チタンドープアパタイトの構造と光触媒機能性

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Hydroxyapatite (HAp) has a molecular structure in which Ca^<2+>, PO_4^<3-> and OH^- are major components. When hydroxyapatite is formed the Ca^<2+>, PO_4^<3-> and OH^- ions can be substituted with other specific ions. When a specific ion is purposely replaced in the forming hydroxyapatite crystal, there is a possibility that the new hydroxyapatite might demonstrate properties that could be attributed to the substituted ion. This change in hydroxyapatite properties has been demonstrated when F^- has been substituted for OH^-, F^- has significant acid resistance. The acid resistance property of F^- was observed when F^- was substituted for OH^- in hydroxyapatite. Therefore, the author performed the following experiment : The first portion of the experiment was the synthesis of HAp using the coprecipitation method substituting Ti^<4+> for Ca^<2+>. The Ti^<4+> was doped to the Ca^<2+> position in the forming hydroxyapatite crystal. In the next phase of this experiment the author analyzed whether the HAp had obtained photocatalytic function that is a major character of Ti^<4+>. HAp using the coprecipitation method was synthesized with different concentrations of Ti^<4+>. Respectively the HAp was prepared with Ti^<4+> concentrations of 0.01, 0.005, 0.0025 and 0 moles. The determination of the elementary composition of the synthesized TiHAp was investigated with ICP analysis. The structure of the TiHAp crystal was also investigated by X-ray diffraction. The TiHAp was irradiated by ultraviolet light to determine and measure the presence of photocatalytic function. The formation of radicals and their strength were also measured by ESR spin trapping. A specimen was prepared with 1% TiHAp combined with polypropylene and a second specimen was prepared with 1% TiHAp combined acrylic denture base resins. These specimens were then investigated by a facilitated deterioration exposure test. The photocatalytic function of each specimen was also investigated. The following conclusions of the experiment were obtained : 1. The X-ray diffraction of the TiHAp showed a. reversed correlative phenomenon when anatase dioxide titanium was at 25° (2θ) and the peak strength of HAp was at 26° (2θ) due to the doped Ti^<4+>. Therefore, the observed change in the HAp must be a consequence of the doped Ti^<4+> into the HAp molecule. The mole ratio of the Ca/P in the synthetic substance showed that the Ti^<4+> concentration was dependent on the successful doping of Ti^<4+> for Ca^<2+>. It was observed that the more successful the dope of Ti^<4+> for Ca^<2+> the mole ratio showed a rectilinear decrease. Therefore, this observation confirmed that Ti^<4+> had replaced Ca^<2+>. 2. The OH radical was identified from the post ultraviolet irradiated synthesized substance. The strength of the OH radical increased when the success of the substitution of Ti^<4+> for Ca^<2+> increased. 3. The observation of a clear OH radical signal by ultraviolet irradiation was confirmed from the outer layers of both the polypropylene and acrylic denture base resins that had been combined with 1 % of the synthesized TiHAp. It was observed that there was delayed depletion in the resins that had been combined with the synthesized TiHAp. The results of this experiment provided these conclusions : When a desired concentration of Ti^<4+> has been successfully substituted for Ca^<2+> in a synthesized hydroxyapatite crystal the newly synthesized HAp obtained photocatalytic function that is a special characteristic of titanium.
奥羽大学の論文
2005-06-30

チタンドープアパタイトの構造と光触媒機能性

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