Kinetic Study on Phosphate Enrichment Behavior in CaO–SiO2–FeO–Fe2O3–P2O5 Steelmaking Slags

2018 ◽  
Vol 37 (5) ◽  
pp. 477-486
Author(s):  
Jin-yan Li ◽  
Mei Zhang ◽  
Min Guo ◽  
Xue-min Yang
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Crystallization Behavior ◽  
Crystallization Rate ◽  
Avrami Equation ◽  
One Dimensional ◽  
Thermal Crystallization ◽  
Steelmaking Slags ◽  
Cooling Schedules ◽  
Kinetics Of

AbstractThe iso-thermal crystallization behavior of phosphate-enriched phase has been experimentally investigated in the rapidly quenched CaO–SiO2–FeO–Fe2O3–P2O5 steelmaking slags under different cooling schedules. The experimental results indicate that increasing endpoint temperature from 1453 to 1533 K and prolonging holding time from 2 to 60 min can result in an increasing tendency of the size of phosphate-enriched phase in the shape of one-dimensional rod. The crystallization kinetics of phosphate-enriched phase in steelmaking slags has been described by Avrami equation. The Avrami constant $$n$$ was obtained to be 0.472, while the crystallization rate constant $$k$$ was recommended as $$\ln k{\rm{= 57}}{\rm{. 40 + 12,273}}{\rm{. 96}}/T - {\rm{8}}{\rm{. 25}}\,\ln T - {\rm{5}}{\rm{. 5}\times{\rm 10}^{- 3}}T$$. Thus, the apparent activation energy $$E$$ of crystallization is recommended as $$E{\rm{= 537}}{\rm{. 60}} - {\rm{206}}{\rm{. 015}}T$$ kJ/mol.

Functionalization of Multiwalled Carbon Nanotubes by Poly (Ethlylene Glycol) and Non-Isothermal Crystallization Kinetic Study

2011 ◽  
Vol 688 ◽  
pp. 127-134
Author(s):  
Song Gao ◽  
Kun Yan Sui ◽  
Zhi Ming Wu ◽  
Wen Wen Wu ◽  
Yan Zhi Xia
Keyword(s):  
Carbon Nanotubes ◽  
Crystallization Behavior ◽  
Crystallization Kinetic ◽  
Crystallization Rate ◽  
Avrami Equation ◽  
Nonisothermal Crystallization ◽  
Multiwalled Carbon ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
Kinetics Of

Multi-walled carbon nanotubes (MWNT) were successfully chemically modified (MWNT-COOH) and reacted with polyethylene glycol (PEG) to prepare nanocomposites. As- prepared kinds of functionalized MWNT (MWNT-g-PEG) were characterized with FTIR, TGA and TEM. Nonisothermal crystallization kinetics of MWNT-g-PEG composites was investigated by differential scanning calorimeter (DSC). The kinetics was analyzed using the Ozawa and Avrami equation modified by Jeziorny. The results showed that the Ozawa approach failed to describe the crystallization behavior of nanocomposites, whereas the modified Avrami analysis could explain the behavior of MWNT-g-PEG nanocomposite only. It is observed that the presence of MWNT hindered the mobility of PEG chains and decreased the overall crystallization rate. It was found that the crystallization behavior of MWNT-g-PEG nanocomposite was strongly affected by the incorporation of MWNT. The data for the nonisothermal crystallization could be analyzed properly by the Avrami equation modified by Jeziorny. The results showed that the presence of MWNT decreased the overall nonisothermal crystallization rate of the PEG chains which were grafted onto the MWNT due to MWNT might act as physical hindrances retarding the mobility of PEG chains and decreased the crystallinity.

scholarly journals Analysis of the rheological property and crystallization behavior of polylactic acid (Ingeo™ Biopolymer 4032D) at different process temperatures

e-Polymers ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 702-709
Author(s):  
Hyeong Min Yoo ◽  
Su-Yeon Jeong ◽  
Sung-Woong Choi
Keyword(s):  
Rheological Property ◽  
Polylactic Acid ◽  
Crystallization Kinetics ◽  
Crystallization Behavior ◽  
Crystallization Rate ◽  
Avrami Equation ◽  
Scanning Calorimetry ◽  
Isothermal Crystallization Kinetics ◽  
Shear Rates ◽  
Kinetics Of

