ZnO rods were synthesized from Zn ingot under various pressures of mixed gas of Ar/O₂(90/10 mass%) from 60 to 95 kPa. ZnO rods were grown on both the surface of the Zn ingot and the vertically mounted quartz substrate. ZnO dots were at first developed on the grain boundaries of the Zn ingot and continued to grow as rods. ZnO rods were also developed on the quartz substrate with a thickness ~1.5 times those of rods grown on the ingots. ZnO nanorods of ~100 nm in diameter were vertically grown with good uniformity on the quartz substrate.

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Particular attention was paid to the “aging” of starting solution for synthesis of spherical silica by a controlled hydrolysis of alkoxide. Two starting solutions, i.e., an ethanol solution of tetraethylorthosilicate (TEOS) and an ethanol solution of ammonia water, were aged and then mixed to synthesize spheres. Sufficient aging (~a week) of the starting solutions resulted in larger sphere size and higher monodispersibility. We infer here that solute molecules are not homogeneously dispersed in the as-dissolved solution even though they appear to be clearly dissolved.

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Surface modification of diamond powder (5-12 μm) was achieved using a water-saturated solution of formaldehyde. The effects of the reaction temperature and time were studied. The diamond surface was characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Four chemical structures; epoxy (-C-O-C-), aliphatic ether (-C-O-C-) as well as methyl (-CH₃) and methyne (-CH) bands were identified in the diamond surface after the treatment. The total intensity of the bands increases proportionally by augmenting the treatment time and temperature. The absorbance intensity of all bands correlates linearly. An activation energy of 34.7 kJ mol^-1 was obtained, that is in the range of a chemisorption reaction energy. From the results it is concluded that methyl formate (HCOOCH₃) was chemisorbed on the diamond surface to a carbon with two unsaturated valences.

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Single phase Bi₂(Sr_1-xCa_x)₂(Ca_1-yY_y)Cu₂O_δ is successfully prepared in the range of 0≤x≤0.8 and 0≤y≤0.6 by a solid state reaction in air. The optimal sintering temperature for forming the single phase is reduced from 875°C to 800°C with substitution of Y in the Ca site or with increased Ca in the Sr site. The lattice parameter c reduced from 3.081 to 3.017 nm by substituting Ca with Y and/or Sr with Ca. Bi₂(Sr_1.0Ca_0.0)₂(Ca_0.8Y_0.2)Cu₂O_δ, is superconducting after heat treatment either in Ar or O₂ while the phases Bi₂(Sr_0.6Ca_0.4)₂(Ca_0.8Y_0.2)Cu₂O_δ, Bi₂(Sr_1.0Ca_0.0)₂(Ca_0.4Y_0.6)Cu₂O_δ and Bi₂(Sr_0.4Ca_0.6)₂(Ca_0.4Y_0.6)Cu₂O_δ are superconducting only after oxygenation. The oxygen stability and optimum heat treatment temperature for superconductivity depend on the Sr/Ca and Ca/Y ratios in Bi₂(Sr_1-xCa_x)₂(Ca_1-yY_y)Cu₂O_δ.

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In order to improve the sinterability of LaCrO₃, which is one of candidate materials for interconnector of Solid Oxide Fuel Cell, the effect of sintering in reducing atmosphere and Ti substitution of Cr on the sinterability was investigated. Judging from the sintering temperature dependence of density, both of sintering in reducing atmosphere and Ti substitution of Cr improved the sinterability of LaCrO₃. Compared with the sample sintered in air, sinterability of the samples sintered in reducing atmosphere was most promoted in a case of small amount of Ti substitution. X-ray photoelectron spectroscopy analysis of the surface of the sample revealed an existence of Cr⁶⁺ ion in LaCrO₃ sintered in air. On the contrary, Cr⁶⁺ ion was not obviously observed in LaCrO₃ sintered in reducing atmosphere as well as LaCr_0.7Ti_0.3O₃ sintered in air and in reducing atmosphere. Therefore, Ti substitution of Cr and sintering in reducing atmosphere have the same effect on suppression of CrO₃ generation, which is harmful for sintering of LaCrO₃. Microstructure observation revealed that grain growth of LaCrO₃ sintered in air was pronounced, while that of LaCrO₃ sintered in reducing atmosphere and LaCr_0.8Ti_0.2O₃ sintered in air was negligible. Activation energy for shrinkage of LaCrO₃ and LaCr_0.95Ti_0.05O₃ sintered in reducing atmosphere was 262 kJ•mol^-1 and 153 kJ•mol^-1, While that of LaCr_0.8Ti_0.2O₃ sintered in air was greater than those of LaCrO₃ and LaCr_0.95Ti_0.05O₃ sintered in reducing atmosphere. The effect of Ti substitution on sintering of LaCrO₃ should be different in rate controlling process from the effect of sintering under reducing atmosphere.

