scholarly journals Thermal Analysis of a Metal–Organic Framework ZnxCo1-X-ZIF-8 for Recent Applications

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 4051
Author(s):  
Moustafa Ahmed ◽  
Yas M Al-Hadeethi ◽  
Ahmed Alshahrie ◽  
Arwa T Kutbee ◽  
Essam R. Shaaban ◽  
...  
Keyword(s):  
Metal Organic Framework ◽  
Combustion Process ◽  
Deep Understanding ◽  
Active Phase ◽  
Decomposition Process ◽  
Dynamical Analysis ◽  
Zeolitic Imidazolate Frameworks ◽  
Heating Rates ◽  
Exponential Factor ◽  
Pyrolysis Mechanism

Zeolitic imidazolate frameworks (ZIFs) are interesting materials for use in several aspects: energy storage material, gas sensing, and photocatalysis. The thermal stability and pyrolysis process are crucial in determining the active phase of the material. A deep understanding of the pyrolysis mechanism is in demand. Therefore, the thermodynamics and combustion process with different heating rates was examined, and the kinetic parameters were computed employing thermogravimetric tests. Based on the TG analysis of combustion, pyrolysis moves to the high-temperature region with an increase in heating rate. The decomposition process can be separated into the dehydration (300–503 K) and the pyrolysis reaction (703–1100 K). Three points of the decomposition process are performed by dynamical analysis owing to shifts of slopes, but the combustion process has only one stage. The Zeolitic imidazolate framework’s structure properties were examined using TDDFT-DFT/DMOl3 simulation techniques. Dynamical parameters, for instance, the possible mechanism, the pre-exponential factor, and the apparent activation energy are obtained through comparison using the Kissinger formula. The thermodynamics analysis of the Zn1-xCox-ZIF-8 materials is an effective way to explore the temperature influence on the process of pyrolysis, which can benefit several environment purifications, photocatalyst, and recent applications.

Kinetic study of wood chips decomposition by TGA

2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Lukáš Gašparovič ◽  
Zuzana Koreňová ◽  
Ľudovít Jelemenský
Keyword(s):  
Activation Energy ◽  
Kinetic Parameters ◽  
Isoconversional Method ◽  
Nitrogen Atmosphere ◽  
Decomposition Process ◽  
Wood Chips ◽  
Water Evaporation ◽  
Heating Rates ◽  
Exponential Factor ◽  
Decomposition Processes

AbstractPyrolysis of a wood chips mixture and main wood compounds such as hemicellulose, cellulose and lignin was investigated by thermogravimetry. The investigation was carried out in inert nitrogen atmosphere with temperatures ranging from 20°C to 900°C for four heating rates: 2 K min−1, 5 K min−1, 10 K min−1, and 15 K min−1. Hemicellulose, cellulose, and lignin were used as the main compounds of biomass. TGA and DTG temperature dependencies were evaluated. Decomposition processes proceed in three main stages: water evaporation, and active and passive pyrolysis. The decomposition of hemicellulose and cellulose takes place in the temperature range of 200–380°C and 250–380°C, while lignin decomposition seems to be ranging from 180°C up to 900°C. The isoconversional method was used to determine kinetic parameters such as activation energy and pre-exponential factor mainly in the stage of active pyrolysis and partially in the passive stage. It was found that, at the end of the decomposition process, the value of activation energy decreases. Reaction order does not have a significant influence on the process because of the high value of the pre-exponential factor. Obtained kinetic parameters were used to calculate simulated decompositions at different heating rates. Experimental data compared with the simulation ones were in good accordance at all heating rates. From the pyrolysis of hemicellulose, cellulose, and lignin it is clear that the decomposition process of wood is dependent on the composition and concentration of the main compounds.

scholarly journals Co-Combustion Studies of Low-Rank Coal and Refuse-Derived Fuel: Performance and Reaction Kinetics

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3796
Author(s):  
Mudassar Azam ◽  
Asma Ashraf ◽  
Saman Setoodeh Setoodeh Jahromy ◽  
Sajjad Miran ◽  
Nadeem Raza ◽  
...  
Keyword(s):  
Activation Energy ◽  
Waste Management ◽  
Energy Demand ◽  
Power Plants ◽  
Combustion Process ◽  
Isoconversional Methods ◽  
Low Rank ◽  
Heating Rates ◽  
Average Activation Energy ◽  
Refuse Derived Fuel

