Preparation of organic vermiculite/polymethylmethacrylate nanocomposite featuring excellent mechanical and thermal properties via ultrasonic in situ polymerisation

To improve the dispersion of organically modified vermiculite (OVMT) in polymethylmethacrylate (PMMA), the method of ultrasonic in situ polymerization was introduced, and a series of OVMT/PMMA nanocomposites were successfully prepared. The structure, morphology, and mechanical and thermal properties of as-prepared sample had been investigated. Results showed that the assistance of ultrasonic irradiation could be beneficial for the good homogeneous dispersion and strong interfacial interaction of OVMT in PMMA. Consequently, the obtained nanocomposites showed better mechanical and thermal properties than those prepared without the assistance of ultrasonic irradiation. When the OVMT content was 3 wt.%, the nanocomposite prepared by ultrasonic in situ polymerization exhibited the Young's modulus, tensile strength, elongation at break and degradation temperatures for 5% and 50% weight loss of 1177 MPa, 65 MPa, 14%, 219.82ºC and 373.91ºC, respectively. These results suggested the great potential application of ultrasonic in situ polymerization for the synthesis of polymer/clay nanocomposite.     

粒子群算法对织构分析改进最大熵法的改进

将粒子群算法(PSO)成功地应用于改进最大熵法(MMEM),使用两张或单张部分极图数据,即可测算出多组具有宏观对称的冷轧纯铜片样品的完整晶粒取向分布(ODF).这一改进保留了原MMEM的特长,用较少的实验数据即可计算出样品的真ODF,而又消除了原法在求解非线性方程组时需要选取特定初解的困难,从而使MMEM更具普适性和实用性.     

单晶体Cd1-xMnxTe中的法拉第旋转

室温下测量了本实验室生长的Cd0.8Mn0.2Te和Cd0.9Mn0.1Te单晶体的法拉第旋转谱.通过提高布里渊区中心L点的能隙值(E1)改进了法拉第旋转的多振子模型.用改进的模型拟合实验结果,得到Cd0.8Mn0.2Te和Cd0.9Mn0.1Te单晶体布里渊区中心F点的能隙值(E0)分别为1.804 eV和1.667 eV.该E0值比以往任何研究都更接近于计算值.     

预置活性物前驱体脉冲电沉积制备DMFC电极

预先将活性物前驱体置于碳黑层的Nafion微粒体内,利用脉冲电沉积法,使Pt或Pt合金优先沉积于Nafion与碳黑的接合部,以提高催化剂层贵金属的有效率.实验采用循环伏安法(CV)测定电极电催化活性,用XRD、EDS、TEM技术表征催化剂微观结构及金属微粒的元素组成.结果表明,toff/ton=3:1,WPtRu/wc=40%,Pt、Ru原子比为1:1,金属微粒的比表面积为92 m2·g-1、粒径为3.2nm,甲醇峰电流密度达到82 mA·cm-2,活性物的有效率达到79.1%.     

带状电极MAG焊电弧行为

用高速摄像系统和电流电压采集模块对带状电极MAG焊工艺电弧行为进行了研究.结果表明,带状电极MAG焊电弧呈非柱对称分布,电弧截面从钢带端部到母材逐渐由椭圆形过渡到圆形.随焊接工艺参数的增大,电弧能量提高,钢带端部由多个电弧共存转变为一个电弧燃烧,电弧沿钢带无规律的紊乱运动转变为较稳定的左右摆动,进而转变为不发生明显摆动...     

纳米结构尖晶石型锂离子电池电极材料的研究进展

综述了近年来纳米结构尖晶石型锂离子电池电极材料（LiMn2O4、LiNi0.5Mn1.5O4和Li4Ti5O12）的研究进展,重点对纳米结构与电化学性能之间的关联性进行了总结和探讨,并对纳米结构电极材料的发展前景进行了展望。     

金电极自组装基因分子膜的制备及电化学检测

采用分子自组装技术制备巯基修饰的基因分子膜修饰金电极,用于竞争式杂交检测黄孢原毛平革菌木素过氧化物酶编码基因。通过差分脉冲伏安法、循环伏安法、交流阻抗法和电流—时间曲线法优化自组装时间和信号探针的最佳响应浓度,研究目标基因的线性检测范围和再生性能。结果表明:修饰金电极最优自组装时间为15 h,信号探针的最佳响应浓度为0.51×10-6 mol/L,目标基因的线性检测范围为7.51×10-12-1.05×10-9 mol/L,检测下限为7.51×10-13 mol/L。该修饰电极具有良好的再生性能。     

CO2气硬改性PVA粘结剂的制备与工艺性能研究

开发优质高效、节能环保的新型粘结剂是当前铸造绿色化发展的迫切需要.以抗压强度为主要考察目标,通过探索性试验与正交试验,优化改性结果,确定粘结剂的制备工艺,并对聚乙烯醇砂的可使用时间、发气性、溃散性和粘结剂加入量等工艺性能进行研究.试验结果表明,改性PVA粘结剂制得的砂型具有良好的工艺性能,吹入CO2气体后,可以获得较高的初强度和终强度.     

Prevention of liquid metal embrittlement cracks in resistance spot welds by adaption of electrode geometry

ABSTRACT

Advanced high strength steels are usually coated by a zinc layer for an increased resistance against corrosion. During the resistance spot welding of zinc coated steel grades, liquid metal embrittlement (LME) may occur. As a result, cracking inside and around the spot weld indentation is observable. The extent of LME cracks is influenced by a variety of different factors. In this study, the impact of the used electrode geometry is investigated over a stepwise varied weld time. A spot welding finite element simulation is used to analyse and explain the observed effects. Results show significant differences especially for highly increased weld times. Based on identical overall dimensions, electrode geometries with a larger working plane allow for longer weld times, while still preventing LME within the investigated material and maintaining accessibility.     

电火花成形加工工具电极损耗预测

电火花成形加工过程中,极间放电在蚀除工件材料的同时,也会对工具电极带来一定程度的损耗,进而影响工件的尺寸及形状精度,降低加工效率。目前普遍采用更换电极重复加工的方式来获得最终形面,需要消耗大量的工具电极和工时。针对电火花加工的工具电极损耗展开了研究,通过系统地分析所得电极形面特征及进给方向与损耗量之间的关系,建立了实用的电极损耗预测模型。通过实验证明了该模型能准确预测工具电极形面损耗,为电火花加工的电极损耗预测提供了有效方法。