Evolution of hardness and transmittance in irradiated LiF single crystals at elevated temperatures

1992 ◽  
Vol 7 (10) ◽  
pp. 2833-2839 ◽  
Author(s):  
Hung-Ye Lin ◽  
Yu-Zen Tsai ◽  
Sanboh Lee
Keyword(s):  
Activation Energy ◽  
Optical Absorption ◽  
Single Crystals ◽  
Vickers Hardness ◽  
Elevated Temperatures ◽  
Kinetic Process ◽  
Order Kinetic ◽  
First Order ◽  
Γ Rays ◽  
Two Stages

The evolution of hardness and transmittance of irradiated LiF single crystals at elevated temperatures has been investigated. The Vickers hardness is proportional to φ1/3 where φ is the dosage of γ-rays. The thermal annealing of hardness which is analyzed according to a first-order kinetic process has one stage for φ = 100 KGy and two stages for φ ≥ 250 KGy. For a given dosage, the activation energy of stage I is larger than that of stage II. The transmittance of irradiated LiF crystals is attributed to F, M, R1, and R2 centers. The transmittance decreases with increasing time at the brief durations, then oscillates, and finally increases monotonically. The region in which the transmittance increases monotonically with time is simulated by a second-order kinetic process of the color center. The activation energy of optical absorption was determined. Comparing both activation energies of hardness and optical absorption, we find that the mechanism of the kinetic process for hardness differs from that for optical absorption.

Regeneration of Adsorbent Carbonaceous Materials with Supercritical Water

2006 ◽  
Vol 514-516 ◽  
pp. 1742-1747 ◽  
Author(s):  
M.Jesus Sánchez-Montero ◽  
Francisco Salvador-Palacios ◽  
Aurelio Salvador Palacios ◽  
M.Jesus Martin Rodriguez
Keyword(s):  
Activation Energy ◽  
Activated Carbon ◽  
Adsorption Capacity ◽  
Supercritical Water ◽  
Kinetic Process ◽  
Regeneration Process ◽  
Order Kinetic ◽  
Carbonaceous Materials ◽  
First Order

The aim of this work was to study a new procedure for the regeneration of activated carbon saturated with phenol. The study was accomplished in two steps: extraction of the pollutant with supercritical water at 410 °C and 275 bar, and gasification of phenol with supercritical water at temperatures ranging between 600 - 650 °C. It was observed that the regeneration process was very rapid and effective. The regenerated activated carbon always recovered its original adsorption capacity, even after several regeneration cycles. The gasification of phenol afforded CO2 and H2O, with a very fast first-order kinetic process. The activation energy was very low (0.192 kJ mol-1).

APPLICATION OF CVD DIAMOND FILMS FOR UV THERMOLUMINESCENCE DOSIMETER

2002 ◽  
Vol 16 (06n07) ◽  
pp. 1003-1007 ◽  
Author(s):  
J. AHN ◽  
B. GAN ◽  
Q. ZHANG ◽  
S. F. YOON ◽  
V. LIGATCHEV ◽  
...  
Keyword(s):  
Activation Energy ◽  
Glow Curve ◽  
Diamond Films ◽  
Frequency Factor ◽  
Cvd Diamond ◽  
Order Kinetic ◽  
First Order ◽  
Order Kinetic Model ◽  
Ionizing Radiations ◽  
Trap Activation

This study presents the investigation of CVD diamond for the application of an UV TL dosimeter. A 9-μm-thick film used in this study presents a TL glow curve with a well-defined first-order kinetic peak (at about 273 K), which norm ally presents in the glow curve from ionizing radiations, is not observed. By fitting the glow curve to a first-order kinetic model, the trap activation energy E t = 0.95 eV and frequency factor s = 5.6 x 106 s -1 have been resolved.

Hydration of Partially Sulfated Lime Particles From Fluidized Bed Combustors

2000 ◽  
Vol 123 (2) ◽  
pp. 173-178 ◽  
Author(s):  
M. F. Couturier ◽  
Y. Volmerange ◽  
F. Steward
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Hydration Reaction ◽  
Order Kinetic ◽  
First Order ◽  
Thermogravimetric Analyzer ◽  
Order Kinetic Model ◽  
Increasing Temperature

The reaction between water and partially sulfated lime particles was studied under isothermal conditions using a microcalorimeter. Experiments were performed with spent sorbent particles from two industrial circulating fluidized bed combustors and with lime particles sulfated in the laboratory using a thermogravimetric analyzer. The rate of hydration of the partially sulfated lime particles was found to be independent of particle size, to increase with increasing temperature, and to decrease with increasing level of sulfation of the particles. A first-order kinetic model is shown to correlate well the effect of time and temperature on the extent of hydration of spent sorbent particles from fluidized bed combustors. The apparent activation energy of the hydration reaction is 45 kJ/mol.

