Silica plasma

Figure 18 shows the bound rubber content of samples filled with untreated silica, plasma-treated silicas, and silane-modified silica, as representative of the filler-polymer interactions. Samples SPTh and SPA show the highest bound rubber contents, and the ST the lowest value. The SPPy sample shows a bound rubber content slightly lower than that of SU. 

The Payne effects of S-SBR/EPDM blend filled with untreated silica, plasma-modified silicas, and silane-treated silica are shown in Fig. 22. 

Wear testing plasma sprayed chrome oxide-silica, plasma sprayed PS 212 or mid-temperature CVD Ti(C,N) rub shoes against a CVD CrN disk at 350 C, lubricated, produced very high friction coefficients (0.17-0.21). The high friction coefficients caused high CrN wear rates and for this reason, only one of these material pairs was tested for over 30 minutes before the wear track had completely worn through the 2 to 3 micron thick CrN coaLing. 

Subsequently, the opened resist mask obtained can be used to etch the underlying substrate. In the case of sihcon or silica, plasmas with fluorine (mainly CF4 and SFg gases), bromine (H Br) or chlorine (CI2, HCl) can be used. Usable aspect ratios are in general larger than 1, that is, the feature height exceeds the line width. To achieve this, imprinted resists have to exhibit the correct selectivity to the underlying material this means that the etch rate of the resist in the plasma has to be sufficiently small compared with the etch rate of the substrate. 

Analyses of alloys or ores for hafnium by plasma emission atomic absorption spectroscopy, optical emission spectroscopy (qv), mass spectrometry (qv), x-ray spectroscopy (see X-ray technology), and neutron activation are possible without prior separation of hafnium (19). Alternatively, the combined hafnium and zirconium content can be separated from the sample by fusing the sample with sodium hydroxide, separating silica if present, and precipitating with mandelic acid from a dilute hydrochloric acid solution (20). The precipitate is ignited to oxide which is analy2ed by x-ray or emission spectroscopy to determine the relative proportion of each oxide. 

Transparent Vitreous Silica. Clear, transparent, bubble-free vitreous sihca may be obtained by melting natural quart2 minerals, ie, fused quart2, by flame or plasma vapor deposition (synthetic fused siUcas), and by sol—gel processing. 

She et al. [128] used rolling contact to estimate the adhesion hysteresis at polymer/oxide interfaces. By plasma oxidation of the cylinders of crosslinked PDMS, silica-like surfaces were generated which could hydrogen bond to PDMS r olecules. In contrast to unmodified surfaces, the adhesion hysteresis was shown to be larger and proportional to the molecular weight of grafted polymer on the substrate. The observed hysteresis was interpreted in terms of the orientation and relaxation of polymer chains known as Lake-Thomas effect. 

Another illustrative example of the application of FTIR spectroscopy to problems of interest in adhesion science is provided by the work of Taylor and Boerio on plasma polymerized silica-like films as primers for structural adhesive bonding [15]. Mostly these films have been deposited in a microwave reactor using hexamethyldisiloxane (HMDSO) as monomer and oxygen as the carrier gas. Transmission FTIR spectra of HMDSO monomer were characterized by strong... 

Fig. 14. RAIR spectra of a plasma polymerized silica-like film deposited onto a polished aluminum substrate (A) before and (B) after annealing at ISO C for 30 min. Film thickness was about 735 A. Reprinted by permission of Gordon and Breach Science Publishers from Ref. [15].

Metyrapone human plasma/urine liq-liq extraction silica Chiralcel OJ UV 42... 

Pimobendan and its human plasma liq-liq extraction silica Chiralcel OD UV 48 ... 

Figure 11.4 Chromatograms of plasma samples on a silica-chiralcel OJ coupled column system (a) plasma spiked with oxprenolol (internal standard) (b) plasma spiked with 040 p-g/ml metyrapone and 0.39 p-g/ml metyrapol (racemate) (c) plasma sample obtained after oral administration of 750 mg metaiypone. Peaks are as follows 1, metyrapone 2, metyrapol enantiomers 3, oxprenolol. Reprinted from Journal of Chromatography, 665, J. A. Chiarotto and I. W. Wainer, Determination of metyrapone and the enantiomers of its chfral metabolite metyrapol in human plasma and urine using coupled achfral-chfral liquid cltro-matography, pp. 147-154, copyright 1995, with permission from Elsevier Science.

