Single crystals of diamond (1∼3 mm in diameter) were grown at high temperatures and pressures by the temperature gradient method using metal solvent. The effect of metal solvent, Fe, Co, Ni and Ni-j binary alloys (j=Fe, Mn, Cr, V, Ti, Zr), on optical properties and morphological features of grown crystals has been studied. The intensity of the four absorption bands in the UV, visible and IR regions (270 nm, 600∼660 nm, 680 nm and 1130∼1350 cm^-1) varied by changing the metal solvent. The 270 nm and 1130 cm^-1 bands, which are due to substitutional nitrogen, were most intense for crystals grown in nickel solvent, while they were undetectably weak for those grown in iron solvent. The addition of the metals ( j) to Ni resulted in the decrease of substitutional nitrogen and this effect was found to increase in the order described above, i. e. Fe<Mn< … <Ti. This tendency was shown to correlate with affinity of the metal with nitrogen. The affinities were estimated from the reported values of solubility of nitrogen in iron-based alloys. Inclusion of solvent metals cccurred when Fe or some of the Ni-j alloys were used. Contrary to what was reported, the absorption band at 680 nm showed little correlation with the bands due to substitutional nitrogen. The occurrence of the 600∼680 nm band is reported in this paper for the first time.

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Effects of the pyrolysis pressure and the starting composition of the organic mixture on the properties and the morphologies of formed carbons were studied for the certain mixture of pter phenyl and anthracene by elevating the pressure and temperature of pyrolysis up to 200 MPa and 700°C, respectively. Carbons formed from anthracene showed the optically anisotropic and graphitizable character and changed their morphology toward the spherule with the increase of the pyrolysis pressure. The isolated anisotropic carbon spherules were synthesized by pressure pyrolysis under 200 MPa, while the mesophase carbons formed intermediately during the pyrolysis readily coalesced on heating under the moderate pressure of 30 MPa to show the complete mosaic structure. The p-terphenyl gave the glass-like carbons with the optically isotropic and non-graphitizable character. By the addition of p-terphenyl to anthracene, the coalescence of the spherical carbons was restrained, and the isolated carbon spherules were produced. The size of the carbon spherules decreased from 20 μm to 5 μm by the addition of 50 mol% p-terphenyl to anthracene as the starting material. The graphitizability of the carbon formed was found to be controlled by the selection of the mixture composition of p-terphenyl and anthracene. It was also found that the spherical carbons with the different graphitizability could be formed efficiently with the carbon yield as high as 85% by the pressure pyrolysis of the mixture of anthracene with p-terphenyl up to 50 mol%.

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Micro-crystals formed by the reaction in alkaline solutio-n containing K₃[Fe(CN)₆] and SiO₄^4-were studied. by the transmission electron diffraction method. The results indicate the crystals formed by the reaction at ca.110°C being disordered α- and β-SiC having a size less than ca.1000Å in diameter. Reduction of SiO₄^4- in the solution is supposed to be proceeded by the oxidation of cyanide ion or cyano radical.

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The sintering behaviour of ultrafine β-SiC powder with the average particle size of 0.01∼0.06μm produced by a vapor phase reaction of the (CH₃)₄Si-H₂ system (1200∼1400°C) was investigated at the temperature range of 1400∼2050°C. In vacuum, a large weight loss of the compact owing to the vaporization of SiC was observed, whereas the introduction of Ar (300mmHg) suppressed the weight loss to a negligible extent even at 2050°C. The compact of un. doped SiC powders was hardly densified at 2050°C, although the grain grew up to ∼5μm. The additions of both boron and carbon powders by 1∼2 wt% promoted the densification and gave the sintered body with the ralative density of above 90% by the pressureless-sintering at -2050°C. When an adequate amount of carbon was deposited for the oxygen content of SiC powders in the course of vapor phase reaction, the powder showed a high sinterability, giving the sintered body with a relative density above 97% by the addition of boron powder alone. This indicates that the homogeneous dispersion of carbon on SiC particles is important to remove the surface oxide layer effectively. Boron and barbon had the inhibitive effet for the grain growth of SiC.

