The effects of sintering atmosphere and sintering time on gas emission behavior during fracture of high-purity Al₂O₃ were investigated under ultrahigh vacuum using a mass spectrometer to examine the behavior of gases in the material. The gas in the sintering atmosphere was predominantly emitted at the moment of fracture for all specimens. The total amount of gas emitted from a specimen sintered in O₂ was less than that of a specimen sintered in air or Ar, showing that the mobility of O₂ in the material was much higher than that of N₂ or Ar. During prolonged sintering, the density of specimens decreased, while the amount of emitted gas increased. Entrapped gases in the sintered body were concluded to bring about the density decrease during grain growth.

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The three-point bending strength of two-dimensional SiC fiber-reinforced SiC composites (SiC/SiC_f) fabricated by chemical vapor infiltration (CVI) method and polymer infiltration and pyrolysis (PIP) method was measured at room and high temperatures up to 1600°C and the fracture behavior was investigated. The maximum strength of the CVI-SiC/SiC_f composite with carbon-coated Hi-Nicalon cloth was maintained at around 200MPa up to 1600°C. The fracture behavior of the CVI-SiC/SiC_f composite showed non-brittle characteristics with fiber pull-out up to 1500°C, whereas it showed brittle fracture at 1600°C. On the other hand, the maximum strength of the PIP-SiC/SiC_f composite increased gradually from 40 to 70MPa with increasing test temperature, due to the crystallization of the matrix. The PIP-SiC/SiC_f composite with carbon-coated Hi-Nicalon had higher strength and fracture energy than that with non-coated Hi-Nicalon. The PIP-SiC/SiC_f composite with carbon-coated Hi-Nicalon showed non-brittle fracture up to 1400°C, whereas that with non-coated Hi-Nicalon showed almost brittle fracture at room and high temperatures, except at 1400°C. The PIP-SiC/SiC_f composite significantly differed from the CVI-SiC/SiC_f composite in maximum strength. This could be mainly explained by bulk density.

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Solid-gas reactions of Si₃N₄ ceramics were investigated with emphasis on the mass loss during sintering under various sagger conditions. A Si₃N₄ powder compact without sintering aids was heat-treated at 2023K for 0 to 8h under 0.1 and 1MPa N₂ adopting three sagger conditions: a Si₃N₄ powder bed, without a powder bed in BN sagger, and without a powder bed in C sagger, and Si₃N₄ with addition of 5 mass% Y₂O₃ and 3 mass% Al₂O₃ was sintered at 2023K for 0 to 16 h under 0.1 to 100MPa N₂ adopting four sagger conditions: a 50 mass% Si₃N₄/50 mass% BN powder bed, without a powder bed in BN sagger, a C powder bed, and without a powder bed in C sagger. In C sagger, the principal mass loss reaction was that of Si₃N₄ (s) with CO(g): 2Si₃N₄(s)+3CO(g)→6SiO(g)+4N₂(g). In BN sagger, the principal mass loss reaction was that of Si₃N₄(s) with SiO₂(l): Si₃N₄(s)+3SiO₂(l)→6SiO(g)+N₂(g). When SiO(g) generated from the sample and the powder bed (based on the above reaction between Si₃N₄(s) and SiO₂(l)) was exhausted, the mass loss reaction of Si₃N₄(s) with CO(g) occurred even in BN sagger, which diffused in through a gap of the sagger.

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Raman and nuclear magnetic resonance (NMR) spectra were measured for GaO_3/2-TeO₂ glasses. Compositional dependence of Raman band intensities reveals that the coordination state of tellurium changes from TeO₄ trigonal bipyramid to TeO₃₊₁ polyhedron and TeO₃ trigonal pyramid. ⁷¹Ga magic angle spinning NMR spectra indicate that most of galliums form GaO₆ octahedra in 10GaO_3/2⋅90TeO₂ glass and tetrahedral and octahedral galliums coexist in 30GaO_3/2⋅70TeO₂ glass. The change in coordination state of galliums depending on composition is discussed.