Abstract The aim of this study was to determine the rheological property and crystallization behavior of polylactic acid (PLA) with improved heat resistance (Ingeo™ Biopolymer 4032D) through investigation of the melt viscosity and crystallization kinetics of PLA at different process temperatures. The viscosity was measured using a rotational rheometer under conditions of shear rates of 0.01, 0.1, and 1/s. The obtained rheological data show that the viscosity tended to decrease slightly as the shear rate increases and decrease sharply as the temperature increases from 180°C to 210°C. To investigate the effect of the process temperature on the crystallization kinetics and final crystallinity of PLA, thermal analysis using isothermal differential scanning calorimetry (DSC) were also performed. The Avrami equation was successfully applied for the isothermal crystallization kinetics model. From crystallization temperature of 85°C to 120°C, we found that the Ingeo™ Biopolymer 4032D PLA had the fastest crystallization rate (t 1/2: 26.0 min) and the largest crystallinity (47.4%) at 100°C.

Kinetics of crystallization for polypropylene/polyethylene/halloysite nanotube nanocomposites

2018 ◽  
Vol 33 (4) ◽  
pp. 451-463 ◽  
Author(s):  
MY Ong ◽  
WS Chow
Keyword(s):  
Crystallization Rate ◽  
Avrami Equation ◽  
Crystallization Time ◽  
Halloysite Nanotube ◽  
Kissinger Equation ◽  
Polyethylene Blends ◽  
Instantaneous Nucleation ◽  
Half Crystallization Time ◽  
T Values ◽  
Kinetics Of

The aim of this study is to investigate the kinetics of non-isothermal crystallization of polypropylene/high-density polyethylene/halloysite nanotube (PP/HDPE/HNT) nanocomposites using three methods, that is, Avrami equation, combined Ozawa–Avrami method (hereafter called Mo model), and Kissinger equation. The Avrami exponent ( n) is in the range of 1–2 for all the PP/HDPE/HNT nanocomposites indicating instantaneous nucleation while the crystallization rate constant ( Zt) values of PP/HDPE increased with the addition of HNT. This proved that addition of HNT increases the crystallization rate. The reduction of half crystallization time ( t 1/2) for PP/HDPE as the increasing HNT loading indicates faster crystallization rate. In the Mo model, the cooling rate chosen at unit crystallization time F( T) values for PP/HDPE decreases with the addition of HNT. Kissinger equation showed that the activation energy ( E a) of crystallization for the PP/HDPE decreases with the addition of HNT. All the results demonstrated that HNT can accelerate the crystallization rate for the PP/polyethylene blends.

scholarly journals Influence of dimensionality on phase transition in VO2 nanocrystals

2013 ◽  
Vol 45 (3) ◽  
pp. 305-311 ◽  
Author(s):  
V.A. Blagojevic ◽  
N. Obradovic ◽  
N. Cvjeticanin ◽  
D.M. Minic
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Transition Temperature ◽  
Apparent Activation Energy ◽  
Phase Transition Temperature ◽  
Bulk Material ◽  
Two Dimensional ◽  
Lower Phase ◽  
One Dimensional ◽  
Simultaneous Movement

Hydrothermally synthesized one-dimensional and two-dimensional nanocrystals of VO2 undergo phase transition around 65?C, where temperature and mechanism of phase transition are dependent on dimensionality of nanocrystals. Both nanocrystalline samples exhibit depression of phase transition temperature compared to the bulk material, the magnitude of which depends on the dimensionality of the nanocrystal. One-dimensional nanoribbons exhibit lower phase transition temperature and higher values of apparent activation energy than two-dimensional nanosheets. The phase transition exhibits as a complex process with somewhat lower value of enthalpy than the phase transition in the bulk, probably due to higher proportion of surface atoms in the nanocrystals. High values of apparent activation energy indicate that individual steps of the phase transition involve simultaneous movement of large groups of atoms, as expected for single-domain nanocrystalline materials.

