Thermodynamics Analysis on Combustion Synthesis of β-SiAlON

2014 ◽  
Vol 787 ◽  
pp. 383-386 ◽  
Author(s):  
Xue Mei Yi ◽  
Jing Niu ◽  
Tomohiro Akiyama
Keyword(s):  
Temperature Profile ◽  
Combustion Synthesis ◽  
Nitrogen Pressure ◽  
Main Reaction ◽  
Maximum Temperature ◽  
Nitrogen Gas ◽  
Exothermic Reactions ◽  
Thermodynamics Analysis ◽  
Intermediate Products ◽  
Endothermic Reactions

Combustion synthesis (CS) of β-SiAlON (z= 1) was carried by heating the raw mixtures of Si, Al, and SiO2under a constant nitrogen pressure of 1 MPa to the preconcerted temperature. The temperature profile was recorded by a W-Re thermocouple, which showed several exothermic and endothermic reactions during the entire CS process. The maximum temperature reached above 1900°C, and two main exothermic reactions at ~800 °C and ~1350 °C were found. The XRD analyses indicated that the main intermediate products are AlN, SiO2, and Al2O3before β-SiAlON was synthesized finally. From our analyses, Al reacted with nitrogen gas at ~800 °C first, then at ~1350 °C, the main reaction occurred and the final product was obtained synchronously.

scholarly journals Combustion Synthesis of Aluminum Oxynitride in Loose Powder Beds

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4182
Author(s):  
Alan Wilmański ◽  
Magdalena Zarzecka-Napierała ◽  
Zbigniew Pędzich
Keyword(s):  
Combustion Synthesis ◽  
Metal Powder ◽  
Weight Ratio ◽  
Nitrogen Pressure ◽  
Alumina Powder ◽  
Metal Powders ◽  
Aluminum Oxynitride ◽  
Synthesis Conditions ◽  
Aluminum Metal ◽  
Loose Powder

This paper describes combusting loose powder beds of mixtures of aluminum metal powders and aluminum oxide powders with various grain sizes under various nitrogen pressure. The synthesis conditions required at least 20/80 weight ratio of aluminum metal powder to alumina powder in the mix to reach approximately 80 wt% of γ-AlON in the products. Finely ground fused white alumina with a mean grain size of 5 μm was sufficient to achieve results similar to very fine alumina with 0.3 μm grains. A lower nitrogen pressure of 1 MPa provided good results, allowing a less robust apparatus to be used. The salt-assisted combustion synthesis upon addition of 10 wt% of ammonium nitrite resulted in a slight increase in product yield and allowed lower aluminum metal powder content in mixes to be ignited. Increasing the charge mass five times resulted in a very similar γ-AlON yield, providing a promising technology for scaling up. Synthesis in loose powder beds could be utilized for effective production of relatively cheap and uniform AlON powder, which could be easily prepared for forming and sintering without intensive grounding and milling, which usually introduce serious contamination.

Chemically activated combustion synthesis of AlON under high nitrogen pressure

2021 ◽  
Vol 232 ◽  
pp. 111560
Author(s):  
Tigran G. Akopdzhanyan ◽  
Sergey I. Rupasov ◽  
Stepan Vorotilo
Keyword(s):  
Combustion Synthesis ◽  
Nitrogen Pressure ◽  
High Nitrogen ◽  
High Nitrogen Pressure

Combustion Synthesis of Si3N4 from Si/NH4Cl at Low Nitrogen Pressure

2008 ◽  
Vol 368-372 ◽  
pp. 1767-1770 ◽  
Author(s):  
Yi Xiang Chen ◽  
Jiang Tao Li ◽  
Zhi Ming Lin ◽  
Guang Hua Liu ◽  
S.L. Yang ◽  
...  
Keyword(s):  
Combustion Synthesis ◽  
Combustion Temperature ◽  
Profile Analysis ◽  
Combustion Velocity ◽  
Nitrogen Pressure ◽  
Analysis Method ◽  
Α Phase ◽  
Steady Combustion ◽  
Combustion Wave Velocity ◽  
Low Nitrogen

Combustion synthesis (CS) of Si3N4 was accomplished by using as-milled Si/NH4Cl as reactants at low nitrogen pressure. The additive of NH4Cl decreased the combustion temperature and promoted the Si nitridation. Full nitridation of Si was achieved by burning Si in pressurized nitrogen with 10 ~ 25 wt. % NH4Cl as additives while no Si3N4 diluent added. The maximum combustion temperature (Tc), the combustion velocity (u) together with the α-Si3N4 content and mean particle size (d50) of the powder products were found to be great dependent on the NH4Cl content added in the reactants. Fine Si3N4 powder products with α-phase content up to 85 wt. % were obtained via steady combustion mode. A mathematical approach named combustion wave velocity methods for the analysis of temperature profiles in CS was proposed and the reaction kinetics was discussed. The apparent activation energy calculated according to the temperature profile analysis method is 29.7 kJ/mol, which agrees well with the corresponding low temperature nitriding combustion of Si.

