Fundamental investigations of the reaction between Si₃N₄ and molten iron have shown that Si₃N₄ material is desirable in steelmaking process. This paper describes the influence of dissolved oxygen in iron on the corrosion of reaction-bonded Si₃N₄. The results are as follows:
Si₃N₄ specimens dipped into iron containing more-than-300-ppm dissolved oxygen for 30 minutes at 1630°C and rotated at 300rpm were not attacked. However, molten iron of less-than-300-ppm oxygen attacked Si₃N₄ as oxygen contents decreased. Optical microscope and EPMA observations showed the formation of 50-150-μm thick SiO₂ layer on the Si₃N₄ surface which did not corrode. Otherwise, there was none of the thick layer on specimens dipped in below-300-ppm-oxygen iron. This reaction mechanism was discussed thermodynamically. Iron with a high dissolved oxygen level forms a large amount of SiO₂ at the beginning of the reaction, which acts as a protection layer on the Si₃N₄ surface. On the other hand, a low dissolved oxygen level iron causes the Si of Si₃N₄ to dissolve into iron without SiO₂ formation.

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The growth of PbTiO₃ single crystals was studied using a MgO single crystal crucible by flux cooling method. As-grown PbTiO₃ single crystals were used for measurements of relative dielectric constant, dielectric loss, dc-resistivity and pyroelectric coefficient. The results obtained are as follows. In this study the preparation conditions to obtain large PbTiO₃ single crystals are summarized as follows. When the raw material mixed with the starting material/flux=PbTiO₃/PbO (weight ratio)=0.339 was used, melted and cooled, a transparent PbTiO₃ single crystal with a maximum size of 2.7×2.7×1.2mm was obtained at a cooling rate of 5°C/h in the range of 600° and 400°C near the Curie point, and 20°C/h in the ranges of 1100° to 600°C and 400°C to room temperature. Mg²⁺-doped PbTiO₃ single crystals prepared in a MgO single crystal crucible were better than that in a platinum crucible. They were obtained in the middle part of the crucible at the upper part of flux as large plate-like crystals, containing 3000 to 5000ppm MgO from EPMA spot analysis of the crystal surface. From measurements of pyroelectric constant, the pyroelectric properties of Mg²⁺-doped PbTiO₃ single crystals were elucidated. The present single crystals were found to be particularly superior with respect to dc-resistivity and dielectric loss to those of pure PbTiO₃ single crystals.

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Experimental and analytical studies on fracture toughness of alumina ceramics were carried out, and the following results and conclusions were obtained.
(1) The fracture toughness obtained by conventional fracture mechanics approach is apparent one, and increases with an increase of precrack length and shows a constant value in the range of larger crack length.
(2) This characteristics was explained by the interaction between a main precrack and inherent microcracks or voids near the crack tip.
(3) The microcrack is often induced near the tip of the notch during cutting under green sheet. The microcrack results in the deviation from the linear relation between load versus displacement, and decreases the fracture toughness.
(4) If we avoid the elimination of factors (2) and (3) would enhance the fracture toughness and decrease its scatter.

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Alumina membranes were modified by the chemical treatment using trimethylchlorosilane (TMS), octadecyldimethylchlorosilane (ODS), γ-aminopropyltriethoxysilane (γ-APS) and 1, 3-propane sultone (PS) to control the zeta potential and surface free energy. Silane coupling agents such as TMS, ODS and γ-APS reacted with surface hydroxyl groups of alumina membrane and formed Al-O-Si bondings. PS was also incorporated into alumina surface by Al-O-C bondings. Reacted amounts of TMS, γ-APS and PS with surface hydroxyl groups were estimated as -3 molecules/nm² by elemental analysis, whereas ODS was found to be reacted with 1.0 OH/nm² hydroxyl groups of alumina. It may be considered that reacted amounts are restricted by geometrical arrangements of ODS on the alumina surface. Zeta potentials of surface-modified alumina membranes were controled to be anodic and cathodic by the introduction of sulufo groups from PS and amino groups from γ-APS, respectively. Low energy surfaces were produced by the introduction of alkyl groups like TMS and ODS.

