Thermal oxidation processing role

The thermal oxidation process is an essential feature of planar-device fabrication and plays an important role in the diffusion of dopants in Si. In the thermal oxidation process, Si reacts with either oxygen or water vapor at temperatures between 600 and 1250 °C to form Si02. The oxidation reaction may be represented by the following two reactions ... 

Commercial polymers are believed to contain reactive groups such as hydroperoxide, carbonyl, and unsaturated groups. These groups often play important roles for the thermal oxidation processes of the polymers (1,2,9,10,43,44). Therefore, one may consider also the effects of the oxidation products originating from these reactive groups at the very beginning of the oxidation, when the mechanism of the copper-catalyzed oxidation of the polymer was discussed. Further experiments on the effects of various oxidation products on the thermal oxidation of the polymer will be published. 

The initiation efficiency and the thermal stability in step-by-step reactions are essentially linked to the dissociation energy, Ed, of the weakest bond. In the frame of oxidation processes, it is clear that the weakest bond is the 0-0 bond of peroxides (140 kJ mol-1, against typically 350 kJ mol-1 for a -C-C- aliphatic bond, and 380 kJ mol-1 for a C-H bond in an aliphatic methylene). This explains the quasi-exclusive role played by peroxides in the initiation of chain oxidation at low temperatures. 

Further developments of the work include a more accurate study of the mechanisms of desulfurization processes using instrumental improvements. This will enable an easy quantitation of gas yield and a thermochemical approach of elemental processes. We also have been using model polymers to better study the interactions of pyrite and sulfur with the organic matrix during coal pyrolysis, oxidation and combustion (34 and to examine more accurately the specific role of organic sulfur in thermal degradation processes. 

A previously described kinetic model for polyethylene radical chain oxidation is tentatively extended to include the conditions relevant to embrittlement behavior in the case of thermal oxidation at 90°C. The important roles of chemi-crystallization and morphology as a follow-up to initial chemical changes are discussed. The philosophy of how chemical reactions will ultimately lead to physical polymer changes apparent in Mw and lamellar properties, and how these processes could be discussed in terms of advanced modeling strategies is briefly reviewed. 

It can be expected that this approach will result in a new physical (microstructural) rather than a chemical method of control and modification of physicochemical properties, by variation of the specific surface, the number and size of macro- and microcells. Taking into account the fundamental role of the specific surface in the processes of thermal oxidation, combustion, asrp-tion, mass and gas transfer, one may also hope for the development of a more accurate mathematical apparatus for predicting the entire complex of physico-mechanical properties and of the behavior and aging in various temperature-humidity media. The development of such an ap-... 

Surrounding atmosphere influences the formation of either decay product in the process of destruction. So in the work [193] it has been found that in nitrogen atmosphere at isothermal heating at 160 °C mainly benzoic acid and esters are formed. Since oxidative processes are absent at thermal destruction in nitrogen atmosphere then one may come to a conclusion that benzoic acid and esters are the products of thermal decay of PETP fibre. At thermal destruction of PETP-fibre thermal decay plays a very important role, especially at the beginning of the destruction process. 

Monohydric phenols, the most applied group of phenolic antioxidants, are changed via phenoxyls into more types of products. The C-C coupling reactions leading to the antioxidation-efficient multinuclear phenols play a favourable role. The formation of quinone methionid compounds which stain polyolefins cannot be avoided in the transformation process. However, these compounds exhibit a retardation effect in thermal oxidation and are able to quench singlet oxygen. The least favourable properties have alkylperoxycyclohexadienones and dioxycyclohexa-dienones, which initiate both the thermal and photochemical oxidation. Products of their subsequent transformations are either inactive or have a weak retardation effect. 

Thermally grown oxide (TOO), generated in the area between an outer ceramic layer and the bond coat area, as an effect of oxidation of the bond coat during oxidation and thermal shocks. Its role is to inhibit the process of oxidation of the bond coat [5],... 

Both this study and later work by Botelho and co-workers [13] showed that, unlike polyolefins, the thermo-oxidative degradation of PET involves non-oxidative thermal degradation processes, especially in the early stages. The overall thermo-oxidative process in PET is therefore extremely complex. Recent studies [19,20] using state-of-the-art mass spectroscopic techniques have provided further evidence for the role of hydroxylated terephthalate fragments in PET discoloration. 

A number of questions concerning the thermal oxidation still remain unanswered, including the problem of transport of charged and neutral oxidants, the formation of structural defects at the Si-Si02 interface, and the role of surface states [2, 5, 7, 8], The Si oxidation process depends on several factors, such as the crystallographic structure at the surface, the type and level of doping in the substrate, the nature of defects, and the surface roughness [2]. 

Styrenic Polymers Stabilization of polystyrene and its copolymers is necessary for articles expected to be exposed to solar radiation or indoor fluorescent lighting. Because of the signiflcant role played by thermal oxidation products in the effect of these sources on the polymers, thermal stabilization at the processing stage is required to reduce their sensitivity to light. The use of a phenolic antioxidant was shown to increase the retention of mechanical properties and. 

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