Kinetic Deconvolution Analysis Research Articles

Multistep kinetics in self-induced sol–gel process of amorphous anhydride formation during thermal dehydration of potassium tetraborate tetrahydrate

AbstractThe physico-geometrical mechanism and kinetics of the multistep thermal dehydration of potassium tetraborate tetrahydrate was investigated as a model reaction to produce amorphous anhydrate via the self-induced sol–gel process. The thermal dehydration is composed of three consecutive dehydration steps: (1) a surface reaction in the solid-state accompanied by crack formation; (2) a rapid mass loss process accompanied by liquefaction to form the aggregate of the gel powders; and (3) the dehydration of gel powder aggregate to form a glassy anhydride. The changes in the contribution of the individual dehydration steps to the overall process according to the sample particle size and the heating rate (β) were identified as specific features of the multistep dehydration, which was characterized quantitatively using mathematical deconvolution analysis with log-normal four-parameter functions. The difficulty in determining the apparent activation energy (Ea) of the individual dehydration steps using isoconversional analysis due to the changes in the contribution depending on β values was addressed using modulated temperature thermogravimetry. Using the contributions and the apparent Ea of the individual dehydration steps as initial values, the kinetic description of the multistep thermal dehydration was refined through a kinetic deconvolution analysis using the cumulative kinetic equation. As a result, the individual dehydration steps were kinetically characterized as: (1) a surface reaction described by the first-order rate law with Ea,1 of approximately 68 kJ mol−1; (2) a reaction accompanied by liquefaction controlled by an autocatalytic rate behavior with Ea,2 of approximately 123 kJ mol−1; (3) a diffusion-controlled dehydration of gel powder with Ea,3 of approximately 82 kJ mol−1.

Kinetic modelling of mixed plastic waste pyrolysis

The study of plastic waste thermal decomposition and kinetics is a crucial step for optimal reactor design and the scale-up of pyrolysis technologies for chemical recycling. Kinetic parameters of individual and mixed plastic waste samples that resemble the main components of plastic waste streams (polyolefins and polyesters) were determined in this study using thermogravimetric analysis. Strong dependencies of activation energy on conversion were found for the mixtures, indicating that the process occurs in multiple steps and there are strong interactions between plastic components, lowering their activation energy during the decomposition. PP and LDPE decomposed via two separate steps whereas others decomposed via a single step process. For plastic mixtures, three dominant partially overlapping steps were identified. Kinetic deconvolution analysis improved model accuracy of mixtures and enabled the study of kinetic contributions and behaviour of individual steps. The models were then applied to predict experimental data at various heating conditions and plastic compositions.

Unraveling the Impact of Heat- or Moist-Aging on the Combustion Heat, Ignition Features, Multistep Thermal Decomposition, and Kinetics of a Magnesium-Based Energetic Composite

ABSTRACT In this work, a Mg-based energetic composites, commonly known as pyrotechnic tracer composition (Mg-PC), was successfully fabricated by a mechanical milling method. The influence of the impact of artificial heat- or moist-aging on the combustion heat, ignition characteristics, and the thermal decomposition behavior of the as-prepared composite were investigated. Results show that the total energy output has decreased by 16% and 51% for the heat- and moist-aged samples, respectively. Microcalorimetric studies revealed shorter induction times and higher heat flow magnitudes for the different aged samples. Compared with the unaged composition, the ignition time of heat- and moist-aged samples are distinctly increased by 2.2 and 14.3 times, respectively. The thermogravimetric analysis demonstrated that humidity and thermal agings have a catalytic effect and accelerate the decomposition reaction, reducing the onset temperature decomposition by about 4–6°C after aging. The kinetic deconvolution analysis (KDA) indicated a multistep reaction comprising the resin decomposition, partial decomposition of the oxidizer, and the combustion of the Mg-PC. The activation energy of the first two decomposition steps was lower than that of the as-prepared mixture. Furthermore, the combustion process, corresponding to the third step exhibited slightly higher activation energy compared to the unaged formulation and is assigned to the fuel oxidation and the pre-decomposition of the oxidizer under heat- or moist-aging.

