The majority of raw materials used by the ceramic industry are the oxides of metals. The three metals which have been the mainstays of the industry for many years are clay, flint, and feldspar. These are the major materials contained in what is sometimes referred to in the industry as "classical ceramic bodies."
Clay
Clays are hydrated aluminosilicates and are the end-product of the weathering of feldspathic rock. The most important clay mineral is Kaolinite which has the composition AL2O3 - 2SiO2 - 2H2O. Clay is the material that gives a ceramic composition the plasticity which facilitates the fabrication of the material into the desired form prior to heat-treating.
Flint
Flint is a form of silicon dioxide (SiO2) usually produced from quartzite, sand or rock. It is used in a finely pulverized form as a filler to give the clay and final product the desired properties.
Feldspar
Feldspar is a broad, generic name applied to a group of alkali-aluminosilicates. For example, feldspars in which the alkali is potassium (K2O - Al2O3 - 6SiO2) are called "potash feldspars," and those containing sodium (Na2O - Al2O3 - 6SiO2) are called "soda feldspars." Most feldspars, however, are combinations of these two types. Feldspar is used and known as a "flux" in the ceramic industry. The flux is the material which starts to melt at the lowest temperature during the heat-treating process, thereby acting as the cementing element which gives the ceramic body its strength.
A great many other naturally-occurring minerals and some synthetically produced chemicals are used as raw materials by the ceramic industry. A few of the more important ones, along with their chemical formulas, are now presented:
| Naturally
Occurring
(Chemical Composition)
Clay (Al2O3 - 2SiO2 - 2H2O) Feldspar (K2O or Na2O - Al2O3 - 6SiO2) Flint (SiO2) Whiting (CaCO3) Magnesite (MgCO3) Talc (3MgO - 4Si2 - H2O) Nepheline Syenite (K2O - 3Na2O - 4Al2O3 - 9SiO2 + Feldspar) Zircon (ZrO2 - SiO2) Borax (Na2O - 2B2O3 - 10H2O) Pyrophyllite (Al2O3 - 4SiO2 - H2O) Spodumene (Li2O3 - Al2O3 - 6SiO2) Beryl (BeO - Al2O3 - 6SiO2) |
Artifically
Produced
(Chemical Composition)
Alumina (Al2O3) Litharge (PbO) Zinc Oxide (ZnO) Tin Oxide (SnO2) Barium Titanate (BaO TiO2) Lead Zirconate (PbO ZrO2) Iron Oxide (Fe2O3) Silicone Carbide (SiC) Titanium Carbide (TiC) Boron Nitride (BN) Cobalt Oxide (CoO)
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