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The vapor phase growth of Si₃N₄ whisker was studied by nitridation of the SiO₂-C-Na₃A1F₆system in flowing N₂ gas at temperatures between 1350 and 1450°C. Si₃N₄ whiskers were grown both at the inside of the graphite sample cylinder with caps and at the outside of it. At the former place, only α-Si₃N₄ whisker grew in the length of average 5 mm with diameters of 0.02∼0.2 μm, while at the latter place, β-Si₃N₄ whisker grew mainly in the length of severa l mm with diameters up to 1.0 μm. The α-type whisker was obtained in a fairly good yield at 0.02∼0.04 molar ratio of NaaAlF, to SiO₂, wherears the O-type whisker was obtained mainly in a high yield at 0.5∼1.0 molar ratio. It was suggested from the thermo dynamical calculation that Si₃N₄ whiskers were produced by the following reaction mechanisms.
It is considered that crylolite (Na₃A1F₆) plays the following roles; 1) to act as a flux and accelerate the reaction of SiO₂ with C, 2) to evolute SiF₄ gas from the inside of fluorosilicate melt and theoreby to promote evolution of SiO gas, 3) to promote the growth of β-type and β'-sialon whiskers.
The α-ty pe whisker obtained in the investigation was identified to have preferentially grown along the directions of [1010] and [1120].

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The hydrothermal growth of quartz crystals has been carried out generally at high filling such as 75∼85%. The growth rates lessen with a decrease, of, filling, and the seeds which are suspended in the growth zone dissolve at a filling of 40% or below. In this experiment, the growth of quartz crystals with a filling of 40% or less, i. e.10∼40%, was carried out by the hydrothermal reverse temperature gradient method, the method whereby the nutrient material was placed at a low temperature (upper side of autoclave) and the seed crystals 'at a high temperature (lower side of autoclave) in Na'OH and Na₂CO₃ solutions. The growth rates were almost identical at 36% and 40% fill, about 1/2 as fast at 20%fill and extremely slow at 10%fill., The dependence of the growth rates on the filling' showed the same tendency in both solutions. The relative growth rates for the Z, X, 'R and r faces were Z>X>r>R. A cre vice flawing was observed on the Z face which exhibited sawtoothed patterns. But the growth in R, r and X directions was flawless and transparent. Spontaneously nucleated crystals were observed conspicuously on the inner wall of the autoclave, but they decreased with a reduction in temperature difference.

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The hydrothermal method has been applied to synthesize solid solutions in the pseudo-binary systems among perovskite-type fluorides (KMF₃: M=Mn, Co, Ni, Zn and Mg) f rom mixtures of co-precipitated powders. The continuous solid solutions existed in the all binary systems. Solid solutions in KCoF3-KNiF3, ICCoFs-KZnF, and KNiF₃-KZnF₃ systems were prod uced in 2 mol KC1 solution under 100 MPa at 300°C, KMnF₃-KCoF₃, KMnFa-KZnF, and KZnF₃-KMgF₃systems at 500°C, as well as KMnF₃-KNiF₃, KMnP., -KMgF₃, KCoF₃-KMgF₃ and KNiFa-KMgF₃ at 800°C. Transition metal ions in perovskite-type fluorides was more easily substituted by other transition metal ions than Mg²⁺ ion.
Crystals of solid solutions were grown by transportation at the t op of the capsule, where the temperature was lower than at the bottom. The crysta-l s in KMnF₃-KCoF₃, KMnF₃-KZnF₃ and KCoF₃-KZnF₃ systems grew faster than the other systems. Their single crystals grew up to 1.5 mm in cubic or rectangular prism form. These crystals were considered to have the same composition as that of the starting material, except for those based on KMgF₃.
The lattice parameter of the mixed crystals in the KCoF₈-KZnF₃ system chan ges continuously with composition, indicating that it obeys to the Vegard's law. The distribution of metal ions in the single crystal of KCo_0.5Zn_0.5F₃ was found to be homogeneous within experimental errors.

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Ferrite formation has been studied in the presence of binary sulfate flux between 600°C and 900°C. Techniques employed are X-ray diffraction analysis, SEM and EPMA.
Mixtures of 0.365 N a₂SO₄-0.635 Li₂SO₄⋅H₂O and constituent oxides [Fe₂ O₃+MO(M Zn, Mg, Ni)] having various particulate characteristics were heated in a Pt crucible at desired tim etemperature conditions, followed by dissolving-out of flux with distilled water.
The flux lowered the temperature of ferrite formation by apprcdiniately 150 degrees regardless of the chemical species of MO(Fig.2). Morphology of ferrite powders so obtained depended on the relative particle sizes of the starting oxides; the combination of large Fe₂O₃ and small MO particles yielded ferrite powders which retained the shapes of the original Fe₂O₃ particles (Fig.5). Size reversal of the oxides, however, yielded ferrite powders with well-developed (111) planes (Fig.8). Two possible mechanisms have been proposed comprising with the relative dissolution rates of oxides into flux and they were confirmed by the experiments using sintered and compacted bodies of constituent oxides.