Kinetics of component reactions in calcium looping appeared during the multistep thermal decomposition of Portland cement under various atmospheric conditions

Calcium looping (CaL) reactions in a Ca(OH)2-CaCO3-CaO system for energy storage and CO2 absorption occur during the thermal decomposition of cement and concrete materials. Herein, we report the kinetic behavior of the reactions in a cement matrix as the necessary information for establishing a CaL cycle supported by cement/concrete materials. The thermal decomposition of Portland cement samples, characterized by different Ca(OH)2/CaCO3 ratios, under different atmospheric water vapor and CO2 conditions were investigated to reveal the kinetic behavior of the component reactions and the changes with atmospheric conditions. The multistep thermal decomposition, characteristic of each sample and atmospheric condition, were separated into individual reaction steps through a kinetic deconvolution analysis. Using the extracted kinetic curves for the reactions of Ca(OH)2 and CaCO3, retardation effects of atmospheric water vapor and CO2 on the thermal decompositions of Ca(OH)2 and CaCO3, respectively, were kinetically described by introducing different accommodation functions (AF) comprised of the partial pressures of the gases and their equilibrium pressure. In addition, the kinetic description of the catalytic effect of water vapor on the thermal decomposition of CaCO3 was achieved by introducing alternative AF of water vapor pressure. The thermally induced carbonation of Ca(OH)2, which occurred in the presence of atmospheric CO2, was characterized kinetically as physico-geometrically regulated consecutive reactions of thermal decomposition of Ca(OH)2 and subsequent carbonation of the as-produced CaO. Kinetic information concerning the reactions of Ca(OH)2 and CaCO3 in the cement materials is reported in details.

Thermally Induced Aragonite-Calcite Transformation in Freshwater Pearl: A Mutual Relation with the Thermal Dehydration of Included Water.

This study focuses on the relationship between the aragonite–calcite (A–C) transformation and the thermal dehydration of included water in the biomineralized aragonite construction using freshwater pearl. These thermally induced processes occur in the same temperature region. The thermal dehydration of included water was characterized through thermoanalytical investigations as an overlapping of three dehydration steps. Each dehydration step was separated through kinetic deconvolution analysis, and the kinetic parameters were determined. A single-step behavior of the A–C transformation was evidenced using high-temperature X-ray diffractometry and Fourier transform infrared spectrometry for the heat-treated samples. The kinetics of the A–C transformation was analyzed using the conversion curves under isothermal and linear nonisothermal conditions. The A–C transformation occurred in the corresponding temperature region of the thermal dehydration, ranging from the second half of the second dehydration step to the first half of the third dehydration step. Because the thermal dehydration process is constrained by the contracting geometry kinetics, the movement of the thermal dehydration reaction interface can be a trigger for the A–C transformation. In this scheme, the overall kinetics of the A–C transformation in the biomineralized aragonite construction is regulated by a contracting geometry.

Kinetic analysis of the multistep thermal decomposition of Maya Blue-type pigments to evaluate thermal stability

This study aimed to evaluate the practical usefulness of kinetic deconvolution analysis (kDa) as a means to obtain the kinetic information on specific reaction steps that characterize the thermal properties of materials for various purposes. The partially overlapping multistep thermal decomposition of Maya Blue (MB)-type pigments was used as an example reaction. Red and yellow MB-type pigment materials, composed of a fibrous clay mineral and an organic dye, were synthesized using palygorskite and sepiolite as the clay minerals and Methyl Red and Alizarin as red and yellow dyes, respectively. The multistep thermal decompositions of the MB-type pigments were investigated using thermogravimetry. The thermoanalytical data were deconvoluted into individual component reaction steps using an empirical kDa technique based on a cumulative kinetic equation that considers the contribution of each reaction step to the overall thermal decomposition. By comparing the kDa results for the thermal decomposition of the composites with those for the decomposition of pure palygorskite and sepiolite, the thermal decomposition steps for the incorporated organic dyes were extracted from the multistep thermal decompositions of the MB-type pigments. Finally, the thermal stabilities of MB-type pigments comprising different clay minerals and organic dyes were compared using the kinetic results extracted for the reaction step associated with the decomposition of the organic dyes.

