Hybrid RF-Si Xerogels: A Cost-Effective Proposal for Insulator Materials

Abstract

Hybrid xerogels RF/Si were synthesized by controlling the chemical variables involved in the polymerization process (i.e., molar ratios, dilution ratio, catalysts, etc.) and evaluated as insulator materials. Higher insulating performances were recorded for these hybrids compared with their counterparts made from only one of their components (i.e., RF or Si xerogels with similar porous characteristics). The analysis of chemical and structural features correlated with heat transfer methods was useful in understanding the sum of contributions involved in the thermal conductivity of RF/Si xerogels. Variables such as roughness and tortuosity can be used to improve the performance of xerogels from a different perspective. In this way, thermal conductivities of 25 mW/mK were achieved without lengthy process steps or special drying methods. Knowledge of material design and the use of microwave heating during the synthesis allowed us to approach a simple and cost-effective process. These results suggest that the hybrid materials developed in this work are a good starting point for the future of the massive production of insulation materials.

Novel Silica Hybrid Xerogels Prepared by Co-Condensation of TEOS and ClPhTEOS: A Chemical and Morphological Study

“…The key behind the tunability of the properties of these materials is the synergetic effect that generates the coexistence, at a nanometric scale, of an inorganic skeleton with flexible and functional organic constituents [ 20 , 21 ]. The hybrid gels are prepared by the sol-gel method, a very versatile synthetic technique that allows different approaches: (i) Anchoring of organic molecules in the porous of the already-formed solid gel [ 1 , 2 , 7 , 8 , 9 ], (ii) grafting of organic moieties on the surface of a silica material [ 4 , 22 , 23 ], (iii) co-condensation of an organosilane (SiR x (OR’) 4−x ), with a carbon precursor, to form Si-O-C xerogels [ 16 , 18 , 24 , 25 ], or finally, (iv) classic co-condensation of a tetraalkoxysilane (Si(OR) 4 ), usually tetraethoxysilane (TEOS), with one or more organosilanes [ 8 , 9 , 10 ]. In the latter approach, to obtain materials with the desired properties, it is of paramount importance to control the precursors’ hydrolysis and condensation reactions ( Figure 1 ), due to their susceptibility to the media conditions (pH, solvents, use or not of a catalyst, proportions of H 2 O/precursor or organosilane/tetra alkoxysilane) [ 26 , 27 , 28 , 29 , 30 ].…”

Novel and High Electrocatalytic Activity Aerogel Pd-Tm (Tm=Co, Ni, Fe)

“…As a consequence, synthesis time is considerably reduced. Hence has been previously used for sol-gel synthesis of carbon [32,33] and silica gels [34,35]. Moreover, Martínez-L azaro et al used microwave heating to produce Pd aerogels with high yield by using a rapid and controlled synthesis process [29].…”