JP2553372B2 - Method for manufacturing SiC filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a SiC filter that can be used for filtration of molten metal or filtration of gas.

2. Description of the Related Art A filter is used, for example, to remove dust in a clean room used in a semiconductor manufacturing process or to filter solids such as metal oxides and non-metal inclusions in a molten metal.

Problems to be Solved by the Invention By the way, as a filter used in a clean room, an organic filter having a small pore size is used.
Since the collected dust is charged, it aggregates on the surface of the filter layer, and when it becomes large to some extent, it falls off from the filter and recontaminates the inside of the clean room.

Further, the ceramic filter used for filtering the molten metal has insufficient mechanical strength at high temperature and has poor durability.

For the above reasons, SiC, which is a semiconductor in a clean room and is not easily charged, is being studied. Further, a filter having a high mechanical strength has been desired as a filter for molten metal.

OBJECT OF THE INVENTION The present invention solves the above-mentioned problems, dust collected when used in a filter for filtration of gas does not aggregate,
Moreover, it aims at providing the manufacturing method of the SiC filter which can exhibit the outstanding durability when used for the filter for metal melts.

SUMMARY OF THE INVENTION This invention has the claims as its gist.

Means for Solving Problems First, a SiC sintered body having a predetermined shape is obtained. The entire SiC sintered body, that is, all the SiC particles from the outer peripheral portion to the inner peripheral portion are heat-treated in an oxidizing atmosphere, and SiO _{2 is} applied to the surface of the SiC particles.
After the film is formed, it is treated with hydrogen fluoride (HF) to remove the SiO ₂ film. By repeating this heat treatment and the treatment with hydrogen fluoride, the pore diameter between all the SiC particles becomes a predetermined diameter.

Example A cylindrical SiC sintered body of which one side is opened is heat-treated in an oxidizing atmosphere after sintering, and a SiO ₂ film of 100 angstrom, for example, is formed on the surface of SiC particles. Then, it is treated with hydrogen fluoride (acid) to remove the SiO ₂ film. By repeating the heat treatment and the hydrofluoric acid treatment, it is possible to form pores having a predetermined diameter between the SiC particles.

Table 1 shows each example made as described above. However, the examples of Nos. 17 to 21 show the case where the number of times of processing is 1 and the processing is performed for a long time for comparison.
With these, the growth speed of the SiO ₂ film is slow.

Further, FIG. 1 shows the relationship between the treatment time and the pore diameter at each temperature. As the treatment time increases, the pore size decreases linearly. That is, the pore size can be freely controlled by the treatment time (or the number of repetitions).

By the way, the SiC filter manufactured by the present invention is not limited to the above-mentioned filter shape.

Effect of the Invention The entire pores including the inside of the SiC sintered body are heated in an oxidizing atmosphere, treated with hydrogen fluoride (acid), and these treatments are repeated, whereby the pore diameter in the filter can be controlled.

[Brief description of drawings]

 FIG. 1 is a diagram showing the relationship between processing time and pore diameter.

Claims (1)

(57) [Claims] 1. A SiC filter manufactured by heating the whole of a SiC sintered body including the inside in an oxidizing atmosphere, then treating with hydrogen fluoride, and repeating the heating and the treatment with hydrogen fluoride. Method.