Microstructure designed granular hydroxyapatite (Ca10(PO)4(OH)2; HA) was prepared by hydrothermal method. The size of granules of less than 100 μm, the shape of particles in the granules, and the micro-pore of about 0.1 μm in size of the granules were controlled. The granular HA prepared at 200°C for 20 h was composed of rod-shaped crystals of about 50 μm in length with the mean aspect ratio of 50. Rod-shaped HA crystals were locked together to make micro-pores of about 0. 1 μm in size. It was non-stoichiometric HA with calcium deficient composition. This granular HA must have the advantage of adsorptive activity, because the HA has many specific crystal surface and micro-pores.

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Formation of β-TOP solid solution by simultaneous addition of mono and divalent metal ion was investigated. Monovalent metal ions were added to raw materials as 2M^I = Ga+ (M^I : monovalent metal ion, :vacancy) from 0mol% to 20mol% of monovalent metal ion. Divalent metal ions were added to raw materials as M^II = Ca (M^II : divalent metal ion) from 0mol% to 20mol% of divalent metal ion. The Ca₉M^IIM^I (PO₄)₇ phase could be observed in β-TCP containing more than 9.09mol% of monovalent metal ion. The length of a-axis and c-axis changed linearly with increasing amount of monovalent metal ion up to 9.09mol%. From these results, limit of amount of mono and divalent metal ion substituted into β-TCP was 18.2mol%.

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The caking behivior of apatite hydrogel was studied.Di-Sodium hydrogen phosphate dodeca-hydrate amd calcium chloride 2 hydrate was dissolved in distilled water,and pH was ajusted to be 7.40.The mixed solution was kept at room temperature for several days.The shrinkage behavior of obtained apatite hydrogel seems to be similar independs on the maturation period of mixed solution.With an increase of maturation period, particle size of apatite hydrogel decreased, while crystallite size of apatite hydrogel is almost the same.Re-aggergation process should be included in drying process,and the specimen with different particle size show the same manner of shrinkage during drying.

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Influence of processing time of dry ball milling for β-TCP (Ca₃(PO₄)₂)on strength development with hydrothermal treatment was investigated. β-TCP was ground by dry ball milling for 0.5-8h and formed by uniaxial pressing. The formed body was hydrothermally treated at 180°C for 6h under saturated steam pressure. In all cases, hydroxy apatite (HAp: Ca₁₀(PO₄)₆(OH)₂) was formed by hydrothermal treatment. The flexural strength increased with milling time and reached the maximum value of 23.6MPa for 2h. The increase in the flexural strength by dry ball milling was caused by the increase of bulk density and contact point of fine HAp crystals.

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Bonelike apatite-forming ability on 60CaO-30P₂O₅-3TiO₂-7Na₂O; PIG3 (mo1%) glass-ceramic was found to be easily improved using the autoclaving treatment at 100~180 C for 1 h. PIG3 glass-ceramic consists ofβ-Ca₃(PO₄)₂ (β-TCP) andβ-Ca₂P₂O₇ (β-CPP) crystal phases with a glassy phase having a composition of 50CaO-30P₂0₅-10TiO₂-10Na₂O. Although β-TCP was reported to form the apatite in SBF, an autoclaved β-TCP ceramic was found to form the apatite on the surfaces within 10 days in SBF. An autoclaved β-CPP ceramic and 50CaO-30P₂O₅-10TiO₂-10Na₂O glass form no apatite. Improvement of the bonelike apatite-forming ability on PIG3 glass-ceramic is suggested to be closely related to surface modification of β-TCP crystal.

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Although ceramics form could be very useful bone filler or scaffold for tissue engineering, little is known about the physical properties of apatite form. In this study, effects of sintering temperature on the physical properties of apatite form were studied. Composition of the form was mainly apatite with small amount of a-TCP. Mechanical strength increased with increase in sintering temperature to reach 45KPa at 1550 degrees. Porosity of the apatite form decreased with increase in the sintering temperature. For example, porosities of the apatite form were 90% and 94% at 1300 and 1550 degrees, respectively.

