The History And Use Of Ceramic Material Engineering Essay
Ceramics which means potter's earth or clay is a material made from naturally occurring clay. Scientifically it may be considered as a compound comprising both metallic and non metallic elements. Diamond and SiC are examples of manufactured ceramics. Ceramic may also be defined as inorganic or non metallic materials processed or used at high temperatures. In ancient times ceramics were pottery which were made from clay itself or mixed with other materials however new ceramic materials have been developed for use in ceramic engineering, such as semiconductors.
There are traditional ceramics and advanced ceramics. Materials such as china clay, Talc, Feldspar, Silica and Dolomite were some of common materials used in traditional ceramics. They were used because of their properties such as dry strength, plasticity and shrinkage. Sel3ction of materials, size of particles and particle shape have great impact on final products. In advanced ceramics industry, the purity of ceramic powder is a great problem while in traditional it is not. Some of the traditional ceramics products are: pottery, tableware, sanitary ware, tiles, blocks and electrical porcelain. Advanced ceramics on the other hand, are mainly used for electrical, electronic, optical and magnetic applications. In this sector, techniques of production must be used to make sure that ceramic powders possess sufficient purity. (2)
Types of ceramic products
Ceramic are of four different categories. Structural ceramic comprises tiles, bricks and pipes. White wares ceramic which include objects like decorative, sanitary ware, table ware and wall tiles. The examples of white ware ceramics are stone ware, porcelain, bone china and earthen ware. Refractories ceramic like glass and steel building crucibles, gas fire radiant and kiln linings. Technical or fine ceramics products which include tiles applied in the space shuttle program, ballistic fortification, bio-medical implants, missile nose cones, nuclear fuel uranium oxide pellets and jet engine turbine. (1)
Properties of Ceramics
They show plastic deformations.
They are semi conductors
They are generally hard
They are crystalline or amorphous
Some ceramics become super conductors under extremely low temperatures
They are usually covalently bonded or ionic substances
Most of them are transitional metal oxides
Ceramics are classified into crystalline or non-crystalline. Non-crystalline are made from melts and are known as glass ceramics. They are not common since they require a lot of processing as compared with crystalline ceramics. (1)
Uses of Ceramics and Why They Are Used
They are used in making knives
Though they are brittle, their blades are more durable.
Their knives are sharper than steel knives.
Alumina and boron carbide are used as "Small Arms Protective Inserts"
This is because of the low weight of the material
Ceramic balls can be used to replace steel in ball bearings
Due to their hardness they have a longer lifetime
Ceramic engines can be used in laboratories
They have high fuel efficiency and do not require cooling.
High-tech ceramic is used in watch making for producing watch cases
The material is valued by watchmakers for its light weight, scratch-resistance, durability and smooth touch.
Hydroxyapatite ceramics used to coat metal orthopedic devices by forming a bond as bone fillers.
They are very porous and lack mechanical strength.
Plastic means capable of being shaped or molded. Its malleability allows when its being produced allows it to be pressed and make many shapes. Used in the manufacture of industrial products, plastic materials are of synthetic or semi synthetic organic solids. Plastic materials are polymers of high molecular mass and contains other substances which improve in turn reduce cost or increase performance. However they are of two types, that is, thermoplastics and thermosetting polymers. When heated, Thermoplastics don't undergo chemical change in their composition. Polyethylene, polystyrene, polyvinyl chloride and polytetrafluoroethylene are main examples which can be molded again and again. Thermosets on the other hand, stay solid when they solidify since they melt and take shape once.
