Electrical and optical study of Cu(In, Ga)Se2 co-evaporated thin films

Co-evaporation technique from three sources was used to prepare Cu(In, Ga)Se₂ polycrystalline thin films for photovoltaic conversion. Their conductivity was studied in the range 20–300 K. The grain boundary scattering mechanism is mainly responsible for the diffusion process in the latter materials. In the low temperature region, we interpret the data in terms of Mott law and the analysis is very consistent with the variable range hopping. However, thermoionic emission is predominant at high temperatures. When the conductivity deviates from the classical grain boundary conduction models, inhomogeneity is then considered and parameters such as the standard deviation and the mean potential barrier height are derived. Transmittance measurements yielded band gap values of 1.07 and 1.64 eV for CuInSe₂ and CuGaSe₂, respectively.     

铁电晶体TGS的快速生长

报道了TGS晶体的溶液状态及其快速生长的实验结果。发现了pH为2.52的溶液是实现快速生长的最佳溶液,利用快速旋转叶片来加速溶液对流,对于截面积为40mm×40 mm的(010)面,其生长速度达到了5mm/d,对快速生长的TGS晶体的性能研究表明:其热电和介电性能也发生了一些变化。     

Reformulation of oxide growth equations for oxidation of silicon bond coat in environmental barrier coating systems

The formulation of Deal and Grove for the oxidation of silicon and the growth of a silica layer is revisited to include the effects of a protective coating layer. The linear-parabolic equation of the form $x_o^2+A{x}_o=Bt$ is still applicable, but the expression for the constant A must be modified to account for the coating. The modified expression for A is a linear function of the coating thickness. The modified formulation is applied to assess recently published experimental results for the oxidation of a silicon bond coat in an environmental barrier coating. Application of the modified expression for A to the experimental results leads to an estimate of the ratio of the oxidant permeability in the oxide to its permeability in the coating.     

Spark Plasma Sintering of Alumina

A systematic study of various spark plasma sintering (SPS) parameters, namely temperature, holding time, heating rate, pressure, and pulse sequence, was conducted to investigate their effect on the densification, grain-growth kinetics, hardness, and fracture toughness of a commercially available submicrometer-sized Al₂O₃ powder. The obtained experimental data clearly show that the SPS process enhances both densification and grain growth. Thus, Al₂O₃ could be fully densified at a much lower temperature (1150°C), within a much shorter time (minutes), than in more conventional sintering processes. It is suggested that the densification is enhanced in the initial part of the sintering cycle by a local spark-discharge process in the vicinity of contacting particles, and that both grain-boundary diffusion and grain-boundary migration are enhanced by the electrical field originating from the pulsed direct current used for heating the sample. Both the diffusion and the migration that promote the grain growth were found to be strongly dependent on temperature, implying that it is possible to retain the original fine-grained structure in fully densified bodies by avoiding a too high sintering temperature. Hardness values in the range 21–22 GPa and fracture toughness values of 3.5 ± 0.5 MPa·m^1/2 were found for the compacts containing submicrometer-sized Al₂O₃ grains.     

70%安泰生WP防治苹果斑点落叶病田间药效试验

试验结果表明，70％安泰生产500倍对苹果斑点落叶病春梢、秋梢的防治效果和大生近似而略好于大生，防效达81．66％－87．29％；70％安700倍仅在春梢期的防效达66．53％，而秋梢期防治效果以及70％安泰生1000倍防效较差。     

Zn:Fe:LiNbO3单晶的坩埚下降法生长及其成分研究

通过优选合适的化学原料，用坩埚下降法生长出了无宏观缺陷的Zn：Fe：LiNbO3(Zn：Fe：LN)单晶。生长的工艺参数是：用微凸生长界面生长，生长速度为1～3mm／h，温度梯度为20～30℃／cm。用X射线衍射及DTA对晶体进行了分析；测定了晶体的吸收光谱。结果表明：所有Zn：Fe：LN晶体中的Fe^2 浓度沿生长方向增加；掺杂3％ZnO(摩尔分数)的Zn：Fe：LN单晶中的Fe^2 浓度沿生长方向的变化量比掺杂6％ZnO的大。从坩埚下降法的温场特点、晶体的热处理过程、环境气氛，以及ZnO组分对Fe离子的排斥作用解释了产生Fe^2 离子浓度变化的原因。     

Microstructural Analysis of Liquid-Phase-Sintered β-Silicon Carbide

The microstructures of fine-grained β-SiC materials with α-SiC seeds annealed either with or without uniaxial pressure at 1900°C for 4 h in an argon atmosphere were investigated using analytical electron microscopy and high-resolution electron microscopy (HREM). An applied annealing pressure can greatly retard phase transformation and grain growth. The material annealed with pressure consisted of fine grains with β-SiC as a major phase. In contrast, the microstructure in the material annealed without pressure consisted of elongated grains with half α-SiC. Energy-dispersive X-ray analysis showed no differences in the amount of segregation of aluminum and oxygen atoms at grain boundaries, but did show a significant difference in the segregation of yttrium atoms at grain boundaries along SiC grains for the two materials. The increased segregation of yttrium ions at grain boundaries caused by the applied pressure might be the reason for the retarded phase transformation and grain growth. HREM showed a thin secondary phase of 1 nm at the grain boundary interface for both materials. The development of a composite grain consisting of a mixture of β/α polytypes during annealing was a feature common to both materials. The possible mechanisms for grain growth and phase transformation are discussed.     

纳米陶瓷的烧结研究

纳米陶瓷的制备过程中，烧结是关键一环。总结了现有的烧结理论，介绍了国内外流行的纳米烧结技术，并提出了今后的研究方向。     

Slow stable crack growth in high density polyethylenes

The phenomenon of slow stable crack growth in polyethylene is investigated using notched specimens subject to constant load and the concepts of fracture mechanics. The effect of specimen geometry and dimension, the loading and the mode of loading on the applied stress intensity factor versus crack speed ($\text{K}{}_{\mathrm{c}}\text{-}\text{a}\text{?}$) curves has been studied to demonstrate that K_c is the controlling stress parameter for crack growth under suitable conditions. $\text{K}{}_{\mathrm{c}}\text{-}\text{a}\text{?}$ curves are obtained for a high density polyethylene homopolymer in distilled water and in a diluted detergent solution at four different temperatures. Results are also obtained for a much tougher medium density polyethylene copolymer whenever possible. Several mechanisms can be identified from the form of the $\text{K}{}_{\mathrm{c}}\text{-}\text{a}\text{?}$ curves. Two, in particular, have been observed but not explained before: (i) crack growth with a time dependence of 0.25, and (ii) the high $\text{K}{}_{\mathrm{c}}\text{-}\text{a}\text{?}$ slopes for crack growth in a tough copolymer. With the help of scanning electron microscopic studies of the fracture surfaces, (i) is postulated to be due to diffusion controlled void growth process and (ii) is considered to be the result of crack tip blunting effects. From the temperature dependence of crack growth, the activation energy of the diffusion controlled crack growth process is found to coincide with that of the x-relaxation process in polyethylene implying that diffusion controlled crack growth may be related to the motion of main chains in the polymer.