•New method was developed to derive kinetics from TGA–DSC at a single heating rate.•Equivalence of TGA–DSC and basket heating methods in kinetics analysis was proven.•TGA–DSC facilitates kinetics ...analysis of low temperature oxidation before ignition.•TGA–DSC is a cost effective method to analyze low temperature oxidation kinetics.
The present work was aimed at developing a method for determining the kinetics of low temperature coal oxidation based on thermogravimetric analysis and differential scanning calorimetry (TGA–DSC). The analyses of TGA–DSC on non-isothermal oxidation of three coals at a single heating rate were carried out. The measured heat release rates and derived apparent kinetic parameters of low temperature oxidation were compared with those from the tests of basket heating methods (crossing point temperature and heat release method). The results demonstrated the equivalence of the TGA–DSC technique and the basket heating methods in measuring the heat release rate and kinetics of coal oxidation in the temperature range of about 100–150°C. Moreover, the TGA–DSC method can also measure the kinetic parameters of coal oxidation at the temperatures from ∼150°C to that of ignition occurring, which were shown to be different from those at the temperatures below ∼150°C. Therefore, the TGA–DSC method developed here is promising to be applied as a cost effective technique for deriving the kinetics of low temperature oxidation to describe coal spontaneous combustion process prior to ignition.
A comparative study of the crystallinity of Polyetheretherketone by using density, DSC, XRD, and Raman spectroscopy techniques.
In this work, the microstructure of Polyetheretherketone is first ...analyzed with usual techniques such as density, Differential Scanning Calorimetry, X-ray Diffraction, and secondly, compared with Raman Spectroscopy. Assessing the degree of crystallinity of PEEK is challenging because of the different interpretation of the crystallinity according to each technique. The density measurement gives the highest most trusted absolute uncertainty for the degree of crystallinity, around 4%, compared to the other techniques. The Differential Scanning Calorimetry, usually used by the polymer community, overestimates up to 18% the degree of crystallinity due to a competitive phenomenon between crystallization and melting of PEEK over the same temperature range, and a fast crystallization. When Analyzing the X-ray Diffraction data, the degree of crystallinity is underestimated up to 11% as a consequence of the broad amorphous halo. Lastly, our investigation proves that Raman microspectroscopy is appropriate to determine the local crystallinity on the sample surface and compares 18 indicators in the same study. The 1651 cm-1 band shift has the highest correlation coefficient of 0.92 with the degree of crystallinity determined by density. This work attempts to correlate the results of degree of crystallinity of PEEK obtained by these four techniques in order to establish the best evaluation of this fundamental property for numerous applications.
•An original comparative analyse of PEEK microstructure with four techniques: density, DSC, XRD, Raman spectroscopy.•The Differential Scanning Calorimetry gives overestimate the value of the degree of crystallinity.•The X-ray diffraction gives underestimate the value of the degree of crystallinity.•Local characterization of the degree of crystallinity with Raman spectroscopy.•The band displacement at 1651 cm-1 of Raman spectroscopy has the highest correlation with the degree of crystallinity.
Fe3O4@SiO2 (FS) nanocomposite was synthesized through the co-precipitation method and utilized as a filler material in the polyvinyl alcohol (PVA) matrix to obtain PVA/iron oxide@silica Fe3O4@SiO2 ...(PFS) films. This study presents the synthesis and characterization of flexible polymer nanocomposites comprising polyvinyl alcohol (PVA) matrices embedded with iron oxide @ silica. Through the analysis of the composite, we observed a significant enhancement in the thermal stability of the nanocomposites with increasing Fe3O4@SiO2 content. X-ray photoelectron spectroscopy (XPS) spectra have been used to provide more information about the chemical state and electronic structure of the polymer film. Dielectric spectroscopy revealed notable improvements in electrical properties, including increased real electric modulus and permittivity. Mechanical investigation showed an improvement in the tensile strength, meanwhile, Young's modulus has improved from 341.2 to 1789.8 MPa, indicating that (PVA) and FS successfully complexed and interacted strongly. These findings underscore the potential of these nanocomposites for high-performance applications in energy storage devices and other fields requiring robust dielectric materials.
