Method for preparing alpha-alumina particles with nanometers size

The present invention belongs to the inorganic non-metallic material preparation technologies, relates to nanometer α-Al₂ O₃ method for the preparation of granules.

Ultra-fine α-Al₂ O₃ particles on the electronics industry is the production of the integrated circuit substrate, transparent ceramic tube, the phosphor powder, recording (phase) tape, laser material and high-performance ceramic structure of the important chemical raw materials. α-Al₂ O₃ particle size directly affect the above-mentioned product quality. According to the general law, the smaller the particle size, more is favorable to the preparation of the product of various high-performance indicators, therefore, it is very great importance to ultra-fine α-Al₂ O₃ the study of granule preparation. At present, only preparing submicron ultra-fine α-Al₂ O₃ Patent or coverage of the particles, and nano-scale ultrafine α-Al₂ O₃ particles rarely reported.

Generally speaking, the particle diameter of 0.05-1.00 the particles between   m called submicron ultra-fine particles, and the diameter is smaller than 50 nm particles referred to as nano-scale ultrafine (abbreviated as nano-scale) particles.

Commercial production of submicron α-Al₂ O₃ particle is mainly technology has carboylate ammonium heat hydrolysis, hydrolysis of compound decomposition, roasting method, improved Bayer process, such as inorganic polymer-type sol. Wherein the first three more commonly used. French Patent 2486058 reports the most new carboylate ammonium heat the hydrolysis process, its preparation process is the diameter is about 1 mm to carboylate grain located in the cone rotary steel enamel tire-dehydrating in, heating the dehydrated product is put in the round furnace, burning, in the 1250 under the temperature of about [...] formed α-Al₂ O₃ particle, its dimension is about 0.1-0.5 the  m. But carboylate ammonium extension into Al₂ O₃ heat will appear in the course of dissolving phenomenon, dewatering the volume expansion can not be high, and thermal decomposition producing pollution of the environment in SO₂ gas and the like. In order to solve the problems the above-mentioned method, the proposed replacement SO²₄but root form another kind of aluminum salt, in other words aluminum ammonium law carbonate. The method is a certain amount of ammonium bicarbonate solution is added to the aluminum sulfate in aqueous ammonium solution, react immediately between the two, forming NH₄ AlO (OH) HCO₃ and a small amount of Al (OH)₃ precipitate, the precipitate after washing by several times, to remove residual SO²₄ the, dry and 1200 the roasting [...] into α-Al₂ O₃ particle, its dimension is about 0.2-1.0 the between   m. This method, however, the ultimate α-Al₂ O₃ performance indicators and synthetic process parameters (temperature, concentration, PH value, and so on) and to precipitate is dried (spray drying, adding the surface active agent directly drying, freeze-drying) there is a close relationship between, is not easy to control this method therefore, relates to a large amount of deionized water and a large number of equipment. Baking process decomposition, hydrolysis of compound is butanol [...] the isopropanol solution of aluminum produced after the addition of water in the hydrolysis, the hydrolysis product of the polycondensation process, to achieve the purpose of controlling polymerization product Al₂ O₃ · 3H₂ O particle size, will Al₂ O₃ · 3H₂ O the particles pass through the 1200-1350 the formed after roasting [...] α-Al₂ O₃ particle size is 20 nm -1000 nm between. Although this method can prepare the cashiering m levels of superfine α-Al₂ O₃ particles, but this method very strict chemical reaction control requirements, in addition, this method requires expensive price and not easy to be stored decomposition compound.

The above-mentioned introducing preparation α-Al₂ O₃ particle method is mainly used for preparing the submicron level. However, at present, the preparation by nano-particles of nano ceramic study shows that the, general nano ceramic and micron-sized ceramic has obvious distinction substance, is mainly shown in nano-ceramic having a high-strength, high-toughness, low sintering temperature, high-density and nano-ceramic unique superplastic. Its final one performance can make general ceramic processing, according to the metal material for forging, extrusion, bending processing mode, without the conventional the cumbersome grinding can be prepared the ceramic parts precision dimension. In studies of the ceramic is very attractive. For Al₂ O₃ based ceramic to have the above-mentioned superior characteristics, must have nanometer α-Al₂ O₃ particles as a premise.

