文档介绍：第一章材料
Definition ;Types;Structure ;Structure-properties-processing
材料的重要性:材料的发展史,就是人类社会的发展史。
影响材料使用的因素
Materials Behavior;Available;Cost;Synthesis and production;method Processing techniques; Environmental acceptability
Characteristics of materials
Have positions; Can be processed;With certain shape and color;Can be used and reused or :具有一定的成分和配比;可成型加工;保持一定形状和外观;具有使用价值并可回收再利用。
Essential role of materials
Indispensable to our society:Food ,Energy, Transportation
Substances VS Materials:Substances That which has mass and occupies space; matter.
Materials The substance or substances out of which a stuff is made.
材料性能的决定因素:组成材料的各元素的原子结构Atomic structure;原子间的相互作用、相互结合Nature of chemical bonds;原子或分子在空间的排列分布和运动规律Atomic ordering;原子集合体的形貌特征Microstructure;
Nature of chemical bonds:
Metallic bond 金属键;Ionic bond 离子键;Covalent bond 共价键;Secondary bond次价键;Van der waals bond范德华力;Hydrogen bond氢键;
金属键既无饱和性又无方向性,每个原子有可能同更多的原子相结合,并趋于形成低能量的密堆结构。当金属受力变形而改变原子之间的相互位置时,不至于使金属键破坏。良好延展性;良好的导电性能;良好的导热性能
离子键一般离子晶体中正负离子静电引力较强,结合牢固。因此,其熔点和硬度均较高。另外,在离子晶体中很难产生自由运动的电子。它们都是良好的绝缘体。但当处在高温熔融状态时,正负离子在外电场作用下可以自由运动,即呈现离子导电。
共价键共价键在亚金属(碳、硅、锡、锗等)、聚合物和无机非金属材料中占有重要地位。共价键晶体中各个键之间都有确定的方位,配位数比较小。共价键的结合极为牢固。共价晶体具有结构稳定、熔点高、质硬脆等特点。共价形成的材料一般是绝缘体,其导电性能差。
Classification:Metals and their alloys:-metallic bonding
Organic polymers Covalent bonding & secondary bonding
ceramics/ anic nonmetallic materials Ionic bonding & covalent bonding
Metals and their alloys:
Are good conductors of heat and electricity;Are opaque(遮蔽性的) to visible light;Are hard, rigid;Can undergo plastic deformationHave high melting temperatures (Tm).
Organic polymers:Made up of long-chain molecules;Are electrical and thermal insulators;Are light and easily formed;he best-anic polymers are: poly (vinyl chloride)(聚***乙烯,PVC);polyethylene(聚乙烯,PE);polystyrene(聚苯乙烯,PS)。
Ceramics / anic nonmetallic materials:
bination of metallic elements (Mg, Al, Ti,…) with non-metallic elements (O…);Have high mechanical properties;Are very ha