These modules are intended to introduce both teacher and student to the world of Materials Science and technology. There are eight modules including this one. The other seven modules cover ceramics, metals, polymers, semiconductors, composites, concrete and energy. This module is intended to give a brief introduction to Materials Science and technology as well as an idea of what each module covers.
A brief definition, description of properties, uses and production techniques are given in this section. The "coverage" section follows this section and talks about specific issues covered in each module.
Metals are metallically bonded compounds made from most of the elements on the periodic table. Metals can be either monatomic such as copper, or an alloy such as steel. Metals are ductile, malleable, electrically conductive and thermally conductive. All of these properties come from the way metallic atoms bond together. Metals are used for structures, electrical wires, locks, coins, and many more items. Metals can easily be bent, machined, cast or extruded into shape. The widespread use of Metals is in large part due to this ease of manufacturing.
Ceramics are defined as inorganic, non-metallic materials; ceramics are either covalently or ionically bonded (or a mixture of the two). Ceramics are brittle, strong and non-conducting materials. Ceramics are typically compounds consisting of metals covalently bonded to oxygen, nitrogen or carbon. Ceramics are used for high temperature applications, abrasives, transparent windows and pottery. Ceramic pieces are generally made through extrusion, slip casting, or compression molding.
Polymer comes from the two Greek words "poly", which means many, and "meros", which means unit. A polymer may have one type of repeating unit of many different types of repeating units. Polymers are usually carbon based. Polyethylene is a long chain of carbons bonded together in a straight line. Hydrogen atoms are bonded to the rest of the sites. ABA is a copolymer with different repeating units. Polymers are light-weight, ductile, usually non-conductive and melt at relatively low temperatures. Polymers are used for a large variety of items. Trash bags, pot holders, wire insulation, computer chips, packing materials, car doors, and many other items are all made of polymers. Polymers can be made into products by injection molding, extrusion, pressing, blow molding, stamping or machining.
Semiconductors are materials that are doped to make them partially conductive through holes (p-type) or electrons (n-type). Most semiconductors are silicon based and doped with boron (p-type) or phosphorous (n-type). Useful electrical properties are found when p-type and n-type semiconductors are combined together. Diodes, transistors, solar cells and opto-electrical devices are all devices that can be made out of semiconductors. The ability to put a million such devices on a surface less than cm^2 allows for the today's computer chips to be so powerful. Processing of semiconductors is a complicated multi-step process.
A composite material is made up of a matrix and a reinforcement phase. Composites take advantage of directional properties of the reinforcement phase and gluing properties of the matrix. The reinforcement phase may be any material in fiber, platelet, or aggregate form. The matrix phase must be able to flow around the reinforcement and later hardened. Metals, ceramics, cement, and polymers are all regularly used for man-made composites. Composites are very difficult to manufacture (except for concrete). New techniques has made it easier to make sporting equipment, space shuttle parts, and car parts out of composites.
Concrete is a composite made up of sand and rocks in a cement paste. Concretes have very good compressive properties but poor tensile properties unless reinforced with steel wires. Concrete has a separate module apart from composites because of its widespread use in our nation's infrastructure and construction industry. Sidewalks, bridges, roads, foundations and support beams are all made out of concrete. Concrete is made into the final product by mixing the aggregate, cement, and water together and pouring into a mold. The chemical process of hydration causes the mixture to chemically bond and become hard.
Energy is the ability to do work. Potential, kinetic, chemical, heat and nuclear are all forms of energy. Energy can be changed from one of these forms to other forms. Energy can neither be created nor destroyed. All material manufacturing procedures rely on energy transfer and storage. This is why energy is included as a module.
This section gives a brief description of what each module covers.
Structure of Metals:
What is This Stuff?: