The stability region of chrysotile in the system MgO-SiO₂-H₂O has previously been investigated by Bowen and Tuttle, showing that chrysotile can be prepared at temperatures below 500°C, and at water vapor pressures from 2, 000 to 40, 000lb/in² and break down into forsterite, talc and water vapor under hydrothermal conditions above 500°C. But the treated pressures were much lower, as described above.
This research was carried out as a part of the study on the synthesis of fluor-chrysotile [Mg₆Si₄O₁₀(F)₈]. Mixtures of SiO₂ (amorphous) and Mg(OH)₂ (brucite) specimens corresponding to chrysotile composition, and natural chrysotile were treated at temperatures ranging from 300° to 600°C and pressures from 2 to 40 kb using a simple squeezer type high pressure apparatus. The present experimental results have indicated that chrysotile can not be formed at 10kb and temperatures above 510°C, at 20kb above 530°C.
The pressure-temperature curve of the equilibrium, chrysotile _??_ talc+forsterite+water vapor, was appeared to be lying on the extrapolated line of Bowen and Tuttle's pressure-temperature curve. The value of (∂P/∂T) was about 8.0×10²(bar/deg.) and was in good agreement with that calculated by thermodynamic data. The synthesized chrysotile crystal was always appeared as minute tubular, not platy and fibrous by photographs in the electron microscope and had the low refractive indices of chrysotile.

抄録全体を表示

ガラスの微構造の決定は, 最近主に電子顕微鏡によって行なわれてきたが, 吸着法によっても多孔体の細孔構造が定量的に決定される. 本研究では多孔体の細孔構造を窒素吸着により決定する方法を検討した. 吸着多分子層膜の厚さを6次の函数で示して, 細孔半径が相対圧との函数関係で取り扱えることを示した. そしてケルビン式と吸着多分子層膜の厚さの影響を考慮して理想細孔構造モデルに対する吸着曲線の算出式を考案した. さらにこの算出式を使用して定量的な吸着曲線及び脱着曲線を電子計算機により決定した. 算出した吸着曲線群を使用して, 実験により求めた吸着曲線から細孔半径, 比表而積, 細孔分布が簡便に推測できることを述べ, さらに細孔構造, 特に細孔形状を実験により求めた吸着曲線より推定する方法を提案した.

抄録全体を表示

Vapor transport reaction of sintered polycrystalline MgO and quartz glass was examined using vapor transport couple. MgO and SiO₂ were separated by 0.1mm platinum wire and firing was carried out at 1400°C for 24hrs.
X-ray examination of the surface of MgO and SiO₂ did not establish the development of reaction product. However, electron microprobe X-ray analysis proved the vapor transport of Si (or Si oxide) to the surface of MgO as well as that of Mg (or MgO) to the surface of SiO₂. In addition, it was found that the amount of Si on the MgO surface was considerably larger than that of Mg on the SiO₂ surface.
Previous study using MgO-SiO₂ contact diffusion couple indicated that the reaction product mainly developed on the SiO₂ side. Therefore, it will be concluded that vapor transport did not play an important part on the development of the reaction product in the solid state reaction.
Platinum wire had an shielding effect on the vapor transport of Mg, but, on the other hand, there was evidence of the rapid movement of MgO toward SiO₂ along the surface of platinum wire.

抄録全体を表示

The relationship between the pore structure and characteristics such as the expansion or drying shrinkage of calcium sulfoaluminate (CSA) cement mortar has been studied by means of Cranston-Inkley method using a digital computer and of X-ray diffraction analysis. In order to examine the pore structure of mortar specimens, the adsorption and desorption of N₂ gas were measured. In addition, the pore size distribution curves and specific surface areas of CSA cement mortar and portland cement mortar were calculated by means of Cranston-Inkley method. It was found that the hysteresis of the adsorption and desorption isotherms was more remarkable for the specimens cured in water than in air. The existence of hysteresis is related to the complexity of the pore structure. The pore size distribution curves and specific surface areas are much the same with CSA cement as with portland cement. The mechanical strength is not very affected with the addition of CSA up to about 10%. According to the X-ray diffraction patterns, the amount of trisulfate hydrate (TSH) increases with the addition of CSA in the specimens cured in water, but is not always related to the degree of expansion due to hydration of specimens.

抄録全体を表示