Influence of some foreign metal ions on crystal growth kinetics of brushite (CaHPO₄ · 2H₂O)

TY - JOUR

T1 - Influence of some foreign metal ions on crystal growth kinetics of brushite (CaHPO4 · 2H2O)

AU - Rosa, Silvia

AU - Madsen, Hans Erik Lundager

PY - 2010/10/1

Y1 - 2010/10/1

N2 - Brushite, CaHPO4·2H2O, has been precipitated at 25 °C in the presence of Mg2+, Ba2+ or Cu 2+ at concentrations up to 0.5 mM. When initial pH is sufficiently low to exclude nanocrystalline apatite as the initial solid phase, overall crystal growth rate may be determined from simple mass crystallization by recording pH as function of time. A combination of surface nucleation (birth-and-spread) and spiral (BCF) growth was found. Edge free energy was determined from the former contribution and was found to be a linear function of chemical potential of the additive, indicating constant adsorption over a wide range of additive concentrations. Average distances between adsorbed additive ions as calculated from slopes of plots are compatible with lattice parameters of brushite: 0.54 nm for Mg2+, 0.43 nm for Ba2+ and 0.86 nm for Cu2+. With the latter a sharp decrease in growth rate occurred early in the crystallization process, followed by an equally sharp increase to the previous level. When interpreted in terms of the Cabrera-Vermilyea theory of crystal growth inhibition, the results are consistent with an average distance between Cu ions of 0.88 nm, in perfect agreement with the above value.

AB - Brushite, CaHPO4·2H2O, has been precipitated at 25 °C in the presence of Mg2+, Ba2+ or Cu 2+ at concentrations up to 0.5 mM. When initial pH is sufficiently low to exclude nanocrystalline apatite as the initial solid phase, overall crystal growth rate may be determined from simple mass crystallization by recording pH as function of time. A combination of surface nucleation (birth-and-spread) and spiral (BCF) growth was found. Edge free energy was determined from the former contribution and was found to be a linear function of chemical potential of the additive, indicating constant adsorption over a wide range of additive concentrations. Average distances between adsorbed additive ions as calculated from slopes of plots are compatible with lattice parameters of brushite: 0.54 nm for Mg2+, 0.43 nm for Ba2+ and 0.86 nm for Cu2+. With the latter a sharp decrease in growth rate occurred early in the crystallization process, followed by an equally sharp increase to the previous level. When interpreted in terms of the Cabrera-Vermilyea theory of crystal growth inhibition, the results are consistent with an average distance between Cu ions of 0.88 nm, in perfect agreement with the above value.

U2 - 10.1016/j.jcrysgro.2010.07.029

DO - 10.1016/j.jcrysgro.2010.07.029

M3 - Journal article

SN - 0022-0248

VL - 312

SP - 2983

EP - 2988

JO - Journal of Crystal Growth

JF - Journal of Crystal Growth

IS - 20

ER -