Thermal Gravimetric Analysis Curves Research Articles

Investigation of molecular polarity and thermal stability of monoethanolamine based deep eutectic solvents

In this work, sigma profile and sigma potential were generated using COSMOtherm software to examine the molecular polarity of choline chloride with monoethanolamine based deep eutectic solvents at various mole ratios (i.e., 1:2, 1:3, 1:4, 1:5, 1:6 and 1:7). It is used to analyses the interaction between the molecules during extraction process. The result revealed that the selected DES are feasible for use as extracting solvents for polyphenol extraction process. Also, it shows that the prepared DES was hydrophilic in nature and it denotes ability of the amine to act as a base. Then, using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), the similar molar ratio of amine-based DES was synthesized and their thermal stability was described in terms of decomposition temperatures, mass loss and melting temperature. When heating rate increased, the TGA curves of 1:6 and 1:7 DES, temperature shifted to higher direction when compared to other mole ratios of DES. When HBD is increases thermal stability also increases in this case. HBD plays an important role in thermal stability of DES which mainly depends on intermolecular interactions. Similarly, in DSC 1:6 and 1:7 high melting temperature and high enthalpy was observed when compare to other mole ratios. It denotes by increasing the HBD ratio melting temperature also increased due to stronger intermolecular force and stronger interaction between HBA and HBD. In end the synthesized DES was suggested to be used as intermediate for the extraction of polyphenols from agricultural wastes.

Synthesis, Structure, Spectral-Luminescent Properties, and Biological Activity of Chlorine-Substituted N-[2-(Phenyliminomethyl)phenyl]-4-methylbenzenesulfamide and Their Zinc(II) Complexes

New azomethine compounds of 2-(N-tosylamino)benzaldehyde or 5-chloro-2-(N-tosylamino)benzaldehyde and the corresponding chlorine-substituted anilines, zinc(II) complexes based on them have been synthesized. The structures of azomethines and their complexes were determined by elemental analysis, IR, 1H NMR, X-ray spectroscopy, and X-ray diffraction. It is found that all ZnL2 complexes have a tetrahedral structure according to XAFS and X-ray diffraction data. The photoluminescent properties of azomethines and zinc complexes in methylene chloride solution and in solid form have been studied. It is shown that the photoluminescence quantum yields of solid samples of the complexes are an order of magnitude higher compared to the solutions and range from 11.34% to 48.3%. The thermal properties of Zn(II) complexes were determined by thermal gravimetric analysis (TGA) and differential scanning calorimetry. The TGA curves of all the compounds suggest their high thermal stability up to temperatures higher than 290 °C. The electrochemical properties of all complexes were investigated by the cyclic voltammetry method. The multilayered devices ITO/PEDOT:PSS/NPD/Zn complex/ TPBI/LiF/Al with wide electroluminescence (EL) color range spanning the range from bluish-green (494 nm) to green (533 nm) and the high values of brightness, current and power efficiency were fabricated. The biological activity of azomethines and zinc complexes has been studied. In the case of complexes, the protistocidal activity of the zinc complex with azomethine of 5-chloro-2-(N-tosylamino)benzaldehyde with 4-chloroaniline was two times higher than the activity of the reference drug toltrazuril.

A Study on the Effects of Potassium Permanganate on the Functionalization of Multi-Walled Carbon Nanotubes

In this work, multi-walled carbon nanotubes (MWCNTs) are functionalized by a wet chemical oxidation method using a mixture of potassium permanganate (KMnO4) and sulfuric acid (H2SO4) at 70 °C, for 12 h. The effects of various KMnO4 amounts on the functionalization of MWCNTs are studied and reported. The surface morphologies, structural properties, dispersion and thermal stability of the MWCNTs are characterized using a field emission scanning electron microscope (FE-SEM), Raman spectroscopy, UV-visible spectroscopy (UV–vis), thermal gravimetric analysis (TGA). The FE-SEM images display some surface roughness, cutting and open ends of functionalized MWCNTs (f-MWCNTs). The TGA curves of f-MWCNTs indicate a weight loss between 150 °C and 350 °C, which is attributed to the loss of carboxyl groups on the MWCNTs surface and the weight loss is increased when KMnO4 mass is increased. The highest weight loss value of 22.23% is recorded for the oxidation treatment with a mixture of 5 M H2SO4 and 200 mg KMnO4. UV–vis measurements indicate that the f-MWCNTs are highly dispersed in the aquoues solution in comparision to the pristine MWCNTs (p-MWCNTs). And f-MWCNTs with higher functionalization degree show better dispersibility. This study provides a great prospect of effective method to cut, end-open, functionalize and disperse MWCNTs.

