Thermal Behavior of Polypropylene-g-glycidyl Methacrylate Prepared by Melt Grafting

The thermal behaviors of glycidyl methacrylate (GMA)-grafted polypropylene (PP) (PP-g-GMA) with two different grafting degrees, namely, GPP1 and GPP2, were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), dynamic mechanical analysis (DMA), and thermogravimetrical analysis (TGA). DSC results suggested that the GMA grafted PP exhibited higher crystallization temperature T_c, higher melting temperature T_m, and higher crystallinity compared with the neat PP. The isothermal crystallization kinetics was analyzed with the Avrami equation and the total crystallization activation energy was calculated. It was concluded that the crystallization processes of PP and the grafted PP were controlled by nucleation and the values of the crystallization activation energy of PP and the grafted PP were almost identical. POM results suggested that the GMA grafted PP exhibited smaller spherulites size compared with the neat PP. WAXD patterns indicated that the neat PP encouraged the formation of γ phase, compared with the grafted PP, during the crystallization process. DMA results showed that melt grafting did not induce a clear effect on the γ-transition and β-transition of the amorphous phase but resulted in a decrease in mobility of the PP chains in the crystals. TGA curves suggested that the melt grafting slightly improved the thermal stability of PP.     

铜锌锡硫薄膜材料及其器件应用研究进展

铜锌锡硫薄膜材料组成元素储量丰富, 环境友好, 成本低廉, 成为最具前景的薄膜材料之一. 目前, Cu₂ZnSn(S, Se)₄ (CZTSSe)薄膜太阳电池的最高转换效率已经达到12.6%. 本文总结了Cu₂ZnSnS₄ (CZTS)的发展历史, 依次介绍了CZTS薄膜材料的结构特性、光学特性、电学特性、界面特性和Na对CZTS 薄膜的影响, 详细介绍了CZTS薄膜的制备方法及器件应用的最新研究进展, 总结了目前CZTS薄膜太阳电池发展中存在的问题, 展望了今后的研究方向.     

大散射角散斑场中有关相位奇异新特性的研究

利用散斑场和参考光的干涉提取散斑场复振幅和相位, 研究了不同散射角下散斑场相位的分布规律以及相位奇异处光波复振幅实部零值线和虚部零值线夹角、光强等值线离心率的统计特性. 在大散射角散斑中发现了一种新的相位奇异现象, 即相位奇异线; 研究了相位在跨越奇异线时的突变规律及涡旋状相位的分布特征, 发现在相位奇异线处存在着呈双曲线或抛物线状的光强等值线.     

石墨烯基双曲色散特异材料的负折射与体等离子体性质

基于有效介质理论研究了石墨烯/介质周期结构的电磁性质, 研究发现这种复合结构的等频面在太赫兹和远红外波段为双曲线, 可用来实现石墨烯基双曲色散特异材料. 通过改变石墨烯的费米能级、介质层厚度和单元结构中石墨烯的层数, 可很容易地调节双曲色散存在的频段. 由于等频面的双曲色散特性, 石墨烯基双曲色散特异材料在远低于截止频率的范围内, 对斜入射的电磁波具有负的能量折射率和正的相位折射率, 并支持局域体等离子体模式. 基于衰减全反射结构, 研究了体等离子体的激发, 探索了体等离子体在可调的光学反射调制器中的应用.     

Study on LiFe<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sm<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>PO<Subscript>4</Subscript>/C used as cathode materials for lithium-ion batteries with low Sm component

LiFe_1???x Sm _x PO₄/C cathode materials were synthesized though a facile hydrothermal method. Compared with high-temperature solid-phase sintering, the method can allow for the fabrication of low Sm content (2 %), a scarce and expensive rare earth element, while the presence of an optimized carbon coating with large amount of sp²-type carbon sharply increases the material’s electrochemical performance. The high-rate dischargeability at 5 C, as well as the exchange current density, can be increased by 21 and 86 %, respectively, which were attributed to the fine size and the large cell parameter a/c as much. It should be pointed out that the a/c value will be increased for the LiFePO₄ Sm-doped papered by both of the two methods, while the mechanism is different: The value c is increased for the front and the value a is decreased for the latter, respectively.     

采动诱发岩体移动破坏过程数值模拟研究

本文基于岩石介质的宏观非线性主要是由非均质性和各向异性造成的, 应用新的数值计算软件RFPA(2D), 对采动引起岩体失稳破坏的全过程进了数值模拟研究。     

DISTRIBUTION OF RANDOM ELEMENTS SUBJECTED TO A FLEXIBLE BOUNDARY CONDITION

The probability distribution function of n random elements subjected to the flexible boundary condition is derived. The probability density is a descending curve and converges to a delta function as n tends to infinity. The distribution of the minimum value is discussed in context of ordered statistics.     

一些磷－氮型极压抗磨添加剂性能的研究

合成了一些磷－氮型极压抗磨添加剂烷基亚磷酸酯胺盐和氮杂环胺盐，并对其油溶性和润滑性等进行了试验研究。结果表明，磷－氮型极压抗磨添加剂的化学结构对其油溶性和极压抗磨性都有较大的影响：烷基链增长有助于油溶性的改善，氮杂环胺盐的油溶性更好；伯胺盐的抗磨性比仲胺盐和叔胺盐的都好，氮杂环胺盐的抗磨性更好；磷－氮型极压抗磨添加剂的减摩性明显比硫化烯烃、烷基亚磷酸酯和苯三唑十八胺的都好，有的在２５０℃时的摩擦系数仅约为０．０４．Ｘ射线光电子能谱和俄歇电子能谱分析发现，磷－氮型极压抗磨添加剂在摩擦表面形成了一种含氮富磷的化学反应膜。其中，元素磷是以磷酸铁的化合态形式存在，而元素氮则是以其原有的价态形式存在，这表明氮参与了整个摩擦过程。在试验研究和分析讨论的基础上，通过综合归纳还提出了磷－氮型极压抗磨添加剂的作用机理模式图。     

航空发动机压气机叶片振动频率与温度的关系

以某型航空发动机压气机第六级叶片为例，研究了温度对叶片振动频率的影响。发现由于温度的升高导致了材料弹性模量的下降，而弹性模量的下降又导致了叶片在发动机一定的转速范围内，除一阶振动外，其余各阶振动的动频均小于静频，因此与通常的工程处理方法不同，研究压气机叶片的动频时，应考虑温度的影响。