forging new generations of engineers. organics metals and alloys polymers ceramics composites

Forging new generations of engineers

• Organics• Metals and

Alloys• Polymers• Ceramics• Composites

Organics are or were living organismsComposed of mostly carbon and HydrogenStructure depends on the way cells developed

not by human manipulationRenewable, sustainable Infinite varietyGenetically alterable

Metals are pure elements which comprise about three-fourths of the periodic table

Few are used in their pure form because of: Hardness; too hard or too softCost; scarcity of elementEngineers need certain characteristics that can

only be accomplished by a blending of basic elements

Metallic materials include alloys, which are combinations of metals and other elements

Possess material properties, including:high strength and toughnesshigh electrical conductancehigh thermal conductanceluster

Examplesaluminum - copper - gold - zinc - iron - lead -

nickelsilver - thorium - chromium - tin - beryllium

Consist of materials composed of two or more elements, at least one being a metal

This combination of elements gives the material a combination of properties from each element

ExamplesSteel- iron, carbon and impurity elements

such as boron copper or silicon Brass - copper, zincStainless Steel - nickel,ironMonel - nickel,copper

Ferrous Metallics - iron and alloys which contain at least 50% iron (e.g. wrought iron, cast iron, steel, stainless steel)

Nonferrous Metallics - Metallic elements other than iron (e.g. copper, lead, tin, zinc, titanium, beryllium, nickel)

Powdered (Sintered) Metals (ferrous or non-ferrous)Sometimes called sintered metal. A process of

producing small (powdered) particles which are compacted in a die and then “sintered” (applying heat below the melting point of the main component)

Examples: trigger on gun, gears, bearings, carbide tool inserts

PolymersChain-like molecule made of many (poly)

smaller molecular units (mono”mers”)Chaining (polymerization) is responsible for

the formation of natural fibers, wood, lignin, rubber, skin, bone and the tissues of animals, humans and insects

PlasticsHuman-made polymersPlastics are workable or moldable

Thermosetting plastics are formable once (e.g. epoxy, phonelic (Bakelite), polyurethane)

Thermoplastics can be heated repeatedly and formed into new shapes (e.g. polyethylene, nylon,

Plexiglas)

Elastomeramorphous (shapeless) structure consisting of long

coiled-up chains of entangled polymerscan be stretched at room temperature to at least

twice its original length and return to its original shape after the force has been removed

Process to strengthen an elastomer: vulcanizationa chemical process used to form strong bonds

between adjacent polymers to produce a tough, strong, hard rubber (automobile tires)

Crystalline compounds combining metallic and non metallic elements

The absence of free electrons make ceramics poor electrical conductors.

Because of the strength of the bonding, ceramics have high melting temperatures

Categories: Clay

Refractory

Electrical and Magnetic

Glasses

Cermets

Clay ProductsInorganic material which is shaped,

dried and fired.Examples: brick, floor and wall tiles, drainage

tile, roof tile, sewer pipe, chimney flue, china, and porcelain.

Refractory MaterialsCeramics designed to provide

acceptable mechanical or chemical properties while at high temperatures.

Most are based on stable oxides such as carbides, nitrides, and borides.

An example of a refractory is the machinable all-silica insulating tiles on the U.S. space shuttle

Electrical and Magnetic Applications Ceramics are used as resistors and heating

elements for furnaces (silicon carbide)Semiconductor properties:

Thermistors- as they heat-up allow current to flow.

Rectifiers- allow current to flow in one directionClay based ceramics for high-voltage insulators

GlassBased on silica with additives that alter the

structure or reduce the melting point, optimize optical properties, thermal stability and resistance to thermal shock

Cermets

Combinations of metals and ceramics(oxides, nitrides, or carbides) bonded together in the same way powdered metallurgy parts are made.

Examples: crucibles, jet engine nozzles

Laminar or Layer Composites - alternate layers of materials bonded together. (e.g. plywood, safety glass, Formica, bimetallic strips)

Particulate Composites - discrete particles of one material surrounded by a matrix of another material. (e.g. concrete, asphalt, powdered metals and ceramics)

Fiber-Reinforced Composites - composed of continuous or discontinuous fibers embedded in a matrix of another material. (e.g. Kevlar, rayon, steel reinforced tires, fiberglass, graphite-epoxy)

• Organics• Metals and Alloys• Polymers• Ceramics• Composites

Major Categories of Materials