-paper and its novel printing fabrication process. pTIO is a kind of conductive polymer (CP) s which are known as one of the EC materials. The electrochromism of pTIO is unique, because its color in doped state is almost transparent (pale gray). A transparent state is required to show a white color in a see-through view of an EC type e-paper. An electrochromism of CP has a good memory effect which is applicable for e-paper. The corresponding monomers of CP are able to be polymerized with an electrochemical method, which be made good use of for the fabrication process of e-paper. pTIO derivatives are copolymerized with other pi-conjugated X unit, which adjusts the color of electrochromism. Finally, we fabricated a segment matrix EC display using pTIO derivatives by ink-jet printing. Full article
(This article belongs to the Special Issue Electrochromic Materials and Devices)
Open AccessArticle Novel Concept to Detect an Optimum Thixoforming Condition of Al-Al3Ni Functionally Graded Material by Wavelet Analysis for Online Operation
Materials 2011, 4(12), 2183-2196; doi:10.3390/ma4122183
Received: 31 October 2011 / Revised: 8 December 2011 / Accepted: 9 December 2011 / Published: 14 December 2011
Cited by 1 | PDF Full-text (459 KB) | HTML Full-text | XML Full-text
Abstract
A novel technique to characterize the transition phenomenon from solid to melt of Al-Al3Ni functionally graded material (FGM) through a wavelet analysis for the development of a thixoforming system is investigated. Identification of an optimum semi-solid condition for thixoforming is necessary
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A novel technique to characterize the transition phenomenon from solid to melt of Al-Al3Ni functionally graded material (FGM) through a wavelet analysis for the development of a thixoforming system is investigated. Identification of an optimum semi-solid condition for thixoforming is necessary not only for the construction of a system but also the fabrication of a near-net-shape product with fine microstructure. An online wavelet analysis system using Haar’s wavelet function, which is applied for its simplicity compared with Daubechies’ wavelet function, is developed to find the optimum operating condition. A thixoforming system, which is constructed adapting a threshold value as an index, monitors successfully a discontinuity of deformation of Al-Al3Ni FGM with the temperature rise. Thus, the timing of an operation is not at pre-fixed temperature but at the time when the index related to a wavelet function is satisfied. The concept is confirmed to be suitable from the micro-structural observation of the Al-Al3Ni FGM product, because the product under the optimum condition is found to have refined Al3Ni grains, which change from coarse grains and are expected to improve the mechanical properties. Full article
(This article belongs to the Special Issue Advances in Functionally Graded Materials)
Open AccessArticle In Vivo Degradation Behavior of the Magnesium Alloy LANd442 in Rabbit Tibiae
Materials 2011, 4(12), 2197-2218; doi:10.3390/ma4122197
Received: 21 November 2011 / Revised: 2 December 2011 / Accepted: 9 December 2011 / Published: 15 December 2011
Cited by 19 | PDF Full-text (4762 KB) | HTML Full-text | XML Full-text
Abstract
In former studies the magnesium alloy LAE442 showed promising in vivo degradation behavior and biocompatibility. However, reproducibility might be enhanced by replacement of the rare earth composition metal “E” by only a single rare earth element. Therefore, it was the aim of this
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In former studies the magnesium alloy LAE442 showed promising in vivo degradation behavior and biocompatibility. However, reproducibility might be enhanced by replacement of the rare earth composition metal “E” by only a single rare earth element. Therefore, it was the aim of this study to examine whether the substitution of “E” by neodymium (“Nd”) had an influence on the in vivo degradation rate. LANd442 implants were inserted into rabbit tibiae and rabbits were euthanized after 4, 8, 13 and 26 weeks postoperatively. In vivo µCT was performed to evaluate the in vivo implant degradation behaviour by calculation of implant volume, density true 3-D thickness and corrosion rates. Additionally, weight loss, type of corrosion and mechanical stability were appraised by SEM/EDS-analysis and three-point bending tests. Implant volume, density and true 3-D thickness decreased over time, whereas the variance of the maximum diameters within an implant as well as the corrosion rate and weight loss increased. SEM examination revealed mainly pitting corrosion after 26 weeks. The maximum bending forces decreased over time. In comparison to LAE442, the new alloy showed a slower, but more uneven degradation behavior and less mechanical stability. To summarize, LANd442 appeared suitable for low weight bearing bones but is inferior to LAE442 regarding its degradation morphology and strength. Full article
Open AccessArticle Novel Repair Concept for Composite Materials by Repetitive Geometrical Interlock Elements
Materials 2011, 4(12), 2219-2230; doi:10.3390/ma4122219
Received: 1 November 2011 / Revised: 7 December 2011 / Accepted: 12 December 2011 / Published: 20 December 2011
Cited by 2 | PDF Full-text (2393 KB) | HTML Full-text | XML Full-text
Abstract
Material adapted repair technologies for fiber-reinforced polymers with thermosetting matrix systems are currently characterized by requiring major efforts for repair preparation and accomplishment in all industrial areas of application. In order to allow for a uniform distribution of material and geometrical parameters over
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Material adapted repair technologies for fiber-reinforced polymers with thermosetting matrix systems are currently characterized by requiring major efforts for repair preparation and accomplishment in all industrial areas of application. In order to allow for a uniform distribution of material and geometrical parameters over the repair zone, a novel composite interlock repair concept is introduced, which is based on a repair zone with undercuts prepared by water-jet technology. The presented numerical and experimental sensitivity analyses make a contribution to the systematic development of the interlock repair technology with respect to material and geometrical factors of influence. The results show the ability of the novel concept for a reproducible and automatable composite repair. Full article
(This article belongs to the Special Issue Fibre-Reinforced Composites)
Open AccessArticle Non-Isothermal Kinetic Analysis of the Crystallization of Metallic Glasses Using the Master Curve Method
Materials 2011, 4(12), 2231-2243; doi:10.3390/ma4122231
Received: 27 October 2011 / Revised: 12 December 2011 / Accepted: 14 December 2011 / Published: 20 December 2011
Cited by 8 | PDF Full-text (2142 KB) | HTML Full-text | XML Full-text
Abstract
The non-isothermal transformation rate curves of metallic glasses are analyzed with the Master Curve method grounded in the Kolmogorov-Johnson-Mehl-Avrami theory. The method is applied to the study of two different metallic glasses determining the activation energy of the transformation and the experimental kinetic
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The non-isothermal transformation rate curves of metallic glasses are analyzed with the Master Curve method grounded in the Kolmogorov-Johnson-Mehl-Avrami theory. The method is applied to the study of two different metallic glasses determining the activation energy of the transformation and the experimental kinetic function that is analyzed using Avrami kinetics. The analysis of the crystallization of Cu47Ti33Zr11Ni8Si1 metallic glassy powders gives Ea = 3.8 eV, in good agreement with the calculation by other methods, and a transformation initiated by an accelerating nucleation and diffusion-controlled growth. The other studied alloy is a Nanoperm-type Fe77Nb7B15Cu1 metallic glass with a primary crystallization of bcc-Fe. An activation energy of Ea = 5.7 eV is obtained from the Master Curve analysis. It is shown that the use of Avrami kinetics is not able to explain the crystallization mechanisms in this alloy giving an Avrami exponent of n = 1. Full article
(This article belongs to the Special Issue Advances in Bulk Metallic Glasses)

