Vacuum Sintering Furnaces for Ceramic molding

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In the era of new materials, advanced ceramics are one of the most important pillar industries in the field of ceramics and inorganic materials. Compared with metals and polymer materials, advanced ceramic materials have incomparable structural characteristics such as high hardness, high modulus, high temperature resistance, corrosion resistance, and excellent functional characteristics such as electrical insulation, light transmission, and wave transmission. Therefore, they are increasingly used in aerospace, information technology, biomedicine, and new energy fields, basically maintaining an annual growth rate of 7% to 10%.

The reason why advanced ceramics have such excellent characteristics is that compared with traditional ceramics, they use raw materials with higher purity and finer particle size and more complex preparation processes. With the continuous expansion of application fields, the requirements for the performance of advanced ceramics are also constantly increasing. To this end, researchers have continuously developed new technologies based on traditional preparation processes, specifically for improving the performance of special ceramics to promote their further development. Among these new technologies, molding and sintering technologies have achieved significant improvements and leaps due to the introduction of vacuum technology.

Application of vacuum sintering technology in ceramic sintering

Sintering is the most critical link in the preparation process of advanced ceramics. Its essence is the process of eliminating pores in the green body and completing densification. The sintering process has a direct impact on the grain size and pore content, which determines the final performance of advanced ceramic samples. Advanced ceramic preparation technology has developed at least, and there are many sintering methods. According to different factors such as pressure and sintering atmosphere, it can be divided into vacuum sintering, hot pressing sintering, spark plasma sintering, etc. In these sintering methods, vacuum technology plays an important role.

Vacuum sintering

During the sintering process, the influence of atmosphere is complex and important. Sintering atmosphere is generally divided into three types: oxidation, reduction and neutral. Generally speaking, reducing atmosphere promotes the detachment of anions from the crystal surface, increases the diffusion coefficient, and is conducive to sintering; while oxidizing atmosphere is conducive to the diffusion of cations. Since oxide sintering is mostly controlled by O² diffusion, reducing atmosphere (especially vacuum) is more suitable. Vacuum also promotes the discharge of gas inside the green body and accelerates densification, so that dense ceramics can be obtained by heating in a vacuum atmosphere.

Vacuum hot pressing sintering

Hot pressing sintering is a process of applying pressure to the powder that is difficult to sinter in the mold and sintering it at the same time. The mold is required to be conductive and pressure-resistant. At present, graphite is the most widely used mold material. Graphite is prone to oxidation at high temperatures, but it happens that the service life of graphite can be well extended under closed vacuum conditions. At the same time, vacuum conditions can promote the diffusion of anions. Therefore, vacuum hot pressing sintering has become an important sintering method.

Photofunctional ceramics can be prepared by vacuum hot pressing. The assistance of external pressure can effectively promote densification, shorten sintering time, and reduce energy consumption. In addition, for other ceramics that are difficult to sinter densely under normal pressure, vacuum hot pressing technology has also achieved better performance, such as the widely used ZnO and MgO ceramics.

Vacuum Sintering Furnace