Abstract
Ultra-large zirconia toughened alumina (ZTA, mass ratio of Al2O3 and ZrO2 is 78:22) ceramics with eccentric circle shape were successfully sintered by microwave sintering with a multi-mode cavity at 2.45 GHz. The dimension of ZTA ceramics (green body) is 165 mm (outer diameter) × 25 mm (thickness). The optimized sintering temperature of microwave sintering is about 1500 °C for 30 min, and the total sintering time is about 4 h which is much shorter than that of conventional sintering. An auxiliary-heating insulation device was designed based on the principle of local caloric compensation to guarantee the intact sintered samples. With the increasing of sintering temperature, more and more microwave energy is absorbed within the entire sample, volumetric densification performs, and phases shift from m-ZrO2 phase to t-ZrO2 phase and cause Al2O3 grain growth.
Highlights
Zirconia toughened alumina (ZTA) ceramics are considered as promising structural materials for their high toughness, hardness, wear resistance, high temperature anticorrosion, and chemical stability [1]
The mass distribution of ZTA ceramics is asymmetrical for its eccentric ring structure; in the case of uniform distribution of silicon carbide rods, the large mass part absorbed microwave intensely causing local heat gather, which may produce great thermal stress in the process of heat conduction, cause structure crack of ZTA ceramics
It can be seen that the peaks of alumina constantly are enhanced with the increasing of sintering temperature, which indicates the crystallinity of ZTA ceramics increases gradually, consistent with the SEM results from Fig. 8, and proves that microwave sintering can promote the grain growth of alumina
Summary
Zirconia toughened alumina (ZTA) ceramics are considered as promising structural materials for their high toughness, hardness, wear resistance, high temperature anticorrosion, and chemical stability [1]. These unique properties of ZTA ceramics lead to many industrial applications including cutting tools, wear parts [2], and seal valves. As one kind of sealing part, commercially available large size ZTA ceramics with eccentric circle shape are prepared. Only one large size sheet of kaolin with complex shape was successfully sintered in a microwave multi-mode cavity [10]. The explorations of microwave sintering process on special-shaped and large size ZTA ceramics are still nonexistent. Ultra-large industrial ZTA ceramics with eccentric circle shape are sintered (a) Green body
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