JPH0230651A - Production of raw material for fine ceramics (new ceramics) having ceramic and mineralogically stable mineral facies - Google Patents

Abstract

PURPOSE:To use an inexpensive fuel with high thermal efficiency and obtain a raw material having the same quality as that of electrofused products and high-temperature stable type physical properties even at ordinary temperature by converting fine powder of refractory raw material mineral into a semifused and calcined product with an instant high-temperature flame, jetting and quenching the resultant product into flowing water just under the flame. CONSTITUTION:For example, high-purity alumina or magnesia which is normally fine powder is normally pulverized if the particle size is not suitable to provide -100mum particle diameter. The resultant fine powder is fed to the central part of a high-temperature frame at about 2,100 deg.C using acetylene, propane, etc., and kept in a semifused state. The flame holding the semifused powder is then jetted into flowing water just thereunder and instantaneously quenched. The recovered calcined product is further finely pulverized to the order of submicron and treated with a mineral acid to remove impurities. The treated fine powder is subsequently with water and dried to afford the objective product.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has discovered that in-ceramics can be obtained by instantly quenching fine ceramic raw material fine powder minerals used in the ceramic industry after instantaneous high heat irradiation.

When comparing the fine ceramic material obtained in this way with fine ceramics produced by electrofusion for the purpose of , this difference is due to the fact that the crystals in the substance are finer and the crystal lattice is changed by a later physical method.
It is removed and has completely the same physical properties, so it does not cause any trouble to the cylinder during use.

Despite this, the current situation is that almost all refractory ceramic materials having high melting points and low thermal conductivity are manufactured using irrational and uneconomical operations.

This is difficult to produce even if a conventional high-temperature ceramic furnace is used to obtain the semi-molten lump ceramic material, and an indirect arc is used as a heat source. In addition, as in the case of electrofusion, high electricity charges greatly affect production costs, making its use economically difficult.

In addition, the method for manufacturing refractories containing semi-molten material as in the present invention is known in 1972-30284 (Public Notice No. 46-9-3), but the purpose of the present invention is completely different in its manufacturing method and mechanism. be.

Therefore, when producing fine ceramic materials by electric fusion as at present, there are many unreasonable, disadvantageous, and
Difficulties exist. (1) Impurities in raw materials must be removed using expensive energy.

(2) Most of the electric furnaces used are Nil furnaces, which have a thermal efficiency of 50%.
The front and back are extremely low. (3) Refractory raw materials with a high melting point generally have low thermal conductivity and low viscosity, so they can be electrofused for a long time,
In addition, since the material is taken out and discharged from the furnace, the temperature also rises, resulting in a large unnecessary loss of energy.

(4) When a ceramic material is used as an electric fusion product, a large amount of power energy is required to pulverize the molten cold soul. (5
) When the raw material for electric melting is a fine powder, the raw material is often scattered and scattered due to the blow-up of the electric furnace when the raw material is input, reducing the actual yield. (6
) When operating an electric furnace, it is absolutely necessary to install a dust collector.

The present invention was made for the purpose of rationally industrially producing fine ceramic materials by eliminating all of the above-mentioned processing and uneconomical problems, as well as the difficulty of firing using a ceramic furnace. .

According to the present invention, if the highly refractory ceramic raw material is supplied with an appropriate fine powder within a sufficiently high temperature range, stable transformation transition and dissociative synthesis will be completed instantaneously.

Therefore, it is impossible to control this moment through manipulation.
It is assumed to be 0-'sec.

The present invention (1) involves pulverizing a raw material mineral to an appropriate particle size according to the properties of the mineral, and then using a high-temperature flame injection device such as a ceramic flame spraying equipment to pulverize the fine powder into the center of the injection flame. Firing is carried out by supplying air or nitrogen gas to the part. This flame injection device uses acetylene, propane, etc. as a fuel gas, which is selected appropriately depending on the purpose of semi-melting the mineral, and burns it in oxygen gas to obtain the necessary high-temperature flame, unlike the case of ceramic spraying. There is no need to melt the feed powder at all, and the thermal efficiency used for the semi-molten ceramic material is extremely high <80% or more. The mineral sent to the center of the flame is kept in a semi-molten state while controlling its temperature, and the flame holding the semi-molten powder is rapidly cooled by injecting it into the flowing water directly below it.

Its injection speed is extremely fast, usually 1375 m/sec or more, and therefore the rapid cooling effect can be enhanced.

A special furnace is not required for these operations; all you need to do is build an enclosure with iron plates to prevent the heat source from being cooled by the draft of Tazo air, and there is no need for a dust collector as no dust is generated. There is no.

Ceramic materials sprayed and deposited in water peel and separate from each other to form individual minerals due to differences in expansion and contraction between different types of minerals, and are then sorted into high-purity minerals using physical methods.

The fine ceramic materials produced in this way are characterized by having many primary properties.

It does not have any inter-wall space, does not cause the digestion phenomenon due to moisture etc. which is characteristic of Magnesia, and has increased resistance to mineral acids.

