It was suggested by Jackson that higher firing temperature would destroy the dielectric properties of wollastonite ceramics by the conversion of wollastonite (β-type) into pseudowollastonite (α-type). To confirm the possible causes of the destruction of the dielectric properties of wollastonite ceramics, the dielectric constant (ε) and dissipation factor (tanδ) of β-wollastonite obtained on two different methods (that is, a powder dispersion method and measurements using hot pressed bodies) were compared with those of α-wollastonite.
It was found that the β-wollastonite powder obtained on firing the glass with CaO⋅SiO₂ composition at 1000°C for 2 hours has good dielectric properties (ε=6.5, tanδ=4.2×10^-4) and the α-wollastonite powder obtained on firing the same glass at 1400°C for 2 hours also has similar properties (ε=8.6, tanδ=5.0×10^-4). ε and tanδ of the β-wollastonite bodies fabricated by hot pressing the glass powders with composition of CaO⋅SiO₂ added 1wt% of Al₂O₃ were found to be 7.4 and 3.9×10^-4, and those of the α-wollastonite bodies fabricated by hot pressing the α-wollastonite powders to be 8.4 and 4.4×10^-4, respectively. From the results of these measurements, no difference in the dielectric properties between β- and α-wollastonite was recognized.
It was supposed through the observation by optical microscope that the destruction in the dielectric properties of wollastonite ceramics fired at high temperatures was due to the microcracks produced in the glass matrix of sintered bodies by the difference of thermal expansion coefficient between α-wollastonite crystals and the glass matrix during cooling.

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Two self-bonded SiC bodies which contain about 12wt% free Si were joined with liquid Ge at 1180°C for 10min in vacuum. The thickness of interlayer was controlled to be about 20μm or 200μm thick, then 4-point bending strength of joined specimens were measured in vacuum at high temperatures. The strength increased with raising temperature, and the thinner interlayer specimen had a strength as strong as about 40kg/mm² at 1050°C or above melting point of Ge. Electron probe micro analysis of the joint showed the composition of the alloy in the thicker interlayer significantly fluctuated, while for the thinner one Ge had relatively uniform distribution, and the liquid formation temperature of the latter was found to be about 1200°C.

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The present study concerns oxygen defects in the spinel-type ferrite system Zn_1-xLi_xFe₂O₄ by means of X-ray diffractometry, density and magnetic measurements and Mössbauer spectroscopy, comparing with the reference system Zn_1-xLi_0.5xFe_2.0+0.5xO₄.
X-ray diffraction showed that a solubility limit of Li was x=0.20, above which α-LiFeO₂ phase appeared. The lattice constant decreased linearly, and continued to decrease in the compositional range above the solubility limit. It was found by density measurements that oxygen vacancies were introduced by the substitution of Li⁺ for Zn²⁺. X-ray diffraction peak-intensity analysis showed that Li ion occupied 80% of octahedral site for the sample with x=0.10 and 84% for the sample with x=0.20 in the spinel structure.
The sample in the compositional range, 0.0≤x≤0.20 was paramagnetic at room temperature. Neel temperature of the ferromagnetic sample with x=0.30 was 154°C and it increased with increasing Li content. The values of quadrupole splitting in the Mössbauer spectra of the paramagnetic phase increased with increasing Li content. This tendency was remarkable, compared with the reference system. Therefore, the fact was ascribed to the presence of the oxygen vacancies. Furthermore, the Mössbauer spectra of the ferromagnetic materials composed of paramagnetic and magnetic-hyperfine absorption line.

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The chemical durability and the binding mechanism of bioglasses with living tissues have been studied by L. L. Hench. The components contained in those glasses, Na₂O, CaO, SiO₂ and P₂O₅, are regarded as the indispensable components for the bioglass. But these bioglasses studied by Hench have not been made fit for practical use yet, because of a serious defect that the mechanical strength decreases with time after implantation. In the present experiments, the glasses of Na₂O-CaO-SiO₂-P₂O₅-Al₂O₃ series, Na₂O-CaO-SiO₂-P₂O₅-B₂O₃ series and Na₂O-CaO-SiO₂-P₂O₅-B₂O₃-Al₂O₃ series containing Al₂O₃ and B₂O₃ as the new components have been studied on chemical durability and Vickers hardness. Al₂O₃ and B₂O₃ contained in these glasses may be expected to increase the chemical durability and the mechanical strength. The chemical durability was measured on the HCl solution of pH=1.0, pH=3.0 and pH=5.0. Some interesting results are obtained in Vickers hardness. The Vickers hardness of the X series glasses increased with increasing SiO₂. Those of the E and F series glasses exhibited maxima at the mol% ratio, B₂O₃/P₂O₅ equal to unity and at the mol% ratio, (B₂O₃+Al₂O₃)/P₂O₅ equal to two, respectively. These properties were generally determined in connection with the composition. From the measurements of these properties, the bioglasses of E 15, A 20 and A 30 were shown to be better than Hench (45 S 5) glass.