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In forming glass material with a metal mold, the heat is transferred from the material to the mold mainly through conduction. In this operation, the minimal clearance between the hot glass and the mold is important. The minimal clearance was studied using polyethylene glycol in place of the hot glass, and the followong results have been obtained:
(1) When two metallic surfaces come into contact with each other, a clearance of air layer is formed, the size of which depends upon the roughness of the metallic surfaces from the viewponit of heat transfer coefficient.
(2) In filling polyethylene glycol into the gap of two metallic surfaces, the clearance is filled up with polyethylene glycol, leaving no air layer, as long as the surface roughness is not too large. The clearance remains nearly unchanged even if the metallic surfaces are coated with such parting agent as graphite.
(3) In actual glass forming, a clearance really exists as seen from the heat transfer, and since its size is larger than it is considered from the surface roughness, the clearance is surmised to be formed by the air that is left behind during forming.

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Thermogravimetric analysis and electrical conductivity measurement were performed for magnesium ferrite at 1000°-1300°C under the controlled oxygen partial pressure. The ferrous ion concentration in the hematite-rich magnesium ferrite increased with decreasing oxygen partial pressure (P_O2) at a fixed temperature, but remained constant in the spinel stoichiometric with respect to the cation-to-anion ratio. Enthalpy of the defect-equilibrium reaction was calculated to be 24.8kcal/mol. Both electrical conductivity and ferrous ion concentration showed similar P_O2 dependences. Arrhenius plot of P_O2-independent conductivity gave an activation energy of 0.16-0.21eV for hopping conduction. Detailed analysis taking into account of the temperature dependence of cation distribution showed that hopping conduction among octahedral iron ions was predominant in both stoichiometric and non-stoichiometric magnesium ferrites.

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Diamond synthesis from graphite with catalysts was tried at various temperatures and pressures. The diamond formation regions were determined by the press load and the temperature of samples measured with thermocouples. By comparing the diamond formation regions with thermodynamically calculated diamond-graphite equilibrium curve, the conical belt high pressure apparatus which was used in the present study was calibrated at high temperature. There are two differences between the resultant line and the calibration line which was determined by using Bi as a calibrant at room temperature; (1) the pressure loss at high temperature is greater than that at room temperature, (2) the slopes of the calibration lines at high temperature are greater than that at room temperature. These differences may be affected by the difference of the sample environments between high temperature and room temperature. The calibration of pressure based on the diamond-graphite equilibrium curve is exact at high temperature.

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β-SiC whiskers were grown by thermal decomposition of two kinds of sulfur-containing silicone oils at 1200°-1400°C. Yield of the whiskers was maximum at 1300°C, and was higher for the oil containing a larger amount of sulfur. The products were white and wooly whiskers having high aspect ratios, 0.1-0.4μm wide and 0.5-9cm long, the aspect ratios and dimensions being dependent on the reactant oils and reaction temperature. The whiskers were triangular rod-form. The growth axis was identified to be ‹111› of β-SiC and side faces were {211} planes. Tensile strength of the whiskers with apparent diameter 1.7-2.9μm was 1.7-14.9GPa, approximately the same as those obtained by other reactions. Many stacking faults were observed obliquely against the whisker axis by electron microscopy, but the existence of stacking faults exerted no influence on the mechanical properties. In addition, there were no perfect dislocations which might result in the lowering of mechanical properties.

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Changes in crystal structure and electric conductivity of Mn-Fe-Co-Ni oxide, a thermistor material, in annealing process were investigated. The starting oxide was prepared by heating a mixture of Mn, Fe, Co and Ni nitrates with molar ratio of 5.7:4.0:1.5:1.0 at about 500°C. The mixture was fired at 1400°C for 1h, cooled and held at 1000°C for 1h. The rates of heating and cooling were 10°C/min. After heating for 1h at 1000°C, the electric power was cut off and the sample was cooled without control in the electric furnace to room temperature. The sample was annealed at 250° to 370°C. X-ray diffraction analysis of as-fired sample detected only a cubic phase with the lattice constant of 0.845nm. Annealing at 250° to 350°C yielded an additional tetragonal phase. The crystal phase of the sample annealed at 370°C was the same as that of the as-fired sample. The phase changes by annealing were attributed to the phase transition of cubic spinel into tetragonal spinel, and the transition was related to a Jahn-Teller type of distortion, which was caused by octahedral Mn³⁺ ions. It was considered that the degree of distortion depended on the concentration of Mn³⁺ which was a function of the annealing temperature. On the other hand, the changes in electric conductivity during annealing were not associated with the crystal structure change.

