Advances in Condensed Matter Physics The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Spatially Resolved Cathodoluminescence in the Vicinity of Defects in the High-Efficiency InGaN/GaN Blue Light Emitting Diodes Mon, 01 Sep 2014 07:47:49 +0000 In addition to the standard 447 nm blue emission from the InGaN/GaN multiple quantum wells, a high-energy shoulder is clearly observed in cathodoluminescence spectra of the high-efficiency InGaN/GaN blue light emitting diodes grown on sapphire substrates by metalorganic chemical vapor deposition. Monochromatic cathodoluminescence images of the samples measured at low temperature reveal a competition between the two emissions in the vicinity of the dislocations. The high-energy emission is dominant at the regions near the dislocation cores, while the blue emission is enhanced around the dislocation edges. The high-energy emission region is considered as a potential barrier that prevents the carriers for the blue emission from nonradiatively recombining at the dislocations. Manh-Ha Doan and Jaejin Lee Copyright © 2014 Manh-Ha Doan and Jaejin Lee. All rights reserved. Influence of Codoping on the Optical Properties of ZnO Thin Films Synthesized on Glass Substrate by Chemical Bath Deposition Method Sun, 31 Aug 2014 12:07:12 +0000 Fe and K simultaneously doped ZnO thin films Zn0.99 K0.01 (Fe)x O (, 2, 3, and 4%) were synthesized by chemical bath deposition method. The XRD investigation reveals that all the doped ZnO thin films are in hexagonal wurtzite crystal structure without impurity phases. With increase in Fe concentration, the growth of thin films along c axis is evident from the XRD which indicates the increase in intensity along (002) direction. The same is visible from the surface morphology which shows the formation of hexagonal structure for higher Fe concentration. The topography shows gradual variation with Fe incorporation. The optical energy band gap obtained from the transmittance spectrum decreases from 3.42 to 3.06 eV with increase in Fe concentration indicating the red shift and this trend is consistent with the earlier experimental results. The UV emission is centered around 3.59 eV. The optical constants such as refractive index, extinction coefficient, and absorption coefficient which are essential for the optoelectronic applications were also determined. G. Shanmuganathan and I. B. Shameem Banu Copyright © 2014 G. Shanmuganathan and I. B. Shameem Banu. All rights reserved. Structural, Electronic, and Optical Properties of Functional Metal Oxides Sun, 31 Aug 2014 08:52:34 +0000 Jianhua Hao, Nian X. Sun, Jianrong Qiu, and Danyang Wang Copyright © 2014 Jianhua Hao et al. All rights reserved. The Low Temperature Specific Heat of Pr0.65Ca0.35MnO3 Mon, 25 Aug 2014 08:05:05 +0000 The low temperature specific heat of polycrystalline perovskite-type Pr0.65Ca0.35MnO3 manganese oxide has been investigated experimentally. It is found that the low temperature electron specific heat in zero magnetic field is obviously larger than that of ordinary rare-earth manganites oxide. To get the contribution of phonon to the specific heat precisely, the lattice specific heat is calculated by Debye model fitting. Results confirm that the low temperature specific heat of Pr0.65Ca0.35MnO3 is related to the itinerant electrons in ferromagnetic clusters and the disorder in the sample. Zhiyong Han and Zhenzhu Jing Copyright © 2014 Zhiyong Han and Zhenzhu Jing. All rights reserved. Laser-Induced Point Defects in Fused Silica Irradiated by UV Laser in Vacuum Sun, 17 Aug 2014 12:27:55 +0000 High-purity fused silica irradiated by third harmonic of the Nd:YAG laser in vacuum with different laser pulse parameters was studied experimentally. Laser-induced defects are investigated by UV spectroscopy, and fluorescence spectra and correlated to the structural modifications in the glass matrix through Raman spectroscopy. Results show that, for laser fluence below laser-induced damage threshold (LIDT), the absorbance and intensity of fluorescence bands increase with laser energies and/or number of laser pulses, which indicates that laser-induced defects are enhanced by laser energies and/or number of laser pulses in vacuum. The optical properties of these point defects were discussed in detail. Xiaoyan Zhou, Xinda Zhou, Jin Huang, Qiang Cheng, Fengrui Wang, Xin Ye, Xiaodong Jiang, and Weidong Wu Copyright © 2014 Xiaoyan Zhou et al. All rights reserved. Cracking Tendency Prediction of High-Performance Cementitious Materials Tue, 05 Aug 2014 09:50:29 +0000 The constraint ring test is widely used to assess the cracking potential for early-age cementitious materials. In this paper, the analytical expressions