Kinetic Analysis of Thermal Decomposition of Inorganic Solids and Polymer by Sample Controlled Thermal Analysis and Kinetic Deconvolution Analysis

Kinetic Analysis of Thermal Decomposition of Inorganic Solids and Polymer by Sample Controlled Thermal Analysis and Kinetic Deconvolution Analysis

Thermal Decomposition of Maya Blue: Extraction of Indigo Thermal Decomposition Steps from a Multistep Heterogeneous Reaction Using a Kinetic Deconvolution Analysis.

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.

Thermal behavior of perlite concrete used in a sodium-cooled fast reactor

In this study, the thermal behavior of the perlite concrete used in a sodium-cooled fast reactor was investigated for obtaining information on a plant simulation system for safety assessment. The thermal stability and kinetic behavior of multistep thermally induced processes of perlite concrete were examined using thermoanalytical techniques and other complementary methods. The partially overlapping thermal decomposition process comprising seven reaction steps was characterized by kinetic deconvolution analysis based on a cumulative kinetic equation by determining the contribution and all kinetic parameters for each component reaction step. The thermal decomposition product was a mixture of amorphous and crystalline phases located in a CaO-rich region in the SiO2–CaO phase diagram. The softening or melting of the decomposition product was initiated at approximately 1520 K. The significance and reliability of the results obtained were discussed on the premise of their practical uses for the safety assessment.

Comparative study on the thermal behavior of structural concretes of sodium-cooled fast reactor

Thermal behaviors of two different siliceous concretes used in a sodium-cooled fast reactor were comparatively investigated in a temperature range from room temperature to 1900 K for obtaining fundamental information required for establishing a plant simulation system for safety assessment under a postulated accidental condition. Silica crystals and Portland cement were identified as the major component of the aggregate and cement portions of the concrete samples, respectively. The thermal decomposition of the cement portion exhibited partially overlapping multistep reaction comprising the thermal dehydration, thermal decomposition processes of Ca(OH)2 and carbonate compounds including CaCO3. TG–DTG curves recorded for the multistep thermal decomposition process of the cement portion were analyzed using the kinetic deconvolution analysis, and the contributions and kinetic parameters of each reaction step were determined. The kinetics of comparable reaction steps between two samples were practically identical, while the difference between the samples was found in the content ratio of Ca(OH)2/CaCO3. The melting behavior of the siliceous concretes was revealed by the complementary interpretation of TG–DTA curves and the morphological observation of the sample heated to different temperatures. The softening and melting behaviors of the siliceous concretes initially occurred in the thermal decomposition product of the cement portion at a temperature range of 1400–1600 K. The subsequent melting behavior of the aggregate portion that occurs at a higher temperature was different between the samples, owing to the different compositions of the aggregates and the possible interaction of the aggregate with the molten cement portion.

Characterization of Carbon/Carbon Composites by Kinetic Deconvolution Analysis for a Thermal Oxidation Process: An Examination Using a Series of Mechanical Pencil Leads

The thermal behaviors of carbon/carbon (C/C) composites in flowing air were investigated on the basis of mechanical pencil leads with different hardness values and diameters as a model system. Two separated mass-loss processes were observed during heating the mechanical pencil leads in air, which are attributed to the evaporation–decomposition of an impregnation agent and the subsequent thermal oxidation of the residual C/C composite. The thermal behaviors were invariant among the mechanical pencil leads with different diameters, but they systematically changed with hardness. Variations in the thermal behaviors can be quantified by the mass-loss value during the evaporation–decomposition of the impregnation agent, in addition to the kinetic deconvolution analysis that was applied to the multistep thermal oxidation process of carbon components with different reactivities. These results correlate the thermal behavior with the compositional and structural characteristics of C/C composites, which can be usefu...

