Particle shapes and S-0 bonding states of the products obtained by heating CaS0₃ · 1/2 H₂0at 590 °C, 650 °C and 810 °C in H₂ or N₂ stream have been studied. Particle shapes were observed by SEM, and S-0 bonding states were investigated by FT-IR spectroscopy.
Both in a hydrogen stream and in a nitrogen stream, particle shapes o f the products were similar. The products obtained by heating up to 590 °C and up to 650 °C were sphere-like particles consisted of plate-like ones, and particle size was in a range of 3-5 μm. The products obtained by heating up to 810 °C were sphere-like particles, on which granular ones formed.
S-O bonding states of the products obtained by heating up to 590 °C were similar. In the product obtained by heating up to 650 °C in a hydrogen stream, more kinds of S-O bonding states existed than that in the products obtained in a nitrogen stream. It was found that similar S-O bonding states of the products were formed again at 810 °C.

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Glycothermal treatment of lanthanum acetate sesquihydrate in 1, 4-butanediol at 300 °C was examined and found to afford lanthanum diacetate hydroxide (La(CH₃COO)₂(OH)), which was confirmed by ¹³C-NMR spectrum (Fig.5), IR spectrum(Fig.4), elemental analysis (Table 2), and thermal analysis.

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Carbon powders dispersed uniformly with cobaltferrite particles were successfully synthesized by pressure pyrolysis of vinylferrocene-cobaltocene derivative-divinylbenzene in the Presence of water below 650 °C at 125 MPa with their high yield and control of morphology of resultant carbon. The amount of cobaltferrite decreased markedly in the carbon matrix formed at 700 °C, since cobaltferrite was reduced to cobalt oxide and wustite by excess carbon. The size of carbon particles was about O.5 μm in diameter at 600 °C and 2.0 μm at 700 °C. The morphology of carbon was dependent upon the pyrolysis temperature and the concentration of metal in a starting copolymer. The morphology of carbon changed from coalescing polyhedra to spherulites with increasing pyrolysis temperature from 600 °C to 700 °C. The size of metal oxide particles which were finely dispersed in carbon synthesized at 600 °C was about 30 nm, which increased with pyrolysis temperature. The saturation magnetization and the coercive force of cobaltferrite-dispersed carbon prepared at 600 °C and 125 MPa were 4.8 emu/g and 2 k0e, respectively.

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Silicon carbide-silicon carbide whisker composites (SiC-SiC(w)) were fabricated by pyrolysis of polycarbosilane (PCS), which was transformed to the SiC matrix by burning. Three kinds of SiC(w) with different diameters whose surfaces were treated with silane-coupling reagent, and PCS ground to less than 500 μm in diameter were used as raw materials.

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Polycarbosilane (PC) has been used as precursor for silicon carbide fiber. Industrially, the fiber is produced by heat-treatment of the melt-spun and cured PC fiber. PC fiber is cured by oxidation, so the SiC fiber properties are influenced enormously by oxygen introduced, especially at high temperature. Clarification of the oxidation mechanism of PC makes possible to controll the high temperature properties of the SiC fiber.

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The effect of titanium in Si-Ti-C-0 fibre on its oxidation resistance was investigated by comparing with the resistance of Si-C-0 fibre. The Si-Ti-C-0 fibre was synthsized by heat treatment of cured fibre of polycarbosilane containing titanoxane, while the Si-C-0 fibre was synthsized by heat treatment of cured polycarbosilane fibre.

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The spherical particles of manganese(II) carbonate were prepared by “Interfacial Reaction Method”, in which the manganese(1I) carbonate was formed by the reaction of manganese (II) salts aqueous solution emulsified in benzene with carbonate salts solution. Some manganese(II) salts (MnCl₂, MnSO₄, Mn(NO₃)₂) and some carbonate salts (NaHCO₃, Na₂CO₃, K₂CO₃) were used in order to make, clear the difference of formation of spherical particles by the kinds of salts. The particle size distributions, DTA-TG curves, X-ray diffraction patterns, specific surface areas and pore volume distributions were measured to clarify the properties of the spherical particles.

