Step-by-Step Modeling and Experimental Study on the Sol–Gel Porous Structure of Percolation Nanoclusters

Abstract

Non-conventional crystallization techniques have been developed in recent years. Non-conventional crystallization techniques use primary structural elements (for example, clusters) rather than atoms and molecules. Modern nanomaterial science is going through great changes as an entirely new approach of non-conventional growth mechanisms is emerging due to cluster coupling, catalyzing interest in cluster physics. The formation of fractal and percolation clusters has increased. We carried out step-by-step modeling and an experimental study of the formation of fractal and percolation clusters based on tin dioxide and silicon dioxide and formed by sol–gel technology. In this paper, the growth of fractal aggregates (clusters) from sol particles SnO2 and SiO2 based on the modified models of diffusion-limited and cluster–cluster aggregation is discussed. A percolation model using simulated fractal clusters of SnO2 and SiO2 particles is proposed. Experimental data on the sol–gel percolation structure of porous nanocomposites are presented. The modeling of SnO2 and SiO2 particles, which also consist of clusters (the next step in the hierarchy), is shown. We propose a generalized hierarchical three-dimensional percolation cluster model that allows calculating the surface area, knowing the experimental sizes of macropores and taking into account the micro- and mesopores (sizes less than a few nanometers).

SnO2-Based Porous Nanomaterials: Sol-Gel Formation and Gas-Sensing Application

“…The analysis of gas sensitivity measurements based on PPD and X-ray phase analysis data allowed us to find the optimal temperature for annealing nanocomposites of a three-component system, SiO 2 –SnO 2 –In 2 O 3 (700 °C). Based on complex studies of AFM, the BET technique and on previous research [ 47 , 48 ], a hierarchical model of the formation of two-component and three-component porous nanocomposites was proposed, presented in Figure 20 and Figure 21 (in the inset, the semiconductor and dielectric grains of nanocomposites are indicated in pink and blue), accordingly. According to the AFM data, it was found that two-component porous nanocomposites, SiO 2 –SnO 2 , were macro–meso–microporous (macropore sizes of 170–180 nm and mesopore sizes of 40–50 nm) and three-component porous nanocomposites, SiO 2 –SnO 2 –In 2 O 3 , were meso–microporous (mesopore sizes of 11–15 nm).…”

“…In refs. [ 47 , 48 ], it is shown that the analytical capabilities of atomic force microscopy do not allow for the diagnosis of elements with sizes smaller than the locality of the method; therefore, the micropore system (less than 2 nm in size) cannot be detected. At the same time, the contribution of such pores to the total surface area can be determined by using the BET technique.…”

“…It was found that the surface area of the porous nanocomposites calculated by processing atomic force images differed by 2–3 orders of magnitude from the surface area calculated according to the BET data. This indicated the existence of a micropore system of less than 10 nm, which was not diagnosed using AFM [ 47 , 48 ].…”