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Three dimensionally ordered porous bioactive ceramics are interesting as new artificial born. In this study, the porous ceramics were prepared with colloidal crystal templating method using polystyrene beads. HAp was selected as the porous ceramic matrix. The pore sizes of three dimensionally ordered macro-porous HAp were controlled with polystyrene beads with different diameters. These materials exhibited a good biocompatibility by examining in vitro test using a simulated body fluid (SBF).

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Porous a-tricalcium phosphate (α-TCP) is expected as a candidate of novel bioresorbable ceramics in orthopaedic field, since it can be easily fabricated through sintering of β-TCP by conventional process at high temperature. However, solubility of α-TCP is much higher than that of β-TCP, and α-TCP is therefore liable to be dissolved much faster than bone repair. In this study, we investigated biodegradation of porous α-TCP coated with sericin in vivo. Bone repair at the defect made in rabbit tibia was nearly completed for 4 weeks when α-TCP coated with sericin was implanted.

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Porous β-TCP was evaluated as a carrier for tissue engineering. Bone grafting material Sferion, consisted by β-TCP of 75% porosity, showed good property as a carrier. The object of this study is to investigate the potential of β-TCP combined with growth factors which are bFGF and TGF β. Rat's MSC was caltured on β-TCP and β-TCP/growth factor composites, and evaluated by ALP assay and then implanted subcutaneous site.

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Electrical property related in hydroxide ion of hydroxyapatite (HAp) ceramics, which sintered in various ambiences, were studied. Sintering ambiences, such as water vapor and argon gas, brought HAp single phase, however HAp sintered in air ambience was also consisted of α-TCP as thermal decomposition. From the results of impedance measurements, the HAp sintered in water vapor showed lower activation energy than those of the other. There fore, it was considered that the HAp sintered in water vapor showed higher ionic conductivity and more OH- ions.

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HAp powder was synthesized using calcium nitrate tetrahydrade and ammonium dihydrogenphosphate by precipitation method. The crystal growth of bone-like apatite was accelerated on N-surface for electrovectorial effect. N-surface attracted calcium ion whereas P-surface repulsed calcium ion by electorovectorial effect. The crystal growth on the polarized treatment at 300°C of P-surface for 5days was turned slowly.

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Electrically polarized bioactive glass (BG) was investigated in polarization properties by a thermally stimulated depolarization current measurement and observed on surface reaction with blood of rat. The polarization of BG was able to be controlled by controlling polarization temperature, applied dc field and polarization time. The surface reactions with blood components changed between non-polarized BG and polarized one.

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Effects of induced surface charges generated by electrical poling on SDS film formation on hydroxyapatite (HA) ceramic substrates from the aqueous solution. The films on the non-poled HA ceramics was significantly thicker than those on the poled ceramics, regardless of the charge polarity. The characteristic absorption band was detected in the films on the negatively charged HA surfaces by FT-IR spectroscopy. It was revealed that the induced charges affected the formation rate and the structures of SDS films.

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Natural bone is a composite in which inorganic apatite crystals are deposited on organic collagen fibers woven into a three-dimensional structure. Three-dimensional ethylene-vinyl alcohol copolymer (EVOH) braids were treated with calcium silicate solution. Dense and uniform calcium silicate layer was formed on the suface of EVOH braid. Thus treated EVOH braids formed bonelike apatite layer on their surfaces. It can be believed that the present apatite-polymer composite with three-dimensional structure could exhibit bone-bonding ability and mechanical properties analogous to those of human bone.

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In the present study, CaSiO3 ceramics were prepared and their bioactivities were evaluated using continuous flowing SBF system, which is higher similarity to human blood system than static SBF system. The hydroxyapatite (HAp) formation rate in the flowing system was slower than the static system. The microstructures of HAp were also differed by changing flowing speed of SBF. The decrease of the HAp formation rate may occur due to the suppression of increases of Ca concentration and pH by SBF flowing. It is considered that flowing speed of SBF has great influence on HAp formation.

