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Additive for magnesium aluminate spinel sintering and application method

A magnesia-aluminum spinel and additive technology, which is applied in the field of powder metallurgy and can solve the problems of ungrowth and development of magnesia-aluminum spinel grains, excessive growth of magnesia-aluminum spinel grains, uneven distribution of the second phase and the like , to achieve the effect of fine particles, short sintering time and easy operation

Inactive Publication Date: 2016-07-20
CENT SOUTH UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Previously, the method of adding sintering aids was mainly to directly add oxides, but directly adding sintering aids in the form of oxides would easily lead to uneven mixing of oxide powders in the magnesium aluminum spinel powder, This in turn leads to the formation of inhomogeneous phases in various microscopic regions
That is, some areas are excessive, and after sintering, they are in an over-burned state, and the magnesia-aluminum spinel grains grow excessively; at the same time, some areas are missing sintering aids, and after sintering, they are in an under-fired state, and the magnesia-alumina spinel grains do not grow. or underdeveloped
In addition, the composition of the sintering aid deviates from the designed low-eutectic composition, resulting in uneven distribution of the second phase, forming a variety of second phases, and greatly reducing thermal conductivity

Method used

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  • Additive for magnesium aluminate spinel sintering and application method
  • Additive for magnesium aluminate spinel sintering and application method

Examples

Experimental program
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Effect test

Embodiment 1

[0026] Scandium chloride (according to 1wt.%Sc 2 o 3 ) into deionized water until completely dissolved. Then 99 wt.% magnesium aluminum spinel was added to the above solution. The pH of the above water-based solution was adjusted to 9.5 with ammonia water, dried at 120° C. for 24 hours, and then calcined at 650° C. for 2 hours. The above-mentioned calcined powder was pressed into shape, and the magnesium-aluminum spar obtained by sintering at 1450° C. for 2 hours had a density of 90% and a bending strength of 150 MPa. Compared with direct compression molding of magnesium aluminum spinel powder without using additives, the density of magnesium aluminum crystal obtained under the same sintering conditions is 70%, and the bending strength is 75MPa.

Embodiment 2

[0028] Scandium nitrate (according to 2wt.%Sc 2 o 3 ) into deionized water until completely dissolved. Then 98 wt.% magnesium aluminum spinel was added to the above solution. The pH of the above water-based solution was adjusted to 10 with ammonia water, dried at 120° C. for 24 hours, and then calcined at 700° C. for 3 hours. The above-mentioned calcined powder was compacted and sintered at 1500° C. for 3 hours to obtain a magnesium-aluminum spar with a density of 92% and a bending strength of 160 MPa. Compared with direct compression molding of magnesium aluminum spinel powder without using additives, the density of magnesium aluminum crystal obtained under the same sintering conditions is 73%, and the bending strength is 83MPa.

Embodiment 3

[0030] Scandium sulfate (according to 4wt.%Sc 2 o 3 ) into deionized water until completely dissolved. Then 96 wt.% magnesium aluminum spinel was added to the above solution. The pH of the above water-based solution was adjusted to 10.5 with ammonia water, dried at 120° C. for 24 hours, and then calcined at 750° C. for 4 hours. The above-mentioned calcined powder was compacted and sintered at 1550° C. for 4 hours to obtain a magnesium-aluminum spar with a density of 95% and a bending strength of 180 MPa. Compared with direct compression molding of magnesium aluminum spinel powder without using additives, the density of magnesium aluminum crystal obtained under the same sintering conditions is 80%, and the bending strength is 95MPa.

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Abstract

The invention relates to an additive for magnesium aluminate spinel sintering and an application method.The main constituents of the additive are scandium salt, ammonia water and water.The application method of the additive comprises the following steps of 1, dissolving the scandium salt into the water; 2, adding magnesium aluminate spinel powder to a solution obtained in step 1; 3, adding the ammonia water to adjust pH of water-based slurry obtained in step 2 to be 9-11; 4, then conducting drying for 24 hours or longer in a drying oven at the temperature of 120 DEG C, and then conducting calcination for 1-6 hours at the temperature of 600-800 DEG C; 5, after compression molding conducted on the calcinated powder is completed, controlling the sintering temperature to be 1400-1600 DEG C, and controlling sintering time to be 1-6 hours.By means of the additive for magnesium aluminate spinel sintering, the sintering temperature can be lowered, sintering time can be shortened, sintering compactness can be improved, and a uniform microstructure can be formed easily.

Description

technical field [0001] The invention belongs to the technical field of powder metallurgy, and in particular relates to an additive for sintering magnesium-aluminum spinel and a use method thereof. Background technique [0002] Magnesium aluminum spinel has some excellent properties, for example, high melting point (2135°C), high mechanical strength, good chemical corrosion resistance, good thermal shock resistance, good electrical insulation, high relative density ( 3.58g·cm -3 ). Magnesium aluminum spinel is widely used in metallurgy, electrochemistry, chemistry and other fields. However, the sintering temperature of magnesium aluminum spinel is very high (>1900℃), which seriously restricts its application. In addition, the domestic technology for preparing high-performance (high thermal conductivity and high strength, etc.) magnesium-aluminum spinel has not formed a mature preparation process, especially the microstructure control process of magnesium-aluminum spinel...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/443C04B35/64
CPCC04B35/443C04B35/64
Inventor 吕晓军刘建华李劼胡凌云赖延清
Owner CENT SOUTH UNIV
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