Alumina, magnesia, and many other fine ceramic materials that have been subjected to high-temperature treatment through synthetic dissociation exhibit their own characteristics, and unlike synthetic spinel, they do not shrink after expansion due to heating.

One of the characteristics of this process is that the crystals of the ultrafine powder required by current fine ceramic materials are made finer by this rapid cooling process, which is convenient and beneficial for obtaining ultrafine powder later on.

Invention (2) of the present application is based on Invention (1) and the second method, so that the conventional production of cubic zirconia crystals can be achieved without adding a stabilizer.

The obtained zirconia is a semi-molten microcrystal of a body-centered cubic stable type and does not contain any tetragonal monoclinic crystals, and when heated after that, it has a 0.
As shown in the zirconia thermal expansion curve shown in J. Whittmore, only reversible linear expansion and contraction occurs, and the abnormal transformation transition peculiar to zirconia does not occur.

Therefore, the obtained fine ceramic zirconia material can maintain a quality of 99.9% or more.

Embodiments of this invention will be described in more detail below.

A) - Case of producing a high-temperature stable semi-molten material based on components In the case of invention (1), the production method for alumina or magnesia will be described.

Chemically produced high-purity alumina or magnesia is usually fine, but if the raw material does not have a particle size suitable for the present invention, it is usually ground to 1100 μm and this fine powder is 21 μm.
The product is instantaneously irradiated with a high-temperature flame at 00°C, placed at the bottom of the furnace at a high speed, and washed and dried with water to produce the product.

Furthermore, in the case of invention (2), for example, zirconia depends on the same method as (1), but in this case, the firing temperature is 2350-265.
By firing at about 2500°C within the 0°C range, a fine ceramic material with 100% body-centered cubic zirconia can be obtained.

B) In the case of producing a multicomponent high temperature stable semi-molten material (a) In the case of dissociation of binary minerals As an example, the case where zircon is used as the raw material for the purpose of obtaining zirconia will be described below.

Since zircon raw sand products are sand-like with a particle size of 800 microns or less, they are first ground to 1100 microns using a zirconia ball mill.

This fine powder is supplied to Zirco, which supplies oxygen and fuel gas propane.
Zircon (n) starts to dissociate from 1500℃ and it takes a long time at this temperature to completely dissociate, but at about 1900℃ or higher it is completely 100% instantaneous and this dissociated product is injected into the flowing water directly below the kiln. The thermal expansion coefficient of sudden zirconia is 8.0X10-
'The molten silicic acid is 0.6X10-'', which is significantly different, and the contraction caused by rapid cooling is also significantly different because both minerals undergo linear reversible expansion. Depending on the difference in shrinkage, the zirco material was made into a bulb with a concentration of 60% in water.
Process in an attrition scraper mill. In this mill, the two mineral particles further remove the unpeeled molten silicic acid remaining on the surface of the zirconia particles due to body friction, and the zirconia becomes a single substance, but the tougher zirconia and the brittle molten silicic acid are further removed. Since these minerals have significantly different frability (crushability), it is possible to completely separate both minerals as single substances by processing in the above-mentioned mill.

Furthermore, the purposes of processing with this mill are (1) crushing of the coarse portions of the finely fed zirconia particles that have been fused with molten silicic acid during high-temperature treatment, and (2) crushing of those portions. When selecting the ratio of both minerals, the minimum amount of particles fed to the slime table is +70 μm, so pulverization of zirconia particles is prevented as much as possible. Since residual stress due to lattice distortion remains in the crystal, external pressure is applied to the surface of the zirconia particles by milling to remove the lattice distortion.

It is completely removed by this large external pressure. Again, this distortion can be completely removed if necessary.

The second type minerals discharged from the above mill are classified with a taracifier using a wet cyclone etc., and the pulp density is 30.
Perform specific gravity beneficiation on a slime table at %. The sorting ability of this slime table is capable of fine selection within ±5 μm, and normally with this kind of slime table, the possible specific gravity difference is 1, and the specific gravity difference is as large as 4.0 (therefore, the above-mentioned single substance separation is completely If this process is carried out, it is possible to selectively separate these two minerals, and the actual yield is as high as 95%, making it possible to efficiently obtain the two products of zirconia and fused silicic acid.

Also, with this specific gravity, high-purity zirconia carefully selected by slime flotation can be obtained by heavy liquid mold breaking using a TBE (S, G, 3.0) cyclone.

The power required for the table, etc., including the flotation process described above, is small and contributes greatly to cost economy.

Thereafter, if necessary, the powder is finely pulverized using a microsizer, and any distortion of the crystal lattice that may still remain is completely removed by the large external pressure of this pulverization.

It is possible to obtain high purity molten silicic acid.

When zircon is used as a raw material for the purpose of obtaining zirconia, 60% zirconia and 30% molten silicic acid can be obtained from zircon, calculated from the zirconia content of zircon and the mold failure yield.

(b) Synthesis of binary minerals The synthesis of flannel, which produces semi-molten materials, will be described below.