Application of L-citrulline loaded beta-cyclodextrin nano-carrier for fabrication of a corrosion protective silane film on mild-steel

In the present work, a beta-cyclodextrin (β-CD) container was utilized for encapsulating the L-citrulline (L-Cit) molecules to achieve promising active and/or passive protection properties in a silane coating. The inclusion complexes (β-CD-L-Cit) were characterized by Fourier-transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), Raman, and Ultraviolet-visible spectroscopy (UV–Vis) techniques. The morphologies of the particles were visualized by field-emission scanning electron microscopy (FE-SEM). The TGA curves displayed about 6% L-Cit molecules encapsulation via β-CDs. The results obtained from the polarization and electrochemical impedance spectroscopy (EIS) tests results evidenced a mixed inhibition mechanism of the encapsulated inhibitor with an inhibition efficiency of 87% for the β-CD-L-Cit sample.The active protection ability of the silane coating (SiC) was evidenced by the EIS results of the scratched coatings. The total resistance of the β-CD-L-Cit/SiC scratched composite was improved from 5540 Ω.cm2 (neat scratched SiC) to 33,128 Ω.cm2 (scratched SiC + 1 wt% inclusion complexes) corresponding to the coverage of the scratched parts via a barrier film. The FE-SEM micrographs demonstrated the development of a smooth and compact inhibitive layer on the scratched region. Additionally, the conducted EIS test over the intact sample illustrated that the highest anti-corrosion property belonged to the β-CD-L-Cit/SiC sample (88,774 Ω.cm2). The improvements are attributed to the SiC matrix pathways blockage by the β-CD-L-Cit inclusion complexes. Besides the experiments, various modeling and simulation explorations were conducted employing Density Functional Theory (DFT-D), Molecular Dynamics (MD), and Monte Carlo (MC)-based tools for elucidating fundamental understandings about L-Cit and β-CD-L-Cit interactions/adsorption at their interface with metallic adsorbent. These theoretical evaluations strongly reflected the affinity of pure and β-CD complexes of L-Cit onto the adsorbent.

Can nano PZT-OPC composites be used as a smart γ-ray attenuator?

Nano PbZr0.52Ti0.48O3-ordinary Portland cement (PZT-OPC) composites were fabricated by a ball milling technique with different PZT content (30, 50, 70, and 90% by weight). The prepared samples were annealed at 600 °C. The structure, morphology, thermal and electrical properties of these annealed samples were investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA). The effects of PZT on dielectric and piezoelectric properties of the composites were investigated. γ-ray spectroscopy was used to measure the γ-ray attenuation coefficients of the annealed nanocomposite samples using the 661.7 keV γ-ray of 137Cs source. The microstructure changes of the prepared composite samples were investigated using the positron annihilation lifetime (PAL) and Doppler broadening (DB) techniques. The XRD patterns show both PZT and cement peaks. Also, these patterns indicate the presence of PZT retards the hydration process of the Portland cement. The FTIR spectra show the major absorption bands for both PZT and cement. SEM images show the binding between calcium silicate hydrate and PZT which may be a better factor for improving the mechanical properties of the cement. TGA curves show a higher thermal weight loss for 50% PZT-OPC composite sample. The PZT-OPC composite sample with 50% PZT content shows the highest γ-ray mass attenuation coefficient compared with the other composite samples. The positron annihilation spectroscopy (PAS) results show that the size of large voids and the concentration of small defects increase by increasing PZT content. Also, these results reveal that the core electrons slightly reduced by increasing PZT content. The results indicate that the dielectric constant and piezoelectric coefficient values slightly and rapidly increase for composite samples with PZT content <50% and >50%, respectively. Finally, the 50% PZT-OPC composite sample showed novel shielding and acceptable piezoelectric properties to be used as a smart shield.