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Titanium substrates were subject to a H₂O₂ treatment subsequent heating to prepare titania layers. Apatite formation was then examined after soaking the substrates in both Kokubo's simulated body fluids (SBF) and modified SBF containing organic components such as succinic acid, tartaric acid and citric acid. Calcium-chelate formation due to the organic acids reduced free calcium ion concentration. The induction time of apatite nucleation on the titania surface was delayed in SBF containing the organic acids. The reduction in the free calcium ion concentration suppressed the apatite nucleation.

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Preparation of anatase nao-particle containing PMMA bone cements was attempted and apatite-forming abilities and mechanical properties of the resultant cements were examined. All the examined cements formed apatite on their surfaces within 1 d in SBF. Their apatite-forming abilities were increased with increasing particle amount and decreasing particle size. Bending strengths of the present cements were smaller than that of PMMA cement, and approximately half of that of glass-ceramic A-W-containing cement.

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So-called bioactive ceramics have been attractive because they spontaneously bond to living bone. Organic-inorganic hybrids consisting of organic polymers and the essential constituents of the bioactive ceramics, i.e. Si-OH group and Ca2+, are useful as novel bone substitutes, owing to bioactivity and high flexibility. In the present study, organic-inorganic hybrids were synthesized from chitin by modification with glycidoxypropyltrimethoxysilane (GPS) and calcium chloride (CaCl2). Their apatite-forming ability was examined in a simulated body fluid (Kokubo solution). Homogeneous bulk gel was obtained when mass ratio of chitin to the total of chitin and GPS was 0.25. The prepared hybrids formed apatite on their surfaces in Kokubo solution within 7 days. This indicates that such modification is also available to chitin-based biomaterials with bone-bonding ability.

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Chitin and chitosan have been widely used as biocompatible and biodegradable materials. A tendon of crab is composed of highly aligned crystalline chitin. On the other hand, hydroxyapatite (HAp) has been used as an artificial bone because of its biocompatibility. If the composite of the crystalline chitosan and HAp is developed, it should have both high intensity and excellent biocompatibility. In this paper, the formation of HAp nano-crystallites on the crystalline chitosan derived from crab tendons was studied as a function of thermal treatment.

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Synthetic organic polymers were modified with sulfonic (SO3H)groups, followed for treatment in saturated calcium hydroxide solution and their apatite-forming ability were tested in a simulated body fluid (SBF). Sulfonation reaction of the polymer substrates was carried out in mild conditions to avoid surface damage, allowing the incorporation of SO3H groups in the surface layer. Chemical changes in the polymer substrates were revealed after XRD, FTIR, SEM and EDX analysis, which also proved that sulfonation process was harmless for the surface morphology. Treatment in calcium hydroxide allows the stabilisation of sulfonic groups, which enhance the ionic strenght in the material environment in physiological media through its release from the surface of specimens. Sulfonated polymers were able to induce apatite nucleation and growth after seven days in SBF. It is thougth that this kind of materials is suitable for bone substitutes with analogous properties of natural bone.

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The effects of simulated body environment on mechanical properties and fracture behavior of bioceramics were investigated. Three types of alumina were used for specimens, and 4 point bending tests were carried out in air, refined water, the simulated body fluid (SBF) and Physiological Saline. The microfracture process during the bending tests was evaluated by the acoustic emission technique. The critical increases in both cumulative AE event and energy were observed before the final unstable fracture, then the critical stress, σc, for maincrack formation was determined from the AE behavior. Comparing the bending strength, σc was more influenced by test environments.

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The effect of strain rate on mechanical properties and fracture behavior of alumina for artificial joints under simulated body environment was investigated. 4 point bending tests were carried out in air, refined water, simulated body fluid and physiological saline at low strain rate, and the critical stress, σc, for maincrack formation was determined from the AE behavior. Comparing with the experimental results at high strain rate tests, it was clarified that the effect of strain rate on σc is little in this material.

