shuangyu 材料的定義

1、Definition 材料的定義：The materials making up the surrounding world consist of discrete particles, having a submicroscopic size. Atomic structure and the nature of bonds(原子結(jié)構(gòu)和化學(xué)鍵) metals and their alloys (metallic bonding 金屬鍵) organic polymers 有機(jī)聚合物(covalent bonding and secondary bonding 共價(jià)鍵和二次鍵) ceramic

2、s (ionic bonding and covalent bonding) Mechanical properties：力學(xué)性能 Which reflect the behavior of materials, deformed by a set of forces （概念） Four basic types of stresses : tensile, compressive, shear ,torsion (拉力，壓力，剪切力，扭轉(zhuǎn)力) Physical properties:物理性能 the behavior of materials subjected to the action o

3、f temperature, electric or magnetic fields, or light. 電性能Electric properties 磁性能Magnetic properties 熱性能Thermal properties 光性能Optical properties Chemical properties:化學(xué)性能 Which characterize the behavior of material in a reactive environment. （概念） The four basic aspects of materials science and technol

4、ogy are: manufacturing processing, structure, properties and performances 結(jié)構(gòu)性能工藝之間的關(guān)系： First, the processing of a material affects the structure, second the original structure and properties determine how we can process the material to produce a desired shape 一、METAL:（金屬） 1、金屬最顯著的特性：good conductors

5、of heat and electricity (熱導(dǎo)性，電導(dǎo)性) 2、性能:are opaque to visible light; are hard, rigid; can undergo plastic deformation; have a high melting temperature 3、金屬的晶體點(diǎn)陣： crystal structure（晶體結(jié)構(gòu)） : body-centered cubic structure , face-centered cubic structure , hexagonal close-packed structure（體型、面型，六角形放射狀） 4、

6、properties of alloys（合金的性能） :(more carbon ,more brittle.) have relatively high thermal and electrical conductivities; good energy absorption characteristics nonmagnetic properties 5、鑄鐵概念：cast iron, essentially an alloy of iron, carbon and silicon, is composed of iron and from 2 to 6.67 percent carbo

7、n, plus manganese, sulfur, and phosphorus, and shaped by being cast in a mold. 6、The types and properties of cast iron ； white cast iron( hard , brittle ) , gray cast iron (brittle ,withstand large compressive loads but small tensile loads ), alloy cast iron , nodular or ductile cast iron (good cast

8、ability ,toughness, good wear resistance ,low melting point ,and hardenability ), malleable cast iron (strength ,toughness, ductility ,and machinability) 7、carbon steels（碳鋼）：low carbon steels（含碳0.050.32%）；medium carbon steels（含碳 0.350.55%）；high carbon steels（含碳0.601.50%） 8、不銹鋼：there are three types

9、of stainless steels: -the martensitic types；the ferritic types ；the austenitic types 9、advantages of using Al: one-third of the weight of steel good thermal and electrical conductivity ;high strength-to-weight ratio ;can be given a hard surface by anodizing and hard coating ;most alloys are weldable

10、 ;will not rust ;high reflectivity ;can be die cast ;easily machined ;good formability; nonmagnetic nontoxic and one third of the stiffness of steel. 10、copper is known for its high thermal (熱導(dǎo)性)and electrical conductivity. 11、crystal structure : body-centered cubic structure (barium), face-centered

11、 cubic structure (copper), hexagonal close-packed structure (zinc) 二、CERAMIC（陶瓷） 1、The property of ceramics （陶瓷的性質(zhì)） Extreme hardness（硬度高） Heat resistance Corrosion resistance Low electrical and thermal conductivity Low ductility (brittleness) 2、Porosity（孔隙度） Open porosity: refers to the network of p

12、ores in a material that is open to the surface and into which a liquid such as water can penetrate if the part were submerged in it。 Closed porosity: refers to those pores that have become sealed within the grain structure 。 Pores affect the strength of ceramics in two ways：（影響強(qiáng)度的毛孔陶瓷兩種方式） 、they pro

13、duce stress concentrations. Once the stress reaches a critical level, a crack will form and propagate. 、pores reduce the cross-sectional areas over which a load can be applied and, consequently, lower the stress that these materials can support。 Conventional ceramic processing（傳統(tǒng)陶瓷處理）； manufacture o

14、f the powder ,its calcinations ,milling ,grading and mixing ,incorporating additives ,shape forming , drying and densification. 三、GLASS（玻璃） 1、the measured mechanical strength of glass is much lower than the theoretical strength causes of this loss of strength ： 、the presence of surface defects, such

15、 as caused by chemical corrosion or mechanical abrasion。 、If the glass is cooled too rapidly it does not have time to release stresses set up within it during cooling . these are "frozen-in" and can cause the glass to shatter when it becomes a solid. the transparency is explained by two pr

16、operties : first ,it has no surface of internal structure which gives reflection or scattering。 second ,it has no free electrons which can interact with the electron magnetic nature of wave motion including visible light 五、POLYMER（聚合物） A Polymers is macromolecule (大分子）built up by the linking togethe

17、r of large numbers of much smaller molecules 性能：low strength,· low melting point · flexible· easily to be formed into different shapes Addition polymerization（加聚反應(yīng)） Here are three significant reactions that take place in addition polymerization: initiation, propagation, and terminatio

18、n. initiation (birth) 鏈引發(fā) propagation (growth) 鏈增長 termination (death) 鏈終止 Termination Reaction: Termination typically occurs in two ways:combination(偶合終止) and disproportionate(歧化終止) Combination occurs when the polymers growth is stopped by free electrons from two growing chains that join and form a

19、 single chain. 反應(yīng)式 Disproportionation halts the propagation reaction when a free radical strips a hydrogen atom from an active chain. A carbon-carbon double bond takes the place of the missing hydrogen. Living polymerization: There exists a type of addition polymerization that does not undergo a ter

20、mination reaction. This so-called “l(fā)iving polymerization” continues until the monomer supply has been exhausted Polymers vary in their mechanical behavior depending on the degree of crystallinity , degree of crosslinking, and the values of Tg and Tm. There are two types of plastics：flexible plastics

21、（柔性塑料） and rigid plastics（剛性塑料）. The flexible plastics possess moderate to high degrees of crystallinity and a wide range of Tm and Tg values. They have moderate to high tensile strengths, and ultimate elongation. The rigid plastics have high moduli and moderate to high tensile strengths, they under

22、go very small elongations before rupturing. Tm-polt of melt temperature Tg-glass transition temperature Tg/Tm=0.5-0.8 A highly flexible chain has a low Tg and strong intermolecular forces tend to raise Tg and also increase crystallinity, the controlling factor in determining Tg is chain flexibility

23、六、COMPOSITE（復(fù)合材料） Definition of Composite復(fù)合材料的定義）A composite is a combined material created by the synthetic assembly of two or more components a selected filler or reinforcing agent and a compatible matrix (基體) binder (e.g. a resin) in order to obtain specific characteristics and properties. Advantages of using Composites: Composites are superior to metals for many applications due to（優(yōu)點(diǎn)） High strengths Stiffnesses, Ease of moulding complex shapes High environ