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Anatase, a crystal form of TiO₂, is supposed to work as a photocatalyst in near UV region. In order to make it more active, chemical reduction methods have been applied to TiO₂ by many researchers. In the present work, the difference between two reducing methods, namely, reducing anatase in H₂ atmosphere and reducing anatase in ethanol atmosphere has been studied. The magnetic properties have been studied by a magnetization meter and by an ESR instrument. The results seem to indicate that in H₂ atmosphere O^2-ion in the lattice is converted to OH^- and then to an anion vacancy while in ethanol atmosphere it is converted to ^-OEt, and then to ·OEt. The relation between the concentration of the paramagnetic species and the photocatalytic activities of these two differently treated catalysts has shown that in the ehtanol treated catalyst those two properties are in a parallel relation while in the H₂ treated catalyst those two properties are in a reverse relation.

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Peroxo-polytungstate anion, formed by the direct raction of metallic tungsten powder with hydrogen peroxide, was precipitated as its salts with relatively large cations such as K⁺, Rb⁺, Cs⁺, Tl⁺, Ba²⁺, Pb²⁺ and NH₄⁺. These precursor salts decomposed at relatively low temperature in air gave oxides with the framework structures based on six-membered rings of corner-sharing WO, ₆ coordination octahedra.

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Ethylenediamine (EDA), and p-phenylenediamine (PA) were intercalated into layered tetratitanate. The reactions were enhanced by the water present in these organics and in the interlayer of titanate. The compositions of the products were (EDA)_0.68H₂Ti₄O₉, and (PA)_3.12H₂Ti₄O₉. Molecular axes of EDA and PA were estimated respectively parallel and perpendicular to the host titanate interlayer surface. Ethylene glycol and bis(2-hydroxyethyl)terephthalate could not be intercalated.

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Adsorption of sulfate ion on aluminium hydroxide was investigated in Na₂SO₄ aqueous solution at 40 °C. Amount of adsorption of sulfate ion on aluminium hydroxide incriased with decreasing of pH, but was independent of Na₂SO₄ concentration and presence of urea. ζ-potential of aluminium hydroxide decreased with increasing of pH and became zero at about 8.7(iep). ζ-potential of aluminium hydroxide decreased by the adsorption of sulfate ion, but was not affected by the presence of urea.

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Intercalation of copper into TaS₂ was investigated with variety of copper contents in the range of 0<x<1 (in Cu_xTaS₂) by a direct reaction between copper and TaS₂ at 950 °C in an evacuated silica tube. A homogeneity range of 0.33<x <0.75 was observed for Cu_xTaS₂, in which all the compounds were isostructural with 2H-MoS₂ (hexagonal). The c-parameter increased from 12.93Å to 13.17Å with increasing x in the homogeneity range, while the a-parameter was almost constant at about 3.337 Å. The resistivities of Cu_xTaS₂, at room temperature were found to be in the range of 6 x 10^-4 Ω·cm through 1.8 x 10^-3 Ω·cm, showing the minimun value at x=2/3.

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A new solid lubricant of intercalation compounds Cr_xTaS₂, (x=0-0.600) were synthesized, and the antiwear property was tested by using a shell four-ball machine added to lithium stearate grease. Its lubricating properties were compared with those of molybdenum disulfide MoS₂ and niobium sulfide Nb_1.333S₂. The compounds with composition x from 0.250 to O.500exhibited the same, or better, antiwear property and a low friction coefficient than MoS₂. In perticular, Cr_0.333TaS₂ has the best lubrication properties. Scanning electron microscopy photograph and electron probe micro analysis of the wear scar surfaces indicated that the surface is very smooth and the distribution of Ta and S atom were uniform in the case of x=0.333. The best lubricity seems to come from this character.

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The Li₂O-Al₂O₃-SiO₂ ceramics have excellent thermomechanical and electrial properties. Therefore, the low-temperature synthesis of the eucryptite (Li₂O·Al₂O₃·2SiO₂) or spodumene (Li₂O·Al₂O₃·4SiO₂) ceramics will lead to the wide applications. This paper des cribes the novel method to prepare the fine and homogeneous precursor powders of the system. The process includes the well controlled hydrolysis and following polycondensation of the raw alkoxides. Namely, the partial hydrolysis method of tetraethyl-orthosilicate (TEOS) coupled with the double alkoxide method resulted in the copolymerized precursor solutions with a stoichimetric composition.

