Silica low-density

In a tour deforce of detective work, Di Renzo et al. uncovered an obscure United States patent filed in 1969 and issued in 1971 to Chiola et al., describing a low-density silica. Reproduction of that patent resulted in a product having all of the properties of MCM-41 [75]. 

In a previous study [5], we showed that some materials, in particular the low density silica xerogels, exhibit a remarkable behavior when submitted to mercury porosimetry. At low pressure, the volume variation observed is entirely due to a crushing mechanism, generally irreversible with sometimes a weak elastic component. At high pressure, these xerogels are invaded by mercury which intrudes the pore network. The transition fi om the crushing mechanism to intrusion is sudden at a pressure Pi, characteristic of the material. This particular point can be easily located on the curve of cumulative volume versus logarithm of pressure by... 

Distarch phosphate Fuller s earth Mica Microcrystalline cellulose Ozokerite Petrolatum Polyethylene, low-density Silica Talc Titanium dioxide... 

The preparation of low-density silica materials by hydrolysis of tetraethylorthosih-cate in the presence of cationic surfactants, namely, hexadecyltrimethylammonium bromide, was patented by Chiola et al. in 1969 [129]. However, the structural properties of these materials were not assessed. Di Renzo et al. [130] reported in 1997 that the patented preparation indeed results in the formation of mesoporous sihcas of the MCM-41 type, which were later rediscovered by researchers from Mobil Research and Development Corporation. 

In order to run photocatalytic oxidative remediation of airborne VOC on titania, Cao et al. (21) made low-density silica-titania aerogels by first preparing a silica aerogel and then impregnating the monolithic silica by a solution containing the Ti precursor. Finally, the impregnated silica aerogels were one more time supercritically... 

Land VD, Harris TM, Teeters DC (2001) Processing of low-density silica gel by critical point drying or ambient pressure drying. J Non-Cryst Solids 283 11-17... 

Allie C, Tcherkassova N, Ferrauche F, Lambert S, Heinrich B, Pirard R, Pirard JP (2006), Multigram scale synthesis and characterization of low-density silica, xerogels. J Non-Cryst Solids 352 2763-2771 Duffours L, Woignier T, Phalippou J (1995) Plastic behavior of aerogels under isostatic pressure. J Non-Cryst Solids 186 321-327... 

Gurav, J L, Rao, A V, Bangi, U K H (2(X)9) Hydrophobic and low density silica aerogels dried at ambient pressure using TEOS precursor. J Alloys Compd 471(1-2) 296-302. 

Bonnet A (1988) Low density silica aerogels observed by high resolution electron microscopy. Europhysics left. 6(8) 731-737... 

Schiith F, Sing K S W, Weitkamp J (eds.) (2002) Handbook of Porous Solids (Band 1). Weinheim Bourret A (1988) Low-Density Silica Aerogels Observed by High-Resolution Electron-Microscopy. Europhysics Letters 6 731-737... 

Tillotson T M, Hrubesh L W (1992) Transparent ultra low-density silica aerogels prepared by a two-step sol-gel process. J Non-Cryst Solids 145 44-50... 

It may seem unexpected that whereas silica can increase the adhesion to surfaces, it also can reduce adhesion between similar surfaces. The well-known addition of small amounts of dry, low-density silica powders to prevent caking of granular material is considered in Chapter 5. Considered here are uses in which sols are applied to various materials to reduce adhesion. 

This has been discussed in detail because it appears to be a way to making wide-pored, low density silica that is an alternative to neutralization in hot solution, and can be carried out at higher silica concentration. 

Amino-functionalized low density silica xerogels seen by different characterization methods... 

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