Introduction

In this lecture we are going see some more advanced fibres. Further, we will see their key features, applications and fabrication processes.

Alumina Fibre

• These are ceramics fabricated by spinning a slurry mix of alumina particles and additives to form a yarn which is then subjected to controlled heating.
• Fibers retain strength at high temperature.
• It also shows good electrical insulation at high temperatures.
• It has good wear resistance and high hardness.
• The upper continuous use temperature is about 1700  .
• Fibers of glass, carbon and alumina are supplied in the form of tows (also called rovings or strands) consisting of many individual continuous fiber filaments.
• Du Pont has developed a commercial grade alumina fibre, known as Alumina FP (polycrystalline alumina) fibre. Alumina FP fibres are compatible with both metal and resin matrices. These fibres have a very high melting point of 2100 . They can withstand temperatures up to 1000 without any loss of strength and stiffness properties at this elevated temperature. They exhibit high compressive strengths, when they are set in a matrix.
• The Alumina whiskers are available and they exhibit excellent properties. Alumina whiskers can have the tensile strength of 20700 MPa and the tensile modulus of 427 GPa.

What are the applications of Alumina fibres?

• The Alumina has a unique combination of low thermal expansion, high thermal conductivity and high compressive strength. The combination of these properties gives good thermal shock resistance. These properties make Alumina suitable for applications in furnace use as crucibles, tubes and thermocouple sheaths.
• The good wear resistance and high hardness properties are harnessed in making the components such as ball valves, piston pumps and deep drawing tools.