The synthesis of finely-divided silica from silicon tetrachloride and oxygen by the vapor phase reaction was investigated at 1200°C, with an emphasis on the effects of reaction conditions on the particle size distribution of the products. The results were as follows:
1) The reaction between silicon tetrachloride and oxygen starts at about 800°C, then takes place rapidly at 1000°C, and reaches to the 100% conversion above 1100°C (Fig. 3).
2) The products were amorphous and nearly spherical particles with the diameter of 150 to 1000Å (Fig. 6). The size distribution became narrower and the mean particle size did smaller with the decreasing in the oxygen concentration or the increasing in the silicon tetrachloride concentration (Figs. 7 and 8). Such effects of gas composition on the particle size distribution were qualitatively explained in terms of the relative change between the nucleation and growth rates with the compositions.
3) The surface area of products was measured about five times as large by BET method as electron microscopic method (Table 2). This means that the particle produced has pores or an uneven surface.
4) The reaction rate of SiCl₄-O₂ system at 925°C was proportional to the partial pressure of silicon tetrachloride, whereas with oxygen pressure it increases rapidly at the low pressure and then did gradually above 0.06 atm. (Fig. 10). The partial pressure dependency of nucleation and growth rates was discussed briefly.

抄録全体を表示

An attempt has been made to measure the apparent viscosity of a glass was Li₂O⋅2SiO₂ and its viscosity varing in process of time was continuously measured at constant temperatures ranging from 487° to 515°C by a fiber-elongation method.
In order to separate the viscosity of matrix glass from the apparent viscosity, these data were analyzed in connection with the shape factor and the volume fraction of lithium disilicate crystallites dispersed in the glass by Simha's formula concerning the relative viscosity of dilute dispersed system.
Despite of the existence of the possibility of the formation of pre-nucleation group in this glass, the variation of the viscosity of matrix glass with time was analogus to that of ordinary soda-lime silica glass which gradually approaches to the equilibrium value.

抄録全体を表示

It is well known that valence, coordination, electronegativity of atom in the compounds and minerals may all have some kinds of effect on X-ray emission spectra, especially those involving the transitions from the valence state. But there have been no effective technologies to measure the emission spectra in ultra soft X-ray region, so such kind of measurement was limited in the short wavelength region using the apparatus with double crystal. The authors tries successfully to measure the OK_α, CrL_α and MnL_α by specially designed apparatus which is improved to be able to count the low energy secondary X-ray in sufficient intensity with good resolution.
The OK_α emission spectra from various compounds classified to three distinguishable groups chosen on the basis of the spectrum shape. Group 1 contains those bands which show structure on the high energy side such as potassium permanganate and chromate compounds. Group 2 show structure on the both side of the main bands such as barium and potassium carbonate, and Group 3 includes symmetrical main spectra such as manganese monoxide and chromic oxide. There exist a linear relationship between peak position of oxygen X-ray emission bands and interatomic distance of oxygen to adjacent atom, oxidation state and electronegativity of atom surrounded by oxygen. Although a slight difference was observed in some compounds, these results showed good agreement with those obtained electron bombardment excitation by D. W. Fischer.
The CrL_α emission spectra in metallic chromium is consists of main peak and high energy side satellite peak. Low energy side satellite peak was also observed in the oxide beside above-mentioned two peaks. The energy difference between main peak and low energy peak was about 5.5 eV for Cr₂O₃, but for CrO₃ and K₂Cr₂O₇ they were not distinguished clearly. The ratio of observed intensity of low energy peak and main peak was 1.5 for CrO₃ and 1.5 for K₂Cr₂O, both of which are larger value than 0.5 for CrO₃. Peak position of CrL_α shifted toward high energy side according to the increase of oxidation number and decrease of interatomic distance from chromium to adjacent atom.
The MnL_α emission spectra observed in several kinds of manganese oxide compounds were symmetrical bands and their peak position shifted systematically toward low energy side with increasing interatomic distance and decreasing valence electron.
These results suggest the possibility for the utilization to the structural research on the oxygen compounds existing most widely on the earth as well as the valence state analysis of heavy metallic compounds.

抄録全体を表示

単結晶MgOと単結晶Al₂O₃間の, 接触の状態を定量的に測定した固相反応を行ない, 反応層の配向とその組織が, 反応初期の接触状態により, どのように影響されるかを実験した. スピネル層はAl₂O₃に固着した形で生成し, 組織・配向の異なる2種の層から成るが, その一方のMgO側反応層は, 接触の良い時にはMgOに配向し, 接触の悪い時にはAl₂O₃に配向した. 接触の良い状態とは, 結晶間のギャヅプが約0.5μ以下のことであった. これによって, これまで研究者によって配向についての異なる結果が, 出ていたことが説明された. このように, 固相反応においては, 接触の良悪によって種々の現象が異なる可能性のあることがわかった.
さらに, 反応初期の異なった時点での反応層の組織を走査型電子顕微鏡によって観察し, スピネルの結晶成長の機構を推論した.

抄録全体を表示

Creep behavior of polycrystalline Ni-Zn ferrite with grain size of 1 to 20 μ was measured at the temperature range of 1000° to 1350°C. With increasing grain size of the ferrite, the mechanism of the creep changed from lattice diffusion controlled to grain boundary diffusion controlled. The critical grain size of the ferrite at which the mechanism changed was about 9 to 10μ. With raising the temperature, the same mechanism change as in the case of increased grain size was also observed. On the other hand, the stress index in the relation between strain rate and stress was a little higher than 1. The grains of the polycrystalline ferrite deformed at higher temperatures than 1300°C showed many clear slip bands resulting from the movement of the dislocations. The effect of the slip of grain boundary on the stress index was also discussed.

抄録全体を表示

The effect of addition of fluorine on crystallization of glass in the CaO-MgO-P₂O₅-SiO₂ system above temperatures at which separation of fluorapatite (FAp) crystals occurred was investigated. Glass samples containing 0.1, 0.5, 1.0 and 1.5 wt% fluorine as aimed contents were prepared by adding calcium fluoride to a base glass melt with the molar composition of 3.5CaO-3.5MgO-P₂O₅-3.5SiO₂. These samples have been examined by electron probe microanalysis (EPMA) and X-ray diffraction techniques after heat-treatment.
A computer was used for calculating compositions of the separated phases from X-ray intensities measured by EPMA. The Ca-rich phase precipitated as individually isolated particles in the initial stage, and then grew to a connected phase gradually. With increasing fluorine content of the sample, the number of Ca-rich particles and their growth rate increased in the above-stated initial stage. In the glasses heat-treated at 750°C to 850°C for 1h, the difference in content of the various component between the Ca-rich phase and the matrix phase was large for Ca²⁺ and Mg²⁺, whereas small SiO_X^n- and, particularly. PO₄^3-. A linear relationship between the amount of the Ca-rich phase and the amount of FAp was recognized above 775°C, while the above relation disappeared below 750°C. It was considered that the Ca-rich phase was formed by metastable phase separation of the glass.
The silicate crystals in the fluorine-containing glasses heat-treated above 800°C were forsterite and diopside. The amount of diopside relative to the amount of forsterite plus diopside increased with increasing the fluorine content. The molar ratios of MgO/SiO₂ and CaO/P₂O₅ in the Ca-rich phase in the glass heat-treated at about 800°C were less and larger, respectively, than those in the starting glass. It was deduced that the deposition of diopside in the fluorine-containing glass occurred in the Ca-rich phase.

抄録全体を表示