β-dicalcium silicate was synthesized and hydrated with/without alkalies at different temperatures. Alkalies accelerated the hydration of β-C₂S and influenced the polymerization of calcium silicate hydrate. KOH and NaHCO₃ caused excessive and early liberation heat of the β-C₂S. The effect of NaHCO₃ was more significant than that of KOH on the acceleration of hydration. The curing temperature was also an important factor in the acceleration of the hydration of β-C₂S; the hydration was occurred much more actively at 40°C than at 20°C. The controlled β-C₂S showed a much greater degree of polymerization of calcium silicate hydrate than did the alkali-added β-C₂S. The hydrates of β-C₂S were influenced by alkalies and temperature. The controlled β-C₂S showed needle-like and wide needle-like shapes of calcium silicate hydrates, while the alkalie-added β-C₂S presented long and wide needle-like shapes and crumbled foil-like shapes of calcium silicate hydrates. The calcium silicate hydrates formed at high temperature exhibited also crumbled foil-like shapes.

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The essential requirement for an artificial material to bond to bone is formation of bonelike apatite on its surface in body environment. The formation of the apatite has been proposed to be induced by silanol groups on the surface of the material. In the present study, the mechanism of apatite formation induced by the silanol groups was investigated in a biomimetic process. A collodion film supported by a titanium grid which faced to a CaO-SiO₂-based glass was soaked for various periods in an acellular simulated body fluid with ion concentrations nearly equal to those of the human blood plasma. The film was observed by a transmission electron microscope equipped with energy dispersive X-ray spectrometer. Silicate ions rich in silanol groups, which were released from the glass, were attached onto the collodion film. They first combined only with calcium ions in the fluid to form a calcium silicate. Later, the calcium ions in the calcium silicate combined with phosphate ions in the fluid to form an amorphous calcium phosphate with a low Ca/P atomic ratio. The amorphous calcium phosphate, increasing its Ca/P atomic ratio, eventually transformed into a crystalline apatite. This indicates that the silanol groups induce the apatite formation not directly but through the formation of calcium silicate and amorphous calcium phosphate with a low Ca/P atomic ratio. The formation of calcium silicate at the initial stage might be attributed to interaction between negatively charged silanol groups and positively charged calcium ions.

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Amorphous Al₂O₃-SiO₂ xerogels were prepared by coprecipitation and their thermal stability was investigated by powder X-ray diffraction, N₂ gas adsorption and transmission electron microscopy. Xerogels with chemical compositions of 4, 30, 60, 80 and 100mol% Al₂O₃ were prepared by adding conc. NH₄OH to an ethanol solution of aluminium nitrate nonahydrate (ANN) and tetraethylorthosilicate (TEOS). Deionized water was added to the solution to adjust the molar ratio H₂O/TEOS≥18. The xerogels obtained by calcining at 300°C were heat-treated at 800-1500°C for 2h at heating and cooling rates of 10°C/min. The specific surface area (S_A) of the xerogels heated at high temperatures showed large composition-dependent variations, the samples containing 60 and 80mol% Al₂O₃ having much higher S_A values than the other xerogels. This is attributed to retarding effect of the SiO₂ component for transition into α-Al₂O₃ phase by avoiding direct contact of γ-Al₂O₃ particles. On the other hand, the S_A values of the SiO₂-rich and Al₂O₃ xerogels decreased markedly at about 1000-1100°C with increasing of pore radius (r_P). This steep decrease in S_A and increase of r_P are attributed mainly to densification by a viscous flow mechanism accompanied by abrupt particle growth in the SiO₂-rich xerogels and by a particle growth mechanism accompanied by the γ-to-α-Al₂O₃ phase transition in the Al₂O₃ xerogel. The thermal stability of the xerogels is compared with those of other previously reported porous ceramics.

