CN1772695A - Prepn of microcrystalline alumina ceramic grain - Google Patents

Abstract

A method for preparing microcrystalline alumina ceramic particles, which is characterized in that the preparation process is to use ultra-fine aluminum hydroxide as a starting material to prepare α-alumina, and then mix it with aluminum hydroxide and pseudoboehmite Grinding, preparing into a suspension, preparing into a gel, drying and crushing, sintering at a temperature of 1250°C to 1650°C, crushing and sieving to obtain microcrystalline alumina ceramic particles. Compared with traditional alumina-based abrasive grains such as white corundum and brown corundum, the alumina ceramic particles prepared by the method of the present invention have the advantages of high hardness, good toughness, good wear resistance, etc., and the primary crystal is between 200nm and 2μm . The durability of abrasive tools prepared from this abrasive material is greatly improved.

Description

A kind of preparation method of microcrystalline alumina ceramic particle

technical field

The invention discloses a preparation method of microcrystalline alumina ceramic particles, which relates to a preparation method of alumina ceramic abrasive grains for grinding materials, and is especially suitable for preparing high wear resistance alumina ceramic grinding products.

Background technique

α-Al ₂ O ₃ (commonly known as corundum) is the most stable phase among all aluminas, belonging to the A2B3 type compound, trigonal crystal system, with high melting point (up to 2050°C), high hardness (Mohs hardness up to 9), and structure Compact (primary crystal true density up to 4.01g.cm ^-3 ), high mechanical strength, stable chemical properties, and good resistance to acid and alkali.

Based on the characteristics of high hardness and good wear resistance _of α- _Al2O3 , it is widely used to manufacture various grinding materials, such as fused corundum, including white corundum, brown corundum, high alumina corundum, etc. The production of corundum generally undergoes a melting process. Due to the melting process, the primary crystals of alumina in corundum are relatively large, generally reaching hundreds of microns or even several millimeters, so corundum abrasives have the characteristics of high hardness. , High brittleness generally manifests as transgranular fracture, so it has a great negative impact on the performance of abrasive tools, mainly manifested in low toughness of abrasive grains and low durability of abrasive tools. Although the hardness of sintered corundum is also very high, but because the processing process is a powder sintering process, the microstructure of the prepared material is a material with no sharp edges and corners, so the cutting force is not strong, so it can only be used as a polishing material. , and cannot be used as an abrasive that requires high cutting force.

Contents of the invention

The purpose of the present invention is to provide a method for preparing microcrystalline alumina ceramic particles with greatly improved toughness and strong cutting force of the prepared abrasive tool for the deficiency of corundum abrasive grains in toughness.

The purpose of the present invention is achieved through the following technical solutions:

A method for preparing microcrystalline alumina ceramic particles, characterized in that the preparation process comprises:

a. Preparation of ultrafine α-alumina powder

Add magnesium oxide or aluminum fluoride with a weight ratio of 0.2%-0.5% to aluminum hydroxide, calcinate at a temperature of 1100°C-1300°C to produce α-alumina, and pulverize until D ₅₀ is less than 1.0μm;

b, preparation of aluminum hydroxide and pseudo-boehmite mixture

Mixing and grinding aluminum hydroxide and pseudoboehmite with a molar ratio of aluminum of 0.1 to 5 until the D50 is less than 1.5 μm;

c. Preparation of suspension

According to the molar ratio of the aluminum in the α-alumina to the aluminum in the mixture in the step b of 0.05-0.8, add the α-alumina micropowder to the mixture prepared in the step b, and add water to prepare a suspension with a solid weight content of 20%-50%. liquid;

d. Preparation of gel particles

To the suspension prepared by c, add 2% to 35% of the total aluminum oxide weight in the suspension to one or more mixtures selected from magnesium oxide, iron oxide, calcium oxide, and silicon oxide; Heat the solution to 60-90°C, control the pH value to 1-3, stir to form a gel; dry the gel in a drying oven and break it into 0.5-1.5mm particles;

e. Preparation of microcrystalline alumina ceramic particles

The gel particles are sintered at a temperature of 1250 DEG C to 1650 DEG C for 2 to 6 hours; they are crushed according to the requirements of grinding materials to prepare microcrystalline alumina ceramic particles.

The method of the present invention uses superfine aluminum hydroxide and pseudo-boehmite as basic raw materials, and adds oxides such as magnesium oxide, iron oxide, calcium oxide, and silicon oxide that can form dense ceramic bodies with aluminum oxide at high temperatures, and passes through the sol —Geling, drying, crushing and other processes can prepare alumina ceramic-based abrasives with superior performance. The preparation process of this kind of abrasive can ensure the uniformity of various chemical components in the abrasive grains due to the sol-gel process. Since the abrasive grains are sintered by a large number of tiny primary crystals, they show a strong cutting effect on the macroscopic scale. At the same time, the toughness of abrasive grains is greatly improved, so the durability of abrasive tools prepared based on the abrasive prepared by this process is greatly improved. Compared with corundum abrasives, the toughness of the prepared alumina ceramic matrix has the advantages of good toughness, good durability of abrasive tools and the like.

