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zirconia toughened alumina

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zirconia toughened alumina can improve fracture toughness of alumina ceramics prominent.

1、 Toughening method

1. Introduce the second phase.

2. Add alumina seed crystals. Because the addition of seed crystals can promote the anisotropic growth of grains, which will form sheet and columnar grains, similar to whiskers, which have the effects of crack displacement, grain extraction, and connection toughening on ceramics.

3. Forming defect distribution. By forming defect distribution during the synthesis process of powders or the preparation process of ceramics, the fracture toughness of alumina ceramics can be improved.

zirconia toughened alumina is a method of improving the fracture toughness of alumina by introducing a second phase. The zirconia toughened alumina (also known as ZTA ceramic) developed and produced by us involves adding a certain proportion of zirconia to the alumina α- The introduction of zirconia as the second phase into alumina crystals fills the grain boundaries of alumina, blocking the propagation of cracks and improving the fracture toughness of ceramics.

2、 Toughening principle

1. The presence of zirconia grains can fix and strengthen the grain boundaries of alumina ceramics, thereby reducing the impact of cracks.
2. The elastic modulus and thermal expansion coefficient of zirconia are different from that of alumina. Due to the differences in their two properties, when zirconia is filled at the grain boundary of alumina, the zirconia grains are subjected to radial compressive stress generated by the alumina grains, and are tightly clamped. When encountering external forces, cracks will deflect, thereby improving the fracture toughness of ceramics.

Data analysis shows that when the sintering temperature is below 1500 ℃, the density of the sintered body is relatively low, indicating that there may still be a large number of pores in the ceramics that have not been ruled out at this time. When the sintering temperature reaches 1500 ℃, there is a significant increase in its density, and even the density of pure alumina sintered body reaches over 99%. However, further increasing the sintering temperature results in a decrease in the density of pure alumina sintered body, while the density of alumina zirconia sintered body mixed with different proportions of zirconia further increases, which is higher than that of pure alumina sintered body. From the density variation trend of zirconia toughened alumina with different ratios, it can be seen that when Al/Zr=20, its density is the highest, reaching 99.4%, and the sample is basically completely dense at this time. For pure alumina ceramics, there was a slight decrease in density at 1600 ℃. This is mainly because as the temperature continues to rise, some of the ceramic grains will grow abnormally, forming secondary recrystallization, causing some pores to be wrapped inside the grains, thereby reducing the density of the ceramic sample. And at the same time, a small number of pores exist in the grains with small sizes, and pores can migrate within the grains, leading to the merging of pores and the appearance of larger pores, ultimately leading to a small decrease in the density of the sample.

That is to say, zirconia toughened alumina sintered at 1600 ℃ have good performance, with a fracture toughness of up to 7.6MPa • m1/2, which is nearly twice that of pure alumina ceramics. They can be used in heavy wear and strong impact conditions such as mines, docks, and ports.