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Zeolite A compacts were directly prepared from allophane compacts by hydrothermal reaction with NaOH solution. With increasing concentration of NaOH solution formation rate of zeolite A from allophane increased and crystal size of formed zeolite A decreased. Higher reaction temperature resulted in increases in formation rate and crystal size of zeolite A. Spaces are formed by the aggregated zeolite A crystals and are the macro pore which shows narrow size distribution. The macro pore size increased linearly with an increase in the crystal size of zeolite A.

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Calcium hydrogenphosphate dihydrate (DCPD) efficiently reacts with fluoride ion in a solution to form fluorapatite (FAp). In this paper, the reaction of DCPD with a solution containing a small amount of fluoride was investigated. 2.0 g of DCPD was added to 2.0 dm³ of solution containing 20 mg dm^-3 of fluoride, and then reacted for various periods. We observed a “lag time” within which the concentration of fluoride ions in the solution did not change. After this lag time, the fluoride ion concentration in the solution quickly decreased. From the results of powder X-ray diffraction, fied emmision-scanning electron microscopy (FE-SEM) observation and chemical analysis of the solid phase, DCPD did not directly react with the fluoride ions, but formed a nano-scale particle on the surface of the DCPD particles, and then reacted with the fluoride to form calcium deficient FAp. From these results, the lag time could be considered to be the time needed to form nano-scale particles on the surface of the DCPD particles. It was also found that the amount of fluoride reactable with DCPD was larger at lower temperatures.

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A novel synthetic route to the preparation of lithium metagallate (LiGaO₂) crystals from Ga₂O₃ and Li₃N under condition milder than conventional methods has been explored. We have found that a reaction of Ga₂O₃ and Li₃N at temperatures ranging from 500°C and 800°C in chloride fluxes yields formation of LiGaO₂ single crystals. This technique has applicability to the synthesis of LiGaO₂ crystals, which are known to be suitable substrates for epitaxial growth of GaN.

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We have fabricated a photonic crystal rod (PCR), which is a novel optical connecting component with a two-dimensional photonic crystal structure, by drawing a preform made of a multicomponent alkali-borosilicate glass. A hot vacuum (725°C, 10 hPa) stacking method was developed for the fabrication of the preform, which enables self-organization of the inner structure of the preform. PCRs with sub-micrometer dimensional accuracy were successfully fabricated by drawing the preform at 820°C, which is a much lower temperature than that used for the drawing of silica glass. The PCRs showed single-mode optical propagation at both wavelengths of 633 and 1550 nm with mode field diameters (MFDs) of 23.1 and 33.4 μm, respectively. The bending strength of the PCR reached 850 MPa after ion-exchange treatment. PCR is expected to be a candidate for precision, high-strength, endlessly single-mode novel optical connecting components with large MFDs.

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Hot-gas corrosion behavior of Si₃N₄ against high speed combustion gas was investigated by optical microscopy observation. A city gas (13A) with the composition of CH₄: 88.60, C₃H₈: 3.20, C₂H₆: 5.09 and C₄H₁₀: 2.86 in vol%, was used as fuel. Three Si₃N₄ test bars with the size of 4 mm×4 mm×80 mm were used for each exposing run. The exposure was carried out in combustion gas temperature of around 1400°C with the current velocity of about 190 m/s. The exposing time was totally 60 h (7-8 h in a day). At the earlier stage, after 8-16 h exposure, thin and glassy oxide layer was formed on the surface of Si₃N₄. The oxide layer changed to a powdery substance with elapsing exposure time and the surface was fully covered by powdery oxide after ≈24 h. The powdery oxide was only attached on the surface very loosely and it was easily removed by soft touch. White spots on particles from the burner side which consisted of a larger amount of glassy phase, also changed to powder and fade away with elapsing time. At an earlier stage, after 8-16 h exposure, the specimens showed relatively lower weight loss compared to that detected after around 24 h exposure. It is considered that the decreasing weight may be divided into two stages according to the change of ratio in weight loss before and after each exposure. Thus, in the earlier stage, it can be assumed that vaporizing of Si, O and N₂ from the surface grassy phase mainly takes place, while in the later stage, the main process is the removment of powdery oxide in addition to vaporization of Si, O and N₂.

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Monodispersed yttria stabilized ZrO₂ nanocrystals were synthesized from zirconium oxyhydrate sols chelated with diglycol. The particle growth kinetics as a function of the concentration of ZrOCl₂ solution and molar ratio of ZrOCl₂: diglycol was investigated. It was demonstrated that the rate constant of the particle growth and the final particle size increased with increasing the concentration of ZrOCl₂ solution and decreasing the molar ratio of ZrOCl₂: diglycol. High-resolution transmission electron microscopy (HRTEM) as well as powder X-ray diffraction showed that the as-synthesized nanoparticles were well crystalline.

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The experimental results obtained in this study demonstrated the feasibility of improving the bending strength of rough-ground Si₃N₄ coated with polymer ceramic precursors and subsequently pyrolyzing the polymer coating. Double coating with 10 mass% polycyclomthylsilazane solution provided the smooth surface, while microcracks were still existence. Increase in the strength of 150 MPa was achievable via polymer coating and pyrolyzing while the improvement in the strength variation in terms of the Weibull modulus was insignificant.

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