稀土元素对R-Y-Ni系A2B7型无镁储氢合金微观结构和电化学性能的影响

采用真空电弧熔炼及退火处理制备R-Y-Ni系A_2B_7型R0.3Y0.7Ni3.25Mn0.15Al0.1(R=Y,La,Pr,Ce,Nd,Gd,Sm)储氢合金,系统研究稀土元素R对合金微观组织与结构、储氢和电化学性能的影响。XRD和SEM-EDS分析表明,合金退火组织由Ce2Ni7型主相、PuNi3型及少量Ca Cu5型相组成,Ce2Ni7型主相的晶格常数a、c及晶胞体积V均随稀土R原子半径的减小而依次降低。该合金均具有明显的吸放氢平台,常温下最大吸氢容量为1.17%~1.48%(w/w),吸氢平台压Peq为0.037~0.194 MPa。电化学分析表明,退火合金电极的电化学活化性能优良,R=La合金具有最高的放电容量(389.2 mAh·g-1)和较佳的容量保持率(充放电循环100次后的S100=85.7%),其中合金微观组织的不均匀性及稀土元素的电化学腐蚀是影响电极循环稳定性的主要原因。合金电极的高倍率放电性能(电流密度为900 m A·g-1)HRD900=71.05%~86.94%,其电极反应动力学控制步骤主要由氢原子在合金体相中的扩散速率所控制。     

锂电池极片微结构优化及可控制备技术进展

锂离子电池是应用最广泛的电化学储能器件,目前,经济的快速发展对其提出了更高的要求。 电极微观结构对电池性能影响显著,电极微结构精细设计及可控制备成为锂离子电池领域的研究热点之一。 本文结合锂离子电池最新发展趋势,总结了锂离子电池电极反应基本过程及电极微结构的表征技术,然后概述了近几年电极微观结构的设计与优化,并分析了电极微结构的关键特征。 基于理想的电极结构,综述了电极可控制备技术的最新进展。     

硼酸钙对电瓷结构和性能的影响

研究了硼酸钙掺量对电瓷的相结构、显微结构、电气性能和机械性能的影响.通过不同硼酸钙添加量的电瓷在不同烧结温度条件下的断裂强度、气孔率、电阻率,结合电瓷的晶相结构和显微结构的变化,探讨其构效关系.结果表明:硼酸钙含量的增加或烧结温度升高,电瓷的电阻率和气孔率降低.但当硼酸钙掺量超过10;,烧结温度超过1120℃之后,电阻率和气孔率的变化不明显.电瓷的断裂强度随着硼酸钙的添加而提高,当硼酸钙含量超过10;后开始降低,添加量为10;时电瓷的断裂强度随着烧结温度而提高,1120℃后无显著变化.硼酸钙促进莫来石相的析出,但硼酸钙含量过高时,会促进CaAl2Si2O8形成,降低莫来石相的析出量,并使其形貌从细针状向短柱状和粒状发生转变.硼酸钙掺量恒定时,提高烧结温度可促进细针状莫来石相的生成.     

滑动干摩擦条件下铸铁的摩擦学特性研究

系统地研究了铸铁材料在干滑动摩擦条件下的摩擦学特性。考察了铸铁石墨形态、合金元素及基体组织对其与钢配副时的滑动摩擦学特性的影响。研究结果表明：蠕墨铸铁具有良好的摩擦磨损特性；在铸铁中加入合金元素P和B可显著改善摩擦副的性能；同时，铸铁的基体组织对于摩擦磨损特性有十分显著的影响。     

Ti6A14V表面微弧氧化陶瓷涂层的结构和摩擦学特性

采用交流微弧氧化法，在Na2SiO3-(NaPO3)6-Na3MoO4溶液中制备了Ti6A14V表面氧化物陶瓷涂层，用X射线衍射仪、扫描电子显微镜和球-盘摩擦磨损试验机研究了涂层的结构、形貌及摩擦学性能，用纳米压痕仪测定了涂层致密层的硬度，用扫描电子显微镜观察涂层磨损表面形貌，用能谱仪分析涂层磨屑的元素组成．结果表明：厚约20pm的涂层致密均匀，主要由锐钛矿和金红石相氧化钛组成；涂层致密层的硬度约为13．5GPa；在0．5N低载荷和摩擦循环次数小于2000次条件下，涂层同GCrl5钢对摩时的摩擦系数仅为0．18～0．20，较基底Ti6A14V与其对摩的摩擦系数低得多．摩擦过程中较软的GCr15钢球材料向涂层表面转移，涂层的磨损机制主要是轻微磨粒磨损与粘着磨损．     