Crystallization and Melting Behaviors of Polylactic Acid/Thermoplastic Polyurethane Blends

2012 ◽  
Vol 627 ◽  
pp. 156-159 ◽  
Author(s):  
Tien Wei Shyr ◽  
Jung Yang ◽  
Chun Chieh Hu ◽  
Jian Ren Wang ◽  
Chia Hsin Tung
Keyword(s):  
Polylactic Acid ◽  
Thermoplastic Polyurethane ◽  
Crosslinking Agent ◽  
Crystallization Rate ◽  
Optical Microscope ◽  
Avrami Equation ◽  
Isothermal Crystallization Kinetics ◽  
X Ray ◽  
Structure Morphology ◽  
Kinetics Of

A series of blends were prepared by different ratios of polylactic acid (PLA) and thermoplastic polyurethane (TPU) with a crosslinking agent of dicumyl peroxide (DCP). This study focused on the crystal structure, morphology, crystallization, and melting behaviors of PLA/TPU blends using a wide angle x-ray diffractometer (WAXD), a polarizing optical microscope (POM) and a differential scanning calorimeter (DSC). A Modified Avrami equation was applied to analyze non-isothermal crystallization kinetics of PLA/TPU blends. Results show that the nucleation of PLA was enhanced by the added TPU. The spherulitic growth rate, crystallization rate, and crystallinity of the PLA/TPU blends increased with an increase of TPU content. WAXD results show that all of the crystal reflections of PLA/TPU blends related to those of PLA.

THE KINETICS OF CUPRENE GROWTH

1950 ◽  
Vol 28b (7) ◽  
pp. 358-372
Author(s):  
Cyrias Ouellet ◽  
Adrien E. Léger
Keyword(s):  
Nitric Oxide ◽  
Activation Energy ◽  
Carbon Monoxide ◽  
Apparent Activation Energy ◽  
Copper Catalyst ◽  
Maximum Velocity ◽  
Static System ◽  
Reaction Velocity ◽  
First Order ◽  
Kinetics Of

The kinetics of the polymerization of acetylene to cuprene on a copper catalyst between 200° and 300 °C. have been studied manometrically in a static system. The maximum velocity of the autocatalytic reaction shows a first-order dependence upon acetylene pressure. The reaction is retarded in the presence of small amounts of oxygen but accelerated by preoxidation of the catalyst. The apparent activation energy, of about 10 kcal. per mole for cuprene growth between 210° and 280 °C., changes to about 40 kcal. per mole above 280 °C. at which temperature a second reaction seems to set in. Hydrogen, carbon monoxide, or nitric oxide has no effect on the reaction velocity. Series of five successive seedings have been obtained with cuprene originally grown on cuprite, and show an effect of aging of the cuprene.

scholarly journals Kinetics of carbothermic reduction of synthetic chromite

2014 ◽  
Vol 50 (1) ◽  
pp. 15-21 ◽  
Author(s):  
Y. Wang ◽  
L. Wang ◽  
J. Yu ◽  
K.C. Chou
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Reduction Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Chromite Ore ◽  
Current Reduction ◽  
Increasing Temperature ◽  
Isothermal Mode ◽  
Kinetics Of

In order to optimize the current reduction process of chromite, a good knowledge of reduction mechanism involved is required. The basic component in chromite ore is FeCr2O4, thus, kinetic investigation of synthetic FeCr2O4 with different amount of carbon were carried out in the temperature range of 1473K to 1673K under both isothermal and non-isothermal mode. The iron can be easily reduced compared with chromium. And higher reduction degree of chromite can be achieved by increasing temperature and carbon content. With the supporting of X-ray Diffraction and Scanning Electron Microscope methods, the formation of metallic products followed the sequence: Fe-C alloy, (Fe,Cr)7C3and Fe-Cr-C alloy. Kinetics analysis showed that the first stage was controlled by nucleation with an apparent activation energy of 120kJ/mol, while the chromium reduction was controlled by crystallochemical transformation with an apparent activation energy of 288kJ/mol.

Kinetics of the addition of acids to olefins with and without boron fluoride catalysis

1967 ◽  
Vol 45 (1) ◽  
pp. 11-16 ◽  
Author(s):  
G. A. Latrèmouille ◽  
A. M. Eastham
Keyword(s):  
Activation Energy ◽  
Acetic Acid ◽  
Apparent Activation Energy ◽  
Trifluoroacetic Acid ◽  
Similar Rate ◽  
Ethylene Dichloride ◽  
Kcal Mole ◽  
Rate Law ◽  
Boron Fluoride ◽  
Kinetics Of

Isobutene reacts readily with excess trifluoroacetic acid in ethylene dichloride solution at ordinary temperatures to give t-butyl trifluoroacetate. The rate of the reaction is given, within the range of the experiments, by the expression d[ester]/dt = k[acid]2[olefin], and the apparent activation energy is about 6 kcal/mole. The rate of addition is markedly dependent on the strength of the reacting acid and is drastically reduced in the presence of mildly basic materials, such as dioxane. The boron fluoride catalyzed addition of acetic acid to 2-butene can be considered to follow a similar rate law, i.e. d[ester]/dt = k[acid·BF3]2[olefin], but only if some assumptions are made about the position of the equilibrium [Formula: see text]since only the 1:1 complex is reactive.

