JPH0212896B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a porous refractory made of ceramic fiber used for high-temperature heat-resistant heat insulating materials, high-temperature fluid filters, catalyst carriers, metal reinforcement, and the like. [Prior Art] Fiber porous refractories made by molding and sintering Al ₂ O ₃ -B ₂ O ₃ -SiO ₂ fibers are known and used by the National Aeronautics and Space Administration in space shuttles and the like. These fibers can fuse the contact areas between the fibers by heating without using a binder, making it possible to form a high-strength fibrous porous refractory. However, this fiber is very expensive and cannot be used as a general industrial material that requires economy. For general industrial use, Al ₂ O ₃ -SiO ₂ fibers, Al ₂ O ₃ fibers, and SiO ₂ fibers are dispersed in water with an inorganic binder such as silica sol or alumina sol, vacuum formed, dried, and fired. The contact area between fibers is SiO ₂ ,
A fibrous porous refractory made by fusing Al ₂ O ₃ is used. However, this material lacks strength, and its bending strength (according to JIS9503-19695.7 bending strength; the same applies hereinafter) is 2 to 4 kg/cm ² , and does not have sufficient strength to withstand handling. If phosphoric acid, water glass, or the like other than silica sol or alumina sol is used as a binder, the fibers will deteriorate and the heat resistance and strength will decrease. A fibrous porous refractory has also been proposed in which Al ₂ O ₃ fibers, SiO ₂ fibers, and boron oxide are dispersed in water, vacuum formed, dried and fired, and the contact areas between the fibers are fused with boron oxide. ing. In this case, boron oxide (B ₂ O ₃ ) has deliquescent properties and reacts with water to form boron and dissolves in water (solubility: 4 g/100 ml at 20°C), so it remains in water during vacuum forming, resulting in loss of fiber. During drying and firing, substances attached to B ₂ O ₃ undergo metaboric acid and tetraboric acid.
It also sublimates and dissipates during the process of changing into . This varies slightly depending on the temperature of the water used as a dispersion medium and the conditions during drying and firing, and the amount of adhesion to the fibers is not constant, so it exhibits sufficient strength to match the amount of B ₂ O ₃ added. In some cases, the strength is not the same as when no additives are used, and in some cases, the strength is only intermediate between the two, resulting in a problem that the strength of the obtained fibrous porous refractory is not constant. [Problems to be Solved by the Invention] The present invention provides a fiber porous refractory made of one or both of Al ₂ O ₃ -SiO ₂ fibers and SiO ₂ fibers and having stable strength, and this refractory. The purpose is to provide an economically stable method of manufacturing. [Means for Solving the Problems] In order to achieve the above object, the present invention provides Al ₂ O ₃ −
A fibrous porous refractory in which the contact portion of the fibers of a porous molded product made of one or both of SiO ₂ fibers and SiO ₂ fibers is fused with nitrogen- and boron-containing glass;
and Al ₂ O ₃ -SiO ₂ fibers, one or both of SiO ₂ fibers, and by heating without dissolving in water, Al, Si, B, O,
Boron nitride or nitrogen compound and boron compound powder forming a glass network structure consisting of N or Si, B, O, and N are dispersed in water, vacuum formed, and the formed product is fired and sintered to produce a fibrous porous refractory. It's about getting things. Nitrogen compounds that can be used in the present invention include AlN,
_Si3N4 , Si- _Al -O _- N, _Si2N2O , _{Ca3N2 ,}
Examples include Li ₃ N and Mg ₃ N ₂ . In addition, boron compounds include B ₄ C, TiB ₂ , CrB ₂ , TaB ₂ ,
MnB ₂ , MoB ₂ , VB ₂ , HfB ₂ , AlB ₂ , MgB ₂ ,
Examples include ZrB ₂ , W ₂ B ₅ , Mo ₂ B ₅ and the like, and any nitrogen compound or boron compound may be used as long as it does not deteriorate the material fiber. If the particle size of boron nitride or the above compound powder is too small, when drying a vacuum-formed product, the particles will migrate to the surface with water and stick to the drying plate, making it difficult to remove and often impairing marketability. If the particle size is too large, it will shift to one side during vacuum forming and the sintered state will be uneven.
Use particles having a particle size distribution in which 80% by weight or more has a particle size of 1 to 44 μm. Boron compound powder contains B ₂ O ₃ per 100 parts by weight of fiber.
Use 2 to 7 parts by weight. If the amount is less than 2 parts by weight, sinterability will be insufficient, and if it is used in an amount exceeding 7 parts by weight, the strength will no longer improve after sintering, and unreacted boron compounds will remain in the sintered body. As a result, the strength of the product decreases when reheated. When using a mixture of nitrogen compound powder and boron compound powder instead of BN, it is preferable to use them so that the number of B atoms and N atoms is 1:1. The fibers have a length of 30 to 1 mm, with most of the fibers having a length of 5 to 7 mm, and about 10 parts by weight or less per 100 parts by weight of water are dispersed in water, and boron nitride powder or nitrogen compound powder and boron compound powder are added. Then, add an organic flocculant, perform vacuum forming, dry, and heat at 1250 to 1400℃.
The material is fired for 1 to 1.5 hours and sintered to create a fibrous porous refractory. [Operation] When the boron nitride powder or nitrogen compound powder and boron compound powder dispersed together with the fibers in water are dried after vacuum forming, they are mainly deposited at the contact areas between the fibers due to capillary action. When these dry deposited powders are heated to high temperatures, Al ₂ O ₃ in the fibers,
Reacts with SiO ₂ to form nitrogen-containing aluminoborosilicate glass or nitrogen-containing borosilicate glass, forming a glass network structure of Al, Si, B, O, N or Si, B, O, N, and forming contact areas of fibers. Tightly connect. Since these compounds remain in the molded body during firing until they decompose or sublimate at high temperatures, they can be used to bond fibers more efficiently than when B ₂ O ₃ is used. [Example] Example 1 10 parts by weight or less of Al ₂ O ₃ -SiO ₂ fiber (trade name Kao Wool manufactured by the applicant) and B ₂ O ₃ in 100 parts by weight of water.
Disperse 1 to 15 parts by weight of BN in water,
After adding an organic coagulant, vacuum forming was performed, drying, and sintering by firing at 1370°C for 1 hour. Bending strength test pieces were prepared from the sintered bodies and their strengths were compared. The results are shown in Table 1.