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Alkoxide-derived precursors can offer a new sintering process in the Li₂O-Al₂O₃-SiO₂ system. In the part 1, fine and homogeneous precursors of beta eucryptite (Li₂O·Al₂O₃·2SiO₂) or beta spodumene (Li₂O·Al₂O₃·2SiO₂) were successfully prepared. This paper describes the sintering behaviors of the precursor powders as well as the properties of the resulting ceramics. The powder compacts of the precursors densified below crystallization temperatures in all composition. Uniform crystallization occurred after total densification. The eucryptite ceramics sintered at 1000 °C had flextural strength of about 100 MPa. The coefficient of thermal expansion of the ceramics can agree with the theoretical value (-3 x 10^-7/°C). In the spodumene composition, single phase ceramics can be sintered at 1200 °C. The spodumene ceramics showed low thermal expansion (7 x 10^-7/°C) and relatively high strength (about 80MPa). These results show the good sinterability of the alkoxide-derived precursors. As a result, the new process can give the homogeneous ceramics with a excellent properties at relatively low temperature.

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The optimum conditons for Zr02 coating on carbon materials by using a 2-propanol solution of zirconium tetra butoxide(ZrBu) were studied. In order to avoid the formation of ZrO₂ fine particles during the hydrolysis of ZrBu, the additon of diethylene glycol (DEG) into the solution was essential. A homogeneous film of ZrO₂ gel without cracks was obtained by using the solution containing ZrBu of O.05 M and with DEG/ZrBu ratio of 2. In the cases what the DEG/ZrBu ratio was above and below 2, the gel film obtained showed faults, such as cracking or peeling. From the results by weight and viscosity changes of the sol (solution)due to gelation (Fig.4) and thermal analysis of gel film(Fig.5), the gelation in air for 24hours and stepwise heating at 90 and 200 °C for 1 hour, respectively, were determined. Scanning electron microscopic observations of the cross section and the surface of ZrO₂ coated carbon (Figs.7-9) showed that the ZrO₂ film thus prepared had a high homogeneity and adhered excellently to carbon substrate.

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Alumina powders were prepared through a coprecipitation route using either aqueous ammonia or urea as a precipitant into an aqueous solution containing Lboehmite sols and b arium nitrate. The precipitates thus prepared were dried and calcined at various temperatures for 5 h and subjected to surface area measurements.
Thermal resistance of alumina was found to be significantly improved by the addition of barium ions, evaluated by measuring the surface area of barium-added alumina calcined at 1200 °C for 5 h. An optimum amount of barium ions added to alumina was estimated to b e 0.14 mole for a mole of alumina prepared using aqueous ammonia as a precipitant; O.14 mole of Ba for a mole of alumina is just the stoichiometric ratio for the formation of BaO·6Al₂O₃ f rom BaO and alumina. While for alumina prepared using urea, only 0.03 mole of Ba ions was reqired to be an optimum amount to be added to a mole of alumina, suggesting that Ba ions cover the surface of boehmite sols during coprecipitation by urea.
Consequently, it is informed that the study on the structures and proper ties of precipitates is of fundamental importance for a preparation of functional solids.

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Reaction of fine-particle gibbsite in glycol under the spontaneous vapor pressure of the glycol (glycothermal treatment) yields a glycol derivative of boehmite (Ref.5). In this paper, the mechanisms of this reaction were explored. With an increase in the particle size of gibbsite, the yield of the boehmite derivative decreased and the yield of well-crystallized boehmite and the amount of unreacted gibbsite increased (Table 2). Autocatalytic nature was observed during the course of the reaction (Figs.2 and 3). Addition of a small amount of water facilitated the formation of the glycol derivative of boehmite. A honeycomb like texture composed of plate-like crystals of the boehmite derivative was developed on the exterior of the particle when coarse gibbsite was used, whereas the glycothermal treatment of fine-particle gibbsite yielded bulky aggregates composed of honeycomb-like texture, combining the original particles (Figs.4-6). These results suggest that aluminum hydroxide was dissolved into a mixture of glycol and water formed by partial dehydration of gibbsite followed by ligand exchange between the water molecule in the coordination site of aluminum and the glycol molecule and then crystallization of the glycol derivative of boehmite. Formation of boehmite was interpreted by the intra-particle hydrothermal reaction originally proposed by de Boer et al. for the formation of boehmite during the thermal dehydration of gibbsite. A chimney-like structure composed of honeycomb-like texture of the glycol derivative of boehmite was found in the product from coarse gibbsite (Fig.7). This structure may have been formed when closed pore filled with water, where the intraparticle hydrothermal reaction took place, reached to the surface of the particle and a large amount of water together with aluminum species was released from the pore into the bulk solvent.

