α及びβ-ビス(オルトリン酸)三カルシウムに対するOH^-及びF^-イオンの競争攻撃によるフッ素化アパタイトの生成

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The process of formation of fluoridated hydroxyapatite, [Ca_<10>(PO_4)_6(OH)_<2-2x>F_<2x>] (FHA_p) through the hydrolysis of α- or β-tricalcium bis (orthophosphate), [Ca_3(PO_4)_2] (α- or β-TCP) in the presence of fluoride ions (F^-) was examined. The presence of F^- ions improved the hydrolysis of both TCPs. The quantity of F^- ions incorporated into the apatite increased with the molar ratio (R) of ammonium fluoride to TCP (R = NH_4F/TCP). When R = 0.7, the molar ratio of Ca/P in the products, which contained small amount of CO_3^<2-> ion, was 1.68. On the other hand, for R = 0.18 or 0.35, the Ca/P ratio decreased to 1.61-1.64. This phenomenon indicates the formation of Ca-deficient FHAps containing HPO_4^<2-> (and CO_3^<2->) ions. FHAp formed from α-TCP contained fine particles with a size smaller than 0.5μm, and needle-like crystals whose width depended on the value of R. FHAp formed from β-TCP was needle-like for R = 0.18, and spindle-like for R = 0.70. Differences in the hydrolysis process between α-TCP and β-TCP were observed. α-TCP is attacked by OH^- and F^- ions which compete in the formation of FHAp crystals on the surface of the α-TCP particles. On the other hand, β-TCP is attacked by F^- ions and forms clusters, and then some of the F^- ions that are incorporated in the clusters are liberated, depending on the F^- ion concentration in the solution. The clusters loosing F^- ions incorporate OH^- ions to form FHAp. The F^- ions liberated from the clusters then again attack the residual β-TCP. When R = 0.18, at an early stage, FHAp with a composition close to fluorapatite [Ca_<10>(PO_4)_6F_2] (FAp) was formed. Then, following the reduction of the F^- ion concentration in the reaction media. FHAp with a composition close to hydroxyapatite, [Ca_<10>(PO_4)_6(OH)_2] (HAp), was formed.
社団法人日本セラミックス協会の論文
2004-01-01

α及びβ-ビス(オルトリン酸)三カルシウムに対するOH^-及びF^-イオンの競争攻撃によるフッ素化アパタイトの生成

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