scholarly journals Effect of atmosphere on the fabrication of Si2N2O matrix composites

2018 ◽  
Vol 12 (1) ◽  
pp. 66-71
Author(s):  
Wei Li ◽  
Fan Zhang ◽  
Ning Li ◽  
Tingting Su ◽  
Bingbing Fan ◽  
...  
Keyword(s):  
Free Energy ◽  
Reaction Mechanism ◽  
Gradient Structure ◽  
Matrix Composites ◽  
Air Atmosphere ◽  
N2 Atmosphere ◽  
O2 Concentration ◽  
Concentration Changes ◽  
Si3n4 Ceramics ◽  
Kinetics And Thermodynamic

Si2N2O matrix composites were fabricated by solid/gas reaction in air or N2 atmosphere. The effects of atmosphere on the phase and microstructure of the composites were investigated. The reaction mechanism of Si2N2O system was discussed by analysing the variation of the Gibbs free energy with temperature. The effect of N2 and air on sintering of Si2N2O matrix composites was discussed in relation to observed kinetics and thermodynamic calculations. The results showed that gradient structure of Si2N2O matrix composites were obtained in N2 atmosphere. While high N2 concentration was useful for the formation of the pure ?-Si3N4 ceramics, low N2 concentration was proposed to form the pure Si2N2O ceramics. However, in the air atmosphere, structure of the Si3N4/SiO2 composites is homogeneous without the gradient structure appearing. Its composition is a little different as the O2 concentration changes.

scholarly journals Experimental validation of the reaction mechanism models of dechlorination and [Zn] reclaiming in the roasting steelmaking zinc-rich dust process

2020 ◽  
Vol 39 (1) ◽  
pp. 107-116
Author(s):  
Hongyang Wang ◽  
Kai Dong ◽  
Rong Zhu
Keyword(s):  
Reaction Mechanism ◽  
Dust Particle ◽  
Chemical Reaction ◽  
Reaction Mechanisms ◽  
Experimental Validation ◽  
Step Process ◽  
Mass Percent ◽  
Mechanism Model ◽  
Air Atmosphere ◽  
Almost All

AbstractThe reaction mechanism models of dechlorination and [Zn] reclaiming in the roasting steelmaking zincrich dust process are studied. The dust collected from a steelwork contains 63.8% zinc and 3.18% chlorine (mass percent), of which, almost all zinc elements exist in ZnO and ZnCl2 forms, and all the chlorine elements are stored in ZnCl2. When the dust is roasted at above 732∘C in an air atmosphere, the ZnCl2 in the steelmaking zinc-rich dust is volatilized into steam and then oxidized into ZnO. Finding the position where the chemical reaction occurs is the key to determining the reaction mechanisms of dechlorination and [Zn] reclaiming. In this study, two groups of thermal experiments are designed and executed for roasting in different atmosphere environments and at different roasting temperatures. Based on the experiment results, the mechanism model is discussed and built, and the reaction of dechlorination and [Zn] reclaiming is shown to be a multi-step process. Because O2 from the air cannot transmit into the dust particle interior or dust bed effectively, the chemical reaction of [Zn] reclaiming occurs in the external gas environment outside of the dust, where the [Zn] recalcining reaction should be limited by the dynamics of new nucleation of ZnO solids.

scholarly journals Sintering of Si3N4 Ceramics in Air Atmosphere Furnace(Part 2)-Agglomeration of Packing Powder and Deterioration of Al2O3 Crucible-

2004 ◽  
Vol 112 (1304) ◽  
pp. 234-237 ◽  
Author(s):  
Shigetaka WADA ◽  
Piyaporn CHAIYAPAK ◽  
Supatra JINAWATH ◽  
Thanakorn WASANAPIARNPONG ◽  
Toyohiko YANO
Keyword(s):  
Air Atmosphere ◽  
Si3n4 Ceramics

scholarly journals The Reaction Mechanism with Free Energy Barriers for Electrochemical Dihydrogen Evolution on MoS2

2015 ◽  
Vol 137 (20) ◽  
pp. 6692-6698 ◽  
Author(s):  
Yufeng Huang ◽  
Robert J. Nielsen ◽  
William A. Goddard ◽  
Manuel P. Soriaga
Keyword(s):  
Free Energy ◽  
Reaction Mechanism ◽  
Energy Barriers

Effects of Interfacial Phenomena and Conduction on an Evaporating Meniscus

2007 ◽  
Author(s):  
Peter C. Wayner
Keyword(s):  
Heat Flux ◽  
Free Energy ◽  
Temperature Field ◽  
Phase Change ◽  
Slip Velocity ◽  
Chemical Potential ◽  
Transport Processes ◽  
Liquid Pressure ◽  
Thickness Profile ◽  
Concentration Changes