In connection to present energy demand and waste management crisis in Pakistan, refuse-derived fuel (RDF) is gaining importance as a potential co-fuel for existing coal fired power plants. This research focuses on the co-combustion of low-quality local coal with RDF as a mean to reduce environmental issues in terms of waste management strategy. The combustion characteristics and kinetics of coal, RDF, and their blends were experimentally investigated in a micro-thermal gravimetric analyzer at four heating rates of 10, 20, 30, and 40 °C/min to ramp the temperature from 25 to 1000 °C. The mass percentages of RDF in the coal blends were 10%, 20%, 30%, and 40%, respectively. The results show that as the RDF in blends increases, the reactivity of the blends increases, resulting in lower ignition temperatures and a shift in peak and burnout temperatures to a lower temperature zone. This indicates that there was certain interaction during the combustion process of coal and RDF. The activation energies of the samples were calculated using kinetic analysis based on Kissinger–Akahira–Sunnose (KAS) and Flynn–Wall–Ozawa (FWO), isoconversional methods. Both of the methods have produced closer results with average activation energy between 95–121 kJ/mol. With a 30% refuse-derived fuel proportion, the average activation energy of blends hit a minimum value of 95 kJ/mol by KAS method and 103 kJ/mol by FWO method.

scholarly journals Lifetime predictions of non-ionic and ionic biopolymers: kinetic studies by non-isothermal thermogravimetric analysis

2021 ◽  
Author(s):  
Martina Maria Calvino ◽  
Lorenzo Lisuzzo ◽  
Giuseppe Cavallaro ◽  
Giuseppe Lazzara ◽  
Stefana Milioto
Keyword(s):  
Degradation Kinetics ◽  
Kinetic Studies ◽  
Ionic Polymers ◽  
Heating Rates ◽  
Exponential Factor ◽  
Master Plot ◽  
Plot Analysis ◽  
Sustainable Polymers ◽  
Master Plot Analysis

AbstractIn this paper, films based on sustainable polymers with variable charge have been investigated by non-isothermal thermogravimetry in order to predict their lifetime, which is a key parameter for their potential use in numerous technological and biomedical applications. Specifically, chitosan has been selected as positively charged biopolymer, while alginate has been chosen as negatively charged biopolymer. Among non-ionic polymers, methylcellulose has been investigated. Thermogravimetric measurements at variable heating rates (5, 10, 15 and 20 °C min−1) have been performed for all the polymers to study their degradation kinetics by using isoconversional procedures combined with ‘Master plot’ analyses. Both integral (KAS and Starink methods) and differential (Friedman method) isoconversional procedures have shown that chitosan possesses the highest energetic barrier to decomposition. Based on the Master plot analysis, the decomposition of ionic polymers can be described by the R2 kinetic model (contracted cylindrical geometry), while the degradation of methylcellulose reflects the D2 mechanism (two-dimensional diffusion). The determination of both the decomposition mechanism and the kinetic parameters (activation energy and pre-exponential factor) has been used to determine the decay time functions of the several biopolymers. The obtained insights can be helpful for the development of durable films based on sustainable polymers with variable electrostatic characteristics. Graphical abstract

scholarly journals Isothermal Kinetic Analysis of the Thermal Decomposition of Wood Chips from an Apple Tree

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 195
Author(s):  
Ivan Vitázek ◽  
Martin Šotnar ◽  
Stella Hrehová ◽  
Kristína Darnadyová ◽  
Jan Mareček
Keyword(s):  
Thermal Decomposition ◽  
Apple Tree ◽  
Combustion Process ◽  
Reaction Model ◽  
Wood Chips ◽  
Small Scale ◽  
Exponential Factor ◽  
Air Atmosphere ◽  
First Order Chemical Reaction ◽  
Isothermal Kinetic

The thermal decomposition of wood chips from an apple tree is studied in a static air atmosphere under isothermal conditions. Based on the thermogravimetric analysis, the values of the apparent activation energy and pre-exponential factor are 34 ± 3 kJ mol−1 and 391 ± 2 min−1, respectively. These results have also shown that this process can be described by the rate of the first-order chemical reaction. This reaction model is valid only for a temperature range of 250–290 °C, mainly due to the lignin decomposition. The obtained results are used for kinetic prediction, which is compared with the measurement. The results show that the reaction is slower at higher values of degree of conversion, which is caused by the influence of the experimental condition. Nevertheless, the obtained kinetic parameters could be used for the optimization of the combustion process of wood chips in small-scale biomass boilers.

