The preparation process of advanced ceramics includes powder preparation, molding, sintering and finishing. Among them, sintering is a technology that compacts the ceramic green body at high temperature and finally forms a solid material. The sintering technology plays a vital role in the production process of advanced ceramics. Common sintering methods include normal pressure sintering, hot pressing sintering, hot isostatic pressing sintering, and microwave sintering. Among them, hot pressing sintering is a widely used method at present.
In the hot press sintering process, it can be divided into constant pressure method, high temperature press method, and sectional press method according to the different press methods. According to the sinter method, it can be divided into vacuum sintering, atmospheric sintering, continuous press sintering, etc.
Compared with other sintering methods, the hot-press sintering process has the following advantages: the hot-press sintering process is performed simultaneously with heating and pressing, and the powder is in a thermoplastic state, which helps the contact diffusion flow of the particles and facilitates the mass transfer process, so it is shaped Low pressure; can also reduce the sintering temperature and shorten the sintering time to resist the growth of grains to obtain products with fine grains, high density, high mechanical properties and high mechanical properties, without the need to add sintering aids Or molding aids can produce ultra-high purity ceramic products.
Hot pressing sintering equipment
The hot-press sintering process requires a dedicated hot-press sintering furnace. The commonly used hot-press sintering furnace is mainly composed of a heating furnace, a pressurizing device, a mold and a pressure measuring device. The working principle of the hot-press sintering furnace is: put the mixed powder into the graphite mold, and heat the powder through the graphite heating sheet. After heating to a certain temperature, the upper and lower pressure heads drive the graphite upper pressure head and the graphite lower pressure head to apply pressure to the powder in the mold to achieve sintering and pressing to be synchronized, so that the powder can be densified and sintered under high temperature and high pressure.
Hot pressed sintered alumina ceramics
The AlTiC master alloy is introduced into alumina ceramics, and the TiC/Al2O3 composite material is prepared by the transition liquid phase hot pressing method. The AlTiC master alloy suppresses the grain growth of alumina, and organically combines hot pressing and transition liquid phase sintering to enhance TiC /Al2O3 composite sintering quality. Fine-grained alumina ceramics were prepared by hot-pressing the pre-treated alumina powder, and alumina ceramics with a grain size of 0.5 μm and a flexural strength of 500 MPa were obtained by hot pressing at 1450°C. At 1550°C, an alumina ceramic material with a fracture toughness of 5.7 MPa·m1/2 was obtained.
