scholarly journals Kinetic study on the grain growth of PuO2 nanocrystals

RSC Advances ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 6542-6547 ◽  
Author(s):  
Daniel Bouëxière ◽  
Karin Popa ◽  
Olaf Walter ◽  
Marco Cologna
Keyword(s):  
Activation Energy ◽  
Kinetic Study ◽  
Grain Growth ◽  
Particle Growth ◽  
Temperature Range ◽  
Micrometer Scale ◽  
Kinetics Of

Results on the kinetics of PuO2 nanocrystals are presented in the temperature range below 1100 °C showing the activation energy for the particle growth is ∼350 kJ mol−1. Particle growth proceeds from the nano- to the micrometer scale.

scholarly journals KINETIKA REAKSI SINTHESIS BIOMATERIAL HIDROXYAPATITE DENGAN JENIS PREKURSOR NITRAT DAN ASETAT

REAKTOR ◽  
2014 ◽  
Vol 15 (2) ◽  
pp. 104 ◽  
Author(s):  
Adhi Setiawan ◽  
W Widiyastuti ◽  
Sugeng Winardi ◽  
Agung Nugroho
Keyword(s):  
Activation Energy ◽  
Kinetic Model ◽  
Kinetic Study ◽  
Reaction Kinetics ◽  
Grain Growth ◽  
High Purity ◽  
Growth Kinetic ◽  
The Body ◽  
Nitrate Precursor ◽  
Kinetics Of

Hidroxyapatite (HAp) merupakan salah satu biomaterial yang banyak diaplikasikan dalam dunia medis untuk membuat implant jaringan tubuh terutama tulang dan gigi sehingga kemurnian produk HAp memegang peranan yang cukup penting. Agar diperoleh HAp dengan kemurnian tinggi, kinetika reaksi pembentukan HAp harus diketahui secara jelas. Metode yang digunakan untuk memperoleh kinetika reaksi HAp adalah dengan analisis TG-DTA  yang dilakukan pada dua jenis prekursor HAp yaitu asetat dan nitrat. Metode TG-DTA tersebut dilakukan dengan memanaskan prekursor HAp dengan variasi laju pemanasan 10, 15, 17, dan 20 oC/menit. Hasil analisis TG-DTA menunjukkan bahwa reaksi dekomposisi prekursor asetat dan nitrat membentuk HAp masing-masing terjadi pada suhu 659 oC dan 560 oC. Hasil fitting parameter kinetika menunjukkan bahwa energi aktivasi pembentukan HAp pada prekursor asetat sebesar 161,56 kJ/mol  dengan model kinetika Normal Grain Growth sedangkan pada prekursor nitrat sebesar 374 kJ/mol dengan model kinetika Johnson-Mehl-Avrami. Kata kunci: Biomaterial, hidroxypapatite, Dekomposisi, Energi Aktivasi ABSTRACT KINETIC STUDY OF THE BIOMATERIAS HIDOXYAPATITE SINTHESIS WITH PRECURSOR NITRATE AND  ACETATE. Hidroxyapatite (HAp) is one of the biomaterials widely applied in the medical world to make implant tissues of the body, especially bones and teeth so that the purity of the HAp plays a fairly important. In order to obtain high purity HAp, reaction kinetics should be known clearly. TG-DTA  is method used to obtain the reaction kinetics of HAp.TG-DTA analyzes were conducted on precursors acetate and nitrate. TG-DTA method is carried out by heating HAp precursor with variation heating rate 10, 15, 17, and 20° C/min respectively. The results of TG-DTA  showed decomposition precursor acetate and nitrate formed HAp occurs on temperature 659° C and 560° C respectively. The results of the fitting kinetic showed activation energy of  the HAp formation on acetate precursors about 161.56 kJ/mol with Normal Grain Growth kinetic model whereas the nitrate precursor about 374 kJ/mol with Johnson-Mehl-Avrami  kinetic model.

