A couple of Rietveld-analysis programs, RIETAN, for angle-dispersive diffraction and time-of-flight neutron diffraction have been extensively used for structural studies of many compounds. The history of their developments is briefly reviewed. The latest versions, RIETAN-2000 for angle-dispersive diffraction and RIETAN-2001T for the Vega and Sirius diffractometers at KENS have a practical feature of partial profile relaxation. In this technique, primary profile parameters of (nearly) isolated reflections can be individually refined independent of secondary profile parameters. It was combined with split profile functions to improve fits between observed and calculated patterns, particularly in samples exhibiting anisotropic profile broadening and reflections with very large lattice-plane spacings. RIETAN-2000 and our own program for the maximum-entropy method (MEM), PRIMA, were virtually integrated into a structure-refinement system, REMEDY, whereby the pattern calculated from structure factors obtained by MEM is fit to the whole observed pattern. `Observed' structure factors estimated at the end of the whole-pattern fitting are analyzed again by MEM. Whole-pattern fitting and MEM analysis are alternately repeated until R factors in the former no longer decrease. Applications of this technology to three inorganic compounds having highly disordered structures are demonstrated, showing its excellent performance and effectiveness.

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There are still several problems to be scientifically solved for the ``conventional''sol-gel ceramic coating technique to be utilized in industrial scale. Based on the recognition, the author's group studied the stress evolution and crack formation in gel-derived films and the evolution of radiative striations in spin-coating films. Possible modification of the sol-gel technique has also been made for realizing thicker films via non-cycled deposition. First, the residual stress was measured on alkoxide-derived silica and titania films deposited on silica glass substrate. The residual stress increased with increasing heat-treatment temperature due to densification. It was demonstrated that the stress in films is not a simple function of the difference in thermal expansion coefficient between the film and the substrate, but is greatly affected by the processing parameters including the amount of water for hydrolyzing alkoxides and the kinds of the chelating agents. Second, in situ observation was conducted on silica and titania gel films deposited on single crystal silicon substrates. Macroscopic cracking occurred in the heating-up stage, suggesting that the cracks are formed by tensile stress generated in films due to densification. Also, such cracking was found to occur at lower temperatures when the films are thick or heated at lower rates. Third, expecting that organic polymers with amide groups like polyvinylpyrrolidone (PVP) can promote structural relaxation and can suppress stress evolution on heating, PVP-assisted sol-gel thin film deposition was proposed. Incorporating PVP in coating solutions, crack-free ceramic thin films including BaTiO₃, PZT and BaBi₄Ti₄O₁₅ films over submicron or micron in thickness could be prepared via non-cycled deposition. Finally, radiative striations were quantitatively evaluated by surface roughness measurement, and the effects of the processing parameters on striation evolution were studied. The height and spacing of striations were found to be increased with decreasing spinning rate and with increasing sol viscosity. Striations were also found to be formed even without the rotation of the substrate, suggesting that the substrate rotation is not a necessary condition for evolution of striations. On the assumption that the mechanism of the evolution of striations is the same irrespective of the presence or absence of the substrate rotation, in situ observation of the evolution of striations was conducted on a sol layer placed on a stationary substrate. It was observed that striations are formed on solvent evaporation after the sol was spread, not on proceeding of the sol front towards the outer.

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60CaO·30P₂O₅·7Na₂O·3TiO₂ glass-ceramic, which consists of crystalline β-Ca₃(PO₄)₂ and β-Ca₂P₂O₇ phases with a small amount of glassy calcium phosphate phase including sodium and titanium ions, has an apatite-forming ability in simulated body fluid (SBF) at 37°C; on the glass-ceramic, the bonelike apatite forms after 20 days of soaking in SBF. In the present work, the apatite-forming ability in SBF of the glass-ceramic was enhanced by a hydrothermal treatment in water at 140°C for 1h; the glass-ceramic was completely covered with bonelike apatite after 10 days of soaking. The phosphate glassy phase around the surface dissolved drastically during the treatment but almost no titanium ion dissolved. X-ray photoelectron spectroscopic analysis implied that the hydrated titania groups, which may induce nucleation of the apatite, form newly around the surface during the treatment.