Surface functionalisation of multi-walled carbon nanotubes with tris(2-aminoethyl)amine and their characterisation

Carbon nanotubes are widely employed in various applications because of its excellent properties. However, they generally suffer from the low dispersion into aqueous solutions. Many applications of carbon nanotubes require previous surface functionalisation. In present study, we report the surface functionalisation of multi-walled carbon nanotubes (MWCNTs) by grafting a tris(2-aminoethyl)amine (TAA) via a facile method. The pristine MWCNTs and TAA-functionalised MWCNTs (MWCNTs-TAA) are characterised by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and Raman spectroscopy, thermal gravimetric analysis (TGA). The TEM image of MWCNTs-TAA exhibits significantly improved dispersion of the MWCNTs. The high-resolution FE-SEM images clearly show the opening ends of nanotubes after TAA functionalisation. The increase in nanotube diameters of MWCNTs-TAA is observed compared to the pristine MWCNTs. The strong absorption peak at 1530 cm−1 from FTIR spectra for MWCNTs-TAA indicates that the amine groups are successfully grafted onto the surface of MWCNTs. The TGA curves of MWCNTs-TAA reveal a weight loss in the temperature range of 200 to 450 °C attributed to the decomposition of the amine groups, and the highest weight loss is obtained to be 22.14 wt% after 12 h reaction time. This work demonstrates the facile and efficient method to functionalise MWCNTs with TAA.

Influence of the Expandable Graphite on the Thermal properties of a Rigid Polyurethane Foam for construction

In this paper, low-combustible composites were made by adding 0.8-25 wt% of expandable graphite to rigid polyurethane foams (PUF) to ensure effective and safe usage of building materials made of PUFs. Thermal gravimetric analysis (TGA) was used to study thermal properties and effectiveness of the resulting low-combustible composites in construction. The analysis of TGA curves of the studied composites can be interpreted as a two-stage process: acid-catalyzed degradation of PUF and formation of an intumescent char layer. A dense intumescent layer can provide an effective prevention of heat transfer. The paper showed that the addition of 25 wt% of expandable graphite to PUF composite improved the thermal stability by 8 °С, as compared to starting PUF, while the residue was 36.2 wt% at 600°С, which was higher by approximately 16 wt% than the residue of starting PUF. So, the sample with 25 % loading of expandable graphite in rigid PUF composite showed the best thermal characteristics.

Pure-Blue Fluorescence Molecule for Nondoped Electroluminescence with External Quantum Efficiency Approaching 13%

A pure-blue light-emitting material is one of the key components in the preparation of organic light-emitting diode (OLED) displays. Although high-efficiency blue OLEDs have been realized in therma...

The Role of Sodium Lauryl Sulfate on the Film Properties of Styrene-Butyl Acrylate-Acrylic Acid Copolymer Latex

In this study, the concentration effect of sodium lauryl sulfate (SLS) as a surfactant in the synthesis of styrene/acrylic acid/butyl acrylate copolymer (SAC) latex particles via seeded emulsion polymerization technique was investigated. Scanning electron microscopy (SEM), minimum film-forming temperature (MFFT), differential scanning calorimetry (DSC), dynamic light scattering (DLS), and thermal gravimetric analysis (TGA) techniques were used to explain the change on physicochemical properties and morphology. The main goal is to determine an optimal surfactant concentration to obtain latexes with low MFFT. DLS studies showed that the particle size decreases 118.30 to 75.18 nm with the increase of SLS concentration. MFFT of latexes decreased with increasing SLS concentration. From the TGA curves, it was found that all the SAC latex particles exhibit a three-step decomposition process. The observed single Tg values for SAC particles showed that the latexes were prepared successfully.

A cycling study for reliability, chemical stability and thermal durability of polyethylene glycols of molecular weight 2000 and 10000 as organic latent heat thermal energy storage materials

In this experimental study, thermal aging test for investigating the variations in thermal and chemical properties of two selected organic phase change materials (PCMs) has been carried out. Polyethylene glycols (PEGs) of molecular weight of 2000 and 10 000 have been considered as potential latent heat thermal energy storage (LHTES) materials for investigation. The aim of this study is to identify the probable variations in thermal properties and chemical structures of PEGs after melting/freezing cycles repeated for 1500 times. The differential scanning calorimetry (DSC) technique was adopted for measuring the thermal properties such as melting point and latent heat of PCMs. In order to study the variations in PCM's chemical functional groups, Fourier transform infrared (FT-IR) spectroscopy was used. Thermal durability property after the cycling test was investigated using thermogravimetric analysis. The DSC measurements indicated that PEG2000 experienced a maximum variation of about 4°C in melting point while the latent heat of fusion reduces by 16% after the cycle test. PEG10000 shows a variation of about 0.3°C in melting point and 15% of the latent heat of melting after the entire cycle test. The spectral investigation confirms that there are no variations in the functional groups of selected materials after cycle test, which can be inferred as chemical stability of them. The thermal gravimetric analysis curves show that both PEGs are thermally quite durable as well after such large number of melt/freeze cycles. Thermal cycling results and economic analysis confirm that both PEGs are potential PCMs for passive solar thermal management purposes. Highlights Synthesis of polyethylene glycol-based binary eutectic mixtures. Accelerated thermal cycle test of eutectic mixtures. Binary mixtures were found chemically stable. Charging/discharging rates of PEG are controlled. Novelty Statement This paper presents the thermal performance of two polyethylene glycols, viz., PEG2000 and PEG10000. These materials were melted and solidified 1500 times for testing their suitability as thermal energy storage materials, and it was found that these materials are stable enough to store solar energy for five years. They found to be suitable for many solar energy storage applications.