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Single crystals of the Sm₂O₃-ZrO₂ solid solution system were grown by the arc image floating zone method and the relation between the compositional fluctuation of the grown crystal and its formation mechanism was studied.
The single crystals were w ith Sm₂O₃ contents of 10, 15, 20, 25, 30, 33.3 and 40 m 01%. CraCk-free single crystals (3∼5 mmφ × 50∼70 mm) could be grown when their Sm₂O₃, contents were 10∼25 mol%, but those with Sm₂O₃ content over 30 mol% always developed cracks and tended to shatter on cooling. The surfaces of the crystals which were cut in parallel or nomal to the growth direction were polished and examined by EPMA for characterizing the compositional fluctuation. After the etching with hot phosphoric acid, the same surfaces were examined microscopically. A pattern of concave stripes with 0.1∼0.15 mm intervals was found on the etched surface parallel to the growth direction and a pattern of circular stripes on the etched surface normal to the growth direction. These patterns correspond well to the compositional fluctuation determined by EPMA. Places difficult to etch were rich in ZrO₂. A careful examination showed that the pattern of circular stripes was a part of vortex. In the crystals having Sm₂O₃ contents over 30 mol%, a pattern of honey-comb was found on the surface normal to the growth direction, suggesting that the cellular growth was occuring. The frequencies of the stripe pattern and the compositional fluctuation correspond to the rotational frequency of the growing crystal in the crystal growth apparatus. Cyclic changes in the solidliquid interface temperature due to the nonuniform heating are responsible for the compositional fluctuation of the grown crystal.

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In an attempt t o e l u c i id d a a tt e e u n _ a m e n t a l problems for synthetic step, and to improve properties of inorganic composite materials by the interaction between inorganic and organic su b stances, the hydrate of CaO-H₂O-CH₂OH system was prepared by immersing CaO and Ca (OH)₂ in methanol, and formation mechanism and characteristics of the hydrate were investigated.
Firstly the methoxidation of CaO and Ca (OH)₂ in methanol was compared; Both hydration and methoxidation occurred simultaneously in the former case, and Ca (OH)₂ and Ca (OCH₃)₂ formed after reacting for 5 h, but in the latter 4 days was necessary to achieve th e same state. However there is not any difference betwen the two cases to reach almost equilibr ium state after reacting for 7 days. The (001) spacing of Ca (OH)₂ and Ca (OCH₃)₂, for med in the early stage of immersion, increased or decreased. This fact suggested that the hydrate w as mixed with calcium hydroxide methoxides through mutual substitution of OH↔CH₃O group between the both layer of layer structured Ca (OH)₂ and Ca(OCH₃)₂ of CdI₂ type. From X-ray diffractometric analysis, these phases were expressed as formulae of Ca (OH)_1.5 (OCH₃)_0.5 and Ca (OH)_0.3(OCH₃)_1.7.
The h y drate crystal containing Ca-OCH₃ bond became thin hexagonal plate-like shape with particle size of 2 μ m (specific surface area being 2.1 m2/g) as a result of friction of (001)plane in layer structure by immersing in methanol. Moreover, it was proved that carbona tion of the hydrate under humidity at 80% was remarkably controlled by the bonded CH₃O group on the crystal surface. Also the group was stable at around 300°Cby heating. The hy d rate of CaO-H₂O-CH₃OH system fairly dispersed in several organic solvents and then its s urface was changed into lipophilic. The hydrate containing Ca-OCH₃ bond could be expec t ed as inorganic filler for plastics, rubber and paper.

