Abstract: To provide an alumina-based fibrous mass having a high areal pressure and is usable as a holding material for an exhaust gas cleaners and a production process thereof; the alumina-based fibrous mass has a chemical composition containing an Al2O3 in an amount of 70% or more and less than 90% and having a total pore volume of 0.0055 mL/g or less.

Abstract: There is provided an alumina fiber capable of fixing a honeycomb carrier while maintaining elasticity for a long period of time even in a severe usage environment, and an alumina fiber aggregate formed of the fiber. Problems in a gripping material of an automotive honeycomb carrier are solved by applying an alumina fiber containing from 70 to 98% by mass of alumina and from 2 to 30% by mass of silica, having an average fiber diameter of from 3.0 to 8.0 ?m, a ratio of fibers having a fiber diameter exceeding 10 ?m being 5% or less in terms of the number of fibers and a size of a mullite crystallite contained in each fiber of from 10 to 1500 ?, and by forming an alumina fiber aggregate by using the fibers.

Abstract: To provide an alumina-based fibrous mass having a high areal pressure and is usable as a holding material for an exhaust gas cleaners and a production process thereof; the alumina-based fibrous mass has a chemical composition containing an Al2O3 in an amount of 70% or more and less than 90% and having a total pore volume of 0.0055 mL/g or less.

Abstract: A process for producing the alumina fiber aggregate which, when examined by the electron microscope method, gives a frequency distribution regarding number of fibers, wherein the number of fibers having a fiber length of 50-200 ?m is 70% or more (including 100%), the number of fibers having a fiber length smaller than 50 ?m is 30% or less (including 0), the number of fibers of 50-100 ?m is 30-50%, the number of fibers longer than 100 ?m but not longer than 200 ?m is 30-50%, and the number of fibers longer than 200 ?m is 20% or less (including 0). The process including the steps of grinding cottony alumina-based fibers comprising 70-100% by mass of Al2O3 and 0-30% by mass of SiO2 while applying a pressure of 0.1-20 MPa thereto and then classifying the ground fibers.

Abstract: A process for producing the alumina fiber aggregate which, when examined by the electron microscope method, gives a frequency distribution regarding number of fibers, wherein the number of fibers having a fiber length of 50-200 ?m is 70% or more (including 100%), the number of fibers having a fiber length smaller than 50 ?m is 30% or less (including 0), the number of fibers of 50-100 ?m is 30-50%, the number of fibers longer than 100 ?m but not longer than 200 ?m is 30-50%, and the number of fibers longer than 200 ?m is 20% or less (including 0). The process including the steps of grinding cottony alumina-based fibers comprising 70-100% by mass of Al2O3 and 0-30% by mass of SiO2 while applying a pressure of 0.1-20 MPa thereto and then classifying the ground fibers.

Abstract: An object of the invention is to provide an alumina fiber aggregate which, when used as a filler in various materials such as, e.g., resins, coating materials, metals, and ceramics, enables the mixtures to have reduced viscosity and thereby heightens the productivity of products containing alumina fibers, and which enables cured thermosetting resins to have a sufficiently heightened thermal conductivity. This alumina fiber aggregate, when examined by the electron microscope method, gives a frequency distribution regarding number of fibers, wherein the number of fibers having a fiber length of 50-200 ?m is 70% or more (including 100%), the number of fibers having a fiber length smaller than 50 ?m is 30% or less (including 0), the number of fibers of 50-100 ?m is 30-50%, the number of fibers longer than 100 ?m but not longer than 200 ?m is 30-50%, and the number of fibers longer than 200 ?m is 20% or less (including 0). The fibrous mass comprises 70-100% by mass of Al2O3 and 0-30% by mass of SiO2.

Abstract: An object of the invention is to provide an alumina fiber aggregate which, when used as a filler in various materials such as, e.g., resins, coating materials, metals, and ceramics, enables the mixtures to have reduced viscosity and thereby heightens the productivity of products containing alumina fibers, and which enables cured thermosetting resins to have a sufficiently heightened thermal conductivity. This alumina fiber aggregate, when examined by the electron microscope method, gives a frequency distribution regarding number of fibers, wherein the number of fibers having a fiber length of 50-200 ?m is 70% or more (including 100%), the number of fibers having a fiber length smaller than 50 ?m is 30% or less (including 0), the number of fibers of 50-100 ?m is 30-50%, the number of fibers longer than 100 ?m but not longer than 200 ?m is 30-50%, and the number of fibers longer than 200 ?m is 20% or less (including 0). The fibrous mass comprises 70-100% by mass of Al2O3 and 0-30% by mass of SiO2.