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Materials, Volume 6, Issue 1 (January 2013) – 23 articles , Pages 1-391

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4225 KiB  
Review
Recent Advances in Characterization of Lignin Polymer by Solution-State Nuclear Magnetic Resonance (NMR) Methodology
by Jia-Long Wen, Shao-Long Sun, Bai-Liang Xue and Run-Cang Sun
Materials 2013, 6(1), 359-391; https://doi.org/10.3390/ma6010359 - 23 Jan 2013
Cited by 589 | Viewed by 20054
Abstract
The demand for efficient utilization of biomass induces a detailed analysis of the fundamental chemical structures of biomass, especially the complex structures of lignin polymers, which have long been recognized for their negative impact on biorefinery. Traditionally, it has been attempted to reveal [...] Read more.
The demand for efficient utilization of biomass induces a detailed analysis of the fundamental chemical structures of biomass, especially the complex structures of lignin polymers, which have long been recognized for their negative impact on biorefinery. Traditionally, it has been attempted to reveal the complicated and heterogeneous structure of lignin by a series of chemical analyses, such as thioacidolysis (TA), nitrobenzene oxidation (NBO), and derivatization followed by reductive cleavage (DFRC). Recent advances in nuclear magnetic resonance (NMR) technology undoubtedly have made solution-state NMR become the most widely used technique in structural characterization of lignin due to its versatility in illustrating structural features and structural transformations of lignin polymers. As one of the most promising diagnostic tools, NMR provides unambiguous evidence for specific structures as well as quantitative structural information. The recent advances in two-dimensional solution-state NMR techniques for structural analysis of lignin in isolated and whole cell wall states (in situ), as well as their applications are reviewed. Full article
(This article belongs to the Special Issue NMR in Materials Science)
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1614 KiB  
Article
Holographic Spectroscopy: Wavelength-Dependent Analysis of Photosensitive Materials by Means of Holographic Techniques
by Kay-Michael Voit and Mirco Imlau
Materials 2013, 6(1), 334-358; https://doi.org/10.3390/ma6010334 - 23 Jan 2013
Cited by 10 | Viewed by 8014
Abstract
Holographic spectroscopy is highlighted as a powerful tool for the analysis of photosensitive materials with pronounced alterations of the complex permittivity over a broad range in the visible spectrum, due to the advances made both in the fields of advanced holographic media and [...] Read more.
Holographic spectroscopy is highlighted as a powerful tool for the analysis of photosensitive materials with pronounced alterations of the complex permittivity over a broad range in the visible spectrum, due to the advances made both in the fields of advanced holographic media and highly tunable lasers systems. To analytically discuss consequences for in- and off-Bragg reconstruction, we revised Kogelnik’s coupled wave theory strictly on the basis of complex permittivities. We extended it to comply with modern experimental parameters such as out-of-phase mixed holograms and highly modulated gratings. A spatially modulated, wavelength-dependent permittivity that superimposes a spatially homogeneous wavelength-dependent ground state spectrum is taken into account for signal wave reconstruction with bulky elementary mixed gratings as an example. The dispersion characteristics of the respective diffraction efficiency is modelled for color-center-absorption and absorption of strongly localized carriers. As an example for the theoretical possibilities of our newly derived set of equations, we present a quantitative analysis of the Borrmann effect connected to out-of-phase gratings, providing easier and more intuitive methods for the derivation of their grating parameters. Full article
(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)
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801 KiB  
Article
Low Stress Mechanical Properties of Plasma-Treated Cotton Fabric Subjected to Zinc Oxide-Anti-Microbial Treatment
by Chi-Wai Kan and Yin-Ling Lam
Materials 2013, 6(1), 314-333; https://doi.org/10.3390/ma6010314 - 22 Jan 2013
Cited by 37 | Viewed by 6494
Abstract
Cotton fabrics are highly popular because of their excellent properties such as regeneration, bio-degradation, softness, affinity to skin and hygroscopic properties. When in contact with the human body, cotton fabrics offer an ideal environment for microbial growth due to their ability to retain [...] Read more.