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Single crystals of various chalcogenides with high melting point and high volatility were grown under a flowing Ar gas at normal pressure by a floating zone method, utilizing a 5 kW Xe arc lamp and an ellipsoidal mirror as an image furnace. Homogeneous crystals with large size, typically 3 mm Φ× 30 mm, were obtained for CaS, SrS, BaS, CaSe, SrSe, BaSe, EuS, EuSe and for solid solution systems of EuS-SrS and EuS-EuSe. Characterizations by X-ray powder diffraction and optical measurements indicated the superior qualities of these crystals to those by the conventional crystal growth methods. Despite the high growth rate, typically 50to 70 mm/h, the homogeneity of the solute distribution was sufficiently good to qbserve the sharp reflection spectra due to the band edge exciton transitions. In the case of CuxMo₆S₈ (x=1.6∼3.2), the microscopic fibrous precipitation of Mo was observed in the otherwise single-crystalline matrix phase. The precipitation could not be avoided unless the atmosphere was slightly pressurized to about 10 atm. The effect of volatilization was discussed in terms of stoichiometric and non-stoichiometric ones. The former turned out to raise rather minor difficulties to the crystal growth process; on the other hand, an adverse effect such as eutectic solidification could result from the change in the melt composition due to the latter.
As a whole, the present method operated under normal pressure seemed to b e highly potential for the growth of single crystals even with high volatility, provided that their volatilization was nearly stoichiometric.

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Shock synthesized wurtzite type boron nitride (w-BN) powders with particle size of 0.1∼0.5 μm were treated in the temperature range between 1150°C and 1900°C at 6.7 GPa. The purpose of this study is to clarify the sintering process and the relation between microstructure and mechanical properties. A link type of cubic anvil very high pressure apparatus was used for very high pressure sintering. w-BN transformed to zinc blende phase (z-BN) above 1300°C. The apparent density and vicker's micro hardness of sintered compacts increased with increasing temperature of treatment up to 1600°C for 15 min. Any grain growth was not observed in the sintered compact treated below 1600°C.
The compact, obtaind at 6.7 GPa and 1600°C for 15 m in, consisted of 10 w t% w-BN and 90 wt% z-BN and had theoretical density and extremely high hardness above 8000 kg/mm2. Hardness and density decre ased with increasing temperature above 1600°C and grain growth was arisen. Plate-like grains whose plane corresponded to (111) of z-BN was observed in the compact obtained at 1900°C. It is seemed that a prefered orientation of w-BN powder to (002) relates to anisopropic grain growth of z-BN.

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Aluminum phosphates were synthesized by hydrothermal treatment of the CaO⋅n Al₂O₃ in H₃PO₄ solutions at 100°Cor 200°C under a pressure of 10 MPa. Their thermal change w as examined, together with the strength of hardened bodies. Three types of AlPO₄⋅2H₂O (i. e. Lucin-type variscite, Messbach-type variscite and Metavariscite) are produced as aluminum phosphate at 100°C and 3 types of AlPO4 (Berlinite, Tridymite form and Cristobalite form) at 200°C.
Decomposition and transformation of variscites during heating were also studied in air by TG-DTA and X-ray diffractometry. The strength of hardened bodies increased with the decrease of their CaO/Al₂O₃ ratio and was enhanced up to 150 to 290 MPa for the products in the system of CA₆.

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The new method is called a disk process; titanium dioxide and anhydrous potassium carbonate in a 3: 1 molar ratio were thoroughly mixed and pressed into disks (13 mmφ×2∼3 mm thick)under the pressure of 113 kg/cm². The disks were calcined in a muffle furnace at a temperature of about 900 to 1100°C. In the synthetic reaction using the disk process, a new potassium titanate Y-phase, presumed to be potassium trititanate, was found and two types of the potassium titanate “Fur-fibers” were obsereved.
The reaction between titanium dioxi de and potassium carbonate involves solid-liquid reactions, varying with the melting points of different potassium titanates, the vaporization and mobilization of potassium oxide. Potassium titanates except potassium hexatitanate could be formed through the melt or incongruent reaction, depending on the quantity of potassium oxide. The phase of potassium titanates recrystllized from the melt was influenced by the coexisting potassium titanate, solid.
The basic sequenc e of the reaction (between titanium dioxide and potassium carbonate through the disk process) was as follows; Y-phase→ potassium tetratitanate → potassium hexatitanate. As the Y-phase changed into potassium tetrattitanate, “Fur-fibers” were grown.

