Effect of magnesium oxide on the metallization of alumina ceramics

The metalization of alumina ceramics is mainly based on the activation MO-MN method. The activated MO-MN method is developed on the basis of sintering metal powder (traditional MO-MN) method.Some activators that can form glass phases during metallization such as: Al2O3, SIO2, MGO, CAO, BAO, porcelain powder, etc. to expand the adaptability of the original MO-MN formula.At present, most units adopt an improved MO-MN formula, mainly to add activation agents to the metallic formula, reduce the metalized temperature, and obtain a higher metallic seal strength.

The role of adding activists is mainly to promote the generation of high temperature liquid phase, that is, to reach the metalized temperature to make the activation agent into liquid phase, part of the effect of generating liquid phase with ceramic ingredients, part with oxidized metal powder generated liquid phases These two cases generally occur at the same time. When the liquid produced is the same, the metal powder and ceramic surface are infiltrated to form adhesion.

The activation agent in metalized formulas is used in three types: AL2O3, SIO2, and MGO. This formula has been put into production for more than two years. The production conditions in the early stage are good and the quality is relatively stable. This article focuses on solving outstanding problems in the process of metallization.

1. There is a problem after a metallic sintering

(1) Severe coverage problem.

(2) A large amount of covering the metal surface after sintering, and some covers were raised to fall off to produce dew porcelain or peeling.

2. Cause analysis and test

2.1, cover flower spots

The analysis believes that there are two main reasons for the creation of the cover of the cover: the proportion of the powder is inaccurate; the sintering process is changed, that is, the heating time and the temperature of the heat preservation and the humid hydrogen temperature are prolonged. Re -equip it with powder and paste, and sintering without changing the existing sintering process. As a result, the cover of the cover still exists. Back to the sintering process sintering, the cover of the cover is reduced, but it still exists.

Select a sample to analyze the spectrum of its cover flower spots, and the analysis conclusion is: FE, NA elements containing the amount of trace except the formula element of the formula. According to analysis, it is believed that the FE and NA elements of the amount of marks are not the cause of the cover of the cover.

Only consider the changes in magnesium oxide, and do two comparison tests: choose magnesium oxide (purity as analyzing pure) powder, prepare metalized powder for metalization. Remove magnesium oxide in the original formula for metalization. The conclusion is that the cover of the cover with magnesium oxide sintering still exists after sintering. It can be concluded that the direct cause of the cover of the cover is magnesium oxide.

2.2, the cover is raised, exposed, peeling

After experimental verification, the main cause of the raisedness is: ① the powder is moisture, and the bonding agent and the powder are difficult to mix and uniformly; Magnesium oxide oxide is easy to connect, resulting in uneven mixed powder, raised or peeling after sintering.

3. Results analysis and solution

Magnesium oxide is the direct cause of the creation of the cover of the cover: ① The magnesium oxide is not fully mixed during the preparation of the paste, causing the magnesium to disperse unevenly during the sintering process; Under the action of hydrogen, increase the temperature or preservation time, which will form more glass phases with smaller viscosity, spread to the surface of the metallic layer, and form cover spots.

Solution: Extend the mixed grinding time of magnesium oxide, shorten metal sintering insulation time, and reduce the temperature of humidity and hydrogen.

The main reason for the raised magnesium oxide is because magnesium oxide has a long time and is not a vacuum packaging. It absorbs water and CO2 in the air to generate alkaline magnesium carbonate, forming hard blocks, which is difficult to grind and mix. Then the hydration ability of magnesium oxide is strong, and it increases with the decrease of particle size, and then the mass of the formation or the formation of the formula is changed to change the formula and proportion of the formula. In the climate, it is possible to make the metal ointment frozen.

Solution: ① Reduce the amount of one -time ordering of magnesium oxide and shorten the storage cycle; ② Use water -free ethanol wet abrasive abrasive oxide, SIO2, magnesium oxide mixed powder according to proportion, dry after 360 measuring Differentiated; ③ Dry the metallic powder before preparing the paste to prevent the reunion of the paste without being easy to mix and the paste frozen glue.

4. Summary

Magnesium oxide, as a common activated agent for medium temperature metal, can effectively reduce the metal sintering temperature, but there is the following problems in the metalization process:

(1) Magnesium oxide and moisture absorption and deterioration, resulting in inaccurate metallic formula ratios, difficulty grinding in blocks, and not suitable for preservation after grinding.

(2) The prepared metal powder is also prone to moisture absorption, which makes it difficult for the paste to mix. There are many quality problems with the metalized cover of silk or hand -painted metal, such as raised, dew porcelain peeling, etc.

(3) Magnesium oxide, as a activator, has poor adaptability to craftsmanship, high requirements for process conditions, and prone to covering the problem of cover, which affects the combination of metalized layers and nickel layers strength.

(4) Metalized powder preparation process is more complicated, which increases the amount of powder production and process equipment and containers, and the quality of metalized powder is unstable, and there are hidden quality hazards.

In short, the amount of magnesium oxide should be reduced during the metalization process. If it is used, it is advisable to reduce the temperature of the dampness and shortening the thermal insulation time of the high -temperature sintering area, and control the stable metalization quality of the powder, cream and sintering process.

High Purity Magnesium Oxide
High Purity Magnesium Oxide

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