scholarly journals Kinetics of Smelting Chromia–Bearing Vanadiferous Titanomagnetite Ore via High–Temperature CO2–Containing Gas Injection

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1008
Author(s):  
Hanlin Song ◽  
Gongjin Cheng ◽  
Jianxing Liu ◽  
Jinpeng Zhang ◽  
Xiangxin Xue
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Apparent Activation Energy ◽  
Gas Injection ◽  
Reduction Rate ◽  
Co2 Concentration ◽  
Thermodynamic Calculations ◽  
Isothermal Kinetics ◽  
Smelting Process ◽  
Fuel Gas

Through thermodynamic smelting experiments, nonisothermal and isothermal kinetics experiments, the effects of CO2–containing gas injection on the smelting of chromia–bearing vanadiferous titanomagnetite ore were investigated. The experiments at 900 °C, 1000 °C, 1100 °C, 1200 °C, and 1300 °C, and CO2 concentration of 0, 10 vol.%, 20 vol.%, and 30 vol.% were studied. The samples after the kinetics experiments were analyzed through thermodynamic calculations and characterized by XRD, XRF, XPS, and SEM. The results of thermodynamic experiments show that the injection of CO2–containing gas significantly improves the softening–melting–dripping behavior during the smelting process. As the concentration of injected CO2 increased from 0 vol.% to 30 vol.%, the range of softening temperature [T40–T4] decreased from 109 °C to 97 °C, and the range of droplet temperature [Td–Ts] decreased rapidly from 196 °C to 162 °C. Moreover, when CO2 concentration was 20 vol.%, the minimum apparent activation energy of nonisothermal kinetics reached 75.58 kJ·mol−1. Combining the lowest permeability index and the fastest nonisothermal reduction rate, the optimal CO2 concentration in the fuel gas was considered to be 20 vol.%. The isothermal parameters were fitted according to 1 − (1 − α)1/3 − t (CG3 model), and the apparent activation energy was 121.93 kJ·mol−1 (less than 150 kJ·mol−1), which means that the restrictive step of the polymetallic reaction is mainly determined by diffusion. Finally, thermodynamic calculations and characterizations show that CO2–containing gas injection helps titanium stabilize in a higher valence state, which is conducive to improve the high–temperature characteristics of titanium–containing slag.

The activation energy U(T,B) in high temperature superconductor

2020 ◽  
Vol 92 (2) ◽  
pp. 20601
Author(s):  
Abdelaziz Labrag ◽  
Mustapha Bghour ◽  
Ahmed Abou El Hassan ◽  
Habiba El Hamidi ◽  
Ahmed Taoufik ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Activation Energy ◽  
Phase Diagram ◽  
High Temperature ◽  
Apparent Activation Energy ◽  
High Temperature Superconductor ◽  
Flux Flow ◽  
Resistivity Measurements ◽  
Vortex Phase ◽  
The Magnetic Field

It is reported in this paper on the thermally assisted flux flow in epitaxial YBa2Cu3O7-δ deposited by Laser ablation method on the SrTiO3 substrate. The resistivity measurements ρ (T, B) of the sample under various values of the magnetic field up to 14T in directions B∥ab-plane and B∥c-axis with a dc weak transport current density were investigated in order to determine the activation energy and then understand the vortex dynamic phenomena and therefore deduce the vortex phase diagram of this material. The apparent activation energy U0 (B) calculated using an Arrhenius relation. The measured results of the resistivity were then adjusted to the modified thermally assisted flux flow model in order to account for the temperature-field dependence of the activation energy U (T, B). The obtained values from the thermally assisted activation energy, exhibit a behavior similar to the one showed with the Arrhenius model, albeit larger than the apparent activation energy with ∼1.5 order on magnitude for both cases of the magnetic field directions. The vortex glass model was also used to obtain the vortex-glass transition temperature from the linear fitting of [d ln ρ/dT ] −1 plots. In the course of this work thanks to the resistivity measurements the upper critical magnetic field Hc2 (T), the irreversibility line Hirr (T) and the crossover field HCrossOver (T) were located. These three parameters allowed us to establish a phase diagram of the studied material where limits of each vortex phase are sketched in order to optimize its applicability as a practical high temperature superconductor used for diverse purposes.