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We have examined the influence of additives to coating sols, such as water, aldehyde, acetal, ester, carboxylic acid and several kinds of diols on the surface roughness of coating films with a ``concave-convex'' surface, derived from the mixtures of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES). Among the additives tested, n-butyric acid and diols such as ethylene glycol, propanediol, butanediol or pentanediol increased the surface roughness of the resultant films. It was also found that the surface roughness (R_a) was controlled by changing the concentration of the additives and that the diols showed different effects among the isomers. Among normal butanediols, 1,4-butanediol of methylene-type diol was the most effective to increase R_a of the films, followed by 1,3-butanediol and then by 1,2-butanediol.

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Novel silica glass single-mode optical fibers (SMFs) directly bonded with a low-expansion glass-ceramic jacket have been fabricated. Jacketing was performed by drawing a Li₂O-Al₂O₃-SiO₂ glass-ceramic preform. The SMF with glass-ceramic jacket (GC-SMF) exhibited a bending strength of 750MPa, suitable for optical connecting components. The dimensional accuracy of GC-SMF with a 0.56-mm-thick glass-ceramic jacket was within the range of 1.4μm in both roundness and concentricity, which are also adequate for optical connecting components. GC-SMF showed single-mode optical propagation with a small propagation loss at a wavelength of 1.3μm. The optical performance of GC-SMF was maintained even after heat treatment at 750°C for 1h, showing excellent high-temperature resistance, approximately 500°C higher than that of conventional SMF assemblies with organic adhesives. GC-SMF is regarded as a promising candidate for high-temperature-resistant optical connecting components, which are applicable to recently developed high-power optical communication systems.

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This study concerns with the adsorption of pathogenic substances on highly blood-compatible titania and the adsorption mechanism. Titania was prepared through a sol-gel procedure by hydrolyzing tetraethylorthotitanate and calcining up to 705°C for 3h. Pore size distribution and surface charge density were measured as a function of calcining temperature. Adsorption of bilirubin, as a typical pathogenic substance, as well as albumin on the titania powder was studied. Bilirubin was adsorbed either in 4 to 8-nm pores or on the surface with a higher positive charge. Thus, either entrapping bilirubin in the pores or electrostatic interaction between bilirubin and titania surface was effective for the adsorption of bilirubin. The titania powder adsorbed a greater amount of bilirubin than the anion-exchange resin used in clinics, hence they have potential for blood purification therapy.

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Tl_2-xBa₂Ca₂Cu_3+zO_y (Tl-2223 system) superconducting oxides with various Tl contents and Cu contents were prepared. We investigated the relation between crystal structure and superconducting property dependence of Tl and Cu content. First, we obtained an almost single-phase material at a Tl content 2-x=1.7 and the Tl-2223 phase remained the main phase in the region of 2-x≥0.631 of Tl_2-xBa₂Ca₂Cu₃O_y. T_c was about 120K for the Tl-2223 in a wide range of 0.631≤2-x≤1.761. Second, we obtained a single-phase at 2-x=1.777 and Cu content 3+z=3.284 of Tl_2-xBa₂Ca₂Cu_3+zO_y. The T_c(zero) dependence of Cu/Tl ratio, showed a maximum value of 122K at Cu/Tl ratio=2.026. Based on results of crystal structure refinements by powder neutron diffraction, it was found that the change in bond length and angle dependence of average Cu valence were similar for Tl_2-xBa₂Ca₂Cu₃O_y and Tl_2-xBa₂Ca₂Cu_3+zO_y. However, the structural change dependence on average Cu valence of Tl_2-xBa₂Ca₂Cu₃O_y was large as compared to that of Tl_2-xBa₂Ca₂Cu_3+zO_y, because the substitution of Cu for Tl causes only a limited distortion of the crystal structure. Moreover, the T_c dependence on average Cu valence shows the same tendency for Tl_2-xBa₂Ca₂Cu₃O_y and Tl_2-xBa₂Ca₂Cu_3+zO_y. T_c(zero) reached the highest value of 122K at-2.07 of average Cu valence. T_c was related to the average Cu valence and flatness of the CuO₂ and BaO planes.

