Plasma phase composition

Argon was used as the central plasma gas and as the sheath gas, as well. Reagent (H2) or auxiliary (O2) gases were mixed to the sheath gas. Powders were injected axially into the hottest region of the plasma by a PRAXAIR powder feeder through a water cooled probe. Both the raw materials and the products were characterized in terms of particle size, chemical and phase compositions. In each run products were collected from the reactor wall (R), from the reactor bottom (RB) and the cyclone (C). 

Xia YQ, Jemal M (2009) Phospholipids in liquid chromatography/mass spectrometry bio-analysis comparison of three tandem mass spectrometric techniques for monitoring plasma phospholipids, the effect of mobile phase composition on phospholipids elution and the association of phospholipids with matrix effects. Rapid Commun Mass Spectrom 23 2125-2138... 

W.M., Influence of deposition temperature, gas pressure, gas phase composition, and RF frequency on composition and mechanical stress of plasma silicon nitride layer. J. Electrochem. Soc. 132 893 (1985). 

Most LC-ICP-MS hyphenation is performed by using isocratic elution. Gradient elution may be used to improve retention times and partition functions for a chromatographic separation with conventional LC detectors, but difficulties arise when gradients are introduced into the ICP. The changing load on the plasma due to the variations in mobile phase composition often causes plasma instability. In addition, optimal operating conditions evaluated for one mobile phase combination may not be valid when an organic constituent concentration is increased. 

The decrease of Si due to F-containing contaminants and the role of the oxygen plasma treatment can be explained by the principle of CAP. The key factor to explain the change of elementary composition at the interface is the plasma sensitivity of elements involved on the surface and in the plasma phase. The ablation of materials exposed to plasmas appears to follow the plasma sensitivity series of the elements involved, which is in the order of the electronegativity of the elements, i.e., elements with higher electronegativity in the condensed phase are more prone to ablate in plasma that contains elements with lower electronegativity [5]. 

The effectiveness of various protein precipitation additives in terms of protein removal and matric effects was investigated [86]. Acetorritrile, trichloroacetic acid (TCA), and zinc sulfate were formd most effective in removing proteirrs (applied in a 2 1 additive-to-plasma ratio). By a post-colunm infusion setup (Figme 11.6), these three methods were further evaluated with respect to matrix effect for five different mobile-phase compositions. As both buffered, acidified, and pure methanol-water mobile phases were compared, actual conclusions are difficult. In the pure methanol-water mobile phases, the use of TCA enhances the response, probably by generating acidic conditions more favourable in ESI-MS. With buffered or acidified mobile phases, the difference in matrix effects between acetonitrile or TCA as protein precipitation additive was less pronounced. A similar comparison between acetonitrile, perchloric acid, and TCA as protein precipitation additives was reported by others [100]. With acid precipitation, lower analyte recoveiy and higher %RSD was observed. Therefore, precipitation by acetonitrile was preferred. 

At 450°C, the reactions take place simultaneously, but reaction (b) is favored in a limited oxygen supply. Reaction (a) can be used exclusively in a plasma at 200-300 C and 0.15-0.3 torr with a gas phase composition of 10 parts silane in 1 part oxygen with a carrier gas of argon or helium. Carbon dioxide can also be used as the oxygen source, where the reaction is ... 

Phase compositions of plasma sprayed Zr02 component... 

A second method is a slight variation of the first. The raw powders are taken to a temperature of 950°C for 2 to 6 h in the same quick-firing kiln mentioned above, cooled and reground, and the procedure repeated for a total of three calcinations. The powders are then checked for phase composition by x-ray diffraction (XRD). Chemical analysis was performed using inductively coupled plasma-atomic absorption analysis and has confirmed that the composition of these powders is correct to within the accuracy of the device. 

A notable exception is a study by Hesse et al. (2008) who investigated the effect of powder grain size and grain size distribution on the spatial distribution of calcium phosphate phases in atmospheric plasma-sprayed hydroxyapatite coatings incubated in r-SBF (SBF-H, Table 7.8). Coatings were mechanically abraded under dry conditions in steps of 40 pm by abrasive SiC paper, and the newly created surfaces analysed by XRD with Rietveld refinement for their quantitative phase composition. The results of this depth profiling are shown in Figure 6.8. 

Figure 6.8 Spatial variation of the phase composition and the crystallinity of APS-HAp coatings incubated for 8 weeks in r-SBF (SBF-H, Table 7.8) as a function of the grain size of the precursor hydroxyapatite powder, (a) Coarse captal 90 powder (Plasma Coating...