Z. Yu and D. Westerlund, Direct injection of large volumes of plasma in a columnswitching system for the analysis of local anaesthetics , II. Determination of bupivacaine in human plasma with an alkyl-diol silica precolumn , ]. Chromatogr. A 725 149-155 (1996). 

The inductively coupled plasma source (Fig. 20.11) comprises three concentric silica quartz tubes, each of which is open at the top. The argon stream that carries the sample, in the form of an aerosol, passes through the central tube. The excitation is provided by two or three turns of a metal induction tube through which flows a radio-frequency current (frequency 27 MHz). The second gas flow of argon of rate between 10 and 15 L min-1 maintains the plasma. It is this gas stream that is excited by the radio-frequency power. The plasma gas flows in a helical pattern which provides stability and helps to isolate thermally the outside quartz tube. 

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

Both reactions may take place simultaneously at a deposition temperature of 450°C and at atmospheric pressure. Reaction (1) can also take place in a plasma at 15-300 mTorr and in a temperature range of200-300°C with a silane-to-oxygen ratio of 10/1 in a flow of argon or helium. These two reactions are used to produce doped silica by adding a doping gas such as diborane (B2H ) or phosphine (PH3) to the stream. 

Inside" processes—such as modified chemical vapor deposition (MCVD) and plasma chemical vapor deposition (PCVD)—deposit doped silica on the interior surface of a fused silica tube. In MCVD, the oxidation of the halide reactants is initiated by a flame that heats the outside of the tube (Figure 4.8). In PCVD, the reaction is initiated by a microwave plasma. More than a hundred different layers with different refractive indexes (a function of glass composition) may be deposited by either process before the tube is collapsed to form a glass rod. 

Increasing price of crude oil has built up pressure on tire and automobile industry to develop low rolling-resistant tire with better traction. Combination of carbon and silica with coupling agent (dual filler technology) shows low RR with better traction and skid resistance in tire tread compound. Carbon black developed by plasma process and nanostructure black are other new significant developments in filler technology. 

Another example of the use of small particle silica is in the analysis of theophylline in plasma, as shown in Figure 5 (40). The clean-up procedure is simply a single extraction of the plasma with an organic solvent. This analysis has also been achieved by reverse phase chromatography (41), and this points out the fact that in some separations (e.g. with components of moderate polarity) either the adsorption or reverse phase mode can be used. 

Figure 5. Chromatograms for theophylline in plasma extracts. Arrow indicates tneophyUine peak. Conditions 50 cm X 3 mm (i.d.) column with 10 fjm silica gel (Micropak Si 10 Varian) mobile phase, 84/15/1 chloroform/isopropanol/acetic acid flow rate, 40 rm/hr detector, UV,273nm(40).

Figure 6. Absorption spectra of spherical non-interacting nanoclusters embedded in no absorbing matrices (a) effect of the size for Ag nanoclusters in silica (b) effect of the matrix for R = 2.5 nm Au clusters (the refractive index n = and the position of the plasma resonance are reported for each considered matrix) (c) effect of the cluster composition for i = 5 nm noble-metal clusters (Ag, Au, Cu) in silica. (Reprinted from Ref [1], 2005, with permission from Italian Physical Society.)...

The new lipid occurred only in the plasma hpids of newborns and was not present in membrane hpids of red cell membranes or platelets. Total lipids were extracted from plasma and from red blood cell membranes and platelets. A total lipid profile was obtained by a three-directional PLC using silica gel plates and was developed consecutively in the following solvent mixtures (1) chloroform-methanol-concen-trated ammonium hydroxide (65 25 5, v/v), (2) chloroform-acetone-methanol-ace-tic acid-water (50 20 10 15 5, v/v), and (3) hexane-diethyl ether-acetic acid (80 20 1, v/v). Each spot was scraped off the plate a known amount of methyl heptadecanoate was added, followed by methylation and analysis by GC/MS. The accmate characterization of the new lipid was realized using NMR technique. 

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