Basics about metals, ceramics, and polymers

Everyone in the group should read this page about all the different classes of materials. After everyone has read, pick who will become the expert in each field. Before the group splits up to become an expert in their field, they should first look at the rest of the basic information about corrosion, processing, conductivity, and forces. After they are finished looking at all those pages, each student should go to their material page (metals, etc.), which are located at top of the Materials Selection Page. Remember you are trying to learn about this class of material so that you can figure out if it would be the best class to choose from for a material that will suit your product redesign. The page will be a bunch of World Wide Web links that will take you to find out about the materials class.

This type of materials has characteristics like, high electrical and thermal conductivity, the ability to be deformed or cut into new shapes without breaking, and high mechanical strength. Since metals must be reduced from chemical compounds, they tend to be somewhat more costly than non-metallic materials, and they are often vulnerable to corrosion damage as the metals react with their environment to re-form those compounds. They tend to be shiny and malleable. Metals have these characteristics because they have nonlocalized electrons.

Ceramics are generally compounds between metallic and nonmetallic elements and include such compounds as oxides, nitrides, and carbides. Typically they are insulating (not electrical or thermally conductive) and resistant to high temperatures and harsh environments (corrosion resistant). They usually have lower electrical and thermal conductivity, higher stiffness, good resistance to corrosive environments, and lower fracture toughness than metals. With the exception of glasses, ceramics usually cannot be reshaped easily. To shape a ceramic, a mixture of ceramic powders, water, and binder materials is molded into the desired dimensions to form a temporary shape. These temporary shapes called "green bodies" are then dried to remove water and heated to allow the binder materials to oxidize, leaving the ceramic powder particles to bond to each other during the high temperature baking.

Plastics (or polymers) are generally organic compounds based upon carbon and hydrogen. They are very large molecular structures. Usually they are low density and are not stable at high temperatures. They can be readily formed into complex shapes. Their strength, stiffness, and melting temperatures are generally much lower than those of metals and ceramics. Their light weight, low cost, and ease of forming make them the preferred material for many engineering applications.
A combination of two or more materials differing in form or composition. The differnet parts still have the same features they originally did, that is, they do not dissolve or merge completely into one another, however, their properties are enhanced by eachother. Normally, the components can be physically identified and exhibit an interface (boundary) between one another. Fiberglass, a combination of glass and a polymer, is an example. Concrete and plywood are other familiar composites. Many new combinations include ceramic fibers in metal or polymer matrix.


Basics about metals, ceramics, polymers,and composites
corrosion and environment




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Click here for the Merriam-Webster dictionary if you have trouble with some of the words on this page.