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Amorphous materials in the system xLi₂S⋅(100-x)SiS₂, where x ranged from 50 to 70mol%, and (100-y)(0.6Li₂S⋅0.4SiS₂)⋅yLi₄SiO₄, where y ranged from 0 to 10mol%, were synthesized by mechanical milling of crystalline starting materials, Li₂S, SiS₂ and Li₄SiO₄. At the compositions with large amounts of Li⁺ ions, a part of crystalline Li₂S used as a starting material remained in the milled powder samples. It was found that the milled powder samples in both systems obtained by mechanical milling exhibited high conductivities in the order of 10^-4S·cm^-1 at room temperature in spite of the presence of small amounts of Li₂S crystals. The conductivity values of the pelletized samples of xLi₂S⋅(100-x)SiS₂ powders maximized at the composition of about x=60. On the other hand, the conductivities in the composition range with y≤5 in the system (100-y)(0.6Li₂S⋅0.4SiS₂)⋅yLi₄SiO₄ were nearly the same values in the measured temperature range and higher by a half order of magnitude than those at the composition with y=10. The transport number of lithium ions of the amorphous materials after mechanically milled was almost unity and the potential window was wider than 10V at room temperature.

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The feasibility of microwave sintering of multilayer ceramics containing capacitor was examined. Simultaneous sintering of ceramic substrates, metallic electrodes and a dielectric layer was performed at low temperature and short soaking time by microwave. Higher dielectric constant and smaller deformation were observed in the dielectric layer and substrates, respectively, as compared with the conventional process. Moreover, a dielectric constant more than 6000 was obtained by using electrodes with Cs additive. It was confirmed that diffusion of glass elements into the dielectric layer and Ag diffusion into the substrates were repressed by the Cs additive in electrodes and microwave sintering.

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Monolithic β-Si₃N₄ ceramics with additives of 5mass% Y₂O₃ and 5mass% Al₂O₃ were prepared by gas-pressure sintering at 2023K at a N₂ pressure of 1MPa with 50mass% Si₃N₄/50mass% BN powder bed. When β-Si₃N₄ was heat-treated at 2023, 2073 and 2123K at the N₂ pressures of 0.1 and 1MPa with a carbon powder bed, a surface layer containing mainly SiC was generated. Inside the SiC layer, α-SiAlON was generated. Moreover, melilite (Y₂Si₃O₃N₄) was observed when the N₂ pressure was 0.1MPa. The reasons for the generations of α-SiAlON and melilite were thought to be as follows. During the formation of the SiC layer, the liquid phase with Y- and Al-elements was excluded from the original surface layer. The liquid phase with Y-and Al-elements concentrated between the SiC layer and the β-Si₃N₄ bulk. Finally, Y and Al in the liquid phase reacted with β-Si₃N₄, and α-SiAlON and melilite were formed.

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The morphology change on glass surface caused by localized corrosion was studied for soda lime silicate glass using an atomic force microscope (AFM). AFM observation was carried out on the glass surfaces after immersion in aqueous solutions with various pHs and for various immersion times. Observation of crack tip morphology was also made for the surface of soda lime silicate glass after indentation. It is shown that surface roughness does not change in the pH range from 1.0 to 10.2, and abruptly increases at a pH 11.7, increases with increasing the immersion time. Stress corrosion around the crack tip was observed at pH 11.7, but not at pH 2.0. XPS results proved that the morphology change on glass surface caused by localized corrosion arises from the sorption of K⁺ ion existing in the test solution.

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Al-substituted tobermorite has been successfully synthesized by hydrothermal treatment at 180°C in the presence of NaOH solution, using waste incineration fly ash as a starting material, pretreated with repeatedly washing and heating at 800°C. The relation between Al-substituted tobermorite yield and synthetic conditions has been also examined. The pretreatment was essential to convert fly ash into Al-substituted tobermorite with reproducibility, and the Al-substituted tobermorite yield was found to reach a maximum in the fly ash treated with 2M (mol·dm^-3) NaOH for 20-30h. The order of Al-substituted tobermorite yield was 2M>>3.5M≅1M>0.5M>>6M, with respect to NaOH concentration. With increasing the NaOH concentration and extending the reaction time, sodalite and cancrinite generated as minor phases. The fly ash treated with 2M NaOH for 30h showed the best removal characteristics and took up about 0.5mmol·g^-1 for both Cs⁺ and NH₄⁺ ions. The uptake amounts of resulting products were found to depend on the Al-substituted tobermorite yield.