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Large bodies of opaque silica glass were fabricated by slip casting and sintering. The raw material was highly pure synthetic silica powders. The slip was prepared without adding any binder. Three types of powders with different particle sizes were used to examine the influence of particle size on slip casting. A significant influence was found, and large green compacts could be obtained only by using a powder with an average particle size of 5μm. Three types of mold materials, plaster, plastic resin and mixtures of both, were tested. The plaster mold fabricated slip casting operation, but caused Ca contamination (about 3ppm) into the resultant glass. After slip casting, the compacts were sintered at 1800°C in nitrogen atmosphere. According to this process, a large ring (φ400mm) of opaque silica glass could be fabricated without any appreciable distortion.

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X-ray spectrometry and X-ray diffraction (XRD) studies indicate that yellow sludge containing hydroxides of several hazardous heavy metal ions, i.e., Cr, Fe, Cu, Zn and Pb, has an amorphous structure. The XRD and ⁵⁷Fe Mössbauer studies of the yellow sludge indicate the formation of a small amount of γ-FeOOH particles. Heavy metal waste glass of a light green color could be prepared by melting the yellow sludge together with synthetic soda-lime silicate glass of a light brown color. Additional waste glass could be prepared from a glass bottle for commercial drinks. Leaching test for Zn and Fe with the acid rain simulant (pH 3.5), which was prepared from a nearly equal amount of HNO₃ (pH 3.5) and H₂SO₄ solution (pH 3.5), proved that the waste glass has higher chemical durability than the sludge adsorbed on “diatomaceous earth.” These results indicate that soda-lime silicate glass is a very effective medium for stable solidification of heavy metal ions, and that the “glass wastes” can be reused for this purpose.

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Porous hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂; HAp) ceramics with various porosity values were fabricated by sintering fibrous HAp particles prepared from the aqueous solutions in the Ca(NO₃)₂-(NH₄)₂HPO₄-(NH₂)₂CO-HNO₃ system by the homogeneous precipitation method using urea. The total porosities, total pore volumes, median pore sizes and specific surface areas of the resulting ceramics were controlled in the range of 16.7 to 55.0%, 0.04 to 0.36cm³·g^-1, 0.28 to 0.78μm and 0.29 to 2.90m²·g^-1, respectively, by changing the compaction pressures (20, 30 and 40MPa) and firing temperatures (1000°C, 1100°C, 1200°C and 1300°C). Most of the pores in the resulting ceramics were regarded as the open pores.

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Slips prepared from bimodal size distributed alumina powder mixtures, which consisted of 30% fine powder and 70% coarse powder, were cast. The two average particle sizes of the bimodal distribution were varied. When the difference between the average particle sizes was small, green compacts had a low packing density and uniform packing structure. In this case, the fine and coarse particles were deposited by filtration of gypsum mold, due to the high viscosity of the slips, an insufficient dispersion of the fine particles and the small size of the coarse particles. On the other hand, when the difference between the average particle size was large, green compacts had a high packing density and nonuniform packing structure. In this latter case, the coarse particles were first deposited by sedimentation to form the skeletal structure; then, the fine particles percolated through the voids of the skeletal structure by filtration and were deposited in the voids. On approaching the bottom part of the green compacts, the skeletal structure showed increased density. Since the water absorption rate was slow, the fine particles did not fill the voids sufficiently. As a result, the maximum packing density of 84% was obtained in the bottom part of the green compact. The packing density decreased with increasing distance from the bottom part of the specimen.

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Powder of the cathode material, LiNi_xMn_2-xO₄ (0≤x≤0.2) was prepared by emulsion method and calcined at 800°C for 48h in air. The calcined powder showed a spinel structure and a spherical morphology. The average particle size and the specific surface area were 0.17μm and 34m²/g, respectively. Charge-discharge tests were carried out galvanostatically in a voltage range between 3.0V and 4.5V. The composition of LiNi_0.025Mn_1.975O₄ showed an improved discharge capacity, 123.4mA·h/g and a stable cycle life during charge-discharge cycling. The plateau range near 4.0V became narrow as the amount of nickel increased. Another plateau range was observed near 4.6V which became broader with increasing x.

