scholarly journals Non-isothermal crystallization of lithium germanophosphate glass studied by different kinetic methods

2018 ◽  
Vol 50 (2) ◽  
pp. 193-203 ◽  
Author(s):  
Srdjan Matijasevic ◽  
Snezana Grujic ◽  
Vladimir Topalovic ◽  
Jelena Nikolic ◽  
Sonja Smiljanic ◽  
...  
Keyword(s):  
Isothermal Condition ◽  
Nucleation And Growth ◽  
Glass Crystallization ◽  
Crystallization Peak ◽  
Crystal Transformation ◽  
Model Free ◽  
Complex Process ◽  
Glass Crystal ◽  
Linear Integral ◽  
Kinetics Of

Crystallization kinetics of 22.5Li2O?10Al2O3?30GeO2?37.5P2O5 (mol%) glass was studied under non-isothermal condition using the differential thermal analysis (DTA). The study was performed by using the first crystallization peak temperature (Tp1) which belongs to the precipitation of LiGe2(PO4)3 phase in the glass. The activation energy of glass crystallization (Ea) was determined using different isokinetic methods. The dependence of Ea on the degree of glass-crystal transformation (?) was studied using model-free isoconversional linear integral KAS (Kissinger-Akahira-Sunose) and FWO (Flynn-Wall-Ozawa) methods. It was shown that the Ea varies with ? and hence with temperature and consequently the glass/crystal transformation can be described as a complex process involving different mechanisms of nucleation and growth.

Kinetics of Mg2Sn Synthesis Reaction under Isothermal Condition

2010 ◽  
Vol 146-147 ◽  
pp. 1712-1716
Author(s):  
Yu Feng Wu ◽  
Wen Bo Du ◽  
Zhao Hui Wang ◽  
Tie Yong Zuo
Keyword(s):  
Isothermal Condition ◽  
Growth Control ◽  
Nucleation And Growth ◽  
Synthesis Process ◽  
Synthesis Reaction ◽  
Isothermal Reaction ◽  
Second Stage ◽  
Two Stages ◽  
Kinetics Of ◽  
Good Agreement

The kinetics of Mg2Sn synthesis reaction was studied under isothermal condition in the present paper. Results indicated that the isothermal reaction of Mg2Sn was controlled by two reactive mechanisms: the nucleation and growth control in the first stage corresponding to the Avrami exponent, m≈3, and the phase boundary control in the second stage corresponding to m≈1.1. The reactive activation energy (Ea ) for the two stages was 293.6 kJ·mol-1 and 358.1 kJ·mol-1, respectively. The microstructural evolution in Mg2Sn synthesis process was in good agreement with the two reactive mechanisms.

Iso-Conversional and Isokinetic Methods of Analysis of Non-Isothermal Crystallization in Ti50Cu20Ni30 Metallic Glass

2011 ◽  
Vol 171 ◽  
pp. 107-119
Author(s):  
Heena Dhurandhar ◽  
T. Lilly Shanker Rao ◽  
Kirit N. Lad ◽  
Arun Pratap
Keyword(s):  
Metallic Glass ◽  
Isoconversional Methods ◽  
Isoconversional Method ◽  
Scanning Calorimetry ◽  
Model Free ◽  
True Value ◽  
Linear Differential ◽  
Linear Integral ◽  
Kinetics Of

The crystallization kinetics of metallic glass Ti50Cu20Ni30 has been studied using Differential Scanning Calorimetry (DSC). The DSC thermograms have been analysed using the model-free isoconversional methods and model dependent isokinetic methods. The activation energy(E) for the crystallization process has been determined utilizing; (i) various linear integral isoconversional methods, namely, Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose, Li Tang method (ii) linear differential isoconversional method and (iii) different isokinetic methods. In the present work, we intend to the determination of true value of E. The above methods are found to give consistent results for E.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

scholarly journals Torrefaction Thermogravimetric Analysis and Kinetics of Sorghum Distilled Residue for Sustainable Fuel Production

