Synthesis and Structure Characterization of Chromium Oxide Prepared by Solid Thermal Decomposition Reaction

2006 ◽  
Vol 110 (1) ◽  
pp. 178-183 ◽  
Author(s):  
Li ◽  
Zi F. Yan ◽  
Gao Q. Lu ◽  
Zhong H. Zhu
Keyword(s):  
Thermal Decomposition ◽  
Chromium Oxide ◽  
Decomposition Reaction ◽  
Structure Characterization ◽  
Solid Thermal Decomposition

scholarly journals Kinetics of White Soft Minerals (WSMs) Decomposition under Conditions of Interest for Astrobiology: A Theoretical and Experimental Study

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 101 ◽  
Author(s):  
Gaia Micca Longo ◽  
Marcella D’Elia ◽  
Sergio Fonti ◽  
Savino Longo ◽  
Francesca Mancarella ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Decomposition Reaction ◽  
Gas Diffusion ◽  
Spectroscopic Technique ◽  
Experimental Results ◽  
Additional Contribution ◽  
Atmospheric Entry ◽  
Entry Models ◽  
Kinetics Of

In this paper, the thermal decomposition kinetics of a class of minerals that we call White Soft Minerals (WSMs) is studied by means of theoretical and experimental methods, in connection to the transport of extraterrestrial organic matter to Earth and the possible use of the decomposition reaction in the characterization of these minerals in space. WSMs include, under a single denomination, carbonates and sulphates of Mg, Fe, and Ca. To improve the present knowledge of the properties of such materials, we use the following techniques: kinetic models for chemical decomposition, atmospheric entry models, spectroscopy, and gravimetric analyses. Model results show that the atmospheric entry of WSM grains is strongly affected by their thermal decomposition. The decomposition reaction, being strongly endothermic, tends to significantly lower the grain temperature during the atmospheric entry, especially at high altitudes and for grazing entries. A previously proposed infrared spectroscopic technique to evaluate the degree of advancement of the reaction is found to be in good agreement with gravimetric measurements for calcium carbonate. The numerical model developed for the atmospheric entry scenarios is used to interpret experimental results. These main findings show that an additional contribution to the reaction enthalpy is needed to reproduce the experimental results, suggesting that the present theoretical model needs improvements such as the account of gas diffusion in the materials.

Fast synthesis of MoO3-x and its catalytic effect on the thermal decomposition of ammonium perchlorate based molecular perovskite (DAP-4)

2021 ◽  
Author(s):  
Xiaoxia Li ◽  
Shuaida Zhu ◽  
Qi Jia ◽  
Haixia Zhao ◽  
Yuqi Cao ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Ammonium Perchlorate ◽  
Reaction Rate ◽  
Decomposition Reaction ◽  
Reaction Rate Constant ◽  
Structure Characterization ◽  
Maximum Heat ◽  
Maximum Heat Release ◽  
Positive Effect ◽  
Fast Synthesis

Abstract: In this work, we proved that MoO3-x has a positive effect on the thermal decomposition of ammonium perchlorate based molecular perovskite (H2dabco)[NH4(ClO4)3] (DAP-4). MoO3-x was prepared by heat-treatment, and the morphology, structure and thermal decomposition performance were characterized. The morphology and structure characterization results showed that MoO3-x was an irregular layered structure material, and Mo element was mainly in the +6 chemical valence state, with a small amount of Mo5+. Thermal analysis results showed that the thermal decomposition peak temperature of DAP-4 was effectively reduced from 394.4 °C to 353.7 °C, 321.4 °C, and 312.5 °C in the presence of 1 %, 5 %, and 10 % MoO3-x, respectively. It is particularly worth noting that the maximum heat release rate of the DAP-4/10 % MoO3-x mixture was increased by 4.9 times compared with pure DAP-4. Through the two classic thermal decomposition kinetic methods, Kissinger and Starink, the reliable kinetic parameters of DAP-4/MoO3-x were obtained. The increase of the reaction rate constant k indicated that the maximum thermal decomposition reaction rate of DAP-4 was effectively improved. This work provided a feasible technology for using MoO3-x as an effective catalyst to improve the thermal performance of DAP-4.

