JPH0466811B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for producing glass by a sol-gel method, and particularly to a method for producing a gel suitable for producing additive-type silica glass.

[Background of the invention]

Conventionally, when producing a glass body by the sol-gel method, as shown in FIG. 1, a metal alkoxide is hydrolyzed with water to produce a gel, then the gel is dried, and then sintered at an elevated temperature. In this case, it is possible to create a gel by using acidic, neutral, or alkaline water in the hydrolysis process, but if you are trying to obtain a large transparent glass body, use alkaline water (for example, aqueous ammonia). It has become essential to hydrolyze it. The reason for this is that when hydrolysis is carried out under acidic or neutral conditions, the pores become smaller and _the bulk density of the gel becomes larger. This is because a foaming phenomenon occurs due to (e.g.). In comparison, when hydrolysis is carried out under alkaline conditions, a gel with relatively large pores and low bulk density can be created, and during transparent vitrification, adsorbed gas is smoothly released and problems such as foaming are less likely to occur. It is from.

However, when creating a glass body consisting of multiple components, hydrolysis under alkaline conditions often produces a compositionally heterogeneous gel, and sintering this gel only yields a heterogeneous glass body. There were flaws.

[Purpose of the invention]

An object of the present invention is to provide a method for producing a homogeneous gel suitable for producing a homogeneous additive-type transparent glass body that eliminates the above-mentioned drawbacks.

[Summary of the invention]

According to the method of the present invention, in the method for producing additive silica gel, in which silicon alkoxide or silicon alkoxide containing other metal alkoxides is hydrolyzed with water or an aqueous solution containing metal ions, gelled and dried, Additive silica gel with large pores and high homogeneity can be produced by hydrolyzing it under acidic or acidic conditions and then gelling it under alkaline conditions.

[Embodiments of the invention]

This will be explained in detail below using examples.

Example As shown in Figure 2, 5 mol% Ge(OCH ₃ ) ₄
4.5 mol of CH ₃ per 1 mol of Si(OCH ₃ ) ₄ containing
OH was added, and to this was added 4 molar 0.01N HC aqueous solution with stirring to complete the hydrolysis reaction. Then, 1N-NH ₄ OH was added to this solution,
Gelation was carried out at an ammonia concentration of approximately 1/100 to 1/10. When this gel was slowly dried in a constant temperature bath at 70°C, a dried gel with a bulk density of about 0.6 g/cm ³ was obtained. For comparison, we dried the gel without preparing ammonia.
The gel bulk density was 1.1 g/cm ³ . When these dried gels were heated to 1300° C. in an electric furnace, the alkali-prepared gels became transparent glass bodies (glass A). Furthermore, the gel without ammonia preparation was a transparent glass body (glass B) at 1100°C, but foamed when the temperature was raised to 1300°C.

On the other hand, for comparison, the above Ge(OCH ₃ ) ₄ is
When a gel was prepared by directly hydrolyzing Si(OCH ₃ ) ₄ containing mol % using a 0.01N NH ₄ OH aqueous solution, a dry gel with a bulk density of 0.59 g/cm ³ was obtained. When this was similarly heated and sintered, a transparent glass body (glass C) was obtained at 1300°C.

Next, in order to examine the optical properties of Glass A, Glass B, and Glass C, we cut them into approximately 50 μm thick pieces, optically polished them, and measured their light transmittance in the wavelength range of 210 to 360 nm. The light transmittance is
However, glass C exhibited large absorption with a peak at 242 nm. According to the literature, this peak appears when GeO is present in the glass, and it can be seen that glass C has a lower homogeneity than A and B. Therefore, it can be seen that Glass A, which was prepared by hydrolyzing with an acidic aqueous solution and then gelling with an ammonia aqueous solution, is a highly homogeneous glass that does not foam even at high temperatures.

In the above examples, Ge (OCH ₃ ) was used as the second component.
₄ was used, but instead of Ge, A, Sb, Ta, Ti,
The method of the present invention can also be applied when one or more additive elements such as Zr, Ga, and Nb are used.

〔Effect of the invention〕

As explained above, according to the present invention, a gel that is extremely homogeneous and has a low bulk density can be created, and by sintering this gel, a homogeneous glass body made of multiple components without foaming can be manufactured.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the steps of a conventional process;
FIG. 2 is an explanatory diagram showing the steps of the process of the present invention. 1...Alkoxide + water or HC or NH ₄
OH aqueous solution + alcohol, 2, 8...gel, 3,
3', 3'', 3... Gel preparation container, 4, 4', 9,
9'...Dried gel, 5,5'...Electric furnace, 6...Alkoxide + HC aqueous solution + alcohol, 7...
Alkaline prepared hydrolysis solution.

Claims (1)

[Claims] 1. Hydrolyzing silicon alkoxide or silicon alkoxide containing other metal alkoxides with water or an aqueous solution containing metal ions,
1. A method for producing additive silica gel which is formed by gelling and drying, the method comprising carrying out hydrolysis under neutral or acidic conditions and gelling under alkaline conditions.