JPH0428666B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat insulating structure and a method for manufacturing the same. Conventionally, the surface of reused spacecraft such as the NASA Space Shuttle has been protected using a heat-resistant material called silica tile. This heat-resistant member is made of a polyrigid material of 9 lbs/ft ³ or 22 lbs/ft ³ made of high-purity silica fiber without a binder or using colloidal silica as a binder and fired at approximately 1300°C. has been done.
As a result, they were weak in strength and suffered from chipping or peeling off from the adhesive surface of the fuselage due to acoustic fatigue during use. In order to solve this problem, a reinforced silica tile has been developed in which alumina silicate fibers or alumina boron silicate fibers are mixed in a weight ratio of 19:1 to 1:19.
However, those containing aminasilicate fibers have the disadvantage of large shrinkage when exposed to high temperatures. In addition, those containing aminaboron silicate fibers have the disadvantage of high thermal conductivity and high cost because the fiber diameter of aminaboron silicate fibers is large (average 11 μm). On the other hand, the inorganic multi-rigid rigid insulation materials that have been put into practical use in Japan include those made by bonding inorganic fibers such as rock wool, glass wool, and alumina silicate fibers with inorganic binders such as colloidal silica and aminasol, as well as foam glass and asbestos foam materials. Inorganic foam materials such as perlite, vermiculite,
There are molded products made mainly from foam materials such as shirasu, calcium silicate insulation materials, and insulating bricks. This heat insulating member has the following drawbacks. 1. At temperatures around 1300°C, it is not practical due to insufficient heat resistance and thermal deterioration. 2 Low density (0.10 to 0.40 g/cm ³ ) has low strength and is brittle. 3 High coefficient of thermal expansion and poor thermal shock resistance. 4. Relatively high thermal conductivity and poor insulation properties. The present invention has been made in view of the above, and provides a heat insulating structure capable of reliably thermally protecting the fuselage structure of a retrievable rocket, and a method for manufacturing the same. That is, in the present invention, silica fibers with an average fiber diameter of 0.5 to 3 μm and alumina fibers with an average fiber diameter of 1 to 5 μm are fused together with boron oxide to form a net-like three-dimensional structure. A thermally insulating structure with a density in the range of 0.40 g/cm ³ . Furthermore, in the present invention, the average fiber diameter is 100 parts by weight of silica fibers having an average fiber diameter of 0.5 to 3 μm.
After dispersing 5 to 100 parts by weight of alumina fibers of 5 to 5 μm and 0.5 to 10 parts by weight of boron oxide in water, this is dehydrated and molded, and then calcined at a temperature of 1100 to 1400°C for 0.5 to 15 hours to reduce the density. 0.10 to 0.40
This is a method for manufacturing a heat insulating structure in which the temperature is set at g/ ^cm3 . Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of one embodiment of the present invention.
This heat insulating structure 1 is made by fusing silica fibers as main fibers and alumina fibers as reinforcing fibers into a three-dimensional network structure. The fusion of the silica fibers 3 and the alumina fibers 4 causes a portion A of the cross-sectional structure to be
As shown on an enlarged scale in the figure, the intersection is formed by an adhesive member 5 made of boron oxide. The silica fibers 3 used have an average fiber diameter of 0.5 to 3 μm. The alumina fibers 4 used have an average fiber diameter of 1 to 5 μm. Further, the density of the heat insulating structure 1 is set within the range of 0.10 to 0.40 g/cm ³ . As the radiant member 2, inorganic fine powder radiant member 2 such as silicon carbide, silicon carbide whiskers, silicon boride, etc. is dispersed and adhered to the surface of the heat insulating structure 1 in order to reduce transmission of radiant heat and improve heat insulation properties. It is also possible to do so. The heat insulating structure 1 configured in this manner has the following effects. 1. Since silica fiber 3 and alumina fiber 4 are used, it has excellent heat resistance, heat insulation, and strength. 2. Silica fibers 3 and alumina fibers 4 are firmly fused together by boron oxide, and it is possible to prevent thermal deterioration due to crystallization of silica fibers 3 at high temperatures. 3. Radiation heat transfer at high temperatures can be reduced by the radiant member 2. Next, a method for manufacturing the heat insulating structure will be explained. First, the average fiber diameter is 0.5 to 3 μm as the main fiber.
Prepare 100 parts by weight of silica fiber. To this, 5 to 100 parts by weight of alumina fibers having an average fiber diameter of 1 to 5 μm are blended as reinforcing fibers, and 0.5 to 1.0 parts by weight of boron oxide are blended and dispersed in water.
Next, this is dehydrated and molded at 1100 to 1400℃.
Calcinate at a temperature of 0.5 to 15 hours to achieve a density of 0.10 to 0.40.
g/cm ³ to obtain a heat insulating structure. Here, boron oxide acts as a binder, and attaches to the intersections of the silica fibers, which are the main fibers, and the alumina fibers, which are the reinforcing fibers, and binds them together during firing to form a three-dimensional network. It is what creates the structure. Further, boron oxide has the effect of preventing silica fibers from crystallizing when exposed to temperatures around 1000°C. Therefore, the blending amount is preferably set within the range of 0.5 to 10 parts by weight so as to sufficiently exhibit the fusing effect and the crystallization inhibiting effect. Further, in order to reduce radiant heat transfer in the heat insulating structure, a predetermined amount of inorganic fine powder such as silicon carbide, silicon carbide whiskers, silicon boride, etc. may be blended in advance. According to this method of manufacturing a heat insulating structure, silica fiber is used as the main fiber and alumina fiber is used as the reinforcing fiber, so it is easy to produce a heat insulating structure with excellent heat resistance, heat insulation properties, and strength. can be obtained. In addition, since it contains boron oxide, it is possible to firmly fuse the main fibers and reinforcing fibers to form a three-dimensional network structure, and also prevent the silica fibers from crystallizing at high temperatures. . Furthermore, by blending inorganic fine powder in advance, radiant heat transfer at high temperatures can be reduced. Hereinafter, an example of the manufacturing method of the present invention and an experimental example conducted to confirm the effects of the present invention will be described. The composition shown in Table 1 below was dispersed in distilled water and preliminarily dehydrated until the slurry concentration was 1.5%.
This was dehydrated and molded using a filter press, and dried at a temperature of 105°C for 16 hours. Next, this was heated to a temperature of 1350°C at a temperature increase rate of 120°C/h, and after reaching a temperature of 1350°C, a firing treatment was performed for 10 hours. Thereafter, a molding process was performed to obtain a flat heat insulating structure with a thickness of 50 mm and a side of 200 mm. When a characteristic test was conducted on this heat insulating structure, the results shown in Table 2 below were obtained. As is clear from Table 2, this heat insulating structure has extremely excellent properties and was found to be able to reliably protect the airframe structure of the retrievable rocket.

