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How to achieve hot pressing and sintering of magnesium oxide ceramics without cracking

Preparation of magnesium oxide, in order to promote sintering as well as can make the grain grow a little, and at the same time in order to reduce the preparation of hydration tendency, can add some additives, such as TiO2, Al2O3, V2O5, etc.. If you require a high purity of magnesium oxide ceramics, you can not use the method of adding additives to promote sintering and grain growth, but the method of activation sintering, that is, magnesium hydroxide calcined at the appropriate temperature, to get a lot of lattice defects of active magnesium oxide, used to manufacture sintered magnesium oxide ceramics.

Magnesium oxide chemically active, easily soluble in acid, hydration capacity, so the manufacturing process of magnesium oxide ceramics must consider this physical properties of raw materials. In order to reduce the activity of magnesium oxide, should be pre-fired to 1100 ~ 1300 ℃, grinding raw materials with the grinding liner and grinding ball are made of porcelain materials, can not use steel balls. The use of dry grinding to prevent hydration, the best use of vibration mill fine grinding, can get more junction particles. Forming method can be used semi-dry pressing method, slurry method, hot die-casting method and hot pressing method.

Most of the magnesium oxide ceramics are produced by slurry method. However, the process is more complicated because magnesium oxide is easily hydrated. In the preparation of slurry, in order not to make magnesium oxide and water contact, need to use ethanol and other organic body as suspension medium.

In order to improve the performance of the slurry, the pH can be adjusted so that the pH value of 7 ~ 8. After demoulding, the blank is dried at a temperature of 70 ℃, in order to make the moisture in the blank quickly excluded, the wet air should be removed as soon as possible.

The ceramics are sintered at a temperature of 1250°C and then packed into a corundum porcelain saggers at a temperature of 1750~1800°C for 2h.

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