摘要:
A process for the preparation of a silica aerogel that includes subjecting a mixture that includes an organosilicon compound and ethyl acetoacetate to hydrolysis and polycondensation in an acidic medium to obtain a transparent gel. The organic solvent is substituted by liquid carbon dioxide and the carbon dioxide is evacuated under supercritical conditions of the carbon dioxide to obtain an aerogel.
摘要:
The invention relates to a thermal energy storage material, comprising a substantially homogeneous mixture of at least one compound having, in a temperature range of between 0.degree. C. and 200.degree.0 C., a solid-solid phase transition having a variation in enthalpy at least equal to 50 J/g, with an organic binder selected from the group consisting of polyepoxyde resins and polyurethane resins, stable at the temperature of the phase transition.
摘要:
The method relates to the production of phospho-nitrogenous products soluble in neutral ammonium citrate and wherein free urea does not remain in significant amount in such products. Most of the free urea is involved in a ureic combination of calcium sulphate. Tricalcic phosphate is reacted with a reactant obtained by mixing sulfuric acid and urea. The process is particularly useful for the manufacture of fertilizers.