1、Unit 5: materials science 材料科学,What materials do you know?,wood plastic iron steel glass -,What are materials, exactly?,Thats a big question - because materialsare the basic substances that make up, well, you name it! Materials can be natural - like wood, or human-made - like plastic. There are now
2、about 300,000 different known materials (if you named one every second, it would take you more than three whole days and nights just to get through the list!). And as materials scientists create and combine materials in new ways, the numbers almost infinite.,What are materials, exactly?,Most materia
3、ls fit into a few big, general categories metal ceramic 陶瓷polymer 聚合物semiconductor 半导体composite 复合材料biomaterial 生物材料,. Metal,Can you list some metals?,iron steel copper silver gold lead aluminum -,What is alloy (合金)?,The presence of other elements in the metal can also change its properties, sometim
4、es drastically. Mixtures of metals are called alloys.,Composition of several alloys,What properties (性能) do metals have?,hard strong conductor of electricity conductor of heat malleable 有延展性的,What are some applications of metals?,Transportation - Cars, buses, trucks, trains, ships, and airplanes. Ae
5、rospace - Unmanned and manned rockets and the space shuttle. Computers and other electronic devices that require conductors (TV, radio, stereo, calculators, security devices, etc.) Communications including satellites that depend on a tough but light metal shell. Food processing and preservation - Mi
6、crowave and conventional ovens and refrigerators and freezers. Construction - Nails in conventional lumber construction and structural steel in buildings.,Biomedical applications - As artificial replacement for joints(关节). Electrical power production and distribution - Boilers, turbines, generators,
7、 transformers, power lines, nuclear reactors, oil wells, and pipelines. Farming Tractors（拖拉机), combines（收割机）, planters, etc. Household conveniences - Ovens, dish and clothes washers, vacuum cleaners, blenders, pumps, lawn mowers and water heaters, heating/cooling, etc.,. Ceramic,Can you list some ex
8、ample of the use of ceramic?,dish ceramic tile 瓷砖-,What Are Ceramics?,It is a hard, inorganic(无机的), and nonmetallic(非金属) material . Traditional ceramic: clay products, cement (水泥) Advanced ceramic,Properties of ceramic,hard strong brittle electricity insulatorheat insulator high melting point corros
9、ion resistance,Application of ceramic,. polymer 聚合物,Application of polymer,What objects in our daily life are made from polymer?,French fries are loaded with a polymer called starch (淀粉), which your body digests into sugar to use as fuel.,Burgers are full of proteins(蛋白质), which your body uses to bu
10、ild and repair itself.,Fast food often comes in boxes made of polystyrene(聚苯乙烯) foam(泡沫).,Many are made from leather(皮革), which is one of many natural polymers. This running shoe has panels(鞋面) made of leather, and also of nylon(尼龙). The sole(鞋底) is made out of a hard rubber called SBS rubber.,Even
11、shoe laces(鞋带) are made from polymers, like nylon and cotton. Cotton is a form of a natural polymer.,We wouldnt have these socks without polymers like cotton, and synthetics(人工合成材料) like polyester (涤纶)and nylon.,Sweaters like these can be made from wool. Sweaters can also be made of cotton or rayon
12、(人造纤维).,A lot of auto body parts are made out of polymer like acrylonitrile-butadiene-styrene plastic, called ABS for short. Using ABS plastic in body parts makes cars lighter so they use less gas and pollute less. This front bumper(前保险杆) is so light that we can lift it with one hand!,This tire is m
13、ade of three kinds of rubber! The tread (胎面) is made from SBS rubber. The sidewalls are made of another rubber called polyisoprene(聚异戊二烯). And the inner liner is made of another kind of rubber called polyisobutylene(聚异丁烯).,This basketball has a cover made from leather, a natural polymer. To help it
14、hold air it has an inner liner(里衬) made from a kind of rubber.,Properties of polymer,Compared with other materials, polymer is： light hard to break long-lasting recyclable easy to form into shapes cheap,What is biomaterial?,Biomaterial can be defined as any material that serves medical purposes.,Wha
15、t materials can be used as biomaterial?,polymer ceramic metal,Artificial limb must be light and flexible to permit easy movement, but must also be able to support the weight of the body or to Manipulate(操作) objects. The materials used in artificial limbs include willow(柳树) wood, fibers and plastics,
16、 various metallic alloys, and carbon-fiber composites.,An artificial heart is made out of metal, plastic, ceramic, and animal parts.,What is composite?,Composite materials are formed by combining two or more materials that have quite different properties. The different materials work together to giv
17、e the composite unique properties.,Composites exist in nature. A piece of wood is a composite, with long fibres of cellulose (纤维素, a very complex form of starch) held together by a substance called lignin(木质浆).,If you embed pieces of straw(稻草) in a block of mud(泥) and let it dry hard, the resulting
18、mud brick resists both squeezing(挤压) and tearing(撕裂) and makes an excellent building material.,Another well-known composite is concrete. Here small stones is bound together by cement(水泥). Concrete has good strength under compression, and it can be made stronger under tension by adding metal rods, wi
19、res, mesh or cables to the composite (so creating reinforced concrete).,What is semiconductor?,Semiconductors are materials which have a conductivity between conductors (generally metals) and nonconductors or insulators (such as most ceramics). Silicon 硅,Text A: Materials science and engineering:An
20、exciting career field for the future,We are constantly reminded that we live in a world that is both dependent on and limited by materials.很多东西不断的提醒我们，我们所生活的世界 既依赖于各种材料又受到他们的限制。,All of these require materials specifically tailored for their application.制造这些东西都要根据他们的用途选择适当的材料。,Specific properties are
21、 required that result from carefully selecting the materials and from controlling the manufacturing processes used to convert the basic materials into the final engineered product.通过精心选择原材料和控制将原材料变成成品的生产过程，就可以获得所需特性的材料。,The activities of these engineers range from primary materials production, inclu
22、ding recycling, through the design and development of new materials to the reliable and economical processing/manufacturing for the final product. 这些工程师的工作包括: 通过研发新材料（包括循环利用）来生产重要材料，通过稳定经济的生产加工过程得到成品。,Many applications are limited by the operating constraints imposed by the properties or behavior of
23、 the materials available. 很多生产加工都受到现有材料的限制。,While much attention is being focused on developing metals, ceramics, polymers, and composites with improved properties, the ability to actually engineer, or create, materials to meet specific needs is just now being realized.,Topics,Talk about the materia
24、ls you know, including their applications and properties talk about nanomaterial. talk about the importance of materials science. talk about what you have learned in this unit.,Reference,http:/matse1.mse.uiuc.edu/ http:/www.whystudymaterials.ac.uk/index.asp http:/ http:/www.ccmr.cornell.edu/education/ret/terrih/quiz.html http:/claweb.cla.unipd.it/home/mcanapero/exercises/materials.htm http:/pslc.ws/macrog/kidsmac/index.htm,
