Classification of solid materials
Solid materials have been classified according to their atomic structure and chemical composition into three major groups:
- Metallic materials
- Polymeric materials
- Ceramic materials
1, Metallic materials: Metallic materials are commonly combination of two or more metallic elements, in some cases non metals like C, N, are also combined to metallic materials to obtain required material properties and the reason why these are combined is because metallic elements are very soft in their pure condition and does not has any practical applications.
Metals have crystalline structure having atoms arranged in orderly manner. Metals have very good conducting source of electricity and heat and also has very lustrous appearance. Metallic materials are very hard and strong but yet are deformable too under some conditions.
Metallic materials are further classified into two categories i.e. Ferrous and Non-ferrous material,
Ferrous materials are those materials which has relatively high percentage of iron element or iron as a major constituent. By adding carbon into this other forms of metals are formed i.e. Wrought iron, Steel, carbon steel, alloy steel and cast iron. Other than carbon other metallic elements like chromium are also added to obtain desired metallic property.
Non-ferrous materials are the ones which does not has iron as a major constituent or has very small percentage of iron element. Examples of non-ferrous metals are Aluminium, Zinc, Copper and lead etc. Non-ferrous materials provide wide range of properties like aluminium is very light weight and soft material it can easy be cast forged and machined also Copper is very good conductor of electricity and is used in the form of wires for the electrification purpose .
2, Polymeric materials: Polymeric materials is basically referred to plastics and rubbers and are made up of combinations of long chains of monomers. This combination of chain is called molecule and the number of links in the chains could be millions.Carbon plays role of major links having 4 valence electrons which enables it to make bond with 4 elements and the links between carbon to carbon c-c is the majority while bond of other elements like nitrogen oxygen hydrogen is minority.
Furthermore they have very large molecular structures. Most polymeric materials are non-crystalline but some are consists of mixture of crystalline and non crystalline regions. Most polymers are poor conductor of electricity while some of them are very good insulators and find application in the electrical insulators.
Polymers can be grouped into three major groups i.e. Thermoplastics , Thermosettings and Elastomers.
Thermoplastics are the materials which can be softened by application of head and re hardened again and again considering the temperature not to be so high to decompose the material. They have linear or branched molecular structures.
Thermosetting are the materials which has very complex molecular structures due to which they are very rigid and they can not be softened by application of heat.
Elastomers are materials having properties between of the thermoset and thermoplastic. They have lightly cross linked structure under which molecules are free to move. Due to this elastomers are very elastic in behaviour.
2, Ceramics: Ceramics are compounds of metallic and non metallic elements. They are mostly oxides , nitrides and carbides. The wide range of materials that falls within this classification includes ceramics that are composed of clay minerals cement and glass. ceramic materials can be crystalline or non-crystalline. These materials are insulator of electricity and are brittle, hard and strong in compression but weak in shearing and torsion.
Ceramics are divided into two categories i.e. Crystalline and non crystalline ceramics.
Crystalline ceramics are the ones which can not be made by application of heat and deformation , they can only be made in two ways, one is making it of desired shape by reaction in situ and second one is by forming ceramic powders in desired shape followed by sintering to form solid body.
Non crystalline ceramics are the ones which can be deformed by application of heat. for example glass can be melted and casted into any shape by application of heat.