Paramagnetische Resonanz von Mn++-Ionen in AgCl-Einkristallen

1962 ◽  
Vol 17 (2) ◽  
pp. 155-158 ◽  
Author(s):  
Jürgen Schneider ◽  
Subhas Ranjan Sircar
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Elevated Temperatures ◽  
Silver Chloride ◽  
Fixed Position ◽  
Paramagnetic Resonance ◽  
X Band ◽  
Wide Range

The paramagnetic resonance of manganese doped silver chloride single crystals has been observed at X-band frequencies over a wide range of temperature. At 77 °K the spectrum is that corresponding to a Mn++-ion associated with a nearest silver vacancy in a fixed position. At elevated temperatures, the angle dependent lines of the spectrum broaden out. due to the enhancement of jumping motion of the vacancies. From the temperature dependence of those lines, the activation energy for the motion of a silver vacancy bound to the Mn++-ion was found to be 0.30 ± 0.05 eV.

Kinetics Analysis of Wheat Straw Pulping Process

2013 ◽  
Vol 860-863 ◽  
pp. 1012-1016 ◽  
Author(s):  
Ming Xian Cui ◽  
Wei Song ◽  
Zong Yu Liu
Keyword(s):  
Activation Energy ◽  
Wheat Straw ◽  
Lignin Content ◽  
Removal Rate ◽  
Black Liquor ◽  
Alkali Concentration ◽  
Slow Stage ◽  
First Order ◽  
Lignin Removal ◽  
Two Stages

This paper analyzes the delignification mechanism of wheat straw pulping process. The lignin removal of pulping process is left in black liquor. The higher the black liquor lignin content is, the bigger the lignin of paper pulp is removed. The relations of black liquor lignin content and alkali concentration to pulping time are described in detail. The results show that delignification process is divided into two stages: quick and slow stage. The lignin removal rate in the first stage is much higher than the second, that is, lignin has been removed more sufficiently after quick stage. In first stage, reaction order of delignification is 1.0, and 0.7 with respect to OH-, the activation energy is 38.62 kJ • mol-1. The latter delignification also belongs to the first-order reaction and 4.4 with respect to OH-, the activation energy is 75.56 kJ • mol-1. Apparently, slow stage needs to consume large amounts of energy to removal lignin.

Vulcanization Kinetics of Natural Rubber Coagulated by Microorganisms with Use of a Vulcameter

2010 ◽  
Vol 160-162 ◽  
pp. 1181-1186 ◽  
Author(s):  
Zhi Feng Wang ◽  
Si Dong Li ◽  
Xiao Dong She
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Rate Constants ◽  
Order Reaction ◽  
First Order Reaction ◽  
First Order ◽  
Second Stage ◽  
End Stage ◽  
Two Stages ◽  
Kinetics Of

Kinetics of vulcanization of natural rubber coagulated by microorganisms (NR-m) was studied with the use of a vulcameter. In the induction period of vulcanization, the time t0 of NR-m is shorter than that of natural rubber coagulated by acid (NR-a), and the rate constant k1/a of NR-m are greater than that of NR-a. Both the curing periods of NR-m and NR-a consist of two stages. The first stage follows first-order reaction. The rate constants k2 of NR-m in the first stage are greater than that of NR-a at the same temperature, and so are the activation energy E2. The second stage (end stage of the curing period) does not follow first-order reaction, and the calculated reaction order n of NR-m is in the range of 0.82-0.85, and that of NR-a is in the range of 0.64-0.72. The rate constants k3 of the second stage for NR -m are greater than that of NR-a at the same temperature, and so is the activation energy E3.

scholarly journals Study on the Pyrolysis Kinetics and Mechanisms of the Tread Compounds of Silica-Filled Discarded Car Tires

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 810
Author(s):  
Chuansheng Wang ◽  
Baishun Zhao ◽  
Xiaolong Tian ◽  
Kongshuo Wang ◽  
Zhongke Tian ◽  
...  
Keyword(s):  
Activation Energy ◽  
Kinetic Equation ◽  
Research Method ◽  
Elevated Temperatures ◽  
Pyrolysis Process ◽  
Pyrolysis Kinetics ◽  
Exponential Factor ◽  
Theoretical Support ◽  
Two Stages ◽  
Research Analysis