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Alumina fibers were prepared by the precursor methods based on the aqueous solutions of Al(OPr¹)₃-AlCl₃-Citrica cid (Method A), Al(OPr¹)₃-AlCl₃ (Method B), Al(OPr¹)₃-Al(NO₃)₃Citric acid (Method C) and Al(OPr¹)₃-Al(NO₃)₃(Method D) at room temperature.

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Alumina fibers were prepared by precursor method on the system Al metal-Al(NO₃)₃-Ci tric acid at room temperature. A spinnable composition range in this system was determined to be 50/1 ≤ H₂O mol/total Al mol, 1/1 ≤ metal Al mol/Al(NO₃)₃mol ≤ 2/1 and Citric acid mol/tota l Al mol=1/10.
It was found that in the spinnable solution [Al(H₂O)₃]³⁺, Al-dimer and Al containing polymers were formed. However, the spinnable solution was not obtained from the system which was free from citrc acid.

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The crystallization of yttrium aluminum garnet (YAG) was investigated for the gelatinous product obtained by the reaction of yttrium acetate with aluminum isopropoxide in ethylene glycol at 280 °C under spontaneous vapor pressure of the glycol (glycothermal method). Crystallization of YAG started at 880 °C and completed at 1000 °C. During these temperatures, a small amount of YAlO₃ (hexagonal), was also detected. The crystallization temperature was as low as the reported temperatures for the products prepared by the alkoxide processes (Refs.5 and 6). Therefore, glycothermal method provides a new route to prepare a gel for the preparation of mixed oxides.

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Equimolar mixed hydrous gels containing Ti and Pb were prepared via two different routes, i. e., (i) mixing two unitary sols of TiO₂ and PbO (MS), and (ii) co-precipitation fr om a binary aqueous solution of TiCl₄ and Pb(NO₃)₂ by NH₃aq (CP). Mechanical pretreatment was also carried out, primarily for the purpose of homogenization. The degree of homogeneity was estimated from the variance of Pb/Ti molar ratio evaluated by the elementary microanalysis under the transmission electron microscopy. CP gel was more homogeneous than MS gel. Ball-milling MS gel for 3 h increased its homogeneity only slightly. However, the homogeneity increased up to that of CP on subsequent heating at the temperature as low as 483 K. This kind of thermal homogenization did not take place for the unground MS gel. Grinding of MS gel brought about the amorphization of small crystallites and the suppression of Pb evaporation. These suggest the ionic migration and the formation of Pb-O-Ti bonds during mechanical activation.

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Reaction of oxobis(2, 4-pentanedionato-O, O')titanium (TiO(acac)₂) or titanium isopropoxide (TIP) in various organic media was examined and found to afford microcrysta lline anatase. The product having the smallest crystallite size and the largest sur face area was obtained by the reaction of TiO(acac)₂ in toluene at 250 °C. The product preserved relative ly high surface area even after calcination at 550 °C in an air flow.

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Thin films of Pb-Ti-O were prepared on MgO(100) substrates by chemical vapor deposition using Pb(C₂H₅)₄ and Ti(OC₃H₇)₄ as sources.

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Bismuth titanate film was prepared by the simultaneous deposition of Bi₂O₃ and TiO₂ on heated substrates at 750 °C under a reduced pressure of 6 Torr. Triphenyl bismuth and tetraisopropoxy titanium were used as source materials.

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The carbon films were deposited on the cathode surface in the D. C. glow discharge with the Ar-CH₄ and H₂-CH₄ gas mixtures. We analyzed the optical emission spectra from the glow discharge plasma, and the cathode surface by FT-IR and XPS after the discharge. The relationship between the optical emission spectra and the deposition behavior on the cathode surface was investigated., The emission intensity of hydrogen atoms in the H₂-CH₄ glow discharge was strongly observed, and the deposited carbon films in this plasma contained many hydrogen atoms bonding chemically with carbon atoms. Thus, it was found that the composition of the deposited carbon films was strongly related to the chemical species in the glow plasma. In the Ar-CH₄ glow discharge, however, the emission intensities decreased in the CH₄ % range above 1.5 %. This is probably because the metastable argon atoms quenched by CH₄ molecules and the discharge characteristics largely changed. In the case of H₂-CH₄ glow discharge, the emission intensity ratio CH 431.4/H I 656.3 increased with an increase of the deposited carbon. Therefore, it is possible to estimate the quantity of the deposited carbon by monitoring the emission intensity ratio.

