Alpha alumina is one of the most important ceramic materials with properties and applications having been thoroughly explored. Fused Cast Alpha Alumina block comprises about 99% alumina (90% alpha alumina and 4% beta Al2O3), 0.4% SiO2 and 0.9% Na2O.
Alumina (Al2O3) is an aluminium compound with many crystalline forms or polymorphs. Alumina exists in many forms, α, χ, η, δ, κ, θ, γ, ρ. Alpha alumina or corundum is the only thermodynamically stable form amongst the different polymorphs. Alpha alumina stable at very high temperature and this property is also used as refractory and thermal barrier.
Alumina is characterized with high compression strength, high hardness, good resistance to abrasion, high resistance to chemical attack, high thermal conductivity, good resistance to thermal shock, and high degree of refractoriness.
Its applications are widespread, and include spark plugs, tap washers, pump seals, electronic substrates, grinding media, abrasion resistant tiles, cutting tools, bioceramics, (hip-joints), body armour, laboratory ware and wear parts for the textile and paper industries. It is also used in the manufacture of monolithic and brick refractories. It is also used mixed with other materials such as flake graphite for even more severe applications.
Fused Cast Alpha Alumina block is relatively resistant to molten glass corrosive action, though not at the level of Baddeleyite. Most importantly, it does not develop a passivation layer like fused cast AZS refractory. It dissolves slowly in the glass through a concentration gradient at the contact surface. Temperature and glass velocity tangential to the surface determine the corrosion speed.
Fused cast alpha alumina block is an ideal product for the lower temperature zones of the glass melting furnaces due to its high density, superior corrosion resistance and low blister potential. It is also an ideal material for Metallurgical Titanium Furnace because the superior thermal stability.