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Materials, Volume 5, Issue 2 (February 2012), Pages 210-363

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Research

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Open AccessArticle Stresses and Displacements in Functionally Graded Materials of Semi-Infinite Extent Induced by Rectangular Loadings
Materials 2012, 5(2), 210-226; doi:10.3390/ma5020210
Received: 24 November 2011 / Revised: 16 January 2012 / Accepted: 17 January 2012 / Published: 30 January 2012
Cited by 1 | PDF Full-text (330 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the stress and displacement fields in a functionally graded material (FGM) caused by a load. The FGM is a graded material of Si3N4-based ceramics and is assumed to be of semi-infinite extent. The load is [...] Read more.
This paper presents the stress and displacement fields in a functionally graded material (FGM) caused by a load. The FGM is a graded material of Si3N4-based ceramics and is assumed to be of semi-infinite extent. The load is a distributed loading over a rectangular area that is parallel to the external surface of the FGM and either on its external surface or within its interior space. The point-load analytical solutions or so-called Yue’s solutions are used for the numerical integration over the distributed loaded area. The loaded area is discretized into 200 small equal-sized rectangular elements. The numerical integration is carried out with the regular Gaussian quadrature. Weak and strong singular integrations encountered when the field points are located on the loaded plane, are resolved with the classical methods in boundary element analysis. The numerical integration results have high accuracy. Full article
(This article belongs to the Special Issue Advances in Functionally Graded Materials)
Open AccessArticle Optical Properties of Mg, Fe, Co-Doped Near-Stoichiometric LiTaO3 Single Crystals
Materials 2012, 5(2), 227-238; doi:10.3390/ma5020227
Received: 17 November 2011 / Revised: 17 January 2012 / Accepted: 19 January 2012 / Published: 30 January 2012
Cited by 5 | PDF Full-text (2046 KB) | HTML Full-text | XML Full-text
Abstract
Mg, Fe co-doped near-stoichiometric lithium tantalite (SLT) single crystals were grown by employing the zone-leveling Czochralski (ZLCz) technique. The optical properties, holographic parameters, as well as the composition of the grown crystals were measured. It was found that the Li/Ta ratio decreased [...] Read more.
Mg, Fe co-doped near-stoichiometric lithium tantalite (SLT) single crystals were grown by employing the zone-leveling Czochralski (ZLCz) technique. The optical properties, holographic parameters, as well as the composition of the grown crystals were measured. It was found that the Li/Ta ratio decreased with the doping of Mg and Fe ions. A red shift was observed in absorption spectrum for the Mg, Fe co-doped crystals compared to the undoped and Mg-doped ones. The effect of the iron ions (Fe2+ and Fe3+) was further discussed based on the specified absorption bands. Moreover, the occupation mechanism for the defects was discussed by using the IR absorption spectrum, which was attributed to the FeTa3− defects in the highly Fe-doped crystal. In addition, the holographic parameters were also found to be improved with a higher Fe/Ta ratio in the crystals. Full article
(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)
Open AccessArticle Aligned Layers of Silver Nano-Fibers
Materials 2012, 5(2), 239-247; doi:10.3390/ma5020239
Received: 5 January 2012 / Revised: 23 January 2012 / Accepted: 28 January 2012 / Published: 1 February 2012
Cited by 2 | PDF Full-text (483 KB) | HTML Full-text | XML Full-text
Abstract
We describe a new dichroic polarizers made by ordering silver nano-fibers to aligned layers. The aligned layers consist of nano-fibers and self-assembled molecular aggregates of lyotropic liquid crystals. Unidirectional alignment of the layers is achieved by means of mechanical shearing. Aligned layers [...] Read more.
We describe a new dichroic polarizers made by ordering silver nano-fibers to aligned layers. The aligned layers consist of nano-fibers and self-assembled molecular aggregates of lyotropic liquid crystals. Unidirectional alignment of the layers is achieved by means of mechanical shearing. Aligned layers of silver nano-fibers are partially transparent to a linearly polarized electromagnetic radiation. The unidirectional alignment and density of the silver nano-fibers determine degree of polarization of transmitted light. The aligned layers of silver nano-fibers might be used in optics, microwave applications, and organic electronics. Full article
(This article belongs to the Special Issue Photonic Materials and Applications)
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Open AccessArticle Molecular Beam-Thermal Desorption Spectrometry (MB-TDS) Monitoring of Hydrogen Desorbed from Storage Fuel Cell Anodes
Materials 2012, 5(2), 248-257; doi:10.3390/ma5020248
Received: 22 December 2011 / Revised: 28 January 2012 / Accepted: 31 January 2012 / Published: 6 February 2012
PDF Full-text (386 KB) | HTML Full-text | XML Full-text
Abstract
Different types of experimental studies are performed using the hydrogen storage alloy (HSA) MlNi3.6Co0.85Al0.3Mn0.3 (Ml: La-rich mischmetal), chemically surface treated, as the anode active material for application in a proton exchange membrane fuel cell (PEMFC). [...] Read more.