based on elastic mechanism are presented to estimate the residual stresses of the restrained mortar ring by considering the comprehensive effects of hydration heat, autogenous and drying shrinkage, creeping, and restraint. In the present analytical method, the stress field of the restrained ring is treated as the superposition of those caused by hydration heat, external restraint, autogenous and drying shrinkage, and creep. The factors including the properties of materials, environmental parameters such as relative humidity and temperature, the geometry effect of specimen, and the relative constraint effects of steel ring to mortar ring, are taken into account to predict the strain development with age of mortar. The temperature of the ring, the elastic modulus, the creep strain, and the split tensile strength are measured to validate the model. The age of cracking is predicted by comparing the estimated maximum tensile stress of the restrained mortar ring with the measured split tensile strength of specimen. The suitability of the present analytical method is assessed by comparing with the restraint ring test and a soundly good agreement is observed. Ke Chen, Hui Hu, Ke Chen, Zhaohui Chen, and Xin Wang Copyright © 2014 Ke Chen et al. All rights reserved. Dynamics and Matter-Wave Solitons in Bose-Einstein Condensates with Two- and Three-Body Interactions Tue, 05 Aug 2014 08:15:41 +0000 By means of similarity transformation, this paper proposes the matter-wave soliton solutions and dynamics of the variable coefficient cubic-quintic nonlinear Schrödinger equation arising from Bose-Einstein condensates with time-dependent two- and three-body interactions. It is found that, under the effect of time-dependent two- and three-body interaction and harmonic potential with time-dependent frequency, the density of atom condensates will gradually diminish and finally collapse. Jing Chen, Jie Yang, and Lu Zhang Copyright © 2014 Jing Chen et al. All rights reserved. First Principles Study of Cerium Monochalcogenides Mon, 21 Jul 2014 09:40:30 +0000 A theoretical investigation of structural, magnetic, electronic, and lattice dynamical properties of cerium monochalcogenides using the generalized gradient approximation (GGA) + U within ultrasoft pseudopotentials and a plane-wave basis is presented. All the calculated quantities, except the local magnetic moments, are found to be in good agreement with the experimental data. The lattice dynamical results indicate a strong chalcogenide dependence for the anomalous features of the phonon dispersions. Recep Eryiğit Copyright © 2014 Recep Eryiğit. All rights reserved. Full Aperture CO2 Laser Process to Improve Laser Damage Resistance of Fused Silica Optical Surface Thu, 17 Jul 2014 00:00:00 +0000 An improved method is presented to scan the full-aperture optical surface rapidly by using galvanometer steering mirrors. In contrast to the previous studies, the scanning velocity is faster by several orders of magnitude. The velocity is chosen to allow little thermodeposition thus providing small and uniform residual stress. An appropriate power density is set to obtain a lower processing temperature. The proper parameters can help to prevent optical surface from fracturing during operation at high laser flux. S-on-1 damage test results show that the damage threshold of scanned area is approximately 40% higher than that of untreated area. Wei Liao, Chuanchao Zhang, Xiaofen Sun, Lijuan Zhang, and Xiaodong Yuan Copyright © 2014 Wei Liao et al. All rights reserved. Laser-Induced Damage Initiation and Growth of Optical Materials Wed, 16 Jul 2014 10:26:02 +0000 The lifetime of optical components is determined by the combination of laser-induced damage initiation probability and damage propagation rate during subsequent laser shots. This paper reviews both theoretical and experimental investigations on laser-induced damage initiation and growth at the surface of optics. The damage mechanism is generally considered as thermal absorption and electron avalanche, which play dominant roles for the different laser pulse durations. The typical damage morphology in the surface of components observed in experiments is also closely related to the damage mechanism. The damage crater in thermal absorption process, which can be estimated by thermal diffusion model, is typical distortion, melting, and ablation debris often with an elevated rim caused by melted material flow and resolidification. However, damage initiated by electron avalanche is often accompanied by generation of plasma, crush, and fracture, which can be explained by thermal explosion model. Damage growth at rear surface of components is extremely severe