Optimization and Analytical Modeling of Technological Modes of Production of Microsilica for Insulation Panels Type VIP

Abstract

Two methods of synthesis of fine-grained microsilica from diatomite rocks suitable for creation of vacuum heat-insulating panels with thermal conductivity of 0,002–0,02 Wt/m²k are considered. The main indicators determining the dependence of thermal conductivity on the physical and topological properties of silicon dioxide particles are determined by the method of analysis of deterministic models of heat transfer in granular systems. To assess and regulate the thermal conductivity of granular systems, to the main indicators we can include: m² – porosity of the microstructure; ρ_к – density of clusters forming the microstructure; εпр – characteristic of the degree (dissipation of radiation energy) of the blackness of the filler particles; d_i – pore diameter at the i-th scale level; λ_Т, λ_Г – thermal conductivity of the solid and gas phase of the system; α – accommodation coefficient; N – coordination number; D – fractal dimension characterizing the topological features of the structure of particles, aggregates, clusters.The experimental analysis of the properties of synthesized silica fume was carried out. As a result of the research, it was found that the optimal properties of dispersed silica, synthesized from opal-cristobalite biomorphic rocks (diatomite of the Atemar Deposit) by deposition of silicon oxide from colloidal solution, obtained in the implementation of the second method of production. In the process of synthesis, dispersed silica fume is obtained, represented by the mineral opal, constructed from polymerized strands of amorphous silica, which are folded into globules, ball clusters with a diameter in the range of 2–40 nm. The topology of the surface of globules is characterized by fractal dimension D = 2,32; 2,64, which reduces the values of the accommodation coefficient and, accordingly, thermal conductivity. Association of the globular clusters of the particles of a nanoscalelevel to form scale invariant pore structure provideslow thermal conductivity.