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The potassium tetratitanate fiber produced through the reaction between titanium dioxide and potassium carbonate by the KDC process (Kneading-Drying-Calcination) were converted into six different hydrous potassium titanate fibers (X_I to X_VI ) and one hydrous titania fiber (X_VII)by leaching with water.
The X_I (2K₂O⋅11TiO₂⋅3H₂O), X_II (K₂O⋅6TiO₂⋅19/11 H₂O), X_III (K₂O⋅7⋅TiO₂⋅24/11 H₂O), X_IV(K₂O⋅8O₂⋅29/11 H₂O) and X_VII(2TiO₂⋅H₂O) phases were treated with water, potassium hydroxide and sulfuric acid under hydrothermal conditions. Consequently, the X_I, X_II and X_III phases changed into fibrous anatase, potassium hexatitanate, potassium tetratitanate and X_V (K₂O⋅9TiO₂⋅34/11 H₂O), the X_IV2 phase into fibrous anatase, potassium hexatitanate and X_V, the X_VII phase into fibrous anatase, fibrous rutile and potassium hexatitanate. These seven phases were divided into three groups, X_I to X_III, X_IV to X_VI, and X_VII
The initial stage of hydrothermal reaction were predominantly the internal reaction of solids which depended on the structure of starting hydrous materials.

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Self-diffusion coefficients of the constituent ions were compared for fluorite-cubic oxides and halides including antifluorite-cubic Li₂O. The diffusion characteristics were discussed with respect to their sublattice structures, employing Arrhenius-type plots normalized in terms of the melting points. By comparison of the tracer diffusion coefficients and ionic conductivities, the charge carriers were confirmed to be the oxide ions for ThO₂ and the lithium ions for antifluorite-cubic Li₂O. Magnesia- and calcia-stabilized zirconias exhibited similar breaks in the temperature dependences of the oxygen diffusivities at approximately 1400°C, as determined by the isotope exchange technique. The low-temperature regimes with increased activation energies were interpreted as due to the occurrence of a second phase for the MgO-stabilized zirconia and as due to the order-disorder transformation for the CaO-stabilized zirconia.

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The sintering of Sm₂O₃-ZrO₂ solid solutions (Sm₂O₃ concentration; 0, 5, 10, 15, 20, 25, 30, 33, 40, 45, 50 mol%) was studied at the temperature range from 1200 to 1600°C, and the sintering time for 0.5 h to 32 h by measuring the linear shrinkage of powder compacts and examining the microstructure of sintered specimens. The apparent diffusion coefficient was calculated using the initial stage sintering equation, and the effect of composition on the sintering behavior was discussed. The sintering kinetics of all solid solution compacts followed the volume diffusion model. The sintering behavior was concluded to be which contained from 0 to 5 mol% Sm₂O₃, monoclinic ZrO₂ and/or fluorite phases were present and the linear shrinkage decreased significantly with the increase of Sm₂O₃ concentration. In the concentration range of Sm₂O₃ from 10 to 20 mol%, only single phase fluorite. type solid solution was present. The linear shrinkage, apparent diffusion coefficient and the grain size of the sintered specimen decreased with the elevation of Stn, O, concentration. In the concentration range of Sm₂O₃ from 25 to 40 m ol% (singie phase pyrochlore type solid solution), the linear shrinkage, apparent diffusion coefficient and the grain size were nearly independent of Sm₂O₃ concentration. In the range of Sm₂O₃ from 40 to 50 mol% (single phase fluorite type solid solution), the entire sintering properties such as shrinkage, grain growth rate and apparent diffusion coefficient increased significantly with increasing Sm₂O₃ concentration.

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The formation of solid solution of the NaCl-KCl and CaO-SrO systems, one of the simplest reaction which involves two or more phases, have been studied by X-ray diffraction method. In the NaCl-KCl system the formation proceeds in two phases during all 'stag es of the reaction. The rate is so high that it was difficult to analyse the kinetics of the respective reaction. The activation energy of overall reaction of the formati/o4 of solid solution is estimated to be 48 kcal/mol for the product of 1: 1 molar' ratio, and a little higher for 0.65: 0.35product. Meanwhile, in the system of CaO-SrO, the formation proceeds in two or more phases, and it was 'possible to determine the value of the activation energy from the decrease of the amount of strontium oxide. The value thus obtained by means of high temperature X-ray diffractometry was estimated to be 61 kcal/mol. From the experimental results of the present research, it was clarified that the formation of solid solution proceeded by the mutual diffusion of the cations. However, the rate of diffusion depended on the characteristics of starting reactants as well as on the condition of the reaction.

