APPLICATIONS OF SILICON CARBIDES

2.1. APPLICATIONS OF SILICON CARBIDES

There has been an increasing demand for high performance materials, which can withstand se- vere conditions such as abrasion, high temperature, pressure and atmosphere in various applications as follows :

1. High Temperature Heat Engines,

2. Nuclear Fusion Reactors,

3. Chemical Processing Industry, and

4. Aeronautical and Space Industries. In order to meet these demands, it requires the introduction of expensive and ‘scarce metallic

alloys’ which also frequently need additional ‘completed cooling arrangements’. Hence, the possibility of using silicon carbide can be explored for important applications in various industries as mentioned above [1-3].

2.1.1. Important Properties

Silicon carbide seems to have the potential to satisfy the requirements in most of the applications as ‘high temperature structural material’ for the following important properties :

(a) Superior Oxidation Resistance, (b) Superior Creep Resistance, (c) High Hardness, (d) Good Mechanical Strength,

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(e) Very High Young’s Modulus, (f) Good Corrosion & Erosion Resistance, and (g) Relatively Low Weight. It is important to mention here that the raw materials of silicon carbide are relatively inexpensive,

and can be made in complex shapes, which my be engineered by conventional fabrication processes, such as dry pressing, extrusion and injection moulding. Therefore, the final products are cost-competi- tive besides offering the advantages of superior technical performance over the other materials.

2.1.2. Ceramic Engines

The application of silicon carbide in ‘ceramic engine’ offers a higher efficiency of the engine, which could be operated at a higher operating temperature, thereby ensuring the complete combustion of the fuel. This ensures that the full energy obtainable from a given fuel is harnessed in the automobile combustion process and at the same time reducing the environmental pollution. Moreover, the material has only one-third of the density of the ‘super-alloys’ giving it an additional advantage, when used in designing and application in an automobile system. In ceramic heat engines, there are many facets in the use of the silicon carbide material, which has the potential for applications as follows :

(a) Turbo-Charger Rotor, (b) Piston Liner, (c) Valve Trim Components in Gasoline Engines, such as :

1. Rocker Arm Pads,

2. Push Rod Tips,

3. Pre-Combustion Caps,

4. Wrist Pins,

5. Lifters Roller Followers.

2.1.3. Other Engineering Applications

The silicon carbides also find many other applications in diverse areas as follows :

A. Stationary and Rotating Components in ‘Automotive Gas Engines’, such as :

1. Turbine Wheel Combustion Chamber,

2. Rotor of Various Dimensions, and

3. Nose Cones.

B. Inherent Hardness, Chemical Inertness and a High Abrasion Resistance make silicon carbides commercially applicable in ‘Chemical Processing Industry’, such as :

1. Seals and Valves,

2. Nozzle for Sand Blasters

3. Lens Modes, and

4. Wear Plates for Spray Drying and Wear Dies

C. The other Applications for these ‘Wear and Erosion Resistant’ silicon carbides include :

1. Aircraft Journal Bearing,

2. Thrust Bearing,

SILICON CARBIDE

3. Ball Bearings,

4. Oil Patch Plungers,

5. Pump Impellars,

6. Pump Components,

7. Various Fixtures,

8. Mould Billets, and

9. Extrusion Dies.

D. Due to high Thermal-Shock Resistance and Creep Resistance Characteristics, Silicon Car- bides are also used as Nozzles in many other applications, such as :

1. Heat Exchanger Tubes,

2. Diffusion Furnace Components, and

3. Furnace Rollers.

E. The silicon carbides alredy find applications as ‘Heating Elements’ because of its Self-Heat- ing and Self-Emitting Glow Characteristics.

F. The silicon carbides also hold promise for its use as “Electronic Substrates’ for Semiconductor Industry. By having a ‘Thermal Conductivity Value’ several times higher than that of alumina, and silicon carbide as a ‘substrate’ can handle the ‘Heat Dissipation’ task of the ‘Electronic Chips’ and also protect the ‘Chips Wall’.

The development of highly dense silicon carbide requires a basic understanding of the mecha- nism of sintering by the addition of various additives or dopants, and their correlation with the micro- structure, to eventually appreciate the inherent mechanism for the development of superior thermo- mechanical properties. With so many important properties with diverse applications, as mentioned above, the study of sintering and fracture mechanical behaviour (see chapter - 4) of silicon carbide assumes a great importance and a considerable significance.