Cotton fabrics are highly popular because of their excellent properties such as regeneration, bio-degradation, softness, affinity to skin and hygroscopic properties. When in contact with the human body, cotton fabrics offer an ideal environment for microbial growth due to their ability to retain oxygen, moisture and warmth, as well as nutrients from spillages and body sweat. Therefore, an anti-microbial coating formulation (Microfresh and Microban together with zinc oxide as catalyst) was developed for cotton fabrics to improve treatment effectiveness. In addition, plasma technology was employed in the study which roughened the surface of the materials, improving the loading of zinc oxides on the surface. In this study, the low stress mechanical properties of plasma pre-treated and/or anti-microbial-treated cotton fabric were studied. The overall results show that the specimens had improved bending properties when zinc oxides were added in the anti-microbial coating recipe. Also, without plasma pre-treatment, anti-microbial-treatment of cotton fabric had a positive effect only on tensile resilience, shear stress at 0.5° and compressional energy, while plasma-treated specimens had better overall tensile properties even after anti-microbial treatment. Full article
(This article belongs to the Special Issue Advances in Cellulosic Materials)
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1015 KiB  
Review
Recent Progress in Fourier Transform Infrared (FTIR) Spectroscopy Study of Compositional, Structural and Physical Attributes of Developmental Cotton Fibers
by Yongliang Liu
Materials 2013, 6(1), 299-313; https://doi.org/10.3390/ma6010299 - 22 Jan 2013
Cited by 61 | Viewed by 6936
Abstract
Cotton fibers are natural plant products, and their end-use qualities depend on their stages of development. In general, the quantity of cellulose in cotton fibers increases rapidly, thus it leads to compositional, structural and physical attribute variations among the fibers with shorter and [...] Read more.
Cotton fibers are natural plant products, and their end-use qualities depend on their stages of development. In general, the quantity of cellulose in cotton fibers increases rapidly, thus it leads to compositional, structural and physical attribute variations among the fibers with shorter and longer growth periods. This article discusses recent progress in applying the Fourier transform infrared (FTIR) spectroscopic technique to characterize these differences, to discriminate immature fibers from mature fibers, to assess fiber maturity and crystallinity and also to unravel the band assignments in crystalline and amorphous celluloses. The results were achieved through the use of various strategies, including wet chemical analysis, principal component analysis (PCA), simple algorithm development, two-dimensional correlation analysis and other independent fiber tests. Of particular interest is that, in general, immature fibers might have the characteristics of less than 21–28 dpa, MIR < 0.58 (in the maturity range of 0 to 1.0) and CIIR < 42% (in the crystallinity range of 0 to 100%). Full article
(This article belongs to the Special Issue Advances in Cellulosic Materials)
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185 KiB  
Article
Single Grain Boundary Modeling and Design of Microcrystalline Si Solar Cells
by Chu-Hsuan Lin, Wen-Tzu Hsu and Cheng-Hung Tai
Materials 2013, 6(1), 291-298; https://doi.org/10.3390/ma6010291 - 21 Jan 2013
Cited by 2 | Viewed by 4718
Abstract
For photovoltaic applications, microcrystalline silicon has a lot of advantages, such as the ability to absorb the near-infrared part of the solar spectrum. However, there are many dangling bonds at the grain boundary in microcrystalline Si. These dangling bonds would lead to the [...] Read more.
For photovoltaic applications, microcrystalline silicon has a lot of advantages, such as the ability to absorb the near-infrared part of the solar spectrum. However, there are many dangling bonds at the grain boundary in microcrystalline Si. These dangling bonds would lead to the recombination of photo-generated carriers and decrease the conversion efficiency. Therefore, we included the grain boundary in the numerical study in order to simulate a microcrystalline Si solar cell accurately, designing new three-terminal microcrystalline Si solar cells. The 3-μm-thick three-terminal cell achieved a conversion efficiency of 10.8%, while the efficiency of a typical two-terminal cell is 9.7%. The three-terminal structure increased the JSC but decreased the VOC, and such phenomena are discussed. High-efficiency and low-cost Si-based thin film solar cells can now be designed based on the information provided in this paper. Full article
(This article belongs to the Special Issue Photovoltaic Materials)
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231 KiB  
Article
“Property Phase Diagrams” for Compound Semiconductors through Data Mining
by Srikant Srinivasan and Krishna Rajan
Materials 2013, 6(1), 279-290; https://doi.org/10.3390/ma6010279 - 21 Jan 2013
Cited by 30 | Viewed by 7089
Abstract
This paper highlights the capability of materials informatics to recreate “property phase diagrams” from an elemental level using electronic and crystal structure properties. A judicious selection of existing data mining techniques, such as Principal Component Analysis, Partial Least Squares Regression, and Correlated Function [...] Read more.
