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Hot-pressing sintering and corrosion resistance of nano-yttrium oxide Y2O3 in ceramics

2019-04-28
As an important special refractory material, yttrium oxide (Y2O3) ceramics have good heat resistance, corrosion resistance and high temperature stability. It is an ideal crucible and mold container for the preparation of active metals and alloys (such as titanium and titanium alloys).
 
The corrosion resistance of molten salt is closely related to porosity, relative density, pore diameter distribution and chemical stability of the material. The reduction or even elimination of grain boundary pores can strengthen grain boundary binding, improve compactness and improve the corrosion resistance of ceramic materials.High temperature sintering is helpful for grain boundary migration, pore spheroidization shrinkage and grain growth during sintering process, which can effectively reduce the dissolution rate of corrosion resistant materials in molten salt and improve corrosion resistance.
 
Hot pressing is to heat the loose powder or powder blank in the mold of specific shape and apply certain pressure on the powder at the same time to realize the molding and sintering at the same time.In the sintering process, external pressure always exists, which is conducive to the diffusion of pores or vacancies from grain boundaries, acceleration of particle flow and plastic deformation, acceleration of pore spheroidization shrinkage, reduction of connected pores at grain boundaries, strengthening of phase grain boundary combination, and improvement of densification of sintered products.In addition, hot pressing sintering can ensure the close contact of powder particles, reduce the sintering temperature, shorten the sintering time, and accelerate the densification process, which is essential to improve the material structure characteristics, reduce porosity, and improve the corrosion resistance of Y2O3 ceramics.

 
High sintering temperature can promote the diffusion and migration of Y2O3 phase particles, promote the growth of grains, accelerate the spheroidization shrinkage of pores, reduce the connected pores of grain boundaries, strengthen the integration of ceramic phase grain boundaries, and improve the material densification.The increase of the relative density of Y2O3 ceramics can effectively inhibit the penetration of molten salt into the ceramic body through the grain boundary pores, reduce the direct contact between grains and molten salt in the ceramic phase, erode the grain boundary, defects and other corrosion prone areas, effectively reduce the penetration depth of molten salt, and reduce the dissolution rate of the ceramic phase in the high temperature molten salt.