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A silicon nitride sintered body with uni-directionally aligned β-Si₃N₄ elongated grains (UA-SN) was fabricated and the effect of microstructural anisotropy on wear properties was investigated. Block-on-Ring tests without lubricants were carried out using the UA-SN as block specimens and commercially supplied Si₃N₄ as ring specimens. In addition, scratch tests were also carried out using a diamond stylus having 25μm of tip radius with the normal load increasing continuously up to 1.47N. For UA-SN, tribological properties were evaluated in three directions with respect to the grain alignment; in the direction normal to the grain alignment on the plane normal to the grain alignment (N), and in the direction parallel (L) to and perpendicular (T) to the grain alignment in the side plane. The N direction exhibited the highest wear resistance, and the worn surface of this plane was quite smooth, in contrast to the other specimens whose surfaces were irregular owing to grain removing. For the scratch test, there was an inflexion point in friction force during increasing load for each specimen. The starting states of wear, such as grain removing, were observed at this point and the loads at this point among specimens correlated with the result of wear resistance obtained from wear tests. Microfracture of the silicon nitride induced by scratching started at the grain boundary as microcracks. Wear was caused by subsequent grain removing following propagation and combination of these microcracks. It is suggested that the high wear resistance achieved in the plane normal to the grain alignment is attributable to the inhibition of crack propagation along the sliding surface by the stacked elongated grains normal to the sliding surface.

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Ammonium hydroxide was used at 10°C as the precipitant to synthesize thin flakes of yttrium hydroxide, agglomerating in a manner resembling houses of card. Onemol% to 50mol% of ammonium sulfate was added to the yttrium hydroxide. Doping of sulfate ion resulted in yttria particles with round edges, in contrast to undoped yttria particles with sharp edges. The amount of doped sulfer was reduced to S/Y=10^-3 by calcinations at 1100°C, and to trace by sintering at 1700°C. Doping of 10mol% of ammonium sulfate resulted in the maximum transparency in those of the yttria ceramics. Transparency of the yttria ceramics related to brittleness of agglomerate of the calcined powder which was evaluated by collapsing tendency of the agglomerates by ultrasonic dispersion.

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In order to investigate the glass strength subjected shock tube loading, characteristics of the shock wave pressure generated in a vertical shock tube with 300mm×300mm square and an enhanced stress measurement technique of 100kHz frequency have been studied. Value of shock wave loading to glass specimen could be estimated from that of pressure behind the reflected shock wave measured by the pressure transducers mounted at the sidewall of the shock tube. Radical increase and monotonic decay were observed in the recorded profile of the shock wave, and generated stress could be measured with a high accuracy.

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Stress generation by shock wave on a 300mm×300mm float glass specimen was investigated. Stresses in float glass plate increased to a maximum value impulsively, and decayed accompanied by a periodical oscillatory pattern. The stress values σ so far generated can be written in the following form of time t and thickness d using 4 parameters, σ(t, d*)=C_dsinωt·exp{-λ(t-π/2ω)}+C_s. In these 4 parameters, C_d and C_s are shown as a factor of Mach number by normalizing with glass thickness, and λ and ω are dependent on glass thickness.