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SiC-AlN powder was synthesized from a powder mixture of Si, Al and C through direct reaction between the constituent elements, i.e., (1-x)Si+(1-x)C+xAl+(x/2)N₂=(SiC)_1-x(AlN)_x. A green compact of the mixed elemental powders was fired in nitrogen, and a porous compact composed of SiC and AlN and their solid solutions was obtained. This porous compact could be easily pulverized to fine SiC-AlN powder by ball-milling. Ultrafine microstructure with fine grains smaller than 100nm was obtained by hot-isostatic pressing (HIP) of the synthesized powders without external additives. Most grains therein were SiC-AlN solid solutions with compositions close to the nominal mixed ratio. The obtained SiC-AlN ceramic alloys, here referred to as homogeneous solid solutions and their mixture, showed better mechanical properties than SiC and AlN. In particular, high strength, more than twice that of the conventional monolithic SiC, was obtained in the SiC-50 mol% AlN composition mainly because of its ultrafine-grained microstructure. This was also the main reason for the present SiC-AlN ceramic alloys to exhibit ductile deformation at relatively low temperatures.

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Effect of addition of borosilicate glass, quartz and feldspar powders on the sintering characteristics of kaolin and CaCO₃ mixtures was investigated in order to obtain low-temperature sinterable porcelain bodies below 1000°C. Upon heating, CaO reacted with decomposed kaolin at temperatures 800-850°C, and formed metastable amorphous materials. Transiently formed active amorphous materials sintered rapidly between 850°C and 950°C by the viscous flow mechanism to generate glass-like dense ceramics. However these materials had the disadvantage of large shrinkage and thermal deformation prior to crystallization. Addition of borosilicate glass powders decreased the difference in temperature between sintering and crystallization, which improved thermal deformation characteristics of the fired specimens. Addition of quartz powders up to 25mass% yielded dense porcelain bodies consisting of anorthite, wollastonite, gehlenite and quartz crystals. Also, a lower shrinkage and a lower thermal deformation were attained by quartz addition. On the other hand, addition of feldspar powders inhibited the densification of the body, since its addition considerably lowered the crystallization temperature of anorthite below 850°C.

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Al chelate compounds with different carbon chain length were synthesized by reactions of aluminum sec-butoxide with β-ketoesters having different carbon chain length, such as acetoacetic acid ethyl ester (n=2), acetoacetic acid pentyl ester (n=5), acetoacetic acid octyl ester (n=8) and acetoacetic acid oleyl ester (n=18). Silica was modified by aluminum sec-butoxide and these Al chelate compounds (ALK, C2, C5, C8 and C18 respectively). Then the modified silica was dried at 100°C and heated up to 400°C. We studied the influence of carbon chain length on the hydrophilic-hydrophobic property of dried silica by measurement of adsorption amount of water vapor. In addition the surface property of heated silica was studied by measurement of specific surface area and pore size distribution. It was found that the adsorption amount of water vapor on dried silica decreased with increasing the length of carbon chain such as ALK, C2 and C5. Adsorption amount of water vapor was the same on C5, C8 and C18. Porous Al₂O₃ was prepared from ALK and C2 by drying at 100°C by hydrolysis of aluminum sec-butoxide and Al chelate compounds. Porous Al₂O₃ was also prepared by thermal decomposition of Al chelate compounds from C5, C8 and C18 by heating at 200°C. The mechanism of pore formation changed according to the carbon chain length of Al chelate compounds. The porous Al₂O₃ prepared from Al chelate compounds had smaller and more uniform pore size than that prepared from aluminum sec-butoxie.