•PVA films with various Fe3O4@SiO2 nanoparticles concentrations were prepared via solution cast techniques.•Fe3O4@SiO2 nanoparticles were prepared by co-precipitation method.•The interaction between the polymer blend and iron oxide@SiO2 nanocomposites was revealed by the XPS and Raman analyses.•Employing TGA and DSC analysis, the PVA/Fe3O4@SiO2 (PFS) films thermal stability was evaluated.•Electrical, and Mechanical properties of PVA/Fe3O4@SiO2 (PFS) films were investigated.
The aim of this study was to analyze the fat extracted from natural and flavored casein. Casein is the main protein in milk, and it is made of structures called micelles. Pure casein is obtained ...through technological processes, and contains a small amount of fat that has not yet been characterized. Fat extraction was performed using the Folch method. The extracted fat was examined by gas chromatography and differential scanning calorimetry. The fatty acid profile of the separated fats was determined using gas chromatography. A total of 20 fatty acids were found, and their content was compared with data on milk fat found in the literature. The analysis showed that the tested fat was dominated by saturated fatty acids, of which palmitic acid had the highest content—31.93%. The obtained results for all three tested caseins were comparable to each other, and no significant differences were noticed when comparing them to milk fat. The melting profiles of fat were analyzed by DSC technique, and it was found that an endothermic transition had occurred. Differences in the number of endothermic peaks were noticed when comparing the tested fat to milk fat. The fat from the casein contained two endothermic peaks for the medium-melting and high-melting fractions, while there was also an endothermic peak in the milk fat for the low-melting fraction.
Novel K5-xTlx(Mg0.5Hf1.5)(MoO4)6 (0 ≤ х ≤ 5) oxides were successfully synthesized by solid state reaction. The results indicate the formation of a continuous series of solid solutions with the ...NASICON-like structure (sp. gr. R3‾c) in the composition range 0 < x < 5. The unit-cell parameters of the solid solutions increase linearly with composition, as a consequence of thallium substitution for potassium. The cation conductivity of Tl5Mg0.5Hf1.5(MoO4)6 has been shown to exceed the conductivity of the parent potassium magnesium hafnium molybdate. The highest total conductivity of 2.49 × 10−3 S/cm was found at 831 K for Tl5Mg0.5Hf1.5(MoO4)6.
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An accurate and fast transient calorimetric ferrite core-loss measurement method is proposed in this article. In contrast to electrical measurements, the accuracy of the calorimetric approach is ...largely independent of the magnetic excitation and operating frequency. However, accurate values of the thermal capacitance and the temperature of the core under test (CUT) are required. Accurate measurement of the specific heat capacity of the core material can be achieved with a differential scanning calorimeter (DSC) or by using the CUT as a dc electric conductor and measuring its thermal response for known Joule heating. Accurate temperature measurements can be realized with NTC temperature sensors. A thorough uncertainty analysis of the presented method is conducted by identifying the impact of each source of uncertainty in the course of a sensitivity analysis. For the considered reference case (R 22.1/13.7/7.9 toroidal core with N49 ferrite material by EPCOS-TDK - 500 kHz/100 mT), the method achieves a total uncertainty with a worst-case value of less than 12% or, in case of a more realistic approach considering a Gaussian distribution of each source of uncertainty, a mean value of −4.3% with a 95% confidence interval of <inline-formula><tex-math notation="LaTeX">\mathbf {\pm }</tex-math></inline-formula>3.2%. The results are verified by means of finite element method (FEM) simulations and experiments. Furthermore, a step-by-step description of the workflow for preparing and conducting the experiments is provided. The proposed method is tested experimentally and compared to a state-of-the-art electrical loss measurement method for MnZn N87 and N49 ferrite cores of EPCOS-TDK. In addition, it is used to measure the loss-map of the NiZn ferrite material 67 from Fair-Rite for very high frequencies up to 50 MHz, which enables the computation of the material's Steinmetz parameters.