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Commercial artificial hip joints with different combinations of head and cup were subjected to assessments in a hip simulator. In the combination of Y-TZP head and UHMWPE cup, it was found that the head received almost no wear, while the cup received fine wear tracks. In the combination of Co-Cr head and UHMWPE cup, the wear was to found to progress severely both on the head and cup, during which metal ions were released from the head surface. In the combination of Y-TZP head and C-UHMWPE cup, the cup surface received fine wear tracks. In the combination of Al2O3 head and Al2O3 cup, the wear was found to progress almost none both on the head and cup surfaces.

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Photocatalytic activities for H₂ evolution of rare earth titanium oxides, RE₂Ti₂O₇ (RE = La, Pr, Nd, Sm, Gd, Dy, Ho, Er, Yb), were investigated. These compounds were synthesized by the solid state reaction or sol-gel method. The products were characterized by X-ray diffraction (XRD) and the particle size was observed by Scanning Electron Microscope (SEM). The band gap energy was estimated by the UV-VIS absorption spectra. Photocatalytic reactions were carried out in a closed gas cell system. Under 500 W Xe lamp light irradiation, H₂ gas was clearly evolved in distilled water suspended La₂Ti₂O₇ or Sm₂Ti₂O₇.

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Photocatalytic activities for H₂ evolution of rare earth zirconium oxides, RE₂Zr₂O₇, (RE = La, Nd, Sm, Ce) were investigated. These compounds were prepared by sol-gel method using RE(NO₃)₃ and ZrO(NO₃)₂ as starting materials. Photocatalytic reactions were carried out in a closed gas cell system with a quartz window at room temperature. Photoelectrochemical properties, band gap energy (E_g) and flat band potential (U_fb), of RE₂Zr₂O₇ thin film electrode were measured. Under 500 W Xe lamp light irradiation, hydrogen gas was evolved in distilled water suspended La₂Zr₂O₇, Sm₂Zr₂O₇, and Nd₂Zr₂O₇ without co-catalyst.

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Photocatalytic activities for H₂ evolution of alkaline uranium oxides, AL₂U₂O₇ (AL = K, Na), and alkaline earth uranium oxide, AEUO4 (AE = Ca, Sr, Ba) were investigated. These compounds were synthesized by the solid state reaction method using AL₂C0₃, or AE₂C0₃ and UO₂ as starting materials. The products were characterized by X-ray diffraction (XRD) and the particle size was observed by Scanning Electron Microscope (SEM). Photocatalytic reactions were carried out in a closed gas cell system. Under 500 W Xe Lamp light irradiation, H2 gas was evolved in distilled water suspended SrUO₄ or BaUO₄ powder.

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Mesoporous nanotubes consisting of nano-crystalline TiO₂ were successfully synthesized through a sol-gel route using a double-templating technique. The tube morphology of TiO₂ was obtained with a porous alumina membrane having straight channels of ca. 100 nm in diameter. The mesoporous structure of the tube wall was ascribed to micelles of triblockcopolymers. The samples prepared in straight channels of a porous alumina membrane with a sol-gel route using propanol solutions of titanium tetra-iso-propoxide containing copolymers were a tube having 150 nm diameter and 60 m length. The wall of the tubes consisting of TiO₂ nanocrystals contained mesopores of 5-20 nm in diameter.

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K₂Ti₄O₉, one of layer-structured titanates has ion exchange ability. We have investigated the ion exchange reaction using ion exchange titration. In the region where the amount of potassium in sample is less than hydronium ion from ion exchange resin (phase 1), pH and electric conductivity decreased and in the other region (phase 2) pH and electric conductivity increased slowly. This result showed not only ion exchange reaction but also another reaction occurred in the phase 1 and hydronium ion from ion exchange resin dominated the reaction in the phase 2.

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UV irradiation against RSiO_3/2-TiO₂ films was found to promote the precipitation of anatase nanocrystals during the subsequent hot water treatment. This is probably due to the formation of Si-OH groups and Si-O-Si bonds in the films with UV irradiation. Pattern with anatase nanocrystals can be formed on the films by selective UV exposure and hot water treatment.

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Silica-titania gel films were immersed in hot water under D.C. electric field. The shape of titania nanocrystals precipitated on the films became sheet-like on the negative electrode, whereas it was roundish on the positive electrode.

