scholarly journals Characterization of PVC/MWCNTs Nanocomposite: Solvent Blend

2020 ◽  
Vol 27 (1) ◽  
pp. 55-64 ◽  
Author(s):  
Abdullah F. Al Naim ◽  
Huda AlFannakh ◽  
Samia Arafat ◽  
S. S. Ibrahim
Keyword(s):  
Thermal Properties ◽  
Kinetic Method ◽  
Multiwall Carbon Nanotubes ◽  
Isothermal Kinetics ◽  
Hysteresis Curve ◽  
Heating Rates ◽  
Model Free ◽  
Main Decomposition ◽  
Apparent Activation Energies ◽  
The Stability

AbstractPolyvinyl Vinyl Chloride (PVC) multiwall carbon nanotubes (MWCNTs) nanocomposite flexible films were prepared using the solvent blend technique. Chloroform (CHCl3) and tetrahydrofuran ((CH2)4O) were used as solvents for MWCNTs and PVC, respectively. The effect of the solvents’ blend on electrical, optical and thermal properties of PVC/MWCNTs were investigated. The results of the Raman spectrum showed that all the characteristic bands of PVC polymer have a slight shift due to addition of MWCNTs. Electrical results showed that the nanocomposite samples with chloroform volume ratios of 10% and 25% had nearly the same conductivity. This is attributed to the formation of the MWCNTs network, which assisted in electrical conductivity. The I-V hysteresis curve decreases as the temperature increases and as it approaches the glass transition temperature. The non-isothermal kinetics analysis for PVC and PVC/MWCNTs were investigated by Thermogravimetry Analysis (TGA) using the model-free kinetic method. The non-isothermal measurements were carried out at five heating rates of 5 to 40∘C/min. The results show that the main decomposition process has constant apparent activation energies for all samples. The use of the bi-solvent method has improved the dispersion of untreated MWCNTs, and this has been reflected on the stability of both electrical and thermal properties.

SOĞUK HADDELENMİŞ AA3105 VE AA5005 LEVHALARIN DSC ANALİZİ İLE YENİDEN KRİSTALLENME KİNETİĞİ

2021 ◽  
Vol 8 (17) ◽  
pp. 80-85
Author(s):  
Atae RAOUGUI ◽  
Ion GRECU ◽  
Volkan Murat YILMAZ ◽  
Kenan YILDIZ
Keyword(s):  
Differential Scanning Calorimetry ◽  
Aluminum Alloy ◽  
Activation Energies ◽  
Isothermal Kinetics ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Recrystallization Kinetics ◽  
Model Free ◽  
Cold Rolled ◽  
Kinetics Of

In this study, the non-isothermal recrystallization kinetics of cold rolled AA3105 and AA5005 aluminum alloy sheets obtained from ASAŞ Aluminum located in Akyazı-Sakarya was studied by using differential scanning calorimetry (DSC). The non – isothermal kinetics was performed by using Kissenger, Boswell, Ozawa and Starink methods known as model – free methods. The recrystallization temperatures on DSC graphics at different heating rates (β) were deduced and the activation energies were calculated from the slopes from Y – 1/T diagrams. Y is ln(β/T2) for Kissenger, ln(β/T) for Boswell, ln(β) for Ozawa and ln(β/T1.92) for Starink. The results showed that the activation energies of recrystallization are in the range of 194 – 206 kJ/mol for cold rolled AA5005 sheet and in the range of 235 – 257 kJ/mol for cold rolled AA3105 sheet, according to four non-isothermal kinetics model.

scholarly journals Non-isothermal kinetics: best-fitting empirical models instead of model-free methods

2019 ◽  
Vol 142 (2) ◽  
pp. 1043-1054 ◽  
Author(s):  
Gábor Várhegyi ◽  
Liang Wang ◽  
Øyvind Skreiberg
Keyword(s):  
Least Squares ◽  
Wood Sample ◽  
Empirical Models ◽  
Isothermal Kinetics ◽  
Heating Rates ◽  
Method Of Least Squares ◽  
Model Free ◽  
Preceding Work ◽  
Best Fitting ◽  
Constant Heating

AbstractThe isoconversional (or model-free) methods cannot provide meaningful kinetic description for most samples in thermal analysis. Nevertheless, they can serve as empirical models. A usable empirical model should describe well the observed data and should be suitable for predictions, too. For this purpose, the functions in the isoconversional kinetic equation were parametrized, and the parameters were determined by the method of least squares. This procedure ensures that the data calculated from the model would be close to the experimental data. The present work supplemented a preceding work of Várhegyi (Energy and Fuels 33:2348–2358, 2019) by further considerations and by various evaluations on the TGA curves of a wood sample. The prediction capabilities of the models were also tested. It was found that an evaluation based on three experiments with constant heating rates could predict well two further experiments with stepwise temperature programs. Furthermore, a modification of the model was proposed and examined. The aim of this modification was to improve the fit quality without increasing the number of parameters in the least-squares procedure.