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The friction and wear properties of newly developed partially stabilized α-sialon ceramics were measured with a pin-on-disk type tester in air at room temperature, at a sliding velocity of 18cm/s and applied load of 1kgf. When α-sialon disk was used, the specific wear rate of α-sialon was 4×10^-8mm²/kgf, a little greater than Si₃N₄ or ZrO₂. The wear of α-sialon on ZrO₂ disk was in the same level as that on α-sialon disk, but the wear of Si₃N₄ and ZrO₂ on ZrO₂ disk was much higher. α-sialon is considered to be one of the excellent wear resistant materials, as it shows relatively low specific wear rate, and α-sialon disk wears much less than ZrO₂ disk. The wear of α-sialon was almost zero, when sliding on metal disks, such as cast iron or phosphorus bronze, which is the same as any other ceramics. On the other hand, the wear of metal disk was severe, with the specific wear rate in the order of 10^-5mm²/kgf. Cast iron disk showed two times greater wear than phosporus bronze disk against the α-sialon pin.

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Diethanolamine (DEA) suppressed the precipitation of the hydroxide on the hydrolysis of magnesium aluminium isopropoxide MgAl₂(O-iPr)₈ (MAI), and a clear solution was obtained even after the addition of water to the isopropanol solution of MAI and DEA, resulting in gellation on addition of excess water. The conditions for preparing the clear solution, MAI concentration, DEA/MAI molar ratio (R), and H₂O/MAI molar ratio (W), were determined. When a suitable plate was dipped into the resulting clear solution, pulled up, dried and heated (600°-650°C) in air, amorphous spinel thin film was obtained. The maximum thickness of the uniform and transparent films was about 100nm, and thicker films could be prepared by repeating the procedure. The refractive indices of the films were 1.60-1.72. They decreased with increasing film thickness. A crystalline film could be formed on a Si-wafer by the heat-treatment around 800°C, but the many cracks were observed in the resulting film. The film on a quartz glass plate remained amorphous at 800°C due to the reaction with the plate, and was converted to cordierite above 1200°C. The film on a glass plate also seemed to react with the glass plate at temperatures as low as 600°C.

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Alumina granules were prepared by gelation of ammonium alginate binder. The alumina granules were prepared by the following procedures: slurries of alumina with the binder were sprayed into a solution of aluminum sulfate, then formed gel particles were dried. The granules were nearly spherical with a density of 2.0g/cm³, and the average granule size could be controlled arbitrarily within the range of about 50-5000μm. The angle of repose and compressibility of the granules with the size of 74-210μm were 25°-27° and 7-8%, respectively. These results indicate that the granules are free-flowing powders. The properties of granule compacts such as green density and compressive strength were also measured.

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The crystallization of glass/ceramic composite was examined, using borosilicate glass and several kinds of ceramic powders. Most composite systems consisted of borosilicate glass and ceramics formed cristobalite during firing, whereas those specimens that include alumina or aluminum nitride did not form any crystal.
The addition of alumina or a aluminum nitride powder is effective means of preventing the formation of cristobalite. The reason for this may be related to aluminum ions.

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The chemical shift of non-bridging to bridging oxygen in XPS O_1s spectra is known to depend on the type of modified cation. Since the chemical shift is closely related to the ionic character of bonds, electronegativity of cations seems to be a useful parameter to interpret this dependence. Our semiquantitative theoretical treatment has confirmed the significant contribution of electronegativity to the chemical shift. The estimated correlation parameter for modified silicate glasses is comparable with that obtained from carbon fluoride polymers.

