Ceramics-Abrasives


 * ABRASIVES **
 * Abrasive** - a substance that is used for the removal of material by scratching or rubbing.

Abrasives are classified into two groups: //natural// and //manufactured//.

Types of //Natural Abrasives//:

Flint is an extremely hard form of silica. Flint is used for making coated abrasive for use in woodworking and leather trades. Flint is used to make sandpaper.
 * Flint**

Corundum contains 98% alumina and small amounts of silica and iron. It is the second-hardest natural material found in the Earth.
 * Corundum**

Emery is an impure form of corundum. It is used for coated abrasives and grinding wheels.
 * Emery**

The most common garnets for abrasive purposes are almandite, andradite, and shodolite. It is used as a coated abrasive in woodworking trades.
 * Garnet**

Sandstone is made of a mineral cement which contains calcite, quartz, clay, or limonite. It is used for grindstones.
 * Sandstone**

Pumice is lava or volcanic rock. Has low density which allows it to float on water. It is used for rubbing and polishing metal, glass, and fine finishes on furniture.
 * Pumice**

Tripoli is a mild abrasive of high silica content. It is used for scouring and cleansing straps, rubbing down compounds, and for finishes.
 * Tripoli**

Rottenstone is a soft rock formed from sandstone. It contains 80-90% of silica along with aluminum. It is used for rubbing compounds.
 * Rottenstone**

Diamond abrasives are used for heavy-duty grinding, drills, and fro dressing points to true grinding wheels. Diamonds are the hardest natural material found in the Earth. Synthetic diamonds have been developed by transforming graphite into diamond through heat and pressure. //(1)//
 * Diamond Abrasives**

Types of //Manufactured Abrasives//:

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 * Silicon Carbide-**
 * Uses- fixed and moving turbine components, suction box covers, seals, bearings, ball valve parts, hot gas flow liners, heat exchangers, semiconductor process equipment
 * Properties- low density, high strength, low thermal expansion, high thermal conductivity, high hardness, high elastic modulus, excellent thermal shock resistance, superior chemical inertness //(3)//


 * Boron Carbide-**
 * Uses- used as an abrasive in polishing and lapping applications, and also as a loose abrasive in cutting applications such as water jet cutting, it can also be used for dressing diamond to
 * Properties- extreme hardness, difficult to sinter to high relative densities without the use of sintering aids, good chemical resistance, good nuclear properties, low density //(2)//

//(1)// Wright, John R. __Introduction to Materials & Processes__. Ed. John Anderson. Albany, New York: Delmar Publishers, 1996.
 * References**

//(2)// "Boron Carbide (B4C) - Properties and Information about Boron Carbide." __AZoM" - The A to Z of Materials and AZojomo - The "AZo Journal of Materials Online"__ 03 May 2009 .

//(3)// "Materials Silicon Carbide (SiC) Properties." __Accuratus Fine Technical Ceramics and Glasses__. 03 May 2009 <http://www.accuratus.com/silicar.html>.