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Thermal Analysis Kinetics for Understanding Materials Behavior
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Thermal Analysis Kinetics for Understanding Materials Behavior

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Physical Chemistry".

Deadline for manuscript submissions: closed (30 June 2019) | Viewed by 51661

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Sergey Vyazovkin

E-Mail Website
Guest Editor
Department of Chemistry, University of Alabama at Birmingham, 901 S. 14th Street, Birmingham, AL 35294, USA
Interests: kinetics of thermally stimulated chemical reactions and phase transitions in the condensed phase; thermal analysis methods

Special Issue Information

Dear Colleagues,

Changing the temperature of a substance can stimulate dramatic changes of its state. These changes can be intermolecular (physical) and intramolecular (chemical) in nature. Physical changes occur without breaking intramolecular bonds, and lead to transitions between the four major phases: gas, liquid, crystal, and glass. Chemical changes are associated with chemical reactions that originate from breaking intramolecular bonds. Phase transitions as well as chemical reactions occur at finite rates. Measuring the rates of processes is the realm of kinetics. The kinetics of thermally stimulated processes is measured routinely by thermal analysis techniques such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Knowing the process rates and their dependence on temperature is of vital importance for understanding the behavior of materials exposed to variations in temperature. For example, the successful function of glassy materials is contingent upon negligibly small rates of the transition from the glass to crystalline phase. On the other hand, phase change materials rely on rapid transition between the liquid and crystalline phases. Similar principles hold for chemical reactions. Slower rates of chemical decomposition give rise to longer drug shelf lives. However, very fast decomposition rates determine the efficiency of explosives and propellants.

In recent years, thermal analysis kinetics has made significant progress by developing computational tools for reliable kinetic analysis. It has also expanded its traditional application area to newly developed nano- and bio-materials. The purpose of this Special Issue is to collect a series of papers that reflect recent developments in the field and highlight the essential role of thermal analysis kinetics in understanding the processes responsible for the thermal behavior of various materials. The processes of interest involve (but are not limited to): thermal decomposition (degradation), polymerization, crosslinking (curing), oxidation, reduction, crystallization, melting, and glass and solid–solid transitions.

Prof. Dr. Sergey Vyazovkin
Guest Editor

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • nonisothermal and isothermal kinetics
  • Arrhenius parameters
  • activation energy, preexponential factor, reaction model
  • differential scanning calorimetry (DSC)
  • thermogravimetric analysis (TGA)
  • thermal decomposition
  • thermal and thermo-oxidative degradation
  • polymerization
  • crosslinking (curing)
  • oxidation and reduction
  • crystallization
  • melting
  • glass transition
  • solid–solid (morphological) transition

Published Papers (13 papers)

