JPH0123422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is capable of suppressing the escape of additives contained in porous glass without using an enclosure when sintering the glass, and of performing pressure sintering even at relatively low temperatures. Regarding possible sintering methods.

As a conventional method for sintering a porous body or an aggregate of granular materials, there is a method shown in FIG. This involves enclosing a porous body 10 in a pressure transmitting container 11, inserting this into a heating furnace 12, supplying pressurized fluid into the furnace, and applying static pressure from this fluid to the porous body together with the container. This method involves sintering by heating. This method allows (i) materials that are difficult to sinter to be sintered at relatively low temperatures and in a short period of time, resulting in a high-density body; and (ii) static pressure can be applied isotropically by applying fluid. Therefore, it is useful because it has the advantage that it can be sintered while maintaining its shape before sintering. On the other hand, a difficulty with this method is the problem with the pressure transmission container required when applying pressure with a fluid. This pressure transmitting container must not allow fluid molecules to pass through the inside of the container, withstand high temperatures, and be easily deformed in response to pressurization. Traditionally, this container has been designed to meet the sintering conditions, such as temperature, pressure,
Special metals, glass materials, etc. are used depending on the material of the object to be sintered. However, in the method using this container, the container tends to contaminate the object to be sintered, and it is necessary to use a special material to avoid contamination. Further, there is a drawback that it is troublesome to remove the container after sintering. Furthermore, if the gap between the container and the object to be sintered is large, when pressurizing them, there will be a time lag in applying pressure to the object to be sintered, and this partial deviation in pressure will cause the object to be sintered to may undergo deformation.

The present invention provides a sintering method that eliminates the above-mentioned drawbacks, and its structure consists of melting the surface of a porous glass body by transforming the surface layer of the porous glass body into a molten glass layer without holes. It is characterized in that it is covered with a glass film layer, and then the molded body is heated and sintered using a fluid while applying static pressure from the outside.

The present invention will be explained in detail below with reference to the drawings.

As the porous glass body of the present invention, a glass fine particle body formed by a VAD method, an external deposition method, an internal deposition method, etc., or a porous glass body formed using phase separation can be used. The porous glass body 20 is inserted into a heating furnace and heated from the outside for a short time to melt its surface layer and transform it into a molten glass layer without holes. Cover the body 20. The thickness of the molten glass film layer 21 is 3 when the porous glass body 20 has a diameter of about 50 mm.
It is sufficient if it is about mm. In addition, the film layer 21 of molten glass
When forming the porous body 20, it is preferable to hold the porous body 20 in a He atmosphere in advance and then heat it to form the membrane layer 21. By the He gas treatment described above, the gas adsorbed on the surface of the porous body 20 is removed, and He gas is adsorbed on the surface of the porous body 20 instead. Although He gas easily dissolves and diffuses in the porous body 20, it does not react with the components of the porous body 20 because it is inert. Therefore, the porous body 20 on which He is adsorbed does not generate bubbles during the pressure treatment after forming the molten glass film layer 21, and a high-density sintered body can be obtained. Next, the porous glass body 20 provided with the molten glass film layer 21 on its surface is inserted into a heating furnace, and pressurized gas having a predetermined flow pressure is supplied to the heating furnace to statically heat the porous glass body 20. Hot sintering the porous glass body 20 by heating the inside of the furnace to a high temperature while applying pressure;
A sintered glass body 22 is made.

According to the sintering method of the present invention described above, since the molten glass film layer 21 covers the surface of the porous glass body 20, there is no need for a container as used in conventional pressure sintering. This eliminates the need to remove the pressure transmission container after sintering. Furthermore, the body to be sintered is not contaminated by the pressure transmission vessel. In addition, in the present invention, since the surface of the porous glass body itself is melted to form a film layer, it is possible to easily sinter the container and the body to be sintered, since they are of the same glass quality and can be easily sintered. Deformation distortion and the like due to gaps do not occur. In the production of optical fibers, the glass film layer can also be formed to be relatively thick so that it also serves as a cladding part.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the equipment configuration of the conventional pressure sintering method.
2 to 4 are explanatory diagrams of the sintering method according to the present invention, in which FIG. 2 shows a porous glass body before sintering, and FIG. 3 shows a porous glass body with a molten glass film layer formed thereon. Figure 4 shows a sintered glass body. In the drawings, 10, 20... porous glass body, 11
... Pressure transmission container, 12 ... Heating furnace, 13 ...
Pressurized fluid, 21... molten glass film layer, 22... sintered glass body.

Claims (1)

[Scope of Claims] 1. The surface layer of the porous glass body is transformed into a molten glass layer without pores, so that the surface of the porous glass body is covered with a molten glass film layer, and then this molded body is exposed to the outside by a fluid. A method for sintering a porous glass body, characterized by heating and sintering it while applying static pressure. 2 After maintaining the porous glass body in a He atmosphere,
A method for sintering a porous glass body according to claim 1, characterized in that the surface layer of the porous glass body is transformed into a molten glass layer without pores.