Properties of Plastics
Tough, rigid, shatter-resistant, softens if heated
Soda, water, juice, and cooking oil bottles
High Density Polyethylene
Semi-rigid, tough, flexible
Milk and water jugs, bleach bottles
Strong, semi-rigid, glossy
Detergent bottles, shampoo bottles, shrink wrap, pipes
Low Density Polyethylene
Flexible, not crinkly, moisture-proof
Garbage bags, sandwich bags, 6-pack rings
Low Density Polyethylene
Flexible, not crinkly, moisture-proof
Yogurt cups, margarine tubs, screw-on lids/caps
Often brittle, sometimes glossy, often has strong chemical reactions
Styrofoam, egg cartons, packing pellets, take-out containers
Manufacture of Plastics
They are manufactured in two ways: blow molding and blown film. In blow molding process, plastic parts are formed by melting and extruding plastics into a hollow tube called parison. It is then taken by closing it into a cooled metal mold. The plastic will take the shape of a mold when air is blown into the parison. Once it has cooled, the mold is opened and the plastic part removed. Milk bottles and household chemical containers are examples of blow molding products. In blown film, in blown film, plastic melt is extruded through an annular die, usually vertically, to form a thin walled tube. Air is then introduced from a hole in the centre of the die by blowing up the tube as a balloon. Mounted on the top of the die, an air ring blows onto the hot film to cool it. The tube of film then continues upwards, continually cooling, until it passes through rolls where it is flattened and then winded in to rolls. The film is used as is or in a subsequent process to convert into bags that have many different consumer and industrial applications. Plastics have been the fastest growing basic material because they are: versatile, lightweight, tough, energy saving, low cost, durable and recyclable. (3)
Uses of plastics
High Density Polyethylene (HDPE)
Used for making food products containers
It has a good moisture barrier, its compatible with acids, it is an excellent choice for silk-screening when flame treated
Low Density Polyethylene (LDPE)
Usedmainly for squeezing applications.
It is less chemically resistant compared with HDPE
Used in packaging, textiles for example ropes, thermal underwear and carpets, stationery, plastic parts and reusable containers of various types and also in manufacture of laboratory equipment.
It is stable at high temperatures, it has excellent chemical resistance
Usedto make plastic jars.
It creates a rigid walled container of excellent clarity
Polyvinyl Chloride (PVC)
Used to insulate electrical wires, manufacture of pipes and in clothing industries
It has extremely good resistance to oils and also a good drop impact resistance
Polyethylene Terephthalate (PET)
Used to make soda bottles and water bottles
Hasexcellent clarity and very good alcohol and essential oil barrier properties, has a high degree of impact resistance.
Metals are chemical elements that form cations and ionic bonds when combined with non metals. They are both good conductors of heat and electricity. It can be an element, compound or an alloy which is characterized by high electrical conductivity. Delocalized ions which are responsible for the conductivity surround the ions. They form a metallic bonding which in turn form a solid which is held by electrostatic interactions between the ions and the electron cloud.
When two metals are mixed together they form alloys. Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modifies the properties of pure metals to produce desirable characteristics. The aim of making alloys is generally to make them less brittle, harder, resistant to corrosion, or have a more desirable color and luster
Categories of metals
Metals may be categorized in different forms which include; base metal, precious metal, Nobel metal and ferrous metal. Base metal is a metal that oxidizes or corrodes easily and reacts with dilute acids to produce hydrogen. Ferrous metal are metals that contain iron and may be magnetic. Examples are wrought iron and alloys such as steel. Noble metals are that which do not corrode or undergo oxidation. Noble metals are very rare and tend to be precious. Examples include tantalum, platinum and gold. Precious metals on the other hand are also rare and have chemical element of high economic value. These metals are considerably less reactive compared with other metals. In contrast to tradition where they were viewed as currency, precious metals are currently used as investment and industrial commodities. (4)
Properties of common metals
used for water pipes and electrical wires
It is shiny, non-toxic (not poisonous), low density (light for its size) and does not corrode (rust).
used for bridges, manhole covers and gates
Good electrical conductor, a good heat conductor and does not corrode (rust).
used for aircraft and overhead electricity cables
It is a hard, strong, and cheap and it corrodes (rusts).
Extraction of Metals
Metals are removed from the earth, by means of mining. They are removed in terms of ores which result to very useful elements. Mineral sources are divided into subsurface mines and surface mines which are extracted by use of heavy machines. Chemical or electrolytic reductions are the methods used to extract metal from the ore.ore are converted to raw materials by use of pyrometallurgy. (4)
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