which can be explained by several models, such as fireball growth, impact crater, brittle fracture, and electric field enhancement. All the physical effects are not independent but mutually coupling. Developing theoretical models of multiphysics coupling are an important trend for future theoretical research. Meanwhile, more attention should be paid to integrated analysis both in theory and experiment. Jingxia Yu, Xia Xiang, Shaobo He, Xiaodong Yuan, Wanguo Zheng, Haibing Lü, and Xiaotao Zu Copyright © 2014 Jingxia Yu et al. All rights reserved. Electrical and Dielectric Characterization of Bi12GeO20 Prepared by Modified Pechini Method Tue, 15 Jul 2014 10:15:27 +0000 Bismuth germanate () ceramics were produced using modified Pechini route, and the synthesis parameters, crystalline phases, microstructure, and sintering conditions were investigated. powders with submicrometric particle sizes were investigated for calcination temperatures from 400 to 600°C, with soaking times of 1 h and 5 h. Controlling the synthesis parameters, dense ceramics with two different grain sizes of 3.4 ± 0.5 µm and 5.7 ± 0.8 µm could be produced after sintering at 750°C/1 h. The electric and dielectric properties of these ceramics were determined by impedance spectroscopy (IS). From the results, it was concluded that the dielectric permittivity measured at high frequencies is insensitive to the grain size, while the AC dark conductivity presents a noticeable dependency on this feature. This behaviour was discussed on the basis of a Maxwell-Wagner interfacial relaxation, whose intensity depends directly on the volume fraction of grain boundaries in the sample. C. G. P. Moraes, F. A. A. Jesus, and Z. S. Macedo Copyright © 2014 C. G. P. Moraes et al. All rights reserved. Study on Macroscopic and Microscopic Mechanical Behavior of Magnetorheological Elastomers by Representative Volume Element Approach Thu, 10 Jul 2014 07:04:32 +0000 By using a representative volume element (RVE) approach, this paper investigates the effective mechanical properties of anisotropic magnetorheological elastomers (MREs) in which particles are aligned and form chain-like structure under magnetic field during curing. Firstly, a three-dimensional RVE in zero magnetic field is presented in ABAQUS/Standard to calculate the macroscopic mechanical properties of MREs. It is shown that the initial shear modulus of MREs increases by 56% with a 20% volume fraction of particles compared to that of pure rubber. Then by introducing the Maxwell stress tensor, a two-dimensional plane stress RVE for the MRE is developed in COMSOL Multiphysics to study its response under a magnetic field. The influences of magnetic field intensity, radius of particles, and distance between two adjacent particles on the macroscopic mechanical properties of MRE are also investigated. The results show that the shear modulus increases with the increase of the applied magnetic field intensity and the radius of particles and the decrease of the distance between two adjacent particles in a chain. The predicted numerical results are consistent with theoretical results from Mori-Tanaka model, double inclusion model, and dipole model. Shulei Sun, Xiongqi Peng, and Zaoyang Guo Copyright © 2014 Shulei Sun et al. All rights reserved. Effect of Concurrent ZnO Addition and AlF3 Reduction on the Elastic Properties of Tellurite Based Glass System Tue, 08 Jul 2014 12:03:26 +0000 New ternary zinc oxyfluorotellurite (ZOFT) with the composition --, where ; ; , has been successfully prepared by the conventional rapid melt quenching technique. Density, molar volume, and glass transition temperature have been assessed for each ZOFT glass sample. The longitudinal and transverse ultrasonic waves propagated in each glass sample were measured using a MBS8020 ultrasonic data acquisition system at 5 MHz frequency and room temperature. The longitudinal modulus (), shear modulus (), Young’s modulus (), bulk modulus (), and Poisson’s ratio () are assessed from both velocity data and their respective density. The compositional dependence of the ultrasonic velocities and related parameters are discussed to understand the rigidity and compactness of the glass system studied. Haji Abdul Aziz Sidek, Raouf El-Mallawany, Krishnaswamy Hariharan, and Shaharuddin Rosmawati Copyright © 2014 Haji Abdul Aziz Sidek et al. All rights reserved. Advanced Catalysis and Nanostructure Design for Solar Energy Conversion Mon, 07 Jul 2014 07:49:41 +0000 Shaohua Shen, Ke Sun, Haimin Zhang, and Yongqi Liang Copyright © 2014 Shaohua Shen et al. All rights reserved. A Contamination Sensor Based on an Array of Microfibers with Nanoscale-Structured Film Tue, 01 Jul 2014 