Heimann, R.B., Tran, H.V., and Hartmann, P. (2003) Laser-Raman and Nuclear Magnetic Resonance (NMR) studies on plasma-sprayed hydroxylapatite coatings influence of bioinert bond coats on phase composition and resorption kinetics in simulated body fluid. Materialwiss. Werkstofftech., 34 (12), 1163-1169. 

The effect of residual stress on the dissolution of hydroxyapatite coatings was investigated on plasma-sprayed coatings of 80, 110 and 200 pm thickness (Han, Xu and Lu, 2001). Residual stresses in the coatings were measured with a holedrilling method. Dissolution of the coatings was monitored along with an examination of the phase composition. The results showed that both tensile residual... 

The composition of the reagent gas plasma is controlled by the mobile phase composition. It contains reactant ions of the type HsO, CH30H2, CHsCNH, etc., in most cases solvated by solvent molecules, for example, CH30H2 (H20)n(CH30H)ni with n + m < 4. The presence of ammonia vapor, for example, as a result of the evaporation of ammonium acetate added to the mobile phase, causes rapid removal of protonated solvent ions with formation of ammonium ions that become the dominant reagent gas ions. The addition of alkylamines or acids to the mobile phase results in the formation of protonated amines or anions as the dominant species in the reagent gas plasma. Since highly reactive ions, such as CHs" ", can not be formed by APCI in the presence of solvents, it is not possible to ionize saturated hydrocarbons or other compounds of low gas-phase basicity. 

In addition small-scale exposures at 870"C were used to study further the role of water vapour with 20 vol.-% and 30 vol.-% water vapour in air in an alumina tube furnace. Phase morphology was studied with scanning electron microscope (SEM). To distinguish between the glassy and crystalline phases some samples were etched in 2-% HF-solution. Phase composition was determined by a quantitative X-ray diffraction (XRD) analysis based on the internal standard, Cap2, method. The chemical composition of the amorphous phase in the binder was determined locally with EDS analysis in SEM. A bulk chemical analysis of the amorphous phases in binder was performed by Induction Coupled Plasma Mass-Spectrometry (ICP-MS). The samples were crushed powders of as-received and 500 h at water vapour bulk exposed (w) materials. The glassy phase was dissolved in HF-HNO3 solution. Open porosity, apparent and bulk densities of each specimen were determined by Archimedes method before and after the tests. 

The aim of this work is investigation of the structure, elemental and phase composition of nanostructured films formed on the carbon steel surface by compression of nitrogen plasma flows containing tungsten. 

Metal-carbon nanocomposite films possessing specific physical properties are recognized to be of current interest for different applications in electronics, mechanics [1-2]. The key property of nanocomposite films is the structure and size of metal particles and carbon matrix [3]. Therefore, the aim of this paper is to study the correlation between the phase composition, structure and tribological properties of Ni/a-C H nanocomposite films formed by microwave plasma-assisted deposition technique as a function of the C2H2 concentration in Ar+C2H2 gas mixtures varying from 0 to 100 %. 

The method of microwave plasma-assisted deposition allows to form nickel/hydrogenated amorphous carbon (Ni/a-C H) nanocomposite films. As the C2H2 concentration in Ar-C2H2 gas mixtures increased from 0 to 100 % the phase composition and precipitates size of Ni/a-C H films varies in the consequence Ni (15 nm)—>Ni + Ni3C (5-17 nm) Ni3C (17 nm)—> Ni + a-C H (1 nm) nc-G H (4 nm). The lowest friction coefficient and wear rate were obtained for Ni/a-C H amorphous nanocomposite films containing 20 % of sp3 bonds and deposited from the gas mixture with a C2H2 concentration of 60 %. 

Figure 6 pvra the mole fractions at equilibrium for the system 1 C, 4 H, 3 O, 2 Fe. This mixture (CH + FejOj) has been studied to provide data on the equilibrium vapour phase composition in a plasma furnace used for the reduction of iron oxide. A priori this diagram shows that the reduction of iron oxide to iron attains 1(K)% in the vapour phase. As we have shown previously for the nitrides the problem of condensation remains tmresolved, however, experimental results indicate that the cooling rate has little effect on the overall yield in that particular case. Figure 7 shows the reducing powers of hydrogen and carbon. 

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