The Effect of Diluent on Combustion Synthesis of Si3N4-SiC-TiN Ceramics with Small Diameter

2007 ◽  
Vol 336-338 ◽  
pp. 1084-1086 ◽  
Author(s):  
Xue Jun Zhang ◽  
Yong Ting Zheng ◽  
Jie Cai Han
Keyword(s):  
Combustion Synthesis ◽  
Small Diameter ◽  
Diameter Ratio ◽  
Nitrogen Gas ◽  
Free Silicon ◽  
Multiphase Ceramics

Si3N4-TiN-SiC multiphase ceramics was synthesized from TiSi2 and SiC powders by combustion synthesis. The effect of dilute content on conversion percentage was calculated in theory assuming that there is no penetration of nitrogen gas, and combustion synthesis was carried under different conditions. The results show that the increase of diluent content in certain extent is helpful for nitrification of TiSi2 and free silicon were detected in the 30wt% and 40wt% SiC-diluted samples with 45vol% porosity while no silicon were found in 50vol% porosity green parts. The increase in diluent content and porosity of the compacts are favorable for the development of rod-like β-Si3N4 and the long-diameter ratio of β-Si3N4 is increase as the increase of these two values.

A Multi-Dwell Temperature Profile Design for the Cure of Thick CFRP Composite Laminates

2021 ◽  
Author(s):  
Wenchang Zhang ◽  
Yingjie Xu ◽  
Xinyu Hui ◽  
Weihong Zhang
Keyword(s):  
Temperature Profile ◽  
Composite Laminates ◽  
Optimization Method ◽  
Maximum Temperature ◽  
Nsga Ii ◽  
Multi Objective ◽  
Optimization Result ◽  
Design Variables ◽  
Cure Time ◽  
Thick Laminates

Abstract This paper develops a multi-objective optimization method for the cure of thick composite laminates. The purpose is to minimize the cure time and maximum temperature overshoot in the cure process by designing the cure temperature profile. This method combines the finite element based thermo-chemical coupled cure simulation with the non-dominated sorting genetic algorithm-II (NSGA-II). In order to investigate the influence of the number of dwells on the optimization result, four-dwell and two-dwell temperature profiles are selected for the design variables. The optimization method obtains successfully the Pareto optimal front of the multi-objective problem in thick and ultra-thick laminates. The result shows that the cure time and maximum temperature overshoot are both reduced significantly. The optimization result further illustrates that the four-dwell cure profile is more e ective than the two-dwell, especially for the ultra-thick laminates. Through the optimization of the four-dwell profile, the cure time is reduced by 51.0% (thick case) and 30.3% (ultra-thick case) and the maximum temperature overshoot is reduced by 66.9% (thick case) and 73.1% (ultra-thick case) compared with the recommended cure profile. In addition, Self-organizing map (SOM) is employed to visualize the relationships between the design variables with respect to the optimization result.

scholarly journals Investigation on the effect of electrode tip on formation of metal droplets and temperature profile in a vibrating electrode electroslag remelting process

Open Physics ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 743-751 ◽  
Author(s):  
Fang Wang ◽  
Jakov Baleta ◽  
Qiang Wang ◽  
Baokuan Li
Keyword(s):  
Temperature Profile ◽  
Electroslag Remelting ◽  
Temperature Fields ◽  
Maximum Temperature ◽  
Periodic Pattern ◽  
Coupled Modelling ◽  
Frequency Changes ◽  
Volume Method ◽  
Peak Value ◽  
Metal Droplets

Abstract In the present work, a transient full-coupled modelling approach has been put forward to study the effect of electrode tip on formation of metal droplets and temperature profile in the electromagnetically-controlled electroslag-remelting furnace with vibrating electrode. The electromagnetic field, momentum and energy conservation equations are solved simultaneously based on the finite volume method. The interface of slag and metal is traced using the volume of fluid approach. The results show that in the case of cone tip electrode the average dimension of metal droplets is smaller compared to the flat tip electrode. In addition, the bigger and stretched metal droplets are not observed with the cone tip electrode. The temperature fields with the cone tip electrode are distributed in a prominent periodic pattern compared to the case with flat tip electrode. The maximum temperature zone with the cone tip electrode is located along the z axial in the upper part of slag, not in the lower part. When the frequency changes from 0.17 Hz to 1 Hz, the maximum temperature reduces from 2050 K to 1985 K and the peak value of velocity decreases from 0.20 m/s to 0.125 m/s. When the vibration amplitude varies from 3mm to 6mm, the maximum temperature in the slag cover drops by 3.9% and the peak value of velocity rises by 16.7%.