Mechanisms and kinetics of initial pyrolysis and combustion reactions of 1,1-diamino-2,2-dinitroethylene from density functional tight-binding molecular dynamics simulations

2019 ◽  
Vol 97 (11) ◽  
pp. 795-804 ◽  
Author(s):  
Dong Xiang ◽  
Weihua Zhu
Keyword(s):  
Activation Energy ◽  
Molecular Dynamics ◽  
Density Functional ◽  
Tight Binding ◽  
Combustion Process ◽  
Exponential Factor ◽  
Three Stages ◽  
Dynamics Simulations ◽  
Combustion Processes ◽  
Kinetics Of

The density functional tight-binding molecular dynamics approach was used to study the mechanisms and kinetics of initial pyrolysis and combustion reactions of isolated and multi-molecular FOX-7. Based on the thermal cleavage of bridge bonds, the pyrolysis process of FOX-7 can be divided into three stages. However, the combustion process can be divided into five decomposition stages, which is much more complex than the pyrolysis reactions. The vibrations in the mean temperature contain nodes signifying the formation of new products and thereby the transitions between the various stages in the pyrolysis and combustion processes. Activation energy and pre-exponential factor for the pyrolysis and combustion reactions of FOX-7 were obtained from the kinetic analysis. It is found that the activation energy of its pyrolysis and combustion reactions are very low, making both take place fast. Our simulations provide the first atomic-level look at the full dynamics of the complicated pyrolysis and combustion process of FOX-7.

scholarly journals Vertical profiles of submicron aerosol single scattering albedo over the Indian region immediately before monsoon onset and during its development: research from the SWAAMI field campaign

2020 ◽  
Vol 20 (6) ◽  
pp. 4031-4046
Author(s):  
Mohanan R. Manoj ◽  
Sreedharan K. Satheesh ◽  
Krishnaswamy K. Moorthy ◽  
Hugh Coe
Keyword(s):  
Active Phase ◽  
Single Scattering ◽  
Monsoon Onset ◽  
Single Scattering Albedo ◽  
Transfer Model ◽  
Heating Rates ◽  
Atmospheric Measurements ◽  
Middle Troposphere ◽  
Submicron Aerosol ◽  
Aerosol Absorption

Abstract. Vertical structures of aerosol single scattering albedo (SSA), from near the surface through the free troposphere, have been estimated for the first time at distinct geographical locations over the Indian mainland and adjoining oceans, using in situ measurements of aerosol scattering and absorption coefficients aboard the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft during the South West Asian Aerosol Monsoon Interactions (SWAAMI) campaign from June to July 2016. These are used to examine the spatial variation of SSA profiles and also to characterize its transformation from just prior to the onset of Indian Summer Monsoon (June 2016) to its active phase (July 2016). Very strong aerosol absorption, with SSA values as low as 0.7, persisted in the lower altitudes (<3 km) over the Indo-Gangetic Plains (IGP), prior to the monsoon onset, with a west-to-east gradient; lower values occurred in the north-western arid regions, peaking in the central IGP and somewhat decreasing towards the eastern end. During the active phase of the monsoon, the SSA is found to increase remarkably, indicating far less absorption. Nevertheless, significant aerosol absorption persisted in the lower and middle troposphere over the IGP. Inputting these SSA and extinction profiles into a radiative transfer model, we examined the effects of using height-resolved information in estimating atmospheric heating rates due to aerosols, over similar estimates made using a single columnar value. It was noted that use of a single SSA value leads to an underestimation (overestimation) of the heating rates over regions with low (high) SSA, emphasizing the importance of height-resolved information. Further, the use of realistic profiles showed significant heating of the atmosphere by submicron aerosol absorption at the middle troposphere, which may have strong implications for clouds and climate.

scholarly journals Curing Kinetic Parameters of Epoxy Composite Reinforced with Mallow Fibers

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3939 ◽  
Author(s):  
Lucio Fabio Cassiano Nascimento ◽  
Fernanda Santos da Luz ◽  
Ulisses Oliveira Costa ◽  
Fábio de Oliveira Braga ◽  
Édio Pereira Lima Júnior ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Industrial Process ◽  
Diglycidyl Ether ◽  
Response Surfaces ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Curing Kinetic ◽  
Technological Tool

Knowledge about the curing behavior of a thermosetting resin and its composites includes the determination of kinetic parameters and constitutes an important scientific and technological tool for industrial process optimization. In the present work, the differential scanning calorimetry (DSC) technique was used to determine several curing parameters for pure epoxy and its composite reinforced with 20 vol % mallow fibers. Analyses were performed with heating rates of 5, 7.5, and 10 °C/min, as per the ASTM E698 standard. The kinetic related parameters, that is, activation energy (E), Avrami’s pre-exponential factor (Z), and mean time to reach 50% cure (t½), were obtained for the materials, at temperatures ranging from 25 to 100 °C. Response surfaces based on the mathematical relationship between reaction time, transformed fraction, and temperature were provided for optimization purposes. The results showed that the average curing time used for the production of diglycidyl ether of bisphenol A/triethylenetetramine (DGEBA/TETA) epoxy systems or their composites reinforced with natural mallow fibers can be considerably reduced as the temperature is increased up to a certain limit.