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Anatase nanocrystals were formed in the microparticles after a hot water treatment. From changes in the concentration of I2 photocatalytically generated from KI solution, the activity of the SiO₂-TiO₂ particles was found to increase with increasing the hot water treatment time.

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Titania ceramic film was successfully prepared from sodium titanate powder by the intercalation of alkyl amine. Highly dispersed titanate plates were deposited on a substrate with a preferred orientation. The effect of heat-treatment on the phase development of titania was evaluated by Raman spectroscopy and XRD. It was confirmed that the bronze type titania film prepared on a substrate kept its preferred orientation after heating at 550°C.

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Highly reduced TiO2 thin film in its rutile modification was prepared by means of helicon sputtering method without applying an additional reducing treatment. Photoelectrochemical (PEC) properties of such sputter deposited films are studied in comparison with that of sol-gel derived TiO2 films. Band model describing the observed PEC characteristics of the helicon plasma sputter deposited highly reduced TiO2 film is then proposed.

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TiO₂ photocatalytic fibers have been prepared from polytitanoxane in sol-gel process. N-doped TiO₂ fibers were obtained by heat-treatment of the polytitanoxane gel fibers or TiO₂ fibers in NH3 atmosphere, and showed a visible-light responsiveness. Under both visible and ultra-violet light irradiations, the photocatalytic activity of N-doped TiO₂ fiber NH₃-treated at 500°C was superior to that of fibers NH₃-treated at 600°C and 700°C.

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TiO₂ photocatalytic microspheres were prepared by heat-treatment at 500°C by sol-gel method using porous organic polymer microspheres as templates. These were N-doped by heat-treatment at 450∼550°C in NH₃ atmosphere. From the measurements of the decomposition rates of pentachlorophenol by N-doped and -undoped TiO₂ spheres, the photocatalytic activity of the fibers N-doped at 500∼550°C was superior to that of the N-undoped under either visible or ultra-violet light irradiations.

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Nitrogen-doped yellowish rutile titania prepared by high energy ball milling of P-25 titania - HMT (Hexamethylenetetramine) mixed powders followed by calcination in air at 400°C possessed two absorption edges around 400 and 540 nm and showed excellent photocatalytic ability for nitrogen monoxide destruction under irradiation of the visible light of wavelength > 510nm.

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Visible light response type titania crystals were prepared from titanium trichloride precursor and ammonia releasing regents such as urea and hexamethylenetetaamine by the homogeneous precipitation - hydrothermal reaction process. Titania powders prepared from these processes possessed large specific surface area and superior visible light absorption and photocatalytic activity for the destruction of NO than those of commercial titanium dioxide P-25.

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[in Japanese]

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Pt-deposited TiO2 powder was prepared by impregnation method and heated at 400°C for 1h. Pt on TiO2 powder was confirmed by EDX of powder samples. The sample was placed in CH3OH solution and exposed to 365 nm light. The gases generated were found to contain H2 gas. Amount of gases generated for Pt-deposited TiO2 is greater than that for TiO2 without Pt. However, it decreases with increasing Pt concentration in the area where the concentration of Pt is high. The potoelectrochemical reaction was very sensitive to the concentration of Pt on TiO2.

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Titania was synthesized in the form of microparticle by sol-gel method. The size of particles was about 4 nm. Addition of acetylene black in synthesis allowed us to obtain titania/carbon composite materials. They were tested as an electrode for lithium secondary battery. They possessed potential around 2 V (vs.Li⁺/Li) and exhibited specific capacity above 100 mAh/g even under large discharge current of 10 A/g (titania weight is used for standardization).

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A variety of oxide nanohole arrays have been prepared from an aqueous solution process. An anodic alumina was immersed in a metal-fluoro complex solution at room temperature and a few hours immersion enabled us to obtain the nanohole arrays of oxides such as titania, iron oxide and tin oxide. The holes were about 200 nm in diameter and penetrated through the disk. The oxide nanohole arrays are attractive for a wide variety of application in different fields such as electrical, optical and chemical devices.