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Sputtered films of the SiO₂-MgO system were prepared by RF-sputtering method. The state of the films, crystalline or amorphous, was determined using X-ray diffraction and thin film X-ray diffraction methods. The amorphous region was in the range MgO = 0-82 mol% when sputtered at 100 W for a duration of 25 h, and MgO = 0-90 mol% when sputtered at 100 W for a duration of 10-30 min. It turned out that the amorphous region was reduced with increasing sputtering time, film thickness and sputtering power. It was inferred that the cooling ability of the substrate becomes poorer as the film thickness increases with time, and that the substrate temperature rises with higher sputtering power. The fact that the amorphous region obtained by the sputtering method is wider than that obtained by the melt-quenching method was speculated due to a striking cooling ability of the sputtering method compared wit h that of the melt quenching method.

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Cadmium oxide (CdO) thin films were prepared by pyrolyzing Langmuir-Blodgett (LB) films of cadmium stearate at 500 °C for 5 min in air with the following two heating processes; heating to 500 °C at the rate of 20 °C·min^-1 (method a) and direct immersion into a furnace kept at 500 °C (method b). Electrical resistivity measurements (Figs.3 and 4) evidenced that continuous CdO thin films which were stable below 400 °C were obtained by the pyrolysis of the LB films of 200 and 300 monolayers by method b but not by the pyrolysis of the LB films of 100monolayers. On the other hand, the pyrolysis of the LB films of 200 monolayers by method a resulted in the formation of a discrete CdO (Fig.3). The results demonstrate that metalcontaining LB films are converted into continuous thin films of the corresponding metal oxides by the pyrolysis when the number of layers of LB films and the pyrolysis condition are well controlled.

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Polycrystalline PbS thin Films were plated on glass-substrates by a new method, “thin liquid film method” at low temperature. Reaction solution (Pb(NO₃)₂ solution and thioacetamide solution) were flowed through the reaction cell (70 × 14 mm, space 0.5 mm) in which the substrate had been placed. The reaction was influenced by the temperature, concentration and pH of the reaction solutions. PUS film with plane surface (thickness was 200 nm) was synthesised at T = 40°C and pH = 9.0 -10.0 using 1-5 mmol·dm^-3 reaction solution. The reaction rate was 18 nm·min^-1 at the best conditions.

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This investigation is to provide a method which can yield magadiite under lower concentration of NaOH and for shorter reaction time compared with the conventional methods for the synthesis of magadiite. Little magadiite was obtained at 120 °C and 170 °C from the starting materials with the molar composition of SiO₂: NaOH: H₂O = 1: 0.23: 18.5 and 1: 0.17: 18.5, respectively. But, the addition of 1-butanol was very effective for the formation of magadiite, especially at the low reaction temperature and low concentration of NaOH. With the addition of 1.3 molar 1-butanol to the starting materials, magadiite was synthesized as a single phase at 120 °C for 7 d and at 170 °C for 18 h.

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Hydrothermal syntheses enable us to prepare HAp crystals with various aspect ratios. HAp crystals 50 nm × 145 nm, aspect ratio = 2.9) were crystallized from the HAp precursor precipitated from Ca (OH)₂ and H₃PO₄ solutions at 200 °C under 2 MPa for 5 h. Among the experimental factors, adding additives are most effective to control the aspect ratio. KOH, K₃PO₄ and EDTA gave needle-like HAp; aspect ratio = 6, 7 and 11, respectively under the similar hydrothermal conditions.