specific implementation plan

A method for preparing microcrystalline alumina ceramic particles, which is characterized in that the preparation process is to use aluminum hydroxide as a starting material, add magnesium oxide or aluminum fluoride as an additive to promote phase transition and inhibit crystal growth, and prepare α - Alumina and the mixed grinding of ultrafine aluminum hydroxide and pseudo-boehmite, adding water to the ground mixture to prepare a suspension, controlling the total solid content in the suspension to be 20% to 50%, and then Add one or more of magnesium oxide, iron oxide, calcium oxide, and silicon oxide to the suspension, which can form a dense ceramic sintered body with aluminum oxide at high temperature. The additive can be added in the form of solid, or Corresponding salts can be added. After sintering at high temperature, the salts are transformed into corresponding oxides. The weight of added oxides accounts for 2% to 35% of the total solid content in the suspension, and inorganic acid is added to the suspension. And heating to prepare a gel body, after drying and crushing the gel body, sintering at a temperature of 1250°C to 1650°C, the sintered particles are crushed and sieved to obtain raw materials for making abrasive tools. The steps are: a. Preparation of superfine α-alumina powder: adding magnesium oxide or aluminum fluoride with a weight ratio of 0.2%-0.5% to aluminum hydroxide, and calcining at a temperature of 1100°C to 1300°C to produce α-alumina powder. - Alumina, pulverized until D ₅₀ is less than 1.0 μm; b. Preparation of aluminum hydroxide and pseudo-boehmite mixture: mixing and grinding aluminum hydroxide and pseudo-boehmite with a molar ratio of aluminum of 0.1 to 5 to D ₅₀ Less than 1.5 μm; c. Preparation of suspension: according to the molar ratio of aluminum in α-alumina and aluminum in the mixture in step b of 0.05 to 0.8, add α-alumina micropowder to the mixture prepared in step b, and add water to prepare a solid A suspension with a weight content of 20% to 50%; d, preparation of gel particles: adding 2% to 35% of the total aluminum oxide weight in the suspension to the suspension prepared by c, selected from magnesium oxide, oxide A mixture of one or more of iron, calcium oxide, and silicon oxide; then heat the suspension to 60-90°C, control the pH value to 1-3, and stir to form a gel; dry the gel in a drying oven Finally, it is broken into particles of 0.5-1.5 mm; e. Preparation of microcrystalline alumina ceramic particles: sintering the gel particles at a temperature of 1250 ° C to 1650 ° C for 2 to 6 hours; breaking according to the requirements of the abrasive material to prepare microcrystalline Alumina ceramic particles.

Compared with traditional alumina-based abrasive grains such as white corundum and brown corundum, the alumina ceramic particles prepared by the present invention have the advantages of high hardness, good toughness, good wear resistance, etc., and the primary crystals are between 200nm and 2μm. The durability of abrasive tools prepared from this abrasive material is greatly improved.

Example 1

First, add 500 grams of aluminum hydroxide with D50<1 μm to 1 gram of magnesium oxide and 2 grams of aluminum fluoride, calcinate at 1200 ° C for 2 hours, and crush the prepared α-alumina into fine powder with D50<1 μm, and take α-alumina 30 grams of aluminum micropowder, 100 grams of superfine superfine aluminum hydroxide micropowder, 300 grams of pseudoboehmite, grind for 12 hours in a small ball mill in the laboratory, add 25 grams of calcium oxide and 45 grams of silicon oxide to the ground material. gram, 30 grams of magnesium oxide, and 1000ml of water are prepared into a suspension, stirred and added dropwise to the suspension with hydrochloric acid until the pH value is 1 to obtain a gel, and the gel is placed in a laboratory drying oven at 90°C Drying, the dried gel is crushed into particles smaller than 1.0mm in a jaw crusher, and the crushed particles are calcined in a muffle furnace at 1400°C for 2 hours to obtain a ceramic sintered body, and the ceramic sintered body is crushed to obtain a finished alumina ceramic particles.

Example 2

First, add 500 grams of aluminum hydroxide with DS0<1 μm to 1 gram of magnesium oxide and 2 grams of aluminum fluoride, calcinate at 1100°C for 2.5 hours, and crush the prepared α-alumina into fine powder with D50<1 μm, ultrafine and ultrafine 100 grams of aluminum hydroxide micropowder and 300 grams of pseudo-boehmite were ground for 12 hours in a small ball mill in the laboratory, and 500 ml of water and 45 grams of silicon oxide were added to the ground material to prepare a suspension to obtain a uniform suspension solution, add 70ml of 1g.ml ^-1 calcium nitrate solution, 100ml of 1g.ml ^-1 magnesium nitrate solution to the suspension, add hydrochloric acid dropwise until the pH value is 2, and heat to obtain a gel. Dry in a drying oven at 90°C, and the dried gel is crushed into particles smaller than 0.5mm in a jaw crusher, and the crushed particles are calcined in a muffle furnace at 1250°C for 4 hours to obtain a ceramic sintered body, which is crushed to obtain Finished alumina ceramic particles.

