An Introduction to Materials Technology Foundations of Technology Unit 3.10

Objectives  To familiarize students with the connection between materials science and engineering materials and how researchers have consistently improved materials that, in turn, enhance the performance of the technologies that use them.

What are materials?  The tangible substances that go into the makeup of a physical object. One of the basic resources used in a technological system.

Basic Concepts  The physical properties of the material are generally a basic reason for selecting the material for the needed product performance.  The performance of a product frequently requires various behaviors and thus types of properties.  It is frequently found that a compromise among the needed properties must be made to be consistent with the processing selected and the structural state desired.  Most of the useful properties are related to the structural state of the material.

Descriptions of Materials  Metals:  Materials are normally combinations of “metallic elements”.  These elements, when combined, usually have electrons that are non-localized and have generic types of properties.  Metals are usually good conductors of heat and electricity.  They are quite strong, but malleable, and tend to have a lustrous look when polished.

Descriptions of Materials  Ceramics:  Ceramics are generally compounds between metallic and nonmetallic elements.  Typically, they are insulating and resistant to high temperatures and harsh environments.  Plastics:  Plastics (or polymers) are generally organic compounds based upon carbon and hydrogen.  They have very large molecular structures. Usually they have low density and are unstable at high temperatures

Descriptions of Materials  Semiconductors:  have electrical properties intermediate between metallic conductors and ceramic insulators.  The electrical properties are strongly dependant upon small amounts of impurities.  Composites:  consist of more than one material type. Examples include plywood and fiberglass.

Properties  Mechanical:  tensile strength, fracture toughness, fatigue strength, creep, hardness  Electrical:  conductivity or resistivity, ionic conductivity, semi-conductivity  Magnetic:  magnetic susceptibility, Curie Temperature, Neel Temperature

Properties Continued  Optical and Dielectric:  polarization, capacitance, refractive index, absorption  Thermal:  coefficient of thermal expansion, heat capacity, thermal conductivity  Environmental-related:  corrosion behavior, wear behavior