Alumina-silica (Al2O3–SiO2) fibers, frequentlyreferred to as ceramic fibers, are formed bysubjecting a molten stream to a fiberizing force.Such force may be developed by high-velocitygas jets or rotors or intricate combinations ofthese. The molten stream is produced by meltinghigh-purity Al2O3 and SiO2, plus suitablefluxing agents, and then pouring this meltthrough an orifice. The jet or rotor atomizes themolten stream and attenuates the small particlesinto fine fibers as supercooling occurs. Ceramic fibers were originally developed forapplication in insulating jet engines. Now, thisis only one of numerous uses for this material.It can be found in aircraft and missile applicationswhere a high-temperature insulatingmedium is necessary to withstand the searingheat developed by rockets and supersonic aircraft.Employed as a thermal-balance and pressure-distribution material, ceramic fiber in theform of paper has made possible the efficientbrazing of metallic honeycomb-sandwichstructures.Successful trials have been conducted inaluminum processing where this versatile productin paper or molded form has been used totransport molten metal with very little heat loss.Such fibrous bodies are particularly useful inthese applications because they are not readilywet by molten aluminum. Industrial furnace manufacturers utilizelightweight ceramic fiber insulation betweenfirebrick and the furnace shell. It is also usedfor “hot topping,” heating element cushions,and as expansion joint packing to reduce heatloss and maintain uniform furnace temperatures.Use of this new fiber as combustion chamberliners in oil-fired home heating units hasmaterially improved heat-transfer efficiencies.The low heat capacity and light weight, comparedto previously used firebrick, improve furnaceperformance and offer both customer andmanufacturer many benefits.