This paper highlights the capability of materials informatics to recreate “property phase diagrams” from an elemental level using electronic and crystal structure properties. A judicious selection of existing data mining techniques, such as Principal Component Analysis, Partial Least Squares Regression, and Correlated Function Expansion, are linked synergistically to predict bandgap and lattice parameters for different stoichiometries of GaxIn1−xAsySb1−y, starting from fundamental elemental descriptors. In particular, five such elemental descriptors, extracted from within a database of highly correlated descriptors, are shown to collectively capture the widely studied “bowing” of energy bandgaps seen in compound semiconductors. This is the first such demonstration, to our knowledge, of establishing relationship between discrete elemental descriptors and bandgap bowing, whose underpinning lies in the fundamentals of solid solution thermodyanamics. Full article
(This article belongs to the Special Issue Compound Semiconductor Materials)
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521 KiB  
Article
Photocatalytic Oxidation of Low-Level Airborne 2-Propanol and Trichloroethylene over Titania Irradiated with Bulb-Type Light-Emitting Diodes
by Wan-Kuen Jo
Materials 2013, 6(1), 265-278; https://doi.org/10.3390/ma6010265 - 18 Jan 2013
Cited by 9 | Viewed by 5426
Abstract
This study examined the photocatalytic oxidation of gas-phase trichloroethylene (TCE) and 2-propanol, at indoor levels, over titanium dioxide (TiO2) irradiated with light-emitting diodes (LED) under different operational conditions. TiO2 powder baked at 450 °C exhibited the highest photocatalytic decomposition efficiency [...] Read more.
This study examined the photocatalytic oxidation of gas-phase trichloroethylene (TCE) and 2-propanol, at indoor levels, over titanium dioxide (TiO2) irradiated with light-emitting diodes (LED) under different operational conditions. TiO2 powder baked at 450 °C exhibited the highest photocatalytic decomposition efficiency (PDE) for TCE, while all photocatalysts baked at different temperatures showed similar PDEs for 2-propanol. The average PDEs of TCE over a three hour period were four, four, five, and 51% for TiO2 powders baked at 150, 250, 350, and 450 °C, respectively. The average PDEs of 2-propanol were 95, 97, 98, and 96% for TiO2 powders baked at 150, 250, 350, and 450 °C, respectively. The ratio of anatase at 2θ = 25.2° to rutile at 2θ = 27.4° was lowest for the TiO2 powder baked at 450 °C. Although the LED-irradiated TiO2 system revealed lower PDEs of TCE and 2-propanol when compared to those of the eight watt, black-light lamp-irradiated TiO2 system, the results for the PDEs normalized to the energy consumption were reversed. Other operational parameters, such as relative humidity, input concentrations, flow rate, and feeding type were also found to influence the photocatalytic performance of the UV LED-irradiated TiO2 system when applied to the cleaning of TCE and 2-propanol at indoor air levels. Full article
(This article belongs to the Special Issue Advances in Catalytic Materials)
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5664 KiB  
Article
Nanomagnetic Gene Transfection for Non-Viral Gene Delivery in NIH 3T3 Mouse Embryonic Fibroblasts
by Angeliki Fouriki and Jon Dobson
Materials 2013, 6(1), 255-264; https://doi.org/10.3390/ma6010255 - 18 Jan 2013
Cited by 24 | Viewed by 8301
Abstract
The objective of this work was to examine the potential of oscillating nanomagnetic gene transfection systems (magnefect-nano™) for improving the transfection efficiency of NIH3T3 mouse embryonic fibroblasts (MEFs) in comparison to other non-viral transfection techniques—static magnetofection™ and the cationic lipid agent, Lipofectamine 2000™. [...] Read more.
The objective of this work was to examine the potential of oscillating nanomagnetic gene transfection systems (magnefect-nano™) for improving the transfection efficiency of NIH3T3 mouse embryonic fibroblasts (MEFs) in comparison to other non-viral transfection techniques—static magnetofection™ and the cationic lipid agent, Lipofectamine 2000™. Magnetic nanoparticles (MNPs) associated with the plasmid coding for green fluorescent protein (GFP) were used to transfect NIH3T3 cells. The magnefect-nano system was evaluated for transfection efficiency, and any potential associated effects on cell viability were investigated. MNPs associated with the plasmid coding for GFP were efficiently delivered into NIH3T3 cells, and the magnefect-nano system significantly enhanced overall transfection efficiency in comparison to lipid-mediated gene delivery. MNP dosage used in this work was not found to affect the cell viability and/or morphology of the cells. Non-viral transfection using MNPs and the magnefect-nano system can be used to transfect NIH3T3 cells and direct reporter gene delivery, highlighting the wide potential of nanomagnetic gene transfection in gene therapy. Full article
(This article belongs to the Special Issue Advances in Nanoscale Biomaterials)
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211 KiB  
Article
Modeling the Microstructure Curvature of Boron-Doped Silicon in Bulk Micromachined Accelerometer
by Wu Zhou, Huijun Yu, Bei Peng, Huaqin Shen, Xiaoping He and Wei Su
Materials 2013, 6(1), 244-254; https://doi.org/10.3390/ma6010244 - 15 Jan 2013
Cited by 13 | Viewed by 5851
Abstract
Microstructure curvature, or buckling, is observed in the micromachining of silicon sensors because of the doping of impurities for realizing certain electrical and mechanical processes. This behavior can be a key source of error in inertial sensors. Therefore, identifying the factors that influence [...] Read more.
