Measurement of Crystal Face Specific Growth Kinetics

An instrument for measurement of face specific growth kinetics of crystals growing in a solution is developed and applied to crystallization of sodium nitrate (NaNO3) and potassium dihydrogen phosphate (KH2PO4, KDP). The device consists of three major components, a stereovision imaging system that captures in real time the size change in each face direction of the crystal, an ATR-FTIR probe measuring solution concentration and supersaturation, and a small purpose-designed crystallizer that allows a crystal to be fixed in the solution and adequate solution mixing so the concentration measured can reflect the solution concentration near the surfaces of the crystal. The growth rates of all independent faces of NaNO3 and KDP crystals were derived at each time interval. For the NaNO3 crystal, growth rates in the temperature range 298.15–318.15 K and the supersaturation range 0.01–0.11 were measured, enabling a systematic kinetic study. For the KDP crystal, the growth rates were measured just to show the capability of the system in handling crystals with different morphologies.