Studies on the Thermal Decomposition Kinetic of an Nitrate Ester

2012 ◽  
Vol 182-183 ◽  
pp. 1575-1580 ◽  
Author(s):  
Juan Wang ◽  
Da Bin Liu ◽  
Xin Li Zhou
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Decomposition Mechanism ◽  
Thermal Decomposition Mechanism ◽  
Decomposition Kinetic ◽  
Heating Rates ◽  
Exponential Factor ◽  
Nitrate Ester ◽  
Dynamic Function ◽  
Thermal Decomposition Kinetic

The certain nitrate ester explosive has been tested by TG at the heating rates of 10, 15, 20, 25K•min-1. Basing on the TG experiment results the thermal decomposition activation energy has been calculated by the methods of Ozawa, KAS and iteration. And the thermal decomposition mechanism function of the explosive with 38 kinds of dynamic function was deduced by the method of integration. The results show that the thermal decomposition mechanism of the nitrate ester is chemical reaction mechanism. The thermal decomposition kinetic parameters such as average activation energy Ea and pre-exponential factor A are 133.23×103 J•mol-1 and 3.191×107 s-1 respectively.

Cure Kinetic Behavior of 191# Unsaturated Polyester Resin Used in Advanced Composites

2006 ◽  
Vol 326-328 ◽  
pp. 1271-1274 ◽  
Author(s):  
Mei Yang ◽  
Shi Lin Yan ◽  
Mei Liu
Keyword(s):  
Polyester Resin ◽  
Unsaturated Polyester ◽  
Cure Kinetics ◽  
Unsaturated Polyester Resin ◽  
Kinetic Properties ◽  
Heating Rates ◽  
Cure Reaction ◽  
Exponential Factor ◽  
Maximum Reaction Rate ◽  
Cure Kinetic

The cure kinetic properties of 191# resin was studied by means of the differential scanning calorimeter (DSC) data. Dynamic DSC scanning at four different heating rates (5, 10, 15 and 20/min) are employed to investigate the cure kinetics. DSC curves show that there are two exothermal peaks. Kissinger’s method is applied to processing the data. The activation energy E and pre-exponential factor A were gained by linear regress and the cure kinetics model was developed. Based on T − β method, the temperatures of cure reaction beginning, maximum reaction rate and reaction ending were obtained. These will help to process designing of unsaturated polyester resin used in advanced composite materials.

scholarly journals MOF-Derived Co3O4 Polyhedrons as Efficient Polysulfides Barrier on Polyimide Separators for High Temperature Lithium–sulfur Batteries

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1574 ◽  
Author(s):  
Zhou ◽  
Li ◽  
Fang ◽  
Zhao ◽  
Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Ionic Conductivity ◽  
Inorganic Compounds ◽  
Metal Organic Framework ◽  
Zeolitic Imidazolate Frameworks ◽  
Lithium Sulfur Batteries ◽  
Lithium Dendrites ◽  
Small Primary ◽  
And Performance ◽  
Lithium Sulfur

The incorporation of highly polarized inorganic compounds in functional separators is expected to alleviate the high temperature safety- and performance-related issues for promising lithium–sulfur batteries. In this work, a unique Co3O4 polyhedral coating on thermal-stable polyimide (PI) separators was developed by a simple one-step low-temperature calcination method utilizing metal-organic framework (MOF) of Co-based zeolitic-imidazolate frameworks (ZIF-Co) precursors. The unique Co3O4 polyhedral structures possess several structural merits including small primary particle size, large pore size, rich grain boundary, and high ionic conductivity, which endow the ability to adequately adsorb dissolved polysulfides. The flexible-rigid lithium-lanthanum-zirconium oxide-poly(ethylene oxide) (LLZO-PEO) coating has been designed on another side of the polyimide non-woven membranes to inhibit the growth of lithium dendrites. As a result, the as-fabricated Co3O4/polyimide/LLZO-PEO (Co3O4/PI/LLZO) composite separators displayed fair dimensional stability, good mechanical strength, flame retardant properties, and excellent ionic conductivity. More encouragingly, the separator coating of Co3O4 polyhedrons endows Li–S cells with unprecedented high temperature properties (tested at 80 °C), including rate performance 620 mAh g−1 at 4.0 C and cycling stability of 800 mAh g−1 after 200 cycles—much better than the state-of-the-art results. This work will encourage more research on the separator engineering for high temperature operation.

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