Microstructure curvature, or buckling, is observed in the micromachining of silicon sensors because of the doping of impurities for realizing certain electrical and mechanical processes. This behavior can be a key source of error in inertial sensors. Therefore, identifying the factors that influence the buckling value is important in designing MEMS devices. In this study, the curvature in the proof mass of an accelerometer is modeled as a multilayered solid model. Modeling is performed according to the characteristics of the solid diffusion mechanism in the bulk-dissolved wafer process (BDWP) based on the self-stopped etch technique. Moreover, the proposed multilayered solid model is established as an equivalent composite structure formed by a group of thin layers that are glued together. Each layer has a different Young’s modulus value and each undergoes different volume shrinkage strain owing to boron doping in silicon. Observations of five groups of proof mass blocks of accelerometers suggest that the theoretical model is effective in determining the buckling value of a fabricated structure. Full article
(This article belongs to the Special Issue Advances in Microelectromechanical Systems (MEMS) Materials)
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10294 KiB  
Review
A Review on the Synthesis and Applications of Mesostructured Transition Metal Phosphates
by Ronghe Lin and Yunjie Ding
Materials 2013, 6(1), 217-243; https://doi.org/10.3390/ma6010217 - 15 Jan 2013
Cited by 82 | Viewed by 9978
Abstract
Considerable efforts have been devoted to extending the range of the elemental composition of mesoporous materials since the pioneering work of the M41S family of ordered mesoporous silica by Mobil researchers. The synthesis of transition metal-containing mesostructured materials with large surface area and [...] Read more.
Considerable efforts have been devoted to extending the range of the elemental composition of mesoporous materials since the pioneering work of the M41S family of ordered mesoporous silica by Mobil researchers. The synthesis of transition metal-containing mesostructured materials with large surface area and high porosity has drawn great attention for its potential applications in acid and redox catalysis, photocatalysis, proton conducting devices, environmental restoration and so on. Thus, various transition metals-containing mesoporous materials, including transition metal-substituted mesoporous silicates, mesostructured transition metal oxides and transition metal phosphates (TMP), have been documented in the literature. Among these, mesostructured TMP materials are less studied, but possess some unique features, partly because of the easy and facile functionalization of PO4 and/or P–OH groups, rendering them interesting functional materials. This review first introduced the general synthesis strategies for manufacturing mesostructured TMP materials, as well as advantages and disadvantages of the respective method; then, we surveyed the ongoing developments of fabrication and application of the TMP materials in three groups on the basis of their components and application fields. Future perspectives on existing problems related to the present synthesis routes and further modifying of the functional groups for the purpose of tailoring special physical-chemical properties to meet wide application requirements were also provided in the last part. Full article
(This article belongs to the Special Issue Advances in Mesoporous Materials)
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422 KiB  
Article
Comparative Study of Loading of Anodic Porous Alumina with Silver Nanoparticles Using Different Methods
by Sanjay Thorat, Alberto Diaspro, Alice Scarpellini, Mauro Povia and Marco Salerno
Materials 2013, 6(1), 206-216; https://doi.org/10.3390/ma6010206 - 14 Jan 2013
Cited by 21 | Viewed by 6035
Abstract
Three different routes were used to infiltrate the pores of anodic porous alumina templates with silver nanoparticles, selected as an example of a bioactive agent. The three methods present a continuous grading from more physical to more chemical character, starting from ex situ [...] Read more.
Three different routes were used to infiltrate the pores of anodic porous alumina templates with silver nanoparticles, selected as an example of a bioactive agent. The three methods present a continuous grading from more physical to more chemical character, starting from ex situ filling of the pores with pre-existing particles, moving on to in situ formation of particles in the pores by bare calcination and ending with in situ calcination following specific chemical reactions. The resulting presence of silver inside the pores was assessed by means of energy dispersive X-ray spectroscopy and X-ray diffraction. The number and the size of nanoparticles were evaluated by scanning electron microscopy of functionalized alumina cross-sections, followed by image analysis. It appears that the best functionalization results are obtained with the in situ chemical procedure, based on the prior formation of silver ion complex by means of ammonia, followed by reduction with an excess amount of acetaldehyde. Elution of the silver content from the chemically functionalized alumina into phosphate buffer saline has also been examined, demonstrating a sustained release of silver over time, up to 15 h. Full article
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490 KiB  
Article
Hardness and Elastic Modulus on Six-Fold Symmetry Gold Nanoparticles
by Manuel Ramos, Luis Ortiz-Jordan, Abel Hurtado-Macias, Sergio Flores, José T. Elizalde-Galindo, Carmen Rocha, Brenda Torres, Maryam Zarei-Chaleshtori and Russell R. Chianelli
Materials 2013, 6(1), 198-205; https://doi.org/10.3390/ma6010198 - 14 Jan 2013
Cited by 35 | Viewed by 8601
Abstract
The chemical synthesis of gold nanoparticles (NP) by using gold (III) chloride trihydrate (HAuCl∙3H2O) and sodium citrate as a reducing agent in aqueous conditions at 100 °C is presented here. Gold nanoparticles areformed by a galvanic replacement mechanism as described by [...] Read more.
