| 摘要 |
PROBLEM TO BE SOLVED: To obtain a heat insulating material excellent in mechanical and thermal characteristics such as strength in spite of low density by mixing mullite fibers with acidic colloidal silica in water, adding silica fibers and a boron compd., dehydrating and compacting the resultant slurry and carrying out drying and firing. SOLUTION: The mullite fibers (A) have a rhombic system, 2-5μm average fiber diameter and 0.2-10mm average fiber length and the molar ratio of SiO2 :Al2 O3 is 2:3. The acidic colloidal silica (B) has a low Na content so as not to deteriorate the heat resistance of stock fibers. The silica fibers (C) are high purity silica fibers having >=95wt.% SiO2 content, 0.3-3μm average fiber diameter and 1-5mm average fiber length. The boron compd. (D) is, e.g. boron oxide. The amt. of the component B is 10-30wt.% of the total amt. of the components A, C. The amt. of the component A is 75-95wt.% of the total amt. of the components A, C. The amt. of the component D is 3-5wt.% (expressed in terms of B2 O3 ) of the total amt. of the components A, C. |
