Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
De re metallica wikipedia , lookup
Shape-memory alloy wikipedia , lookup
Carbon nanotubes in interconnects wikipedia , lookup
Electromigration wikipedia , lookup
Crystal structure wikipedia , lookup
Work hardening wikipedia , lookup
Glass-to-metal seal wikipedia , lookup
Glass transition wikipedia , lookup
Metals Aluminium Aluminium is a metallic element. It is a soft metal with a silvery appearance. Aluminium exists in a metal lattice structure as Al3+ ions in a 'sea' of electrons where the bonding between the ions and the free electrons is very strong. This gives the aluminium a tightly bound metallic lattice making the melting point of aluminium very high. Aluminium has a low density, high electrical and thermal conductivity and excellent corrosion resistance. It has a high strength-to-weight ratio. Although it is a good conductor of heat it will reflect up to 90% of radiant heat. It is used for engine parts, aircraft structures, cooking utensils, drink cans, aluminium foil for heat reflection, window and door frames. Chromium Chromium is a transition element. It is a hard silvery metal and pure chromium exists as a typical metal lattice. That is, the metal consists of chromium ions in a sea of electrons. Chromium can have more than one valency. The main oxidation states of chromium in its compounds are +3 and +6. Chromium is a shiny metal that does not oxidise or corrode easily; it is brittle with a high melting point. It is used in alloys such as stainless steel and high strength and heat resistant alloys. It is used in cooking utensils, and as plating on bicycle handle bars and car parts. Copper Copper is a red-brown transition element. The metal is composed of copper ions in a sea of electrons, forming the metal lattice. Compounds of copper contain the metal in the +1 or +2 valency state. The +2 oxidation state is the more stable of the two. The metal is resistant to corrosion and has low electrical resistance and good thermal conductivity. It is easily worked and can be joined by soldering, brazing and welding. It is used in water pipes, electrical wires and in alloys. Gold Gold is a transition metal. It exists, like other metals, in a metallic lattice structure as close packed ions in a sea of electrons. Gold is a very unreactive metal but can form compounds. The compounds of gold are strong oxidising agents. In these compounds gold can exist in the +1 or +3 valency states. Gold is very ductile and worked easily. It has good electrical and thermal conductivity. Gold is used as currency and used in electronic micro circuits. Gold resists infrared radiation, so if a little is added to glass or plastic an effective heat shield can be formed. Being unreactive it is used in dental work and in plating corrosive containers as well as in jewellery. Iron Iron is a silvery transition element. Pure iron exists in a metallic crystal structure. In the metallic lattice the iron atoms are ionised forming ions and are closely packed together. Electrons form a sea around these ions. Iron can have a valency of +2 or +3. Iron is used in alloys such as carbon steels, cast irons, alloy steels and stainless steels. Mild steels are used for joists in buildings, bodywork for cars and ships, screws, nails and wire. Medium-carbon steels are used for shafts and parts in car transmissions, suspensions and steering. High-carbon steels are used for machine tools, saws, axes, cold chisels, punches and drills. Stainless steels are high alloy steels with more than 12% chromium. They are used where high corrosion is required in chemical and food-processing equipment. Cast iron is hard and brittle. They are used for machine castings, manhole covers, heavy-duty piping and machine tool beds. Lead Lead is a soft metal. It is a silvery metal but usually appears dull grey due to its reaction with air. The lead atoms exist in a metallic crystal lattice in which the lead exists as ions in a sea of electrons. It has a valency of +2 when forming its compounds. Lead is highly resistant to corrosion, has a low melting point and is electrically conductive. It is very dense and malleable. Lead is used in lead acid batteries, water pipes, as an electrical insulator, in roofing noise insulation and in paint pigments. Nickel Nickel exists, like other metals, in a metallic lattice structure as close packed ions in a sea of electrons. Nickel is used for a number of alloys with excellent corrosion resistance and strength at high temperatures. The alloys are basically nickel-copper and nickel-chromium-iron. They are used for pipes and containers in the chemical industry where high resistance to corrosive atmospheres is required, food-processing equipment, and applications, such as gas turbine blades and parts, where strength at high temperatures is required. Silver Silver is a soft metallic transition element. It exists, when pure, in a metallic lattice structure. In the metal lattice, the silver