Swelling performance of sodium polyacrylate and poly(acrylamide-co-acrylic acid) potassium salt

The application of superabsorbent polymer hydrogels is gaining much research attention. Industrial applications include agriculture, environmental engineering, biomedical and tissue engineering, oilfield, construction and electrical products, personal care products, and wastewater treatment. In this study, the swelling performance and adsorption kinetics of two commercial superabsorbent polymer hydrogels were evaluated based upon their stimuli response to pH and salinity at varying temperature and reaction time periods. Characterisation and evaluation of the materials were performed using analytical techniques—optical microscopy, scanning electron microscopy, thermal gravimetric analysis, and the gravimetric method. Experimental results show that reaction conditions strongly influence the swelling performance of the superabsorbent polymer hydrogels considered in this study. Generally, increasing pH and salinity concentration led to a significant decline in the swelling performance of both superabsorbent polymer hydrogels. An optimal temperature range between 50 and 75 °C was considered appropriate based on swell tests performed between 25 c to 100 °C over 2-, 4- and 6-h time periods. These findings serve as a guideline for material technologist and field engineers in the use of superabsorbent polymer hydrogels for a wide range of applications. The study results provide evidence that the two superabsorbent polymer hydrogels can be used for petroleum fraction-saline water emulsions separation, among other applications.Graphic abstractHighlightsThe swelling performance of the two superabsorbent polymer hydrogels experimentally studied showed a maximum absorbency in the range of 270 to 300g/g.Thermal gravimetric analysis curves show that both superabsorbent polymer hydrogels are stable at high temperatures.Commercially available superabsorbent polymer hydrogels can be used in industrial water absorption applications.

High Performance Shape-Stabilized Phase Change Material with Nanoflower-Like Wrinkled Mesoporous Silica Encapsulating Polyethylene Glycol: Preparation and Thermal Properties.

Nanoflower-like wrinkled mesoporous silica (NFMS) was prepared for further application as the carrier of polyethylene glycol (PEG) to fabricate the new, shape-stabilized phase change composites (PEG/NFMS); NFMS could improve the loading content of PEG in the PEG/NFMS. To investigate the properties of PEG/NFMS, characterization approaches, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) analysis, and differential scanning calorimetry (DSC), were carried out. The characterization results illustrated that the PEG was completely adsorbed in the NFMS by physical adsorption, and the nanoflower-like wrinkled silica did not affect the crystal structure of PEG. As reported by the DSC test, although NFMS had a restriction influence on the activity of the PEG molecules, the melting and binding enthalpies of the PEG/NFMS could reach 136.6 J/g and 132.6 J/g, respectively. In addition, the TGA curves demonstrated that no evident weight loss was observed from 20 °C to 190 °C for the PEG/NFMS, and the results revealed that the PEG/NFMS had remarkable thermal stability. These results indicated that the NFMS is a potential carrier of organic phase change material for the preparation of shape-stabilized phase change composites.

Influence of natural ageing on the flame retardancy and thermal properties of intumescent flame retardant long glass fibre reinforced polypropylene composites

In this work, the composites based on long glass fiber reinforced polypropylene/intumescent flame retardant (LGFPP/IFR) were prepared by melt blending. This article presented an experimental research on the influence of combined environment elements in natural condition on the properties of LGFPP/IFR composites with 0–12 months ageing. The flammability and thermal properties of the composites were investigated by limiting oxygen index (LOI), UL–94 test, cone calorimeter test (CCT), thermal gravimetric analysis (TGA), mechanical properties test and energy dispersive X‐ray analysis (EDAX). The LOI values increased from 27.5 to 28.3 in 0–6 months ageing, and then decreased back, however, the TGA curves shift to the lower temperature. The thermal degradation kinetics were analyzed and the apparent active energy (E) of aged and unaged samples were calculated by Flynn‐Wall‐Ozawa method. The results indicated that much lower E values were obtained after 3–12 months ageing. EDAX data proved that the IFR particles gathered on the surface of samples in natural exposing, by which had some effect on the thermal stability and flame retardancy of the composites. The mechanical properties showed a global decrease in the whole ageing period by matrix degradation and interface debonding under the influence of combined environment elements. POLYM. ENG. SCI., 58:2098–2105, 2018. © 2018 Society of Plastics Engineers