The disposal of used automobile tires is a major waste concern. Simply stacking tires and allowing them to decompose will harbor breeding mosquitoes that spread viruses, whereas burning them will release acidic and toxic gases. Therefore, one viable option is pyrolysis, where elevated temperatures are used to facilitate the decomposition of a material. However, the lack of theoretical support for pyrolysis technology limits the development of the pyrolysis industry when it comes to discarded tires. The purpose of this research is to put forward a brand-new multi-kinetic research method for studying materials with complex components through the discussion of various kinetic research methods. The characteristic of this kinetic research method is that it is a relatively complete theoretical system and can accurately calculate the three kinetic factors considered during the pyrolysis of multicomponent materials. The results show that the multi-kinetic research method can obtain the kinetic equation and reaction mechanism for the pyrolysis of tires with high accuracy. The pyrolysis process of this compound was divided into two stages, Reaction I and II, where the kinetic equation of Reaction I was f ( α ) = 0.2473 α − 3.0473 , with an activation energy of 155.26 kJ/mol and a pre-exponential factor of 5.88 × 109/min. Meanwhile, the kinetic equation of Reaction II was f ( α ) = 0.4142 ( 1 − α ) [ − ln ( 1 − α ) ] − 1.4143 , while its activation energy was 315.40 kJ/mol and its pre-exponential factor was 7.86 × 1017/min. Furthermore, based on the results of the research analysis, the reaction principles corresponding to Reaction I and Reaction II in the pyrolysis process of this compound were established.

scholarly journals Thermal Degradation Kinetics and pH-Rate Profiles of Iriflophenone 3,5-C-β-d-diglucoside, Iriflophenone 3-C-β-d-Glucoside and Mangiferin in Aquilaria crassna Leaf Extract

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 4898
Author(s):  
Eakkaluk Wongwad ◽  
Kornkanok Ingkaninan ◽  
Wudtichai Wisuitiprot ◽  
Boonchoo Sritularak ◽  
Neti Waranuch
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Shelf Life ◽  
Leaf Extract ◽  
Degradation Kinetics ◽  
Order Reaction ◽  
Thermal Degradation Kinetics ◽  
Order Kinetic ◽  
First Order ◽  
Aquilaria Crassna

The health benefits of the Aquilaria crassna Pierre ex Lecomte leaf extract (AE) make it very useful as an ingredient in food and pharmaceutical products. Iriflophenone 3,5-C-β-d-diglucoside (1), iriflophenone 3-C-β-d-glucoside (2) and mangiferin (3) are bioactive compounds of AE. We assessed the stability of AE by investigating the thermal degradation kinetics and shelf-life (t90%) of compounds 1, 2 and 3 using Arrhenius plot models and studied their pH-rate profiles. The results demonstrate that 1 and 2 were degraded, following a first-order kinetic reaction. The degradation of 3 followed first-order reaction kinetics when present in a solution and second-order reaction kinetics in the dried powder form of the extract. According to the first-order kinetic model, the predicted shelf-life (t90%) of the extract at 25 °C in dried form for compound 1 was 989 days with activation energy 129.86 kJ·mol−1, and for 2 it was 248 days with activation energy 110.57 kJ·mol−1, while in the extract solution, the predicted shelf-life of compounds 1–3 was 189, 13 and 75 days with activation energies 86.83, 51.49 and 65.28 kJ·mol−1, respectively. In addition, the pH-rate profiles of 1–3 indicated that they were stable in neutral to acidic environments.

Leaching Kinetics of Atrazine and Inorganic Chemicals in Tilled and Orchard Soils

2014 ◽  
Vol 28 (2) ◽  
pp. 231-237 ◽  
Author(s):  
Lech W. Szajdak ◽  
Jerzy Lipiec ◽  
Anna Siczek ◽  
Artur Nosalewicz ◽  
Urszula Majewska
Keyword(s):  
Reaction Rate ◽  
Inorganic Compounds ◽  
Model Performance ◽  
Order Reaction ◽  
First Order Reaction ◽  
Order Kinetic ◽  
Time Data ◽  
First Order ◽  
Concentration Changes ◽  
Reaction Constants

Abstract The aim of this study was to verify first-order kinetic reaction rate model performance in predicting of leaching of atrazine and inorganic compounds (K+1, Fe+3, Mg+2, Mn+2, NH4 +, NO3 - and PO4 -3) from tilled and orchard silty loam soils. This model provided an excellent fit to the experimental concentration changes of the compounds vs. time data during leaching. Calculated values of the first-order reaction rate constants for the changes of all chemicals were from 3.8 to 19.0 times higher in orchard than in tilled soil. Higher first-order reaction constants for orchard than tilled soil correspond with both higher total porosity and contribution of biological pores in the former. The first order reaction constants for the leaching of chemical compounds enables prediction of the actual compound concentration and the interactions between compound and soil as affected by management system. The study demonstrates the effectiveness of simultaneous chemical and physical analyses as a tool for the understanding of leaching in variously managed soils.

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