A hydroxyapatite is most suitable biomaterial for clinical application, because it is a main component which constitutes bones and teeth of an organism. Since the hydroxyapatite has different biocompatibility and absorptive activity of proteins for its crystal plane, it is necessary to use the appropriate crystal plane for use in vivo. Thus, the crystal orientation of the hydroxyapatite is one of the very crucial subjects in biomaterials processing. In this study, the control of crystal orientation of the hydroxyapatite has been conducted in the colloidal filtration (slip casting) process under a high magnetic field and a new process where the high magnetic field is introduced in the heat substrate method developed by Okido et al. The usefulness of the processes has been confirmed through the orientation index evaluated by X-ray diffraction patterns and scanning electron microscope (SEM) images of hydroxyapatite crystals. The crystal axis of hydroxyapatite aligned by a magnetic field was determined.
The electronic structure of the one-dimensional Ni complexes, ͓Ni͑chxn͒ 2 X]X 2 "XϭCl, Br; ͑chxn͒ϭ1R,2R-cyclohexanediamine…, is studied together with the discrete Ni complexes, ͓NiX 2 (͓14͔aneN 4 ͔͒ClO 4 "X ϭCl; Br;͓͑14͔aneN 4 ͒ϭ1,4,8,11-tetraazacyclotetradecane…,using optical spectroscopy, x-ray photoelectron spectroscopy ͑XPS͒ and Auger electron spectroscopy. The optical spectra show that the Br compounds have a smaller gap as compared with the Cl compounds. An analysis using a simple X-Ni-X trimer model on the optical spectra and the Ni 2p XP spectra yields quantitative estimates for the charge transfer ͑CT͒ energy ⌬ and the transfer energy T for discrete and one-dimensional Ni complexes. The analysis on the Ni LVV Auger spectra in conjunction with the valence XP spectra indicates that the average on-side d-d Coulomb energy U in the one-dimensional and discrete Ni complexes is about 5 eV, quite similar to the case of the Ni dihalides. The obtained results demonstrate that the one-dimensional Ni complexes are CT insulators. We discuss the differences in the electronic structures of the one-dimensional Ni complexes compared with the Ni dihalides and the one-dimensional Pt complexes on the basis of the estimated parameter values of ⌬, T, and U.
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