Prediction of higher heating values of combustible solid wastes by pseudo-components and thermal mass coefficients

A method was developed for the prediction of the higher heating values (HHVs) of combustible solid wastes (CSWs) by considering the thermal mass coefficients and the HHVs of pseudo-components. The pseudo-components include cellulose, hemicellulose, lignin, and starch for biomass based CSWs, and PE, PVC, PP, PS and PET for plastic CSWs. The thermal mass coefficients of the pseudo-components were determined by thermal gravimetric analysis (TGA). The TGA curves were used to determine the corresponding thermal mass coefficients by linear regression. The proposed model was also validated by experiments using 49 types of CSWs.

Investigation on the path process of M doped ZnO (M = Gd, Mg) via the sol-gel method from dried gel to stable nanostructure powder

Doping is one of the effective methods to modify the physical properties of ZnO material in order to extend its applications. An investigation on Zn1-xMxO (M = Gd, Mg and x = 0.00, 0.03) nanopowders that have been synthesized by sol-gel method and sintered at 600 °C for 2 hours was reported. The decomposition process of the dried gel system was investigated by thermal gravimetric analysis (TGA) and the nanopowders with different heating temperature were studied using FT-IR spectroscopy. The crystal structure of the nanopowders after sintering at 600 °C was obtained using X-ray diffraction (XRD). The TGA curves of the samples showed the various weight loss regions corresponding to the removal of starting materials and no weight loss was observed in the temperature range of 300 to 800 °C which corresponded to the phase-crystallization step. The FTIR spectra showed that ZnO band was assigned to the stretching frequency at 669 cm-1 while Gd/Mg doped ZnO was at 668 cm-1 and 666 cm-1. From the XRD studies, the crystal structure of the samples indicated single phase ZnO crystalline and confirmed hexagonal wurtzite structure (space group of P63mc).

Effect of functionalization of carbon nanotubes on mechanical and electrochemical behavior of polyaniline nanocomposite coatings

Functionalization of carbon nanotubes (CNTs) is recognized to enhance their dispersion nature and improves the overall performance of the CNT-polymer nanocomposite. In this current study, effective attempt of constructing nanocomposite comprised of polyaniline (PANI) and functionalized CNTs has been done for the purpose of surface protection of mild steel (MS). The synthesized nanocomposites were investigated in terms of morphology, chemical structure and thermal stability with scanning electron microscope (SEM), attenuated total reflectance infrared (ATR-IR), UV–visible spectral and thermal gravimetric analysis (TGA) methods, respectively. SEM investigations evidenced the uniform fibrous morphology in PANI/CNT nanocomposites with nanometer-sized diameters. TGA curves confirmed the enhanced thermal behavior of PANI with the inclusion of functionalized CNTs. The improved corrosion performance of PANI/CNT nanocomposite in 3.5% NaCl solution was corroborated by electrochemical impedance spectroscopy, electrochemical frequency modulation and potentiodynamic measurements. The origin of such enhanced corrosion protection property is explained from the view point that the interfacial interactions between functionalized CNTs and PANI matrix, greatly improves at the polymer/filler bond stability resulting in a better corrosion performance.

In Situ Synthesis of Carbon Nanotubes/Graphene Nanoplatelets Hybrid Materials with Excellent Mechanical Performance

A two-step method for the preparation of hybrid materials consisting of multi-walled carbon nanotubes (MWCNTs) attached to graphene nanoplatelets (GNPs) was proposed. Firstly, poly (acryloyl chloride) was grafted in situ onto the surface of MWCNTs. Secondly, the obtained MWCNTs (MWCNTs-PACl) were reacted with acid-treated GNPs to form a nanotube–polymer–graphene hybrid. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA) were used to investigate the forming of the hybrid materials. FTIR results showed that MWCNTs/PACl and GNPs were successfully bridged by chemical bonds like O – C = O and C – O – C . Raman spectroscopy furthermore revealed that acryloyl chloride can be used to connect the MWCNTs and GNPs due to the defects of MWCNTs, and consequently the defects of the hybrid materials were limited. Meanwhile, TEM observation demonstrated the nanostructure clearly in which the MWCNTs with a polymer layer were attached successfully on the surface of GNPs. And TGA curves reflected that the content of MWCNTs and GNPs was about 46.5% in the hybrid materials. In addition, the tensile tests results showed that MWCNTs/GNPs hybrid materials can improve the mechanical performance of epoxy composites in higher degree, compared with MWCNTs or GNPs particles alone.