Thermo-catalytic decomposition of polystyrene waste: Comparative analysis using different kinetic models

2019 ◽  
Vol 38 (2) ◽  
pp. 202-212 ◽  
Author(s):  
Ghulam Ali ◽  
Jan Nisar ◽  
Munawar Iqbal ◽  
Afzal Shah ◽  
Mazhar Abbas ◽  
...  
Keyword(s):  
Activation Energy ◽  
Copper Oxide ◽  
Solid Waste ◽  
Thermodynamic Parameters ◽  
Model Fitting ◽  
Catalytic Decomposition ◽  
Decomposition Reaction ◽  
Inert Atmosphere ◽  
Heating Rates ◽  
Model Free

Due to a huge increase in polymer production, a tremendous increase in municipal solid waste is observed. Every year the existing landfills for disposal of waste polymers decrease and the effective recycling techniques for waste polymers are getting more and more important. In this work pyrolysis of waste polystyrene was performed in the presence of a laboratory synthesized copper oxide. The samples were pyrolyzed at different heating rates that is, 5°Cmin−1, 10°Cmin−1, 15°Cmin−1 and 20°Cmin−1 in a thermogravimetric analyzer in inert atmosphere using nitrogen. Thermogravimetric data were interpreted using various model fitting (Coats–Redfern) and model free methods (Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose and Friedman). Thermodynamic parameters for the reaction were also determined. The activation energy calculated applying Coats–Redfern, Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose and Friedman models were found in the ranges 105–148.48 kJmol−1, 99.41–140.52 kJmol−1, 103.67–149.15 kJmol−1 and 99.93–141.25 kJmol−1, respectively. The lowest activation energy for polystyrene degradation in the presence of copper oxide indicates the suitability of catalyst for the decomposition reaction to take place at lower temperature. Moreover, the obtained kinetics and thermodynamic parameters would be very helpful in determining the reaction mechanism of the solid waste in a real system.

scholarly journals Structural, elastic, electronic and thermal properties of InAs: A study of functional density

2017 ◽  
Vol 26 (46) ◽  
Author(s):  
Víctor Mendoza-Estrada ◽  
Melissa Romero-Baños ◽  
Viviana Dovale-Farelo ◽  
William López-Pérez ◽  
Álvaro González-García ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Density Functional ◽  
Experimental Studies ◽  
Debye Model ◽  
Band Gap Energy ◽  
Functional Theory ◽  
Zinc Blende ◽  
The Density Functional Theory ◽  
The Stability ◽  
Experimental Values

In this research, first-principles calculations were carried out within the density functional theory (DFT) framework, using LDA and GGA, in order to study the structural, elastic, electronic and thermal properties of InAs in the zinc-blende structure. The results of the structural properties (a, B0, ) agree with the theoretical and experimental results reported by other authors. Additionally, the elastic properties, the elastic constants (C11, C12 and C44), the anisotropy coefficient (A) and the predicted speeds of the sound ( , , and ) are in agreement with the results reported by other authors. In contrast, the shear modulus (G), the Young's modulus (Y) and the Poisson's ratio (v) show some discrepancy with respect to the experimental values, although, the values obtained are reasonable. On the other hand, it is evident the tendency of the LDA and GGA approaches to underestimate the value of the band-gap energy in semiconductors. The thermal properties (V, , θD yCV) of InAs, calculated using the quasi-harmonic Debye model, are slightly sensitive as the temperature increases. According to the stability criteria and the negative value of the enthalpy of formation, InAs is mechanically and thermodynamically stable. Therefore, this work can be used as a future reference for theoretical and experimental studies based on InAs.

scholarly journals Pyrolysis Kinetic Properties of Thermal Insulation Waste Extruded Polystyrene by Multiple Thermal Analysis Methods