ionises and the silver ions pack closely together in a sea of electrons. Silver is not very reactive. In its compounds it has a valency of +1, forming the ion Ag+. Silver has a high thermal and electrical conductivity, and is very soft and ductile. It has high reflectivity. Silver is used in jewellery and the photographic industry as certain silver compounds darken when exposed to light. Silver is the best conductor known to man so the electronics industry uses it in nearly all its products. Silver batteries are smaller and more powerful than conventional batteries so are ideal for hearing aids, cameras and even space satellites. In powdered form it is an excellent catalyst used in industrial alcohols, solvents and with ammonia compounds to produce fertilizers. Silver is useful in medicine as it absorbs the oxygen that germs need to live and therefore kills them. Surgeon's instruments are often made from silver to reduce the chance of infection, and silver wire and plates can be used to repair broken limbs. Tooth fillings are made out of a silver, tin and mercury compound. Tin Tin is a silvery-white element. It exists in a crystal lattice structure as tin ions in a sea of negative electrons. In its compounds, tin can appear in the +2 or +4 valency states. Tin has a low tensile strength, is fairly soft and can be very easily cut. Tin plate is steel plate coated with tin, the tin conferring good corrosion resistance. Solders are essentially tin alloyed with lead and sometimes antimony. Tin alloyed with copper and antimony gives a material widely used for bearing surfaces. Zinc Zinc is a blue white transition metal. Pure zinc is found as a metallic crystal structure with ions of zinc packed together in a sea of electrons. When forming compounds zinc forms the Zn2+ ion. Zinc has very good corrosion resistance and hence finds a use as a coating for steel, the product being called galvanised steel. It has a low melting point and hence zinc alloys are used for products such as small toys, cogs, shafts, door handles. It is also used in battery electrodes, coinage and in paint. Polymers Acetate Acetate, which is really called cellulose acetate, can be produced as long, strong fibres (known as rayon, dicel or tricel) similar in feel to natural fibres, and is widely used in clothing. Cellulose fibres are used to produce filter tips for cigarettes. A sheet form of cellulose acetate is called Clarifoil. This is a transparent film used to give a shiny finish to cosmetics packs and high quality print brochures and magazines. It is also used in adhesive tapes, labels and as photographic and cinema film. A further form of cellulose is Dexel, which can be produced in a variety of colours and moulded into many different shapes. It is used to manufacture plastic products such as tool handles, combs, toothbrush handles, goggles, masks and spectacle frames. Bakelite Bakelite is a thermoset and is hard, rigid and is a good electrical insulator. It is low cost and has good heat resistance and water resistance. It is used for electrical plugs and sockets, switches, door knobs and handles. Epoxy Epoxy resins are thermosets which are used with glass fibres to form composites or laminates with high strength and stiffness. Ethylene Ethylene vinyl acetate is an elastomer that has good flexibility, impact strength and electrical insulation properties. It is used for cable insulation, flexible tubing and gaskets. Melamine Melamine formaldehyde is a thermoset resin. When impregnated in paper it is used as a laminate for table and kitchen unit surfaces. It is also used with fillers for moulding knobs, handles, cups, saucers, toys and light fittings. Nylon Nylon is a thermoplastic used as a synthetic fibre. It has structural similarity to real fibres and is a strong, hard-wearing material making it ideal for use in clothes such as ladies tights and stockings and in raincoats. In addition to its strength and toughness, nylon has a relatively high softening temperature and this makes it ideal for use in various engineering materials like machine gear wheels and bearings as it has a low coefficient of friction. Perspex Perspex is a clear glass-like plastic. It has strong resistance to outdoor environments, heat and ultraviolet radiation and will transmit 90% of daylight. Perspex is also much lighter, tougher and cheaper than glass. Perspex is used as a substitute for glass in aircraft glazing, roof lighting, advertising displays, windows and windscreens, vehicle tail lights, double glazing and protective shields as well as in the lenses of glasses. Plastics Plastics is a common name for a wide range of materials. Thermosetting plastics tend to be hard, rigid plastics which can withstand high temperatures. They are used for making objects which require durability. These include ship's hulls, heavy duty flooring and road surfacing, car tyres, heating pipes, adhesives and car and electrical parts. Thermosoftening plastics tend to be a lot more flexible