An overview of some of the theoretical models describing the effects of chemical potential, excess free energy, free energy gradient, film thickness profile, temperature profile, superheat, thermal conduction, concentration gradient, velocity profile, slip velocity, apparent contact angle, and kinetic theory on the phase change heat transfer processes in an evaporating meniscus are presented. The relative importance of the parameters is demonstrated. Experimental techniques and confirming experimental data are also presented. In essence, the microscopic thickness profile of the evaporating meniscus is measured optically to obtain the details of the liquid pressure field and modeled to give the fluid flow rate and the evaporative heat flux. The macroscopic temperature field of the substrate is measured and numerically modeled to give the microscopic temperature field and a complementary calculation of the evaporative heat flux. For closure, the values of the slip velocity and concentration change on evaporation need to be correctly assumed. The interfacial transport processes are very sensitive to small interfacial temperature and concentration changes, which are difficult, if not impossible, to measure directly. However, the liquid pressure gradients can be directly measured. The effects of the interacting phenomena on the phase change processes are demonstrated using these complementary experimental-modeling procedures. The processes are found to be very complex and simple modeling/experiments can only confirm the general phenomena and give insight.

Effect of Humidity on Friction of Carbon Nitride Coatings Under N2 Gas Lubrication

2005 ◽  
Author(s):  
Koshi Adachi ◽  
Naoya Sodeyama ◽  
Koji Kato
Keyword(s):  
Friction Coefficient ◽  
Relative Humidity ◽  
Carbon Nitride ◽  
Frictional Pair ◽  
Low Friction ◽  
Nitrogen Gas ◽  
N2 Atmosphere ◽  
Gas Atmosphere ◽  
O2 Concentration ◽  
Nitride Coatings

The effect of humidity on friction properties of carbon nitride (CNx) in nitrogen (N2) atmosphere were investigated by using a ball-on-disk tribo-tester in atmospheres with controlled humidity and oxygen concentration. It was concluded that friction coefficient in the combination of CNx/CNx and Si3N4/CNx in N2 gas atmosphere were reduced from the order of 0.1 to 0.01 by decreasing of humidity from 40% RH to 0% RH when the O2 concentration is kept below 100 ppm. Further, stability of low friction of CNx/CNx in N2 gas atmosphere was confirmed experimentally. The frictional pair of CNx/CNx provided low and a stable friction coefficient of 0.01 in 99.9% nitrogen gas condition under low relative humidity of 2% or less.

Effects of Al Content on Phase Composition of Zr-Al-O-N Composites

2010 ◽  
Vol 97-101 ◽  
pp. 1637-1640 ◽  
Author(s):  
Rong Lin Wang ◽  
Jing Long Bu ◽  
Zhi Fa Wang ◽  
Jia Lin Sun
Keyword(s):  
Phase Composition ◽  
Reaction Mechanism ◽  
Raw Materials ◽  
Formation Reaction ◽  
Al Content ◽  
N2 Atmosphere ◽  
Sem Analyses

Zr-Al-O-N composites were prepared in N2 atmosphere at 1600oC with Ca-PSZ and Al powders as raw materials. Phase composition of the composites and formation reaction mechanism were investigated by XRD and SEM analyses. With Al content increaseing from 1% to 50%, phase composition of the composites were changed step by step. The results showed that phase compositions of the composites are related to Al content.

scholarly journals Thermodynamic Study of Hydrolysis Reactions in Aqueous Solution fromAb InitioPotential and Molecular Dynamics Simulations

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
S. Tolosa ◽  
A. Hidalgo ◽  
J. A. Sansón
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solution ◽  
Free Energy ◽  
Reaction Mechanism ◽  
Molecular Dynamics Simulations ◽  
Infinite Dilution ◽  
Theoretical Study ◽  
Water Model ◽  
Dynamics Simulations ◽  
Hydrolysis Of

A procedure for the theoretical study of chemical reactions in solution by means of molecular dynamics simulations of aqueous solution at infinite dilution is described usingab initiosolute-solvent potentials and TIP3P water model to describe the interactions. The procedure is applied to the study of neutral hydrolysis of various molecules (HCONH2, HNCO, HCNHNH2, and HCOOCH3) via concerted and water-assisted mechanisms. We used the solvent as a reaction coordinate and the free energy curves for the calculation of the properties related with the reaction mechanism, namely, reaction and activation energies.

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