Diffusion Mechanisms in Nanocrystalline and Nanolaminated Au-Cu

2007 ◽  
Vol 266 ◽  
pp. 13-28 ◽  
Author(s):  
Alan F. Jankowski
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Diffusion ◽  
Bulk Diffusion ◽  
Grain Boundary Diffusion ◽  
Dominant Mechanism ◽  
Temperature Range ◽  
Diffusion Mechanisms ◽  
Kinetics Of

Thermal anneal treatments are used to identify the temperature range of the two dominant diffusion mechanisms – bulk and grain boundary. To assess the transition between mechanisms, the low temperature range for bulk diffusion is established utilizing the decay of static concentration waves in composition-modulated nanolaminates. These multilayered structures are synthesized using vapor deposition methods as thermal evaporation and magnetron sputtering. However, at low temperature the kinetics of grain-boundary diffusion are much faster than bulk diffusion. The synthesis of Au-Cu alloys (0-20 wt.% Cu) with grain sizes as small as 5 nm is accomplished using pulsed electro-deposition. Since the nanocrystalline grain structure is thermally unstable, these structures are ideal for measuring the kinetics of grain boundary diffusion as measured by coarsening of grain size with low temperature anneal treatments. A transition in the dominant mechanism for grain growth from grain boundary to bulk diffusion is found with an increase in temperature. The activation energy for bulk diffusion is found to be 1.8 eV·atom-1 whereas that for grain growth at low temperatures is only 0.2 eV·atom-1. The temperature for transitioning from the dominant mechanism of grain boundary to bulk diffusion is found to be 57% of the alloy melt temperature and is dependent on composition.

Diffusion kinetics of gold in TiO2 nanotube arrays for formation of Au@TiO2 nanotube arrays

RSC Advances ◽  
2016 ◽  
Vol 6 (54) ◽  
pp. 48580-48588 ◽  
Author(s):  
Wanggang Zhang ◽  
Yiming Liu ◽  
Diaoyu Zhou ◽  
Jing Wen ◽  
Liuwei Zheng ◽  
...  
Keyword(s):  
Activation Energy ◽  
Tio2 Nanotube Arrays ◽  
Tio2 Nanotube ◽  
Nanotube Arrays ◽  
Diffusion Kinetics ◽  
Temperature Range ◽  
Heating Treatment ◽  
Kinetics Of

Heating treatment leads to the diffusion of Au into TiO2 nanotube arrays and the formation of Au nanocrystals. The activation energy for the Au diffusion on the surface of the TiO2 nanotubes in the temperature range of 400 to 500 °C is 67.2 kJ mol−1.

β Grain Growth Kinetics of Hot-Rolled TB-13 Alloy

2011 ◽  
Vol 689 ◽  
pp. 472-478 ◽  
Author(s):  
Yue Fei ◽  
Bin Tang ◽  
Hui Chang ◽  
Zhi Shou Zhu ◽  
Zhong Bo Zhou ◽  
...  
Keyword(s):  
Activation Energy ◽  
Grain Growth ◽  
Kinetic Equations ◽  
Type Equation ◽  
Growth Exponent ◽  
Fine Grained ◽  
Solution Treated ◽  
Grain Growth Kinetics ◽  
Hot Rolled ◽  
Kinetics Of

A study on the kinetics of β grain growth of a fine-grained, hot-rolled TB-13 alloy was carried out by isochronal and isothermal solution treatments. The grain size of the as-rolled and as-solution-treated samples was determined by metallographic observation using the linear intercept method. The kinetic equations and the Arrhenius-type equation were applied to calculate the β grain growth exponent and the activation energy for β grain growth at special temperatures. The results showed that the β grain growth rate decreased with elongating solution treated time, but increased with increasing solution treated temperature. The β grain growth exponents (n) were 0.394, 0.403 and 0.406 during the solution treated temperatures at 1103K, 1153K and 1203K, respectively. The values of n increased with increasing solution treated temperature and the determined activation energy (Qm) for β grain growth after holding for 0.5h at 1103K-1203K was around 156KJ/mol.

scholarly journals Pyrolytic characteristics and kinetics of Guanzhong wheat straw and its components for high-value products

BioResources ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. 1958-1979
Author(s):  
Bingtao Hu ◽  
Zhaolin Gu ◽  
Junwei Su ◽  
Zhijian Li
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Wheat Straw ◽  
Pyrolysis Products ◽  
Transportation Fuels ◽  
Temperature Range ◽  
Model Free ◽  
System A ◽  
Gas Products ◽  
Kinetics Of

