Cooling source strategy for synthesis of highly porous tungsten using freeze-drying technology

Porous tungsten is composed of tungsten skeleton with numerous internal pores, and shows high temperature resistance, good corrosion resistance, large specific surface, and high permeability, promising for aviation, electronics, and high temperature manufacture applications. Formation of the highly porous tungsten structures has been a key barrier for its successful applications. In this study, porous tungsten was prepared using a freeze-drying method, and influences of cooling sources’ distributions on microstructures and properties of porous tungsten were investigated. Results showed that the distribution of cold source has significant influences on detailed structures of porous tungsten. Lamellar and porous structures were obtained when the ice crystals were grown in a columnar form. We proposed that shapes and sizes of these porous structures were controlled by a combined effect of ice crystal growth rate and particle sedimentation rate.