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Research

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15 pages, 2970 KiB  
Article
Effects of Lipid Solid Mass Fraction and Non-Lipid Solids on Crystallization Behaviors of Model Fats under High Pressure
by Musfirah Zulkurnain, V.M. Balasubramaniam and Farnaz Maleky
Molecules 2019, 24(15), 2853; https://doi.org/10.3390/molecules24152853 - 6 Aug 2019
Cited by 4 | Viewed by 3981
Abstract
Different fractions of fully hydrogenated soybean oil (FHSBO) in soybean oil (10–30% w/w) and the addition of 1% salt (sodium chloride) were used to investigate the effect of high-pressure treatments (HP) on the crystallization behaviors and physical properties of the binary mixtures. [...] Read more.
Different fractions of fully hydrogenated soybean oil (FHSBO) in soybean oil (10–30% w/w) and the addition of 1% salt (sodium chloride) were used to investigate the effect of high-pressure treatments (HP) on the crystallization behaviors and physical properties of the binary mixtures. Sample microstructure, solid fat content (SFC), thermal and rheological properties were analyzed and compared against a control sample (crystallized under atmospheric condition). The crystallization temperature (Ts) of all model fats under isobaric conditions increased quadratically with pressure until reaching a pressure threshold. As a result of this change, the sample induction time of crystallization (tc) shifted from a range of 2.74–0.82 min to 0.72–0.43 min when sample crystallized above the pressure threshold under adiabatic conditions. At the high solid mass fraction, the addition of salt reduced the pressure threshold to induce crystallization during adiabatic compression. An increase in pressure significantly reduced mean cluster diameter in relation to the reduction of tc regardless of the solid mass fraction. In contrast, the sample macrostructural properties (SFC, storage modulus) were influenced more significantly by solid mass fractions rather than pressure levels. The creation of lipid gel was observed in the HP samples at 10% FHSBO. The changes in crystallization behaviors indicated that high-pressure treatments were more likely to influence crystallization mechanisms at low solid mass fraction. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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24 pages, 7487 KiB  
Article
Non-Isothermal Crystallization Kinetics of Poly(4-Hydroxybutyrate) Biopolymer
by Ina Keridou, Luis J. del Valle, Lutz Funk, Pau Turon, Lourdes Franco and Jordi Puiggalí
Molecules 2019, 24(15), 2840; https://doi.org/10.3390/molecules24152840 - 5 Aug 2019
Cited by 15 | Viewed by 4600
Abstract
The non-isothermal crystallization of the biodegradable poly(4-hydroxybutyrate) (P4HB) has been studied by means of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). In the first case, Avrami, Ozawa, Mo, Cazé, and Friedman methodologies were applied. The isoconversional approach developed by Vyazovkin allowed [...] Read more.
The non-isothermal crystallization of the biodegradable poly(4-hydroxybutyrate) (P4HB) has been studied by means of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). In the first case, Avrami, Ozawa, Mo, Cazé, and Friedman methodologies were applied. The isoconversional approach developed by Vyazovkin allowed also the determination of a secondary nucleation parameter of 2.10 × 105 K2 and estimating a temperature close to 10 °C for the maximum crystal growth rate. Similar values (i.e., 2.22 × 105 K2 and 9 °C) were evaluated from non-isothermal Avrami parameters. All experimental data corresponded to a limited region where the polymer crystallized according to a single regime. Negative and ringed spherulites were always obtained from the non-isothermal crystallization of P4HB from the melt. The texture of spherulites was dependent on the crystallization temperature, and specifically, the interring spacing decreased with the decrease of the crystallization temperature (Tc). Synchrotron data indicated that the thickness of the constitutive lamellae varied with the cooling rate, being deduced as a lamellar insertion mechanism that became more relevant when the cooling rate increased. POM non-isothermal measurements were also consistent with a single crystallization regime and provided direct measurements of the crystallization growth rate (G). Analysis of the POM data gave a secondary nucleation constant and a bell-shaped G-Tc dependence that was in relative agreement with DSC analysis. All non-isothermal data were finally compared with information derived from previous isothermal analyses. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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15 pages, 4191 KiB  
Article
Kinetic Processes in Amorphous Materials Revealed by Thermal Analysis: Application to Glassy Selenium
by Jiří Málek and Roman Svoboda
Molecules 2019, 24(15), 2725; https://doi.org/10.3390/molecules24152725 - 26 Jul 2019
Cited by 16 | Viewed by 3474
Abstract
It is expected that viscous flow is affecting the kinetic processes in a supercooled liquid, such as the structural relaxation and the crystallization kinetics. These processes significantly influence the behavior of glass being prepared by quenching. In this paper, the activation energy of [...] Read more.
