Showing papers on "Differential scanning calorimetry published in 2020"

Green synthesis and characterization of zinc oxide nanoparticles using Eucalyptus globulus Labill. leaf extract and zinc nitrate hexahydrate salt

Abstract: This study consists of a reliable process for synthesizing ZnO NPs by green method. Here, Eucalyptus globulus Labill. leaf extract is utilized as an efficient chelating and capping agent for synthesizing ZnO NPs from zinc nitrate hexahydrate salt. The plant ingredients, structure, morphology, thermal behavior, chemical composition and optical properties of ZnO nanoparticles were investigated using several characterization techniques, namely XRD, FE-SEM, EDX, BET, Zeta potential, DLS, differential scanning calorimetry (DSC) analysis, FT-IR analysis and UV–Vis spectroscopy. The UV–Vis and FTIR analysis of Eucalyptus globulus leaf extract verified that this extract is a promising candidate for biosynthesizing ZnO NPs. The XRD spectrum, DLS and the SEM images confirmed the crystallinity and the spherical-shape of the ZnO NPs with an average size between 27 and 35 nm. The band-gap of the ZnO were measured to be around 2.67 eV. Zeta potential and BET analysis showed that, the biosynthesized ZnO NPs possess good stability and the their specific surface area is 23.481 m2/g. DSC analysis exhibits two endothermic peaks related to the water evaporation absorbed by the NPs and modification of zinc complex to zinc hydroxide, with a single exothermic peak related to the crystallization of ZnO NPs and degradation of organic materials.

Fully Biobased Superpolymers of 2,5-Furandicarboxylic Acid with Different Functional Properties: From Rigid to Flexible, High Performant Packaging Materials

Abstract: In the present paper, four fully biobased homopolyesters of 2,5-furandicarboxylic acid (2,5-FDCA) with a high molecular weight have been successfully synthesized by two-stage melt polycondensation, starting from the dimethyl ester of 2,5-FDCA and glycols of different lengths (the number of methylene groups ranged from 3 to 6). The synthesized polyesters have been first subjected to an accurate molecular characterization by NMR and gel-permeation chromatography. Afterward, the samples have been successfully processed into free-standing thin films (thickness comprised between 150 to 180 μm) by compression molding. Such films have been characterized from the structural (by wide-angle X-ray scattering and small-angle X-ray scattering), thermal (by differential scanning calorimetry and thermogravimetric analysis), mechanical (by tensile test), and gas barrier (by permeability measurements) point of view. The glycol subunit length was revealed to be the key parameter in determining the kind and fraction of ordered phases developed by the sample during compression molding and subsequent cooling. After storage at room temperature for one month, only the homopolymers containing the glycol subunit with an even number of −CH2– groups (poly­(butylene 2,5-furanoate) (PBF) and poly­(hexamethylene 2,5-furanoate) (PHF)) were able to develop a three-dimensional ordered crystalline phase in addition to the amorphous one, the other two appearing completely amorphous (poly­(propylene 2,5-furanoate (PPF) and poly­(pentamethylene 2,5-furanoate) (PPeF)). From X-ray scattering experiments using synchrotron radiation, it was possible to evidence a third phase characterized by a lower degree of order (one- or two-dimensional), called a mesophase, in all the samples under study, its fraction being strictly related to the glycol subunit length: PPeF was found to be the sample with the highest fraction of mesophase followed by PHF. Such a mesophase, together with the amorphous and the eventually present crystalline phase, significantly impacted the mechanical and barrier properties, these last being particularly outstanding for PPeF, the polyester with the highest fraction of mesophase among those synthesized in the present work.

A novel form stable PCM based bio composite material for solar thermal energy storage applications