Different types of experimental studies are performed using the hydrogen storage alloy (HSA) MlNi3.6Co0.85Al0.3Mn0.3 (Ml: La-rich mischmetal), chemically surface treated, as the anode active material for application in a proton exchange membrane fuel cell (PEMFC). The recently developed molecular beam—thermal desorption spectrometry (MB-TDS) technique is here reported for detecting the electrochemical hydrogen uptake and release by the treated HSA. The MB-TDS allows an accurate determination of the hydrogen mass absorbed into the hydrogen storage alloy (HSA), and has significant advantages in comparison with the conventional TDS method. Experimental data has revealed that the membrane electrode assembly (MEA) using such chemically treated alloy presents an enhanced surface capability for hydrogen adsorption. Full article
(This article belongs to the Special Issue Recent Advances in Hydrogen Storage Materials)
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Open AccessArticle Carbon Nanotubes: Solution for the Therapeutic Delivery of siRNA?
Materials 2012, 5(2), 278-301; doi:10.3390/ma5020278
Received: 1 December 2011 / Revised: 2 February 2012 / Accepted: 6 February 2012 / Published: 13 February 2012
Cited by 15 | PDF Full-text (1707 KB) | HTML Full-text | XML Full-text
Abstract
Carbon nanotubes have many unique physical and chemical properties that are being widely explored for potential applications in biomedicine especially as transporters of drugs, proteins, DNA and RNA into cells. Specifically, single-walled carbon nanotubes (SWCNT) have been shown to deliver siRNA to [...] Read more.
Carbon nanotubes have many unique physical and chemical properties that are being widely explored for potential applications in biomedicine especially as transporters of drugs, proteins, DNA and RNA into cells. Specifically, single-walled carbon nanotubes (SWCNT) have been shown to deliver siRNA to tumors in vivo. The low toxicity, the excellent membrane penetration ability, the protection afforded against blood breakdown of the siRNA payload and the good biological activity seen in vivo suggests that SWCNT may become universal transfection vehicles for siRNA and other RNAs for therapeutic applications. This paper will introduce a short review of a number of therapeutic applications for carbon nanotubes and provide recent data suggesting SWCNT are an excellent option for the delivery of siRNA clinically. Full article
(This article belongs to the Special Issue Carbon Nanotubes: Synthesis, Characterization and Applications)
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Open AccessArticle Synthesis and Properties of Poly(Isothianaphthene Methine)s with Chiral Alkyl Chain
Materials 2012, 5(2), 317-326; doi:10.3390/ma5020317
Received: 29 December 2011 / Revised: 21 January 2012 / Accepted: 6 February 2012 / Published: 16 February 2012
Cited by 5 | PDF Full-text (308 KB) | HTML Full-text | XML Full-text
Abstract
We synthesized poly(isothianaphthene methine)s with chiral alkyl chains in the substituent. Resultant polymers are soluble in THF and CHCl3. Structure of the polymers was characterized with FT-IR, FT-Raman, and UV-Vis-NIR optical absorption spectroscopy. They showed low-bandgap both in solution and [...] Read more.
We synthesized poly(isothianaphthene methine)s with chiral alkyl chains in the substituent. Resultant polymers are soluble in THF and CHCl3. Structure of the polymers was characterized with FT-IR, FT-Raman, and UV-Vis-NIR optical absorption spectroscopy. They showed low-bandgap both in solution and in a form of film. Optical activity of the polymers was confirmed with optical rotatory dispersion. Doping effects on the polymer were also examined with UV-Vis-NIR spectroscopy and ESR measurement. Full article
Open AccessArticle Influence of Carbon Nanotubes on Thermal Stability of Water-Dispersible Nanofibrillar Polyaniline/Nanotube Composite
Materials 2012, 5(2), 327-335; doi:10.3390/ma5020327
Received: 2 December 2011 / Accepted: 9 February 2012 / Published: 17 February 2012
Cited by 2 | PDF Full-text (555 KB) | HTML Full-text | XML Full-text
Abstract
Significant influence on the thermal stability of polyaniline (PANI) in the presence of multi-walled carbon nanotubes (MWCNTs) is reported. By means of in-situ rapid mixing approach, water-dispersible nanofibrillar PANI and composites, consisting of MWCNTs uniformly coated with PANI in the state of [...] Read more.
Significant influence on the thermal stability of polyaniline (PANI) in the presence of multi-walled carbon nanotubes (MWCNTs) is reported. By means of in-situ rapid mixing approach, water-dispersible nanofibrillar PANI and composites, consisting of MWCNTs uniformly coated with PANI in the state of emeraldine salt, with a well-defined core-shell heterogeneous structure, were prepared. The de-protonation process in PANI occurs at a lower temperature under the presence of MWCNTs on the polyaniline composite upon thermal treatment. However, it is found that the presence of MWCNTs significantly enhances the thermal stability of PANI’s backbone upon exposure to laser irradiation, which can be ascribed to the core-shell heterogeneous structure of the composite of MWCNTs and PANI, and the high thermal conductivity of MWCNTs. Full article
(This article belongs to the Special Issue Carbon Nanotubes: Synthesis, Characterization and Applications)
Open AccessArticle Challenges and Strategies in the Synthesis of Mesoporous Alumina Powders and Hierarchical Alumina Monoliths
Materials 2012, 5(2), 336-349; doi:10.3390/ma5020336
Received: 14 December 2011 / Revised: 13 February 2012 / Accepted: 13 February 2012 / Published: 20 February 2012
Cited by 10 | PDF Full-text (1182 KB) | HTML Full-text | XML Full-text
Abstract
A new rapid, very simple and one-step sol-gel strategy for the large-scale preparation of highly porous γ-Al2O3 is presented. The resulting mesoporous alumina materials feature high surface areas (400 m2 g−1), large pore volumes (0.8 mL [...] Read more.
