| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2001: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2000: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The chemical structure of titanium surface polished with SiC, Al_2O_3, Fe_20_3, Si0_2 and Cr_2O_3 was investigated by means of surface analysis methods. Si, Al, Fe, and Cr contaminated the surface with non-uniform distributions. The higher polishing pressure, the more remarkably the surface was contaminated, which failed to create a smooth and chemically clean surface. Finer abrasive grain and lower pressure is essential for a mirror-like surface. The surface contamination resulted from destruction of the passive oxide film through cutting action of abrasives, and resultantly from their reactions with inherently active titanium. Actually, Fe was suggested to exist as Fe^<2+> at the outermost surface. Al and Cr might exist as trivalent hydroxide. Moreover, the surface polished under higher pressure was tinged with a pale brown or gold-like color, as if it was anode oxidized. The surface analyzes proved that this was a result of notable increase in the oxide film thickness. It is doubtfu
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l, however, whether the increased thickness raises favorably the corrosion resistance of titanium, since the film had abrasive constituent elements and its thickness was non-uniform. Polishing with colloidal silica, regardless of polishing pressure, provided a chemically clean mirror-like surface. Si was hardly detected in the oxide film and its thickness did not change. Together with mechanical action of silica, some colloid stabilizing agents might dissolve the oxide film and reaction products between titanium and silica. When immersed in an electrolyte solution, the polished surface under higher pressure showed the existence of higher amounts of Ca and P, compared with lower pressure, which corresponded to the increased thickness of the oxide film. The protein-absorbed layer was suggested to be thicker in the colloidal silica-polished surface. For the understanding of in vivo behaviors of titanium, including the protein-absorbability, it is necessary to investigate more precisely the chemical structure of surface modified by various methods. Less
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