A one-pot approach to dendritic star polymers via double click reactions

A class of well-defined dendritic star polymers with poly (ε-caprolactone) (PCLs) on the periphery has been prepared via one-pot double click reactions (Cu-catalyzed azide/alkyne click chemistry, i.e., CuAAC and Diels–Alder [4+2] cycloaddition reactions). The predecessors for Diels–Alder reaction, maleimide end-functionalized PCLs were produced by ring-opening polymerization (ROP). Obtained dendritic star polymers were characterized by ¹H NMR, size exclusion chromatography (SEC), UV/vis, and fluorescence spectroscopy.     

POE-g-MAH/OMMT对PA6的增韧机理研究

制备了马来酸酐接枝(乙烯/辛烯)共聚物(POE-g-MAH)/有机蒙脱土(OMMT)增韧粒子,并以其增韧尼龙(PA)6.研究表明,随着增韧粒子中OMMT含量的增加,PA6/POE-g-MAH/OMMT共混物的缺口冲击强度呈现先增加后降低的变化趋势.这一性能变化与增韧粒子中OMMT质量分数对增韧粒子分散粒径的影响密切相关.在增韧粒子质量分数相同的情况下,较小的分散粒径和基体韧带厚度,有利于基体韧带从平面应变状态到平面应力状态的转变,有利于基体塑性变形的发生,从而消耗较多能量,导致缺口冲击强度增加.     

Cu/Co/Cr Nanocomposites Obtained from Hydrotalcite Precursors as Catalysts for Thermal Decomposition of Ammonium Perchlorate

A series of Cu/Co/Cr nanocomposites with different Cu/Co/Cr molar ratios were obtained by calcination of Cu/Co/Cr hydrotalcites precursors,which were prepared by a co-precipitation reaction.X-ray diffraction,inductively coupled plasma analysis,and transmission electron microscopy were used to characterize the structure,composition,and morphology of Cu/Co/Cr nanocomposites.The results show that Cu/Co/Cr nanocomposites have both CuCr2O4and CoCr2O4spinel phase.The particle size of Cu/Co/Cr nanocomposites is 15–20 nm and the specific surface area is 95–115 m2/g.Cu/Co/Cr nanocomposites were used as new catalysts for improving thermal decomposition of ammonium perchlorate(AP).Their catalytic activities were investigated using differential thermal analysis and thermal gravimetric analyzer coupled with an online mass spectrometer.The results show that the decomposition temperature of AP lowered 132–146 °C by adding 4 wt% Cu/Co/Cr nanocomposites.Catalytic activities of the prepared nanocomposites depend on the calcinations temperature and addition amount of corresponding nanocomposites.The possible catalytic mechanism of Cu/Co/Cr nanocomposites was also studied and discussed.     

Rapid Hydrogen Transportation Along Grain Boundary in Nickel

The permeability and diffusivity of hydrogen in directionally solidified polycrystalline and single crystal nickel foils were measured by gas permeation method.The results showed that both hydrogen diffusivity and permeability were higher in directionally solidified nickel specimen than those in single crystal one at the temperature ranging from 300 to480 °C,and confirmed the existence of short-circuit diffusion along the grain boundaries(GBs) in the directionally solidified nickel.The results suggested that the rapid diffusion along GBs was more obviously characterized in terms of higher permeability rather than higher diffusivity.The contribution of grain boundary to hydrogen transportation was represented by the differences of diffusivity(and permeability) in single crystal nickel and directionally solidified nickel.By modifying the Fick's first diffusion law and counting the grain boundary density,the hydrogen diffusivity and permeability of rapid diffusion along GBs were calculated.The results suggested both the diffusivity and permeability fit the Arrhenius relationship well at different temperature.     

Fatigue damage study of cold metal transition fusion-brazed aluminium/steel dissimilar joints

ABSTRACT

An aluminium/steel CMT-welded joint is mainly composed of fusion zone (FZ), interfacial intermetallic compound (IMC) zone, and heat-affected zone (HAZ). IMC and FZ are the weakest link in the welded joint. The fatigue fracture indicates that the lattice distortion caused by the lattice mismatch of Fe₂Al₅ and Fe is more likely to engender dislocation slipping and cracks easily nucleate during the fatigue testing. The hysteresis loop is shifted to the right, which indicating that the specimen experiences a ratcheting effect. In the high-stress condition, the cyclic hardening induced by the ratcheting strain is much stronger than that in the lower stress condition, which improves the fatigue life of the materials.     

基于仿生结构的Al-Ti-Ti2AlNb层状复合材料的组织与力学性能

受生物材料的韧脆复合结构的启发,本文将Al箔、Ti箔和Ti2AlNb箔材堆叠排列,采真空热压烧结技术制备了层级结构的Al-Ti-Ti2AlNb层状复合材料。利用SEM、XRD等技术表征了材料的微观结构,并测试了抗弯与抗压性能。研究发现,本文设计的层状结构复合了Ti、TiAl系列间化合物、Ti2AlNb等多种材料,层级结构明显,界面清晰。抗弯强度与抗压强度分别为1231±71MPa和1341±63MPa,相比同类材料具有显著的优势。分析认为,多层级结构的存在对裂纹的扩展有显著地阻碍作用;相比常规的二元TiAl层状材料,Ti2AlNb层的存在显著提高了力学性能。     

基于SolidWorks Motion的车辆自动跟随行驶仿真

随着汽车产业与互联网的发展,依靠计算机系统智能驾驶替代人工驾驶已成为汽车发展的新趋势;ACC自适应巡航技术虽然依旧需要人工驾驶,但可使用电控程序解决车辆在车流中保持合理的跟车间距。基于无人驾驶和自适应巡航的理论基础,提出一种介于两者之间的行驶模式,即在两辆车同向行驶时,前车人工驾驶,后车自动跟随行驶,并采用Solidworks进行车辆三维建模;并用Motion运动仿真插件模拟车辆前车在加速、减速、匀速直线及弯道转向运动状态,观察后车跟随情况,获得了相应的车辆跟随动力学仿真结果。     

火力发电厂反渗透法海水淡化系统设计研究

阐述了火电厂独有的有利于海水淡化的各种因素,分析了常规反渗透海水淡化的设计条件,并对火电厂反渗透海水淡化系统设计进行了研究.火电厂建反渗透海水淡化装置,可大大降低取水及浓水排放系统的投资,并可减少反渗透海水淡化膜元件数量,对生态环境的影响也小,可以优先发展.     

奈非西坦的合成研究

奈非西坦是新研制的一种对阿尔茨海默氏病和脑血管后遗症有良好的临床治疗价值的药物。对奈非西坦的各种合成方法进行了总结,分析了各路线的优缺点,并对奈非西坦的药理学内容做了概述。     

整体式无痕注塑模芯的快速成型工艺

详细阐述了以SRW金属粉末快速成型毛坯,然后经过热处理及精加工制作整体式无痕注塑模具模芯的过程,并以实例对制作过程进行了研究。结果表明,利用该工艺制造的模芯,其致密度接近理想密度,机械性能达到模具的设计要求。