Cab* O’Sil

Fia. 13. (a) Raman spectrum of a pretreated Cab-O-Sil disk recorded using a laser beam expander (b) infrared spectrum of a newly pressed Cab-O-Sil disk. From Hendra and Gilson, Laser Raman Spectroscopy, p. 186. Wiley, New York, 1970. 

Fig. 25. Interference of plasma lines from the Ar+ emiasion in the Raman spectrum of a Cab-O-Sil silica sample.

Loader 38) studied the Raman spectra of styrene adsorbed on different silicas—chromatographic grade silica gel, Cab-O-Sil, and Aerosil 380. The author utilized the fact that chemisorption will bring about marked changes in the spectrum whereas physical adsorption will cause only a broadening of the Raman lines accompanied in some cases by a frequency... 

Raman spectra, 296, 298, 303, 304 of adsorbed molecules, 333-339 of adsorption systems, 320-332 of Cab-O-Sil disk, 320 different from infrared spectra, 302-304 effect of fluorescence on, 321-327 molecular symmetry and, 304, 305 of oxides, 321... 

Ref 4 contains the following requirements and criteria for silica (1) finely divided similar to Cab-O-Sil , Grade M-5, made by the Cabot Corp of Boston, Mass, (2) surface area as ml of NaOH titrant used to achieve a pH of 9.0 175 to 225m2/g, (3) density as the wt of a known vol of silica 2.31bs/cu ft max, (4) moisture as loss in wt 1.5% max, (5) pH as the measurement made using a Beckman Model G pH Meter with glass vs calomel electrodes ... 

We have recently tested the Tx model described above by obtaining T, measurements in powder samples with known S/V. Samples used were constructed from fumed silica (CAB-O-SIL M-5 and TS-500, Cabot Corp.), and were either hydrophilic (M-5) or treated by the manufacturer to be hydrophobic (TS-500). Powder of each type was pressed into a polycarbonate cylinder, with a degree of compression controlling the pore space volume of each sample. These materials have a very high specific surface area (200 m2 g 1 for M-5, 212 m2 g-1 for TS-500), which is not expected to change significantly even at the maximum compaction pressure used. 

The catalyst used throughout this study was prepared by impregnation. To a slurry of silica (M5 Cab-O-Sil, Surface Area 200 m2g 1) in water sufficient copper nitrate solution was added to give a loading of 8.6 % w/w Cu. The resulting suspension was dried at 353 K until a free flowing powder was obtained. 

Recent experimental results are summarized in Table III. The catalyst used here was molybdenum supported on Cab-O-Sil. We have experienced difficulty in repeating the previous results, which indicated that up to 50% selectivity to methanol could be achieved even at conversions of -15% (18). In the more recent study it has been possible to obtain this selectivity only at conversions of 1%. Nevertheless, at sufficiently low conversions methanol is the principal product, provided steam is present in the system. 

Berg and Flood (B8) and Berg, Fernish, and Flood (B5, B6) made measurements on the charging of Carbowax 60009a and saccharin (with and without 1 % Cab-O-Sil additive), Cab-0-Sil,9a MgO, and NH4C1 when passed pneumatically through a 0.8-mm-diam stainless steel tube (see Section VI for... 

Figure 4.9. Stem-Volmer intensity quenching of (a) Ru(bpy)32+, (b) Ru(phen)32 and (c) Ru(Ph2phen)32+ on hydrophilic Cab-O-Sil silica disks. The solid lines are the best fits using a two-parameter Freundlich adsorption model. (Reprinted from Ref. 33 with permission. Copyright 1991, American Chemical Society.)...

Figure 10.9 shows the intensity versus [O2] quenching curve for three complexes in Cab-O-Sil disks. The solid lines are the best fits to a Freundlich adsorption model (see below). All quenching is dynamic with no static component. 

Surface Sol-Gel Modification of Fumed Silica with Ti02/Al20s orAfO / T1O2 Double Layer. The basic procedure for functionalization of Cab-O-Sil silica... 

Relaxation dispersion data for water on Cab-O-Sil, which is a monodis-perse silica fine particulate, are shown in Fig. 2 (45). The data are analyzed in terms of the model summarized schematically in Fig. 3. The y process characterizes the high frequency local motions of the liquid in the surface phase and defines the high field relaxation dispersion. There is little field dependence because the local motions are rapid. The p process defines the power-law region of the relaxation dispersion in this model and characterizes the molecular reorientations mediated by translational displacements on the length scale of the order of the monomer size, or the particle size. The a process represents averaging of molecular orientations by translational displacements on the order of the particle cluster size, which is limited to the long time or low frequency end by exchange with bulk or free water. This model has been discussed in a number of contexts and extended studies have been conducted (34,41,43). 

Fig. 2. Water proton spin-lattice relaxation dispersion in Cab-O-Sil M- samples with two different degrees of compression. The solid lines were computed using the model as in Ref. (45).

On the other hand, the alkoxide system presented several problems in formulation. The system first chosen as a model consisted of a trimethoxymethyl silane crosslinker, 8000 centistoke HEB siloxane, and a catalyst. A number of catalysts were used and each exhibited different cure rates and electrical properties. DuPont tetraalkoxytitante-Tyzor appears to he one of the better catalysts used in this type of curing system. Fillers are usually incorporated into the silicone formulation to improve mechanical properties, promote adhesion, and to serve as light screening and pigment agents. Cab-o-sil, a form of fumed silica, carbon-black, titanium dioxide and calcium carbonate are then used as RTV fillers. 

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