Effective elastic moduli of an inhomogeneous medium with cracks

In the present paper, the effective elastic moduli of an inhomogeneous medium with cracks are derived and obtained by taking into account its microstructural properties which involve the shape, size and distribution of cracks and the interaction between cracks. Numerical results for the periodic microstructure of different dimensions are presented. From the results obtained, it can be found that the distribution of cracks has a significant effect on the effective elastic moduli of the material. The project supported by the National Education Committee for Doctor     

新型精铸热锻模具钢高温磨损性能同其显微组织的相关性

研究了经不同热处理条件下的新型精铸热锻模具钢的组织同其高温磨损性能的相关性,对比分析了新型铸钢与H13锻钢的高温磨损性能,并探讨了其磨损机理.结果表明:新型精铸热锻模具钢的高温耐磨性能明显优于锻钢H13;在马氏体、贝氏体和马贝复相3种组织中,贝氏体和马贝复相的高温耐磨性能较好,马氏体相的高温耐磨性能最差;经过400～620℃回火处理的新型精铸热锻模具钢的硬度为42～43HRC,高温耐磨性能较好;当回火温度大于650℃或小于400℃时,新型精铸热锻模具钢的磨损率明显增大,耐磨性显著降低.     

利用分子动力学方法铁素体-渗碳体相界面效应探究

珠光体是十分重要的组织结构,因此本文构建了含铁素体-渗碳体相界面的模型,并采用分子动力学模拟方法模拟纳米压入的过程。通过对模拟结果的力学性能和组织结构分析,探究了铁素体-渗碳体相界面效应。研究发现,距铁素体-渗碳体晶界不同距离（位置压入）,在压入最初阶段,压头载荷随着压头与晶界距离的增大而增大,当压入深度达到一定深度后,载荷随着距离的增大而减小。杨氏模量和最大剪切模量受压头尖端下方原子结构的直接影响,硬度受到结构完整性和类型的共同影响。铁素体-渗碳体相界面影响了纳米压入过程中位错形核、增殖和扩展,宏观表现为在相同压入深度下,不同压入位置压头载荷的差异。     

Evaluation of Vetiver Volatile Compound Production under Aeroponic-Grown Conditions for the Perfume Industry

Vetiver (Chrysopogon zizanioides (L.) Roberty) is a major tropical perfume crop. Access to its essential oil (EO)-filled roots is nevertheless cumbersome and land-damaging. This study, therefore, evaluated the potential of vetiver cultivation under soilless high-pressure aeroponics (HPA) for volatile organic compound (VOC) production. The VOC accumulation in the roots was investigated by transmission electron microscopy, and the composition of these VOCs was analyzed by gas chromatography coupled with mass spectrometry (GC/MS) after sampling by headspace solid-phase microextraction (HS-SPME). The HPA-grown plants were compared to plants that had been grown in potting soil and under axenic conditions. The HPA-grown plants were stunted, demonstrating less root biomass than the plants that had been grown in potting soil. The roots were slender, thinner, more tapered, and lacked the typical vetiver fragrance. HPA cultivation massively impaired the accumulation of the less-volatile hydrocarbon and oxygenated sesquiterpenes that normally form most of the VOCs. The axenic, tissue-cultured plants followed a similar and more exacerbated trend. Ultrastructural analyses revealed that the HPA conditions altered root ontogeny, whereby the roots contained fewer EO-accumulating cells and hosted fewer and more immature intracellular EO droplets. These preliminary results allowed to conclude that HPA-cultivated vetiver suffers from altered development and root ontology disorders that prevent EO accumulation.     

Positron spectroscopy analysis in metallocene propylene/1‐octadecene copolymers: Parameters dependence on monoclinic and mesomorphic polymorphs

Copolymers of propylene and 1‐octadecene synthesized by a metallocene catalyst were characterized by PALS, WAXD, DSC, and density measurements. The change in the sizes and the number density of free‐volume holes as a function of the 1‐octadecene content were compared to the master laws published for copolymers of propylene with α‐olefins of shorter lengths. It was found that the samples were separated into two groups. The first set of samples obeyed the master laws while the second group deviated. This behavior was explained by the difference in the copolymer structure. The WAXD analysis confirmed the separation as well. The deviation was explained as due to the mesomorphic crystalline structure of the second group of samples, in contrast to the monoclinic one for the first group, which was a result of the relatively fast cooling from the molten state and from the high comonomer molar content. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1994–2002, 2010