Hydrophobic aerogels from Si(OMe)4/MeSi(OMe)3 mixtures

Schwertfeger, Fritz; Glaubitt, Walther; Schubert, Ulrich

doi:10.1016/s0022-3093(05)80435-1

Cited by 128 publications

(57 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For samples C to E, the IL ratio increases and the associated pH increase enhances polycondensation reactions (Pope & Mackenzie, 1986) and thus the gelling time decreases (Schwertfeger et al, 1992). It is worth noting that the shrinkage after drying is rather low (< 10%)for all the investigated samples except sample A.…”

Section: Discussionmentioning

confidence: 87%

“…The presence of MT MS (hydrophobic groups) in the sol postpones the hydrolysis and condensation reactions and thus increases the gelation time (Schwertfeger et al, 1992). For samples C to E, the IL ratio increases and the associated pH increase enhances polycondensation reactions (Pope & Mackenzie, 1986) and thus the gelling time decreases (Schwertfeger et al, 1992).…”

Section: Discussionmentioning

confidence: 99%

“…Capillary tensions induced by IL exchange are probably overcoming the strength of the silica network. For the other samples, the MT MS induces a repulsive wall/liquid effect (stable S i − CH 3 groups on the surface of S iO 2 particles) and thus reduces the capillary tensions (Schwertfeger et al, 1992). Consequently shrinkage decreases slightly as the increase of the MTMS content.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Textural, Structural and Electrical Characterizations of EMIMAc Silica Ionogels and Their Corresponding Aerogels

Bengourna¹,

Despetis²,

Bonnet³

et al. 2014

APR

View full text Add to dashboard Cite

Silica ionogels were synthesized from tetramethoxysilane (T MOS ),methyltrimethoxysilane (MT MS ) and 1-ethyl-2-methylimidazolium Acetate (EMI MAc: Ionic Liquid) in different proportions .The textural characterizations showed an effect of these concentrations on the corresponding aerogels: pore size distributions and effective surfaces. The structure of the aerogels was measured with a SAXS (Small-Angle XRay Scattering) apparatus and was typical of acid catalyzed aerogels. Conductivity voltage measurements, operated on the ionogels, were carried out using an electrical 4 wire-electrodes set up. The electrical voltage temporal response of the EMIMAc silica ionogel was modelled by a RLC series circuit which characteristics depended on the synthesis.

show abstract

Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Textural, Structural and Electrical Characterizations of EMIMAc Silica Ionogels and Their Corresponding Aerogels

Bengourna¹,

Despetis²,

Bonnet³

et al. 2014

APR

View full text Add to dashboard Cite

show abstract

“…To explain the influence of precursor material on the elastic moduli we have to adress the chemical differencesy of phenol and resorcinol first, Both monomers are trifunctional, but the phenol is much less reactsmk While the particle growth mechanism is totally different for the present organic system [8], the strong difference in monomer reactivity reminds of a silica system with TMOS (tetramethoxysilane) and MeTMOS (Methyl-Trimethoxysilane), where the latter monomer is reacting slower [9]. In that work is was found that due to the difference in reactivity the slower reacting monomer predominantly condensed onto the surface of primary particles that mainly consisted of TMOS.…”

Section: Discussionmentioning

confidence: 99%

Structural Evolution in Carbon Aerogels as a function of Precursor Material and Pyrolysis Temperature

1996

View full text Add to dashboard Cite

Several organic reactions that proceed through a sol-gel transition have been identified at LLNL. The most-studied reaction involves the aqueous polycondensation of resorcinol (1,3- dihydroxybenzene) with formaldehyde. Recently, we have shown that phenol can be added to this polymerization as a comonomer. The resultant crosslinked gels are supercritically dried from carbon dioxide (Tc=31°C, Pc = 7.4 MPa) to give resorcinol-phenol-formaldehyde (RPF) aerogels. Because RPF aerogels are composed of a highly crosslinked aromatic polymer, they can be pyrolyzed in an inert atmosphere to form vitreous carbon monoliths (CRPF). The resultant aerogels are black in color and no longer transparent, yet they retain the high porosity (40–98 %), ultrafine cell/pore size (< 50 nm), high surface area (600–800 m2/g), and interconnected particle (˜10 nm) morphology of their organic precursors. In this study, we examine the acoustic and mechanical properties of these materials as a function of precursor material and pyrolysis temperature. It is shown that the elastic moduli of RPF and CRPF is higher than that of pure RF / CRF aerogels at a given density. Upon pyrolysis RPF aerogels tend to shrink to a larger extent.

show abstract

“…21 Schubert et al successfully incorporated organic groups into the silica aerogel network by cocondensing Si(OR) 4 with RSi(OR) 3 . 22 Loy et al have formed novel aerormosil materials by inserting organic bridges into the silicate network, through the hydrolysis-condensation of trialkoxylsilyl-terminated organic molecules such as p-triethoxylsilylbenzne. 23 Due to higher functionality (i.e., 3 in triethoxysilyl vs. 1 in silanol), all of the organic functional groups were attached to the silica network by C-Si covalent bonds in both cases, which was proven by 29 Si solid-state NMR results.…”

mentioning

confidence: 99%