and mouldable. They include synthetic polymers such as nylon and polyester which can be easily woven. Thermoplastics are also used in packaging, plastic bags, footwear, guttering and piping, to name a few. Polyester Polyester can be produced in two forms; thermoplastics and thermosets. Thermoplastic polyesters have long unlinked polymer chains. They have excellent electrical resistivity, are tough and discolour when subject to ultraviolet radiation. These polymers are used to produce synthetic fibres which are long, strong and can easily be woven into clothes. Thermosetting polyesters have interlinked polymer chains. These polyesters, with glass fibre as a reinforcement, can be created with great tensile strength, similar to that of metals. Reinforced polyesters are used in hulls of boats, car bodies, wheelbarrows, helmets, swimming pools, fishing rods and archery bows because of their strength and toughness. Polythene Polythene is a thermoplastic material. There are two main types: low density (LDPE), which has a branched polymer chain structure and a fairly low tensile strength and high density (HDPE), with linear chains being stronger and stiffer. Both forms have good impermeability to gases and very low absorption rates for water. LDPE is used for bags, squeeze bottles, ballpoint pen tubing, and wire and cable insulation. HDPE is used for piping, toys and household ware. Rubber Rubber is a natural material which is an elastomer that is elastic and resilient. A main property of rubber is that heat builds up slowly within the material. Rubber is essential for tyres as a build up of heat in car or plane tyres could lead to bursting. Because of the resilience of rubber it is used in engine mounts. The good cold weather resistance of rubber makes it a good material to use for bridge bearings. Rubber is used in gloves as it is tough, flexible and water resistant. Rubber is used in bands and as foam due to its elasticity. Ceramics Alumina Alumina is a ceramic that has excellent electrical insulation properties and resistance to hostile environments. Combined with silica, it is used as refractory bricks. Cement Cement, when mixed with water, causes a reaction which results in a silicate structure being formed. Portland cement is used in the manufacture of concrete, a composite material involving cement, gravel and sand. As the tensile strength of concrete is very low, concrete structures are built to exploit the materials impressive compressive strength. Where additional tensile strength is required concrete is usually reinforced by steel. Common uses for concrete include all kinds of building work, railway lines and road building. Clay Clay is used in many ceramic materials with other materials such as silica and feldspar being added. The materials are mixed with water and the product formed. It is then dried and fired to produce the ceramic bonds. Earthenware, such as drain pipes, are fired at a low temperature and have a relatively porous structure. Glass Glass is a non-crystalline solid in which there is no orderly pattern or arrangement of atoms. Glass tends to have low ductility, low thermal expansivity and conductivity but good resistance to chemicals and good electrical insulation properties. Common glass, used in windows, is a form of calcium and sodium silicates. Pyrex glass, a more heat resistant glass has some boron atoms replacing the silicon atoms in the calcium silicate. Optical glass, have different elements incorporated, such as barium or lead. Composites Ceramic Ceramic composites such as alumina with silicon carbide fibres and Pyrex glass with aluminium oxide fibres. Toughness is increased in the composite. Industrial cutting tools are made with alumina reinforced with silicon carbide fibres. Laminates Laminates are made by gluing together sheets of materials together. An example of such a material is plywood with thin layers of wood. Three-ply wood consists of a first layer with fibres in one direction, a second layer with fibres at right angles, and then a final layer with fibres in the same direction as the initial layer; this gives added strength. Metal Metal composites such as alumina and silicon carbide have been used as reinforcement for metals. The composite is stiffer and stronger than the metal alone, but less ductile. Natural Natural composites, such as wood, consist of longitudinal cellulose cells bound together with lignin. The properties along the fibre direction are different from those at right angles to it. Bone is another example of a natural composite. Wood is used extensively in the building trade for beam supports for floors and ceilings. It can also be used to panel walls, for staircases and is used for doors. Often the whole frame of a house is made of wood. Polymer Polymer composites such as epoxy resin with glass fibre and polyester with glass fibre are much stiffer and stronger than the polymer alone and have stiffnesses and strengths as good as some metal alloys.