Abstract: An alumina fiber structure of a flat shape composed of alumina fibers having an alumina content of at least 65% by weight, the majority of said fibers being oriented substantially in parallel with the flat surfaces of the structure, and a number of fiber strands composed of the same alumina fibers extending inwardly from the flat surfaces of the structure, said structure having a thickness of from 4.8 mm to less than 10 mm, a density of from 0.07 to 0.3 g/cm.sup.3, a tensile strength of at least 0.5 kg/cm.sup.2 and a peeling strength of at least 0.5 kg/m.

Abstract: Alumina fiber structures prepared by (i) preparing precursor fibers by spinning a viscous spinning solution containing compounds of metals including aluminum and an organic polymer compound in which the proportion of alumina in the total metals in the solution is at least 65% by weight of alumina when all metals are calculated as their oxides; (ii) laying the precursor fibers into a mat; (iii) applying a lubricant which is a solution of higher fatty acid ester in a hydrocarbon solvent to the fibers either before or after forming the mat; (iv) needling the lubricated mat; and (v) burning the obtained structure to convert the precursor fibers to alumina fibers, possess high tensile strengths and high peel strengths.

Abstract: An alumina fiber structure of a flat shape composed of alumina fibers having an alumina content of at least 65% by weight, the majority of said fibers being oriented substantially in parallel with the flat surfaces of the structure, and a number of fiber strands composed of the same alumina fibers extending inwardly from the flat surfaces of the structure, said structure having a thickness of at least 10 mm, a density of from 0.07 to 0.3 g/cm.sup.3, a tensile strength of at least 0.5 kg/cm.sup.2 and a peeling strength of at least 0.5 kg/m.