Reactive sintering method for preparing magnesia alumina spinel

A technology of magnesia-aluminum spinel and sintering method, which is applied in the field of reaction sintering for preparing magnesia-aluminum spinel, can solve the problems of short sintering time, high calcination temperature, uneven particles, etc., and achieves short holding time at high temperature and microstructure Uniform and simple preparation process

Inactive Publication Date: 2015-07-08
CENT SOUTH UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Due to the need for a two-step calcination process, the power consumption is high, resulting in high production costs
For this reason, some new sintering methods have been tried before to shorten the sintering time or lower the sintering temperature, such as microwave sintering, vacuum sintering, spark plasma sintering, etc. However, these sintering methods require some high-end equipment, so it is difficult to produce on a large scale application
Generally speaking, the shortcomings of these solid-phase methods are that impurities are easily introduced during the preparation process, the purity of the sintered product is low, the particles are uneven, and the shape is difficult to control. In addition, the calcination temperature is high and the production cost is high.
Therefore, the design of sintering temperature control degree will significantly affect the sintering performance and microstructure uniformity of ceramics.
If the sintering temperature is too low or the sintering time is too short, the reaction cannot occur or the reaction cannot be completed; if the temperature is too high or the time is too long, the resulting product particles are likely to be coarse, and too high a temperature may cause the raw materials to evaporate or the product to decompose

Method used

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  • Reactive sintering method for preparing magnesia alumina spinel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0026] Magnesium oxide with an impurity content of 4wt.% and alumina with an impurity content of 1wt.%, according to MgO:Al 2 O 3 The molar ratio is 1:1. The ball milled for 1 hour at a speed of 10r / min and a ball-to-battery ratio of 1:1. The powder obtained by ball milling is held at 50 MPa for 1 min, and the green body is molded at 120°C. Dry at temperature. Place the dried green body in a box-type resistance furnace, heat it up to a temperature of 1300°C at a heating rate of 5°C / min for 2 hours, and then heat it to a temperature of 1600°C at a heating rate of 5°C / min 0.1h, then at a cooling rate of 30°C / min, the temperature is reduced to 1350°C for 2 hours, and then cooled naturally to room temperature. The resulting magnesium aluminum spinel ceramic has a density of 93% and a bending strength of 150 MPa.

Embodiment 2

[0028] Magnesium raw material mixed with magnesium hydroxide and magnesium oxide with an impurity content of 3wt.%, and aluminum raw material mixed with aluminum carbonate and alumina with an impurity content of 2wt.%, according to MgO:Al 2 O 3 The molar ratio is 1:1, and the ball milled for 4 hours at a speed of 30r / min and a ball-to-battery ratio of 2:1. The powder obtained by ball milling is held at 100MPa for 5 minutes, and the green body is pressed at 120℃. Dry at temperature. Place the dried green body in a box-type resistance furnace, heat it up to a temperature of 1400°C at a heating rate of 8°C / min for 2 hours, and then heat it to a temperature of 1650°C at a heating rate of 8°C / min 0.5h, then at a cooling rate of 40℃ / min, the temperature is lowered to 1450℃ for 5h, and then cooled naturally to room temperature. The obtained magnesium aluminum spinel ceramic has a density of 96% and a bending strength of 180 MPa.

Embodiment 3

[0030] Magnesium raw material mixed with magnesium hydroxide and magnesium carbonate with an impurity content of 2wt.%, and aluminum raw material mixed with aluminum carbonate and aluminum hydroxide with an impurity content of 3wt.%, according to MgO:Al 2 O 3 The molar ratio is 1:1, and the ball milled for 8 hours at a speed of 60r / min and a ball-to-battery ratio of 3:1. The powder obtained by ball milling is held at 150MPa for 8min, and the green body is molded at 120℃. Dry at temperature. Place the dried green body in a box-type resistance furnace, heat it up to 1450°C at a heating rate of 10°C / min for 10 hours, and then heat it to a temperature of 1680°C at a heating rate of 10°C / min 0.8h, then at a cooling rate of 50℃ / min, the temperature is lowered to 1500℃ for 10h, and then cooled naturally to room temperature. The obtained magnesium aluminum spinel ceramic has a density of 98% and a bending strength of 200 MPa.

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Abstract

The invention discloses a reactive sintering method for preparing magnesia alumina spinel, which is characterized by comprising the following steps: heating a dry green compact to 1250-1550 DEG C in a resistance furnace at the rate of 4-16 DEG C / minute, and keeping the temperature for 0.5-16 hours; heating to 1550-1750 DEG C at the rate of 4-16 DEG C / minute, and keeping the temperature for not more than 1.5 hours; and cooling to 1300-1600 DEG C at the rate of 10-70 DEG C / minute, keeping the temperature for 0.5-16 hours, and naturally cooling to room temperature to obtain the uniform-microstructure high-density magnesia alumina spinel. The method is beneficial to lowering the sintering temperature and shortening the holding time at high temperature, thereby lowering the energy consumption. The method improves the microstructure of the magnesia alumina spinel ceramic material, and enhances the mechanical properties of the magnesia alumina spinel ceramic material. The method improves the melt permeation resistance and corrosion resistance of the magnesia alumina spinel.

Description

Technical field [0001] The invention belongs to the technical field of powder metallurgy, and specifically relates to a reaction sintering method for preparing magnesium aluminum spinel. Background technique [0002] MgAl 2 O 4 Spinel (MAS) has a face-centered cubic crystal structure, so MAS has some important properties, such as high melting point (2135°C), high mechanical strength, good chemical resistance, good thermal shock resistance, and good Electrical insulation, high relative density (3.58g·cm -3 ). MAS is widely used in metallurgy, electrochemistry, chemistry and other fields. However, pure natural Al-Mg spinel is very rare, and the Al-Mg spinel used in industry is synthesized by artificial synthesis. According to different production processes, it is divided into: sintered spinel and fused spinel. Since the electrofusion method is mainly an intermittent operation, the cooling of the pouring block causes the uneven microstructure, which is difficult to meet the indus...

Claims

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Application Information

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