The chemical synthesis of gold nanoparticles (NP) by using gold (III) chloride trihydrate (HAuCl∙3H2O) and sodium citrate as a reducing agent in aqueous conditions at 100 °C is presented here. Gold nanoparticles areformed by a galvanic replacement mechanism as described by Lee and Messiel. Morphology of gold-NP was analyzed by way of high-resolution transmission electron microscopy; results indicate a six-fold icosahedral symmetry with an average size distribution of 22 nm. In order to understand the mechanical behaviors, like hardness and elastic moduli, gold-NP were subjected to nanoindentation measurements—obtaining a hardness value of 1.72 GPa and elastic modulus of 100 GPa in a 3–5 nm of displacement at the nanoparticle’s surface. Full article
(This article belongs to the Special Issue Metal Nanoparticles 2012)
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263 KiB  
Article
Nanocrystalline Akaganeite as Adsorbent for Surfactant Removal from Aqueous Solutions
by George Z. Kyzas, Efrosyni N. Peleka and Eleni A. Deliyanni
Materials 2013, 6(1), 184-197; https://doi.org/10.3390/ma6010184 - 10 Jan 2013
Cited by 30 | Viewed by 5840
Abstract
The present study presents the effective use of nanocrystalline akaganeite for the adsorption of an anionic (SDS), a cationic (CTAB), and a nonionic (tween80) surfactant from wastewater. Equilibrium experiments, as well as thermodynamic analysis, were performed. The maximum SDS adsorption occurs at the [...] Read more.
The present study presents the effective use of nanocrystalline akaganeite for the adsorption of an anionic (SDS), a cationic (CTAB), and a nonionic (tween80) surfactant from wastewater. Equilibrium experiments, as well as thermodynamic analysis, were performed. The maximum SDS adsorption occurs at the lowest pH value (5), the opposite is observed for CTAB (pH = 11), while for tween80, the change of pH value did not affect the adsorption. The equilibrium data could be described by Freundlich and Langmuir isotherms. The maximum adsorption capacity at 25 °C (pH = 8) was 823.96 mg/g for SDS, 1007.93 mg/g for CTAB, and 699.03 mg/g for tween80. The thermodynamic parameters revealed the exothermic and spontaneity nature of the process. Also, FTIR measurements established that surfactants are adsorbed on the surface of akaganeite, replacing adsorbed water. Full article
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1281 KiB  
Review
Recent Progress in Advanced Materials for Lithium Ion Batteries
by Jiajun Chen
Materials 2013, 6(1), 156-183; https://doi.org/10.3390/ma6010156 - 10 Jan 2013
Cited by 293 | Viewed by 22063
Abstract
The development and commercialization of lithium ion batteries is rooted in material discovery. Promising new materials with high energy density are required for achieving the goal toward alternative forms of transportation. Over the past decade, significant progress and effort has been made in [...] Read more.
The development and commercialization of lithium ion batteries is rooted in material discovery. Promising new materials with high energy density are required for achieving the goal toward alternative forms of transportation. Over the past decade, significant progress and effort has been made in developing the new generation of Li-ion battery materials. In the review, I will focus on the recent advance of tin- and silicon-based anode materials. Additionally, new polyoxyanion cathodes, such as phosphates and silicates as cathode materials, will also be discussed. Full article
(This article belongs to the Special Issue Advanced Materials for Lithium Ion Batteries)
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1731 KiB  
Article
Design of High Impedance Electromagnetic Surfaces for Mutual Coupling Reduction in Patch Antenna Array
by Mohammad Tariqul Islam and Md. Shahidul Alam
Materials 2013, 6(1), 143-155; https://doi.org/10.3390/ma6010143 - 07 Jan 2013
Cited by 34 | Viewed by 8240
Abstract
A compact planar meander-bridge high impedance electromagnetic structure (MBHIES) was designed and its bandgap characteristics, mutual coupling reduction abilities were studied and compared in detail. Several parametric analyses were performed to obtain optimized design values and the transmission responses were calculated through the [...] Read more.