Characteristics and thermal decomposition kinetics of wood-SiO2 composites derived by the sol-gel process

Holzforschung ◽  
2017 ◽  
Vol 71 (3) ◽  
pp. 233-240 ◽  
Author(s):  
Ke-Chang Hung ◽  
Jyh-Horng Wu
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Apparent Activation Energy ◽  
Sol Gel ◽  
Weight Percent Gain ◽  
Weight Percent ◽  
Decomposition Kinetics ◽  
Thermal Decomposition Kinetics ◽  
Sol Gel Process ◽  
Kinetics Of

Abstract Wood-SiO2 composites (WSiO2Cs) were prepared by means of the sol-gel process with methyltrimethoxysilane (MTMOS) as a reagent, and the physical properties, structure and thermal decomposition kinetics of the composites has been evaluated. The dimensional stability of the WSiO2Cs was better than that of unmodified wood, especially in terms of the weight percent gain (WPG), which achieved values up to 30%. The 29Si-NMR spectra show two different siloxane peaks (T2 and T3), which supports the theory about the formation of MTMOS network structures. Thermal decomposition experiments were also carried out in a TG analyzer under a nitrogen atmosphere. The apparent activation energy was determined according to the iso-conversional methods of Friedman, Flynn-Wall-Ozawa, modified Coats-Redfern, and Starink. The apparent activation energy between 10 and 70% conversion is 147–172, 170–291, 189–251, and 192–248 kJ mol−1 for wood and WSiO2Cs with WPGs of 10, 20, and 30%, respectively. However, the reaction order between 10 and 70% conversion calculated by the Avrami theory was 0.50–0.56, 0.35–0.45, 0.33–0.44, and 0.28–0.48. These results indicate that the dimensional and thermal stability of the wood could be effectively enhanced by MTMOS treatment.

Optical Properties and Phase Transformation Kinetics of Ge-Sb-Te-(N) Alloy Thin Films Investigated by Ellipsometry

2003 ◽  
Vol 803 ◽  
Author(s):  
Sang Youl Kim
Keyword(s):  
Thin Films ◽  
Phase Transformation ◽  
Optical Properties ◽  
Phase Change ◽  
Crystallization Behavior ◽  
Ex Situ ◽  
Recent Analysis ◽  
Avrami Equation ◽  
Step Process ◽  
Kinetics Of

ABSTRACTThe recent research works of optical properties and crystallization kinetics of phase change Ge-Sb-Te-(N) alloy by using ellipsometry are reviewed.The complex refractive index spectra of phase-change Ge2Sb2+xTe5 thin films and those of the nitrogen Ge2Sb2Te5 thin films have been determined.The crystallization behavior of amorphous Ge2Sb2Te5 thin films investigated by in situ ellipsometry revealed that the crystallization process of Ge2Sb2Te5 near 140°C is a two-step process. The kinetic exponent of the Johnson-Mehl-Avrami equation was about 4.4 for the first stage and 1.1 for the second stage. Ex situ study confirmed the cascaded crystallization behavior of phase-change Ge2Sb2Te5 films.A passive type single wavelength ellipsometer adopting a DOAP (division-of-amplitude photopolarimeter) configuration with nanosecond time resolution is developed to monitor the phase transformation of Ge2Sb2Te5 caused by a high power nanosecond laser pulse in real time. The two-step process - the fast nucleation-dominant stage followed by the slow anomalous grain growth stage is confirmed.Based on the recent analysis of the ellipsometric isotherm at moderately elevated temperature, we found for the first time that the fast nucleation dominant crystallization of Ge2Sb2Te 5 can be better explained by a modified JMA equation that illustrates the nucleation dominated process where the creation rate of a new nucleus is proportional to the density of preexisting nuclei and growth rate is negligible.

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