JPS61141683A - Heat insulating structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a heat insulating structure with improved heat insulation properties.

[Conventional technology]

Ceramic refractory materials used to protect winged recovery vehicles from aerodynamic heating during atmospheric reentry are lightweight, heat resistant,
Excellent heat insulation properties are required.

Incidentally, conventionally, the surface of reused spacecraft such as the NASA Space Shuttle in the United States has been protected using a heat-resistant member called silica tile. This heat-resistant member is
High-purity SiO2 fibers are used without a binder or colloidal silica is used as a binder, and this
9 bs/ft or 22 bs/ft fired at 00°C
ft3 made of polyrigid material. For this reason, there is a problem that the strength is low and it may chip due to acoustic fatigue during use or peel off from the adhesive surface of the aircraft body.

In order to solve the above-mentioned problems, silica tiles have been reinforced by mixing aluminosilicate fibers or aluminoboron silicate fibers in a weight ratio of 19:1 to 1:19.

However, those containing aluminosilicate fibers have the disadvantage of large shrinkage at high temperatures.

In addition, those containing aluminoboron silicate fibers have a drawback that the aluminoboron silicate fibers have a large au+i diameter (11 μm on average), resulting in high thermal conductivity and high cost.

On the other hand, inorganic multi-rigid insulation materials that have been put into practical use in Japan are those made by bonding inorganic fibers such as rock wool, glass wool, and aluminosilicate fibers with inorganic binders such as colloidal silica and alumina sol, or foam glass and asbestos foam materials. There are inorganic foam materials such as Perlite, Vermiculite, Shirasu and other foam materials as main raw materials, calcium silicate retaining materials, heat insulating bricks, etc.

(Problems to be Solved by the Invention) However, the above-described heat insulating material has the following drawbacks.

(1) At temperatures around 1300° C., the heat resistance is insufficient and thermal deterioration occurs, making it impractical.

(2) The low density amount (0.10-0.40g/Cm3) is
Low strength and brittle.

(3) The coefficient of thermal expansion is large and the thermal shock resistance is poor.

(4) The thermal conductivity is relatively high and the heat insulation properties are poor.

The present invention aims to provide a heat insulating structure that has high mechanical strength, reduces heat conduction at high temperatures, and improves heat insulation performance.

[Means for solving problems]

The present invention uses silica fibers with an average fiber diameter of 0.3 to 3 μm.
00 parts by weight, 115 to 100 parts by weight of alumina with an average IIAM diameter of 1 to 5 μm, 1 to 20 parts by weight of silicon carbide whiskers with an average diameter of 0.5 μm or less, and 0 parts by weight of boron oxide.
．． This is a heat insulating structure characterized by containing 5 to 10 parts by weight.

A detailed explanation will be given below with reference to FIGS. 1 and 2.

1 in the figure is a heat insulating structure made of a highly heat-resistant inorganic material. As shown in FIG. There is.

The main fibers 2 are made of high-purity silica fibers having heat resistance, heat insulation properties, and a small coefficient of thermal expansion, and having an average fiber diameter of 0.5 to 3 μm.

The reinforcing fibers 3 improve the heat resistance and strength of the heat insulating structure 1, and are made of heat resistant and high strength alumina fibers. The reinforcing fiber 3 is blended in an amount of 5 to 100 parts by weight with respect to the main fiber 2 (100 parts by weight). The radiation agent 4 reduces the transmission of radiant heat at high temperatures, and is made of silicon carbide whiskers having a high radiation rate. This radiant material (silicon carbide whisker) has a diameter of 0.5 μm or less in order to increase the surface area, and 1 to 2
0 parts by weight is blended. Note that boron oxide is attached to these fibers and whiskers. This boron oxide acts as a binder between fibers, which will be described later, and also acts to suppress crystallization of high-purity silica fibers at around 1000°C.
．． It is blended in an amount of 5 to 10 parts by weight. Furthermore, 5 in the diagram is 1 fiber II! 2 and reinforcing fibers 3 or the like, or the fibers and the radiation material (silicon carbide whiskers) 4. This cross contact point 5 is caused by the boron oxide attached to the surface of the fibers, which causes the fibers to sinter at high temperature. It is formed by softening and joining. By such cross contact 5, 1
The fibers M2, the reinforcing fibers 3, and the radiant material 4 are formed into a three-dimensional network.

