JPS58199713A - Manufacture of needlelike mullite crystal powder - Google Patents

Abstract

PURPOSE:To manufacture needlelike mullite crystal powder by hydrothermally treating a substance contg. Al and a substance contg. Si at high temp. and pressure using water as a medium and carrying out calcination. CONSTITUTION:A substance contg. Al is mixed with a substance contg. Si so as to make the atomic ratio of Al/Si >=about 2, and hot water regulated to >=550 deg.Chigh temp. and >=10kg/cm<2> high pressure is allowed to act on the mixture. The resulting powdered precipitate is taken out by filtration, dried, and calcined to manufacture needlelike mullite crystal powder.

Description

[Detailed description of the invention] The present invention relates to a method for producing acicular mullite crystal powder.

More specifically, the present invention relates to a method of hydrothermally treating an aluminum-containing material and a silicon-containing material to produce an acicular alumino-silicate compound, and firing the ridge to produce a single-acicular mullite powder.

Conventionally, mullite porcelain and other alumino-siliferous ceramics have been widely manufactured and used. Mullite and some to phantom glass coexist. This causes a decrease in the strength or melting point of mullite porcelain,
The current situation is that mullite's original properties cannot be fully demonstrated.

Therefore, if acicular mullite crystal powder can be selectively obtained, it is fully possible to obtain ceramics with high strength and high melting point by sintering it.

However, there are usually two types of mullite crystals: needle-like and lump-like.
is obtained when the composition of mullite is made into a melt at a high temperature of 1850° C. or higher and then cooled. Moreover, in this case,
It is necessary to delicately control the cooling rate, and
Glassy substances usually coexist in all cases.

In view of these conventional problems, the present inventors conducted extensive research and arrived at the present invention. That is, an aluminum-containing material and a silicon-containing material are mixed using water as a medium.
The inventors have invented a method for producing acicular mullite powder by hydrothermal treatment at a temperature of 0° C. or higher and a pressure of 10 kl/d or higher, followed by calcination.

The aluminum-containing material used in the present invention is plandum.

Including α-alumina such as emery, su7aiya, ruby, etc., non-hydrated alumina such as r-1δ-1θ-1-1 μm, χ-alumina: quipsite (hydrargilite), beidellite, notostrandite, Hydrated alumina such as bauxite, boehmite, diamond bore, toadite; in addition to solely hydrated and non-hydrated amorphous alumina, compounds 1 that can be converted into hydrated or non-hydrated alumina by hydrothermal treatment.

Aluminum metal; aluminum salts such as aluminum sulfate, aluminum nitrate, and aluminum chloride; aluminates such as sodium aluminate and ammonium aluminate; triethylaluminum, aluminum triethoxyde, aluminum triisopropoxide, aluminum trin- Examples include organometallic aluminum compounds such as butoxide.

The silicon-containing substances used in the present invention include crystalline silica such as α- and β-quartz, α- and β-tridymite, and α- and β-climetopalite; In addition to silica, hydrothermal treatment ml
Compounds that can become crystalline or amorphous silica, such as metal silicon, metals such as 7 yellow silicon, silicon salts such as silicon tetrachloride; silicates such as sodium silicate and ammonium silicate; tetraethylsilane, polydimethyl silicon , organic silicon compounds such as silicon tetraethoxide, and the like.

In the present invention, hydrothermal treatment is performed in the coexistence of an aluminum-containing material and a silicon-containing material. In this case, it is preferable to mix the two in advance. Moreover, a compound containing both aluminum and silicon can also be used. Konoyo 5
Examples of such compounds include clay minerals such as kaolinite, nacrite, dietschite, halloysite, mo/molypnite, beidellite, nonitronite, saponite, illite group, and pyrophyllite.

The ratio of aluminum-containing materials to silicon-containing materials is A.
It is preferable that the molar ratio of l/St is 2 or more, and 11
If the 71310 molar ratio is less than 2, silica content will remain in the resulting powder.

Hydrothermal treatment in the present invention means applying hot water at high temperature and high pressure, and hot water at high temperature and high pressure is above the boiling point and above the flat beak vapor pressure, that is, above 100°C and above 1 Y/-. K is 550°C or higher to obtain acicular powder.

Hot water of 1θ kg/d or more must be used. still,
As long as there is no problem, additives such as acids, alkalis or salts may be used as reaction accelerators at °C.

In the present invention, acicular mullite powder is obtained by calcination after hydrothermal treatment under the above conditions.However, by setting the calcination temperature to 100°C or higher, the formation of mullite in the hydrothermal treatment product is promoted. The produced acicular mullite powder is kneaded and molded with various binders, etc., and when fired, it can be used to make various fired bodies, as well as to give a fragrance to resins, cement, metals, etc., and to be used as a fiber reinforcement material. , can be used for various purposes.

In the case of making a sintered body, it was obtained by hydrothermal treatment.

By using the acicular alumino-silicate compound powder as it is, shaping it, and then firing it, it is also possible to perform mullite formation and sintering in one process.

Next, the present invention will be explained in a different manner with reference to Examples. In the following, 1, part and % are all based on tumor volume unless otherwise specified.

Example Alumina sol (Alumina sol 200 manufactured by Nikichi Kagaku ■; kl
tO, content 10%) and silica sol (Nippon Kagaku ■Snowtex o; sto, content 20%) were mixed in a mixer at ℃, and this mixture (Aj/81 molar ratio = 3/1)
was placed in a cone-in-cone pressure vessel, and the temperature was 600°C using water as a medium.

Claims (1)

[Claims] An acicular mullite crystal powder characterized in that an aluminum-containing material and a silicon-containing material are hydrothermally treated using water as a medium at a temperature of 550° C. or higher and a pressure of 10 to 5+/aIIP or higher, followed by firing. Production method.