Fabrication and processing of ceramics

Fabrication and processing of glass and ceramics

The ceramics fabrication technique generally consist of three different forms

1. Glass forming
2. Particulate forming process
3. Cementation

Glass forming process

Glass forming process mainly consist of four steps:

• Blowing
• Pressuring
• Drawing
• Fiber forming

1. Glass is produced by heating raw materials to high temperature above which melting occurs. Most commercial glass is of silicon soda lime verity. Silicon is usually supplied as quartz sand whereas \(Na_2O\) and CaO are added as sodium carbonate and lime state (\(CaCO_3\))(calcium carbonate).
2. The most essential property of glass must be free from porosity and impurities. Thus result from small gas bubbles and foreign substances.
3. Pressing :Pressing is used in the fabrication of relatively thick walled piece such as plates and dishes. The glass piece is form by pressure application in graphite coated cast-iron mold having desired shaped.

• Blowing:

Some glass blowing is done by hand. Specifically, for art object. The process has been completely automated for production of glass jar, bottle and light bulbs.

• Drawing

Drawing is used to form long glass piece such as sheet, rod, tubing, fibre which have constant cross-section.

• Fiber forming:

Glass of different refractive index is mixed with to form core and cladding surface. This is used for the transmission of communication signal. The schematic diagram for the process of making glass making glass sheet is shown in figure.

Some ceramic material include clay products and white wares:

• Characteristics of clay

Clay material has two important roles in ceramics:

1. When water is added they become very plastic and condition is solid to be hydroplasticity, this property is very important in forming process.
2. Clay fuses or melts over a wide range of temperature. The fusion temperature range depends upon composition of clay.

• Clay are alumino silicates i.e. compose of \(Al_2o_3\) and \(SiO_2\) and chemically consist of bound water.

1. The clay product has wide range of physical characteristics, chemical composition and structure. These products include barium, calcium sodium, potassium, iron and some organic matter. Crystal structure clay minerals are relatively compact and complicated.
2. In the composition of clay product known clay minerals includes flint finally ground quartz and minerals such as salts of potassium, sodium, calcium ions are mixed. For example: a typical porcelain might contain 50% clay, 25% quartz and 25% feldspar. Fieldspar are some of the more common fluxing agents they are group of alumino silicate materials that contained \(K^+,Na^+, Ca++\).

Fabrication technique

The two common shaping technique are utilized for forming clay based composition:-

• Hydroplastic forming
• Slip casting

Hydroplastic forming

In this process clay minerals is mixed with water in such a way that it becomes plastic and pliable materials without cracking the most common hydroplastic forming is extrusion in which a stiff plastic ceramics mass is forced through die orifice. Brick, pipe, ceramic block, tiles are commonly fabricated by this technique.

Slip casting:

A slip is suspension of clay or other non-plastic materials in water when it is poured into a porous mold commonly made of plaster of paris. Water from the slip is absorbed into the mold leaving behind a solid layer of mold. This process is continuing until a solid layer of mold wall is formed. And it becomes solid layer of mold wall is formed. And it becomes solid casting.

The solid mold is dries and shrinks to form mold wall. The clay product mostly free defects and excess liquid to remove this, defect and liquid drying and firing process done.

References:

Callister, W.D and D.G Rethwisch. Material Science and Engineering. 2nd. New Delhi: Wiley India, 2014.

Lindsay, S.M. Introduction of Nanoscience . New York : Oxford University Press, 2010.

Patton, W.J. Materials in industry . New Delhi : Prentice hall of India, 1975.

Poole, C.P. and F.J. Owens. Introduction To Nanotechnology. New Delhi: Wiley India , 2006.

Raghavan, V. Material Science and Engineering. 4th . New Delhi: Pretence-Hall of India, 2003.

Tiley, R.J.D. Understanding solids: The science of Materials. Engalnd : John wiley & Sons , 2004.