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The transformation process of graphite to diamond without any intensive addition of metal was observed dynamically by following the change in the applied voltage-current relation directly passed through graphite sample under pressure (by so-called the electro-thermal analysis).
Spectroscopic graphite bar and graphite bar for electrode of 80 to 250 mg were exposed to the static pressure of 80 to 140 kb (14 GPa) at 2100 to 2900 K.
By applying the a. c. voltage stepwise, the current throu gh the graphite sample increased stepwise. When the voltage was attained to about 1.8 to 1.9 V, the current drastically decreased, indicating the conversion of graphite to diamond. It was found that the graphite sample must be machined into the optimum size in order to avoid the reconversion of diamond to graphite by the superheating of diamond. Under the pressure below 120 kb, the induction period prior to the conversion to diamond and the, apparent crystallization time increased with the decrease of the applied pressure. The pressure of 120 kb was essential to convert graprhite to diamond without any induction period. It was found that the phenomena accompanied by the diamond formation could be observed reproducibly by controlling the dimension and the charge density of the starting graphite sample. with the same graphitizability. The crystal morphology of diamond formed depends remarkably on the applied pressure. Above 120 kb, diamond was crystallized in dendritic form indicating the rapid nucleation of diamond. Below 120 kb, the crystal growth becomes dominant to develop the (111) face.
The analysis of the relation of the applied voltage to current, that is to say, the electrothermal analysis was found useful for the efficient diamond production under a controlled cOndition, since the behavior of the starting graphite sample can be followed dynamically in the process of the transformation.

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The graphitization of the nongraphitizing carbon matrix in a C/C composite has been explained as a stress graphitization process caused by a large shrinkage of matrix around the fiber. In this paper the stress accumulation along the fiber axis together with the effect of adjacent fibers was investigated by means of thermal shrinkage measurement, thermogravimetric analysis, optical microscopy and X-ray diffraction techniques by using PAN CF/Furan C and Phenol CF/Phenol C composites.
The accumul ated stress by a single fiber along the fiber axis was estimated to be about 440 MPa from the measurement of the residual strain of the fiber. The effect of the distribution of fibers along the fiber axis was examined by the addition of stress with two adjacent fibers, because the direction of the accumulated stress along the fiber axis was the same as the direction of the stress by the adjacent fibers. Then, the stress accumulated between the adjacent fibers in a distance of 2.3, am was estimated to be about 660 MPa for the composite with 60vol% fibers. The stress distribution profile was also illustrated by this model. This value of 660 MPa agreed with the pressure graphitization of the glassy carbon.
It was assumed that the accumulated stress of 660 MPa induc ed on the carbonization process was large enough to form activated stage, which would act as a source for the graphitization of composites at high temperatures above 2000°C.

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The crack velocity in fused silica and soda-lime silicate glass was determined at 17∼64°C in various H₂S gas environments from 0.1 to 1 Torr by means of the double torsion technique, in order to / clarify the mechanism of stress corrosion reaction between H₂S and stressed glass. The chemical reaction was found to be the first-order reaction similar to that between H₂O and stressed glass, although the reaction rate with H2S was much slower than that with H₂O. The activation energy of the reaction was 38 kcal/mol between H₂S and fused silica and 27kcal/mol between H₂S and soda-lime silicate glass. These values were higher than those with H₂O by several kcal, and this difference was attributed to the difference in size and polar ization between H2S and H20 molecules. However, the mechanism of stress corrosion of silicate glasses bx, H₂S was essentially the same as, that by H₂O.

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In order to obtain a strong body of active alumina, the relationship between the strength and hydration conditions of the body was investigated. The result revealed that the strength of the body increases by the bond formation through the repetition of alumina dissolution and boehmite precipitation during the hydration treatment. This bond is not broken by the dehydration treatment 700°C and the bend strength of the body was maintained 300 kg/cm².
On the basis of the test result, a new type of honeycomb substrate was de veloped. The honeycomb catalyst impregnated with Pt was used for the oxidation of propane. The catalytic activity was related to the depth of impregnated Pt in the substrate. The active alumina substrate was found to be suitable to get an optimum depth of Pt impregnation. A method to estimate the life time of the catalyst in a plant vas developed by an accelerated test in a laboratory, and was approved its appropriateness by measuring the rate of Pt sintering.