The reason for limiting the blending amount of reinforcing fiber (alumina fiber) 3 to the above main 1!1li2 (100 parts by weight) to the above range is that if the blending amount is less than 5 parts by weight, the reinforcing effect will not be exhibited. If the blending amount exceeds 100 parts by weight, the thermal expansion coefficient and thermal conductivity of the heat insulating structure will increase, resulting in a decrease in heat resistance performance.

The reason is that the amount of the radiant material (silicon carbide whiskers) 4 added to the 1 fiber N2 (100 parts by weight) is limited to the above range. However, the amount is 2
If it exceeds 0 parts by weight, the thermal expansion coefficient and thermal conductivity of the heat insulating structure will increase, resulting in a decrease in heat resistance performance.

The reason why the amount of boron oxide added to the main fiber 2 (100 parts by weight) was limited to the above range is that if the amount is less than 0.5 parts by weight, the degree of fusion with the fiber component will decrease.
The strength of the heat insulating structure decreases, but the amount decreases by 1
If it exceeds 0 parts by weight, softening and melting with the i1M component will become significant, resulting in a heat insulating structure with poor heat resistance.

In order to manufacture the above-mentioned heat insulating structure, for example, a method may be adopted in which each fiber, whisker, and boron oxide are stirred and dispersed in distilled water, and then dehydrated and dried using a filter press to uniformly disperse each of the 11 fibers. .

[Effect]

According to the present invention, as shown in FIG. 1 and FIG. Reinforcing fibers 3 formed from alumina fibers and radiant material 4 formed from silicon carbide whiskers that reduce transmission of radiant heat transfer
By blending a predetermined amount of each and fusing inter-fibers and fibers with whiskers using boron oxide to form cross-contact points 5 to form a three-dimensional network structure, a heat-resistant, lightweight, and high-strength heat insulating structure is created. You can get body 1.

[Embodiments of the invention]

Examples of the present invention will be described in detail below.

Example After stirring and dispersing raw materials for heat insulating structures having the compositions shown in the table below in distilled water, dehydration and drying were carried out using a filter press to obtain each tlAM.
A heat insulating structure in which the following materials were uniformly dispersed was manufactured.

Therefore, the density, thermal conductivity, tensile strength, tensile modulus, and heat resistance of the heat insulating structure of this example were investigated. The results are also listed in the same table. In addition, in the table, a heat-resistant structure containing no silicon carbide whiskers and a heat-insulating structure manufactured using silicon carbide whiskers having a large fiber diameter are also listed as Comparative Examples 1 and 2, respectively.

As is clear from the table above, the heat insulating structure of the present invention includes a heat insulating structure that does not contain silicon carbide whiskers (Comparative Example 1) and a heat insulating structure that uses silicon carbide whiskers with a large fiber diameter (Comparative Example 2).
), the thermal conductivity at high temperatures is lower, and the strength and elastic modulus are significantly higher. Due to these characteristics, it is suitable as an external heat insulating material for reusable and recoverable rockets.

〔Effect of the invention〕

As detailed above, according to the present invention, by blending small-diameter silicon carbide whiskers with silica fibers, alumina fibers, and boron oxide, a heat insulating structure with low thermal conductivity and significantly improved strength and heat resistance is obtained. can be provided.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a heat insulating structure of the present invention, and FIG. 2 is an enlarged explanatory view of section A in FIG. 1. DESCRIPTION OF SYMBOLS 1... Heat insulation structure, 2... 1 fiber 1 (high purity silica fiber), 3... Reinforcement fiber (alumina fiber), 4... Radiant material (silicon carbide whisker), 5... Intersection contact. Applicant Sub-Agent Patent Attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] 5 to 5 parts by weight of alumina fibers with an average fiber diameter of 1 to 5 μm per 100 parts by weight of silica fibers with an average fiber diameter of 0.3 to 3 μm
100 parts by weight of silicon carbide whiskers having an average diameter of 0.5 μm or less, 1 to 20 parts by weight, and 0.5 to 10 parts by weight of boron oxide.