Corundum (Al₂O₃) was obtained from boehmite (AlOOH) under hydrothermal conditions at temperatures above 400°C. The grain size of the crystals with definite habit was 10 to 100 microns.
In the present study impurity effects on the crystallization process of corundum in the above reaction have been investigated. It was found that the reaction rate, crystal size and habit, and incorporation of added ions were strongly influenced by temperature change, pH change, and addition of impurities into solution.
These observed data were explained as the results of impurity effects on: (1) solvent structure, (2) solution structure, (3) solubility, (4) diffusion process, (5) nucleation process, and (6) growth process.
In some cases a metastable phase was formed under the influence of certain impurity. Fluorine ion in the solution inhibited the corundum nucleation and caused the formation of tohdite in the corundum stable region. This effect was explained as a change of solution structure, that is, structure change of hydrated poly aluminate ion in the solution by the existence of fluorine ion. It must be noted that the solution structure is an important factor for the crystallization process.
Habit modification of corundum by adding iron group ions as sulfate, nitrate, chloride, hydroxide or oxide was determined. Valency and coordination number of these ions incorporated into the corundum lattice were determined from their visible reflection spectra. Copper ion is not solid soluble in corundum if sulfate ion coexists, while it is solid soluble substitutionally as Cu³⁺ in 6 coordinated site if it is added as nitrate, oxide or hydroxide. Judging from the formation mechanism of “Star” corundum, Copper ion seems not to be incorporated into the lattice through the basal plane (0001).

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Beam-bending method that one used to measure the sag point of glass was tried to apply to the viscosity measurement of the relatively unstable glasses. An electrical circuit making connections between the differential transformer and the recording millivoltmeter was newly designed. This enables the viscosity measurement in range of 10⁷-10¹⁶ poises involving annealing point and sag point. Annealing point of a commercial soda-lime glass measured by this method coincided with that obtained by the fibre-elongation method. Furthermore, results of viscosity measurements of glasses in the systems of Li₂O-B₂O₃-SiO₂-Al₂O₃, Li₂O-Al₂O₃-SiO₂ and Na₂O-Al₂O₃-SiO₂ were given. The glasses in the two former systems are so apt to crystallize or separate into two phases at a temperature near the sag point that they can hardly be obtained in a form of relatively long fibre as homogeneous state. The present method is especially suited for measuringt he annealing point and sag point of glass in case that the glass to be subjected cannot be got in a large amount because of the preciousness or the experimental situation.

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Formation and growth of chrysotile fibers were investigated under hydrothermal conditions with addition of alkali halides to chrysotile composition of raw materials mixture of silicic unhydride and magnesium hydroxide.
At first, formation of serpentine was studied by X-ray diffraction for short period of reactions at relatively low temperatures. Then serpentine was formed with addition of potassium bromide, but not formed only from raw materials. Moreover for prolonged reaction time at elevated temueratlire, 50μ length of the fiber was easily produced with that addition.
By adding magnesium bromide, about 3mm of the fiber was grown under the same condition as the above. In this case, however, slurry of the mixture was weakly acidic by hydrolysis of magnesium bromide, therefore the slurry was gradually dehydrated in process of the reactions with iron metal placed in the bottom of autoclave.
For the above results, the effect of bromide for formation of chrysotile was deduced that structure of magnesium bromide was the same CdI₂ type as brucite which was outer layer of chrysotile. And also at process of formation and growth, the slurry was concentrated by the dehydration to state as sol, where would be thought that dissolved polysilicic acid combined brucite with Br partially substituting to site of (OH).

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For the purpose of obtaing a low loss sintered glass-ceramics, behaviors of oxide and oxyfluoride glasses during heat-treatment were investigated. The systems investigated were PbO-ZnO-B₂O₃ and PbF₂-ZnO-B₂O₃. From the oxide glass, 2PbO⋅ZnO⋅B₂O₃ was crystallized by heat treatment, while from the oxyfluoride glass the oxyfluoride crystal contaming Pb and Zn was crystallized primarily after phase separation due to spinodal decomposition and then this crystal transformed to PbO⋅2ZnO⋅B₂O₃.
Volume resistivity and activation energy of electrical conduction of the oxide glass decreased, as crystallization proceeded, and on the other hand, those of the oxyfluoride glass increased as oxyfluoride crystal appeared, but when the crystal transformed to PbO⋅2ZnO⋅B₂O₃, by further heat-treatment at higher temperatures, volume resistivity and activation energy decreased sharply.
Main conduction mechanism of the oxide glass was considered as cationic conduction related to Na⁺ ions, and that of oxyfluoride glass was anionic or vacancy conduction that related to F^- ion, or F^- vacancy or F^- interstitial.

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Already, it has been well known that an “absanding phenomenon” occurs at some times after the surface of hardened body which was mainly consisted of the granulated blastfurnace slag, for example, such as super-sulfate cement, was exposed under atmosphere. The practical use of super-sulfate cement is still now obstructing by this phenomenon.
Though it has been suggested that this phenomenon may be mainly caused by the carbonation of calcium compounds in the surface layer of the hardened body made from super-sulfate cement etc., its detailed study has still not been undertaken.
The authors investigated electronmicroscopically the difference of the hardened structure between a neat paste of portland cement and a paste which is mainly consisted of the granulated blastfurnace slag, in the both cases that the hardened body is exposed under atmosphere and not.
In general, all the clinker minerals of portland cement contain a larger quantity of lime than that of lime required for the formation of its normal hydration products. Therefore, these excess lime liberated from each particle of cement in the hydration are present as the crystallized calcium hydroxide or the amorphous ones at every place in the hardend body of portland cement paste. The calcium hydroxide and some portions of the hydration products in the surface of its hardened body react with CO₂ in atmosphere. Then, the tight and continuous coatings consisted of calcium carbonate are formed gradually on the surface of hardened body for some times after its surface comes into contact with CO₂. It is considered that this coatings are very available for the prevention of the penetration of CO₂ inside the hardened body.
On the other hand, the excess lime is not contained in the cement which is mainly consisted of the granulated blastfurnace slag that a large amount of lime is required for the formation of its hydration products. This cement has only a small amount of portland cement or calcium hydroxide as the accelerating agents for the hydration. The tight protective coatings which are observed in the structure of hardened body of portland cement can not be formed by the additional accelerating agents in that of hardened body of super-sulfate cement. Besides, considering the poor rate of hydration, it is natural that the structure of hardened body is so porous that CO₂ can be easily penetrated inside the hardened body. In fact, a large amount of the coarse crystals of calcium carbonate are partially produced on the surface and in the layer under surface of hardened body which is mainly consisted of the granulated blastfurnace slag.
Consequently, the bonds among the hydration products are broken by the formation of these coarse crystals of calcium carbonate and subsequently the “absanding phenomenon” is occurred.

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For the purpose of investigating the structure of glass and initial stage of plase separation of sodium borosilicate glass, pore size distribution of porous glass which was obtained by acid leaching of sodium borosilicate glass heat-treated at 540°C was determined by nitrogen adsorption and direct transmission of electron microscope. Cranston-Inkley method was applied to calculate the pore size distribution and the calculation was performed by using electronic computer. The results obtained by both methods were in good agreement.

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