It is expected that viscous flow is affecting the kinetic processes in a supercooled liquid, such as the structural relaxation and the crystallization kinetics. These processes significantly influence the behavior of glass being prepared by quenching. In this paper, the activation energy of viscous flow is discussed with respect to the activation energy of crystal growth and the structural relaxation of glassy selenium. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and hot-stage infrared microscopy were used. It is shown that the activation energy of structural relaxation corresponds to that of the viscous flow at the lowest value of the glass transition temperature obtained within the commonly achievable time scale. The temperature-dependent activation energy of crystal growth, data obtained by isothermal and non-isothermal DSC and TMA experiments, as well as direct microscopic measurements, follows nearly the same dependence as the activation energy of viscous flow, taking into account viscosity and crystal growth rate decoupling due to the departure from Stokes–Einstein behavior. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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18 pages, 5978 KiB  
Article
Thermal Decomposition of Maya Blue: Extraction of Indigo Thermal Decomposition Steps from a Multistep Heterogeneous Reaction Using a Kinetic Deconvolution Analysis
by Yui Yamamoto and Nobuyoshi Koga
Molecules 2019, 24(13), 2515; https://doi.org/10.3390/molecules24132515 - 9 Jul 2019
Cited by 15 | Viewed by 3796
Abstract
Examining the kinetics of solids’ thermal decomposition with multiple overlapping steps is of growing interest in many fields, including materials science and engineering. Despite the difficulty of describing the kinetics for complex reaction processes constrained by physico-geometrical features, the kinetic deconvolution analysis (KDA) [...] Read more.
Examining the kinetics of solids’ thermal decomposition with multiple overlapping steps is of growing interest in many fields, including materials science and engineering. Despite the difficulty of describing the kinetics for complex reaction processes constrained by physico-geometrical features, the kinetic deconvolution analysis (KDA) based on a cumulative kinetic equation is one practical method of obtaining the fundamental information needed to interpret detailed kinetic features. This article reports the application of KDA to thermal decomposition of clay minerals and indigo–clay mineral hybrid compounds, known as Maya blue, from ancient Mayan civilization. Maya blue samples were prepared by heating solid mixtures of indigo and clay minerals (palygorskite and sepiolite), followed by purification. The multistep thermal decomposition processes of the clay minerals and Maya blue samples were analyzed kinetically in a stepwise manner through preliminary kinetic analyses based on a conventional isoconversional method and mathematical peak deconvolution to finally attain the KDA. By comparing the results of KDA for the thermal decomposition processes of the clay minerals and the Maya blue samples, information about the thermal decomposition steps of the indigo incorporated into the Maya blue samples was extracted. The thermal stability of Maya blue samples was interpreted through the kinetic characterization of the extracted indigo decomposition steps. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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16 pages, 2090 KiB  
Article
Critical Appraisal of Kinetic Calculation Methods Applied to Overlapping Multistep Reactions
by Nikita V. Muravyev, Alla N. Pivkina and Nobuyoshi Koga
Molecules 2019, 24(12), 2298; https://doi.org/10.3390/molecules24122298 - 21 Jun 2019
Cited by 66 | Viewed by 4671
Abstract
Thermal decomposition of solids often includes simultaneous occurrence of the overlapping processes with unequal contributions in a specific physical quantity variation during the overall reaction (e.g., the opposite effects of decomposition and evaporation on the caloric signal). Kinetic analysis for such reactions is [...] Read more.
Thermal decomposition of solids often includes simultaneous occurrence of the overlapping processes with unequal contributions in a specific physical quantity variation during the overall reaction (e.g., the opposite effects of decomposition and evaporation on the caloric signal). Kinetic analysis for such reactions is not a straightforward, while the applicability of common kinetic calculation methods to the particular complex processes has to be justified. This study focused on the critical analysis of the available kinetic calculation methods applied to the mathematically simulated thermogravimetry (TG) and differential scanning calorimetry (DSC) data. Comparing the calculated kinetic parameters with true kinetic parameters (used to simulate the thermoanalytical curves), some caveats in the application of the Kissinger, isoconversional Friedman, Vyazovkin and Flynn–Wall–Ozawa methods, mathematical and kinetic deconvolution approaches and formal kinetic description were highlighted. The model-fitting approach using simultaneously TG and DSC data was found to be the most useful for the complex processes assumed in the study. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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25 pages, 6927 KiB  
Article
Continuous Monitoring of Shelf Lives of Materials by Application of Data Loggers with Implemented Kinetic Parameters
by Bertrand Roduit, Charles Albert Luyet, Marco Hartmann, Patrick Folly, Alexandre Sarbach, Alain Dejeaifve, Rowan Dobson, Nicolas Schroeter, Olivier Vorlet, Michal Dabros and Richard Baltensperger
Molecules 2019, 24(12), 2217; https://doi.org/10.3390/molecules24122217 - 13 Jun 2019
Cited by 20 | Viewed by 5420
Abstract
