The present study was performed in order to clarify how the mechanical strength of the molded product is generated in a course of its production, being prepared from an aqueous slurry consisted of secondary particles of calcium silicate crystals.
Namely, it was investigated in practice how the physical properties such as structural form, apparent density and porosity of secondary particles mutually relate the pressure load upon dehydrating press molding and the mechanical strength of products.
As a result, it became clear that there was a co-relationship among the number of whiskers (chestnut bur) made of calcium silicate hydrate crystal projecting on the surface of secondary particle, other properties such as size, apparent density and porosity shown by oil absorption of secondary particle, pressure load for press molding and the mechanical strength of the resultant molded product, as shown in Table 1. Especially, it was confirmed that the whiskers on the surface of secondary particle had a very large effect to the mechanical strength of resultant molded product.
The mechanism how the mechanical strength of resultant molded product is generated was verified as that secondary particles are inter locked each other in forming a honneycomb structure as shown in Fig. 6.

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Structure of carbons which appeared in plane, spherical and fibrous forms on the clay body was studied by X-ray emission spectra, small-angle X-ray scattering and by high resolution electron micrograph.
X-ray emission spectrum of plane carbon was similar in features to that of graphite in which carbon crystallite is oriented parallel to the basal plane. Spherical and fibrous carbons gave X-ray spectra similar to carbon black in which any parallel orientation of crystallite has not been observed. Small-angle X-ray scattering method revealed that crystallite of surface carbon aggregated each other to make a large cluster. Turbostratic structure of crystallite has been observed in all the high resolution electron micrographs of surface carbon. Electron diffraction pattern showed that crystallite of plane carbon was oriented to the direction of (002) plane. The crystallite size of surface carbon was as tiny as carbon black, which was revealed by X-ray diffraction pattern. In spherical and fibrous carbons, turbostratic structure of crystallite developed three dimensionally, however, in plane carbon, crystallite with turbostratic structure was oriented parallel to the deposit surface and made a large plane which constructed a layer by stacking each other.
It was emphasized that orientation of crystallite in plane carbon was the most characterizing feature of carbon formed on the smoked rooftile.

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The graphite crucible consisting of graphite-silicon carbide-ferrosilicon has high fire-resistance and suitable thermal conductivity and it is quite strong for thermal shock. But the resistance to oxidations is quite weak at high temperature.
To protect this oxidation, several kinds of inorganic fluxing materials are usually added to graphite crucible.
The oxidation of graphite crucible may be affected by the wetting of the inorganic fluxing materials to materials composing the graphite crucible.
In this study, the wetting of inorganic fluxing materials consisting of borosilicate glass and fluoride to materials consisting of graphite-silicon carbide-ferrosilicon was investigated, and the effect of these inorganic fluxing materials upon the oxidation loss of the materials composing the graphite crucible was also investigated. The following results were obtained.
When ferrosilicon content was large and graphite content was small in graphite-silicon carbide-ferrosilicon materials, the inorganic fluxing materials wetted well these materials. The wettability of inorganic fluxing materials became well in the case where cryolite were involved in the inorganic fluxing materials.
When cryolite was involved in the inorganic fluxing materials, the oxidation loss of the materials composing the graphite crucible became very small and the oxidation loss ratio was less than 15% in the case where graphite content in the materials was less than 60%.
The good correlation was found between the wettability of the inorganic fluxing materials involving fluoride to the materials composing of graphite crucible under constant temperature and oxidation loss of the materials composing the graphite crucible.

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The equilibrium pressure and composition isotherms for the Mg₂Ca-H₂ system were measured at 400°, 350° and 320°C up to 70kg/cm². Each isotherm has shown three plateau regions, indicative of three successive reactions taking place, as follows;
i) Mg₂CaH₂→CaH_2-x+2Mg
ii) Mg+CaH_2-xH₂→MgCaH_3.72
iii) MgH₂→MgH_2-y
The new hydride MgCaH_3.72 was purely synthesized by hydriding of MgCa alloy or heat-treating of MgH₂ and CaH₂ mixture at 400°C and 50kg/cm² H₂. This compound is fine powder which is coloured light gray and unstable in air.
From the X-ray powder diffraction pattern, it was recognized that the compound has hexagonal symmetry, a=6.300, c=6.882Å with density 1.92g/cm³ and Z=4.

