JPH0226862A - Production of silica sintered body - Google Patents

Abstract

PURPOSE:To produce a sintered body of an accurate shape at a low temp. by hot pressing hyperfine silica powder in high vacuum. CONSTITUTION:Hyperfine silica powder of <=500Angstrom , preferably 50-200Angstrom average particle size is hot pressed at 500-800 deg.C, preferably 550-700 deg.C under 0.05-10t/cm<2>, preferably 0.1-0.5t/cm<2> pressure in high vacuum of 10<-2>-10<-9>Torr, preferably 10<-4>-10<-6>Torr degree of vacuum to obtain a silica sintered body. When the oxides of rare earth elements are added to the silica powder, a sintered body of silica-based multicomponent glass or ceramic can be obtd. The amt. of the oxides added is 0-30 pts.wt., preferably 1-5 pts.wt. per 100 pts.wt. silica powder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for producing a sintered body based on silica at a low temperature.

[Prior art and its problems]

Until now, in order to manufacture silica sintered bodies, 1500
A melting method that cools silica melted at a high temperature of ℃ or higher,
A sol-gel method is used in which silica gel made in a solution is dried and heated to about 1000°C. but,
The former melting method has the problem of requiring high temperatures;
On the other hand, the latter sol-gel method has the problem that the shape changes during sintering due to contraction of the gel. Therefore, it is difficult to obtain a silica sintered body with an accurate shape at a low temperature using conventional methods.

[Purpose of the invention]

An object of the present invention is to provide a method that can produce a silica sintered body with an accurate shape at a low temperature.

[Means for solving problems]

The method of the present invention involves processing ultrafine silica powder in a high vacuum at a temperature of 50°C.
This method produces a silica sintered body with an accurate shape by hot pressing at 0 to 800°C.

The ultrafine silica powder used in the present invention has an average particle size of 500 Å or less, preferably in the range of 50 to 200 Å. The finer it is, the more preferable it is. Ultrafine powder of rare earth oxide or the like can be added to this ultrafine silica powder, if necessary. The amount added is 0 to 30 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of ultrafine silica powder. Ultrafine powder of a composite oxide of silica and rare earth oxide can also be used as a starting material. By using such additives, multi-component glass or ceramic sintered bodies based on silica can be obtained.

To do so. In this case, the heating temperature is 500-800°C, preferably 550-700°C. As for the vacuum conditions, 1
0''''-10-'Torr, preferably 10-'-10
-' Torr high vacuum is employed. Press pressure is 0
．． 05-10ton/aJ, preferably 0.1-0.5
ton/j.

[Effects of the Invention] According to the method of the present invention, in addition to single-component silica sintered bodies, by adding appropriate additives, multi-component glass or ceramic sintered bodies with silica family as a base can be made at low temperature. The shape can be manufactured accurately.

In the present invention, unlike conventional methods, the glass is not heated to high temperatures, so it is possible to avoid the contamination of impurities from containers, etc., and also to avoid the problems of phase separation and crystallization that occur when producing multi-component glasses. Furthermore, unlike the conventional sol-gel method, organic matter is not used as a raw material, so contamination of carbon and the like as impurities can be avoided. Moreover, if the vacuum is thoroughly evacuated, moisture can also be thoroughly removed. In addition, depending on the conditions of hot pressing, a highly porous sintered body can be made, and by allowing the strain caused by pressing on the -axis to remain, it is also possible to manufacture glass with strong anisotropy.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Aerosil 200 (particle size: about 12 nm) manufactured by Nippon Aerosil Co., Ltd. was used as ultrafine silica powder as a raw material for the examples.

10.4 g of this powder, which had been exposed to the atmosphere, was processed in a vacuum hot press device (Osara Shinku Giken ■H). In this case, the die is made of graphite and has an inner diameter of 501 mm.
The die had an m+ cylinder shape, and a thin layer of boron nitride powder was applied to the inner surface of the die. Also, before evacuation, a 0.5 ton load was applied to the ultrafine silica powder, and after crushing it, it was evacuated, and when the vacuum reached 5 × 10-'Pa, a 4 ton load was applied at 600°C. I pressed it. In this way, a sintered body of silica was obtained. The bulk density of the sintered body is 0.642 g/am3,
The filling rate is about 24%. The color was white. When this fractured surface was inspected using a scanning electron microscope, a few irregular particles were observed here and there, but the rest of the surface was almost smooth and uniform.

sub-agent

Claims (2)

[Claims] (1) Ultrafine silica powder is heated to a temperature of 500 to 800 in a high vacuum.
A method for producing a silica sintered body, characterized by hot pressing at 0°C. (2) The method according to claim 1, wherein the ultrafine silica powder contains a rare earth oxide as an additive.