07:51:26 +0000 A contamination sensor based on an array of microfibers with nanoscale-structured film using evanescent field is proposed and demonstrated theoretically and experimentally. When the molecular contaminants deposit on the nanoscale-structured film, the refractive index of the film will change and the additional loss will be produced due to the disturbance of evanescent field. The possibility of the sensor is demonstrated theoretically by using three-dimensional finite-difference time domain (3D-FDTD). The corresponding experiments have also been carried out in order to demonstrate the theoretical results. Microfibers are fabricated by using hydrogen-oxygen flame-heated scanning fiber drawing method and the nanoscale-structured film coated on the surface of microfibers is deposited by using dip coating process. Then an array of microfibers is assembled to demonstrate the feasibility of the device. The experimental results show that contaminants detection with the device can agree well with the results measured by the laser-scattering particle counter, which demonstrates the feasibility of the new type of contaminant sensor. The device can be used to monitor contaminants on-line in the high-power laser system. Guorui Zhou, Xiaodong Yuan, Hai-Bing Lü, Hai Zhou, Haijun Wang, Hongbin Wang, and Xinxiang Miao Copyright © 2014 Guorui Zhou et al. All rights reserved. Surface Contaminant Control Technologies to Improve Laser Damage Resistance of Optics Sun, 29 Jun 2014 11:41:07 +0000 The large high-power solid lasers, such as the National Ignition Facility (NIF) of America and the Shenguang-III (SG-III) laser facility of China, can output over 2.1 MJ laser pulse for the inertial confinement fusion (ICF) experiments. Because of the enhancement of operating flux and the expansion of laser driver scale, the problem of contamination seriously influences their construction period and operation life. During irradiation by intense laser beams, the contaminants on the metallic surface of beam tubes can be transmitted to the optical surfaces and lead to damage of optical components. For the high-power solid-state laser facilities, contamination control focuses on the slab amplifiers, spatial filters, and final-optical assemblies. In this paper, an effective solution to control contaminations including the whole process of the laser driver is put forward to provide the safe operation of laser facilities, and the detailed technical methods of contamination control such as washing, cleanliness metrology, and cleanliness protecting are also introduced to reduce the probability of laser-induced damage of optics. The experimental results show that the cleanliness level of SG-III laser facility is much better to ensure that the laser facility can safely operate at high energy flux. Xiaofeng Cheng, Xinxiang Miao, Hongbin Wang, Lang Qin, Yayun Ye, Qun He, Zhiqiang Ma, Longbiao Zhao, and Shaobo He Copyright © 2014 Xiaofeng Cheng et al. All rights reserved. One-Dimensional Nonequilibrium Radiation-Transport Equation under Diffusion Approximation and Its Discrete Scheme Tue, 24 Jun 2014 12:16:03 +0000 Based on the nonlocal thermodynamic equilibrium state and large optical thickness of plasma, we establish one-dimensional nonequilibrium radiation-transport equation from diffusion approximation. Through finite volume method, the discrete scheme of radiation-transport equation and the conditions for its definite solution are proposed. The reliability of radiation-transport equation and its discrete scheme is validated. Qi Gao, Chuanfei Zhang, Lin Zhou, Zhenghong Li, Zeqing Wu, Yu Lei, Chunlai Zhang, and Xiaotao Zu Copyright © 2014 Qi Gao et al. All rights reserved. Evolution of Helium with Temperature in Neutron-Irradiated 10B-Doped Aluminum by Small-Angle X-Ray Scattering Sun, 22 Jun 2014 13:41:02 +0000 Helium status is the primary effect of material properties under radiation. 10B-doped aluminum samples were prepared via arc melting technique and rapidly cooled with liquid nitrogen to increase the boron concentration during the formation of compounds. An accumulated helium concentration of ~6.2 × 1025 m−3 was obtained via reactor neutron irradiation with the reaction of 10B(n, α)7Li. Temperature-stimulated helium evolution was observed via small-angle X-ray scattering (SAXS) and was confirmed via transmission electron microscopy (TEM). The SAXS results show that the volume fraction of helium bubbles significantly increased with temperature. The amount of helium bubbles reached its maximum at 600°C, and the most probable diameter of the helium bubbles increased with temperature until 14.6 nm at 700°C. A similar size distribution of helium bubbles