Abstract: Phase change materials found to be a promising solution in the field of thermal energy storage. However, the low thermal conductivity and form stability over cycles of charging and discharging of PCM are challenges to address. In the proposed study, a novel and low cost biochar-PCM hybrid latent heat energy storage material have been developed and tested. The biochar is prepared from aquatic invasive weed plants by using a batch type pyrolyser. The characteristics and properties of the novel energy storage material have been evaluated using various experimental and analytical methods. The methods include Brunauer, Emmett and Teller (BET), Scanning electron microscope (SEM), X-ray powder diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT–IR) and thermal conductivity tester. The study also put forward the optimized proportion of biochar and PCM in hybrid thermal energy storage material. The new material shows superior thermal conductivity over pure PCM as well as better stability due to the high carbon content and porosity of the developed biochar. Simple Impregnation method has been used to prepare form stable composite material which has good thermal and structural stability. The best mixing ratio (PCM: biochar) is found to be 6:4 (wt/wt%) with minimum leakage of PCM from the composite. The sample prepared through this method yield all the desirable properties as compared to other developed samples. The chemical properties of the composite remain the same as the pure PCM, which confirms no chemical interaction between the PCM and biochar. The heat of fusion is calculated to be 179.4 J/g. The thermal conductivity of the PCM is enhanced up to 13.82 times with the addition of water hyacinth biochar as a supporting matrix. The addition of aluminum metal powder further increases the thermal conductivity by 17.27 times higher than that of PCM alone.

Mechanical, Thermal and Antimicrobial Properties of Chitosan-Based-Nanocomposite with Potential Applications for Food Packaging

Abstract: Sodium montmorillonite organically modified by octadecylammonium (Np-Clay) and zinc oxide nanoparticles (Np-ZnO) were incorporated into chitosan (C) matrix in different proportions to evaluate its mechanical properties and antimicrobial activities. The composites were obtained by polymer intercalation method in solution using acetic acid (1% v/v) as solvent. The functional groups, thermic behavior and surface morphology of the chitosan film and of the composites prepared with different percentages of Np-Clay and Np-ZnO were characterized through Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results showed that a combined effect of clay and zinc oxide increases significantly the mechanical properties of pure chitosan. FTIR results confirmed good compatibility among functional groups of chitosan, montmorillonite/metallic oxides. The Np-ZnO distribution became more uniform in chitosan films when the Np-clay was incorporated, thus, the Np-Clay compatibilizes the Np-ZnO with the chitosan and the mechanical properties improved and without affecting the antimicrobial activity of the films. The thermal degradation temperature of the chitosan did not change significantly with the addition of Np-Clay, but changes significantly with Np-ZnO addition. In antimicrobial test was found that the chitosan and Np-ZnO showed a synergistic effect against to Escherichia coli and Staphylococcus aureus. The addition of Np-ZnO and C-Clay in chitosan resulted in enhancement of mechanical and antimicrobial properties, turning this material prospective for food packaging applications.

Synthesis and thermal properties of nanoencapsulation of paraffin as phase change material for latent heat thermal energy storage

Abstract: In this work, a series of nanoencapsulated phase change materials (NanoPCMs) with paraffin wax (PW) as core and melamine-formaldehyde (MF) as shell were synthesized by the in-situ polymerization method. The morphology, chemical structure and thermal properties of prepared NanoPCMs were characterized by scanning electron microscope, Fourier transform infrared, differential scanning calorimetry and thermogravimertic analyzer. The results show that the PW is successfully encapsulated in the MF without chemical interaction, and the NanoPCMs present regular spherical shape with the average diameter of 260–450 nm. The encapsulation efficiency of the NanoPCMs increases with the augment of the supplied amount of core material. The maximum encapsulation efficiency of the NanoPCMs can reach up to approximately 75%. The NanoPCMs can maintain excellent thermal reliability and stability after 2000 thermal cycling. The prepared NanoPCMs can be well applied in the latent heat thermal energy storage and thermal management systems due to their remarkable encapsulation efficiency and thermal properties enable them to.

Poly(lactic Acid)-Biochar Biocomposites: Effect of Processing and Filler Content on Rheological, Thermal, and Mechanical Properties.

Abstract: Biocomposites based on poly(lactic acid) (PLA) and biochar (BC) particles derived from spent ground coffee were prepared using two different processing routes, namely melt mixing and solvent casting. The formulated biocomposites were characterized through rheological, thermal, and mechanical analyses, aiming at evaluating the effects of the filler content and of the processing method on their final properties. The rheological characterization demonstrated the effectiveness of both exploited strategies in achieving a good level of filler dispersion within the matrix, notwithstanding the occurrence of a remarkable decrease of the PLA molar mass during the processing at high temperature. Nevertheless, significant alterations of the PLA rheological behavior were observed in the composites obtained by melt mixing. Differential scanning calorimetry (DSC) measurements indicated a remarkable influence of the processing method on the thermal behavior of biocomposites. More specifically, melt mixing caused the appearance of two melting peaks, though the structure of the materials remained almost amorphous; conversely, a significant increase of the crystalline phase content was observed for solvent cast biocomposites containing low amounts of filler that acted as nucleating agents. Finally, thermogravimetric analyses suggested a catalytic effect of BC particles on the degradation of PLA; its biocomposites showed decreased thermal stability as compared with the neat PLA matrix.