Wheat straw produced annually in the Shaanxi Guanzhong region is a potential biomass feedstock for the production of transportation fuels and specialized chemicals through combustion, pyrolysis, or gasification. In this work, the pyrolytic characteristics, evolved gas products, and kinetics of Guanzhong wheat straw and its components were first investigated with a thermogravimetry-Fourier infrared spectroscopy (TG-FTIR) system. A comparative kinetic study was conducted using different model-free methods of Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Kissinger, and the Coats-Redfern methods. The main pyrolysis products identified by FTIR include H2O, CH4, CO2, and CO as well as aromatics, acids, ketones, and aldehydes. Kinetic results showed that the pyrolytic apparent activation energy of the straw is approximately 200 kJ/mol obtained via FWO and KAS methods at the conversion range of 0.4 to 0.75, which was 30 kJ/mol higher than the value 171.1 kJ/mol obtained by the Kissinger method. The apparent activation energy of cellulose in its main pyrolysis region is 135.5 kJ/mol and is about three times larger than that of hemicellulose (49.5 kJ/mol). The apparent activation energy of lignin at the temperature range of 45 to 116 °C was 34.5 kJ/mol, while that value at the temperature range of 120 to 252 °C was 6.64 kJ/mol.

scholarly journals A combined high-temperature experimental and theoretical kinetic study of the reaction of dimethyl carbonate with OH radicals

2017 ◽  
Vol 19 (10) ◽  
pp. 7147-7157 ◽  
Author(s):  
Fethi Khaled ◽  
Binod Raj Giri ◽  
Milán Szőri ◽  
Tam V.-T. Mai ◽  
Lam K. Huynh ◽  
...  
Keyword(s):  
High Temperature ◽  
Shock Waves ◽  
Kinetic Study ◽  
Reaction Kinetics ◽  
Dimethyl Carbonate ◽  
Oh Radicals ◽  
Temperature Range ◽  
Reflected Shock ◽  
Kinetics Of

The reaction kinetics of dimethyl carbonate (DMC) and OH radicals were investigated behind reflected shock waves over the temperature range of 872–1295 K and at pressures near 1.5 atm.

THE KINETICS OF THE REACTION OF ACTIVE NITROGEN WITH ETHYLENE

1962 ◽  
Vol 40 (4) ◽  
pp. 686-691 ◽  
Author(s):  
E. M. Levy ◽  
C. A. Winkler
Keyword(s):  
Nitric Oxide ◽  
Activation Energy ◽  
Low Temperature ◽  
Copper Oxide ◽  
Cobalt Catalyst ◽  
Cobalt Catalysts ◽  
Active Nitrogen ◽  
Temperature Range ◽  
P Factor ◽  
Kinetics Of

A comparison has been made of five methods for terminating the reaction of active nitrogen with ethylene in the temperature range 295° to 673° K. These were based on deactivating the active nitrogen by low-temperature trapping, by addition of nitric oxide, and by passing it over copper oxide or cobalt catalysts. With the nitric oxide and cobalt catalyst techniques, which appeared to be the most reliable of those used, an activation energy of 400 ± 200 cal/mole, with a P factor of about 10−5, have been determined for the reaction.

KINETICS OF THE CUPRIC ACETATE CATALYZED HYDROGENATION OF DICHROMATE IN AQUEOUS SOLUTION

1955 ◽  
Vol 33 (2) ◽  
pp. 356-364 ◽  
Author(s):  
E. Peters ◽  
J. Halpern
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Partial Pressure ◽  
Kinetic Study ◽  
Reaction Rates ◽  
Homogeneous Catalyst ◽  
Cupric Acetate ◽  
Partial Pressures ◽  
Kinetics Of

In aqueous solution, cupric acetate was found to act as a homogeneous catalyst for the reduction of dichromate by hydrogen, i.e.[Formula: see text] The paper describes a kinetic study of this reaction. Rates were determined at temperatures between 80° and 140 °C. and hydrogen partial pressures up to 27 atmospheres. The rate is independent of the dichromate concentration but varies directly with the partial pressure of hydrogen and is nearly proportional to the concentration of cupric acetate. The activation energy is 24,600 calories per mole. Cupric acetate, apparently acting as a true catalyst, activates the hydrogen through formation of a complex with it. An extension of the mechanism proposed earlier for the reaction of cupric acetate itself with hydrogen also accounts for the kinetics of the dichromate reaction.

