화학공학소재연구정보센터
Molecular Crystals and Liquid Crystals, Vol.424, 253-264, 2004
Mechanism of surface crystal formation on NaF, mother crystal for nano-technology
An investigation of mechanisin that the surface crystals forming on the mother crystal of NaF in the course of the solution, crystallization was attempted by using the additive molecules and excess species of reactants (NaOH and NH4F) in NaF crystallization. Based on the mechanism, it was supposed that the surface crystal formation was dictated by the interfacial supersaturation on the crystal, which was determined the bulk diffusion and surface integration of the molecular growth process. As the surface integration was inhibited or the bulk diffusion. was facilitated, the interfacial supersaturation was improved, the surface crystal formation. Thereby, the population of the surface crystal was found to increase as increasing the reacatant, concentration and agitation speed, which promoted the, bulk diffusion. Similarly, as surface integration was retarded by the ionic additives of NaOH, NH4F and KCl, the surface crystal formation was facilitated due to the interfacial supersaturation increased. However, it was found that the surface crystal formation was suppressed by lite NH4OH was added in the crystallization because of relaxation effect of NH4OH on compact adsorption of NaOH on the crystals. Those experimental results of additives and excess species effects were consistent with the mechanism of the surface crystal formation.