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Bending test specimens made of silicon nitride ceramics were indented with a Knoop pyramid at intervals of 100-5000μm, and four-point bending strength was measured at room temperature. The bending strength increased with decreasing crack interval for the crack interval smaller than 500μm. This was attributed to the interference of stress field around the Knoop cracks. The influence of surface layer removal on the bending strength was studied for the specimens with many surface cracks introduced during the previous machining process. No difference was observed in the bending strength when the surface layer of less than 10μm was removed. This invariability of strength with the surface removal was also attributed to the interference of the stress field.

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The ion exchange abilities of two kinds of porous glasses with pore diameters of 4 and 48nm was studied in the aqueous solutions of M(NO₃)_n (M=Li, K, Mg, Ca, Mn, Co, Ni, Cu, Zn, Cr, Fe), and NiX (X=Br₂, I₂, SO₄, (NO₃)₂, (ClO₄)₂, C₂O₄, (CH₃CH(OH)COO)₂). The ion exchange ability of Fe³⁺ was high, but that of the other chemical species were also the same. Porous glasses were modified by treatment with trimethylchlorosilane (TMS), γ-aminopropyltriethoxysilane (γ-APTES) and 1, 3-propanesultone (PS). The porous glass treated with TMS had no ion exchange ability. The ion exchange ability of glass treated with PS was three times and by γ-APTES was ten times as high as that of the untreaded glass.

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Local structures around Ce⁴⁺ ions in stabilized tetragonal zirconias with the chemical compositions of 86ZrO₂⋅10CeO₂⋅4YO_1.5 (Ce 10) and 93ZrO₂⋅4CeO₂⋅3GdO_1.5 (Ce 4) were studied by Ce L_III EXAFS (extended X-ray absorption fine structure) analysis. Using CeO₂ crystals (Ce-O=2.343Å) as a reference sample, the average Ce-O distances for both Ce 10 and Ce 4 samples were estimated to be 2.32Å and average Ce-cation distances for Ce 10 and Ce 4 samples to be 3.62 and 3.61Å, respectively.

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Refractoriness and mineral compositions of various kinds of Amakusa pottery stones (218 samples) were measured by thermal expansion and X-ray powder diffraction methods respectively. The nominal temperature (T_sk) equivalent to refractoriness was predicted by thermal expansion curves. The mineral compositions were determined on the basis of X-ray powder profile refinement method. The statistics of data for T_sk (°C) and mineral compositions, such as quartz (QU (wt%)), sericite (SE (wt%)), kaolin (KA (wt%)), albite (AB (wt%)), calcite (CA (wt%)), siderite (SI (wt%)), showed a high correlation between them with the correlation coefficient of 0.981, which was expressed by T_sk=1404+2.98QU+0.00SE+1.72KA-3.20AB-23.2CA-24.4SI.

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An additive effect on the pressureless sintering of boron carbide is investigated. Some additive species, Al, TiB₂, and AlF₃ show a remarkable densification effect upon B₄C. The Al-addition provides the best sintered body with the highest bulk density of 95% by means of the firing condition of 2200°C for 30min under Argon flow. An addition of SiC prevents the densification process. The additive species except for SiC tend to restrain the grain growth and the pore growth, acting probably as an inhibitor for the surface matter transport.

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A new method for preparing gels as a precursor for SiO₂-M_xO_y (M=Al, Ti, Zr) glasses of an arbitrary composition was investigated. The gels were formed via polymetalloxanes from hydrolytic condensation of metal chelates of ethyl acetoacetate or condensation polymerization of the chelate with silicic acid. The method permitted to prepare transparent gel plates of M_xO_y and binary SiO₂-M_xO_y component systems.

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Chlorine gas sensing characteristics of ZnO/SiC hetero-contact was measured at 20°C in the Cl₂ concentration range from 400 to 1600ppm. The current-voltage curve of the contact showed a rectifying character in which the forward-direction bias is positive on SiC. The current at the forward bias decreased with increasing Cl₂ concentration up to 1600ppm. No sensitivity against H₂ and HCl gases was observed. From the capacitance-voltage relations, height of the potential barrier at ZnO surface was found to increase by introduction of Cl₂ gas.

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