A new rapid, very simple and one-step sol-gel strategy for the large-scale preparation of highly porous γ-Al2O3 is presented. The resulting mesoporous alumina materials feature high surface areas (400 m2 g−1), large pore volumes (0.8 mL g−1) and the γ-Al2O3 phase is obtained at low temperature (500 °C). The main advantages and drawbacks of different preparations of mesoporous alumina materials exhibiting high specific surface areas and large pore volumes such as surfactant-nanostructured alumina, sol-gel methods and hierarchically macro-/mesoporous alumina monoliths have been analyzed and compared. The most reproducible synthesis of mesoporous alumina are given. Evaporation-Induced Self-Assembly (EISA) is the sole method to lead to nanostructured mesoporous alumina by direct templating, but it is a difficult method to scale-up. Alumina featuring macro- and mesoporosity in monolithic shape is a very promising material for in flow applications; an optimized synthesis is described. Full article
(This article belongs to the Special Issue Advances in Porous Inorganic Materials)
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Review

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Open AccessReview Ceramic Laser Materials
Materials 2012, 5(2), 258-277; doi:10.3390/ma5020258
Received: 26 December 2011 / Accepted: 1 February 2012 / Published: 9 February 2012
Cited by 40 | PDF Full-text (3948 KB) | HTML Full-text | XML Full-text
Abstract
Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic [...] Read more.
Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements. Full article
(This article belongs to the Special Issue Laser Materials)
Open AccessReview Sorbate Transport in Carbon Molecular Sieve Membranes and FAU/EMT Intergrowth by Diffusion NMR
Materials 2012, 5(2), 302-316; doi:10.3390/ma5020302
Received: 19 January 2012 / Revised: 9 February 2012 / Accepted: 10 February 2012 / Published: 14 February 2012
Cited by 1 | PDF Full-text (421 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present and discuss selected results of our recent studies of sorbate self-diffusion in microporous materials. The main focus is given to transport properties of carbon molecular sieve (CMS) membranes as well as of the intergrowth of FAU-type and [...] Read more.
In this paper we present and discuss selected results of our recent studies of sorbate self-diffusion in microporous materials. The main focus is given to transport properties of carbon molecular sieve (CMS) membranes as well as of the intergrowth of FAU-type and EMT-type zeolites. CMS membranes show promise for applications in separations of mixtures of small gas molecules, while FAU/EMT intergrowth can be used as an active and selective cracking catalyst. For both types of applications diffusion of guest molecules in the micropore networks of these materials is expected to play an important role. Diffusion studies were performed by a pulsed field gradient (PFG) NMR technique that combines advantages of high field (17.6 T) NMR and high magnetic field gradients (up to 30 T/m). This technique has been recently introduced at the University of Florida in collaboration with the National Magnet Lab. In addition to a more conventional proton PFG NMR, also carbon-13 PFG NMR was used. Full article
(This article belongs to the Special Issue Diffusion in Micropores)
Open AccessReview Carbon Nanomaterials: Efficacy and Safety for Nanomedicine
Materials 2012, 5(2), 350-363; doi:10.3390/ma5020350
Received: 16 December 2011 / Revised: 11 February 2012 / Accepted: 15 February 2012 / Published: 21 February 2012
Cited by 15 | PDF Full-text (124 KB) | HTML Full-text | XML Full-text
Abstract
Carbon nanomaterials, including fullerenes, carbon nanohorns, and carbon nanotubes, are increasingly being used in various fields owing to these materials’ unique, size-dependent functions and physicochemical properties. Recently, because of their high variability and stability, carbon nanomaterials have been explored as a novel [...] Read more.
Carbon nanomaterials, including fullerenes, carbon nanohorns, and carbon nanotubes, are increasingly being used in various fields owing to these materials’ unique, size-dependent functions and physicochemical properties. Recently, because of their high variability and stability, carbon nanomaterials have been explored as a novel tool for the delivery of therapeutic molecules including peptide and nucleic acid cancer drugs. However, insufficient information is available regarding the safety of carbon nanomaterials for human health, even though such information is vital for the development of safe and effective nanomedicine technologies. In this review, we discuss currently available information regarding the safety of carbon nanomaterials in nanomedicine applications, including information obtained from our own studies; and we discuss types of carbon nanomaterials that demonstrate particular promise for safe nanomedicine technologies. Full article
(This article belongs to the Special Issue Carbon Nanotubes: Synthesis, Characterization and Applications)

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