Abstract. A data processing method is presented making it possible to determine thin film thickness from GDOS depth profiles. It consists of fitting a piece-wise linear function to the depth profile and in using positions (abscissae) of their knots as parameters which are proportional to film thickness. For thickness calibration, such a linear combination of these parameters is used, which gives minimum variation coefficient of the residuals between the real and the estimated thickness of calibration samples. Relative error lower than 3% was obtained in calibration using 4 samples with nickel film thickness ranging from 0.1 to 8.3 ~tm, each analyzed four times.
Differences in porous structure of the dried aluminium hydroxide (containing sulphate ions) caused by changes in temperature and pH of precipitation, the time of aging and by additions of surfactants are documented and discussed. The aluminium hydroxide precipitated at low temperatures (30 – 50°C) and pH values (7 – 8) has bi-disperse porous structure with maxima in the region of large and medium pores. The increase of temperature and pH of precipitation limits or completely suppresses medium pores and increases large and small pores. Characteristic trend was the disappearance of medium pores which led to monodispersity in the region of large and small pores. The addition of surfactants suppressed the effect of short-time aging on pore size distributions. At moderate temperatures the effect of surfactants manifested itself in the broad pore size distributions and in the increase of the volume of large and medium pores. Qualitative and quantitative differences in porous structure caused by the action of surfactants were suppressed on increasing temperature and pH of precipitation.
The analysis of variance (ANOVA) was used to test the effect of changes of temperature and pH of precipitation, the time of aging and the addition of surfactants on the porous structure of dried aluminium hydroxide (containing sulphate ions). Changes in precipitation temperature effect the structure of samples, the most pronounced effect being observed in the region of large and small pores. The less distinct effect is exerted by pH of precipitation which affects especially small pores. The time of aging up to 48 h has little effect; it affects the volume of large and medium pores. The addition of surfactants during precipitation and washing leads to the increase of large and medium pores volume. Surfactants eliminate relatively efficiently the effect of aging time. Cationic and nonionic surfactants act similarly, but with different intensity, affecting the porous structure of aluminium hydroxide.
New data on critical holdups of dispersed phase were measured at which the phase inversion took place. The systems studied differed in the ratio of phase viscosities and interfacial tension. A weak dependence was found of critical holdups on the impeller revolutions and on the material contactor; on the contrary, a considerable effect of viscosity was found out as far as the viscosity of continuous phase exceeded that of dispersed phase.
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