Review

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Open AccessReview Hydrogen
Materials 2011, 4(12), 2073-2091; doi:10.3390/ma4122073
Received: 20 September 2011 / Revised: 25 October 2011 / Accepted: 15 November 2011 / Published: 30 November 2011
Cited by 5 | PDF Full-text (582 KB) | HTML Full-text | XML Full-text
Abstract
The idea of a “Hydrogen Economy” is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO2 in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of
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The idea of a “Hydrogen Economy” is that carbon containing fuels should be replaced by hydrogen, thus eliminating air pollution and growth of CO2 in the atmosphere. However, storage of a gas, its transport and reconversion to electricity doubles the cost of H2 from the electrolyzer. Methanol made with CO2 from the atmosphere is a zero carbon fuel created from inexhaustible components from the atmosphere. Extensive work on the splitting of water by bacteria shows that if wastes are used as the origin of feed for certain bacteria, the cost for hydrogen becomes lower than any yet known. The first creation of hydrogen and electricity from light was carried out in 1976 by Ohashi et al. at Flinders University in Australia. Improvements in knowledge of the structure of the semiconductor-solution system used in a solar breakdown of water has led to the discovery of surface states which take part in giving rise to hydrogen (Khan). Photoelectrocatalysis made a ten times increase in the efficiency of the photo production of hydrogen from water. The use of two electrode cells; p and n semiconductors respectively, was first introduced by Uosaki in 1978. Most photoanodes decompose during the photoelectrolysis. To avoid this, it has been necessary to create a transparent shield between the semiconductor and its electronic properties and the solution. In this way, 8.5% at 25 °C and 9.5% at 50 °C has been reached in the photo dissociation of water (GaP and InAs) by Kainthla and Barbara Zeleney in 1989. A large consortium has been funded by the US government at the California Institute of Technology under the direction of Nathan Lewis. The decomposition of water by light is the main aim of this group. Whether light will be the origin of the post fossil fuel supply of energy may be questionable, but the maximum program in this direction is likely to come from Cal. Tech. Full article
(This article belongs to the Special Issue Advanced Materials for Water-Splitting)

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