•(GeSe4)100-x(As2Se3)x glasses with x in the range 0 ≤ x ≤ 100 are prepared by melt quenching.•Glass forming ability and thermal stability of all these glasses are found to be high.•These glasses ...exhibit minimum fragility indicating their melts are strong.•Melts of glasses in the range 0 ≤ x ≤ 30 are super strong in nature.•They transmit IR light over a wide wavelength range.
(GeSe4)100-x (As2Se3)x glasses in the GeSe4-As2Se3 pseudo-binary joint are prepared by the melt quenching method. In this tie-line, the entire composition 0 ≤ x ≤ 100 is characterized by fixed average network connectivity of 2.40, which is considered to be optimal connectivity as the number of constraints and the number degrees of freedom available to the atoms are balanced at this average connectivity. The glass forming ability of the glasses having this average connectivity of 2.40 is usually found to be maximum. Glass transition temperature (Tg) decreases till x = 30 and remains invariant in the range 40 ≤ x ≤ 70. For x > 70, Tg shows an increasing trend. The jump in specific heat capacity (ΔCp), non-reversing heat flow (ΔHnr), Tg and the optical bandgap (Eg) show a distinct change in the composition range 40 and 70 mol.% of As2Se3. The fragility index (m) lies in the range of 15 and 32 for all the prepared glasses, representing the strong nature of these glass forming melts in the (GeSe4)100-x (As2Se3)x glasses. The viscosity as a function of reduced temperature (Tg/T) shows almost an Arrhenius nature for 0 ≤ x ≤ 70 and for x > 70, a slight deviation from the Arrhenius behviour is observed. The structural network of these glasses primarily consists of GeSe4/2 and Se-Se chains for x ≤ 30. For 40 ≤ x ≤ 70, the network is dominated by AsSe3/2 pyramidal units and As-As homopolar bonds. For x > 70, the structural network is characterized by AsSe3/2 pyramidal units. All the prepared glasses are found to transmit infrared (IR) light over a wide wavelength range from 2 to 17 μm. The super strong nature of the melts indicates that optical devices can be easily made for IR applications.
The flash point (FP) temperatures of some lubricant and base oils were measured according to ASTM D92 and ASTM D93. In addition, the thermal stability of the oils was studied using differential ...scanning calorimeter (DSC) and thermogravimetric analysis (TGA) under nitrogen atmosphere. The DSC results showed that the FP temperatures, for each oil, were found during the first decomposition step and the temperature at the peak of the first decomposition step was usually higher than FP temperatures. The TGA results indicated that the temperature at which 17.5% weigh loss take placed (T17.5%) was nearly identical with the FP temperature (±10°C) that was measured according to ASTM D92. The deviation percentage between FP and T17.5% was in the range from −0.8% to 3.6%.
Background: Curcumin is a compound obtained from the rhizomes of Curcuma Longa. It has various pharmacological properties like anti-inflammatory, anti-oxidant, anti-hyperlipidemic, etc. However, it ...also has some limitations that restrict its use as a medicine. Material and method: In the present study, a eutectic mixture of curcumin and glycine (35% and 65%) was prepared to improve its dissolution rate and photostability, characterized by DSC, FTIR, and XRD studies. Result and discussion: After 40 minutes, the eutectic mixture dissolved 10-fold more than the parent drug. The photostability studies were conducted according to ICH Q1B guidelines; after the seventh day of accelerated photostability studies, curcumin-glycine eutectic mixtures showed 36% degradation, 34% less than pure curcumin. Conclusion: The present study revealed that the physicochemical properties of BCS class II drugs can be improved by forming an eutectic mixture.
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