Combustion Synthesis of Porous Oxynitride Ceramics - Influence of Cocurrent Nitrogen Flow on the Combustion Parameters

2016 ◽  
Vol 683 ◽  
pp. 125-130
Author(s):  
Anatoly Maznoy ◽  
Alexander Kirdyashkin ◽  
Ramil Gabbasov
Keyword(s):  
Mass Transfer ◽  
Combustion Synthesis ◽  
Heat And Mass Transfer ◽  
Combustion Wave ◽  
Current Flow ◽  
Conversion Ratio ◽  
Adiabatic Heating ◽  
Maximum Temperature ◽  
Nitrogen Flow ◽  
Favorable Conditions

It is shown that the organization of co-current flow of the reacting gas during combustion synthesis of porous oxynitride materials leads to intensification of the process. The flow creates favorable conditions for directed heat and mass transfer in reacting media. It results in super-adiabatic heating of the products in the area of the combustion wave. Thus, macrokinetic parameters of the combustion synthesis exceed 10 % than the ones that had been obtained without forced filtering of gaseous reactant. Organization of the process in flowing of the reacting gas allows us to obtain materials with conversion ratio up to 0.95 under the combustion rates up to 0.8 mm/s and maximum temperature in the combustion wave up to 1900 °C.

Combustion synthesis of AlN with melamine as an additive

2006 ◽  
Vol 21 (3) ◽  
pp. 747-753 ◽  
Author(s):  
Gunchoo Shim ◽  
Je-Shin Park ◽  
Sung-Wook Cho
Keyword(s):  
Aluminum Nitride ◽  
Combustion Synthesis ◽  
Reaction Rates ◽  
Nitrogen Pressure ◽  
Chamber Pressure ◽  
Nitrogen Flow ◽  
Optimum Conditions ◽  
X Ray Diffraction ◽  
Diffraction Patterns ◽  
Nitrogen Contents

Melamine (C3H6N6) was used as an additive for synthesizing aluminum nitride by combustion synthesis. It was found that at least 0.1 M of melamine addition to 1 M of aluminum and 0.8 MPa of nitrogen pressure were necessary to initiate a stable reaction. In addition to melamine, however, use of aluminum nitride as a diluent and application of forced nitrogen flow yielded better results. Analyzing the reaction temperatures, reaction rates, nitrogen contents, x-ray diffraction patterns, and scanning electron microscopy photographs, the optimum conditions for synthesizing AlN were established: (i) reactants were 90 wt% (1 M Al + 0.1 M melamine) + 10 wt% AlN diluent, (ii) chamber pressure was 0.9 MPa, and (iii) nitrogen flow rate was 15 l/min. Under these conditions, aluminum nitride with the stoichiometric nitrogen content of 34 wt% could be obtained.

Effects of nitrogen pressure and diluent content on the morphology of gel-cast-foam-assisted combustion synthesis of elongated β-Si3N4 particles

2014 ◽  
Vol 40 (8) ◽  
pp. 12553-12560 ◽  
Author(s):  
Wei Cui ◽  
Yuan Zhu ◽  
Yiyao Ge ◽  
Feiyu Kang ◽  
Xuanyi Yuan ◽  
...  
Keyword(s):  
Combustion Synthesis ◽  
Nitrogen Pressure

Effects of Technical Parameters on the Phase Composition and Microstructure of Yb α-SiAlON Prepared by Combustion Synthesis

2007 ◽  
Vol 280-283 ◽  
pp. 1237-1240 ◽  
Author(s):  
G.H. Liu ◽  
Ke Xin Chen ◽  
He Ping Zhou ◽  
Xiao Shan Ning ◽  
José Maria F. Ferreira
Keyword(s):  
Phase Transformation ◽  
Phase Composition ◽  
Combustion Synthesis ◽  
Nitrogen Pressure ◽  
Nucleation And Growth ◽  
Experimental Results ◽  
Microstructure Development ◽  
Technical Parameters

In this paper, Yb a-sialon powders with elongated grains have been prepared by combustion synthesis. The effects of diluents, nitrogen pressure, adding a-sialon seeds and NH4F on the phase transformation and microstructure development of the samples are discussed systematically. The experimental results show that the addition of diluents, proper nitrogen pressure and additive NH4F can facilitate the nitridation of Si. It was also found that the added a-sialon seeds and NH4F are beneficial to the nucleation and growth of elongated grains.

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