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Bioactive glasses in the system Na₂O-CaO-SiO₂-P₂O₅ are useful as implant materials for repairing bone because of their high bone-bonding ability. Their mechanical strength are, however in sufficient for bone substitutes under load-bearing conditions. The present study deals with preparation of the bioactive glass reinforced with rod-shaped crystals by hydrothermal hot-pressing (Fig.1). The glass powders in the system Na₂O-CaO-SiO₂-P₂O₅ solidified by hydrothermal hot-pressing at 100 °C contained no crystalline phases. The solidified glass had about 86 % density. The Vickers hardness and the compressive strength of the solidified glass were 1 GPa and 150 MPa. The glass powders subjected to a hydrothermal treatment above 150 °C contained crystalline phases of NaCa₂HSi₃O₉ and Na₂Ca₂Si₃O₉ (Fig.2). The glass-ceramics prepared at 350 °C was almost pore free and homogeneously precipitated rod-shaped crystals with the length of about 3μm and with the width of about 0.3μm (Fig.3). The Vickers hardness and the compressive strength of the glass-ceramics were 3 GPa and 460 MPa (Fig.6). The fracture toughness K_IC was 2.5 ± O.3 MPa·m^1/2, about five times that of the parent glass prepared by the conventional method. This high fracture toughness of glass-ceramics might be attributed to the crack defrection toughening and pull-out toughening with the rod-shaped crystals.

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Manganese complex oxide was electrochemically synthesized. Its film was deposited on a Pt electrode by electrochemical oxidation of solution containing La³⁺, Sr²⁺ and Mn²⁺ ions in an autoclave at 150 °C under pressure of 1.0 MPa. The electrolytes were nitrates and chlorides of these metals in aqueous solutions. The deposited oxide films contained La³⁺, Sr²⁺ and water molecules in the structure and had layered structure similar to hydrated manganese dioxides (birnessite) such as Mn₇O₁₃·5H₂O and Na₄Mn₁₄O₂₄·9H₂O. The layer spacings of the oxide films prepared in nitrates and chlorides solutions were 13.535 Â and 12.975 Â, respectively. These values were close to the layer spacing of Na₄Mn₁₄O₂₄·9H₂O (14.26Â), suggesting that the structure of the oxide films are very similar to that of Na₄Mn₁₄O₂₄·9H₂O. It was presumed from IR, XPS, TG and XRD measurements that the layer structures of the oxide films are composed of MnO₂ layers intercalated with water molecules, La(OH)₃ and Sr(NO₃)₂ (or SrCl₂). The electrodeposition process was also discussed from electrochemical measurements and TG etc.

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Reaction sequences from composite powders to corresponding ternary compounds in the system BaO-Ln₂O₃-TiO₂ (Ln=La, Nd, and Sm) and the sintering characteristics of the calcined composite powders. were investigated.

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Growth of β-Ga₂O₃ single crystals was prepared by the high temperature tin solution method using gallium o×ide powder as starting material in an argon atmosphere.
The e×perimental conditions for obtaining single crystals of relatively large size were established. The optimum conditions for growing β-Ga₂O₃ single crystals were found to include weight % of starting materials Ga₂O₃/Sn = 2.0, heating temperature 1250 °C, soaking time 10 h and a cooling rate of 50 °C h^-1.

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Aluminium nitride poWders were synthesized by the spark discharge method in liquid ammonia at 0-130 °C and 2.5-11 kV of the spark discharge voltage using aluminium pellets as starting material. The crystallite size and the grain size of MN were 29-43 nm and 4.5-8.7 μm, respectively. Significant amount of Al coexisted with AlN. The content of A1N increased with decreasing the size of aluminium pellet and with rising the temperature of liquid ammonia. By calcining the powder in nitrogen atmosphere at 900-1200 °C Al coexisted with AlN could be converted to AlN without coagulation of the powder.

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The mechanochemical effects of grinding on the reaction beween Bi₂O₃ and CuO have been investigated. Bi₂O₃, CuO and their mixtures were ground with an automatic mortar for 5 to 100 h, and heated up to 1000 °C. The resulting samples have been examined with XRD, DTATG, DTA-TG-MS and IR. No reaction was observed in the mixture without grinding up to 700 °C, while, ground mixtures transformed into CuBi₂O₄ at about 360 °C and its amount increased with increasing grinding time.
The cristallite size of CuO in the mixtures and CuO alone decreased with increasing grinding time. On the surface of CuO, carbonate was also formed. Bi₂O₃, in the mixtures and alone, transformed into oxycarbonate and into amorphous compound by grinding.

