Thermochemistry and Kinetics of Gas-Phase Reactions Relevant to the CVD of Coatings: New Data for Process Models

1998 ◽  
Vol 555 ◽  
Author(s):  
M. D. Allendorf ◽  
C. F. Melius ◽  
A. H. McDaniel
Keyword(s):  
Gas Phase ◽  
Hexagonal Boron Nitride ◽  
Precursor Chemistry ◽  
Process Models ◽  
Phase Reaction ◽  
Gas Phase Reactions ◽  
Flow Reactors ◽  
Powerful Approach

AbstractUnderstanding the role of gas-phase reactions is an important step in the development of useful CVD process models. In this article, we review the general types of gas-phase reactions that can occur and discuss quantum-chemistry techniques for predicting their thermochemistry and kinetics. We also describe the use of high-temperature flow reactors to measure gas-phase reaction kinetics. Coupling these theoretical and experimental methods is a powerful approach to the characterization of CVD precursor chemistry. We illustrate this in a discussion of the reaction between BC13 and NH3, which is important in the deposition of hexagonal boron nitride coatings.

scholarly journals Role of (H2O)n (n = 1–2) in the Gas-Phase Reaction of Ethanol with Hydroxyl Radical: Mechanism, Kinetics, and Products

ACS Omega ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 5805-5817 ◽  
Author(s):  
Li Xu ◽  
Narcisse T. Tsona ◽  
Shanshan Tang ◽  
Junyao Li ◽  
Lin Du
Keyword(s):  
Hydroxyl Radical ◽  
Gas Phase ◽  
Radical Mechanism ◽  
Phase Reaction ◽  
Gas Phase Reaction

The Role of Starting Potential in the Kinetics of Chemical Reactions under Electrodeless Discharge

1970 ◽  
Vol 25 (11) ◽  
pp. 1772
Author(s):  
T.S.R Ao ◽  
A. Patil
Keyword(s):  
Gas Phase ◽  
Chemical Reactions ◽  
Electric Discharge ◽  
Specific Rate ◽  
Gas Phase Reactions ◽  
Electrodeless Discharge ◽  
First Order ◽  
Kinetics Of

Abstract It has been shown that in kinetically first order gas phase reactions occuring under electric discharge, such as the decomposition of N2O, the application, at various initial pressures, of the same multiple of the respective starting potential ensures that the reaction occurs at the same specific rate.

Homogeneous Oxidation of Hydrogen in Catalytic Mini/Microchannels

2011 ◽  
Author(s):  
Azad Qazi Zade ◽  
Metin Renksizbulut ◽  
Jacob Friedman
Keyword(s):  
Gas Phase ◽  
Surface Reactions ◽  
Operating Conditions ◽  
Planar Geometry ◽  
Channel Height ◽  
Phase Reaction ◽  
Gas Phase Reactions ◽  
Radical Chain ◽  
Oxidation Of Hydrogen ◽  
Volume Method

Gas phase reaction effects in the catalytic oxidation of hydrogen on platinum-coated minichannels and microchannels are investigated numerically in planar geometry. The main objective of this work is to identify the relative importance of the gas phase and surface reactions under different operating conditions. A collocated finite-volume method is used to solve the governing equations. Detailed gas phase and surface reaction mechanisms along with a multi-component diffusion model are used. As the channel size is reduced, heat and radical losses to the walls can significantly alter the combustion behavior. While catalytic walls help in sustaining the gas phase reactions at very small length scales by reducing the heat losses to the walls owing to heat release associated with the surface reactions, they may inhibit homogeneous reactions by extracting radicals due to typically high absorption rates of such species at the walls. Thus, the radical chain mechanisms can be significantly altered by the presence of wall reactions, and the build-up of radical pools in the gas phase, which lead to homogeneous ignition, can be suppressed as a consequence. In the present study, the effects of two key parameters, i.e. channel height and the inlet mass flux on the interaction of gas phase and surface reactions will be explored. In each case, the limiting values beyond which the gas-phase reactions become relatively negligible compared to surface reactions will be identified for hydrogen/air mixtures.

Impact of water on the BrO + HO2 gas-phase reaction: mechanism, kinetics and products

2019 ◽  
Vol 21 (36) ◽  
pp. 20296-20307 ◽  
Author(s):  
Narcisse T. Tsona ◽  
Shanshan Tang ◽  
Lin Du
Keyword(s):  
Reaction Mechanism ◽  
Gas Phase ◽  
Hydrogen Abstraction ◽  
Phase Reaction ◽  
Gas Phase Reaction

The role of water in preventing the barrierless hydrogen abstraction in the BrO + HO2 reaction is highlighted.

In-Situ Formation and Characterization of α-Si3N4 Whiskers from Nano Amorphous Si-N-C Powders

1994 ◽  
Vol 363 ◽  
Author(s):  
Ya-Li Li ◽  
Yong Liang ◽  
Zhuang-Qi Hu
Keyword(s):  
Gas Phase ◽  
Whisker Growth ◽  
Process Conditions ◽  
Phase Reaction ◽  
In Situ Formation ◽  
Amorphous Si ◽  
Xrd Techniques ◽  
Vs Mechanism

Abstractα-Si3N4 whiskers were formed from laser-synthesized nanoscale amorphous Si-N-C powders at 1873K under 1 atm N2. The as-formed whiskers were characterized by TEM, STEM, XRD techniques and the process conditions for the whisker growth were studied. The whiskers exhibit various morphologies such as the long thick straight, the prismatic, the ribbon-like, and knuckled whiskers. The gas phase reaction among N2, SiO, and CO gases leads to Si3N4 whisker growth on the pre-crystallized α-Si3N4 grains by the Vapor-Solid (VS) mechanism along specific crystal planes such as {1101}., which ensures an in-situ formation. No addition of other catalyst and the atomic combination of the elements in the Si-N-C powders ensure a high purity of the whiskers.

Gas-phase reactions of anions with halogenated methanes at 297 ± 2 K

1976 ◽  
Vol 54 (10) ◽  
pp. 1643-1659 ◽  
Author(s):  
K. Tanaka ◽  
G. I. Mackay ◽  
J. D. Payzant ◽  
D. K. Bohme
Keyword(s):  
Gas Phase ◽  
Rate Constants ◽  
Hydrogen Atom Transfer ◽  
Gas Phase Reactions ◽  
Phase Measurements ◽  
Displacement Reactions ◽  
Nucleophilic Reactivity ◽  
Apparent Activation Energies

The rate constants for a number of exothermic displacement (SN2) reactions of the type X− + CH3Y → Y− + CH3X where X− = H−, O−, C−, F−, S−, Cl−, OH−, C2−, CN−, SH−, S2−, C2H−, NH2−, NO2−, CHF−, CH2Cl−, CH2Br−, CH3O−, CH3S−, and CH3NH− and Y = F, Cl, and Br, have been measured in the gas phase at 297 ± 2 K using the flowing after-glow technique. These gas-phase measurements provided an opportunity to determine the intrinsic nucleophilic reactivity of 'nude' anions and hence to assess the role of solvation in the kinetics of SN2 reactions proceeding in solution. Comparisons of the experimental rate constants with rate constants calculated using classical theories of capture indicate that several displacement reactions may possess large intrinsic energies of activation, [Formula: see text]. Correlations were found between apparent activation energies and the heats of reaction. These correlations provided a convenient classification of the various anion nucleophiles. Displacement was observed to compete with proton transfer in reactions involving nucleophiles of high intrinsic basicity and with hydrogen atom transfer and H2+ transfer in the reactions of the O− radical anion.

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