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Effect of doping amount of CaO on the antibacterial activity of ZnO powders was studied by conductance method and colony count method under the condition of enabling and not enabling bacterial growth, respectively. ZnO-CaO solid solution powders when CaO was added in a molar ratio (CaO/ZnO)<10mol%, ZnO-CaO solid-solution powders were synthesized by heating at 1400°C for 6h in air, but ratios>10mol% resulted in a residual CaO phase in addition to ZnO-CaO solid solution. After milling the powders by planetary ball mill, the average particle size of the obtained powders was 0.5μm and used in the test of growth-inhibition of bacteria. Evaluation by the conductance method revealed that the increase of CaO in ZnO-CaO powders resulted in a decrease of the growth inhibitory effect against Escherichia coli and Staphylococcus aureus. In addition, the inhibitory effect against S. aureus was found to be stronger than that against E. coli in ZnO-CaO powder slurries. On the other hand, in the case of the colony count method, the killing effect of ZnO-CaO powders on S. aureus markedly increased with increasing the excess CaO in ZnO-CaO powders, i.e., the deposition of CaO from ZnO-CaO solid solution.

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The effect of granule properties on the microstructure of sintered silicon nitride bodies and their strength variation was examined. Commercially available silicon nitride, alumina and yttria powders were used as the raw materials. The granules were fabricated under three different spray drying conditions. Employed were several characterization techniques which are capable of directly observing the internal structures of granules, green bodies and of sintered bodies. The strength variation of the sintered bodies was correlated with the dimension of large pores detected by the direct observation of the internal structure of sintered bodies. These pores were originated from the inherent flaws in green compacts. These inherent flaws were introduced by non-uniform packing of powder particles via the incomplete collapse of dimples in granules and also from the cavities between granules. Furthermore, it was emphasized that these large pores in the sintered body was controlled by the granule size, dimple size, as well as the yield stress of granules.

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Thermal shock fracture testing was performed on both alumina and silicon nitride by water-quenching method. Disk-shaped specimens in this study were preferred because of their easier processing and smaller volume as composed to the pencil-shaped specimen recommended by JIS. Thermal stress in the specimen during quenching was calculated by numerical analysis in order to evaluate the critical temperature difference, Δθ_c. The heat transfer coefficient of water was previously measured on a Ni-specimen under experimental conditions similar to the present thermal shock test. Observed values of Δθ_c agreed well with the calculated values for alumina, but disagreed by about 150K in silicon nitride.

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Translucent γ-alumina and θ-alumina sheets were obtained from polyhydroxoaluminum (PHA)-hexadecyltrimethylammonium ion (HTM) composite gels upon heating at 700 and 1000°C, respectively, provided that the corresponding mixed solutions of PHA-HTM were hydrothermally treated at 140-150°C before gelation. Dilution of PHA solution below 6.0% was also indispensable for obtaining translucent activated aluminas. The effect of hydrothermal treatment on diluted solutions resulted from the promotion of hydrolysis of PHA ions to form colloidal particles. Translucency of activated aluminas is due to their sharp monomodal pore size distribution. The pore size ranges from 8 to 21nm, depending on both the hydrothermal temperature and the calcination temperature. All these facts indicate that pore sizes of γ- and θ-alumina are controllable.

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Stress concentration behavior of the O-ring and C-ring test specimens compressed by diametrically opposite external concentrated loads has been analyzed using a finite element method. The ring compression strength for three kinds of tubular ceramic filter was evaluated using the O-ring and C-ring test specimens. It was indicated in this experiments that the fracture strength of both internal and external surfaces of tubular ceramic filters could be evaluated using the O-ring and C-ring tests, respectively. The experimental results showed that the O-ring compression strength and rigidity of silicon carbide-based filters were longer than that of alumina filters, silica- and magnesia-based filters were longer than alumina- and silica-based filters. It was also confirmed that a large difference in fracture strength of the internal and external surfaces can be observed in the case of silicon carbide-based filters.

