scholarly journals Crystallization kinetics of poly (butylene adipate terephthalate) in biocomposite with coconut fiber

2019 ◽  
Vol 24 (3) ◽  
Author(s):  
Jokdérlea Correa Sousa ◽  
Salim Abdelnor Arruda ◽  
Juliana Cisneiros Lima ◽  
Renate Maria Ramos Wellen ◽  
Eduardo Luis Canedo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Crystallization Kinetic ◽  
Model Fitting ◽  
Quantitative Information ◽  
Melt Crystallization ◽  
Coconut Fiber ◽  
Scanning Calorimetry ◽  
Cooling Rates ◽  
Torque Rheometry ◽  
The Matrix

ABSTRACT The melt crystallization characteristics of a compound of coconut lignocellulosic fibers dispersed in poly(butylene adipate terephthalate) (PBAT), a fully biodegradable copolyester matrix, was studied by differential scanning calorimetry (DSC). PBAT/coconut fiber compounds with 10% and 20% filler content were prepared in a laboratory internal mixer; torque rheometry showed negligible degradation during processing. Nonisothermal melt crystallization of the matrix was thoroughly studied by DSC in 10% compounds at cooling rates between 2 and 32°C/min, and quantitative information was provided on crystallization temperatures and rates, as well as the crystallinity developed, which turned out to be higher than expected at the high cooling rates. Crystallization kinetic results were correlated using classical macrokinetic Pseudo-Avrami, Ozawa, and Mo models, in order to obtain quantitative analytical expressions appropriate for processing applications. Pseudo-Avrami and Mo models were found to represent well the experimental data. A detailed analysis of the model fitting is presented, in order to assess the expected uncertainties. Despite its failings at the onset and end of the crystallization process, Mo model is recommended as best overall empirical correlation of the experimental data for the intended purpose.

scholarly journals Non-Isothermal Crystallization Kinetic of Polyethylene/Carbon Nanotubes Nanocomposites Using an Isoconversional Method

2019 ◽  
Vol 3 (1) ◽  
pp. 21 ◽  
Author(s):  
Beatriz Menezes ◽  
Tiago Campos ◽  
Thais Montanheiro ◽  
Renata Ribas ◽  
Luciana Cividanes ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Kinetic Parameters ◽  
Isothermal Crystallization ◽  
Crystallization Kinetic ◽  
Model Fitting ◽  
Kinetic Studies ◽  
Isoconversional Method ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Crystallite Sizes

Behavior studies of thermoplastic polymers during non-isothermal crystallization are extremely important since most of their properties are influenced by degree of crystallinity and the crystallization process. In general, an approach based on a model-fitting method is used to perform crystallization kinetic studies. Due to their inability to uniquely determine the reaction mode, many studies have used the isoconversional method, where it is not necessary to assume a crystallization model to obtain the kinetic parameters. Therefore, in this work, the influence of acid and octadecylamine functionalized carbon nanotubes (CNTs) in the crystallization kinetic of polyethylene (PE) was studied using an isoconversional method with differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The kinetic parameters and the crystallization model were determined. The incorporation of functionalized and non-functionalized CNTs into PE did not change the Johnson-Mehl-Avrami crystallization model. However, the CNTs increased the crystallization temperature and reduced the activation energy for crystallization. In addition, the Avrami coefficient values were lower for the nanocomposites when compared to pure PE. The incorporation of CNTs accelerated the crystallization of PE, reducing the crystallite sizes and modifying their morphology.

