Granular fragility under thermal cycles

We study the effect of thermal cycling of granular materials on both the granular packing fraction and the position of an intruder object within a granular sample. We demonstrate that the packing fraction consistently increases with thermal cycling, regardless of the relative coefficients of thermal expansion for the grains and their containers. The exact magnitude of the packing fraction increase appears to be influenced by factors other than the thermal expansion coefficients, with the intergrain friction and the friction between the grains and their container likely to be important. We also examined the motion of spherical intruders with thermal cycling as a function of the size and density of the intruders, and find that such intruders sink within the grains when the pressure from the intruder exceeds a threshold. These data demonstrate the fragility of dense granular ensembles to changes in the ambient temperature.     

Effects of deposition conditions on composition and thermal cycling life of lanthanum zirconate coatings

Lanthanum zirconate (La₂Zr₂O₇, LZ) coatings were prepared under four different deposition conditions by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, surface and cross-sectional morphology, cyclic oxidation behavior of these coatings were studied. Elemental analysis indicates that the coating composition has partially deviated from the stoichiometry of pyrochlore, and the existence of excess La₂O₃ is also observed. The deviation could be reduced by properly controlling the electron beam current or by changing the ingot composition. Meanwhile, when the electron beam current was 500 - 600 mA, the thermal cycling life of the coating is superior to other coatings.     

矿山酸性废水治理HDS工艺技术研究

HDS处理工艺是一种高效底泥循环回流技术,在矿山酸性废水治理中具有提高药剂利用率、提高污泥浓度、改善污泥沉降浓缩特性等优点,在国外矿山酸性废水治理中具有广泛的应用,在国内仅有部分试验研究。通过实验室试验以及结合研究资料对HDS处理工艺在矿山酸性废水的治理过程机理进行了研究,同时对技术研究进展及应用等方面进行了现状分析。     

基于多指标综合评价策略的快速冷热成型工艺优化研究

在对快速冷热成型（RHCM）工艺深入研究及合理分析的基础上,确定了RHCM制品品质评价指标为制件翘曲变形量、降沉指数和成型收缩率,主要成型工艺参数为模具温度、熔体温度、注射压力、V/P转换压力和保压压力;结合田口实验法、CAE分析和多元线性回归理论建立了可以适当描述RHCM制品品质评价指标与主要成型工艺影响因素之间的关系的多指标综合评价数学模型;整个建模过程沿袭了量纲分析法的建模理论;模型的优化通过改进遗传算法来实现,并经实验验证了该优化方法的可行性。     

Fuel-flexible operation of a solid oxide fuel cell with Sr0.8La0.2TiO3 support

Solid oxide fuel cells with Sr_0.8La_0.2TiO₃ anode-side supports, Ni- Sm-doped ceria adhesion layer, Ni- Y₂O₃-stabilized ZrO₂ (YSZ) anode active layer, YSZ electrolyte, and La_0.8Sr_0.2MnO₃(LSM)–YSZ cathode are described. These cells are stable in simulated natural gas at current densities as low as 0.2 A cm⁻². This represents much-improved stability against coking in natural gas, compared with conventional Ni–YSZ anode-supported SOFCs which rapidly coke, even at higher current densities. Cell operation in H₂ fuel with 50–100 ppm, H₂S results in an initial decrease in cell power density, but no long-term degradation occurs and full recovery to the initial performance level is observed after dry H₂ fuel flow is restored. Degradation is not observed during or after seven redox cycles between H₂ and air.     

The effect of carbon support treatment on the stability of Pt/C electrocatalysts

A potential cycling test was conducted to evaluate the effect of carbon support treatment on the stability of Pt/C electrocatalysts. The FTIR spectra show that after oxidative treatments, the carbon support became rich in oxygen-containing functional groups. Oxidative treatments of the carbon support increase the interaction between the metal particle and the support, resulting in an improved electrochemical stability of Pt/C catalysts. The Pt/C catalyst prepared from the H₂O₂-treated carbon support exhibits a higher stability than that prepared from the HNO₃-treated carbon support.     

有机-无机混合相变材料的热物性研究

目的获得有效改善过冷,同时保持较高潜热、性能稳定的混合相变储能材料。方法分别制备不同质量比的硬脂酸/Mg(NO_3)_2·6H_2O、硬脂酸/Na_2HPO_4·12H_2O的混合材料,使用高低温交变箱测试长期循环性能,用温度记录仪测其步冷曲线,得到相变温度和过冷度,再使用参比温度曲线法对相变材料循环前后的相变潜热进行测试比较。结果硬脂酸/Na_2HPO_4·12H_2O混合材料的过冷度降低至3℃左右,经300次融化/凝固循环后过冷度维持恒定,潜热衰减率在20%以内。结论采用结构相似的2种混合相变材料均可改善无机水合盐的过冷度。硬脂酸与Mg(NO_3)_2·6H_2O相容性不佳,相变潜热的衰减加剧,循环稳定性变差,而硬脂酸与Na_2HPO_4·12H_2O的相容性良好,性能表现稳定,是一种良好的储能材料。     

斜管沉淀罐在转炉污水处理系统中的应用

简要叙述了斜管沉淀罐的原理、特点和在炼钢厂4号、5号、6号转炉炼钢污水处理系统中的应用,与1号、2号、3号转炉污水处理系统使用的浓缩池进行了比较,并对斜管沉淀罐在炼钢污水处理系统中节省占地、降低检修维护成本等特点进行了简要说明。     

基于四水转化的灌区耗水量计算模型

针对以往灌区耗水量计算方法的不足和灌区水循环机制的特点,本文建立了基于四水(即大气水、地表水、地下水和土壤水)转化的灌区耗水量计算模型。该模型把灌区划分为农田、林草地、荒地、湖泊湿地和城镇用地五类水均衡模块,重点考虑了人类活动对灌区农业、工业、生活和生态耗水量的影响。以宁夏青铜峡引黄灌区为例,详细计算了各种耗水类型的耗水总量和耗用的黄河水总量,并定量分析了各水均衡要素间的相互转化关系。模拟计算结果与试验观测结果对比分析表明,该模型在平原灌区具有较好的模拟精度,能够应用于生产实践。     

RHCM成型高光制品的结构设计技术

根据快速冷热成型(RHCM)对制品结构设计的基本要求,结合普通制品结构设计一般原则,研究了高光注塑制品的主体结构及其筋、凸起、孔、圆角等类型结构的基本设计技术,得出了高光注塑制品结构设计需要同时满足壁厚均匀性与结构协调性两个主要准则,并以音箱前面壳和液晶显示器(LCD)电视机前壳为例进行了设计研究,为高光制品结构设计提供了理论上的指导。