Effect of high temperature on the apparent activation energy of respiration of fresh produce

2005 ◽  
Vol 37 (3) ◽  
pp. 277-285 ◽  
Author(s):  
Daisuke Nei ◽  
Toshitaka Uchino ◽  
Natsumi Sakai ◽  
Shun-ichirou Tanaka
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Apparent Activation Energy ◽  
Fresh Produce

Nitridation Isothermal Kinetics of In Situ β-Sialon Bonded Al2O3-C Refractories

2016 ◽  
Vol 697 ◽  
pp. 572-575
Author(s):  
Xue Qing Yang ◽  
Nai Peng ◽  
Cheng Ji Deng
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Isothermal Kinetics ◽  
Nitridation Reaction ◽  
Result Show ◽  
Different Temperatures ◽  
Two Stages ◽  
Kinetics Of ◽  
And Diffusion

The kinetics of in-situ β- Sialon bonded Al2O3-C (SAC) refractories were investigated by TGA techniques via isothermal nitridation experiments at different temperatures. The result show that the nitridation process of in-situ β-Sialon bonded Al2O3-C refractories can be divided into two stages: the nitridation reaction rate controlling stage in the first 10 min, and the apparent activation energy of nitridation reaction is 370 kJ/mol ; then the reaction is controlled by both chemical reaction and diffusion rate in the following 110 min, the apparent activation energy of nitridation reaction is 410 kJ/mol.

High Temperature Internal Friction Behavior of Unidirectionally Solidified Al2O3/YAG Eutectic

2010 ◽  
Vol 638-642 ◽  
pp. 2482-2486
Author(s):  
Shunkichi Ueno ◽  
Satoshi Takata ◽  
Yasuhiro Tanabe ◽  
Takashi Akatsu ◽  
Eiichi Yasuda ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Internal Friction ◽  
Single Crystal ◽  
Apparent Activation Energy ◽  
Elevated Temperatures ◽  
Torsional Loading ◽  
Friction Behavior

In this paper, the internal friction behaviors of unidirectionally solidified Al2O3/YAG eutectic that are examined by the authors in passed several years are reviewed. The internal friction of this eutectic increased with increasing temperatures above 1200oC. The apparent activation energy of the eutectic sample in the range from 1100 to 1400oC was same to that of Al2O3 single crystal. Above 1200oC, the internal friction of this material drastically increased with increasing temperatures. The magnitude of the internal friction strongly depended on the elevated temperatures and the cycle numbers of the torsional loading. For the 1400oC test, the internal friction gradually increased with the loading cycles and then saturated by 103 times of the loading cycles.

scholarly journals Kinetics Study of Acid Catalyzed Degradation of Glucose in High-Temperature Liquid Water

2020 ◽  
Vol 5 (2) ◽  
pp. 21
Author(s):  
Atiqa Rahmawati ◽  
Aulia Iin Saputri ◽  
Ignatius Gunardi
Keyword(s):  
Activation Energy ◽  
Sulfuric Acid ◽  
High Temperature ◽  
Acid Concentration ◽  
Liquid Water ◽  
Reduction Rate ◽  
Acid Catalyzed ◽  
Temperature Liquid ◽  
Kinetics Of ◽  
Time Of Reaction