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To clarify the electrical discharge machining (EDM) mechanism of insulated ceramics with an assisting electrode method, the waveforms and displacement curve of tool electrode were investigated during electrical discharge process, with emphasis on the following factors: (1) The effects of EDM conditions on machining rate, wear of electrode, surface roughness and stability of discharge. (2) The variation of discharge stability corresponding to the machining process. From the obtained results, it appeared that an electrical conductive layer was created on the machined surface by the generation of both long pulse and concentration discharge pulses. The surface roughness decreased with increasing the ratio of these abnormal pulses. To decrease the generation of abnormal pulses, machining was carried out in carbon-powder-mixed machining fluid. As a result, the surface roughness was markedly improved according to on increase of the normal discharge ratio and discharge dispersion phenomena.

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This paper describes the friction and wear properties of carbon/silicon carbide composites in comparison with that of porous silicon carbide and dense silicon carbide. Tests were conducted in ambient air, using a pin-on-disk friction test apparatus. The friction and wear properties of these materials varied according to the combination of pin and disk materials. The carbon/silicon carbide composite containing the largest carbon volume (about 40vol%) showed the lowest values of friction coefficient and specific wear among all the investigated materials. In addition, it also showed a stable behavior with respect to sliding velocity. The friction and wear mechanisms of these materials were discussed according to the morphology of the worn surfaces observed by scanning electron microscopy (SEM).

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Silica skeletons were fabricated from xonotlite using an acetic acid treatment, and using HCl as a comparison. Identification and quantification between xonotlite and silica skeleton were performed successfully from the chemical shifts and widths of the peaks in the ²⁹Si MAS NMR spectra. The evidence for carbonation of the original xonotlite was established by X-ray powder diffraction. All of the acetic acid treated samples were amorphous when the mole ratio between acetic acid and the xonotlite was 12:1. Specific surface areas of the produced silica skeletons were 3-5 times larger than the specific area of the original xonotlite. Transmission electron microscope observations showed that most of the silica particles had a slab-like or needle-like texture for the acetic acid treated samples. The texture was similar to that of the original xonotlite.

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To characterize humidity conditioning ceramics, the relative humidity as a function of temperature (H(T)) was measured using a glass desiccator technique with varying the ambient temperature between 298 and 288K. A logarithmic plot of H(T) was approximately represented by a linear function, and the humidity conditioning ability was evaluated by the slope (B) of such a linear equation (B-value method). Humidity conditioning ceramics, made of several ceramic materials such as Wakkanai diatomaceous shale, calcium silicate and zeolite, were characterized according to their B-values in comparison with wood. The relation between the B-value and the ratio of the exposed surface area of the material to the volume of desiccator was also investigated to extend the efficiency of the B-value method to the large scale of actual applications. It was also found that the B-value method to estimate the humidity conditioning ability for wooden material can be applied to porous ceramics, which had B-values higher than wood. The porous diatomaceous ceramics showed the highest B-value among the ceramic investigates.

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Friction and wear properties of ceramics were measured in water and in ethanol according to the ball-on-disk method with a steel ball. Silicon carbide grains were dispersed in water or ethanol to investigate its abrasive effects. The coefficient of friction slightly decreased in water and much in ethanol compared with that in air. The change of friction behavior due to silicon carbide addition was almost negligible. The wear of the steel ball was nearly identical in air and in water, but greatly decreased in ethanol. Abrasive addition increased the steel ball wear, particularly when harder SiC or Al₂O₃ disk was used. The wear behavior of the ceramic disk was also greatly promoted by abrasive addition in water and in ethanol.

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The ultraviolet transmission characteristics of a calcium meta phosphate glass is reported. A calcium meta phosphate glass was prepared using high-purity reagents and taking care in avoiding contamination during glass preparation. This glass exhibited an excellent transmittance in the wavelength range from 250 to 1500nm (10mm thick) and an ultraviolet absorption-edge wavelength of 178nm (3mm thick). The absorption-edge value was about 60nm shorter than that reported by Kordes et al. Irradiation of 248-nm excimer laser light to the glass induced strong absorption at <300nm and weak absorption in the 350-550nm range. The weak absorption consists of two bands, which are considered to be due to P-O⁽⁺⁾ and Ca^2+(-).