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SrAl₂O₄ phosphor excited with fluorescent light or sunlight, has been recently reported to be a long-lasting afterglow (AG) phenomenon. However, the AG mechanism has not been clarified yet. In this study, the long-lasting AG mechanism of SrAl₂O₄ phosphors doped with Eu and/or Dy, was investigated on the basis of AG, photoluminescence (PL), and thermoluminescence (TL) measurements after UV or X-ray irradiation. A hole trap is presumed to be ascribed to Sr defects, which increases and is stabilized by a charge compensation behavior upon doping Dy ion. An electron trap probably originates from oxygen defects, as produced by firing in a reductive atmosphere. Furthermore, the role of dopants (Eu, Dy ion) on SrAl₂O₄ phosphor co-doped with Eu and Dy ions, was studied by comparing the luminescence (AG and PL) phenomena with the distribution of dopant in SrAl₂O₄ matrix. Eu ion contributed closely to both the AG and PL behaviors, while the Dy ion contributes only to the AG phenomenon.

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Propagation of a combustion wave during self-propagating high-temperature synthesis of TiC with gas formation was observed in-situ with a high-speed CCD camera. According to this experiment, combustion wave behavior and its relationship with the developed microstructures of products was evaluated. Combustion wave did not propagate uniformly in any of the cases at a microscopic level. Lack of uniformity increased with increasing the size of raw Ti powders and the amount of TiC as a diluent additive, but decreased with the amount of SiC. Heat-treated carbon black results in further degradation of uniformity in wave propagation for the Ti-C, Ti-C-TiC, and Ti-C-SiC systems. Layered structures of the products were strongly affected by such a lack of uniformity. However, the particle diameter of Ti did not strongly affect combustion wave propagation in the Ti-C-Si system, thus, no significant formation of layered structure occured in the products as compared with the Ti-C, Ti-C-TiC or Ti-C-SiC systems. TiC additive decreased the thickness of the reaction zone, while SiC addition increased it. Heterogeneity formation of melt (s) during the synthesis resulted in a more layered structure and brittle products.

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β-Si₃N₄ powders with different particle size, AlN and Y₂O₃ were used as starting materials to fabricate α-SiAlON by hot-pressing. Five mass% of commercial α-SiAlON powder was also added as seeds to these mixtures to increase the formation rate of α-SiAlON. No significant increase in the α-SiAlON content was found by seed addition when coarse β-Si₃N₄ powder was used. However, in samples sintered from fine β-Si₃N₄ powder, the addition of seeds promoted α-SiAlON formation and a content of 100mass% (compared to the 60mass% without seed) could be achieved. When the starting powder β-Si₃N₄ was coarse, large α-SiAlON and β-Si₃N₄ grains were obtained, the residual β-Si₃N₄ phase being located within the α-SiAlON grains also could be found. In principle fine-grained β-Si₃N₄ and α-SiAlON could both form from fine β-Si₃N₄ powder, residual β-Si₃N₄ was hardly deserved within α-SiAlON grains.

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The formation rate and the primary particle size of monoclinic hydrous-zirconia produced by the hydrolysis of ZrOCl₂ solutions with and without an addition of metal chlorides (NaCl, CaCl₂, or AlCl₃), or HCl were measured to clarify the effects of added metal chlorides and HCl on the nucleation and crystal growth processes of hydrous zirconia. Chemical kinetics analyses to which Avrami-Erofeev's equation was applied and X-ray diffraction measurements revealed that the rate constants and the primary particle sizes of hydrous-zirconia, under constant ZrOCl₂ concentration, decreased with increasing concentrations of added metal chloride or HCl. The nucleation and crystal-growth rates of primary particles of hydrous-zirconia were determined by analyzing the relationships between rate constant and primary particle size. The nucleation rate of hydrous-zirconia particles increased slightly increasing concentration of added HCl, but was independent of the kind and the concentration of added metal chlorides. The crystal-growth rate de termined from ZrOCl₂ solutions with added metal chlorides decreased monotonously with increasing Cl^- ion concentration, and was independent of the kind and the concentration of added metal ions. In ZrOCl₂ solutions with added HCl, the crystal-growth rate decreased monotonously with inceasing Cl^- ion concentration, and the decrease tendency was greater than that of ZrOCl₂ solutions with added metal chlorides. This difference in decrease tendency on the crystal-growth rate can a explained by the blocking action on crystal growth of Cl^- ions attracted on the particle surface, through the formation of an electric double layer.

