ИСТИНА

Synthesis and processing of 3D nanomaterials consisting of nanofibrils of Al2O3∙nH2O were studied in the temperature range of 20 – 1700 °C. We have shown that structure of these materials can be presented as a 3D network consisting of nanofibrils of aluminum oxyhydride/oxide (NOA). A remarkable property of the NOA material is the preservation of the monolithic state during annealing although the density of NOA monolith increases from ~ 0.02 up to ~ 3 g/cm3, the total porosity decreasing from 99.3% to 25% and remains open up to 4 hour annealing at 1300 °C. Two mechanisms of the morphological and structural transformations in NOA are evidenced and quatitative physical model was proposed allowing the estimations of all this changes as the morphological evolution of the averaged NOA fibril. Applying the 3D model allows to explain the phenomenon of the preservation of the integrity of NOA monoliths during annealing by an important role of surface diffusion which provides an isotropic decrease in the parameters of the 3D structure without a significant increase in internal stresses, and samples integrity are preserved. With the purpose of functionalization of NOA materials properties, various methods of the structural and chemical modification have been developed: by applying metallorganic compounds (siloxanes, phthalocyanines, oxyquinolinates) and by impregnation with nanoparticles <10 nm (TiO2, NiO2, CeOx, etc.) The simplest effective media models using Maxwell-Garnett, Bruggeman and Landau-Lifshitz-Looyenga equations was applied to describe the optical properties of the NOA materials in the THz range, and good agreement with the experimental results was achieved. This work was supported by the French-Russian collaboration project DRI CNRS No.EDC26176, and by the Russian Foundation for Basic Research Project 17-53-150007 CNRS_a.