无氧铜的准等熵压缩性

 利用递变冲击阻抗材料叠合而成的组合飞片，在二级轻气炮上对无氧铜进行了准等熵压缩性测量，加载时间约达1 μs。用激光速度干涉仪连续记录了不同厚度处无氧铜样品自由面速度随时间的变化过程，并通过拉格朗日波分析技术计算得到40 GPa下的准等熵的应力-应变曲线。结果表明：在低应力区，无氧铜的准等熵压缩线位于冲击绝热线之上；到32 GPa以上，准等熵压缩线才回落到冲击绝热线之下。这个现象与Barker、Chhabildas等对铝与钨的实测现象是一致的，它表明：在低应力区，材料的冲击强化效应与加载速率密切相关。     

Swelling Properties and Environmental Responsiveness of Superabsorbent Composite Based on Starch-G-Poly Acrylic Acid/Organo-Zeolite

Star-g-poly (acrylic acid)/organo-zeolite 4A (S-g-PAA/OZ) superabsorbent composite was prepared by grafting partially neutralized acrylic acid onto starch in the presence of organo-zeolite 4A (OZ) as an inorganic component. The morphology was characterized with scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) analysis revealed the fine distribution of OZ in superabsorbent composite. The swelling kinetics of the composites were characterized by means of a Schott's second-order model. The effect of OZ concentration in the composite on the water absorbency and swelling behavior were tested. The swelling properties of the composites were evaluated in various environments; pH, salinity, temperature, urea solution, and solvent-water mixtures. The activation energy (ΔE) for water during the swelling process was also determined through Arrhenius plots. The results showed that the proper amount of OZ was beneficial for improvement of the water absorbent capacity and the initial swelling rate in distilled water. The optimum prepared composite with 10 wt % OZ, possessed the maximum water absorption (511g/g) in distilled water and (521 g/g) in 0.1 wt % urea solution. The results inferred that S-g-PAA/OZ superabsorbent composite can be exploited for agriculture and medical applications.     

Graphite–boron composite heater in a Kawai-type apparatus: the inhibitory effect of boron oxide and countermeasures

We have investigated the performance of a graphite–boron composite (GBC) with 3?wt % boron as a precursor for a boron-doped diamond heater in a Kawai-type apparatus at 15?GPa. We first tested a machinable cylinder of GBC sintered at 1000°C in Ar/H₂ gas (99:1 molar ratio). Boron oxide (B₂O₃) formed during sintering frequently hindered the GBC heater from stable operation at temperatures higher than 1400°C by producing melt throughout the heater together with oxide and/or silicates. We then rinsed the GBC heater in hydrochloric acid to remove B₂O₃. After rinsing, we succeeded in stably generating temperatures higher than 2000°C. We also improved a molding process of different-sized GBC tubes for convenient use and tested the molded GBC heater. It was free from the B₂O₃ problem. The electromotive force of the W/Re thermocouple was successfully monitored up to 2400°C.     

Mechanical properties of sisal fibre-reinforced polymer composites: a review

There has been a growing interest in the utilization of sisal fibres as reinforcement in the production of polymeric composite materials. Natural fibres have gained recognition as reinforcements in fibre polymer–matrix composites because of their mechanical properties and environmental friendliness. The mechanical properties of sisal fibre-reinforced polymer composites have been studied by many researchers and a few of them are discussed in this article. Various fibre treatments, which are carried out in order to improve adhesion, leading to improved mechanical properties, are also discussed in this review paper. This review also focuses on the influence of fibre content and fabrication methods, which can significantly affect the mechanical properties of sisal fibre-reinforced polymer composites.     

Banana fiber strands–reinforced polymer matrix composites

Banana fiber (BF)-reinforced low-density polyethylene (LDPE) unidirectional composites were fabricated by the compression molding process with 40 wt% fiber loading. The fibers were modified with methylacrylate (MA) mixed with methanol (MeOH) along with 2% benzyl peroxide under thermal curing method at different temperatures (50–90 °C) for different curing times (10–50 min) in order to have better compatibility with the matrix. The effect of fiber surface modification on the mechanical properties (tensile and impact properties) of the composites were evaluated. Monomer concentration, curing temperature, and curing time were optimized in terms of polymer loading and mechanical properties. The mechanical properties were found to be improved based on the improved interaction between the reinforcement and the matrix. Optimized BFs were again treated with 2–5 wt% starch solutions and composites made of 4% starch treated BF showed the highest mechanical properties than that of MA treated composites. Scanning electron microscopy (SEM) was performed to get an insight into the morphology of the composites. Water uptake and soil degradation test of the composites were also investigated.     