Example 3

Get 50 grams of α-alumina micropowder prepared in Example 1, 80 grams of superfine superfine aluminum hydroxide micropowder, 45 grams of superfine calcium oxide, 55 grams of superfine silicon oxide, 40 grams of magnesium oxide, pseudoboehmite 350 grams, 500 grams of water, prepared into a suspension, grinded for 12 hours with a small ball mill in the laboratory, to obtain a uniformly mixed suspension, add 15% dilute hydrochloric acid to the suspension until the pH value is 3, and heat to obtain a condensed Colloid, the gel is dried in a laboratory drying oven at 90°C, the dried gel is crushed into particles smaller than 1.5mm in a jaw crusher, and the crushed particles are calcined in a muffle furnace at 1650°C for 2 Hours, a ceramic sintered body is obtained, and the ceramic sintered body is broken into different particle sizes to obtain finished alumina ceramic particles.

Example 4

First, add 500 grams of aluminum hydroxide with D50<1 μm to 1 gram of magnesium oxide and 2 grams of aluminum fluoride, calcinate at 1300 ° C for 2 hours, and crush the prepared α-alumina into fine powder with D50<1 μm, and take the prepared 30 grams of α-alumina micropowder, 60 grams of ultrafine superfine aluminum hydroxide micropowder, 45 grams of calcium chloride, 50 grams of magnesium nitrate, 400 grams of pseudoboehmite, 500 grams of water, prepared into a suspension, and prepared in the laboratory Grind in a small ball mill for 12 hours to obtain a uniformly mixed suspension, add nitric acid dropwise to the suspension until the pH value is 2, and heat to obtain a gel, which is stored in a laboratory drying oven at 90°C Drying, the dried gel is crushed into particles smaller than 1.0mm in a jaw crusher, and the crushed particles are calcined in a muffle furnace at 1350°C for 5 hours to obtain a ceramic sintered body, and the ceramic sintered body is crushed to obtain a finished alumina ceramic particles.

Example 4

Get 30 grams of α-alumina micropowder prepared in Example 1, 50 grams of superfine ultrafine aluminum hydroxide micropowder, 80 grams of magnesium nitrate, 400 grams of pseudoboehmite, and 500 grams of water, and prepare a suspension. Grind in a small ball mill for 12 hours to obtain a uniformly mixed suspension, add nitric acid dropwise to the suspension until the pH value is between 1 and 3, and heat to obtain a gel, which can be used in the laboratory Dry in a drying oven at 80°C, and the dried gel is crushed into particles smaller than 1.5mm in a jaw crusher, and the crushed particles are calcined in a muffle furnace at 1250°C for 6 hours to obtain a ceramic sintered body, and the ceramic sintered body is broken The finished alumina ceramic particles are obtained.

Example 5

Get 30 grams of α-alumina micropowder prepared in Example 1, 50 grams of superfine superfine aluminum hydroxide micropowder, 80 grams of calcium chloride, 400 grams of pseudoboehmite, 500 grams of water, be mixed with suspension, in Grind in a small ball mill for 12 hours in the laboratory to obtain a well-mixed suspension, add nitric acid dropwise to the suspension until the pH value is between 2-3, and heat to obtain a sol system, and use the gel in the laboratory Dry in a drying oven at 80°C, and the dried gel is crushed into particles smaller than 0.5mm in a jaw crusher, and the crushed particles are calcined in a muffle furnace at 1250°C for 5 hours to obtain a ceramic sintered body, and the ceramic sintered body is broken into alumina ceramic particles.

Claims (2)

1. A preparation method of microcrystalline alumina ceramic particles, characterized in that its preparation process comprises: a. Preparation of ultrafine α-alumina powder Add magnesium oxide or aluminum fluoride with a weight ratio of 0.2%-0.5% to aluminum hydroxide, calcinate at a temperature of 1100°C-1300°C to produce α-alumina, and pulverize until D ₅₀ is less than 1.0μm; b, preparation of aluminum hydroxide and pseudo-boehmite mixture Mixing and grinding aluminum hydroxide and pseudoboehmite with a molar ratio of aluminum of 0.1 to 5 until the D50 is less than 1.5 μm; c. Preparation of suspension According to the molar ratio of the aluminum in the α-alumina and the aluminum in the mixture of the step b being 0.05-0.8, the α-alumina fine powder is added to the mixture prepared in the step b, and water is added so that the solid weight content is 20%-50%. suspension; d. Preparation of gel particles Add one or more oxygen compounds selected from magnesia, iron oxide, calcium oxide and silicon oxide, accounting for 2% to 35% of the total aluminum oxide weight in the suspension, to the suspension prepared by c; heating Bring the suspension to 60-90°C, control the pH value to 1-3, stir to form a gel; dry the gel in a drying oven and break it into 0.5-1.5mm particles; e. Preparation of microcrystalline alumina ceramic particles The gel particles are sintered at a temperature of 1250 DEG C to 1650 DEG C for 2 to 6 hours; they are crushed according to the requirements of grinding materials to prepare microcrystalline alumina ceramic particles. 2. The preparation method of a kind of microcrystalline alumina ceramic particles according to claim 1, characterized in that the aluminum hydroxide used is superfine aluminum hydroxide.