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Variations in Solution Chemistry During the Low‐Temperature Formation of Hydroxyapatite
Author(s) -
Brown Paul W.,
Hocker Nancy,
Hoyle Susan
Publication year - 1991
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1991.tb07798.x
Subject(s) - chemistry , dissolution , aqueous solution , stoichiometry , precipitation , inorganic chemistry , calcium , phosphate , chemical engineering , magnesium , mineralogy , organic chemistry , physics , meteorology , engineering
Both the kinetics and the microstructure of monolithic hydroxyapatite formed by a low‐temperature dissolution and precipitation reaction strongly depend on the conditions in solution during the reaction. The relationships between the molar ratio of the particulate reactants (dicalcium phosphate and tetracalcium phosphate), the solution chemistry, and the rates of formation of hydroxyapatite are examined. During reaction, steady‐state solution conditions are rapidly achieved. However, the steady states attained are not those associated with the metastable invariant point involving the reactants. Rather, the steady‐state condition varies depending on the molar ratio of the reactants. The ultimate product of the reactions investigated is calcium‐deficient hydroxyapatite. Hydroxyapatite formation occurs in two stages: initial formation of nearly stoichiometric hydroxyapatite followed by its conversion to calcium‐deficient material. Microstructural evidence indicates that the formation of hydroxyapatite occurs in association with dicalcium phosphate, eventually causing the dissolution of the hydroxyapatite reactant to become diffusionally controlled. Effects of common ions, sodium chloride and magnesium chloride, on the chemistry of the aqueous phase and on microstructural development are investigated.