New technology for rapid processing and moulding of silica aerogel materials in prescribed shapes and sizes and their characterization

Mechanisms of Silicon Alkoxide Hydrolysis–Oligomerization Reactions: A DFT Investigation

“…[1][2][3][4][5][6][7] Because of these remarkable properties, experimental and theoretical investigations involving aerogels are mostly focused on silicon compounds. [1][2][3][4][5][6][7] Because of these remarkable properties, experimental and theoretical investigations involving aerogels are mostly focused on silicon compounds.…”

“…[8] Silica aerogels are ideal candidates for various applications, such as thermal superinsulators, adsorbents, sensors, catalyst carriers, and inorganic fillers. [12][13][14][15][16][17] The hydrolysis and condensation of the precursor silicon alkoxide, Si(OR) 4 , is the initial step to prepare silica aquasols. [12][13][14][15][16][17] The hydrolysis and condensation of the precursor silicon alkoxide, Si(OR) 4 , is the initial step to prepare silica aquasols.…”

“…[3,[9][10][11] The fabrication, morphologies, and applications of silica aerogels have received sustained attention in recent years in both chemistry and physics. d + % 0.32 ppm in Si(OEt) 4 ], so the hydrolysis and condensation reactions of Si alkoxides may be very slow and therefore need to be catalyzed, either with bases that carry strong negative charges (e.g. The Si atoms in Si(OR) 4 carry a reduced partial positive charge [e.g.…”

“…[19] Brochier Salon and Belgacem carried out 29 Si NMR spectroscopy studies on the competition between hydrolysis and condensation reactions of trialkoxysilanes in water/ethanol solutions and selected acidic conditions to enhance the formation of hydrolyzed alkoxysilane molecules and to slow down the consecutive self-condensation reactions. Recently, an off-lattice kinetic Monte Carlo (kMC) approach called continuum kMC was used to model silicate oligomerization from Si(OH) 4 in water and the evolution of silicate oligomers as well as their role in the oligomerization process were reported. [21][22][23][24][25][26][27][28][29][30][31][32] With regard to theoretical studies on the hydrolysis and oligomerization of silica, in 2005 Mora-Fonz et al [33] investigated the oligomerization and cyclization processes in the nucleation of microporous orthosilicic acid, Si(OH) 4 , by using DMOL3 with a numeric DNP basis set; in 2006 Trinh et al [34] studied the anionic and neutral mechanisms of oligomerization reactions of silica by using DFT calculations for various structures of silicate oligomers with the continuum solvation (COSMO) method and the activation energies for di-and trimer formation were estimated.…”

Preparation and characterization of hydrophobic silica aerogel sphere products by co-precursor method

“…Due to their superior characteristics above, silica aerogels are potential application materials for scientific and technological, such as environment clean up and protection [6e8], internal confinement fusion (ICF) targets for thermonuclear fusion reactions [9], efficient catalysts and catalytic supports [10], efficient thermal insulator for solar energy systems, refrigerators, thermal flasks, building, aeronautical and aerospace domains [11e15], and others [16,17]. Therefore, molding problem of silica aerogels as a filling material is extremely important requirements for different aspects of the applications.…”