presentation on ceramic fibers

3. Outline:
 Introduction
 Examples of heat resistance fibres
 Ceramic materials
 Ceramic fibers
 Ceramic raw materials
 Production
 Classification of ceramic fibers
 Properties of ceramic fibers
 Uses of ceramic fibers

4. Introduction:
 Heat resistant fibers are all man made
fibers when we talk about very high
temperatures e.g. above 500 ° C.
 These are all high performance fibers.

5. Examples of Heat Resistance Fibers:
 Nomex
 Ceramic fibers
 Glass fibers
 Carbon fibers

6. Ceramic Materials:
 The word ceramic is derived from the Greek words
kéramos.
 kéramos - ground, clay; kerameoús - made of clay.
 The term covers inorganic non-metallic materials that
have been permanently hardened by firing at a high
temperature.
 The structural ceramic matrix composites (CMC) are used
in reinforcements at temperatures above 1000°C.

8. Ceramic Fibers:
 The definition of ceramic is often restricted to inorganic
non-metallic polycrystalline solids, as opposed to the
noncrystalline glasses.
 The distinction between ceramic and glass has become
difficult now, because ceramics produced from new
precursors or sol – gel routes can be amorphous.

9. Ceramic Raw Materials
Ceramic raw materials (ceramic powders) can be divided into two groups

10. Production:
The ceramic fibers can be produced by either:
 direct process
or
 indirect process.

11. Direct process:
• The pre-treated fibers are spun
through melt spinning.
• The spun fiber is then treated
to form actual ceramic fibers.

12. Transition of pores during treatment

13. Heat treating:
• Organosilicon polymers such as polydimethyl
silane are used.
• The melt spun filament is heated in the air to 190
°C to crosslink the polydimethyl silane molecules
by oxygen
• Then heat treated at 800-1500 °C in nitrogen or
vacuum to form crystalline structure.
• The conversion to ceramic fibers occurs by
pyrolysis above 1200 °C.

14. Indirect method:
 In the indirect process, ceramic fibers are not obtained by spinning process,
but by using some other approach. The process involves two steps
• Step 1: Organic substrate fibers are
soaked with the precursor material or
precursor material is deposited on the
surface.
• Step 2: The inorganic fibre is then
formed by pyrolysis of the organic
template fibre.

16. By Chemical vapor deposition
• Both tungsten and carbon cores are used as
templates for making silicon carbide fibres by
CVD route.
• Various carbon-containing silanes have been
used as reactants.
• In a typical process, with CH3SiCl3 as the
reactant, SiC is deposited on the core as follows:

17. During fabrication of ceramic products significant structural
changes are observed

18. Classification of Ceramic Fibers:
 Chemically these fibers have different compositions and thus
these fibers can be broadly divided into following two
categories:
 Oxide fibres :
Silica fibres, alumina fibres, alumina-silica fibres,
alumina zirconia fibres
 Non-oxide fibres:
Silicon carbide(SiC), silicon carbon nitride, silicon
nitride(SiN)

19. Ceramic fibers are
• hard,
• have low densities (compared to metals)
• high compressive strength
• very good thermal resistance
• strength at higher temperature.
Properties of Ceramic Fibers:

20. Working Temperature :
1,800 °F. for Continuous Use,
2300 °F Maximum
Specific Heat (@2000°F):
0.27 Btu/lb °F
pH Range: 2-12

21. • Due to their notable high temperature
performance, these are useful as reinforcement
in metal and ceramic matrix composites,
where the structures are required to operate at
high temperature.
Uses of Ceramic Fibers:

22. • Ceramic fibers are used in various
applications which include high
temperature insulating material in the
form of mats, blankets and boards,
fire protection.

23. •High temperature insulation seals and gaskets
•Protective blankets, curtains, covers, pads and
wrapping
•Expansion joint fabric, safety clothing