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Test pieces of a tetragonal zirconia polycrystal containing 3mol% yttria were deformed in tension under superplastic conditions in air to pre-determined nominal strains ranging from 0.0 to 200%. The X-ray diffraction experiments were conducted on surface regions of gauge sections of the deformed test pieces to investigate phase transformation and domain switching behaviors that might occur during the superplastic deformation. The measured X-ray patterns were analyzed using a Rietveld refinement method. As a result: (i) Reflections from monoclinic (m) phase were not observed in the X-ray patterns, indicating that tetragonal (t) to m phase transformation might not occur during superplastic deformation under the above condition. Meanwhile, the fraction of cubic (c) phase seemed to decrease with increasing strain. (ii) Traces of ferroelastic domain switching were observed in the X-ray patterns of the deformed specimens. The switching amount was found to depend on flow stress and deformation amount. The tetragonal axis ratio (c/a) along the scattering vector used in this study was found to decrease with increasing the switching amount.

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Alumina bicrystals were successfully fabricated by hot joining technique at 1500°C in air to obtain two kinds of [0001] symmetrical tilt grain boundaries, i.e., Σ7 and Σ31. Their atomic structures and high-temperature deformation behaviors were investigated by high resolution transmission electron microscopy (HRTEM) and compressive creep tests, respectively. HRTEM observation revealed that grain boundaries in the alumina bicrystals were directly bonded without any amorphous phases, and that the atomic structure of Σ7 was different from that of Σ31 due to their geometrical misorientation and grain boundary planes. It was also found that grain boundary sliding rate in Σ7 was much smaller than that in Σ31. These results indicate that grain boundary sliding strongly depends on geometrical coherency and atomic structure of grain boundaries.

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In order to obtain a material with excellent sliding properties under normal oil-lubrication, several kinds of basic experiments on both raw powders and sintered bodies, as follows: 1) measurement of the degree of adhesion of calcium-sulphonate to the surface of powders and contact angle measurement of oil on sintered bodies were done. And those experiments revealed that CeO₂ added Al₂O₃/ZrO₂ ceramics showed the most promising performance, 2) measurement of friction coefficient showed that CeO₂10mass% added Al₂O₃/ZrO₂ had a much lower frictional coefficient than Si₃N₄ based ceramics and cast iron under mixed lubricating conditions. It was confirmed that CeO₂ added Al₂O₃/ZrO₂ ceramics was less sensitive to calcium-sulphonate, which is a widely used detergent-dispersant ingredient.

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Films were prepared on stainless steel, aluminum alloy and glass substrates using silica precursor solution containing copper ions. The thickness of the film coating was about 0.1-0.2μm. The corrosion resistance was greatly improved by PVB-containing silica coating onto stainless steel. An antimicrobial test based on Japanese Industrial Standard (JIS Z 2801) indicates that the antimicrobial activity (R) of a control silica coating is R=0.0, whereas R=5.0 for the copper-containing silica coating (Cu: 6.1×10^-3mol/L). JIS defines antimicrobial activity as positive when R is more than 2.0. A submicron thick copper-containing silica coating clearly impacts corrosion resistance and antimicrobial activity to a material surface without any heat treatment.

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Particle oriented bismuth titanate ceramics with high density was successfully developed by a novel processing involving a high magnetic field. The b axes of fine powder particles were oriented perpendicular to the applied magnetic field in the green compact. High density was achieved by subsequent sintering. The microstructure showed highly anisotropic structure.

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Frictional properties of Fe₃O₄-Al₂O₃ composite ceramics were investigated under lubricating conditions, and the following results were obtained; 1) when fresh lubricant oil was used, Fe₃O₄-Al₂O₃ and cast iron had similarity in their frictional properties, while those materials have different hardness, 2) on the other hand, in the case of deteriorated oil or detergents-dispersants free oil, the frictional behaviors of the two above materials were quite different. The range of fluid lubricating conditions for Fe₃O₄-Al₂O₃ was enlarged and its frictional coefficient under mixed lubricating conditions was much lower than that of cast iron. And the dependence of frictional properties on the oil characteristics is supposed to be related to the detergent-dispersant, one of the agents in lubricant oil.

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