A compact planar meander-bridge high impedance electromagnetic structure (MBHIES) was designed and its bandgap characteristics, mutual coupling reduction abilities were studied and compared in detail. Several parametric analyses were performed to obtain optimized design values and the transmission responses were calculated through the suspended microstrip line and waveguide simulation methods. The achieved bandgap is 2.3 GHz (2.55–4.85 GHz) with −61 dB minimum transmission coefficient level at the center frequency of 3.6 GHz. To see the effectiveness, the proposed design was inserted between a microstrip patch antenna array which operates at 3.8 GHz and whose operating bandwidth falls within the MBHIES bandgap. The surface wave suppression phenomenon was analyzed and simulated results are verified by measuring the fabricated prototypes, both are in good agreement. The configuration reduced the mutual coupling by 20.69 dB in simulation and 19.18 dB in measurement, without affecting the radiation characteristics of the array but increasing the gain slightly. Full article
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1035 KiB  
Review
Photo-Responsive Shape-Memory and Shape-Changing Liquid-Crystal Polymer Networks
by Danish Iqbal and Muhammad Haris Samiullah
Materials 2013, 6(1), 116-142; https://doi.org/10.3390/ma6010116 - 02 Jan 2013
Cited by 125 | Viewed by 18391
Abstract
“Surrounding matters” is a phrase that has become more significant in recent times when discussing polymeric materials. Although regular polymers do respond to external stimuli like softening of material at higher temperatures, that response is gradual and linear in nature. Smart polymers (SPs) [...] Read more.
“Surrounding matters” is a phrase that has become more significant in recent times when discussing polymeric materials. Although regular polymers do respond to external stimuli like softening of material at higher temperatures, that response is gradual and linear in nature. Smart polymers (SPs) or stimuli-responsive polymers (SRPs) behave differently to those external stimuli, as their behavior is more rapid and nonlinear in nature and even a small magnitude of external stimulus can cause noticeable changes in their shape, size, color or conductivity. Of these SRPs, two types of SPs with the ability to actively change can be differentiated: shape-memory polymers and shape-changing polymers. The uniqueness of these materials lies not only in the fast macroscopic changes occurring in their structure but also in that some of these shape changes are reversible. This paper presents a brief review of current progress in the area of light activated shape-memory polymers and shape-changing polymers and their possible field of applications. Full article
(This article belongs to the Special Issue Stimuli-Responsive Materials)
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230 KiB  
Review
Ethylene Formation by Catalytic Dehydration of Ethanol with Industrial Considerations
by Denise Fan, Der-Jong Dai and Ho-Shing Wu
Materials 2013, 6(1), 101-115; https://doi.org/10.3390/ma6010101 - 28 Dec 2012
Cited by 154 | Viewed by 20915
Abstract
Ethylene is the primary component in most plastics, making it economically valuable. It is produced primarily by steam-cracking of hydrocarbons, but can alternatively be produced by the dehydration of ethanol, which can be produced from fermentation processes using renewable substrates such as glucose, [...] Read more.
Ethylene is the primary component in most plastics, making it economically valuable. It is produced primarily by steam-cracking of hydrocarbons, but can alternatively be produced by the dehydration of ethanol, which can be produced from fermentation processes using renewable substrates such as glucose, starch and others. Due to rising oil prices, researchers now look at alternative reactions to produce green ethylene, but the process is far from being as economically competitive as using fossil fuels. Many studies have investigated catalysts and new reaction engineering technologies to increase ethylene yield and to lower reaction temperature, in an effort to make the reaction applicable in industry and most cost-efficient. This paper presents various lab synthesized catalysts, reaction conditions, and reactor technologies that achieved high ethylene yield at reasonable reaction temperatures, and evaluates their practicality in industrial application in comparison with steam-cracking plants. The most promising were found to be a nanoscale catalyst HZSM-5 with 99.7% ethylene selectivity at 240 °C and 630 h lifespan, using a microreactor technology with mechanical vapor recompression, and algae-produced ethanol to make ethylene. Full article
(This article belongs to the Special Issue Advances in Catalytic Materials)
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3197 KiB  
Article
Hydrazine-Assisted Formation of Indium Phosphide (InP)-Based Nanowires and Core-Shell Composites
by Greta R. Patzke, Roman Kontic, Zeinab Shiolashvili, Nino Makhatadze and David Jishiashvili
Materials 2013, 6(1), 85-100; https://doi.org/10.3390/ma6010085 - 27 Dec 2012
Cited by 6 | Viewed by 6904
Abstract
Indium phosphide nanowires (InP NWs) are accessible at 440 °C from a novel vapor phase deposition approach from crystalline InP sources in hydrazine atmospheres containing 3 mol % H2O. Uniform zinc blende (ZB) InP NWs with diameters around 20 nm and [...] Read more.