A Useful Curve Fitting Method for Concrete Uniaxial Compressive Experiment Data

2011 ◽  
Vol 291-294 ◽  
pp. 1015-1020 ◽  
Author(s):  
Chong Jin ◽  
Hong Wang ◽  
Xiao Zhou Xia
Keyword(s):  
Experimental Data ◽  
Orthogonal Polynomial ◽  
Least Square ◽  
Base Function ◽  
Concrete Material ◽  
Fitting Method ◽  
Orthogonal Base ◽  
The Matrix ◽  
Uniform Function ◽  
Curve Fitting Method

Based on the superiority avoiding the matrix equation to be morbid for those fitting functions constructed by orthogonal base, the Legendre orthogonal polynomial is adopted to fit the experimental data of concrete uniaxial compression stress-strain curves under the frame of least-square. With the help of FORTRAN programming, 3 series of experimental data is fitted. And the fitting effect is very satisfactory when the item number of orthogonal base is not less than 5. What’s more, compared with those piecewise fitting functions, the Legendre orthogonal polynomial fitting function obtained can be introduced into the nonlinear harden-soften character of concrete constitute law more convenient because of its uniform function form and continuous derived feature. And the fitting idea by orthogonal base function will provide a widely road for studying the constitute law of concrete material.

The effect of cooling rate on crystallization behavior and tensile properties of CF/PEEK composites

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Guangming Dai ◽  
Lihua Zhan ◽  
Chenglong Guan ◽  
Minghui Huang
Keyword(s):  
Cooling Rate ◽  
Crystallization Temperature ◽  
Crystallization Behavior ◽  
Crystalline Polymer ◽  
Scanning Calorimetry ◽  
Nonisothermal Crystallization ◽  
Cooling Rates ◽  
Control Range ◽  
Temperature Range ◽  
Transverse Tensile

Abstract In this study, the differential scanning calorimetry (DSC) tests were performed to measure the nonisothermal crystallization behavior of carbon fiber reinforced polyether ether ketone (CF/PEEK) composites under different cooling rates. The characteristic parameters of crystallization were obtained, and the nonisothermal crystallization model was established. The crystallization temperature range of the material at different cooling rates was predicted by the model. The unidirectional laminates were fabricated at different cooling rates in the crystallization temperature range. The results showed that the crystallization temperature range shifted to a lower temperature with the increase of cooling rate, the established nonisothermal crystallization model was consistent with the DSC test results. It is feasible to shorten the cooling control range from the whole process to the crystallization range. The crystallinity and transverse tensile strength declined significantly with the increase of the cooling rate in the crystallization temperature range. The research results provided theoretical support for the selection of cooling conditions and temperature control range, which could be applied to the thermoforming process of semi-crystalline polymer matrixed composites to improve the manufacturing efficiency.

scholarly journals Homogenisation Efficiency Assessed with Microstructure Analysis and Hardness Measurements in the EN AW 2011 Aluminium Alloy

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1211
Author(s):  
Maja Vončina ◽  
Aleš Nagode ◽  
Jožef Medved ◽  
Irena Paulin ◽  
Borut Žužek ◽  
...  
Keyword(s):  
Experimental Data ◽  
Image Analysis ◽  
Phase Equilibrium ◽  
Aluminium Alloy ◽  
Phase Formation ◽  
Aluminium Alloys ◽  
Eutectic Phase ◽  
The Matrix ◽  
Equilibrium Solidification ◽  
Homogenisation Process

When extruding the casted rods from EN AW 2011 aluminium alloys, not only their homogenized structure, but also their extrudable properties were significantly influenced by the hardness of the alloy. In this study, the object of investigations was the EN AW 2011 aluminium alloy, and the effect of homogenisation time on hardness was investigated. First, homogenisation was carried out at 520 °C for different times, imitating industrial conditions. After homogenisation, the samples were analysed by hardness measurements and further characterised by microscopy and image analysis to verify the influence of homogenisation on the resulting microstructural constituents. In addition, non-equilibrium solidification was simulated using the program Thermo-Calc and phase formation during solidification was investigated. The homogenisation process enabled more rounded shape of the Al2Cu eutectic phase, equilibrium formation of the phases, and the precipitation in the matrix, leading to a significant increase in the hardness of the EN AW 2011 aluminium alloy. The experimental data revealed a suitable homogenisation time of 4–6 h at a temperature of 520 °C, enabling optimal extrusion properties.