Thermal Decomposition and Solid Characterization of Calcium Oxide in Limestone Calcination

2008 ◽  
Vol 591-593 ◽  
pp. 352-357 ◽  
Author(s):  
Bruno D. Soares ◽  
Carla Eponina Hori ◽  
Carlos E.A. Batista ◽  
Humberto Molinar Henrique
Keyword(s):  
Mass Transfer ◽  
Thermal Decomposition ◽  
Decomposition Reaction ◽  
Bet Surface Area ◽  
Textural Characterization ◽  
Process Operation ◽  
Thermodynamic Effects ◽  
Carbon Dioxide Co2

This work is concerning to production of quicklime (CaO) from thermal decomposition of the calcite limestone (CaCO3) using analytical and instrumental techniques (TGA and MS) to evaluate kinetic and thermodynamic effects as well as heat/mass transfer associates with the process operation. On the other hand, experiments of morphologic, structural and textural characterization (XRD, SEM and BET surface area) were carried out in order to evaluate the quality of the quicklime produced. Under experimental studied conditions it was observed that carbon dioxide (CO2) inhibits the thermal decomposition reaction rate. In addition, it was observed that steam (H2O) can catalyze this reaction but it can also cause sintering of the oxide formed. It was also observed that the calcination reaction is greatly limited by mass transfer effects and that the controlled thermal decomposition generates an increase in the solid porosity. The formed CO2 have also increased the sintering phenomena in the oxide structure, resulting in less reactive quicklime.

Characterization of microwave-sintered ceramic composites

1993 ◽  
Vol 51 ◽  
pp. 1136-1137
Author(s):  
X. Zhang ◽  
Y. Pan ◽  
T.T. Meek
Keyword(s):  
Matrix Material ◽  
Maximum Output Power ◽  
Ceramic Matrix Composite ◽  
Ceramic Composites ◽  
Processing Technique ◽  
Structure Characterization ◽  
Alumina Powder ◽  
Maximum Output ◽  
Sintered Ceramic

Industrial microwave heating technology has emerged as a new ceramic processing technique. The unique advantages of fast sintering, high density, and improved materials properties makes it superior in certain respects to other processing methods. This work presents the structure characterization of a microwave sintered ceramic matrix composite.Commercial α-alumina powder A-16 (Alcoa) is chosen as the matrix material, β-silicon carbide whiskers (Third Millennium Technologies, Inc.) are used as the reinforcing element. The green samples consisted of 90 vol% Al2O3 powder and 10 vol% ultrasonically-dispersed SiC whiskers. The powder mixture is blended together, and then uniaxially pressed into a cylindrical pellet under a pressure of 230 MPa, which yields a 52% green density. The sintering experiments are carried out using an industry microwave system (Gober, Model S6F) which generates microwave radiation at 2.45 GHz with a maximum output power of 6 kW. The composites are sintered at two different temperatures (1550°C and 1650°C) with various isothermal processing time intervals ranging from 10 to 20 min.

Visualization and characterization of localized outgassing position on surface-treated specimens: Chromium oxide layer on stainless steel

2019 ◽  
Vol 492 ◽  
pp. 280-284
Author(s):  
Naoya Miyauchi ◽  
Tomoya Iwasawa ◽  
Taro Yakabe ◽  
Masahiro Tosa ◽  
Toyohiko Shindo ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Oxide Layer ◽  
Chromium Oxide ◽  
Chromium Oxide Layer

Synthesis and Characterization of Nanocrystalline ZnO Powders by a Direct Thermal Decomposition Route Using Zinc Nitrate Hexahydrate

2013 ◽  
Vol 770 ◽  
pp. 68-71 ◽  
Author(s):  
Supphadate Sujinnapram ◽  
Uraiphorn Termsuk ◽  
Atcharawan Charoentam ◽  
Sutthipoj Sutthana
Keyword(s):  
Thermal Decomposition ◽  
Crystallization Temperature ◽  
Zinc Nitrate ◽  
Zinc Nitrate Hexahydrate ◽  
Absorption Peak ◽  
Synthesis And Characterization ◽  
Nitrate Hexahydrate ◽  
Different Temperatures ◽  
Zno Powders

The nanocrystalline ZnO powders were synthesized by a direct thermal decomposition using zinc nitrate hexahydrate as starting materials. The precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found to be at 325 oC. The precursors were calcined at different temperatures of 400, 500, and 600°C for 4 h. The structure of the prepared samples was studied by XRD, confirming the formation of wurtzite structure. The synthesized powders exhibited the UV absorption below 400 nm (3.10 eV) with a well defined absorption peak at around 285 nm (4.35 eV). The estimated direct bandgaps were obtained to be 3.19, 3.16, and 3.14 eV for the ZnO samples thermally decomposed at 400, 500, and 600°C, respectively.

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