Similar to KH2PO4, NaNO2 is also a

Similar to KH2PO4, NaNO2 is also a hygroscopic compound, which is very soluble in water (84.8 g/100 mL at 25°C). Such a large solubility guarantees a fast “dissolution-precipitation” process for compound dissolving and recrystallization, hence dense NaNO2 ceramics could be expected by utilizing Cold Sintering Process under appropriate conditions. The cold sintered-dense ceramics are actually a result of the coupling effects of temperature and pressure. In the case of as-pressed NaNO2 bulk ceramics, a relative density of 85% was obtained after air drying the ceramics at room temperature. This scenario could be understood using a simple thermodynamic perspective, where an open system is readily formed when the as-pressed green body with an aqueous content issurrounded by an ambient environment; mass and energy exchanges take place between these two components (namely the ceramics and environment) owing to the water evaporation; a supersaturate NaNO2 water solution is subsequently formed, which provides the dynamic driving force for thenatural precipitation process.