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What are the conventional sintering methods for alumina ceramics? Conventional sintering methods cannot meet the requirements for preparing transparent alumina ceramics. Commonly used sintering methods for preparing transparent ceramics include: a) atmosphere and vacuum sintering, b) hot isostatic pressing sintering, and c) electric discharge plasma sintering.

What are the conventional sintering methods for alumina ceramics?

1. Atmosphere and vacuum sintering

Alumina ceramics prepared by atmospheric pressure sintering usually have 1-3% residual porosity. However, sintering in a vacuum or atmosphere can generate a large number of oxygen vacancies in the alumina blank, accelerate the diffusion of O2-, and speed up the densification rate of the blank, which makes it easier to remove residual porosity.

Alumina ceramic sintering process flow, what are the alumina ceramic sintering methods?

2. Hot isostatic pressing sintering

Hot isostatic pressing (HIP) is a process technology that integrates high temperature and high pressure, with heating temperatures reaching 2000℃. Using a high-pressure inert gas or nitrogen in a closed container as the pressure transmission medium, the working pressure can reach over 200MPa. Under the combined action of high temperature and high pressure, closed gas vents that are difficult to eliminate under normal pressure sintering can be eliminated, allowing the production of highly transparent submicron-sized alumina ceramics. Due to the fine grain size of the transparent alumina ceramics prepared using this method, the ceramics exhibit excellent mechanical properties.

3. Discharge plasma sintering

Spark plasma sintering (SPS) involves loading raw material powder into a mold made of materials such as graphite, and applying specific sintering power and pressing pressure to the raw material powder using upper and lower punches and energized electrodes. The sintering process is completed through spark activation, thermoplastic deformation, and cooling. Due to its ability to sinter rapidly and achieve densification of fine ceramic structures at relatively low temperatures, SPS has been widely used in recent years to prepare transparent alumina ceramics.