ZTA ceramic toughening principle

1. The existence of zirconia grains can fix and strengthen the grain boundaries of alumina ceramics, thus weakening the effect of cracks.

2, zirconia elastic modulus and thermal expansion coefficient are different from alumina, because of the difference between their two properties, when zirconia filled in alumina grain boundary, zirconia grain will be subjected to the radial compressive stress generated by alumina grain, so as to be tightly clamped, when the external force, cracks will be deflected, and then improve the fracture toughness of ceramics.

The data analysis shows that when the sintering temperature is lower than 1500℃, the density of the sintered body is relatively low, indicating that there may be a large number of pores in the ceramics. When the sintering temperature reaches 1500℃, the density is greatly increased, and even the density of pure alumina sintered body reaches more than 99%. However, the density of pure alumina sintered body decreases with increasing sintering temperature, while the density of alumina - zirconia sintered body with different proportions of zirconia increases further and is higher than that of pure alumina sintered body. According to the density variation trend of different proportions of alumina and zirconia sintered body, when A1/Zr=20, its density is the highest, reaching 99.4%, and the sample is basically completely dense. For pure alumina ceramics at 1600℃, the density has a small reduction, which is mainly because when the temperature continues to rise, the grain of the ceramic will grow abnormally, forming secondary recrystallization, resulting in some pores being wrapped into the grain interior, so that the density of the ceramic sample is reduced. At the same time, a small number of pores exist in the grain with a small size, and the pores can migrate in the grain, which leads to the porosity merger, resulting in the appearance of larger pores, and finally the density of the sample is slightly reduced.

In other words, the sintered zirconia toughened alumina ceramics at 1600℃ has good performance, and its fracture toughness can reach 7.6MPa•m1/2, which is nearly double that of pure alumina ceramics, and can be used in heavy wear and strong impact conditions such as mines, docks and ports.