Studies on the removal of As(III) and As(V) through their adsorption onto granular activated carbon/MnFe2O4 composite: isotherm studies and error analysis

The granular activated carbon/MnFe₂O₄ composite with a mass ratio of 2:1 was synthesized using a simple chemical coprecipitation procedure and used for the removal of As(III) and As(V) from synthetically prepared wastewater. Physicochemical analysis of the composite was carried out through Brunauer, Emmett and Teller surface area and total pore volume, Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Micrograph and Energy-Dispersive X-Ray Spectroscopy (SEM-EDX). The impact of various adsorption parameters such as the initial pH, adsorbent dose, contact time, temperature and initial arsenic concentration were systematically investigated to evaluate the optimum operating conditions. Nonlinear regression analysis was employed to identify the best-fit isotherm on the basis of three correlation coefficients and three error functions and also to predict the parameters involved in one one-parameter, six two-parameter, nineteen three-parameter, three four-parameter and one five-parameter isotherms. The maximum adsorption capacities estimated using the Langmuir model were 1253 mg/g for As(III) and 1314 mg/g for As(V) at 30 °C temperature and 70 min contact time. The results showed that As(III) and As(V) removal was strongly pH-dependent with an optimum pH value of 7.0 and 4.0, respectively. The mean adsorption energy (E) calculated from the D–R model indicated the nature of adsorption being ion exchange type.     

A novel orthogonally linearly polarized Nd:YVO4 laser

<正>We presented a novel orthogonally linearly polarized Nd:YVO₄ laser.Two pieces of a-cut grown-together composite YVO₄/Nd:YVO₄ crystals were placed in the resonant cavity with the c-axis of the two crystals orthogonally.The polarization and power performance of the orthogonally polarized laser were investigated.A 26.2-W orthogonally linearly polarized laser was obtained.The power ratio between the two orthogonally polarized lasers was varied with the pump power caused by the polarized mode coupling.The longitudinal modes competition and the corresponding variable optical beats were also observed from the orthogonally polarized laser.We also adjusted the crystals with their c-axis parallele to each other,and a 40.7-W linearly polarized TEMoo laser was obtained,and the beam quality factors were M_x²=1.37 and M_y² =1.25.     

分层复合材料光波导的非线性二次增强效应

通过对分层复合材料光波导ＴＭ模等效介电系数的分析，清楚地预言了无限扩展分层复合材料结构中的非线性增强将因光波导的边界作用而引起进一步的加强。     

Photo-induced anisotropy in ZnO/PVA nanocomposites prepared by modified electrochemical method in PMA matrix

Substantial photo-induced optical anisotropy was discovered in ZnO/PVA nanocomposites under the influence of external bicolor laser illumination. Zinc oxide nanoparticles were synthesized by electrolysis of a sodium chloride aqueous medium including poly-methacrylic acid (PMA) in a cell system having a soluble zinc anode. The structural analysis of the ZnO powder samples has been carried out by X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM). The polyvinyl alcohol (PVA) embedded ZnO films obtained from the powder samples possess larger grain sizes than those in powder form. The films were prepared from the same polymer matrix but elaborated with two different PVA contents which are respectively 15% and 30%. The photoinduced anisotropy was identified by using two bicolor Er: glass laser beams incident at different angles. Substantial influence of the technological processes on the embedded nanoparticle sizes and related birefringence was explored. The process of laser induced anisotropy shows an occurrence of birefringence saturation.     

梯度颗粒复合介质的光学双稳

重点研究了组分的梯度构形对带壳球形颗粒复合介质的光学双稳特性的影响.其中球形颗粒是由非线性核和介电函数具有梯度分布的线性壳组成.对于壳层介电函数具有幂指数分布的情况,通过求解麦克斯韦方程,得到各区域的势能分布函数,从而求得核内电场的数学表达式.数值研究发现,该复合介质的光学双稳阈值和区域与壳层的厚度及壳层的介电幂指数有关,随着壳层厚度增大或幂指数增大,双稳阈值将变宽.此外,还研究了正入射情况下复合材料体系的反射系数随外电场的变化情况, 发现其关系曲线是一条回线. 关键词： 梯度颗粒 复合介质 光学双稳