Patent ID: 8911825

Claim:
A process for producing a fiber-reinforced heat-resistant sound-absorbing material, the process comprising the steps of: (a) forming a fiber preform made of silicon carbide short fibers having a length of 50 mm or less and a heat resistance of at least 1000° C.; (b) preparing a sol-gel solution containing a heat resistant compound having heat resistance of at least 1000° C.; (c) impregnating the fiber preform with the sol-gel solution, then drying and calcining the fiber preform; and (d) crystallizing the fiber preform after impregnation, drying and calcination, wherein the silicon carbide fibers contain a metal element which is selected form the class consisting of Group I, III and IV metal atoms of the periodic table and in which a temperature at which a free energy change in the carbon reduction reaction of the oxide of the metal element becomes a negative value is higher than a temperature at which a free energy change in the carbon reduction reaction of silicon oxide becomes a negative value; and wherein the silicon carbide fibers have an oxygen content falling within a range of from 2 to 13 wt. %, wherein the resulting fiber-reinforced heat-resistant sound-absorbing material has a porosity of at least 95%, and a noise absorption of at least 95 % in a frequency band of 1000 to 4000 Hz.