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A new sol-gel route using phenyldichlorophosphine and calcium nitrate as starting materials and 2-ethoxyethanol as solvent has been developed to prepare β-tricalcium phosphate (β-TCP). β-TCP fine particles could be prepared at 900°C 1h, a temperature and firing time lower than that necessary for wet- or dry- preparation (i.e., 1000°C and 16h). The particle morphology of the β-TCP by sol-gel route was columnar-like, with diameter and length 200nm and 600nm long at 600°C. However the morphology of β-TCP at 1000°C was porous materials.

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It is no exaggeration to say that the remarkable development of the Japanese steel industry in the 20th century has been brought about by technological advances in the field of refractories. We may pinpoint two important reasons for the advances in refractory technologies. One is that ceramists in Japan have been producing new refractories based on the evaluation of refractory performance in actual use, together with engineers in the steel industry, and the other is that ceramists in Japan have devoted much effort to the quality control of refractories. This study was the starting point of the present success of the Japanese refractory industry. The authors collected information on 39 types of refractories from domestic and foreign companies, and systematically investigated their chemical compositions, physical properties, refractoriness and slag resistance. It is worth mentioning that this paper contained the first proposal in the world for a testing method of slag resistance by contacting slag at high temperatures. In those days, refractories were tested solely by heating at high temperatures, and therefore the testing method proposed in this paper was ground-breaking. Moreover, it is clear that the authors overacame the difficulty in measuring temperatures accurately during the test whenever we see the word “Shinetsu” in the paper. Therefore, we should appreciated once again the significant contribution of these authors towards the development of ceramic science and technology.

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The author performed systematic research on calcium almino-ferrite phase in portland cement by means of optical microscope and powder X-ray diffraction, and presented 7 reports to the Journal. They are Part I, Vol. 45, No. 533, pp. 279-299 (1937), Part II, Vol. 45, No. 534, pp. 361-373 (1937), Part III, Vol. 45, No. 535, pp. 433-446 (1937), Part IV, Vol. 45, No. 537, pp. 614-631 (1937), Part V, Vol. 45, No. 540, pp. 880-896 (1937), Part VI, Vol. 46, No. 541, pp. 12-20 (1938), and Part VII, Vol. 46, No. 542, pp. 66-76 (1938).
The ferrite phase in portland cement is known to be crystallized from molten liquid containing CaO, Al₂O₃, Fe₂O₃, and SiO₂ together with calcium alminate phase. It was concluded, in the last report of the series, that the composition of calcium almino-ferrite was 6.2CaO:2.2Al₂O₂:Fe₂O₃ when Al₂O₃/Fe₂O₃ ratio of starting mix exceeded 1.4 in the ternary system CaO-Al₂O₃-Fe₂O₃, and that the addition of SiO₂ had no effect on the ferrite composition.
The calcium alumino-ferrite was called celite, similarly to alite and belite, and it was supposed to be a compound with the composition of 4CaO:Al₂O₃:Fe₂O₃. The author found it possible to prepare ferrite phase with any composition in the solid solution series between 2CaO:Fe₂O₃ and 6.2CaO:2.2Al₂O₂:Fe₂O₃, or Ca₂(Al_xFe_1-x)₂O₅ where 0<x<0.7, for the first time. And all text books in cement chemistry show the phase equilibrium diagram as Fig. 1.
In addition to the micro-structure observation with optical microscope, crystalo-chemical consideration based on X-ray diffraction determination was applied, and the research out put has contributed not only to ceramic science and but also practical cement technology to a great extent till now, in ceramic field including cements, refractories, and so on.
The contribution of the author to ceramics field spread in wide range and extra-ordinal. One of those is the introduction of powder X-ray diffraction technique to ceramic research. It was really hard for him to assemble X-ray apparatus for himself and find his way to analyze experimental results. He started to evacuate the tube in the morning, and the X-ray experiment was continued through night. But, today, it is one of the most popular and important tool for ceramists, we depend strongly on him today and in future.
Explanatory article can be seen at Vol. 41, pp. 251-259 (1933), showing illustration of X-ray tube at that time as Fig. 2. And the earliest research report, Vol. 42, pp. 313-322 (1934), is on calcium aluminate, as an out put from fundamental research on castable refractory.

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