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Titania nanohole arrays have been prepared from an aqueous solution process; by immersing an anodic alumina in ammonium hexafluorotitanate solution at room temperature for a few hours. The obtained titanium nanohole arrays are annealed at several temperatures. The photocatalytic activity of titania nanohole array for decomposition of CH₃CHO was evaluated.

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By immersing an anodic alumina in ammonium hexafluorotitanate solution and ammonium hexafluorostannate at room temperature for a few hours. The obtained composite nanohole arrays are annealed at several temperatures. The photocatalytic activity of titania nanohole array for decomposition of CH₃CHO was evaluated.

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Nanoporous crystal was prepared by solid-stats reaction of mixture of Sr(OH)2 and γ- Al2O3 at 600°C. Lots of O- and O2- were detected by ESR measurement. The spin concentration of the sample that heated at 900°C for 24h in O2 atmosphere was 2.0X10X²⁰cm^-3.12SrO⋅Al2O3 phase was decompose SrO⋅Al2O3 and 3SrO⋅Al2O3 over 1000°C.

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Polycrystalline 12CaOAl₂O₃ thin films have been grown on single crystal substrates of MgO by pulsed laser deposition (PLD) technique. Optical band gap was estimated to be 5.7 eV.

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Thermal change of an ecological carbon/carbon hybrid material, wood ceramics (WC) prepared from apple pomace, was studied for the first time by mainly using TG-DTA/MS. Dehydration and release of gaseous carbon dioxide (CO2) occur in temperatures lower than ca. 483K; CO₂ and fragments of phenol resin are mainly found up to 943K; at higher temperatures, gaseous CO is discharged, showing progressive carbonation. Carbonized materials and Woodceramics sintered at 1073K shows maximum evolution of adsorbed gases, and show dehydration immediately followed by CO2 evolution at temperatures lower than 483 K; but Woodceramics is thermally more stable than carbonized materials and the gas evolution peak temperatures are higher for products sintered at higher temperatures.

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Simultaneous measurement of TG-DTA and EGA using mass spectrometry (TG-DTA/MS) revealed that thermal change of cedar-based wood ceramics (WC) in helium was initiated by dehydration, which was followed by several decomposition steps. Total mass loss increased with increasing particle size of the sample. Evolution of CO2 was detected mainly throughout the reaction, while benzene, phenol and xylene were slightly observed in the middle temperature region (∼600°C), attributed to adsorbed decomposition species. Gaseous CO was distinct at higher temperatures. The results suggested that the ability of gas absorption of WC is higher than that of carbonized cedar, and characteristic water adsorption effect is observed for coarser samples. Furthermore, the results imply the presence of different gas adsorption sites.

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Removal of electrolytes from aqueous solutions (2.5X10-4 mol/l∼0.01 mol/l of Mg(NO3)2) was carried out by using an electric double layer capacitor with activated carbon fiber cloth (ACFC) polarizable electrodes. Without charging the capacitor, it was difficult to remove Mg(NO3)2 from the solutions. On the other hand, Mg(NO3)2 was effectively removed, especially in low concentrations of Mg(NO3)2, by charging the capacitor to 1.0 V.

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In order to decrease the total amount of landfilled industrial waste by reuse and/or recycling of the industrial solid waste, the porous ceramics with activated carbon species was prepared from industrial solid wastes and its characterization were investigated. Sludge from gravel plant and sawdust from wood plant were used as the industrial solid wastes (ISW). The molded body after kneading these ISW's with bentonite and activator were calcined at 850°C for 1 hour under N2 atmosphere. Black powder after grinding the calcined body with added activator exhibited a high adsorption ability for methylene blue molecules in liquid phase, and possessed large specific surface area. This result indicates that the carbonized sawdust can be efficiently activated by the activator during calcination process, even though the ISW's was used as source materials.

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In order to develop various reuse of old paper, activated carbons were prepared from corrugated paper by direct activation method using steam. The porous properties of the products were investigated by N2 adsorption method. The N2 isotherms show that micropores were developed as well as mesopores. The products activated at lower temperature for longer time showed higher specific surface area and higher yield, which is suitable to raise mechanical strength.

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