A METHOD OF THE PREPARATION OF FIBRILLAR AND LAMELLAR POROUS MICROSTRUCTURES AND NANOSTRUCTURES BY MEANS OF CONTROLLED VACUUM FREEZE-DRYING OF LIQUID NANOPARTICLES DISPERSIONS

摘要

The invention relates to a method of preparation of fibrillar and lamellar porous microstructures and nanostructures of various density based on controlled vacuum freeze-drying of a liquid dispersion of nanoparticles. According to the required density and structure of a final product, the particle concentration in the dispersion is adjusted from very low values for formation of fine, predominantly fibrillar structures, to very high values for formation of highly porous materials with high values of surface area in unit volume. The liquid dispersion of particles is rapidly freezed into solid state inside a tightly closed volume. In this form it is submitted to vacuum freeze-drying with required rate of sublimation of molecules of a liquid dispersion medium, until their total removal, accompanied by the creation of fibrillar and/or lamellar porous microstructures and nanostructures with density proportional to the initial concentration of particles in the dispersion and high value of surface area in unit volume. The orientation of the normal vector of the dominant surface of sublimation interface can be set with regard to the required properties of the final sublimate structure from vertically upwards to vertically downwards. The sublimation rate is adjusted by combination of vacuum depth and external heating of the sublimation interface of the frozen material.