Glass and Ceramics

Glass and Ceramics hold the promise to change our lives in the way that Plastics have done. A great deal of money has been put into research with some results, but still short of the dream.

Ceramics are composed of inorganic nonmetallic materials such as oxides, nitrides, borides, and carbides. Ceramics can be broken down into two groups, the "traditional" ceramics (which includes glass, pottery, brick, and refractories) and "advanced" ceramics, which are the newer materials developed since the 1960's.

Glass
Glass is generally considers to be a subset of ceramics, however since its use is so wide spread it warrants sharing the heading. Glass is used in a wide variety of applications, from the obvious sheet glass used in windows, and containers, to more specialized glasses used for dishware (home and laboratory).

Even in the solid form, its structure is more like a "liquid" than a solid. It is actually a super cooled liquid somewhat similar to "Taffy". ASTM defines the material as an inorganic product of fusion that has been cooled to a rigid condition without crystallizing. It is an amorphous material (As glass is cooled it become less plastic in its behavior and more brittle. It, like taffy is also "rate" sensitive. If you bend a piece of glass that has been heated to a temperature where it still maintains its form, it can be bent and shaped. but if you bend it too quickly, it may break.

Most glasses are made up of Silicates. Soda Lime Glass accounts for approximately 90% of all glass tonnage produced. The glass is relatively easy to melt from basic raw materials and is used for containers, flat glass, and lighting products. Borosilicate glasses have lower coefficients of expansion and good resistance to chemical attack. They are used on ovenware and sealed beam headlights. A third group a glasses are the aluminosilicate glasses, these glasses contain alumina in an alkali silicate glass. These aluminosilicate glasses have higher temperature properties and can be used in stove top applications.

Glass-Ceramics
Glass-Ceramics contain both

Ceramics
Ceramic Materials (other than "glass") are most often formed by producing parts from powder, and sintering them. The proper mix of powder elements is mixed with a binder and then fired at high temperatures.