January 1, 2010

Ceramics Class

بِسم الله الرَحْمنِ الرَحِيْم


This word "Ceramic" was derived from Greek word "Keramikos", which is derived from "Keramon" or "Keramos", meaning "Argil"[1] or pottery.

Another definition is 
Any of various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing a nonmetallic mineral, such as clay, at a high temperature.[2]

But, a ceramic has traditionally been defined as “an inorganic, nonmetallic solid that is prepared from powdered materials, is fabricated into products through the application of heat, and displays such characteristic properties as hardness, strength, low electrical conductivity, and brittleness." 


Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (e.g., a glass). Because most common ceramics are crystalline, the definition of ceramic is often restricted to inorganic crystalline materials, as opposed to the non-crystalline glasses. 

They are most frequently oxide,nitrides, and carbides. For example, some of the common ceramic materials include aluminum oxide (or alumina, Al2O3), silicon dioxide (or silica, SiO2), silicon carbide (SiC), silicon nitride (Si3N4).


Ceramic materials can be subdivided into traditional and advanced ceramics. Traditional ceramics are composed of clay minerals (i.e., porcelain), and other natural occuring materials. Clay-base materials such as brick, tile, sanitary ware, dinnerware, clay pipe, and electrical porcelain. Common-usage glass, cement, abrasives, and refractories are also important classes of traditional ceramics.

Advanced ceramics are tailored to have premium properties through application of advanced materials science and technology to control composition and internal structure. Examples of advanced ceramic materials are silicon nitride, silicon carbide, toughened zirconia, zirconia-toughened alumina, aluminum nitride, lead magnesium niobate, lead lanthanum zirconate titanate, silicon-carbide-whisker-reinforced alumina, carbon-fiber-reinforced glass ceramic, silicon-carbide-fiber-reinforced silicon carbide, and high-temperature superconductors. 

Properties : 

Ceramic materials are relatively stiff and strong in compression comparable to those of the metals and weak in shearing an tension. In addition, ceramics are typically very hard. On the other hand, they are extremely brittle (lack ductility), and are highly susceptible to fracture. These materials are typically insulative to the passage of heat and electricity (i.e., have low electrical conductivities, ), and are more resistant to high temperatures and harsh environments than metals and polymers.  With regard to optical characteristics, ceramics may be transparent, translucent, or opaque and some of the oxide ceramics (e.g., Fe3O4) exhibit magnetic behavior.

Atomic Bonding:

The atoms in ceramic materials are held together by a chemical bond  Briefly though, the two most common chemical bonds for ceramic materials are covalent and ionic. Covalent and ionic bonds are much stronger than in metallic bonds and, generally speaking, this is why ceramics are brittle and metals are ductile.



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