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A study was made on the characteristics of the hydrogen absorption and desorption of Mm_1-x⋅AxNi₅ and MmNi₅ B_y of which Mm or. Ni in MmNi₅ were partially substituted by the metals (A and B). The dissociation pressure of, Mm_1-xAx Ni₅ (A: Al, B, Cu, Mn and Si)hydrides was higher than that of NmNi₅ hydride, whereas, the dissociation pressure of Mm⋅Ni₅_B_y (B: Al, Co, Cr, Cu, Fe, Mn, Si, Ti, V and Zn) hydrides depended on the con tent'of the metals, which substituted partially for nickel, and log P decreased in proportion to y. The dissociation pressure of MmNi_5-yB_y hydrides decreased in the following order: Mn> Al>Cr>Si>Fe>Co>Cu. A linear correlation was found between log P and the cell volum e of the alloy for the _5-yB_y. The trend of lower pressures along with the Mn and Al contents were in agreement with the cell volume correlation observed in other AB, compounds. MmNi_4.5B_0.5(B: Al, Cr, Mn and Si) and MmNi_2.5Co_2.5 could easily be activated and react fairly readily with hydrogen to form the hydrides MmNi_4.5Al_0.5H_4.9, MmNi_2.5Co_2.5H_5.2, Mm⋅MmNi_4.5Cr_0.5H_6.6 and, MmNi_4.5Si_0.5H_3.8 (hydrogen contents: 1.2, 1.2, 1.4, 1.5 and 0.9 wt%, respectively) under a hydrogen pressure of 60 atm at room temperature. 'The enthalpy changes in hydride formation determined from the dissociation isotherms for MmNi_4.5Al_0.5-H, MmNi_2.5 Cro_2.5-H and MmNi_4.5Mno_0.5-H systems were -5.5, -8.4, -6.1 and -4.2 kcal/mol H₂, respectively. These values were smaller than or nearl y the same as those of LaNi₅ and MmNi₅. The dissociation pressures were 2.5, 2.0, 4.8 and 2.0 atm at 20°C, respectively. The apparent activation energy of hydrogen desorption for these alloys were smaller than those of LaNi₅ and MmNi₅. For MmNi_4.5, Al_0.5, MmNi_2.5Co_2.5, MmNi_4.5Cr_0.5, and MmNi_4.5Mn_0.5 the hydrogen absorption-desorption cycles were repeated 500 times but no variation in the hydrogen absorption-desorption capacity was observed. The cyclic studies with MmNi_4.5Mn_0.5 showed that the spalling occurred more rapidly than with MmNi_2.5Co_2.5 and MmNi_4.5Cr_0.5

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Conditions which lead to the formation of spherical silica particles of uniform size by the reaction of tetraalkyl orthosilicate in alcoholic solution with water in the presence of ammonia are described. A series of electron micrographs and pH measurements of the solution are observed during the hydrolysis. Numerous small particles having irregular shapes and particle sizes from 100 to 200 angstrom are observed in very early stages of the process. A part of the particles spontaneously gathered together followed by immediate coagulation. The aggre gates changed from irregular shape into perfect- spheres and grew larger by the exhaustible supply of the small particles in an instant.
Rapid decrease of pH at that tim e continued until the small particles disappeared. In the final step of the hydrolysis, slow growth of spheres are observed by the concentration of solu te Si(OH)₄ species on their surface. In the meanwhile, pH of the solution remained at a de finite value.

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Silicon nitride (Si₃N₄) is one of Candidate materials for the engineering caraniics which can be used at high temperatures. The mechanical strengthsof hotpressed or sintered Si₃N₄ cera.; inics containing some amount of additives, however, , are deteriorated at elevated temperatures. To improve the, high temperature strength of Si₃N₄ ceramics, an attempt to consolidate Si₃N₄ without additives was made by high pressure sintering technique. Scanning, electron mic rographs of fracture surfaces of the sintered bodies showed the bodies had finely grained and fully selfbonded microstructures. Vickers microhardness of selfbonded sintered bodies were 310N/m² at room temperature and 174 N/m² at 1200°C.

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A new indium phospiiicte, InP₃, was prepared by the reaction between two elements under high temperature and pressure conditions. Its X-ray powder diffraction pattern was completely indexed with, heiagonal lattice constants of a = 0.7449 and c =0.9885 (nm). The structure of InP₃ is considered to be closely related to those of GeP₃, and SnP₃. The c/a ratios for N b element phosphides are about 1.4, while that of InP₃ is 1.3. This may indicate that the environment of In in the structure is different somewhat from those of Ge and Sn. InP3 is a metallic conductor and diamagnetic.