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5595
Author(s):  
Ang Li ◽  
Wenlong Zhang ◽  
Juan Zhang ◽  
Yanming Ding ◽  
Ru Zhou
Keyword(s):  
Reaction Mechanism ◽  
Thermal Insulation ◽  
Conversion Rate ◽  
Model Fitting ◽  
Pso Algorithm ◽  
Energy Utilization ◽  
Kinetic Properties ◽  
Insulation Material ◽  
Heating Rates ◽  
Model Free

Extruded polystyrene (XPS) is a thermal insulation material extensively applied in building systems. It has attracted much attention because of outstanding thermal insulation performance, obvious flammability shortcoming and potential energy utilization. To establish the reaction mechanism of XPS’s pyrolysis, thermogravimetric experiments were performed at different heating rates in nitrogen, and multiple methods were employed to analyze the major kinetics of pyrolysis. More accurate kinetic parameters of XPS were estimated by four common model-free methods. Then, three model-fitting methods (including the Coats-Redfern, the iterative procedure and masterplots method) were used to establish the kinetic model. Since the kinetic models established by the above three model-fitting methods were not completely consistent based on different approximations, considering the effect of different approximates on the model, the reaction mechanism was further established by comparing the conversion rate based on the model-fitting methods corresponding to the possible reaction mechanisms. Finally, the accuracy of the above model-fitting methods and Particle Swarm Optimization (PSO) algorithm were compared. Results showed that the reaction function g(α) = (1 − α)−1 − 1 might be the most suitable to characterize the pyrolysis of XPS. The conversion rate calculated by masterplots and PSO methods could provide the best agreement with the experimental data.

Influence of the multiwall carbon nanotubes on the thermal properties of the Fe–Cu nanocomposites

2020 ◽  
Vol 816 ◽  
pp. 152525
Author(s):  
M.C. Bouleklab ◽  
S. Hamamda ◽  
Y. Naoui ◽  
S. Nedilko ◽  
T. Avramenko ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Thermal Properties ◽  
Multiwall Carbon Nanotubes ◽  
Multiwall Carbon

scholarly journals Adaptive Model-Free Coupling Controller Design for Multi-Axis Motion Systems

2020 ◽  
Vol 10 (10) ◽  
pp. 3592
Author(s):  
Bo-Sheng Chen ◽  
Ching-Hung Lee
Keyword(s):  
Controller Design ◽  
Uncertain System ◽  
Contour Error ◽  
Nonlinear Phenomena ◽  
Nonlinear Phenomenon ◽  
Adaptive Model ◽  
Model Free ◽  
Fuzzy Neural ◽  
Adaptive Coupling ◽  
The Stability

In this study, we introduce an adaptive model-free coupling controller while using recurrent fuzzy neural network (RFNN) for multi-axis system to minimize the contour error. The proposed method can be applied to linear or nonlinear multi-axis motion control systems following desired paths. By the concept of cross-coupling control (CCC), multi-axis system is transferred into a nonlinear time-varying system due to the time-dependent coordinate transformation; tangential, normal, and bi-normal components of desired contour. Herein, we propose a model-free adaptive coupling controller design approach for multi-axis linear motor system with uncertainty and nonlinear phenomena. RFNN establishes the corresponding adaptive coupling controller to treat the uncertain system with nonlinear phenomenon. The stability of closed-loop system is guaranteed by the Lyapunov method and the adaptation of RFNN is also obtained. Simulation results are introduced in order to illustrate the effectiveness.

scholarly journals Model-Free Stochastic Collocation for an Arbitrage-Free Implied Volatility, Part II

Risks ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 30
Author(s):  
Fabien Le Floc’h ◽  
Cornelis Oosterlee
Keyword(s):  
Implied Volatility ◽  
Initial Guess ◽  
Stochastic Collocation ◽  
Option Prices ◽  
Spline Collocation ◽  
Model Free ◽  
Free Interpolation ◽  
Collocation Technique ◽  
Interpolation Technique ◽  
The Stability

This paper explores the stochastic collocation technique, applied on a monotonic spline, as an arbitrage-free and model-free interpolation of implied volatilities. We explore various spline formulations, including B-spline representations. We explain how to calibrate the different representations against market option prices, detail how to smooth out the market quotes, and choose a proper initial guess. The technique is then applied to concrete market options and the stability of the different approaches is analyzed. Finally, we consider a challenging example where convex spline interpolations lead to oscillations in the implied volatility and compare the spline collocation results with those obtained through arbitrage-free interpolation technique of Andreasen and Huge.

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