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Powdery α-tricalcium phosphate [α-Ca₃(PO₄)₂] was treated up to 15 days in boiling aqueous solution of calcium hydroxide or calcium chloride with initial pH's in the range of 6-12.8. The compositional and structural changes of the phosphate treated were investigated by the chemical and X-ray analyses.
The changes were considered to be classified into the following two processes. The one is a hydration process (I) with a structural change to a nonstoichiometric hydroxyapatite (Ca/P molar ratio 1.50), and the other is a process (II) with an increase of the Ca/P ratio up to the stoichiometric value of 1.67, keeping the apatite structure.
Reaction I was accelerated by lowering the initial pH of the solution within the above pH range used here. The reaction is complete within 2h at pH 11.4 [H. Monma, T. Kanazawa, Yogyo-Kyokai-Shi, 84, 209 (1976)], however, at 12.8 the completion of the reaction was not observed even after 15 days. It was considered that the process II is owing to an uptake of Ca²⁺ from solution to solid part or a release of PO₄^3- from the solid. Increasing the concentration of Ca²⁺ had a tendency to increase the reaction rate of II. When the solution contained Cl ions, the Cl ions were considered to be incorporated into the apatite structure. The product formed by the reaction I contained 4-5% H₂O. Water contents of the hydroxyapatites decreased in proportion to the Ca/P ratios. A similar relation was recognized between the thermal decomposition of the apatites and the Ca/P ratios.
Beta tricalcium phosphate, which is unchanged as far as the β-type is treated at pH 11.4 for 2h, could be hydrated by using conditions of low pH's (5.3-6.1) and boiling times of 6-38h.

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Stresses in the glazes of chinaware were measured by a high-temperature-polarizing-microscope during the heating of specimens from room temperature to 700°C. The stress-temperature curve of all non-crazed plates showed a similar path. That is, the compressive stress first decreased with increasing temperature, and it became zero at a temperature (designated as T_S) between 400°C and 560°C, and the stress became tensile; after taking a small maximum, the stress again became zero at a temperature (designated as T_R) around 620°C, and changed to compression; finally through the very small maximum, it was released completely at around 670°C. In the case of crazed plates the tensile stress at room temperature remained almost unchanged up to 530°C, and became zero around 620°C (T_R). After a small peak of compressive stress, it was finally released around 670°C (T_M).
With the assumption that the dimensions of the glaze and the body became equal at the temperature of zero-stress, the thermal expansion curve of the thin layer of glaze on the body was calculated. If the calculated curve of glaze is overlaid with the observed thermal expansion curve of the body in such a way as the two curves cross at T_R, the run of the stress-temperature curve could be clearly explained.
It was concluded that the generation of the stress does not begin at the lower annealing point of the glaze, but begins at T_R, about 20°C to 100°C higher than its transformation temperature. It was concluded also that the glaze layered on the body was subjected to some composition change.

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The effect of particle-size distribution of batch on packing character, permeable character and bonding strength as factors of corrosion and errosion resistance, and spalling resistance were investigated for magnesia brick.
(1) The closer density were obtained when q (particle-size distribution parameter of continuous grading of Andreasen) shifted from 0.2 to 0.4.
(2) The low permeability and low value of the functional structure factor corresponding to permeation of Zagal (F_text) were obtained when q shifted below 0.3.
(3) The high bonding strengths were obtained when q shifted below 0.2, and the log of strength were in good proportion to log of F_text.
(4) The high thermal spalling resistance was obtained when q shifted over 0.3, and the resistance was in good proportion to q. It was presumed that the good mechanical spalling resistance is identified with that of high bonding strength, the good structural spalling resistance is identified with that of low permeable character.
Thus from the results above, the fanction F_text was considered to be very available factor for permeable character, strength and structural spalling of refractories, and it was concluded that the q of batch should be 0.3 for achieving the harmonized character of magnesia brick.

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