[Table] Example 2 Also, instead of BN, B ₄ C and Si ₃ N ₄ are used as B atoms and N
A sintered body was prepared and tested in the same manner as in Example 1 except that the ratio of atoms was approximately 1:1, and the results were as shown in Table 2.

[Table] Comparison A sintered body was prepared and tested in the same manner as in Example 1 except that B ₂ O ₃ was used instead of BN in Example 1. The results were as shown in Table 3.

〔Effect of the invention〕

In place of B ₂ O ₃ , boron nitride, which does not dissolve in water and forms nitrogen-containing aluminoborosilicate or nitrogen-containing borosilicate glass in coexistence with silica;
Alternatively, by using a nitrogen compound and a boron compound powder, it is possible to economically produce a fibrous porous body that is more stable and strong than when B ₂ O ₃ is used.

Claims (1)

[Claims] 1. A porous molded product made of one or both of Al ₂ O ₃ -SiO ₂ fibers and SiO ₂ fibers, in which the fiber-to-fiber contact portions are fused by nitrogen- and boron-containing glass. Fiber porous refractories. _2. Al _, Si _{, B} , O,
A fibrous porous material made by dispersing powder of boron nitride or a nitrogen compound and a boron compound in water to form a glass network structure consisting of N or Si, B, O, and N, vacuum forming it, and firing and sintering the formed product. Method of manufacturing refractories. 3 Boron nitride, nitrogen compound and boron compound powder have an average particle size of around 10 μm and more than 80% by weight have a particle size of 1 to 1.
Claim 2 having a particle size distribution of 44 μm
A method for producing a fibrous porous refractory as described in 2. 4. The fibrous porous refractory according to any one of claims 2 and 3, wherein boron nitride or a nitrogen compound and boron compound powder are used in 2 to 7 parts by weight in terms of B ₂ O ₃ per 100 parts by weight of fibers. How things are manufactured.