2021 ◽  
Vol 13 (8) ◽  
pp. 4246
Author(s):  
Shih-Wei Yen ◽  
Wei-Hsin Chen ◽  
Jo-Shu Chang ◽  
Chun-Fong Eng ◽  
Salman Raza Naqvi ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Pso Algorithm ◽  
Nitrogen Atmosphere ◽  
Computational Method ◽  
Weight Changes ◽  
Design And Optimization ◽  
Thermogravimetric Analyzer ◽  
Model Free ◽  
Different Temperatures ◽  
Kinetics Of

This study investigated the kinetics of isothermal torrefaction of sorghum distilled residue (SDR), the main byproduct of the sorghum liquor-making process. The samples chosen were torrefied isothermally at five different temperatures under a nitrogen atmosphere in a thermogravimetric analyzer. Afterward, two different kinetic methods, the traditional model-free approach, and a two-step parallel reaction (TPR) kinetic model, were used to obtain the torrefaction kinetics of SDR. With the acquired 92–97% fit quality, which is the degree of similarity between calculated and real torrefaction curves, the traditional method approached using the Arrhenius equation showed a poor ability on kinetics prediction, whereas the TPR kinetic model optimized by the particle swarm optimization (PSO) algorithm showed that all the fit qualities are as high as 99%. The results suggest that PSO can simulate the actual torrefaction kinetics more accurately than the traditional kinetics approach. Moreover, the PSO method can be further employed for simulating the weight changes of reaction intermediates throughout the process. This computational method could be used as a powerful tool for industrial design and optimization in the biochar manufacturing process.

Diffusion Enhancement in Glassy Metals Under Non-Equilibrium Conditions

1995 ◽  
Vol 400 ◽  
Author(s):  
S. Bellini ◽  
G. Mazzone ◽  
A. Montone ◽  
M. Vittori-antisari Enea ◽  
C.R. Casaccia
Keyword(s):  
Free Volume ◽  
Growth Kinetics ◽  
Bulk Diffusion ◽  
High Energy ◽  
First Case ◽  
Diffusion Enhancement ◽  
Glass Crystal ◽  
Kinetics Of ◽  
Crystal Interface ◽  
Diffusion Properties

AbstractThe diffusion properties of a Ni-Zr metallic glass formed at the interface of a bulk diffusion couple have been studied in conditions far from a fully relaxed state. The growth kinetics of the interface film have been enhanced by both plastic deformation and high energy electron irradiation. Different results have been obtained in the two cases, since in the first case the film grows exponentially with time, while in the second case the usual square root dependence on time is observed. This behaviour has been interpreted as a consequence of the annihilation kinetics of the excess free volume introduced in the glass by the above methods. Two different mechanisms of free volume annihilation , namely exchange with a crystal vacancy at the glass-crystal interface and structural relaxation in the bulk glassy phase have been considered to be operative so that the nature of the growth kinetics has been found to depend on the mechanism predominant in each experimental condition.

Inhomogeneous Swelling Near Grain Boundaries in Irradiated Materials: Cavity Nucleation and Growth Saturation Effects

2000 ◽  
Vol 650 ◽  
Author(s):  
S. L. Dudarev
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Nucleation And Growth ◽  
Homogeneous Distribution ◽  
Rate Theory ◽  
Diffusional Growth ◽  
Standard Rate ◽  
Saturation Effects ◽  
Kinetics Of ◽  
Cascade Damage

ABSTRACTThe effect of inhomogeneous nucleation and growth of cavities near grain boundaries illustrates the failure of the standard rate theory to describe the kinetics of phase transformations in irradiated materials under cascade damage conditions. The enhanced swelling observed near grain boundaries is believed to result from the competition between the diffusional growth of cavities and their shrinkage due to the interaction with mobile interstitial clusters. Swelling rates associated with the two processes behave in a radically different way as a function of the size of growing cavities. For a spatially homogeneous distribution of cavities this gives rise to the saturation of swelling in the limit of large irradiation doses.We investigate the evolution of the population of cavities nucleating and growing near a planar grain boundary. We show that a cavity growing near the boundary is able to reach a size that is substantially larger than the size of a cavity growing in the interior region of the grain. For a planar grain boundary the magnitude of swelling at maximum is found to be up to eight times higher than the magnitude of swelling in the grain interior.