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In the previous work, a finely dispersed TiB₂ has been synthesized by combustion synthesis with a powder mixture of Ti, B and Al in the molar ratio of 1: 4: 1, and the grain size of the synthesized TiB₂ is <0.5 μm, which is much smaller than that obtained from combustion synthesis with a powder mixture of Ti, B and Al in the molar ratio of 1: (n+2): 0 or 1: 2: n (n=0, 1, 2 or 3).
In order to make clear the mechanism of formation of such a finely dispersed TiB₂ particle, the measurement of the temperature hysteresis and the heat of formation during the combustion synthesis are carried out for various Ti-B-Al systems in the present work. As a result, the cooling rate in the process of combustion synthesis with the Ti+4 B+Al powder mixture is found to be much smaller than that with the Ti+2 B+2 Al or the Ti1+5 B one. The heat of formation is a little higher in the former compared to the latter because of formation of A1B₁₂. Therefore, it is considered taht the reaction of Al-B system at high temperature would proceed and supply a little excess heat to the reaction system behind the main combustion front following the reaction of Ti-B system, resulting in the increase of TiB₂ nucleation ratio.
As a result of a hot-pressing test of the present combustion synthesized powders, it is confirmed that the sintered composite of Ti+4 B-FA1 system is superior to those obtained from other systems.

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Surface modification of silica induced by CF₄ plasma treatment and subsequent air exposure has been investigated by X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) and thermally stimulated exoelectron emission (TSEE). Species such as SiF, CF_x. and CO= were formed on the surface. A large ESR signal was observed, and the intensity of the signal increased with increasing treatment time in the same manner as the F/Si atomic ratio increased. The signal intensity decreased and became stabilized with standing time in air just as the fluorine content decreased. The ESR signal may be attributed to a peroxy radical like CFOO·formed by a post reaction of the CF_x radicals on the surface with atmospheric oxygen. For the surface evacuated after the plasma treatment the signal due to the peroxy radical was not observed. The TSEE glow curve exhibited a broad peak emission at ∼250 °C. The intensity of the emission increased and then became almost constant with treatment time. This peak is closely associated with the introduction of fluorine on the surface.

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Synthesis of Ga-mordenite using benzyltrimethylammonium chloride (BTMA) was studied. High crystalline Ga-mordenites were obtained from the synthesis mixtures with ratio of SiO₂/Ga₂O₃ less than 40 and ratio of BTMA/SiO₂ more than 0.05 (Table 1 and Fig.1). The crystal form was plates of about 10 μm in size (Fig.2). The bulk ratios of SiO₂/Ga₂O₃ in Ga-mordenites synthesized were 12-16. TG-DTA profiles suggest that BTMA are occluded in the zeolite (Fig.3)

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Substrates including ceramics, metals and polymers were placed on particles of a CaO·SiO₂based glass which were soaked in a simulated body fluid at 36.5 °C, and then reimmersed into an aqueous solution with ion concenteations 1.5 times those of the simulated body fluid at 36.5 °C. An uniform layer of an apatite similar to the bone mineral was formed on all th e examined substrates. The thickness of the layer increased at a rate of 1.7 μm/d. This kind of biomimetic process might be useful for obtaining highly bioactive composites with mechanical properties close to those of the natural bone.

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TiN combustion synthesis is investigated through a self-propagating reaction of titanium powder compacts of various packing density (40%, to 60% theoretical one) in liquid nitrogen under atmospheric pressure. By changing the position of ignition point, it is confirmed that the upward combustion propagation is more effective for getting higher conversion ratio than the downward one. It is considered that both the heat and evolved nitrogen gas propagate upward in the case of upward reaction propagation, resulting in higher TiN conversion ratio compared to the downward one. As a result of combustion synthesis of Ti compacts added with TiN powders, almost 90% of the TiN content can be attained with the addition of 45mol%, which is the composition to generate the heat of reaction close to the solid-side limits at the melting point of TiN.

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A new process of preparing metal oxide powder by spark discharge between two metal electrodes in deionized water has been studied. In this paper, the phase and shape of the prepared powders by using niobium and tantalum electrodes are reported.
In the case of niobium electrode, niobium and niobium oxide were formed. By applying tantalum electrode instead of niobium one, tantalum and tantalum oxide (δ phase) were formed. Spherical particles appeared in all the cases.

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Oxynitriding of phosphate glass was made by microwave plasma using nitrogen and ammonia gas. Changes of dissolution rate of Na⁺ ion into water, T_g and electric resistivity showed the same tendency as those appeared in general oxynitriding of the glasses. ESCA results showed that the increase of nitrogen contents on the treated glass surface was higher in the ammonia plasma treatment than in the nitrogen plasma treatment.

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