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The basic experimental study on producing the heat-treated lightweight bodies from red mud-scrapped glass compact was carried out by measuring bulk density, water absorption, bending strength and burning shrinkage. Some relations between bloating process of heat-treated compacts and variation of mineral composition were investigated. The results obtained are as follows:
(1) The bulk density and bending strength of red mud compacts heated at the temperature range from 1150° to 1250°C increased rapidly. The mineral composition of the heated compacts consists of hematite, nepheline, ilmenite and/or pseudobrookite.
(2) Bloated bodies could be obtained from compact of the scrapped glass and red mud mixture at the following temperature range:
1150°-1200°C: For red mud 75% and scrapped glass 25% mixture
950°-1050°C: For red mud 50% and scrapped glass 50% mixture
800°-1000°C: For red mud 25% and scrapped glass 75% mixture
According to higher mixing ratio of scrapped glass, the sintering and bloating temperature became lower.
(3) Red mud-scrapped glass compact seems to be bloated by the H₂O gas generated through the formation of nepheline from sodalite contained in the red mud at the softening temperature of the compacts. The red mud containing much sodalite is suitable for a raw material of bloated body.

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Densification and phase transformation of Si₃N₄ were studied by high pressure hot-pressing without additives. The α to β phase transformation rate was accelerated by the application of pressure. The fracture surface showed the existence of self-bonding and formation of polyhedrons. When the α-Si₃N₄ powder was hot-pressed at 1600°C under 3.0GPa, a fully dense body was obtained at about 10wt% of β phase, and the maximum Vickers microhardness of 2200kg/mm² was observed at about 40wt% of β phase transformed. There was no difference in densification behaviors in either case when α or β phase Si₃N₄ was used as starting materials.

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Crystal structures of the high temperature form (γ_II) of γ_II-Li₂CoSiO₄ and γ_II-Li₂MgSiO₄ and the low temperature form (β_II) of β_II-Li₂ZnSiO₄ have been determined from X-ray powder data on the basis of known structures, γ_II-Li₂ZnSiO₄ and β_II-Li₂CoSiO₄. The three compounds of the γ_II form (space group P 2₁/n) are isostructural with each other. The two compounds of the β_II form (space group Pbn 2₁), which are also isostructural with each other, show the same disorder as that found in a single crystal of β_II-Li₂CoSiO₄. Both the γ_II and β_II forms consist of subcells, P and Q, each having two units of Li₂MSiO₄ related by an n-glide; the symmetry elements connecting subcells P and Q characterize the formation of the two polymorphic forms. All cations are coordinated tetrahedrally by O atoms.

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Indonesia is dominated by various kinds of volcanic ejecta such as obsidian, lahar (lava) and trass which is similar to shirasu in Japan. Some characteristics of these raw materials and samples prepared by drying, milling (for only obsidians) and sieving, were investigated as compared with those of shirasu. Bloated lightweight particles were tried to be produced from these samples by heat treatments, and their physical properties were measured. All the samples prepared could be used as raw materials of bloating lightweight particles. The results obtained are summerized:
(1) The raw materials are neutral or acidic volcanic ejecta: two kinds of obsidians in Bogor and in Garut, West Java; one kind of lahar in Garut; three kinds of trasses in Sukabumi, West Java, in Kayutanam and in Bukittinggi, West Sumatra. Volcanic glass is contained in the raw materials as the major component, and quartz and feldspar are as minor component. Lahar and trass have similar particle size distribution to that of shirasu.
(2) The platy or massive volcanic glass particles with smooth surface which is suitable for bloating, are contained mainly in all the samples prepared. The state of the water contained in the volcanic glass particles can be classified into three groups by DTG; the group of obsidians, the group of lahar and trasses in Sukabumi and Kayutanam, and the group of trass in Bukittinggi and shirasu.
(3) Bloated lightweight particles with low apparent density can be obtained with high percentage of yield from the prepared samples of obsidian in Bogor by continuous heat treatment at the maximum temperature 1000°C near the central part of kiln and in residence time 5min from inlet to outlet. However, longer residence time than 5min at the maximum temperature 1200°C or higher maximum temperature than 1200°C is necessary for obsidian in Garut.
(4) Through present continuous heat treatment for lahar, yield of bloated lightweight particles was almost same value. However, the lowest apparent density of bloated lightweight particles in fine size range can be obtained by continuous heat treatment at the maximum temperature 950°C and residence time 1min.
(5) Because of low glassy part content in trasses, separation of volcanic glass is necessary, especialy for trass in Sukabumi. Bloated lightweight particles which is similar to Shirasu Balloons, can be obtained from prepared samples of trasses by continuous heat treatment at the maximum temperature 950°-1000°C and in residence time 1min.

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