Physicochemical Characterization and Pyrolysis Kinetic Study of Sugarcane Bagasse Using Thermogravimetric Analysis

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Anil Kumar Varma ◽  
Prasenjit Mondal
Keyword(s):  
Activation Energy ◽  
Sugarcane Bagasse ◽  
Physicochemical Characterization ◽  
Maximum Error ◽  
Proximate Analysis ◽  
Pyrolysis Kinetics ◽  
Exponential Factor ◽  
Physiochemical Properties ◽  
Model Free ◽  
Complex Process

The present study was conducted to investigate the physicochemical properties and pyrolysis kinetics of sugarcane bagasse (SB). The physiochemical properties of SB were determined to examine its potential for pyrolysis. The physiochemical properties such as proximate analysis, ultimate analysis, heating values, lignocellulosic composition, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) of SB were investigated. The pyrolysis experiments were conducted in a nonisothermal thermogravimetric analyzer (TGA) to understand the thermal degradation behavior of SB. The activation energy (Ea) of SB pyrolysis was calculated by model-free Kissinger–Akahira–Sunose (KAS) and Ozawa–Flynn–Wall (OFW) methods. Average values of activation energy determined through KAS and OFW methods are found as 91.64 kJ/mol and 104.43 kJ/mol, respectively. Variation in the activation energy with degree of conversion was observed, which shows that pyrolysis is a complex process composed of several reactions. Coats–Redfern method was used to calculate the pre-exponential factor and reaction order. Conversion of SB due to heat treatment computed by using the kinetic parameters is found to be in good agreement with the experimental conversion data, and the maximum error limit between the experimental and predicted conversions is 8.5% for 5 °C/min, 6.0% for 10 °C/min, and 11.6% for 20 °C/min. The current investigation proves the suitability of SB as a potential feedstock for pyrolysis.

Effects of Dispersed Al2O3 Particles on Sintering of LTCC

2008 ◽  
Vol 39-40 ◽  
pp. 375-380
Author(s):  
Ralf Müller ◽  
Stefan Reinsch ◽  
Markus Eberstein ◽  
Joachim Deubener ◽  
A. Thiel ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Al2o3 Particle ◽  
Model Composite ◽  
Heating Microscopy ◽  
Glass Crystal ◽  
Rate Controlled ◽  
Higher Temperature ◽  
Crystal Particle ◽  
Kinetics Of ◽  
Glass Viscosity

The sintering of Low Temperature Co-fired Ceramics prepared from alumoborosilicate glass- and Al2O3 powders of similar small particle size was studied by dilatometry, heating microscopy, microstructure analysis, glass- and effective viscosity measurements. The steric effect of Al3O3 inclusions was studied using a “non-reactive” model composite. With increasing Al3O3 volume fraction ( Φ ≤ 0.45), sintering decelerates and its final stage shifts to higher temperature. The attainable shrinkage is reduced as Al2O3 particle clusters bearing residual pores become more frequent. The kinetics of sintering could be described formally superposing the weighed contributions of differentially sized and randomly composed glass-crystal particle clusters and assuming a sintering rate controlled by the effective matrix viscosity, which increases with Φ and with progressive wetting of Al2O3 particles during densification. The “reactive” model composite shows significant dissolution of Al2O3 into the glass, which has two opposed effects on sintering: reducing Φ and increasing glass viscosity. For the present case ( Φ = 0.25), the latter effect dominates and sintering is retarded by Al2O3 dissolution. Crystallization of wollastonite starts after full densification. Dissolution of Al2O3 was found to promote the subsequent growth of anorthite.

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