The Role of Demixing and Crystallization Kinetics on the Stability of Non‐Fullerene Organic Solar Cells

Abstract: With power conversion efficiency now over 17%, a long operational lifetime is essential for the successful application of organic solar cells. However, most non-fullerene acceptors can crystallize and destroy devices, yet the fundamental underlying thermodynamic and kinetic aspects of acceptor crystallization have received limited attention. Here, room-temperature (RT) diffusion coefficients of 3.4 × 10-23 and 2.0 × 10-22 are measured for ITIC-2Cl and ITIC-2F, two state-of-the-art non-fullerene acceptors. The low coefficients are enough to provide for kinetic stabilization of the morphology against demixing at RT. Additionally profound differences in crystallization characteristics are discovered between ITIC-2F and ITIC-2Cl. The differences as observed by secondary-ion mass spectrometry, differential scanning calorimetry (DSC), grazing-incidence wide-angle X-ray scattering, and microscopy can be related directly to device degradation and are attributed to the significantly different nucleation and growth rates, with a difference in the growth rate of a factor of 12 at RT. ITIC-4F and ITIC-4Cl exhibit similar characteristics. The results reveal the importance of diffusion coefficients and melting enthalpies in controlling the growth rates, and that differences in halogenation can drastically change crystallization kinetics and device stability. It is furthermore delineated how low nucleation density and large growth rates can be inferred from DSC and microscopy experiments which could be used to guide molecular design for stability.

Amino-Functionalized β-Cyclodextrin to Construct Green Metal-Organic Framework Materials for CO2 Capture.

Abstract: The adsorption of CO2 by conventional liquid alkanolamine adsorbents does not meet the requirements for green-friendly development in industrial applications. In this work, we constructed NH2-β-CD-MOF for the first time through the amino-functionalization of the lowest-priced, readily available, and biocompatible β-CD. Subsequently, the samples were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, elemental analysis, and N2 adsorption/desorption. The CO2 adsorption capacity of NH2-β-CD-MOF was found to be 12.3 cm3/g, which is 10 times that of β-CD-MOF. In addition, NH2-β-CD-MOF has outstanding selective adsorption of CO2/N2 (947.52) compared with the reported materials. The adsorption mechanism of CO2 was analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Furthermore, we have found that NH2-β-CD-MOF has better water stability relative to β-CD-MOF a...

Peculiarities of the Crystal Structure Evolution of BiFeO3-BaTiO3 Ceramics across Structural Phase Transitions.

Abstract: Evolution of the crystal structure of ceramics BiFeO3-BaTiO3 across the morphotropic phase boundary was analyzed using the results of macroscopic measuring techniques such as X-ray diffraction, differential scanning calorimetry, and differential thermal analysis, as well as the data obtained by local scale methods of scanning probe microscopy. The obtained results allowed to specify the concentration and temperature regions of the single phase and phase coexistent regions as well as to clarify a modification of the structural parameters across the rhombohedral-cubic phase boundary. The structural data show unexpected strengthening of structural distortion specific for the rhombohedral phase, which occurs upon dopant concentration and temperature-driven phase transitions to the cubic phase. The obtained results point to the non-monotonous character of the phase evolution, which is specific for metastable phases. The compounds with metastable structural state are characterized by enhanced sensitivity to external stimuli, which significantly expands the perspectives of their particular use.