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Bilayer films of Pb(Mg_1/3Nb_2/3)O₃ [PMN]/BaPbO₃ [BPO] were fabricated on MgO (100) substrates by metallo-organic deposition (MOD) method. PMN films crystallized to a perovskite structure by firing above 450°C on BPO. A broad peak at around-10°C was observed in the temperature dependence of the dielectric constant of the PMN film fabricated from a solution containing 20mol% Pb excess and fired at 600°C. The PMN film showed a P-E hysteresis loop with a remanent polarization, P_r=0.03C/m² and a coercive field, E_c=5MV/m at -45°C, despite a very narrow hysteresis loop at room temperature.

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Porous hydroxyapatite (HAp) monoliths synthesized from gypsum mold waste were used for removing lead ions from aqueous solution. The gypsum waste was crushed into small blocks and converted directly to porous HAp pieces in a 0.5mol/dm³ diammonium hydrogen phosphate solution at 55 and 80°C. Porous structures were effected by reaction temperatures. Twenty and 40mg of lead ions were removed from 100cm³ aqueous solution by stirring with 1.0g porous HAp monoliths at pH 3 for 5 to 30min. HAp was dissolved in the pH 3 acidic solution, but Pb-Cl apatite, which was formed from Pb²⁺, PO₄^3- and Cl^-, was stable in the pH 3 acidic solution.

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Effects of addition of montmollironite on the plasticity of kaolinitic clay, Georgia kaolin, was studied by a uniaxial compression test. It was found that the plasticity of Georgia kaolin was affected by the addition of montmorillonite. From the relation of stress-aspect ratio curve appeared by a uniaxial compression test, the relationship between yield point, which represented a fluidity of the plasticity, and water content was studied. It was suggested that the fluidity was improved when montmorillonite was added in Georgia kaolin. When the forming retention of Georgia kaolin added with montmorillonite was compared with that of Georgia kaolin, the forming retention of Georgia kaolin added with montmorillonite was smaller than that of Georgia kaolin. The relationship between the forming retention and the fluidity of Georgia kaolin added with montmorillonite and Georgia kaolin was investigated. The forming retention of paste added montmorillonite in Georgia kaolin was increased when the fluidity value was same. The plasticity of a Georgia kaolin green body added with montmorillonite improved on that of Georgia kaolin green body.

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To investigate the effect of microwave heating on grain growth behavior in silicon nitride ceramics, microwave annealing was carried out using a microwave radiation frequency of 28GHz. A comparative study of silicon nitride annealed by microwave and by conventional heating was done using scanning elec tron microscopy (SEM) observation and image analysis. Results show that microwave annealing is more effective in enhancing the grain growth and in producing the bi-modal microstructure than conventional heating. In particular, the growth along the c-axis was more remarkable due to the local and selective heating of the liquid phase by the microwave.

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This paper has the following key features. Systematic research on the many types of multicomponent (mainly ternary components) glass formation ranges, such as borate, silicate, germanate, vanadate and tellurite systems, revealed the conditions for multicomponent glass formation. Although the conditions for monocomponent glass formation identified by Zachariasen have been acknowledged since 1932, the conditions for multicomponent glass formation were not proposed at that time. Imaoka introduced general rules for the conditions of multicomponent glass formation on the basis of Zachariasen's rule. The adaptability of these conditions was confirmed by later research. Preciously, the glass formation probability of arbitrary compositions had only been judged by the melting method, but the application of general rules by Imaoka allowed predictions for glass formation possible without experimentation, and this allowed tremendous time savings during the planning of glass compositions.
The establishment of multicomponent glass forming conditions clarified, to a certain extent, the relationship between the glass compositions and the glass structure. Therefore, the multicomponent glass forming conditions have been extremely useful in research on material design to predict the relationship between physical properties and the glass structure. Thus, it is now possible to target the research objectives more precisely and save considerable research time. Although not all commercial glass components can be judged by the conditions examined in this study, it is considered to be a reasonable reference for the discussion of commercial glass components.
The above-mentioned features have contributed enormously to the research and technological development of glass.

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