【table】

[Table] As explained above, according to the heat insulating structure according to the present invention, the fuselage structure of a retrieval rocket can be reliably thermally protected. Furthermore, according to the method of manufacturing a heat insulating structure according to the present invention, the fuselage structure of a retrievable rocket can be reliably thermally protected. A heat insulating structure can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a main part of an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing an enlarged internal structure of the embodiment. DESCRIPTION OF SYMBOLS 1... Heat insulation structure, 2... Radiation member, 3... Silica fiber, 4... Alumina fiber, 5... Adhesive member.

Claims (1)

[Claims] 1 Silica fibers with an average fiber diameter of 0.5 to 3 μm and alumina fibers with an average fiber diameter of 1 to 5 μm are fused together with boron oxide to form a network-like three-dimensional structure, and A thermally insulating structure characterized in that it has a density within the range of 0.40 g/cm ³ . 2 After dispersing in water 5 to 100 parts by weight of alumina fibers with an average fiber diameter of 1 to 5 μm and 0.5 to 10 parts by weight of boron oxide to 100 parts by weight of silica fibers with an average fiber diameter of 0.5 to 3 μm. A method for manufacturing a heat insulating structure, which comprises dehydrating and molding this, and then firing it at a temperature of 1100 to 1400°C for 0.5 to 15 hours to set a density of 0.10 to 0.40 g/cm ³ .