Concentration dependence of the elastic moduli, thermal properties, and non-isothermal kinetic parameters of Yb3+ doped multicomponent tellurite glass system

Abstract: The thermal properties and the kinetic parameters of TeO2–Li2O–ZnO–Nb2O5–Yb2O3 glass series have been evaluated as a function of increasing Yb2O3 content. The theoretical elastic properties and the quantitative analysis (the link between the elastic features and the changed chemical composition of the glass) have been determined by the use of bond compression and Makishima–Mackenzie models. The thermal analysis Differential Scanning Calorimetry (DSC) test was used for estimating the glass characteristics temperatures, thermal stability, and non-isothermal kinetic parameters at the heating rates (β) 10, 15, 20 and 25 K/min. The activation energies of the glass transition 〈 Eg 〉 and crystallization 〈 Ec 〉 , as well as the order of the crystallization reaction (n), have been computed by different models with clear consistency and harmony between them. It was found that the characteristics temperatures of transition (Tg), softening (Ts), the onset of the crystallization (Tx) and the crystallization (Tc) increased with increasing the heating rate. Also, the results showed the higher thermal stability values (>100 K) for the understudied glass which is confirmed by KSP and ((Tc–Tg)/Tg) parameters values. Calculating of (n) showed that the crystallization started with surface nucleation and finished with bulk volume nucleation with rising Yb2O3 (mol %). The computed elastic moduli were linked with the interpretation of the thermal parameters to give a comprehensive image of the studied glass system.

Thermal behavior of graphene oxide-coated piassava fiber and their epoxy composites

Abstract: Natural lignocellulosic fibers have been studied as cost-effective reinforcements in composites for engineering applications that, in some cases, may require exposure to temperatures above ambient. In the present work a promising fiber extracted from a Brazilian palm tree, the piassava fiber both neat as well as graphene oxide (GO) functionalized, had their thermal behavior analyzed jointly with corresponding epoxy composites. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were for the first time employed to assess the thermal properties of the GO-coated piassava fiber. Dynamic mechanical analysis (DMA) investigated innovative epoxy matrix composites reinforced up to 30 vol% of both neat and GO-coated piassava fiber. TGA/DTG results indicate a limit of thermal stability of about 200 °C for the neat piassava fiber. On the other hand, the hemicellulose and lignin maximum degradation rates occurred at relatively higher temperatures for the GO-coated piassava fibers. The DSC analysis revealed an endothermic peak at about 125 °C for the neat piassava fiber associated with the breakage of molecular bond, which was not found for the GO-coated fibers within the maximum interval of temperature analyzed. The DMA parameters revealed notable changes attributed to the effect of GO coating on the piassava fibers regarding the viscous stiffness and damping capacity of the epoxy composite.

Bisbenzylidene cyclopentanone and cyclohexanone-functionalized polybenzoxazine nanocomposites: Synthesis, characterization, and use for corrosion protection on mild steel

Abstract: In this study, we synthesized and investigated bisbenzylidene cyclopentanone and cyclohexanone-functionalized polybenzoxazine nanocomposites as anti-corrosion coatings. The chemical structures of CP-BZ and CH-BZ were confirmed using Fourier transform infrared (FTIR) spectroscopy and 1H and 13C nuclear magnetic resonance spectroscopy. Differential scanning calorimetry (DSC) revealed that the thermal polymerization temperature of the uncured CH-BZ (198 °C) was significantly lower than that of the monomer 3-phenyl-3,4-dihydro-2H-benzoxazine (263 °C). We used DSC and FTIR spectroscopy to study the curing behavior of these monomers. The degradation temperature of poly(CH-BZ) (326 °C) was higher than that poly(CP-BZ) (249 °C), based on thermogravimetric analysis. We used solution dispersion and thermal ring-opening polymerization to prepare a new class of bisbenzylidene-based polybenzoxazine (PBZ; CP-BZ or CH-BZ) composites with epoxidized soybean oil (E-SBO; 10 or 20 wt%) and E-SBO/bentonite (nanoclay; 3 or 5 wt%) for use as corrosion-protection coatings for mild steel (MS). We employed salt-spray and electrochemical measurements to investigate the influence of the epoxy and nanoclay contents, respectively, on the corrosion-resistance of these coatings. A 20 wt% epoxy content in the PBZ/E-SBO coatings provided corrosion-resistance superior to those of pure PBZs. Furthermore, the addition of 20 wt% E-SBO and 3 wt% of nanoclay decreased the corrosion rate by one order of magnitude (2.653 × 10−3 mm year–1) when compared with that of pure poly(CH-BZ) (1.292 × 10-2 mm year–1) and two orders of magnitude when compared with blank(MS) (1.094 × 10-1 mm year–1) with protection efficiency (98.16 %), revealing markedly increased barrier properties of the composite coatings towards corrosive species. Thus, these materials function as excellent corrosion-resistance coatings for MS.