The database consists of what are known as "advanced ceramics" or "technical ceramics". Modern technical ceramic materials are a diverse group of materials whose properties have been deliberately engineered to produce a wide range of properties, and hence a wide range of applications exist for their use. This breadth and diversity is demonstrated in the following list.

The majority of micrographs in the Digital Library are from the first three categories.

Ceramic materials represent a wide range of materials ranging from single crystal to polycrystalline ceramics to composite ceramics all typified by their brittleness and low strain to failure when compared with metals and plastics. The materials contained in the library are predominantly polycrystalline ceramics fabricated by the consolidation of ceramic powders at elevated temperatures by various processes. In addition there are micrographs of ceramic ceramic composites, which consist of two or more phases deliberately added to the material to promote certain properties. Frequently one of these phases is in the form of a fiber added to improve the toughness of the ceramic.

Listed below is a short explanation of the various methods used to fabricate the ceramic materials contained in this library of micrographs.

Sintering is a process in which the a pressed powder compact is heated to elevated temperature to cause the compact to shrink in size and increase its density close to its theoretical density.

Hot Pressing involves the application of a uniaxial pressure at elevated temperature to the powder compact.

In Hot Isostatic Pressing a high pressure gas is used to apply pressure to the powder compact which is contained in an impervious glass envelope.

Reaction Bonding is a process in which two or more powders or a powder and a gas react together to form the desired ceramic.

Chemical Vapor Deposition utilizes the chemical reaction of one or more gases at elevated temperature to form a thin layer or coating of the ceramic material.

Gas Pressure Sintering employs a medium pressure gas atmosphere in conjunction with elevated temperature.

Fusion Casting the powder compact is heated to a very high temperature so that the ceramic melts and can be cast to shape on a cooling block or die.

Two infiltration methods are used to prepare some of the composite materials in the database.
	In Chemical Vapor Infiltration a gas penetrates a porous ceramic and reacts to fill the open porosity with another ceramic material.
	Melt Infiltration a liquid ceramic fills the open porosity in the host ceramic. The database can be searched to show only materials fabricated by one of these techniques.

TESTING OF CERAMICS

The library contains many images with associated property data. Frequently the micrographs are taken from the specimen used in a specified test, such as a tensile test or a creep test. There are many standardized laboratory tests used to evaluate the performance of ceramics. Test selection is based upon the desired application of a paticular ceramic, the temperature and environment the material will witness, and the functionality of the ceramic. For example, a ceramic material that might be used as cutting tool would be expected to possess high hardness, fracture toughness and creep resistance. Thus candidate ceramic cutting tool materials would be subjected to several laboratory tests to determine these properties. The resulting test data would then be used to determine if any of the candidate materials exhibit the desired properties to warrant further evaluation in actual metal cutting trials.

Many of the tests are ASTM ones and references to the details of these tests such as mechanical testing of ceramics can be found on their website at

http://www.astm.org/cgi-bin/SoftCart.exe/index.shtml?E+mystore