was obtained via TEM after in situ SAXS measurement at 700°C, except that the most probable diameter was 3.9 nm smaller. Chaoqiang Huang, Guanyun Yan, Qiang Tian, Guangai Sun, Bo Chen, Liusi Sheng, Yaoguang Liu, Xinggui Long, Xiao Liu, Luhui Han, and Zhonghua Wu Copyright © 2014 Chaoqiang Huang et al. All rights reserved. Influence of Ambient Temperature on Nanosecond and Picosecond Laser-Induced Bulk Damage of Fused Silica Thu, 19 Jun 2014 12:04:47 +0000 The nanosecond (ns) and picosecond (ps) pulsed laser-induced damage behaviors of fused silica under cryogenic and room temperature have been investigated. The laser-induced damage threshold (LIDT) and damage probability are used to understand the damage behavior at different ambient temperatures. The results show that the LIDTs for both ns and ps slightly increased at cryogenic temperature compared to that at room temperature. Meanwhile, the damage probability has an inverse trend; that is, the damage probability at low temperature is smaller than that at room temperature. A theoretical model based on heated crystal lattice is well consistent with the experimental results. L. Yang, X. D. Yuan, H. X. Deng, X. Xiang, W. G. Zheng, S. B. He, Y. Jiang, H. B. Lv, L. Ye, H. J. Wang, and X. T. Zu Copyright © 2014 L. Yang et al. All rights reserved. Effect of UV Laser Conditioning on the Structure of KDP Crystal Wed, 18 Jun 2014 07:15:47 +0000 Multiparametric raster scanning experiments for KDP crystals are carried out to study the laser conditioning efficiency as a function of laser fluence, fluence step, and pulse sequence by using ultraviolet (UV) laser irradiation with pulse duration of approximately 7 ns. It indicates that damage resistance of KDP can be enhanced after conditioning process. And laser conditioning efficiency depends on the maximal fluence which is below the damage threshold. Raman spectra and photothermal absorption have also been studied on KDP crystals before and after multiparametric laser conditioning. Photothermal absorption data reveal that absorbance of conditioned KDP crystal decreases with the increase of laser fluence and the damage threshold of low absorption area is higher. Raman analysis reveals that the effectiveness of laser conditioning relies mainly on the individual mode of PO4 molecule. Decheng Guo, Xiaodong Jiang, Jing Huang, Fengrui Wang, Hongjie Liu, and Xiaotao Zu Copyright © 2014 Decheng Guo et al. All rights reserved. Effect of Heating Method on Hydrogen Production by Biomass Gasification in Supercritical Water Tue, 17 Jun 2014 09:09:43 +0000 The glucose as a test sample of biomass is gasified in supercritical water with different heating methods driven by renewable solar energy. The performance comparisons of hydrogen production of glucose gasification are investigated. The relations between temperature raising speed of reactant fluid, variation of volume fraction, combustion enthalpy, and chemical exergy of H2 of the product gases with reactant solution concentration are presented, respectively. The results show that the energy quality of product gases with preheating process is higher than that with no preheating unit for hydrogen production. Hydrogen production quantity and gasification rate of glucose decrease obviously with the increase of concentration of material in no preheating system. Qiuhui Yan, Hong Zhang, Bingjie Sun, and Liejin Guo Copyright © 2014 Qiuhui Yan et al. All rights reserved. A Model to Describe the Magnetomechanical Behavior of Martensite in Magnetic Shape Memory Alloy Tue, 17 Jun 2014 06:21:56 +0000 A model to describe the constitutive behavior of magnetic shape memory alloy composed with pure martensite is proposed based on the analysis of variants reorientation. A hyperbolic tangent expression is given to describe the variants transition during magnetic and mechanical loading process. The main features of magnetic shape memory alloy, such as pseudoelastic and partially pseudoelastic behavior as well as minor hysteretic loops, can be successfully replicated with the proposed model. A good agreement is achieved between calculated results and experimental data for NiMnGa single crystal. Zaoyang Guo, Haitao Li, Qiang Wan, Xianghe Peng, and Jing Wen Copyright © 2014 Zaoyang Guo et al. All rights reserved. Defects-Induced Hot Spots in TATB Tue, 17 Jun 2014 05:50:00 +0000 We investigate the interaction between the laser and energetic materials with different defects. The three-dimensional models of triaminotrinitrobenzene (TATB) explosives containing spherical pores, craters, and cracks are established, respectively. The laser ignition process of TATB is simulated with three-dimensional finite difference time domain (3D-FDTD) method to study the electromagnetic field distribution surrounding these defects with 355 nm laser incidence. It indicates that the larger defects in the TATB energetic materials have the stronger electric field modulations to initial incident laser for all the three defects, which is easier to lead to the generation of hot spots. Furthermore, TATB materials with spherical pore defects and crater defects are easier to form hot spots than those with narrow crack defects. Zhonghua Yan, Chuanchao Zhang, Hongwei Yan, Zhijie Li, Li Li, Ming Huang, Bisheng Tan, and Xiaodong Yuan Copyright © 2014 Zhonghua Yan et al. All rights reserved. Dielectric Studies on Fe3O4 Nanodoped --Alkyloxybenzoic Acids Mon, 16 Jun 2014 12:03:08 +0000 The stability of phase transition temperatures and textural changes for thermotropic pure and nanodoped --alkyloxybenzoic acid mesogens were aimed to study at considerable time periods. Frequency and temperature dependent dielectric constant and dielectric loss for the pure and nanodoped liquid crystals were carried out. Significant anomalies in dielectric studies were observed near phase transitions when dielectric constant and dielectric loss had been measured as a function of temperature and frequency. Changes in dielectric constant and loss were observed and there were no apparent changes at high frequencies instead maintaining constant values. The variations in conductivity, activation energy, and relaxation times had also been studied in the nematic and smectic phases. The temperature dependent dielectric constant stability (temperature coefficient of dielectric constant ) had shown shift in the observed frequency range of thermotropic liquid crystals corresponding to the change in the dielectric constant values. S. Sreehari Sastry, L. Tanuj Kumar, T. Vishwam, V. R. K. Murthy, S. Lakshminaryana, and Ha Sie Tiong Copyright © 2014 S. Sreehari Sastry et al. All rights reserved. Hydrogen Production by Supercritical Water Gasification of Biomass with Homogeneous and Heterogeneous Catalyst Mon, 16 Jun 2014 06:15:08 +0000 Biomass gasification in supercritical water is a clean and efficient way to convert biomass to hydrogen-rich gaseous products. Appropriate catalyst can lower the reaction temperature to guarantee the technological and economic feasibility. This paper selects Ca(OH)2, Na2CO3, K2CO3, NaOH, KOH, LiOH, and ZnCl2 as typical homogeneous catalysts and three kinds of Raney-Ni, dolomite, and olivine as typical heterogeneous catalysts. The catalyst effects are investigated in the process of biomass gasification in supercritical water with the temperature of 400°C, pressure of  MPa, and residence time of 20 min. The experimental results show that Raney-Ni has the best hydrogen selectivity and hydrogen yield. The mixture of NaOH with Raney-Ni was investigated in order to research the synergistic effect of different catalysts. The experimental results show that Raney-Ni and NaOH have a synergistic effect in the biomass gasification in supercritical water. Hui Jin, Youjun Lu, Liejin Guo, Ximin Zhang, and Aixia Pei Copyright © 2014 Hui Jin et al. All rights reserved. The Electric Field Modulation by Hemisphere Damage Sites in Fused Silica Subsurface Wed, 11 Jun 2014 09:33:49 +0000 The effect of defect density on the electric field modulation to incident laser is investigated in this work. Based on the actual defect distribution in fused silica subsurface, the three-dimension grid model of defect sites is constructed firstly. Then, the three-dimension finite-difference time-domain method is developed to solve the Maxwell equations. The electric field intensity in the vicinity of the defect sites located in front subsurface of fused silica is numerically calculated. The relationships between the maximal electric field intensity in fused silica and the geometry of the defect sites are given. The simulated results reveal that the modulation becomes more remarkable with the increase of defects density firstly and then decrease. Besides, the effect of the distribution mode of defects on modulation is discussed. Meanwhile, the possible physical mechanism is analyzed in detail. Shaobo He, Liang Yang, Li Li, and Xiao-Tao Zu Copyright © 2014 Shaobo He et al. All rights reserved. Revisiting the Zinc-Blende/Wurtzite Heterocrystalline Structure in CdS Tue, 10 Jun 2014 00:00:00 +0000 The band offset at CdS zinc-blende (ZB)/wurtzite (WZ) heterocrystalline interface was revisited using the first principles calculations with the local density approximation (LDA), generalized gradient approximation (GGA), and Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional. It was revealed that, unlike most IV, III-V, and