Methods for silicas

Fig. 3.20 Pore size distributions (calculated by the Roberts method) for silica powder compacted at (A) Ibtonin" (B) 64tonin (C) 130 ton in". The distributions in (a) were calculated from the desorption brunch of the isotherms of nitrogen, and in (h) from the adsorption branch.

Special Characterization Methods for Silica-Rubber Coupling.805... 

The investigation of silica materials has been a field of huge interest for a long time, because this is an inert and very stable material [68-76], In Chapter 2, the amorphous morphology of silica and, in Chapter 3, the method for silica synthesis were described. 

A dielectric oxide layer (eg. silica) is useful as a shell material because of the stability it lends to the core and its optical transparency. The classic method of Stober for solution deposition of silica are adaptable for coating of nanocrystals with silica shells.111 This method relies on the pH and the concentration of the solution to control the rate of deposition. The natural affinity of silica to oxidic layers has been exploited to obtain silica coating on a family of iron oxide nanoparticlcs including hematite and magnetite111 Such a deposition process is not readily extendable to grow shell layers on metals. The most successful method for silica encapsulation of metal nanoparlides is that due to Mulvaney and co-workers.114 In this method, the surface of the nanoparticles is functionalized with aminopropyltrimethylsilane. a bifunctional molecule with a pendant silane group which is available for condensation of silica. The next step involves the slow deposition of silica in water followed by the fast deposition of silica in ethanol. Fig. 13 shows the TEM images... 

Ung, T., Liz-Marzan, L. M. and Mulvaney, P. (1998). Controlled method for silica coating of silver colloids. Influence of coating on the rate of chemical reactions. Langmuir 14 3740-3748. 

L.A.Belyakova, A.V.Simurov, V.V.Sidorchuk and V.A.Tertykh, The Method for Silica Modification, SSSR Patent No. 1742208 (1992). 

Simultaneous development was undertaken of a method for silica coating steels and a test to demonstrate that the coke formation reaction was surface sensitive and reduced by the deposition of a silica film. 

Figure 8. Silica layer thickness versus silica loading determined by TEM and XPS (ESCA) methods for silica-coated a-alumina particles. The theoretical curve was calculated for uniform silica coating of dense spherical a-alumina particles with equivalent 150-nm diameters. (Reprinted with permission from reference 7. Copyright 1989.)...

Abrasive-polishing agent, use of silica gels and precipitated silicas, 625 Abrasive powder, preparation, 426, 427f Acetic acid, catalysis of silica sol-gel precursor hydrolysis, 406, 407t, 408/ Acid-neutralization manufacturing method for silica sol, procedure, 53, 54/... 

Several months are required to acid clean the scale from the evaporators thus leaving the evaporators unavailable to perform an important process fimction. To help predict the rate of scale formation, salt solutions that feed the evaporators are analyzed for silica. The molybdosilicate colorimetric method for silica was developed for remote determination by using fiber optics to couple the light source and photodiode array spectrophotometer outside the shielded cell to the flow cell inside the cell. This remote method has considerable advantages in terms of speed and minimizing radiation dose to personnel versus analyzing the high radiation samples outside the shielded cell. 

Concentration Range The linearity of the proposed SIA method for silica determination was studied imder optimum conditions described above. The correlation coefficient was 0.9999. The method is linear between 0.5 and 50 ppm. The detection limit was 0.5 ppm. The equation for absorbance measurement was A = 0.220 + 0.009x. 

Xia, X.P., Beland, R., Miersch, S. et al.. Development and validation method for silica determination by spectrophotometry in some herbs and pharmaceutical formulations. Analytical Letters... 

Supercritical drying (SCD) is the first and most commonly used method for silica aerogels ... 

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