Indium phosphide nanowires (InP NWs) are accessible at 440 °C from a novel vapor phase deposition approach from crystalline InP sources in hydrazine atmospheres containing 3 mol % H2O. Uniform zinc blende (ZB) InP NWs with diameters around 20 nm and lengths up to several tens of micrometers are preferably deposited on Si substrates. InP particle sizes further increase with the deposition temperature. The straightforward protocol was extended on the one-step formation of new core-shell InP–Ga NWs from mixed InP/Ga source materials. Composite nanocables with diameters below 20 nm and shells of amorphous gallium oxide are obtained at low deposition temperatures around 350 °C. Furthermore, InP/Zn sources afford InP NWs with amorphous Zn/P/O-coatings at slightly higher temperatures (400 °C) from analogous setups. At 450 °C, the smooth outer layer of InP-Zn NWs is transformed into bead-shaped coatings. The novel combinations of the key semiconductor InP with isotropic insulator shell materials open up interesting application perspectives in nanoelectronics. Full article
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207 KiB  
Article
Thermal Annealing Effect on Optical Properties of Binary TiO2-SiO2 Sol-Gel Coatings
by Xiaodong Wang, Guangming Wu, Bin Zhou and Jun Shen
Materials 2013, 6(1), 76-84; https://doi.org/10.3390/ma6010076 - 24 Dec 2012
Cited by 46 | Viewed by 8814
Abstract
TiO2-SiO2 binary coatings were deposited by a sol-gel dip-coating method using tetrabutyl titanate and tetraethyl orthosilicate as precursors. The structure and chemical composition of the coatings annealed at different temperatures were analyzed by Raman spectroscopy and Fourier Transform Infrared (FTIR) [...] Read more.
TiO2-SiO2 binary coatings were deposited by a sol-gel dip-coating method using tetrabutyl titanate and tetraethyl orthosilicate as precursors. The structure and chemical composition of the coatings annealed at different temperatures were analyzed by Raman spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. The refractive indices of the coatings were calculated from the measured transmittance and reflectance spectra. An increase in refractive index with the high temperature thermal annealing process was observed. The Raman and FTIR results indicate that the refractive index variation is due to changes in the removal of the organic component, phase separation and the crystal structure of the binary coatings. Full article
(This article belongs to the Special Issue Advances in Sol-gel Derived Materials)
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501 KiB  
Article
Morphological Change of Heat Treated Bovine Bone: A Comparative Study
by Sumit Pramanik, Asyikin Sasha Mohd Hanif, Belinda Pingguan-Murphy and Noor Azuan Abu Osman
Materials 2013, 6(1), 65-75; https://doi.org/10.3390/ma6010065 - 21 Dec 2012
Cited by 47 | Viewed by 6826
Abstract
In this work, untreated bovine cortical bones (BCBs) were exposed to a range of heat treatments in order to determine at which temperature the apatite develops an optimum morphology comprising porous nano hydroxyapatite (nanoHAp) crystals. Rectangular specimens (10 mm × 10 mm × [...] Read more.
In this work, untreated bovine cortical bones (BCBs) were exposed to a range of heat treatments in order to determine at which temperature the apatite develops an optimum morphology comprising porous nano hydroxyapatite (nanoHAp) crystals. Rectangular specimens (10 mm × 10 mm × 3–5 mm) of BCB were prepared, being excised in normal to longitudinal and transverse directions. Specimens were sintered at up to 900 °C under ambient pressure in order to produce apatites by two steps sintering. The samples were characterized by thermogravimetric analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) attached to an energy-dispersive X-ray spectroscopy detector. For the first time, morphology of the HAp particles was predicted by XRD, and it was verified by SEM. The results show that an equiaxed polycrystalline HAp particle with uniform porosity was produced at 900 °C. It indicates that a porous nanoHAp achieved by sintering at 900 °C can be an ideal candidate as an in situ scaffold for load-bearing tissue applications. Full article
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1791 KiB  
Article
Molecular Dynamics of Poly(Ethylene Glycol) Intercalated in Clay, Studied Using 13C Solid-State NMR
by Roberto W. A. Franco, Carlos A. Brasil, Gerson L. Mantovani, Eduardo R. de Azevedo and Tito J. Bonagamba
Materials 2013, 6(1), 47-64; https://doi.org/10.3390/ma6010047 - 21 Dec 2012
Cited by 8 | Viewed by 6096
Abstract
In this study, Cross-Polarization Magic-angle Spinning CP/MAS, 2D Exchange, Centerband-Only Detection of Exchange (CODEX), and Separated-Local-Field (SLF) NMR experiments were used to study the molecular dynamics of poly(ethylene glycol) (PEG) inside Hectorite/PEG intercalation compounds in both single- and double-layer configurations. The results revealed [...] Read more.
