A powder is disclosed having a coarse fraction representing more than 60% and less than 85% of the powder, as a weight percentage on the basis of the oxides, and that is constituted of particles having a size greater than or equal to 50 m, referred to as coarse particles, the powder comprising at least 5% of coated grains having a size greater than or equal to 50 m, as a weight percentage on the basis of the oxides of the powder, and a fine fraction, forming the balance to 100% as a weight percentage on the basis of the oxides, constituted of particles having a size of less than 50 m, referred to as matrix particles. The powder can be applied in combustion chambers in which the temperature may reach 1400 C.

A molten refractory product having the following average chemical composition, in wt % on the basis of oxides and for a total of 100%: Al.sub.2O.sub.3: balance to 100%; Fe.sub.2O.sub.3: 0.6%-5.0% and/or TiO.sub.2: 1.5%-10.0%; Fe.sub.2O.sub.3+TiO.sub.210.0%; Na.sub.2O+K.sub.2O: 1.0%-8.0%; SiO.sub.2: 0.2%-2.0%; CaO+BaO+SrO: 0.5%; Other oxide species: 1.5%. Also, a glass-melting furnace and the use of the refractory product in the glass-melting furnace.

A molten refractory product having the following average chemical composition, in wt % on the basis of oxides and for a total of 100%: Al.sub.2O.sub.3: balance to 100%; Fe.sub.2O.sub.3: 0.6%-5.0% and/or TiO.sub.2: 1.5%-10.0%; Fe.sub.2O.sub.3+TiO.sub.210.0%; Na.sub.2O+K.sub.2O: 1.0%-8.0%; SiO.sub.2: 0.2%-2.0%; CaO+BaO+SrO: 0.5%; Other oxide species: 1.5%. Also, a glass-melting furnace and the use of the refractory product in the glass-melting furnace.

The present invention relates to temperature-treated polycrystalline porous Al.sub.2O.sub.3 bodies comprising an amount of aluminum oxide of more than 97% by weight, an amount of other oxide alloying components of a total of less than 3% by weight, a macroporosity of between 5 and 30% by volume, wherein the Al.sub.2O.sub.3 bodies are composed of a plurality of Al.sub.2O.sub.3 primary crystals comprising a crystallite size of between 20 and 100 m.

The present invention relates to temperature-treated polycrystalline porous Al.sub.2O.sub.3 bodies comprising an amount of aluminum oxide of more than 97% by weight, an amount of other oxide alloying components of a total of less than 3% by weight, a macroporosity of between 5 and 30% by volume, wherein the Al.sub.2O.sub.3 bodies are composed of a plurality of Al.sub.2O.sub.3 primary crystals comprising a crystallite size of between 20 and 100 m.

The present invention relates to temperature-treated polycrystalline porous Al.sub.2O.sub.3 bodies comprising an amount of aluminum oxide of more than 97% by weight, an amount of other oxide alloying components of a total of less than 3% by weight, a macroporosity of between 5 and 30% by volume, wherein the Al.sub.2O.sub.3 bodies are composed of a plurality of Al.sub.2O.sub.3 primary crystals comprising a crystallite size of between 20 and 100 m.

A ceramic oxide body is disclosed. The ceramic oxide body may include fused cast aluminum oxide powder, fine aluminum oxide powder and titanium oxide powder.

A ceramic oxide body is disclosed. The ceramic oxide body may include fused cast aluminum oxide powder, fine aluminum oxide powder and titanium oxide powder.

A castable refractory composition may include from 5% to 95% by weight of alumina, aluminosilicate, or mixtures thereof; from 0.5% to 1.5% by weight alkaline earth metal oxide and/or hydroxide, and 0.1% to 5% by weight of silica having a surface area of at least about 10 m.sup.2/g. The refractory composition may include no more than 0.5% by weight of cementitious binder. The refractory composition may release less than 25 cm.sup.3 of hydrogen gas per kilogram of castable refractory composition upon addition of water. The refractory compositions may set on addition of water.

A castable refractory composition may include from 5% to 95% by weight of alumina, aluminosilicate, or mixtures thereof; from 0.5% to 1.5% by weight alkaline earth metal oxide and/or hydroxide, and 0.1% to 5% by weight of silica having a surface area of at least about 10 m.sup.2/g. The refractory composition may include no more than 0.5% by weight of cementitious binder. The refractory composition may release less than 25 cm.sup.3 of hydrogen gas per kilogram of castable refractory composition upon addition of water. The refractory compositions may set on addition of water.