II-VI semiconductors, the band alignment at CdS ZB/WZ heterocrystalline interface was of type-I with straddling lineup of band edges, which was irrespective of the exchange-correlation energy functional, the thickness of ZB and WZ segments, and the ZB/WZ interface location. The partial charge densities of VBM and CBM states were separated around two adjacent interfaces in one unit cell of heterocrystalline superlattice. This type of carrier localization was mainly attributed to the spontaneous polarization occurring in the WZ segment rather than the band offset at the interface. Zhaohui Zhou, Mingtao Li, Po Wu, and Liejin Guo Copyright © 2014 Zhaohui Zhou et al. All rights reserved. Preparation and Characterization of Novel Fe2O3-Flaky Coated Carbon Fiber by Electrospinning and Hydrothermal Methods Wed, 04 Jun 2014 07:25:43 +0000 A novel hierarchical nanostructure of -flaky coated carbon fibers was produced by the electrospinning process followed by a hydrothermal technique. First, electrospinning of a colloidal solution that consisted of ferric nitrate and polyacrylonitrile (PAN) was performed to produce PAN nanofibers. Then electrospun nanofiber was stabilized and calcinated in nitrogen at 800°C for 2 h to produce carbon nanofibers (CNFs) which were exploited to produce -flaky structure using hydrothermal technique. The as-obtained products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results revealed that flakes were successfully grown on the CNFs substrates, and the coverage of flakes could be controlled by simply adjusting the hydrothermal pH value and time. -flaky coated carbon fibers displayed high photocatalytic activity toward degradation of methyl orange (MO) under visible light irradiation. Qing-Yun Chen, Lang Liu, and Yun-Hai Wang Copyright © 2014 Qing-Yun Chen et al. All rights reserved. Investigation of Control of Residual Stress Induced by CO2 Laser-Based Damage Mitigation of Fused Silica Optics Tue, 03 Jun 2014 07:05:45 +0000 A CO2 laser-based annealing technique for the mitigation of damaged sites of fused silica is studied to suppress the residual stress left on the surface. The laser annealing by a linear decrease of the CO2 laser power effectively reduces the residual stress. The residual stress of mitigated sites is characterized by polarimetry, the reduction of the maximum retardance around the mitigated sites with the exposure time of laser annealing fits a stretched exponential equation, and the maximum retardance with optimal laser annealing is reduced (36 ± 3)% compared to that without laser annealing. The residual stress regions are destructively characterized by introducing damage. The critical size of damage leading to fracture propagation for the mitigated sites without laser annealing is in the range of 120~230 μm, and the corresponding critical size of damage for the mitigated sites with laser annealing is larger than 600 μm. According to the relationship between maximum damage size and critical stress, the residual stress without laser annealing is in the range of 28–39 MPa and the residual stress with laser annealing is less than 17 MPa. These results indicate that the CO2 laser-based annealing technique has a positive effect on the control of residual stress induced by CO2 laser-based damage mitigation. Chuanchao Zhang, Wei Liao, Lijuan Zhang, Yayun Ye, Jing Chen, Haijun Wang, Xiaoyu Luan, and Xiaodong Yuan Copyright © 2014 Chuanchao Zhang et al. All rights reserved. Evolution of Oxygen Deficiency Center on Fused Silica Surface Irradiated by Ultraviolet Laser and Posttreatment Thu, 29 May 2014 13:34:32 +0000 Evolution of oxygen deficiency centers (ODCs) on a fused silica surface irradiated using a 355 nm ultraviolet (UV) laser beam in both vacuum and atmospheric conditions was quantitatively studied using photoluminescence and X-ray photoelectron spectroscopy. When the fusedsilica surface was exposed to the UV laser in vacuum, the laser damage threshold was decreased whereas the concentration of the ODCs was increased. For the fuse silica operated under the high power lasers, creation of ODCs on their surface resulted from the UV laser irradiation, and this is more severe in a high vacuum. The laser fluence and/or laser intensity have significant effects on the increase of the ODCs concentration. The ODCs can be effectively repaired using postoxygen plasma treatment and UV laser irradiation in an excessive oxygen environment. Results also demonstrated that the “gain” and “loss” of oxygen at the silica surface is a reversible and dynamic process. Hai-Bing Lü, Shi-Zhen Xu, Hai-Jun Wang, Xiao-Dong Yuan, Chao Zhao, and Y. Q. Fu Copyright © 2014 Hai-Bing Lü et al. All rights reserved.