已选分类
工学
单选题Recycling a thermoplastic polymer is possible, because ______ . A．different polymer chains in a thermoplastic are held together by relatively weak Van der Waals bonds which can be broken at relatively low temperatures B．thermoplastics are only lightly crosslinked in comparison to thermosets C．both of the above D．neither of the above
单选题Which of the following is the type ofbond between molecules of water? A) Ionicbond B) Covalentbond C) Hydrogenbond D) Metallicbond
单选题调幅分解(spinodal decmnposition)是经过______方式形成。
单选题在扩散系数的热力学关系中，称为扩散系数的热力学因子。在非理想混合体系中：
当扩散系数的热力学因子＞0时，扩散结果使溶质______；
当扩散系数的热力学因子＜0时，扩散结果使溶质______。
a．发生偏聚 b．浓度不改变c．浓度趋于均匀
单选题Which term describes the behavior of materials when subjected to some external force or condition? A) Material B) Property C) Automation D) Synthesis
单选题在晶体中形成空位的同时又产生间隙原子，这样的缺陷称为______。 (A) 肖特基缺陷 (B) 弗仑克尔缺陷 (C) 线缺陷
单选题现有下列铸铁：HT250、KTH350-10、QT600-2，请按用途选材。 A．制作机床床身，可选( ) B．制作柴油机曲轴，可选( ) C．制作汽车后桥外壳，可选( )。
单选题______，位错滑移的派一纳力越小。
单选题离子晶体通常借助表面离子的极化变形和重排来降低其表面能，对于下列离子晶体的表面能，最小的是______。
A.CaF2
B.PbF2
C.Pbl2
D.BaSO4
E.SrSO4
单选题Which advantage do smart polymeric materials offer designers? A) Eliminate selection problems B) Reduce raw materials costs C) Adapt to environmental changes D) Reduce processing
单选题泥浆胶溶必须使介质呈______，还必须有______价阳离子交换粘土中原来吸附的阳离子。
A.酸性
B.碱性
C.中性
D.一价
E.二价
F.三价
单选题Four quantum numbers characterize an electron as to its size, shape, and spatial orientation. The number ofenergy states for each orbital is determined by ______. A) The principal quantum number B) The second quantum number C) The third quantum number D) The fourth quantum number
单选题在定向凝固中，希望获得最大程度的提纯，有效分配系数应该______。
单选题对Fe-Cr-C三元系合金进行渗C的反应扩散，则该合金中不能出现______。
单选题Anaerobic adhesives set up into hard, strong adhesives when ______. A．The two parts of resin and catalyst are mixed B．Squeezed into thin joints which block the oxygen C．The solvents evaporate or penetrate porous adherends D．The heat source is removed
单选题铸铁(cast iron)与碳钢(carbon steel)的区别在于有无______。
单选题Which term describes well-defined methods for solving specific problems, such as those used to develop an approach to materials selection? A) JIT B) Design C) Algorithm D) CIM
单选题合金在凝固时产生成分过冷的条件是______。(其中TL是成分为CL的合金开始凝固温度)
单选题立方晶体中(110)和(211)面同属于______晶带。
单选题Trade name for aramid fiber, which is used for bulletproof vests and advanced composites for aerospace applications. A) E-glass B) Kevlar C) Borsic D) Graphite