The evaluation of the shelf life of, for example, food, pharmaceutical materials, polymers, and energetic materials at room or daily climate fluctuation temperatures requires kinetic analysis in temperature ranges which are as similar as possible to those at which the products will be [...] Read more.
The evaluation of the shelf life of, for example, food, pharmaceutical materials, polymers, and energetic materials at room or daily climate fluctuation temperatures requires kinetic analysis in temperature ranges which are as similar as possible to those at which the products will be stored or transported in. A comparison of the results of the evaluation of the shelf life of a propellant and a vaccine calculated by advanced kinetics and simplified 0th and 1st order kinetic models is presented. The obtained simulations show that the application of simplified kinetics or the commonly used mean kinetic temperature approach may result in an imprecise estimation of the shelf life. The implementation of the kinetic parameters obtained from advanced kinetic analyses into programmable data loggers allows the continuous online evaluation and display on a smartphone of the current extent of the deterioration of materials. The proposed approach is universal and can be used for any goods, any methods of shelf life determination, and any type of data loggers. Presented in this study, the continuous evaluation of the shelf life of perishable goods based on the Internet of Things (IoT) paradigm helps in the optimal storage/shipment and results in a significant decrease of waste. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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17 pages, 5871 KiB  
Article
Kinetics of Crystallization and Thermal Degradation of an Isotactic Polypropylene Matrix Reinforced with Graphene/Glass-Fiber Filler
by Evangelia Tarani, George Z. Papageorgiou, Dimitrios N. Bikiaris and Konstantinos Chrissafis
Molecules 2019, 24(10), 1984; https://doi.org/10.3390/molecules24101984 - 23 May 2019
Cited by 18 | Viewed by 3639
Abstract
Polypropylene composites reinforced with a filler mixture of graphene nanoplatelet-glass fiber were prepared by melt mixing, while conventional composites containing graphene nanoplatelet and glass fiber were prepared for comparative reasons. An extensive study of thermally stimulated processes such as crystallization, nucleation, and kinetics [...] Read more.
Polypropylene composites reinforced with a filler mixture of graphene nanoplatelet-glass fiber were prepared by melt mixing, while conventional composites containing graphene nanoplatelet and glass fiber were prepared for comparative reasons. An extensive study of thermally stimulated processes such as crystallization, nucleation, and kinetics was carried out using Differential Scanning Calorimetry and Thermogravimetric Analysis. Moreover, effective activation energy and kinetic parameters of the thermal decomposition process were determined by applying Friedman’s isoconversional differential method and multivariate non-linear regression method. It was found that the graphene nanoplatelets act positively towards the increase in crystallization rate and nucleation phenomena under isothermal conditions due to their large surface area, inherent nucleation activity, and high filler content. Concerning the thermal degradation kinetics of polypropylene graphene nanoplatelets/glass fibers composites, a change in the decomposition mechanism of the matrix was found due to the presence of graphene nanoplatelets. The effect of graphene nanoplatelets dominates that of the glass fibers, leading to an overall improvement in performance. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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9 pages, 1937 KiB  
Article
Investigation of Size-Dependent Sublimation Kinetics of 2,4,6-Trinitrotoluene (TNT) Micro-Islands Using In Situ Atomic Force Microscopy
by Yong Joon Lee and Brandon L. Weeks
Molecules 2019, 24(10), 1895; https://doi.org/10.3390/molecules24101895 - 17 May 2019
Cited by 7 | Viewed by 2628
Abstract
Kinetic thermal analysis was conducted using in situ atomic force microscopy (AFM) at a temperature range of 15–25 °C to calculate the activation energy of the sublimation of 2,4,6-trinitrotoluene (TNT) islands. The decay of different diameter ranges (600–1600 nm) of TNT islands was [...] Read more.
Kinetic thermal analysis was conducted using in situ atomic force microscopy (AFM) at a temperature range of 15–25 °C to calculate the activation energy of the sublimation of 2,4,6-trinitrotoluene (TNT) islands. The decay of different diameter ranges (600–1600 nm) of TNT islands was imaged at various temperatures isothermally such that an activation energy could be obtained. The activation energy of the sublimation of TNT increases as the diameter of islands increases. It was found that the coarsening and the sublimation rate of TNT islands can be determined by the local environment of the TNT surface. This result demonstrates that a diffusion model cannot be simply applied to “real world” systems for explaining the sublimation behavior and for estimating the coarsening of TNT. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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17 pages, 5594 KiB  
Article
Thermal Decomposition Kinetics and Mechanism of In-Situ Prepared Bio-Based Poly(propylene 2,5-furan dicarboxylate)/Graphene Nanocomposites
by Zoi Terzopoulou, Evangelia Tarani, Nejib Kasmi, Lazaros Papadopoulos, Konstantinos Chrissafis, Dimitrios G. Papageorgiou, George Z. Papageorgiou and Dimitrios N. Bikiaris
Molecules 2019, 24(9), 1717; https://doi.org/10.3390/molecules24091717 - 2 May 2019
Cited by 21 | Viewed by 4519
