RESEARCH AREA
Encapsulated Monoclinic Sulfur for Stable Cycling of Li-S Rechargeable Batteries
In the present investigation, we developed an encapsulated sulfur electrode. In the electrode design perspective, sulfur nanowires (NWs) were well aligned and completely covered by a minimal amount of carbon, and in the sulfur crystal structure perspective, a majority of sulfur adopts the uncommon monoclinic phase rather than the typical orthorhombic phase, after a heat treatment within a confi ned environment in nanometer dimensions. The electrode design in conjunction with the monoclinic crystal structure address all of the aforementioned issues and result in excellent electrical performance: a specifi c capacity reaching the theoretical value, substantial capacity retention over 1000 cycles, and rate capability with < 1 min discharge time were achieved.

Graphene-supported Na3V2(PO4)3 as a high rate cathode material for sodium-ion batteries

We report a facile synthetic strategy to improve the rate performance of Na-based electrode materials in sodium-ion batteries. Na3V2(PO4)3 (NVP) is one of the most promising cathode materials with a NASICON structure, and it has been synthesized on a graphene sheet surface using a simple method that combines sol–gel and solid-state reaction. The NVP/ graphene composite displays an excellent high-rate performance; it delivers approximately 67% of the initial 0.2 C capacity at a 30 C rate, whereas bare NVP produces only 46% of the 0.2 C capacity at a 5 C rate.

Synthesis, structure, and electrochemical Li-ion intercalation of LiRu2O4 with CaFe2O4-type structure

A new material, LiRu2O4, has been synthesized by ion-exchange reaction from NaRu2O4 that has been prepared by solid state reaction at 950 C under Ar flow. The crystal structure of LiRu2O4, isostructural with the parent NaRu2O4, has been refined by an X-ray Rietveld method.The structure belongs to CaFe2O4-type, where double chains of edge-sharing octahedral RuO6 share the corners with neighboring double chains and form tunnels in between them parallel to the shortest b-axis so that the onedimensional Li array is placed inside each of the tunnels. Detailed structural analysis indicates that the tunnel inside has more than enough space to be filled with the Li atoms. The electrochemical tests of LiRu2O4 demonstrates a reversible Li intercalation reaction at 3.2e3.5 V vs. Li/Liþ with a capacity of w80 mAhg1.
 
Electrochemical Sodium Ion Intercalation Properties of Na2.7Ru4O9 in Nonaqueous and Aqueous Electrolytes .  
Na2.7Ru4O9 was synthesized at 700–850◦C by solid-state reaction under Ar flow. It has single, double and triple chains of edge-sharing RuO6 octahedra and one-dimensional tunnels between them parallel to the b-axis, accommodating three different sites of Na1, Na2 and Na3. In an organic electrolyte (1 M NaClO4 in PC), Na2.7Ru4O9 shows three redox peaks in its cyclic voltammogram between 2.8 and 3.9 V vs. Na. In an aqueous (1 M Na2SO4) electrolyte, Na2.7Ru4O9 exhibits three anodic peaks during the first charge, similar to the behavior observed in the organic electrolyte.
 
Diffusion behavior of sodium ions in Na0.44MnO2 in aqueous and non-aqueous electrolytes
sodium ion intercalation/de-intercalation behavior of Na0.44MnO2 (NMO), which is one of the promising cathode materials for sodium batteries, is presented in both aqueous and non-aqueous electrolyte systems. The NMO samples synthesized using modified Pechini method shows better rate capability in 0.5 M sodium sulfate aqueous electrolyte system than the 1 M sodium perchlorate non-aqueous system.
 
Aluminum Nitride (AlN) Ceramics
Aluminum Nitride (AlN) has attractive thermal and electrical properties and it make AlN a very promising material for electronic substrates such as electrostatic chuck. We investigated bulk AlN crystals using Raman spectroscopy in order to characterize their defects and thermal conductivity. We studied the correlation between the width of the E2(high) phonon of AlN and lattice thermal conductivity as measured by the laser flash method. Raman spectroscopy is a good candidate for a nondestructive assessment tool for the thermal conductivity of bulk AlN ceramics.
 
TEM Study of the High-Temperature Oxidation Behavior of Hot-Pressed ZrB2–SiC Composites
The oxidation behaviors of ZrB2- 30 vol% SiC composites were investigated at 1500°C in air and under reducing conditions with oxygen partial pressures of 104 and 10−8 Pa, respectively. The oxidation of ZrB2 and SiC were analyzed using transmission electron microscopy (TEM). Due to kinetic difference of oxidation behavior, the three layers (surface silica-rich layer, oxide layer, and unreacted layer) were observed over a wide area of specimen in air, while the two layers (oxide layer, and unreacted layer) were observed over a narrow area in specimen under reducing condition. In oxide layer, the ZrB2 was oxidized to ZrO2 accompanied by division into small grains and the shape was also changed from faceted to round. This layer also consisted of amorphous SiO2 with residual SiC and found dispersed in TEM. Based on TEM analysis of ZrB2–SiC composites tested under air and low oxygen partial pressure, the ZrB2 begins to oxidize preferentially and the SiC remained without any changes at the interface between oxidized layer and unreacted layer.
 
Atomic-Resolution Imaging of the Nanoscale Origin of Toughness in Rare-  Earth Doped SiC
Ultrahigh-resolution transmission electron microscopy and atomic-scale spectroscopy are used to investigate the origin of the toughness in rare-earth doped silicon carbide (RE-SiC) by examining the mechanistic nature of the intergranular cracking events which we find to occur precisely along the RE-decorated interface between the SiC grains and the nanoscale grain-boundary phase. We conclude that, for optimal toughns are the most critical material parameters; both can be altered with judicious choice of rare-earth elements.ess, the relative elastic modulus across the grain-boundary phase and the interfacial fracture toughnes
 
One-dimensional WO3 nanorods as photoelectrodes for dye-sensitized solar cells
Tungsten oxide (WO3) nanorods were applied for the first time as photoelectrodes in dye-sensitized solar cells (DSSCs).The DSSC based on WO3 nanorods showed a short-circuit current, an open-circuit voltage, a fill factor, and a conversion efficiency of 4.66 mA/cm2, 0.383 V, 0.22, and 0.75%, respectively. The WO3 nanorod photoelectrode was treated with TiCl4 aqueous solution to improve the dye absorption and open-circuit voltage by coating the thin TiO2 layer on the WO3 nanorod surface. 
 
High Temperature Fracture Strength of SiC Coating Layer
Micro tensile test were performed to estimate the high temperature fracture strength of SiC coating layer. The tensile strength of SiC coating layer is decreasing with increasing temperature from the RT to 700°C. The temperature dependent fracture strength was related to the microstructure of SiC coating layers. SiC coatings deposited at 1300°C showed a small grain size have high stability and reliability at high temperature.