MICROSTRUCTURAL EVOLUTION OF Al-Cu-Mg-Ag ALLOY WITH TRACE Zr ADDITION DURING TWO-STEP HOMOGENIZATION

2009 ◽  
Vol 23 (06n07) ◽  
pp. 855-862 ◽  
Author(s):  
FEIYUE MA ◽  
ZHIYI LIU
Keyword(s):  
Melting Point ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Cast Alloy ◽  
Scanning Calorimetry ◽  
Zr Addition ◽  
Homogenization Time ◽  
The Matrix ◽  
Higher Temperature ◽  
Lower Temperature

The microstructural evolution in an Al - Cu - Mg - Ag alloy with trace Zr addition during homogenization treatment was characterized by Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray Spectroscopy (EDS). It was shown that the low-melting-point phase segregating toward grain boundaries is Al 2 Cu , with a melting point of 523.52°C. A two-step homogenization process was employed to optimize the microstructure of the as-cast alloy, during which the alloy was first homogenized at a lower temperature, then at a higher temperature. After homogenized at 420°C for 6 h, Al 3 Zr particles were finely formed in the matrix. After that, when the alloy was homogenized at an elevated temperature for a longer time, i.e., 515°C for 24 h, most of the precipates at the grain boundaries were removed. Furthermore, the dispersive Al 3 Zr precipitates were retained, without coarsening greatly in the final homogenization step. A kinetics model is employed to predict the optimal homogenization time at a given temperature theoretically, and it confirms the result in present study, which is 420°C/6h+515°C/24h.

Crystallization kinetics mechanism investigation of sol–gel-derived NaYF4:(Yb,Er) up-converting phosphors

CrystEngComm ◽  
2017 ◽  
Vol 19 (34) ◽  
pp. 4992-5000 ◽  
Author(s):  
C. Bartha ◽  
C. E. Secu ◽  
E. Matei ◽  
M. Secu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Crystallization Kinetics ◽  
Sol Gel ◽  
Model Fitting ◽  
Crystallization Mechanism ◽  
Differential Scanning Calorimetry Analysis ◽  
Scanning Calorimetry ◽  
Model Free

The crystallization mechanism of sol–gel-derived NaYF4:(Yb,Er) up-converting phosphors has been studied by differential scanning calorimetry analysis using both model-free and model fitting approaches.

Properties of aluminum metal matrix composites manufactured by selective laser melting

2021 ◽  
Vol 112 (7) ◽  
pp. 552-564
Author(s):  
Christian Felber ◽  
Florian Rödl ◽  
Ferdinand Haider
Keyword(s):  
Additive Manufacturing ◽  
Aluminum Alloys ◽  
Selective Laser Melting ◽  
Metal Matrix ◽  
High Hardness ◽  
High Strength ◽  
Laser Melting ◽  
Scanning Calorimetry ◽  
Particle Reinforcement ◽  
The Matrix

Abstract The most promising metal processing additive manufacturing technique in industry is selective laser melting, but only a few alloys are commercially available, limiting the potential of this technique. In particular high strength aluminum alloys, which are of great importance in the automotive industry, are missing. An aluminum 2024 alloy, reinforced by Ti-6Al-4V and B4C particles, could be used as a high strength alternative for aluminum alloys. Heat treating can be used to improve the mechanical properties of the metal matrix composite. Dynamic scanning calorimetry shows the formation of Al2Cu precipitates in the matrix instead of the expected Al2CuMg phases due to the loss of magnesium during printing, and precipitation processes are accelerated due to particle reinforcement and additive manufacturing. Strong reactions between aluminum and Ti-6Al-4V are observed in the microstructure, while B4C shows no reaction with the matrix or the titanium. The material shows high hardness, high stiffness, and low ductility through precipitation and particle reinforcement.