Abstract
Bio-based polyesters are a new class of materials that are expected to replace their fossil-based homologues in the near future. In this work, poly(propylene 2,5-furandicarboxylate) (PPF) nanocomposites with graphene nanoplatelets were prepared via the in-situ melt polycondensation method. The chemical structure of the [...] Read more.
Bio-based polyesters are a new class of materials that are expected to replace their fossil-based homologues in the near future. In this work, poly(propylene 2,5-furandicarboxylate) (PPF) nanocomposites with graphene nanoplatelets were prepared via the in-situ melt polycondensation method. The chemical structure of the resulting polymers was confirmed by 1H-NMR spectroscopy. Thermal stability, decomposition kinetics and the decomposition mechanism of the PPF nanocomposites were studied in detail. According to thermogravimetric analysis results, graphene nanoplatelets did nοt affect the thermal stability of PPF at levels of 0.5, 1.0 and 2.5 wt.%, but caused a slight increase in the activation energy values. Pyrolysis combined with gas chromatography and mass spectroscopy revealed that the decomposition mechanism of the polymer was not altered by the presence of graphene nanoplatelets but the extent of secondary homolytic degradation reactions was increased. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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16 pages, 3136 KiB  
Article
Advanced Isoconversional Kinetic Analysis for the Elucidation of Complex Reaction Mechanisms: A New Method for the Identification of Rate-Limiting Steps
by Nicolas Sbirrazzuoli
Molecules 2019, 24(9), 1683; https://doi.org/10.3390/molecules24091683 - 30 Apr 2019
Cited by 54 | Viewed by 3988
Abstract
Two complex cure mechanisms were simulated. Isoconversional kinetic analysis was applied to the resulting data. The study highlighted correlations between the reaction rate, activation energy dependency, rate constants for the chemically controlled part of the reaction and the diffusion-controlled part, activation energy and [...] Read more.
Two complex cure mechanisms were simulated. Isoconversional kinetic analysis was applied to the resulting data. The study highlighted correlations between the reaction rate, activation energy dependency, rate constants for the chemically controlled part of the reaction and the diffusion-controlled part, activation energy and pre-exponential factors of the individual steps and change in rate-limiting steps. It was shown how some parameters computed using Friedman’s method can help to identify change in the rate-limiting steps of the overall polymerization mechanism as measured by thermoanalytical techniques. It was concluded that the assumption of the validity of a single-step equation when restricted to a given α value holds for complex reactions. The method is not limited to chemical reactions, but can be applied to any complex chemical or physical transformation. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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15 pages, 2170 KiB  
Article
Kinetic Analysis of Digestate Slow Pyrolysis with the Application of the Master-Plots Method and Independent Parallel Reactions Scheme
by Pietro Bartocci, Roman Tschentscher, Ruth Elisabeth Stensrød, Marco Barbanera and Francesco Fantozzi
Molecules 2019, 24(9), 1657; https://doi.org/10.3390/molecules24091657 - 27 Apr 2019
Cited by 34 | Viewed by 4405
Abstract
The solid fraction obtained by mechanical separation of digestate from anaerobic digestion plants is an attractive feedstock for the pyrolysis process. Especially in the case of digestate obtained from biogas plants fed with energy crops, this can be considered a lignin rich residue. [...] Read more.
The solid fraction obtained by mechanical separation of digestate from anaerobic digestion plants is an attractive feedstock for the pyrolysis process. Especially in the case of digestate obtained from biogas plants fed with energy crops, this can be considered a lignin rich residue. The aim of this study is to investigate the pyrolytic kinetic characteristics of solid digestate. The Starink model-free method has been used for the kinetic analysis of the pyrolysis process. The average Activation Energy value is about 204.1 kJ/mol, with a standard deviation of 25 kJ/mol, which corresponds to the 12% of the average value. The activation energy decreased along with the conversion degree. The variation range of the activation energy is about 99 kJ/mol, this means that the average value cannot be used to statistically represent the whole reaction. The Master-plots method was used for the determination of the kinetic model, obtaining that n-order was the most probable one. On the other hand, the process cannot be modeled with a single-step reaction. For this reason it has been used an independent parallel reactions scheme to model the complete process. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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8 pages, 2088 KiB  
Article
Non-Isothermal Sublimation Kinetics of 2,4,6-Trinitrotoluene (TNT) Nanofilms
by Walid M. Hikal and Brandon L. Weeks
Molecules 2019, 24(6), 1163; https://doi.org/10.3390/molecules24061163 - 23 Mar 2019
Cited by 2 | Viewed by 2626
Abstract
Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for [...] Read more.
Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn–Wall, and Kissinger models were 105.9 ± 1.4 kJ mol−1, 102.1 ± 2.7 kJ mol−1, and 105.8 ± 1.6 kJ mol−1, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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Review

