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•The thermal lag causes the heating-rate-dependent onset of melting temperature.•At larger samples, the onset temperature increases linearly with the heating rate.•At smaller sample ...mass, the onset temperature behaves nonlinearly.•This behavior is explained by using a heat flow model and an equation is derived.•The heating rate dependence for small samples and fast heating is corrected.
The thermal lag of DSC is a heating rate independent constant and influences the measured onset temperature of melting peaks and must be taken into account during the temperature calibration. In the literature, however, non-linear behavior of the measured onset temperature is reported for the case of high scanning rates and the use of small samples. Based on a conventional heat transfer model of a DSC a general relation of the heating rate and sample mass dependence of the onset temperature is derived. The reason of this unusual behavior is that the time for the melting event is less than the equilibration time of the DSC. The approach presented can be used to correct the onset temperatures in the case of non-linear behavior, which may occur in conventional DSC and Fast DSC (using chip sensors).
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•Novel Li2−2xK2xPbP2O7 system has been synthesized through the conventional melt-quenching method.•The amorphous and crystalline characteristics have been investigated using both XRD ...and DSC analyses.•The thermal characteristics have been investigated via the DSC technique.•The composition effect on the glass structure before and after crystallization has been explored through spectroscopic studies.•Dielectric relaxation phenomenon has been evidenced for all samples.
Novel Li2−2xK2xPbP2O7 system (x = 0, 0.2, 0.4, 0.6, 0.8, and 1 mol%) was synthesized through the conventional melt-quenching method. The amorphous and crystalline characteristics of the resulting compounds were investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The study assessed the effect of potassium doping on thermal parameters, including glass transition temperature (Tg), crystallization temperature (Tc), and overall thermal stability. The findings reveal that the stability does not consistently follow a single pattern with K2O doping. Notably, the Li1.6K0.4PbP2O7 glass exhibits the greatest stability. The addition of K2O led to a reduction of the density and an increase in the molar volume of the system. These observations align with FTIR results, which reveal that introducing additional potassium ions results in longer bond lengths and weaker bonds. The spectroscopic study was supported by Raman spectroscopy. Post-annealing XRD analysis revealed the presence of distinct crystalline phases that differed according to the K2O content The structure of the various phosphate groups in the synthesized materials after annealing was also analyzed using Fourier Transform Infrared (FTIR) spectroscopy. Moreover, dielectric studies were conducted over a range of frequencies, and the presence of the relaxation phenomenon as well as the influence of potassium content on dielectric features have been evidenced.
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•The cooling rate dependence of the glass transition is measured in a cooling rate range of more than six decades.•The cooling rate dependence of the glass transition can be described ...by a Vogel–Fulcher–Tammann–Hesse equation.•The influence of the heat transfer conditions in a Flash DSC is discussed.
The thermal glass transition of polystyrene (PS) is measured in a range between 0.003K/s and 4000K/s using a conventional DSC 1 and a Flash DSC 1 from Mettler-Toledo. The dependency between the cooling rate and the glass transition temperature is in accordance with the Vogel–Fulcher–Tammann–Hesse (VFTH) equation, as it is usually used for description of the frequency–temperature relationship of the dynamic glass transition (or main relaxation process). Furthermore we discuss the influence of the thermal lag on the measurement and develop correction methods.
Titanium tetrachloride (TiCl4) treatment processed by chemical bath deposition is usually adopted as pre- and post-treatment for nanocrystalline titanium dioxide (TiO2) film deposition in the ...dye-sensitized solar cell (DSC) technology. Pre-treatment influences positively the bonding strength between the fluorinated tin oxide (FTO) substrate and the porous TiO2 layer, blocking the charge recombination at the interface between the conduction glass FTO and the I3 a degree ions present in the Ia degree /I3 a degree red-ox couple. Additionally, TiCl4 post-treatment is a widely known method capable of improving the performance of dye-sensitized solar cells, in particular, the photocurrent collected from the device. In this study, the influence and effect of TiCl4 pre- and post-treatment on the TiO2 layer is proposed and compared to the untreated film. The relative DSC devices are characterized in terms of short circuit current density, open circuit voltage, fill factor, conversion efficiency and IPCE. The dark current characteristics of cells with a treated and untreated TiO2 layer are also shown in order to evaluate the effect of TiCl4 pre-treatment as a blocking layer.
