JPS59102838A - Devitrification-resistant molded article of fused quartz - Google Patents

Abstract

PURPOSE:To obtain the titled molded article having high resistance to devitrification at a low cost, by coating a molded article of fused quartz with ultra- fine powder of high-purity amorphous silica using a colloidal solution obtained by the hydrolysis of silicon tetrachloride. CONSTITUTION:A molded article 1 of fused quartz having a porosity of about 4-20% is immersed in a colloidal solution prepared by the hydrolysis of silicon tetrachloride. Ultra-fine particles of high-purity amorphous silica 3 having particle diameter of about 0.01mum are brought into the pore 2 by capillary action. The article 1 is taken out of the solution, polished, washed, dried, and baked at about 1,100 deg.C to form the coating layer 4 of amorphous silica on the surface of the molded article 1. The coating layer suppresses the development of alpha- cristobalite and improves the devitrification property. Since the coating layer 4 is made of silica which is the same material as the molded article 1, it is resistant to peeling even at a high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a devitrification-resistant melt-pored substantial molded article.

Fused silica molded bodies have various characteristics. for example,
It has characteristics such as a small coefficient of thermal expansion, excellent thermal shock resistance, and low thermal conductivity. For this reason, fused silica molded bodies have been used in various industries.

However, when conventional fused silica molded bodies are used at high temperatures of 1100° C. or higher, devitrification rapidly progresses. Therefore, in order to prevent this devitrification, conventionally, fused silica molded bodies have been manufactured from high-purity raw materials and subjected to IC, or coated with a material that is resistant to devitrification.

If a fused silica molded body is manufactured using high-purity raw materials,
It certainly becomes stronger against devitrification.

However, the use of highly pure raw materials has resulted in problems such as high costs and non-negligible contamination during the manufacturing process.

Further, even if a coating film such as A 9203, which is resistant to devitrification, is applied to a fused silica molded body, there is a drawback that the coating film peels off due to the difference in thermal expansion.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a devitrification-resistant melt-pore substantial molded body that is resistant to devitrification and can be manufactured at low cost.

The present invention is characterized in that the devitrification-resistant melt-pore substance molded body is a fused silica molded body coated with high-purity amorphous silica with ultrafine particles composed of a colloidal solution prepared by hydrolysis of silicon tetrachloride. It is something to do.

As described above, the devitrification-resistant fused silica molded body of the present invention is coated with ultrafine particles of highly pure amorphous silica. Therefore, the generation of α-cristobalite is suppressed, and it is extremely resistant to devitrification.

The devitrification-resistant fused silica molded body of the present invention does not use high-purity raw materials. Therefore, an inexpensive devitrification-resistant fused silica molded body can be obtained. Also, there is no need to be very careful about contamination during the manufacturing process.

Furthermore, since the amorphous silica coating layer with ultra-fine particles and high purity is a sintered layer of fused silica, which is the same as the fused silica molded body, it is different from conventionally cast A 9203, S +3 N.
There is no danger of peeling off like coating layers such as 4.

The devitrification-resistant fused silica molded product of this invention has the above-mentioned effects, so it is suitable for refractories for the glass industry and jigs for the electronic industry, as well as for firing phosphor materials. can also be used.

With reference to FIGS. 1 and 2, the manner in which the surface of a fused silica molded body is coated with ultrafine amorphous silica particles will be described.

The fused silica molded body 1 has a porosity of 4 to 20%. For this reason, when the fused silica molded body 1 is immersed in a colloidal solution, the colloidal solution will flow into the pores due to capillary action, for example.
invade inside. As a result, amorphous silica 3, which is an ultrafine particle with a particle size of 0.01 μm, enters into the pores 2 (see FIG. 1). In this way, an amorphous silica coating layer 4 is formed on the surface of the fused silica molded body 1 (see FIG. 2).

Various coating methods can be considered.

In addition to the method using the capillary phenomenon described above, it is also possible to apply a voltage to the fused silica molded body 1 and use electrophoresis. Electrophoresis allows coating to occur in a shorter time than capillary action. In addition, it is also possible to impregnate the amorphous silica 3 by pressurizing or reducing the pressure.

Hereinafter, the present invention will be described in more detail with reference to Examples.

A fused silica molded body (which may be used before or after firing) having the properties shown in Table 1 was immersed in a colloidal solution prepared with silicon tetrachloride and pure water and taken out after 5 hours. Then, it was polished, washed with ether and pure water in that order, and dried at 1100 ml.
It was baked at °C for 8 hours. Table 2 shows the physical properties of the devitrification-resistant fused silica molded article of the present invention thus produced.

A copper electrode was placed in a fused silica pipe having the characteristics shown in Table 1 and immersed in a colloid solution.

The same colloid solution as in Example 1 was used and was prepared in a copper container. Then, a positive voltage was applied to the electrode of the fused silica pipe, and a negative voltage was applied to the copper container. The voltage was 20-30V/cn+. After about 10 minutes, the current was turned off and polishing, cleaning, and firing were performed in the same manner as in Example 1. Table 3 shows the physical properties of the devitrification-resistant fused silica pipe of the present invention thus produced.

From Tables 1 to 3, it can be seen that the devitrification-resistant fused silica molded body of the present invention has a smaller porosity than the uncoated molten stone substance or body.

Next, a devitrification test was conducted on the devitrification-resistant fused silica molded body of the present invention and the uncoated fused silica molded body in air at 1300°C. Then, α-
The amount of cristobalite was measured. The results are shown in FIG.

This devitrification test revealed that the devitrification-resistant fused silica molded product of the present invention exhibits superior devitrification resistance compared to an uncoated fused silica molded product.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an example of the surface of the fused silica molded product before coating, FIG. 2 is a partial sectional view showing an example of the surface of the devitrification-resistant fused silica molded product of the present invention, and FIG. It is a graph that does not show the results of a devitrification test of the devitrification-resistant fused silica molded body of the present invention and the uncoated fused silica molded body. 1... Fused silica molded body 2... Pore 1 3... Amorphous silica 4... Coating layer -
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Claims (1)

[Claims] A devitrification-resistant fused pore substantial molded product characterized by coating a fused silica molded product with highly pure amorphous silica with ultrafine particles produced from a colloidal solution prepared by hydrolyzing silicon tetrachloride.