Principle and characteristics of Microwave Sintering Technology
The microwave sintering is that the microwave energy can be converted into thermal energy by using a material and a microwave electric field or a magnetic field coupling, so that the material can be simultaneously heated both inside and outside, so that the temperature gradient inside the material is small, and the temperature gradient is not even and the internal heat stress of the material is reduced to the lowest, so that the cracking and deformation of the material during the sintering process can be effectively relieved, and the material has better mechanical property.
Compared with the traditional sintering technology, microwave sintering can significantly reduce the sintering temperature, in addition, the heating rate of microwave sintering can shorten the sintering cycle greatly. At the same time, in the microwave field, the material itself is a heat source, and the microwave energy directly interacts with the matter, avoiding contact with other parts that are used for heating but not directly involved in sintering, thus greatly reducing the energy consumption. Compared with conventional sintering, energy saving is 70% and 90%; Microwave sintering is rapid and can significantly reduce the amount of gas used in sintering atmosphere. The waste heat emission from sintering process is reduced and the waste heat is friendly to the environment.
Under the action of microwave electromagnetic energy, the material will produce a series of "microwave effects", which will increase the kinetic energy of the molecule inside the material, increase the diffusion coefficient, decrease the activation energy of sintering, speed up the sintering process and shorten the sintering period. The grain is sintered before it can grow, and the fine grain is obtained. The porosity of the material is smaller and the pore shape is more smooth than that of the traditional sintering, which makes the material have better mechanical properties. Microwave sintering can inhibit grain growth, which provides a potentially feasible and efficient method for the preparation of nanomaterials.
The dielectric properties of different materials are different, so the absorption of microwave is different, and the thermal effect in microwave field is also different. Using this point, the multiphase mixed materials can be selectively sintered. New materials can be prepared and materials with better properties can be obtained.