The photo differential scanning calorimetry (photo-DSC) is an appropriate method to characterize photopolymers used in additive manufacturing (AM). Important process parameters such as optimal ...ultraviolet (UV) exposure time and reaction heat can be attained by this method. However, achieving reliable and meaningful results from photo-DSC experiments requires careful sample preparation, i.e. the selection of a suitable sample shape, sample mass and sample holder (crucible). The sample shapes drop and spread with 1.0 mg and 2.8 mg sample masses were investigated in this study. Three different times from sample preparation until the start of the measurement (0, 4 and 7 h) were tested, in order to investigate different surface effects such as oxygen-diffusion, prior UV-curing through ambient radiation and evaporation of volatile components. While the 1.0 mg spread sample shape offers the thinnest film thickness (40 μm) and thus the closest comparability to high resolution print jobs, the 2.8 mg drop shape offers a more robust sample preparation with minimized surface effects. To further reduce time-dependent surface effects, this study shows how a preexisting test protocol was shortened from 42 min to 24 min without losing measuring accuracy. Furthermore, to reduce evaporation, different covers were placed on different crucibles, which were tested over time in the device’s automated sample changer (ASC) that enables automated and consecutive measurements. The combination of a cold pressed 85 μL crucible covered with a 300 μL Al2O3 crucible, which is removed shortly before the actual measurement, provides the best sample preparation for the ASC since mass loss remains below 1% for up to 10 h. Finally, two two-part resin systems, namely a methacrylate-urethane and an acrylate-epoxy based resin that are used in Digital Light Synthesis (DLS) are characterized part by part as well as in mixed state. Together with the investigation of different temperatures and atmospheres, it was possible to identify not only the part with the photoinitiator and the type of system (radical or cationic), but also a difference between methacrylates and acrylates with the aid of the photo-DSC method.
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•The 1.0 mg spread sample shape has shortest times to peak.•The 2.8 mg drop sample shape is more robust towards time-dependent surface effects.•EPX 82 follows a radical not a cationic or hybrid reaction system.•The reaction heat of EPX 82 is almost twice as much compared to RPU 70.•Sample preparation for reduced mass loss with the ASC of the DSC is presented.
Authentic representative gum exudate samples from Acacia species namely Acacia senegal var. senegal (ASG), Acacia mellifera (AMF), Acacia seyal var. seyal (ASY), and Acacia tortilis var. raddiana ...(ATR), were physicochemically analyzed. The moisture, ash, nitrogen and protein content, pH, specific optical rotation, and number average molecular weight were found to be ranging from 9.76% to 8.35%, 3.40% to 2.05%, 0.243% to 1.549%, 1.610% to 10.378%, 4.45 to 4.94, −48.25 to +86.75 and 0.24×106 to 2.95×106 respectively. The 13C and 1H NMR spectra of gum samples showed similarity in individual sugar components, but characteristic patterns of each gum, were observed. FTIR spectra of the studied gums show the presence of the same functional groups in the four gums. DSC and TGA thermograms were characteristic for each gum. Evaluation of the functional properties of the four gums indicated that ATR gum bears the best emulsification characteristics in terms of emulsion’s stability and emulsification power.
•DSC measurements of the LiCl-UCl3, NaCl-UCl3, KCl-UCl3, LiCl-NaCl-UCl3, and NaCl-KCl-UCl3 salts.•Thermodynamic assessment of the LiCl-NaCl-KCl-UCl3 salt.•Heat capacity predictions of alkali uranium ...chloride molten salts.•Uncertainty assessment of DSC measurements.•High temperature XRD to suggest intermediate compound in NaCl-UCl3 system.