In this study, Cross-Polarization Magic-angle Spinning CP/MAS, 2D Exchange, Centerband-Only Detection of Exchange (CODEX), and Separated-Local-Field (SLF) NMR experiments were used to study the molecular dynamics of poly(ethylene glycol) (PEG) inside Hectorite/PEG intercalation compounds in both single- and double-layer configurations. The results revealed that the overall amplitude of the motions of the PEG chain in the single-layer configuration is considerably smaller than that observed for the double-layer intercalation compound. This result indicates that the effect of having the polymer chain interacting with both clay platelets is to produce a substantial decrease in the motional amplitudes of those chains. The presence of these dynamically restricted segments might be explained by the presence of anchoring points between the clay platelets and the PEG oxygen atoms, which was induced by the Na+ cations. By comparing the PEG motional amplitudes of the double-layered nanocomposites composed of polymers with different molecular weights, a decrease in the motional amplitude for the smaller PEG chain was observed, which might also be understood using the presence of anchoring points. Full article
(This article belongs to the Special Issue NMR in Materials Science)
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1305 KiB  
Article
The Surface of Nanoparticle Silicon as Studied by Solid-State NMR
by Rebecca A. Faulkner, Joseph A. DiVerdi, Yuan Yang, Takeshi Kobayashi and Gary E. Maciel
Materials 2013, 6(1), 18-46; https://doi.org/10.3390/ma6010018 - 20 Dec 2012
Cited by 55 | Viewed by 9559
Abstract
The surface structure and adjacent interior of commercially available silicon nanopowder (np-Si) was studied using multinuclear, solid-state NMR spectroscopy. The results are consistent with an overall picture in which the bulk of the np-Si interior consists of highly ordered (“crystalline”) [...] Read more.
The surface structure and adjacent interior of commercially available silicon nanopowder (np-Si) was studied using multinuclear, solid-state NMR spectroscopy. The results are consistent with an overall picture in which the bulk of the np-Si interior consists of highly ordered (“crystalline”) silicon atoms, each bound tetrahedrally to four other silicon atoms. From a combination of 1H, 29Si and 2H magic-angle-spinning (MAS) NMR results and quantum mechanical 29Si chemical shift calculations, silicon atoms on the surface of “as-received” np-Si were found to exist in a variety of chemical structures, with apparent populations in the order (a) (Si–O–)3Si–H > (b) (Si–O–)3SiOH > (c) (HO–)nSi(Si)m(–OSi)4−m−n ≈ (d) (Si–O–)2Si(H)OH > (e) (Si–O–)2Si(–OH)2 > (f) (Si–O–)4Si, where Si stands for a surface silicon atom and Si represents another silicon atom that is attached to Si by either a Si–Si bond or a Si–O–Si linkage. The relative populations of each of these structures can be modified by chemical treatment, including with O2 gas at elevated temperature. A deliberately oxidized sample displays an increased population of (Si–O–)3Si–H, as well as (Si–O–)3SiOH sites. Considerable heterogeneity of some surface structures was observed. A combination of 1H and 2H MAS experiments provide evidence for a substantial population of silanol (Si–OH) moieties, some of which are not readily H-exchangeable, along with the dominant Si–H sites, on the surface of “as-received” np-Si; the silanol moieties are enhanced by deliberate oxidation. An extension of the DEPTH background suppression method is also demonstrated that permits measurement of the T2 relaxation parameter simultaneously with background suppression. Full article
(This article belongs to the Special Issue NMR in Materials Science)
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356 KiB  
Article
A Refined Finite Element Formulation for the Microstructure-Dependent Analysis of Two-Dimensional (2D) Lattice Materials
by Geminiano Mancusi and Luciano Feo
Materials 2013, 6(1), 1-17; https://doi.org/10.3390/ma6010001 - 20 Dec 2012
Cited by 15 | Viewed by 4910
Abstract
A finite element approximation is proposed for the dynamic analysis of two-dimensional (2D) lattice materials. The unit cell is modeled by means of a defined number of shear deformable micro-beams. The main innovative feature concerns the presence of a microstructure-dependent scale length, which [...] Read more.
A finite element approximation is proposed for the dynamic analysis of two-dimensional (2D) lattice materials. The unit cell is modeled by means of a defined number of shear deformable micro-beams. The main innovative feature concerns the presence of a microstructure-dependent scale length, which allows the consideration of the so called size-effect that can be highly relevant, due to the characteristics of the lattice at the local scale. Some numerical results show the influence of the microstructure parameter on the dynamic behavior of two-dimensional lattice materials. Full article
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