Jasbinder Sanghera , Woohong Kim , Guillermo Villalobos , Brandon Shaw , Colin Baker , Jesse Frantz , Bryan Sadowski and Ishwar Aggarwal
Review: Ceramic Laser Materials
Materials 2012, 5(2), 258-277; doi:10.3390/ma5020258 - published online 9 February 2012
Show/Hide AbstractAbstract: 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.

Rui F. M. Lobo , Diogo M. F. Santos , Cesar A. C. Sequeira and Jorge H. F. Ribeiro
Article: 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 - published online 6 February 2012
Show/Hide AbstractAbstract: Different types of experimental studies are performed using the hydrogen storage alloy (HSA) MlNi_3.6Co_0.85Al_0.3Mn_0.3 (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.

Andrii B. Golovin , Jeremy Stromer and Liubov Kreminska
Article: Aligned Layers of Silver Nano-Fibers
Materials 2012, 5(2), 239-247; doi:10.3390/ma5020239 - published online 1 February 2012
Show/Hide AbstractAbstract: 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.

Wei Tse Hsu , Zhi Bin Chen , Chien Cheng Wu , Ravi Kant Choubey and Chung Wen Lan
Article: Optical Properties of Mg, Fe, Co-Doped Near-Stoichiometric LiTaO₃ Single Crystals
Materials 2012, 5(2), 227-238; doi:10.3390/ma5020227 - published online 30 January 2012
Show/Hide AbstractAbstract: 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 Fe_Ta³⁻ 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.

Hong-Tian Xiao and Zhong-Qi Yue
Article: 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 - published online 30 January 2012
Show/Hide AbstractAbstract: 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.

Sophia Haussener and Aldo Steinfeld
Article: Effective Heat and Mass Transport Properties of Anisotropic Porous Ceria for Solar Thermochemical Fuel Generation
Materials 2012, 5(1), 192-209; doi:10.3390/ma5010192 - published online 19 January 2012
Show/Hide AbstractAbstract: High-resolution X-ray computed tomography is employed to obtain the exact 3D geometrical configuration of porous anisotropic ceria applied in solar-driven thermochemical cycles for splitting H2O and CO2. The tomography data are, in turn, used in direct pore-level numerical simulations for determining the morphological and effective heat/mass transport properties of porous ceria, namely: porosity, specific surface area, pore size distribution, extinction coefficient, thermal conductivity, convective heat transfer coefficient, permeability, Dupuit-Forchheimer coefficient, and tortuosity and residence time distributions. Tailored foam designs for enhanced transport properties are examined by means of adjusting morphologies of artificial ceria samples composed of bimodal distributed overlapping transparent spheres in an opaque medium.