Kinetic characterization of multistep thermal oxidation of carbon/carbon composite in flowing air

Thermal oxidation of carbon/carbon composites in an oxidizing atmosphere is a multistep process regulated by the intrinsic heterogeneity of the solid–gas reaction, the additional heterogeneity of the compositional and structural characteristics of the composite, and how these two properties change as the reaction progresses. By focusing on the overlapping features of the component reaction steps, the kinetic characterization of the multistep kinetic process was studied to reveal the correlation between the thermal oxidation behavior and the compositional and structural characteristics of carbon/carbon composites. Using commercially available mechanical pencil leads as a typical model system for a carbon/carbon composite, the thermal behaviors of two different leads manufactured by different companies were investigated comparatively via thermoanalytical techniques and morphological observations. On the basis of a reaction model considering the different reactivities of the main (graphite) and secondary (carbonized polymer) carbon components, the kinetic features of two partially overlapping reaction steps were revealed via a kinetic deconvolution analysis of the thermoanalytical data for the thermal oxidation process. The kinetic results were correlated with the compositional and structural characteristics of carbon/carbon composites using morphological observations of the partially reacted samples. Herein, the practical usefulness of the kinetic analysis in characterizing carbon/carbon composites is discussed.

Kinetic approach to multistep thermal behavior of Ag2CO3–graphite mixtures: Possible formation of intermediate solids with Ag2O–Ag and Ag2CO3–Ag core–shell structures

This study aimed to investigate the contribution of carbothermal reduction to the overall thermal decomposition process of different Ag2CO3 samples in Ag2CO3–graphite mixtures and the possible formation of Ag2O–Ag and Ag2CO3–Ag core–shell structures as intermediate compounds. Distinguishable contribution of the carbothermal reduction process was observed during the second mass loss process of the thermal decomposition. The second mass loss process was characterized by two partially overlapping reaction steps: (i) the carbothermal reduction of surface Ag2O; and (ii) subsequent thermal decomposition of bulk Ag2O or Ag2CO3. The overlapping features of the carbothermal reduction and thermal decomposition processes were analyzed via the kinetic deconvolution analysis. The present results provide us with fundamental information for preparing possible functional Ag compound materials with Ag2O–Ag and Ag2CO3–Ag core–shell structures in a controlled manner during the thermal decomposition of Ag2CO3.

Exothermic Behavior of Thermal Decomposition of Sodium Percarbonate: Kinetic Deconvolution of Successive Endothermic and Exothermic Processes.

This study focused on the kinetic modeling of the thermal decomposition of sodium percarbonate (SPC, sodium carbonate-hydrogen peroxide (2/3)). The reaction is characterized by apparently different kinetic profiles of mass-loss and exothermic behavior as recorded by thermogravimetry and differential scanning calorimetry, respectively. This phenomenon results from a combination of different kinetic features of the reaction involving two overlapping mass-loss steps controlled by the physico-geometry of the reaction and successive endothermic and exothermic processes caused by the detachment and decomposition of H2O2(g). For kinetic modeling, the overall reaction was initially separated into endothermic and exothermic processes using kinetic deconvolution analysis. Then, both of the endothermic and exothermic processes were further separated into two reaction steps accounting for the physico-geometrically controlled reaction that occurs in two steps. Kinetic modeling through kinetic deconvolution analysis clearly illustrates the appearance of the net exothermic effect is the result of a slight delay of the exothermic process to the endothermic process in each physico-geometrically controlled reaction step. This demonstrates that kinetic modeling attempted in this study is useful for interpreting the exothermic behavior of solid-state reactions such as the oxidative decomposition of solids and thermal decomposition of oxidizing agent.

DATforDCEMRI: AnRPackage for Deconvolution Analysis and Visualization of DCE-MRI Data

Numerical deconvolution is a powerful mathematical operation that can be used to extract the impulse response function of a linear, time-invariant system. We have found this method to be useful for preliminary analysis of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) data, capable of quickly producing voxel-wise parametric maps describing the heterogeneity of contrast agent kinetics over the entire field of view, typically comprising tens of thousands of voxels. The statistical programming language R is well suited for this type of analysis and when combined with LATEX, via Sweave, allows one to perform all calculations and generate a report with a single script. The purpose of this manuscript is to describe the R package DATforDCEMRI, a Deconvolution Analysis Tool for DCE-MRI contrast agent concentration vs. time data, which allows the user to perform kinetic deconvolution analysis and visualize/explore the resulting voxel-wise parametric maps and associated data.