Glucose is the most abundant monosaccharide in nature, glucose obtained from cellulose and starch, it is many used to degradation process, and for the production of several organic compounds, one of the degradation products of glucose is an HMF (5-hydroxymethylfurfural). HMF is a platform chemical, which can be converted into several chemical and liquid fuels through hydrogenation, oxidation, and esterification. The objective of this researches has studied the kinetics of glucose degradation using acid-catalyzed (H2SO4) in high-temperature liquid water and observe the effect of acid concentration and temperature on degradation of glucose to HMF. In this research was used reactor with pressure 10 atm, with variation time of reaction, sulfuric acid concentration, and temperature of the reaction. From this research found kinetics of glucose degradation was followed by the first-order reaction in each variable. Activation Energy (Ea) values were 7306,593 J/mol; 6341,59 J/mol; 3988,14 J/mol and 3988,14 J/mol on the concentration sulfuric acid 0,05M; 0,1 M; 0,05M, from that result indicated that reaction rate was increase when activation energy was decrease this was related to Arrhenius equation. The effect of acid concentration on degradation glucose was the higher acid concentration used, the more glucose was degraded, and more HMF was formed. Meanwhile, the effect of temperature of reaction on degradation glucose was the higher temperature of the reaction, more glucose was degraded, and more HMF was formed. The highest value of HMF was in operation condition of concentration H2SO4 0,5 M at 175°C, with a time of reaction 120 minutes. However, the reduction rate of glucose was not equal to the rate of formation of HMF (5-hydroxymethylfurfural), it can be indicated that HMF (5-hydroxymethylfurfural) was not the only product of degradation of glucose, but the others product might be formed from this operating condition. The other product that might be formed was humin and levulinic acid.

Apparent Activation Energy for High-Temperature Deformation of EN AW 2014

2009 ◽  
Vol 28 (5) ◽  
pp. 315-322 ◽  
Author(s):  
Jana Bidulská, ◽  
Imrich Pokorný, ◽  
Tibor Kvačkaj, ◽  
Róbert Bidulský, ◽  
Marco Actis Grande,
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
Apparent Activation Energy ◽  
High Temperature Deformation ◽  
Temperature Deformation

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

scholarly journals The Hydrothermal Stability and the Properties of Non- and Strongly-Interacting Rh Species over Rh/γ, θ-Al2O3 Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 99
Author(s):  
Guanghao Cheng ◽  
Gurong Shen ◽  
Jun Wang ◽  
Yunhao Wang ◽  
Weibo Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Aging Time ◽  
Reaction Path ◽  
Aging Treatment ◽  
Hydrothermal Stability ◽  
Hydrothermal Aging ◽  
Strongly Interacting

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh3+ and Rh4+, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (Eapp) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al2O3 and Rh/θ-Al2O3.

scholarly journals High-Temperature Deformation of Naturally Aged 7010 Aluminum Alloy

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 581
Author(s):  
Abdulhakim A. Almajid
Keyword(s):  
Activation Energy ◽  
Aluminum Alloy ◽  
High Temperature ◽  
Threshold Stress ◽  
Activation Energies ◽  
Temperature Deformation ◽  
High Temperature Range ◽  
Temperature Range ◽  
True Activation Energy ◽  
Two Temperatures

This study is focused on the deformation mechanism and behavior of naturally aged 7010 aluminum alloy at elevated temperatures. The specimens were naturally aged for 60 days to reach a saturated hardness state. High-temperature tensile tests for the naturally aged sample were conducted at different temperatures of 573, 623, 673, and 723 K at various strain rates ranging from 5 × 10−5 to 10−2 s−1. The dependency of stress on the strain rate showed a stress exponent, n, of ~6.5 for the low two temperatures and ~4.5 for the high two temperatures. The apparent activation energies of 290 and 165 kJ/mol are observed at the low, and high-temperature range, respectively. These values of activation energies are greater than those of solute/solvent self-diffusion. The stress exponents, n, and activation energy observed are rather high and this indicates the presence of threshold stress. This behavior occurred as a result of the dislocation interaction with the second phase particles that are existed in the alloy at the testing temperatures. The threshold stress decreases in an exponential manner as temperature increases. The true activation energy was computed by incorporating the threshold stress in the power-law relation between the stress and the strain. The magnitude of the true activation energy, Qt dropped to 234 and 102 kJ/mol at the low and high-temperature range, respectively. These values are close to that of diffusion of Zinc in Aluminum and diffusion of Magnesium in Aluminum, respectively. The Zener–Hollomon parameter for the alloy was developed as a function of effective stress. The data in each region (low and high-temperature region) coalescence in a segment line in each region.

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