Kinetics of the Reaction between Silver and Nitric Acid

1962 ◽  
Vol 15 (2) ◽  
pp. 181 ◽  
Author(s):  
JJ Batten
Keyword(s):  
Activation Energy ◽  
Nitric Acid ◽  
Induction Period ◽  
Acid Concentration ◽  
Maximum Rate ◽  
Kcal Mole ◽  
Temperature Range ◽  
Induction Rate ◽  
Rate Of Dissolution ◽  
Kinetics Of

The rate of dissolution of silver gauze in nitric acid at various concentrations and temperatures was measured in a static system. The solution process was measured by the weight of silver dissolved in various time intervals. In general, induction periods were observed, but after this period the dissolution proceeded with an appreciable velocity. To examine the influence of acid concentration and temperature on the kinetics of the reaction, the duration of the induction period, the rate of dissolution during this period, and the subsequent maximum rate were taken as kinetic parameters of the reaction. The induction rate was found to be highly dependent on the initial acid concentration (approx. seventh power), whereas over most of the concentration range accessible to study, the maximum rate was proportional to the square of the concentration. It was also observed that increase in temperature sharply increases the induction rate, but has little effect upon the subsequent maximum rate over most of the temperature range studied. The activation energy of the induction rate was greater than 20 kcal/mole, whereas that of the maximum rate was about 4 kcal/mole over most of the temperature range studied. This difference in the activation energy during and after the induction period is explained by a shift in the mechanism controlling the rate of the process from a chemical reaction at the surface to a diffusion process.

Determination of Recrystallization Kinetics and Activation Energy of Grain Growth Process of Cu-14Al-4Ni Shape Memory Alloy

2015 ◽  
Vol 1765 ◽  
pp. 127-132 ◽  
Author(s):  
Emmanuel P. R. Lima ◽  
Pedro C. de Lima ◽  
Marcelo Nava
Keyword(s):  
Activation Energy ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Grain Growth ◽  
Growth Process ◽  
Treatment Time ◽  
Mechanical Tests ◽  
A Value ◽  
Kinetics Of

ABSTRACTThe non-ferrous shape memory alloys have, normally, two problems that hinder its use in industrial scale: the natural aging and grains growth. The first degrades the memory effect, while the second, observed during the processing of alloy, modifies the temperatures which the transformations occur. Thus, the study of kynetic of recrystallization is important for enabling the control of hardened state in function of treatment time, without causing excessive grain growth. Therefore, the objective of this study is to determine the kinetics of recrystallization of Cu-14Al-4Ni shape memory alloy, based on an empirical law of the formation of Jonhson-Mehl-Avrami, as well as their activation energies for grain growth process according to the empirical Arrhenius law. The alloy was vacuum melted in an induction furnace. After casting, the bulk samples of the alloy were homogenized for 24 hours, solubilized and hot rolled followed by water-quenching to initiate the recrystallization. Then, different samples were annealed at temperatures close to the peak, start and end of the DSC curve. Following the heat treatments, the samples were submitted to mechanical tests and the values of the properties were correlated to the fraction transformed for determination of recrystallization’s kinetic. For the characterization of the grain growth process, analyses in optical microscopy were accomplished and all annealed samples were examined by statistical metallography and the grain sizes were measured. After measurements, the ln[-ln(1-Yrec)] x ln(t) and the ln [D-Do] x 1/T diagrams were plotted to determine the parameters of Jonhson-Mehl-Avrami equation and the activation energy of the process, respectively. The results showed that the equation of the recrystallized fraction follows the empiric law of the formation of Jonhson-Mehl-Avrami for the considered property, as well as, also showed that the alloy Cu-14Al-4Ni is extremely sensitive to temperature variation in which the alloy is treated, having a dual kinetics of grain growth. In the first domain, between 670 and 710°C, the diagram provides a value for the activation energy equal to 39.32 KJ/mol, in the second domain, between 710 and 790°C, the diagram provides a value for the activation energy equal to 9.01 KJ/mol.

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