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ZeoliteY was s ynthesizedfr om homogeneouasq ueouss olutionsa t 100°Cu nder atmospheric pressure, and was grown as a single phase from a clear solution with the iutia1 composition of 10 Na₂O.0.45 Al₂O₃⋅26 SiO₂⋅270H₂O. As a reaction time was prolonged, zeolites S and Pc appeared in the solution, and in final, zeolite Y formed previously decomposed to zeolite Pc. The effect of the discontinuous change of soda, alumina at41 silica concentrations in mother liquors in the course of the reaction was examined on the tability of crystallizingz eoliteiY. The results, show that the reduction of their concentrations due to the formation of zeolites causes the conversiono f zeolite Y to Pc. The chemicala nalysis data of synthetic zeolite Y lead a conclusionth at polymer speciesh aving the compositiona nd structure a nalogoust o those of crystallized zeolite Y exist in the mother liquor.

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It is known that catalysts prepared from ammonium metavanadate and chromium (III) nitrate contain X- and Y-phases besides vanadium (V) oxide and chromium (III) oxide. No data concerning the crystal structure and the compositions of these two phases have appeared in the literature so far.
In the pres ent work, X- and Y-phases were isolated by an extraction technique using aqueous ammonia and their compositions were determined by chemical analysis to be Cr₂V₁₂0₃₅and Cr₆V₁₈O₄₅, respectively.
It was reported that the catalyst containing Y-phase showed high activity for the oxidation of acrylaldehyde in the liquid phase reaction. Therefore, experiments were further carried out to obtain the favorable conditions for the preparation of the catalyst containing a large amount of Y-phase. The conditions were proposed as follows; NH₄VO₃ and Cr (NO₃)₃⋅9 H₂O are mixed together in water and kneaded at around pH 6.5, and the precipitates obtained are then calcined at 600°C in air.

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MSn(OH)₆ (M=Ca, Mg, Co, Cd, Zn) was synthesized by the coprecipitation method from dilute Na₂Sn(OH)₆ and M²⁺ solution, and characteristic properties of the precipitate were studied by X-ray diffractometry, thermogravimetry and differential thermal analysis. A linear relation between lattice constant ao and ionic radius of M²⁺ was found. By using mixed solution of Cd²⁺ and Mg²⁺, (Cd_1-x Mgx)Sn(OH)₆ was obtained. They decomposed to MSnO₃ by releasing water at the elevated temperature, which depended on M2+. The decomposition product of the first step was amorphous and upon the heating up to 600°C the amorphous phase transformed to crystalline.

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Alkylamine (n-CmH_2m+1 NH₂ where m=0∼6) intercalation was quantitatively investigated with layered compounds Na₂Ti₃O₇, and H₂Ti₃O₇. Na₂Ti₃O₇ has exchangeable sodium ions in its interlayer region. These sodium ions were substituted for H⁺ through the HC1 treatment of Na₂Ti₃O₇. The obtained H₂Ti₃O₇ was intercalated by alkylamines. With the original Na₂Ti₃O₇, however, the alkylamine intercalation could not be observed. The intercalation proceeded with the exchange of the interlayer protons for alkylammonium ions, but only a part of them (25∼42%) were exchanged. The orientation of the intercalated alkylammonium ions was estim ated on the basis of interlayer distances increasing with an increase of the carbon number in the alkylammonium ion (Fig.1), and a model with double layers of the alkylammonium ions (Fig.2) was proposed.

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Oxygen self-diffusion coefficient has been studied in Li₂O⋅2 SiO₂ glass. The concentration distribution of stable ¹⁸O isotope within the glass after the gas/solid exchange was determined by secondary ion mass spectrometry. A diffusion coefficient and a surface exchange reaction coefficient were determined from the concentration distribution.

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The adsorption of oxygen and the oxidation of carbon monoxide over LaMetal (Co, Ni, Fe, Mn, Ti) perovskite oxides were investigated by the pulse adsorption and flow method. The amounts of O₂ adsorption strongly correlate with the binding energy of transition metal coordinating with oxygen of the perovskite structure. The relation was discussed between the electronic configuration of transition metal ion of perovskite oxides and the catalytic activity in connection with CO oxidation mechanisms.

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