Formation and growth of bubbles were treated as a “phase transition” phenomenon, in which the nuclei of gas bubbles were formed in a supersaturated solutiond and then were grown through gas diffusion.
The theoretical equations giving the rate of nucleation and of the growth of bubbles were derived in the forms
J=K exp[-1/kT{U₁+16πσ³/3(1-lnc/c₀/plnc/c₀)²}],
representing the rate of nucleation, and
I=K′exp{-1/kT(U₁′+πσ′²/δ 1-2lnc/c₀/plnc/c₀)},
representing the rate of the growsh of bubbles. In the equation U₁ and U₁′ are the activation energies of gas diffusion, σ, σ′ the interfacial energies between solution and bubble, where dashes refer to two-dimensional growth, c, c₀ are respectively, the concentrations of dissolved gas in the liquid and p is the external atomospheric pressure and δ the thickness of gas film. The rate of the growth of bubbles in the supersaturated solution dissolving CO₂ in water and in glycerin was measured with results showing the good applicability of the second equation.
The average diameter of bubbles in molten BK 7 glass increased at the initial stage of melting, which decresed again after passing through a maximum showing the existence of the growth of bubbles in glass melting processes. The rate of decrease of bubbles in the melt from the batch containing the component liberating gases is faster than in the case of cullet melting.
Agitation, which increases the rate of diffusion also accelerated the rate of growth of bubbles.
All these facts prove the soundness of the postulated theoretical equations.

抄録全体を表示

In order to make clear the influence of sodium oxide upon the formation and crystal structure of tricalcium silicate solid solution produced in the system CaO-SiO₂-Al₂O₃-Fe₂O₃, tricalcium silicate solid solution was prepared by heating the mixture of guaranteed reagents of calcium carbonate, silicic anhydride, sodium carbonate, and liquid, the composition of which is represented by the formula 6CaO⋅xAl₂O₃⋅yFe₂O₃ (x+y=3).
The process and the rate of formation of tricalcium silicate solid solution was discussed on the base of the results of free lime analysis and optical observation. The ordinary and high temperature X-ray diffraction, differential thermal analysis, infra-red absorption spectra and alkali analysis were employed for the determination of crystal structure. The results obtained are summarized as follows:
(1) Tricalcium silicate solid solution were formed approximately above 1300°C. The process of the formation was not the solid state reaction but it was proceeded by the diffusion of calcium ion and silicate ion through the liquid phase. The diposition of calcium and silicate ion occured the neighbour of dicalcium silicate solid solution accompanying with the formation of the zonal structure of tricalcium silicate solid solution.
(2) Rate of the formation of tricalcium silicate solid solution was accelerated with the increase of the quantities of liquid phase as well as the rising of the burning temperature which was retarded by the addition of sodium carbonate. No tricalcium silicate solid solution was formed from the batch containing more than 2% Na₂O. Remarkable retardation of the rate of the formation of tricalcium silicate solid solution by the addition of sodium carbonate was recognized in case of low burning temperature.
(3) The rate of formation of dicalcium silicate solid solution was accelerated by the sodium oxide, and initially formed β-2CaO⋅SiO₂ at 1300°C changed to α-modification with prolonged burning time.
(4) Solubility limit of ferric oxide in tricalcium silicate lattice is considered to be about 2% without giving remarkable change in crystal structure, and it changed to monoclinic form by the dissolution of sodium oxide.
(5) The crystal structure of tricalcium silicate solid solution with aluminum oxide and ferric oxide retained the triclinic form until 0.25-0.3% of sodium oxide dissolved into tricalcium silicate lattice.
(6) The change of X-ray diffraction pattern by the dissolution of minour constituents was discussed in the system 3CaO⋅SiO₂-Na₂O, 3CaO⋅SiO₂-Al₂O₃-Na₂O, CaO-SiO₂-Fe₂O₃-Na₂O and CaO-SiO₂-Al₂O₃-Fe₂O₃-Na₂O.

抄録全体を表示

In spite of the great importance for the maintenance of the aluminous cement buildings there have been only a few papers concerning the changes of the mechanical properties extending long times.
This paper deals with the possibilities of finding out the method of prediction of the mechanical strength of aged mortar as early as possible.
The results of the studies on the changes of the structure of hydrated aluminous cement during aging showed that the decomposition of aluminum hydrate, which took an important part in the mechanical strength, was accelerated remarkably by the cycle of wetting and drying as well as by exposing to sunlight.
It was considered that the change of the strength of hydrated aluminous cement during long age may be found rather in a short period by an accelerated test using weather-meter, a well known apparatus for testing the aging effect of organic products.
A good many specimens of aluminous cement mortars were subjected to weather-meter test, under 40% relative humidity at 35°C. During the test extending about 100 days they were exposed alternatively to the attacks of arc light and water spray (8min/hr, 1 atm nozzle).
Every 5 days the crushing strength were measured to compare with those of naturally aged mortar.
It was confirmed that the curve of weather-meter test was quite similar in form to that of natural aging, giving, however, in the first 30 days the change as large as that occurred in 3 years of natural aging.; both curves showed no change of strength therafter. The statistical consideration of the experimental data indicated that 10 days of the artificial weathring corresponded to a year in natural aging. Thus, the change of the mechanical strength of hydrated aluminous cement may be predicted by using weather-meter test which gives the values of natural aging test 30 times or more earlier.

抄録全体を表示