Thursday, December 25, 2008

what are ceramic material and its uses ?

When we just hear the term Ceramic, the term ceramic comes to mind as dish, porcelain figures, and the like. A typical dictionary definition of ceramic is “ the art of work of making pottery, like, porcelain, etc..

Original definition of ceramic: compound composed of metallic and non metallic elements with strong ion, ionic or covalent bond between atoms.

The most significant property is common to ceramic as well as to cemented carbide, glasses, and carbon-graphite is brittleness. Most of ceramic materials are brittle: concrete blocks , ceramic tile, carbide tools, ceramic wear pants, glasses, pottery, computer chips, bricks.

Technical Ceramics can also be classified into three distinct material :

* Oxides: Alumina, zirconia

* Non-oxides: Carbides, borides, nitrides, silicides

* Composites: Particulate reinforced, combinations of oxides and non-oxides.

Each one of these classes can develop unique material properties. Below is some details about categories.

Oxide ceramics: Oxidation resistant, chemically inert, electrically insulating, generally low thermal conductivity, slightly complex manufacturing and low cost for alumina, more complex manufacturing and higher cost for zirconia.

Non – oxide ceramics: Low oxidation resistance, extreme hardness, chemically inert, high thermal conductivity, and electrically conducting, difficult energy dependent manufacturing and high cost.

Ceramic – based composites: Toughness, low and high oxidation resistance (type related), variable thermal and electrical conductivity, complex manufacturing processes, high cost.

The most used material of any type of structure application are ceramic type of material, concrete, to glasses.

In the early 1990s’,many material research laboratories in industry had programmes trying to develop application for which ceramics will be cost effective and provide a service advantage over other materials, only few ceramics emerged as contenders for industrial applications; Aluminium oxides, silicon carbides, also cemeted carbides and in some cases the machinable ceramic(glass-bonded micas) are candidates.

Ceramic Industry manufacture of useful and ornamental articles from clay by shaping and hardening it in high temperature. The industry is basically a development of indigenous pottery works. Broadly, ceramics denote the manufacture of any product made from a non-metallic mineral hardened at high temperatures. Industrial ceramics comprise all industrially used solid materials that are neither metallic nor organic. Major ceramic products include glass, earthenware, porcelain, and white-ware, porcelain enamels, brick tiles and terracotta, refractories, cement, lime and gypsum and certain abrasives.

In a Industry ceramic materials play a very large roll, from walls to electrical ware, ceramic is used world wide, industrial uses of ceramic are;

Bricks (mostly aluminium silicates), used for construction, building walls as partitions as protections and many more used in a ceramic brick.

Earthenware, which is often made from clay, quartz and feldspar.

Ferrite (Fe3O4), which is ferrimagnetic and is used in the core of electrical transformers and magnetic core memory.

Zirconia, which in pure form undergoes many phase changes between room temperature and practical sintering temperatures, can be chemically "stabilized" in several different forms. Its high oxygen ion conductivity recommends it for use in fuel cells. In another variant, metastable structures can impart transformation toughening for mechanical applications; most ceramic knife blades are made of this material.

Clay products of all kinds can be used for interior finishing, ceramic wall tile in various sizes and shapes is used in kitchens, bathrooms, wash rooms, labouratires, for a feature wall, or as a dadu or wainstoria with another material covering the upper part of the wall.

In the early 1980s, Toyota researched production of an adiabatic ceramic engine which can run at a temperature of over 6000 °F (3300 °C). Ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater fuel efficiency. Fuel efficiency of the engine is also higher at high temperature. In a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts.

Recently, there have been advances in ceramics which include bio-ceramics, such as dental implants and synthetic bones. Hydroxyapatite, the natural mineral component of bone, has been made synthetically from a number of biological and chemical sources and can be formed into ceramic materials. Orthopedic implants made from these materials bond readily to bone and other tissues in the body without rejection or inflammatory reactions. Because of this, they are of great interest for gene delivery and tissue engineering scaffolds. Most Hydroxyapatite ceramics are very porous and lack mechanical strength and are used to coat metal orthopedic devices to aid in forming a bond to bone or as bone fillers. They are also used as fillers for orthopedic plastic screws to aid in reducing the inflammation and increase absorption of these plastic materials. Work is being done to make strong-fully dense nano crystalline Hydroxapatite ceramic materials for orthopedic weight bearing devices, replacing foreign metal and plastic orthopedic materials with a synthetic natural bone mineral. Ultimately these ceramic materials may be used as bone replacements or with the incorporation of protein collagens, synthetic bones.

Until the mid 1980s’ the electroic industy multichip substance needs were normally met by ceramic based hybrid intergrated circuits (HICs) HICs were the first widely used mem technology, whose biggest strength lays in its extensive passive component capability.

In electronic circuits, last packing processes step is package sealing. Ceramic packages use two basic process: glass and solder sealing. Welding is used in very high reliability applications typically with metals packages. There are various ceramic packages construction and sealing techniques. Glasses may also be used to attach the package lid to the seal ring solder attachment of metal hide to a moralized seal ring is widely used in military applications.

In paint industry ceramic as a surface coating offer high coating offer high hardness, resistance to abrasion and corrosion protection as well as high temperature properties considerably superior to those of there materials. Their main disadvantages are their liability to crack under conditions of mechanical and thermal shock and their cost.


-Engineering material, 5th edition, Kenneth G. budinski.
-Material of construction,2nd edition, R.C smith.
-Ceramic Fabrication Technology; Roy Rice
-Building services materials hand book, E & F.N spon
-Materail scince & technology,vol16,R.W cahn,p.haasan, e.j kraner.

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