Plasma-chemical oxidation

XPS will aid in understanding specifically the surface of the black deposit covering pictographs in Little Lost River Cave in Idaho. This work will complement other bulk analyses carried out with pyrolysis-GC-MS and thermally assisted hydrolysis /methylation (THM)-GC-MS (75). The objectives of this project were to use XPS to qualitatively determine the surface elemental composition of the black residue semiquantitatively characterize the surface, for comparison with other surface-related materials and examine the relationship between the chemistry and depth by using Ar+ sputtering. This, then, will aid in validating the radiocarbon date obtained through plasma-chemical oxidation and accelerator mass spectrometry by Steelman et al. (5). 

Gas-Phase Synthesis Related to Plasma-Chemical Oxidation of HCI and SO2... 

Interaction of Atoms, Molecules, and Other Chemically Active Heavy Particles Generated in Non-Thermal Plasma with Polymer Materials Plasma-Chemical Oxidation of Polymer Surfaces... 

An important topic of research is the introduction of the catalyst in the microreactor. In brief solid catalysts can be incorporated on the interior of micromachined reaction channels, prior to or after closure of the channel, by a variety of strategies anodic oxidation, plasma-chemical oxidation, flame combustion synthesis, sol-gel techniques, impregnation, wash coating, (electro-)plating, aerosols, brushing, chemical vapor deposition, physical vapor deposition and nanoparticle deposition or self-assembly. Some of these methods can be applied in combination with photolithography or shadow masking. 

Pollution control such as the reduction of nitrogen oxides, halocarbons and hydrocarbons from flue gases [37] is another important field of plasma-assisted chemistry using non-thennal plasmas. The efficiency of plasma chemical reactions can be enhanced by introducing catalysts into the plasma [38, 39]. 

In plasma chemical vapor deposition (PCVD), the starting materials are typically SiCl, O2, 2 6 GeCl (see Plasma technology). Plasma chemical vapor deposition is similar to MCVD in that the reactants are carried into a hoUow siUca tube, but PCVD uses a moving microwave cavity rather than a torch. The plasma formed inside the microwave cavity results in the deposition of a compact glass layer along the inner wall of the tube. The temperatures involved in PCVD are lower than those in MCVD, and no oxide soots are formed. Also, the PCVD method is not affected by the heat capacities or thermal conductivities of the deposits. 

The first experiments on the plasma chemical decomposition of fluoride solutions containing tantalum or niobium to obtain tantalum and niobium oxides were reported about fifteen years ago [524]. Subsequent publications were devoted to further development and expansion of the method for other refractory rare metals such as titanium and zirconium [525 - 532]. 

The plasma chemical decomposition method is based on rapid heating, decomposition and hydrolysis of fluoride compounds to obtain powdered oxides following interaction with water. Rakov and Teslenko [533] showed that the following hydrolysis equilibrium... 

Niobium oxide obtained by plasma chemical decomposition is an ultra-fine powder with a specific surface area, as determined by the BET method, of about 20-30 m2/g. The estimated average particle size does not exceed 0.1 pm. 

Investigations of the plasma chemical decomposition of tantalum-containing fluoride solutions indicated no significant differences in the process and product parameters compared to the corresponding decomposition of niobium-containing fluoride solution [529, 532]. The particle diameter, shape and specific surface area of both niobium oxide and tantalum oxide powders attest to a gas-phase mechanism of the interaction, with sequential condensation and agglomeration of the oxides. 

Mantyla, T., Vuoristo, P., and Kettunen, P., Chemical Vapor Deposition of Plasma Sprayed Oxide Coatings, Thin Solid Films, 118(4) 437-444(24Aug. 1984)... 

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. 

Partial oxidation is also mentioned as a process to convert ethanol to hydrogen.124 Another novel technology for ethanol to hydrogen has been described by Toci and Modica.125 It is based on cracking ethanol vapors by "cold-plasma-chemical processing" in the presence of a Ni-based catalyst. 

The removal of T from thick co-deposits (tens of pm) may require the removal of the co-deposits themselves by chemical and/or plasma-assisted oxidizing reactions in the presence of oxygen, or alternatively, via abra-sive/mechanical techniques, such as pellet blast cleaning. From the extensive laboratory measurements of H/D/T removal rates from co-deposited films during exposure to air or oxygen, three key conclusions can be drawn (i) D release occurs in conjunction with C erosion (ii) D-removal and C-erosion rates depend strongly on film structure and (iii) the D release rate during oxidation is a critical function of the specimen temperature. 

Oxidation by heat, by radiofrequency plasma, chemically, or elec-trochemically (cathodic and extreme anodic polarization cycles). The resulting surface can be linked to enzymes directly or with a coupling agent (58, 79,80, 152, 153). 

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