Characterization of Polypyrrole Hydroxyethyl Cellulose/TiO2 Nanocomposite: Thermal Properties and AFM Analysis

Polypyrrole–hydroxyethylcellulose/TitaniumDioxide (PPy-HEC/TiO2) nanocomposite was synthesized via in situ chemical oxidative polymerization method at room temperature in water and water/ethyl acetate solution in the presence of ferric chloride (FeCl3). The effect of TiO2 nanoparticles and HEC on the characteristics of products such as thermal stability and morphology was investigated. The fabricated composite and nanocomposite morphology and structure were examined by atomic forced microscopy (AFM), Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and Thermal gravimetric analysis (TGA). The AFM images of products indicated that hydroxyethylcellulose decreased the surface roughness of nanocomposite. Also, hydroxyethylcellulose decreased particle size. The molecular structure of product was determined by FTIR spectroscopy. The results of XRD confirmed crystalline structure of TiO2 nanoparticles and partly crystalline structure of PPy-HEC/TiO2 nanocomposite. Thermogravimetric analyzer (TGA) was used to study the thermal behavior of nanocomposite. The TGA curves indicated that TiO2 and HEC enhanced thermal stability of products.

Effect of the number of TGA curves employed on the biomass pyrolysis kinetics results obtained using the Distributed Activation Energy Model

The Distributed Activation Energy Model (DAEM) is widely used for determination of characteristic parameters of pyrolysis kinetics from a certain number of experimental thermal gravimetric analysis (TGA) curves obtained at different heating rates. The number of heating rates employed to obtain different TGA curves varies between different authors, being typically between 3 and 5. The validity of DAEM has been discussed by several authors based on its capability of describing the devolatilization kinetics of the samples. Nevertheless, to our knowledge, there are no studies available in the literature evaluating the uncertainties associated to the simplified DAEM method or quantifying the effect of considering different numbers of TGA curves in the analysis. Therefore, we studied the effect of the number of TGA curves considered in this work, as well as the effect of considering or neglecting the uncertainties of different measurement parameters employed in the calculation. The characterization was carried out using four types of biomass (pine wood, olive kernel, thistle flower and corncob) employing up to 9 different heating rates between 10 and 40K/min during the TGA tests. Activation energies and pre-exponential factors were given and their uncertainties were reduced by increasing the number of TGA curves obtained at different heating rates. Nonetheless, considering measurement uncertainties during the calculations reduces significantly the final uncertainties of the pyrolysis parameters, permitting the reduction of the number of TGA curves used in the analysis.

Structural and optical properties of new yellow emitting iridium(iii) complexes and their application as an active layer component in white organic light-emitting diodes

Iridium(III) complexes containing two 2-(3-fluorophenyl)-4-methylpyridine and one branched alkyl side group on the 2,2′-bipyridine ligand were synthesized and characterized by UV-Visible, fluorescence, FTIR, NMR spectroscopies, thermal gravimetric analysis (TGA) and cyclic voltammetry. The complexes containing 4-dihexylmetyl-4′-heptyl-2,2′-bipyridine, 4,4′-bis(3-ethylheptyl)-2,2′-bipyridine and 4-(3-ethylheptyl)-4′-methyl 2,2′-bipyridine are named as CS137, CS138 and CS139, respectively, and exhibit a yellow emission band at around 590 nm. The photoluminescence quantum yields are in the range of 0.63–0.72 in chlorobenzene. The TGA curves of the complexes present high decomposition temperatures above 280 °C. The HOMO and LUMO energy levels are in the range of −5.36–(−5.43) eV and −3.21–(−3.27) eV, respectively. Solution processed organic light-emitting diodes are fabricated by the use of these complexes as dopants at various concentrations in the poly(N-vinyl carbazole: 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene host. Almost no electroluminescence could be obtained from the blend containing CS139 whereas those of CS137 and CS138 resulted in white light. Commission Internationale de L'Eclairage (CIE) chromaticity coordinates shifted to the yellow region with the increase in complex ratio in the blend. The obtained device characteristics are attributed to the positive effects of higher steric hindrance in CS137 and CS138.