Influence of thermal annealing on structural properties of silica aerogel super insulation material

Abstract

Nowadays, aerogel materials are some of the lightest thermal insulation materials available on the construction market; they are produced by the mixing of polymers with solvents since they create a gel. Insulated fibrous-enhanced forms are the most frequently used ones. The type, which is used for thermal insulation, is usually produced by mixing the glass fiber net with the liquid-solid solution. The present paper talks about the structural modifications caused by heat treatment of the aerogel-reinforced with fiberglass. The aerogel probes were subjected to thermal annealing, and once they got isothermal heat treatments for weeks at 70 °C, moreover, untreated samples were subjected to stepwise thermal treatments between 100 and 250 °C for 1 day. Both the heat treatments were executed in dryer equipment under atmospheric air. Changes both in the structure and in chemical bonds of the untreated and annealed samples were followed. Raman spectra have been obtained for the samples. The structural changes have an influence on the studied material as well as in thermal properties. The structural and thermal properties were put under investigation after executing heat treatments on them. Jumps in the thermal conductivity could be connected with some structural changes. Due to the annealing intensity of the peaks connected with Si-O, crystalline SiO is increased, while CH, CH2, CH3,-OH and others are decreased.

Thermal Diffusion in Fibrous Aerogel Blankets

“…It was also stated in Ref. [28] Thermal conductivities can be found in the function of thermal diffusivities (Figure 1) calculated from the above-mentioned equations, as suggested by Salazar [24]. Salazar [24] highlights the necessity to plot thermal conductivity as a function of density.…”

“…Furthermore, it has to be mentioned that after these isochronal investigations, where the temperature was set at 100, 130, 150, 180, and 210 • C, significant changes were found both in the thermal conductivity and in the density of the material (see Table 2). The change both in the density and in the thermal conductivity can be identified as the dehydration process of the samples and the crystallization process [28]. It was also stated in Ref.…”

“…Material test results were presented in order to see the causes of the changes in thermal annealing. Moreover, in our previous study [28], both physical (structural) and chemical investigations were executed on the samples (Table 3).…”

“…From the material tests, one can conclude that the samples after thermal annealing go through crystallization processes on one hand and grain separation on the other hand. Lakatos and Csarnovics [28] presented that the number and intensity of the OH roots are decreasing. This means dehydration.…”

“…Material test results were presented in order to see the causes of the changes in thermal annealing. Moreover, in our previous study [28], both physical (structural) and chemical investigations were executed on the samples (Table 3). From the material tests, one can conclude that the samples after thermal annealing go through crystallization processes on one hand and grain separation on the other hand.…”