Categories of Materials

 Organics   Metals and Alloys Polymers or “Plastics”  Ceramics  Composites

Organics

 Organics are or were living organisms  Composed of mostly carbon and Hydrogen  Structure depends on the way cells develop, not by human manipulation  Renewable, sustainable  Infinite variety  Genetically alterable

Organics-Wood

 Hardwood- Deciduous, tend to be harder and more expensive  Softwood- Conifers, tend to be softer and cheaper  Plywood- Much stronger and dimensionally stable  Engineered Beams- Construction only  Oriented Strand Board and MDF Dimensionally stable and cheap

Metals and Alloys

    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 soft   Cost; scarcity of element Engineers need certain characteristics that can only be accomplished by a blending of elements Metals are malleable, reflective, and electrically conductive material They are excellent conductors of electricity and heat

Metals

 Possess material properties, including:  high strength and toughness   high electrical conductance high thermal conductance  luster  Examples  aluminum - copper - gold - zinc - iron - lead nickel  silver - thorium - chromium - tin - beryllium

Alloys

   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 Examples  Steel- iron, carbon and impurity elements such as boron copper or silicon    Brass - copper, zinc Stainless Steel - nickel,iron Monel - nickel,copper

Types of Metallics

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

Polymers

 Polymers  Chain-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

Plastics

 Plastics  Human-made polymers  Plastics 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)

Elastomers

 Elastomer  amorphous (shapeless) structure consisting of long coiled-up chains of entangled polymers  can 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: vulcanization  a chemical process used to form strong bonds between adjacent polymers to produce a tough, strong, hard rubber (automobile tires)

Ceramics

 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

Ceramics

(continued)  Categories:  Clay  Refractory  Electrical and Magnetic  Glasses  Cermets

Ceramics

(continued) Clay Products  Inorganic material which is shaped, dried and fired.

Examples: brick, floor and wall tiles, drainage tile, roof tile, sewer pipe, chimney flue, china, and porcelain.

Ceramics

(continued) Refractory Materials  Ceramics 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

Ceramics

(continued) 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 direction  Clay based ceramics for high-voltage insulators

Ceramics

(continued)  Glass Based 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

Composites



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)

Review Major Categories of Materials

 Organics  Metals and Alloys  Polymers  Ceramics  Composites