Journal of Applied Research of Chemical -Polymer Engineering

Abstract In graded structure aerogels, change of pores diameter through the thickness affects the effective thermal conductivity. As the pores diameter is reversely correlated to the density, the effective thermal conductivity of aerogel is often normalized to the density and it is expressed as the B parameter. Lower values of B would be the optimum conditions for the resulting aerogel. The objective of this work is to simulate the heat transfer of the homogenous structures and to compare it with structures that pore diameter vary through the thickness. For this purpose, the structure characteristics and properties of silica aerogel along with the effect of coupling thermal conductivity have to be taken into consideration. Using the COMSOLMultiphysics®software, the heat transfer was modeled for a number of cases, including homogenous structures with minimum density (L), maximum density (H) and for an optimum structure (OPT) having a minimum value of the B parameter. The results were compared to thestructurally graded aerogels in which the density was varied in two fashions, from higher values to lower (HtL) and from lower to higher values (LtH). The change of temperature with time was tracked for all the cases. Results indicated that the minimum value of heat transfer was obtained for the structurally graded aerogel of the type of LtH (a 2-percent increase of efficiency for LtH when compared to the optimum structure (OPT)). Therefore, this structure introduce as the best candidate for producing a thermal insulator.

Abstract Recently, flexible and environmental-friendly aerogel blankets have attracted considerable attention. In this work, the novel silica aerogel/basalt blanket was prepared using basalt fibers via a two-step sol-gel process followed by an ambient drying method and immersing the basalt fiber layer into silica sol. The silica aerogel particles were characterized by FTIR, FE-SEM and nitrogen adsorption analysis. The morphology, hydrophobic properties and surface roughness of neat basalt fiber and its aerogel blanket were also investigated. The density if 0.34 g/cm³, the porosity of 85%, mean pore size of 7±1.5 nm and the surface area of 750 m²/g for the nanostructured silica aerogel particles are obtained. The formation of nanostructured silica aerogel particles on the surface of basalt fibers in the sol-gel process were efficiently occurred leading to a strong hydrophobicity the blanket samples (contact angle of 114°) compared to the hydrophilic neat basalt fibers. The surface roughness of basalt fiber in the blanket samples was increased due to the fiber surface coating with silica aerogel particles. Increasing the sol volume in the synthesis process increased the basalt surface roughness from 3.6μ to 11μ.