铌单晶循环变形过程中的表面形变带

用光学显微镜和扫描电镜观察了〔321〕和〔110〕位向的铌单晶在循环变形时的表面形貌变化.研究了圆形试样经过循环变形到饱和阶段表面出现的皱褶.本文用形变带这个词来表示材料经不均匀变形后产生的这种皱带,它不同于有特定位向的扭折带.根据表面形貌细节把形变带分成五类,并对形变带的形成过程进行了讨论.形变带所在平面和轴向夹角均在≈45°,说明宏观应力状态对形变带的形成起重要作用.     

Electric Field and Gradient Microstructure for Cooperative Driving of Directional Motion of Underwater Oil Droplets

Driving a liquid droplet with control of directional motion on a solid surface, by introducing a surface wettability gradient or external stimuli, has attracted considerable research attention. There still remain challenges, however, due to the slow response rate and slow speed of continuous liquid droplet motion on the structured surface. Here, an approach to continuously drive the underwater oil droplet with control of directional motion by the cooperative effects of an electric field and the gradient of a porous polystyrene microstructure is demonstrated. The gradient microstructure induces the liquid droplet to take on an asymmetrical shape, causing unbalanced pressure on both ends to orient the droplet for motion in a particular direction. Meanwhile, the electric field decreases the contact area and the corresponding viscous drag between the droplet and the gradient‐structured surface. Then, the unbalanced pressure pushes the underwater oil droplet to move directionally and continuously at a certain voltage. This work provides a new strategy to control underwater oil droplets and realize unidirectional motion. It is also promising for the design of new smart interface materials for applications such as electrofluidic displays, biological cell and particle manipulation, and other types of microfluidic devices.     

Preparation and characterization of submicron-cerium oxide by hypergravity coprecipitation method

Submicron-cerium oxide particles were synthesized by applying hypergravity using ammonium bicarbonate (precipitant) and cerium nitrate hexahydrate (precursor). The influence of the concentration, pH, dispersant loading, flow rate, rotation speed of the hypergravity rotating bed, calcination temperature, and time on the cerium oxide particle size were examined by zeta potential, solid–liquid contact angle, thermo-gravimetry–differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The cerium oxide particles were highly dispersed, with an average particle size of 200 nm. Calcining at 650 °C for 1.5 h afforded the smallest particles. The crystallite size and fraction crystallinity increased with prolonged calcination. Crystalline cerium dioxide grew along three crystal planes, forming a complete face-centered cube, affording high hardness and activity of the polishing powder. The optimal conditions were: cerium nitrate concentration: 0.7 mol/L, cerium nitrate/ammonium bicarbonate molar ratio: 1:3, dispersant mass fraction: 3%, cerium nitrate initial pH: 4–5; the precursor solution was adjusted to pH 9 with ammonia water. Hypergravity coprecipitation with 1.5 h calcination afforded submicron-sized cerium oxide with a uniform size distribution using ammonium bicarbonate in an industrially viable process. The simple and low-cost manufacturing process may enable the development of hypergravity-assisted chemical synthesis technology.     

磷酸根掺杂MnFe2O4及其赝电容特性

采用水热法先合成MnFe₂O₄(MFO), 然后通过与PH₃反应制备了磷酸根离子掺杂的MnFe₂O₄(PMFO), 以提高它的电化学性能。研究结果表明, 磷酸根掺杂不仅增大了MnFe₂O₄的比表面积, 也增加了材料的电导性。在1 A/g电流密度下, PMFO比容量为750 F/g, 与MFO相比, 比电容提高了近70%, 同时循环稳定性也得到了极大改善。以PMFO为正极、活性碳为负极的非对称超级电容器(ASCs), 在功率密度为2.7 kW/kg时, 能量密度达到168.8 Wh/kg。因此, PMFO是有极大应用前景的超级电容器电极材料。     

结构早期损伤识别技术的现状和发展趋势

本文综述了近几年来结构早期损伤识别技术的方法，对各结构早期损伤识别的方法进行了评述，讨论了各方法在理论上和实际应用中存在的问题。根据国内外最新文献，指出了结构早期损伤识别技术发展的方向和趋势。     

An Innovative Approach for Improving the Reliability of Reticulated Porous Ceramics

An innovative approach has been developed to fabricate reticulated porous ceramics (RPCs) with uniform macrostruc-ture by using the polymeric sponge as the templates. In this approach, the coating process comprises of two stages. In the first stage, the thicker slurry was used to coat: uniformly the sponge substrate. The green body was preheated to produce a reticulated preform with enough handling strength after the sponge was burned out. In the second stage, the thinner slurry was used to coat uniformly the preform. The population of the microscopic and macroscopic flaws in the structure is reduced significantly by recoating process. A few filled cells and cell faces occur in the fabrication and the struts were thickened. A statistical evaluation by means of Weibull statistics was carried out on the bend strength data of RPCs, which were prepared by the traditional approach and innovative approach, respectively. The result shows that the mechanical reliability of RPCs is improved by the innovative approach     

CH3COONa·3H2O相变蓄热性能研究

以三水醋酸钠(CH3COONa·3H2O)为蓄热基质,通过大量实验,遴选合适的抗沉淀剂和成核剂.配成相变温度约55"(2、过冷度小于2℃的蓄热材料.对该材料的蓄热性能进行研究表明,该材料相变热可达238J/g,导热系数为1.072W/m·K(30℃时),可用于空调冷凝热回收系统.     

Effect of polyvinyl alcohol additive on the pore structure and morphology of the freeze-cast hydroxyapatite ceramics

Porous hydroxyapatite (HAP) ceramics with different morphologies were fabricated by the freeze casting method. The morphologies of HAP ceramics were modified by adjusting the concentration of polyvinyl alcohol (PVA) additive in the HAP slurries. HAP ceramics without PVA additive were composed of non-interconnected macroscopic lamellar pores and porous ceramic walls. With PVA additive, the HAP ceramics were made up of small lamellar pores or three-dimensional reticulate pores and porous ceramic walls. PVA additive had no effect on the phase composition of HAP ceramics. The open porosity and pore connectivity were improved because of the addition of PVA.     

岩溶热储地热能可持续开发潜力的模糊综合评价

该文运用模糊综合评判法对天津市区雾谜山组热储层的地热资源进行了可持续开发潜力评价。在前人研究的基础上,建立起评价因素集和评语集,并利用层次分析法确定了各因素的权重。选用合适的隶属函数,建立隶属度矩阵。经模糊转换得到评判结果,其与当地管理部门根据实践经验得出的结果基本一致。这表明模糊综合评判法在地热资源的评价上可操作性强、效果好,可以用于地热资源的可持续开发潜力评价。     

Effects of M-Doping （M = Al or Si） on Electronic Structure of LaNi5

Employing the first principles discrete variational method （DVM）, the electronic structures of LaNi5 hydrogen storage alloys with Ni replaced by common element M （M = Al or Si） were investigated. The results show that the s electrons of H mainly interact with the s electrons of non-hydride-forming element Ni and M, though there is a larger affinity of La for hydrogen than that of Ni and M in pure metal hydrogen system. The effect on the electronic structure of Al is very similar to that of Si in the LaNi5 alloy because of their similar character.