The purpose of this invention aimed at the development of a simple preparation, process is easy to control, high yield, using conventional aluminum salt as the raw material, and the preparation of the nano-scale α-Al₂ O₃ the method of the particle.

The technical idea of the present invention:

The low price of aluminum salt forming an aqueous solution, then add a certain amount of another kind of chemical substance. In the solution and form a water-insoluble the infinitesimal particles containing Al (i.e. sol). Provide the polymer or polymer monomer in, then adding a cross-linking agent or initiator, the organic polymer or polymer monomer produces polymerization reaction to form a high-molecular-weight polymer, at the same time make the sol into a gel system system. This reaction process but high polymer in the material known as sol-gel process. In this process the solid phase particles in the organic matter is always evenly distributed in the reaction system. Particles and between the particles of organic high polymer gel network is spaced apart from each other, this will assumes the kind solid organic high polymer gel can be conveniently placed in different temperature processing, after the 1200 after roasting temperature of about [...] , organic decomposition, α-Al₂ O₃ particles thus formed. Although in forming α-Al₂ O₃ in phase process Al₂ O₃ particles will grow up, but since the initial particle containing Al₂ O₃ amount little, scale and small, it follows that the final forming α-Al₂ O₃ particle size is generally less than 50 nm, in other words m levels of ultrafine particles.

According to the above-mentioned ideas, the substance of the present invention:

1. Process flow such as shown in the Figure, the significance of the symbols in the Figure:

A-aluminum salt solution, 1-a certain chemical substance, B-sol, 2-polymer or polymer monomer, C-sol, 3-cross-linking agent or initiator, D-high polymer gel, 4-govind 1150 the the [...] -1200 [...] , E-nanometer α-Al₂ O₃ particles.

2. In the process chemical raw materials:

Forming a solution of aluminum salt: ammonium aluminium sulphate or aluminum nitrate or aluminum chloride or basic aluminum acetate or aluminum sulfate, etc.;

Adding chemical substances: aqueous ammonium or ammonium bicarbonate or six times, such as methyl amine;

High polymer: polyvinyl alcohol or chitosan or polymethyl methacrylate;

High polymer monomer: α-hydroxy acrylic acid or methacrylic acid or acrylamide, etc.;

Cross-linking agent: glutaraldehyde or N-2 alkenyl-pyrrolidone or ethylene diamine or diethylene triamine or methylene bis acrylamide;

Initiator: peroxysalts toluene or azo d b harumi or hydrogen peroxide or peroxy ammonium sulphate or ammonium sulphate peroxysalts potassium sulfate, and the like.

3. The preparation method of this invention:

In 0.01-0.1M aluminum salt aqueous solution in the concentration, add a certain amount of ammonia (its concentration is containing NH₃ 25-1% (weight content), NH₃/Al₂ O₃ weight ratio of 0.01-1) or ammonium bicarbonate solution (its concentration is 1-0.01M, NH₄ HCO₃/Al₂ O₃ weight ratio 25-4) or six a amine solution (its concentration is 1-0.5M, (CH₂)₆ N₄/Al₂ O₃ weight ratio of 10-1), the temperature is 10-70 the reaction under [...] , aluminum-containing particles formed after the sol system, adding polymer or polymer monomer (an amount and Al₂ O₃ the weight ratio of 10-40), then adding a cross-linking agent (an amount of the polymer or polymer monomer in the weight ratio of 0.01-0.30) and initiator (an amount of the polymer or polymer monomer molar ratio of 0.1-0.05), the the 25-100 [...] carried out under temperature conditions after reaction high polymer sol-gel process, in a few seconds to several tens of hours can produce the high polymer gel, the gel in 100 the dry the [...] several minutes to several tens of hours later, is placed in the crucible 1100-1300 the heat treatment is carried out under [...] a few minutes to a few hours later, can be obtained by furnace cooling by the aluminum-containing particles formed by decomposition of α-Al₂ O₃ particle, its scale is in 10 nm -50 nm range.

Compared with the prior art having a remarkable effect of the present invention:

The low price of raw material, the operation is convenient, it is easy to control, high yield, without large-scale special equipment, and to use in the industry.