G., A., Ramkist and H.E., Merw.
In 1916, the synthesis of both minerals starts at 1600℃, which shows the equilibrium state of the binary system.
It takes a long time to completely synthesize spinel, which becomes 1" cubic microcrystals. (Semi-molten) This synthesized spinel is injected into flowing water and rapidly cooled to form semi-molten high temperature stable spinel. You can get it.

This synthesized spinel contains a small amount of melt during firing, and if it is rapidly cooled, the glass phase of the mineral may be mixed, and a small amount of unreacted magnesia and alumina may remain. However, the coefficient of thermal expansion of these mixed minerals is Alumina = 80X107 Magnesia = 140X10-', Spinel = 90XIO
-' Due to linear reversible expansion and contraction due to rapid cooling, these mixed minerals separate from each other and become individual minerals. Therefore, high-purity spinel can be obtained at a high yield by a selective method such as the above-mentioned zirconia production.

The above minerals have a specific gravity of 3.5, magnesha = 5.4, alumina = 3.9, and Dallas phase = 4.0.
Since the difference in specific gravity is not large, the specific gravity is disadvantageous.

Therefore, by flotation, only the spinel is suspended to produce a high-purity concentrate. In this case, since spinel can be flotated with any of the ten ion collectors, only spinel is flotated with nononic acid and higher fatty acids.

After sorting, the particles are finely pulverized to submicron size, a large external pressure is applied to the surface of the spinel particles, and the remaining crystal lattice distortion is removed by rapid cooling.The particles are then treated with mineral acid to remove any impurities, washed with water, and dried. High-purity ultra-fine powder spinel product.

(MgO: Cr2O3 weight ratio 58.5% + 41.5%), forsterite (
2MgO: S i O, weight ratio 57.2%: 42.8
%), mullite (3Al, o, = 28io2 weight ratio 7
1.8%: 28.2%), cordierite (2Mg
O:2AIiOi:5SiOa Weight ratio 13.8%
:34.9%:51.3%), Magne titanate: T
All high-grade refractory ceramics such as IO, weight ratio 49.5%: 50.5%) can be synthesized using spinel synthesis using the equilibrium phase diagram of the component system. - Achieve thousand-method production.

Minerals produced through such synthesis are similarly subjected to high-temperature treatment, so it goes without saying that spinel is a stable product that does not undergo contraction after expansion.

Regarding patent claim (2), zirconia is produced by a completely different method than patent claim (1), which further features embodiments thereof, but method (1) produces high-temperature stable body-centered cubic crystals. zirconia cannot be obtained.

Therefore, fine zirconia powder was prepared by J according to the manufacturing method (1),
R, Hellman's Zr02-Cao and H,G.

5cott (100% zirconia seen in this binary equilibrium state diagram 1975 of D Z r Oa Y20s
In the composition range of 2,350-2,670℃, that is, within the cubic crystal region of zirconia, instantaneous high-temperature heat irradiation was performed at 2,500℃ to avoid unnecessary loss of heating energy, and then the product was placed in running water. After rapid cooling by injection, body-centered cubic microscopic zirconia is obtained using the method [1]. The obtained zirconia is stable at high temperatures.

As is clear from the invention detailed above, the present invention has many excellent effects as follows.

(1) The present invention does not use expensive electricity with extremely low thermal efficiency as an energy source for production, but uses inexpensive fuel with high efficiency, and although it has the same quality as conventional electrical products, it is semi-stable at room temperature. Since the molten product can be supplied industrially in large quantities at low cost, it has a tremendous effect on production costs.

(2) Conventionally, it was impossible to obtain zirconia in the form of a cubic crystal without adding this stabilizer, so impurities such as karja, magnesha, and ittoriya were added to reduce the amount of zirconia added. Since it is necessary to add 5% or more of zirconia, the purity of zirconia must be lowered.

Zirconia 100% square crystal has a fire resistance of 2700' and when additives are added zirconia 92-95
%, and therefore the upper limit of the fire resistance is 2500', and a difference of 200 °C in this high temperature range has a tremendous effect on its use as a highly refractory fine ceramic material.

1) In the attached document submitted by Kyoto on February 17th, (1. Name of invention column) ``Ceramic industry: Production of raw materials for fine ceramics and new ceramics with a mineralogically stable mineral phase''``Method'' has been corrected to ``Method for producing fine ceramic raw materials with a mineral phase that is mineralogically stable.''

post code Method" I will correct it.

Below Up Contents of correction As per attached attachment

Claims (2)

[Claims] (1) Irradiate fine powder of refractory raw material mineral with instantaneous high temperature flame,
After producing a semi-molten fired product, this material is injected into running water directly under the flame and instantly quenched.The mineral phase and physical properties of the mineral, which were stable in the high temperature range, are also preserved in the normal temperature range. A method for producing high-temperature refractory ceramic raw materials characterized by maintaining the material in the state of ■. (2) Zirconia (ZrO_
2) For stabilization at room temperature, we use 100% body-centered cubic zirconia that is stable at room temperature without adding conventional stabilizers.
How to produce.