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15 pages, 2373 KiB  
Review
All You Need to Know about the Kinetics of Thermally Stimulated Reactions Occurring on Cooling
by Tatsiana Liavitskaya and Sergey Vyazovkin
Molecules 2019, 24(10), 1918; https://doi.org/10.3390/molecules24101918 - 18 May 2019
Cited by 4 | Viewed by 2684
Abstract
In this tutorial overview article the authors share their original experience in studying the kinetics of thermally stimulated reactions under the conditions of continuous cooling. It is stressed that the kinetics measured on heating is similar to that measured on cooling only for [...] Read more.
In this tutorial overview article the authors share their original experience in studying the kinetics of thermally stimulated reactions under the conditions of continuous cooling. It is stressed that the kinetics measured on heating is similar to that measured on cooling only for single-step reactions. For multi-step reactions the respective kinetics can differ dramatically. The application of an isoconversional method to thermogravimetry (TGA) or differential scanning calorimetry (DSC) data allows one to recognize multi-step kinetics in the form of the activation energy that varies with conversion. Authors’ argument is supported by theoretical considerations as well as by experimental examples that include the reactions of thermal decomposition and crosslinking polymerization (curing). The observed differences in the kinetics measured on heating and cooling ultimately manifest themselves in the Arrhenius plots of the opposite curvatures, which means that the heating kinetics cannot be used to predict the kinetics on cooling. The article provides important background knowledge necessary for conducting successful kinetic studies on cooling. It includes a practical advice on optimizing the parameters of cooling experiments as well as on proper usage of kinetic methods for analysis of obtained data. Full article
(This article belongs to the Special Issue Thermal Analysis Kinetics for Understanding Materials Behavior)
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