Papers by Keyword: Activation Energy

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Authors: Gilles Adjanor, Manuel Athènes
244
Authors: Seung Hwan Byun, Seung Hyun Cho
Abstract: 4,4’-Diglycidyloxy-α-methylstilbene (DOMS) was synthesized and characterized with cross-polarized optical microscopy (POM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Activation energies for decomposition (Ed) by TGA were determined as a function of conversion by weight loss process.
628
Authors: Juan Daniel Muñoz-Andrade
Abstract: ±Abstract. By applying the new quantum mechanics and relativistic mathematical model, proposed by Muñoz-Andrade, on the experimental results reported previously by Aghaie-khafri and Adhami [5], the true activation energy for hot deformation of 15-5 PH stainless steel is obtained over the temperature range of 900-1150°C and strain rates varying between 0.001 and 0.5s-1. It is interesting to contrast the results of this theoretical work with the main results of the apparent activation energy obtained for the same data, but applying the common methodology. It is shown that the true activation energy increased as the hot deformation is increased. Moreover, the true activation energy decreased as the strain rate is increased. The mean value of the true activation energy (289 kJ/mol) at high strain rate, ξ=0.5s-1, for dynamic recrystallization over the temperature range of 900-1150°C is in a closed agreement with the value of activation energy for self-diffusion in γ iron (280 kJ/mol) in dissimilarity of the result of the apparent activation energy (49221 kJ/mol) obtained beforehand by Aghaie-khafri and Adhami [5]. The results obtained in this work by the quantum mechanics and relativistic mathematical model are widely satisfactory; because essentially they are over the crucial limitations of the common methodology to obtain the activation energy at each thermo-mechanical metalworking condition. Keywords: Activation Energy, Hot Deformation, Dynamic Recrystallization, Quantum Mechanics, Special Relativity Theory.
1217
Authors: Wei Min Mao, Mao Hua Zhang, Ping Yang, Kai Ping Wang
Abstract: The recrystallization behaviors of 60% rolled Fe-wt.3%Si and Fe- wt.3%Si-Mn-S alloys containing coarsen MnS particles were observed in temperature range 600°C~1000°C. The activation energy for recrystallization was determined according to an Arrhenius type of relationship. It was found that the activation energy in the temperature range 600°C~750°C was much higher than that in the temperature range 850°C~1000°C. Thermo-mechanical calculation indicates that there are hardly precipitation behaviors of MnS particles in 600°C~1000°C. Fe3C will precipitate below 650°C and Cottrell atmosphere will form just above 650°C, which induces dragging effect against the boundary migration during recrystallization and increase the activation energy. The activation energy determined was about 99kJ/mol or 217kJ/mol in Fe-3%Si alloy and 91kJ/mol or 220kJ/mol in Fe-3%Si-Mn-S alloy for the recrystallization in high temperature range of 850°C~1000°C or low temperature range of 600°C~750°C respectively.
181
Authors: Kazumasa Yamada, M. Ito, Masaaki Tatsumiya, Yoshiaki Iijima, Kazuaki Fukamichi
815
Authors: Jin Ping Wang, Bo Yuan, Jian Wang, Yi Luo
Abstract: Activation energy is an important parameter which determines thermal stability of solar selective absorbing coating. In this investigation, a new performance criterion (PC) was defined for solar selective coating according to our modified equation of photo-thermal conversion. Then the activation energy of Cu/stainless steel (SS)-AlN/SiAlOx solar selective absorbing coating was measured. Cu/SS-AlN/SiAlOx tandem films were deposited by magnetron sputtering. Accelerated ageing tests were performed on the coating at 500°C and 550°C, under the atmosphere, calculating PC from the reflectance spectrum and measuring the failure time. According to Arrhenius equation, the activation energy and the equivalent life span of Cu/SS-AlN/SiAlOx tandem film at 400°C were determined to be about 187.4kJ/mol and more than 16260 hours, respectively.
870
Authors: Chang Seon Shon, Dongoun Lee
Abstract: The utilization of fly ashes produced by circulated fluidized bed combustion (CFBC) has been limited in construction application due to their inherent high sulfate and carbon contents although CFBC fly ash exhibits very good binding properties without requiring any supplementary activator. This study reports alkali silica reaction (ASR) behavior of CFBC fly ash geopolymer mortars in terms of activation energy using a modified ASTM C 1260/C 1567. Two different strengths of NaOH solution were used to test reactive and potentially reactive aggregates in the presence of CFBC fly ash. The other variables included a longer test period of 3 months and three different temperatures, namely 60°C, 70°C, and 80°C. It was observed that there was no significant expansion in CFBC fly ash based geopolymer mortar regardless of variation of temperature and alkalinity of test solution. Activation energy of CFBC fly ash geopolymer for ASR was higher than that of plain cement mortar irrespective of strength of NaOH solution.
77
Authors: Yusuke Hara
Abstract: A self-oscillating polymer chain consisting of N-ethylacrylamide (NEAAm) and a Ru catalyst of the BelousovZhabotinsky (BZ) reaction was prepared. The polymer chain underwent soluble-insoluble self-oscillation induced by the BZ reaction, originating from the differing solubility of the Ru moiety in the reduced and oxidized states. The amplitude of self-oscillation was small compared to that for the polymer chains prepared from N-Isopropylacrylamide (NIPAAm). The activation energy observed with the novel, NEAAm-based polymer chain was 68 kJ/mol, similar to that found with the NIPAAm-based polymer chain and normal (no Ru catalyst incorporated in the polymer) BZ reaction.
1212
Authors: N. Singh
147
Authors: Tomas Chrebet, Martinka Jozef, Karol Balog, Zuzana Turnova
Abstract: On the base of experimental observations of mass loss rate in dependence of temperature in isothermal condition in circulating air atmosphere was determined the activation energy of lignocellulosic materials degradation without and with retardants. Experiment was performed in an electrically heated hot-air furnace according to ISO 871 standard (Setchkin furnace) in conjunction with precision scales. Degradation of lignocellulosic materials was performed at various temperatures and various air-flow speeds. Pure cellulose as a model compound was impregnated by water solution of KHCO3 and (NH4)2HPO4.
1179
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