Effect of vacuum and of strong adsorbed water films on micropore formation in aluminum hydroxide xerogel powders

Aluminum hydroxide gels were washed with water, ethanol, methanol and isopropanol to obtain new gels with different liquid phases that were dried either in air at 120 \u25e6C or under vacuum at 80 \u25e6C. Drying in air leads to alcoholic xerogels with BET surface areas larger than the aqueous ones. The effect of the alcoholic groups as substitutes of the hydroxyl ones has been discussed to account for the final size of xerogel crystallites

Specific wetting enthalpies for investigating lime surface properties due to the high temperature reactivity of limestone impurities

In this paper, we address the role that limestone impurities play in the morphogenesis of different CaO-based particle surfaces. During the thermal decomposition of 00., such impurities can be the source of a complex pattern of reactions that form heterogeneous CaO-based surfaces. Our study reveals that this phenomenon is experimentally measurable once the level of impurities in the starting limestone is approximately 1.7% and the decomposition temperature is 1300\ub0C. In limestones with impurity levels of 1% or less, the reactivity between them and the host CaO/CaCO3 phases is reduced to a negligible level. To explore their average surface properties, we dispersed a set of heterogeneous lime powders in liquid paraffin and measured the correspondent exothermic wetting heat. Combining these results with Brunauer, Emmett and Teller (BET) measurements of the specific surface of the limes allows one to introduce a new parameter: the specific wetting enthalpy \u3be (J/m2). Limes with nearly identical specific surface areas of approximately 1 m2/g can differ greatly in their \u3be values, which range from -8\ub10.2 J/m2 to -1\ub10.2 J/m2. The specific wetting heats can be used as an intensive average thermodynamic parameter to characterise the chemical and physical properties of lime surfaces with specific surface energies that are experimentally undeterminable via calorimetric measurements

Silica-paraffin and kaolin-paraffin dispersions: Use of rheological and calorimetric methods to investigate the nature of their dispersed microstructure units

Enthalpy of wetting of silica\u2013paraffin dispersions is function of volume fraction \u3b8. \u25ba Microstructure of silica\u2013paraffin dispersion evolves according to branching mechanism. \u25ba Stability of a silica\u2013paraffin microstructure is greater than kaolin\u2013paraffin one. \u25ba Percolation thresholds determined by analysing \u3c40 versus \u3b8 and \u394H versus \u3b8 are fairly equal