Thermodynamic descriptions of higher-order molten salt systems are essential for the effective application of molten salt technologies. However, for pyroprocessing and molten salt reactor development, a complete description of the key Li-Na-K-U(III) chloride system has yet to be provided. To remedy this, we applied the CALculation of PHAse Diagrams (CALPHAD) approach to all available phase equilibria and related thermodynamic measurements that include new differential scanning calorimetry (DSC) observations for pseudo-binary and pseudo-ternary systems to obtain consistent and accurate sets of thermodynamic properties. An outcome of that effort was the apparent discovery of a previously unreported intermediate compound in the NaCl-UCl3 system. In this effort, we adopted a unique approach to the quantification of uncertainty in phase equilibria obtained from DSC measurements, which can provide distinct advantages in phase diagram analysis. The methodology indicates that reported values of uncertainty are often underestimated. The assessed systems of the current effort were incorporated in the publicly available Molten Salt Thermal Properties Database - Thermochemical.
During ICTAC2020, a workshop was held on “Good laboratory practice in thermal analysis and calorimetry” for young researchers and beginners under the aegis of the Education Committee of ICTAC. ...Thermal analysis (TA) covers relationship between large number of sample properties and the temperature. Naturally, there is some technique for each property of the sample bringing versatility in TA. This review is devoted to the Workshop and has been refined for the benefit of the readers so that it helps them in obtaining useful qualitative and quantitative information about the effects of heat treatments on materials of all kinds. Recent trends in DSC, TG-FTIR, TG-MS, DMA, kinetics and nanocalorimetry have also been covered in this article.
Non-isothermal differential scanning calorimetry (DSC) was used to study the influences of particle size daver and heating rate q+ on the crystal growth and decomposition kinetics of amorphous ...N,N’-bis(3-methylphenyl)-N,N’-bis(phenyl)-benzidine (TPD). The macroscopic crystallization kinetics was found to be strongly dependent on q+. At high q+, the crystal growth proceeded dominantly from the mechanical defects acting as primary growth centers, with the corresponding activation energy being ∼70–80 kJ mol−1. At low q+, the crystalline phase was primarily formed from heterogeneous nuclei, with the activation energy for the growth process being ∼980 kJ mol−1. The prolonged nucleation led to extensive passivation of the surface mechanical defects with respect to their function as direct crystal-growth-accelerating centers. Temperature-resolved in-situ Raman microscopy has confirmed the conclusions derived from the DSC data and helped to identify the residual low-q+ defects-originating crystal growth as proceeding from volume-located micro-cracks. The X-ray diffraction analysis confirmed that TPD crystallizes into an identical phase under all circumstances. The thermal decomposition of TPD was found to proceed in a single step, by simple nth-order reaction kinetics with the activation energy of ∼120 kJ mol−1.
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•Crystal growth and thermal decomposition of TPD were studied by means of DSC.•Crystallization rate and thermal stability are strongly dependent on heating rate.•Prolonged nucleation leads to extensive passivation of surface mechanical defects.•Thermal decomposition of TPD proceeds with nth-order reaction kinetics.
The paper reports on the phase stability of the (FeCoNi)0.75Cr0.25-xCux HEA system with equimolar ratio of Fe, Co and Ni by differential scanning calorimetry (DSC) and measurements of physicochemical ...properties: density, electrical resistivity, Seebeck coefficient, thermal conductivity, and magnetic behaviour in a broad temperature region as well as hardness and elastic modulus at room temperature as a function of the gradual substitution of chromium by copper in a series of (FeCoNi)0.75Cr0.25-xCux alloys with different mole fraction of Cu (x = 0, 0.05, 0.1, 0.15 and 0.2). DSC measurements showed that all alloys are thermally stable. Increasing content of Cu was found (i) to increase the formation of a fcc Cu-rich phase, (ii) to strengthen ferromagnetic interactions, resulting in rising ordered magnetic moments, as well as in growing ferromagnetic transition temperatures, and (iii) to distinctly change physical properties like electrical resistivity, thermal expansion, and mechanical properties. Experimental data regarding the phase stability are supported by CALPHAD calculations.
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•Thermal stability and physical properties of HEAs (FeCoNi)0.75Cr0.25-xCux (x = 0–0.2).•Phase fractions of bcc, hcp and fcc phases evaluated by CALPHAD calculations.•Ferromagnetic-like magnetic order observed as function of Cr/Cu substitution.•TC increases with Cu content.•TC explained via the Slater – Pauling concept and can be read off from an growing valence electron count.
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