已选分类
工学材料科学与工程
单选题在置换型固溶体中，原子扩散的方式一般为______。 (A) 原子互换机制 (B) 间隙机制 (C) 空位机制
单选题Vickers hardness numbers are a measure of the size of the penetration made by ______ with different loads. A) 10-mmsteelball B) tungsten carbide sphere C) diamond pyramid indentor D) diamond cone indentor
单选题多晶体塑性变形时，至少需要______独立的滑移系。
单选题从高分子(polymer)的重复结构单元(mer)的对称性可知，最易结晶(crystallization)的是______。
单选题在金属、陶瓷和高分子中最易结晶的是______。
单选题A key difference between a thermoplastic polymer and an elastomeric material like rubber is that ______. A．rubber has a relatively small number of covalent crosslinks and thermoplastic polymers have none B．thermoplastics dont melt when heated but rubbers do C．rubber can be subjected to extensive plastic deformation whereas typical thermoplastics have little plasticity D．all of the above
单选题The objective of vulcanizing rubber A．To improve processibility B．To increase hardness and chemical resistance C．To reduce materials cost D．To increase amorphousness
单选题硅酸盐熔体的粘度随碱金属氧化物含量的增加而迅速增大。
单选题Cu-Al合金和Cu焊接成的扩散偶发生柯肯达尔效应，发现原始标记面向Al-Cu合金一侧漂移，则两元素的扩散通量关系为______。
单选题A field that deals with developing, preparing, modifying, and applying materials to a specific need. A) Engineering Materials Technology B) Materials Engineering C) Materials Science D) Materials ScienceAnd Engineering
单选题六方晶系中晶面间距______晶面间距。
单选题铁素体(bcc，点阵常数ab=0.287nm)与奥氏体(fcc，点阵常数af=0.365nm)间可形成K-S关系([111]b∥[110]f，，则在半共格界面上沿[111]b方向上的位错间距为______。
单选题The maximum number of electrons in the N energy levelis ______. A) 2 B) 8 C) 18 D) 32
单选题______ is the most effective approach to making plastic more environmentally friendly. A) Using biodegradable plastics B) Using photodegradable plastics C) Recycling plastics D) Burning plastics for volume reduction and/or energy
单选题氯化铯(CsCl)为有序体心立方结构，它属于______。 (A) 体心立方点阵 (B) 面心立方点阵 (C) 简单立方点阵
单选题Chemical that serves as molecular matchmaker9 necessary to begin polymerization reaction. A．Monomer B．lsotope C．Catalyst D．Filler
单选题在点阵常数为a的体心立方结构中，伯氏矢量(Burgersvector)为a[100]的位错(dislocation)______分解为
单选题半结晶期是指______。
单选题过共析钢的正常淬火加热温度是( )。 A．Accm+(30～50)℃ B．Ac3+(30～50)℃ C．Ac1+(30～50)℃ D．Ac1-(30～50)℃
单选题
下述说法中哪种正确？
A、本征半导体是电子与空穴两种载流子同时参与导电，而杂质半导体(n型或P型)只有一种载流子(电子或空穴)参与导电，所以本征半导体导电性能比杂质半导体好。
B、n型半导体的导电性能优于p型半导体，因为n型半导体是负电子导电，p型半导体是正离子导电。
C、n型半导体中杂质原子所形成的局部能级靠近导带的底部，使局部能级中多余的电子容易被激发跃迁到导带中去，大大提高了半导体的导电性能。
D、p型半导体的导电机构完全决定于满带中空穴的运动。