The thermodynamic properties of mixed phospholipid bilayers: a theoretical analysis

1984 ◽  
Vol 62 (8) ◽  
pp. 796-802 ◽  
Author(s):  
Maryse Mondat ◽  
A. Georgallas ◽  
D. A. Pink ◽  
M. J. Zuckermann
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
Reasonable Agreement ◽  
Phospholipid Bilayers ◽  
Scanning Calorimetry ◽  
Phase Separations ◽  
Lipid Mixtures ◽  
Wide Range ◽  
Acyl Chains ◽  
Gel Phase

A theoretical model is presented with the intention of describing lateral phase separations in binary lipid mixtures in which the acyl chains of the components differ in their length. The model includes explicitly interactions between the acyl chains and between polar heads of the lipid molecules. Phase diagrams and thermodynamic properties of binary lipid mixtures were calculated using a wide range of interaction parameters. It is shown that the occurrence of immiscibility in the gel phase is related to the interactions between the polar heads of the lipid molecules. The calculated results for binary lipid mixtures are compared with the available experimental data. In particular, the calculated specific heat for dilauroyl phosphatidylcholine – distearoyl phosphatidylcholine is in reasonable agreement with experimental results obtained from differential scanning calorimetry measurements.

scholarly journals Thermal Kinetics of SiCp Reinforced Al-Zn-Mg-Cu Alloy Composite

2021 ◽  
Author(s):  
Saikat Das ◽  
R. Govinda Rao ◽  
Prasanta Kumar Rout
Keyword(s):  
Base Alloy ◽  
Accelerated Aging ◽  
Stir Casting ◽  
Hardness Profile ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
The Matrix ◽  
Aging Kinetics ◽  
Aging Phenomena ◽  
Kinetics Of

Abstract In the present work, the artificial aging kinetics of SiCp particles reinforced AA7075-SiCp composite fabricated by stir casting method was investigated. The aging behavior of AA7075-SiCp composite was investigated by Rockwell hardness tests and differential scanning calorimetry (DSC). Results show there are no changes in the sequences of formation and dissolution of precipitate. Reinforced particles are uniformly distributed throughout the matrix. The hardness profile shows increase in hardness with the comparison of AA7075 base alloy. In addition to SiCp in the matrix, precipitation kinetics has changed compared with base alloy since higher dislocations present in composite, hence requires lower activation energy to form ή precipitate and takes less time to reach the maximum hardness. In contrast, the addition of SiCp at low volume percent also showing accelerated aging phenomena in the composite during the aging process. High-resolution transmission electron microscope (HRTEM) micrograph of peak age (T6) condition divulges that enormous fine and plate-like ή (MgZn2) precipitates are uniformly distributed in the composite.

scholarly journals Quantification of multiple simultaneously occurring nitrogen flows in the euphotic ocean

2016 ◽  
Author(s):  
Min Nina Xu ◽  
Yanhua Wu ◽  
Li Wei Zheng ◽  
Zhenzhen Zheng ◽  
Huade Zhao ◽  
...  
Keyword(s):  
Matrix Equation ◽  
Ammonia Oxidation ◽  
Mass Conservation ◽  
Quantitative Information ◽  
Nitrite Oxidation ◽  
Dissolved Nitrogen ◽  
Total Dissolved Nitrogen ◽  
Transformation Rates ◽  
The Matrix ◽  
Multiple Transformation

Abstract. The general features of the N cycle in the sunlit ocean are known, but quantitative information about multiple transformation rates among nitrogen pools, i.e., ammonium (NH4+), nitrite (NO2−), nitrate (NO3−) and particulate/dissolved organic nitrogen (PN/DON), are limited due to methodological difficulties. By adding a single 15N-labelled NH4+ tracer into incubators, we monitor ed the changes in concentration and isotopic composition of the total dissolved nitrogen (TDN), PN, NH4+, NO2−, and NO3− pools to trace the 15N and 14N flows. Based on mass conservation and isotope mass balance, we formulate d a matrix equation that allow edus to simultaneously derive the rates of multiple transformation processes in the nitrogen reaction web . We abandoned inhibitors and minimized the alteration of the system by adding a limited amount of tracer. In one single incubation, solution of the matrix equation provided the rates of NH4+, NO2−, and NO3− uptake; ammonia oxidation; nitrite oxidation; nitrite excretion; DON release; and potentially, the remineralization rate. To our knowledge, this is the first and most convenient method designed to quantitatively and simultaneously resolve complicated nitrogen transformation rates, albeit with some uncertainties. Field examples are given, and c omparisons with conventional labeling methods are discussed.

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