Ceramic Fibers

CERAMIC FIBERS

They are known as refractory ceramic fibers. ST90

Ceramic fibers comprise a wide range of amorphous or crystalline synthetic mineral fibers characterized by their refractory properties (i.e., stability at high temperatures).

They are typically made of alumina, silica, and other metal oxides or, less commonly, of nonoxide materials such as silicon carbide.

Most ceramic fibers a are compounds of alumina and silica in an approximate 50/50 mixture.

The monoxide ceramics, such as alumina and zirconia, are composed of at least 80% of one oxide; they generally contain 90% or more of the base oxide, and specially products may contain virtually 100%.

Non-oxide ceramic fibers, such as silicon carbide, silicon silicon nitride, and boron nitride, also have been produced. Because there are several types of ceramic fibers, such fibers exhibit a range of chemical and physical properties.

Most ceramic fibers are white to cream in color and tend to be polycrystallines or polycrystalline metal oxides.

Characteristics and advantages of ceramic fibers

 (i) Low thermal conductivity: This makes the use of much thinner blankets possible for furnace lining.

 (ii) Weight: It is a light weight refractory insulation. This reduces the manpower engaged at site for handling and installation.

(iii) Thermal mass: Heat storage is directly related to mass. Ceramic fibre is a low thermal mass material. Considerable energy can be saved specially in case furnaces are operating a cyclic pattern.

(iv)Thermal shock: Ceramic fibres are resistant to thermal shock. Rapid heating and cooling does not affect ceramic fibres.

(v) Mechanical shock: It is flexible and resilient in most product forms.

(vi) Chemical attack: It has excellent resistance to chemical attack and is unaffected by oil, steam, water. However, it is affected by concentrated hydrofluoric acid, phosphoric acid and concentrated alkalies.

(vii) Thermal expansion: Thermal expansion is nil. Large furnaces can be built without any expansion joint. However, there may be some shrinkage.

(viii) Acoustic properties: Ceramic fibres provide good acoustical properties in the frequency range of 300 - 3000 cycles/seconds, over many of the conventional products used for acoustic purpose.

(ix) Health and safety: Ceramic fibres are inorganic and completely non-combustible, hence safe to handle and work.

Uses and Applications

• Ceramic fibers are used as insulation materials, due to their ability to withstand high temperatures. They are used primarily for lining furnaces and kilns.

• The products are in the form of blankets, boards, felts, bulk bas fibers, vacuum-formed or cast shapes, paper and textiles.

• High-temperature resistant ceramic blankets and boards are used in ship building as insulation to prevent the spread of fires.

• Ceramic textile products, such as youns and fabrics, are used extensively for heat-resistant clothing, flame curtains for furnace openings.

• Ceramic fibers are used as thermocoupling and electrical insulation, gasket and wrapping insulation, coverings for induction-heating furnace coils.

• In automotive industry, papers and felts containing bna bi ceramic fibers are used in catalytic converters, heat shields, air bags, brake pads, clutch facings, and shoulder-belt controls.

• Commercial and domestic appliances using ceramic-fiber insulation include pizza-oven and deep-fryer heat shields toasters, self-cleaning ovens, wood stoves, homeheating furnaces, gas hot water heaters, and simulated fire place logs.

The refractory fibres have found their applications in

(a) Boiler and reformer lining.

(b) High temperature pipe insulation.

(c) Furnace door seals and lining.

(d) Stack lining - low flue gas velocity.

(e) Repair of refractory furnace lining and roofs. beleorist

(f) Kiln insulation as packing material.

(g)  Packing material in burner openings.

(f) Packing material in glass tanks.