Differential Thermal Analysis Measurements Research Articles

Evaluation and thermodynamic optimization of phase diagram of lithium niobate tantalate solid solutions

The lithium niobate–lithium tantalate solid solution’s phase diagram was investigated using experimental data from differential thermal analysis (DTA) and crystal growth. We used XRF analysis to determine the elemental composition of the crystals. The Neumann–Kopp rule provided essential data for the end members lithium niobate (LN) and lithium tantalate (LT). The heats of fusion of the end members, given by DTA measurements, are 103 kJ/mol at 1531 K for LN and 289 kJ/mol at 1913 K for LT. These values were used as input parameters to generate the data. This data served as the basis for calculating a phase diagram for LN-LT solid solutions. Finally, based on the experimental data and a thermodynamic solution model, the Calphad Factsage module optimized the phase diagram. We also generated thermodynamic parameters for Gibbs’ excess energy of the solid solution. A plot of the segregation coefficient as a function of Ta concentration was derived from the phase diagram.

Structural Characterisation of End-of-Life Cement–Asbestos Materials from Lithuania

Asbestos is a widely used name for natural silicate minerals with fibrous properties. Asbestos minerals were one of the most popular and cheapest raw materials used in the construction industry in the past when they was used in the form of cement–asbestos composite material. Nowadays, we know that asbestos possesses carcinogenic properties. Due to this fact, asbestos was banned in many countries including Lithuania. All asbestos-containing materials are considered waste and stored in special landfills, which causes significant environmental pollution. One of the methods proposed to solve the asbestos problem may be thermal treatment. In the present study, asbestos-containing wastes in the form of cement–asbestos materials were examined. These asbestos-containing materials were characterised via chemical analysis (XRF) connected with mineralogical phase analysis with powder X-ray diffraction (XRD) as well as scanning electron microscopy (SEM). The thermal decomposition of samples was studied via differential thermal analysis (DTA) and thermogravimetric measurements with evolved gas analysis (TG–EGA). It was found that thermal treatment is a possible way to destroy asbestos contained in cement–asbestos wastes and convert it into new mineral phases. The work also compared the obtained characteristics of asbestos waste with the characteristics of waste produced in other countries.

Structural and thermoluminescence properties of lithium borate glass matrices under UV and beta radiation.

In the present work, glass samples in the (100 - x)B2O3-xLi2O binary system, with x varying from 30 to 50 mol%, were prepared using the conventional melting and moulding method, with the main objective of evaluating the thermoluminescence response when exposing these materials to ultraviolet (UV) radiation. Complementary analysis based on density, optical absorption on the UV-visible region (UV-vis absorbance), Fourier transform infrared spectroscopy on the medium region, X-ray diffraction, and differential thermal analysis measurements were performed. Thermoluminescence measurements of vitreous samples showed glow curves with at least one peak with a maximum temperature of ~170°C after exposure to UV radiation in the temperature range 50-250°C. Samples were also exposed to beta radiation in the temperature range 25-275°C, also showing single peaks with a maximum temperature of ~150°C.

Structure and Luminescent Properties of Niobium-Modified ZnO-B2O3:Eu3+ Glass.

The effect of the addition of Nb2O5 (up to 5 mol%) on the structure and luminescent properties of ZnO-B2O3 glass doped with 0.5 mol% (1.32 × 1022) Eu2O3 was investigated by applying infrared (IR), Raman and photoluminescence (PL) spectroscopy. Through differential thermal analysis and density measurements, various physical properties such as molar volume, oxygen packing density and glass transition temperature were determined. IR and Raman spectra revealed that niobium ions enter into the base zinc borate glass structure as NbO4 tetrahedra and NbO6 octahedra. A strong red emission from the 5D0 level of Eu3+ ions was registered under near UV (392 nm) excitation using the 7F0 → 5L6 transition of Eu3+. The integrated fluorescence intensity ratio R (5D0 → 7F2/5D0 → 7F1) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites. The higher Eu3+ luminescence emission observed in zinc borate glasses containing 1-5 mol% Nb2O5 compared to the Nb2O5-free zinc borate glass evidences that Nb2O5 is an appropriate component for modifying the host glass structure and improving the emission intensity.

Thermodynamic and structural change of Cu-13.5Al-4Ni shape memory alloy aged under different pressures for equal times

In this study, Cu-13.5Al-4Ni shape memory alloy (mass %) was tested. The alloy samples, at different pressures, were aged for an equal period of 5 min. The physical properties of Cu-13.5Al-4Ni alloy samples aged for an equal period were investigated. Differential scanning calorimetry (DSC) was used to investigate the impact on thermodynamic parameters. The differential thermal analysis (TG/DTA) measurements were made to obtain the ordered-disordered phase transformations from room temperature to 1200 °C. X-ray diffraction (XRD) and optic microscope observation were used to examine the microstructure. Microhardness measurements were performed on alloy samples aged for an equal period. The physical properties of the samples aged at different pressures for an equal period were compared to the measurement results of the homogenous sample.

Tunable emission and energy transfer of B2O3–Bi2O3–AlF3 glass system doped with Eu3+/Dy3+

The structure and luminescent properties of the B2O3–Bi2O–AlF3 glass system doped with Eu3+/Dy3+ ions in different molar ratios were studied. A series of glasses were synthesized by the conventional melt quenching technique. Glass transition and crystallization temperatures were examined by Differential Thermal Analysis (DTA) measurements. The amorphous character of the prepared samples was confirmed by the X-ray diffraction (XRD) method. Raman and FTIR spectra were collected and deconvoluted to investigate the glass micro-structure. Luminescence spectra revealed that the added rare-earth ions can be excited by a single wavelength. The emitted color can be tuned by changing the ratios of the Eu3+/Dy3+ ions and the excitation wavelength. Furthermore, the influence of the addition of AlF3 on the luminescence and decay times was investigated. In the glasses with 10 mol% AlF3 an enhancement of the emission and excitation spectra was detected. The energy transfer analysis confirms the energy transfer between Eu3+ and Dy3+ ions in the glass matrix. Additionally, the results of this study indicate that the B2O3–Bi2O–AlF3 glasses doped with Eu3+ and Dy3+ can be used as a color tunable phosphor.

Redefine the existence form and function of water in potassium carbonate-based deep eutectic electrolyte

Here, we prepared a green and novel deep eutectic electrolyte (DEE) consisting of potassium carbonate (PC) and ethylene glycol (EG). The formation mechanism and microstructure of deep eutectic solvent (DES) were studied by FTIR, 1H NMR and molecular dynamics simulation. And physicochemical properties of DES were further investigated by thermogravimetric analysis, differential thermal scanning analysis and conductivity measurement. The influence of H2O on the microstructure, physical properties and electrochemical properties of PC-EG electrolyte were systematically investigated. The results showed that PC-EG-20 where PC:EG molar ratio was 1:20 had a wide liquid range and the highest conductivity. The supercapacitor assembled from PC-EG-20 and activated carbon had a voltage window of 2.0 V, a specific capacitance of 190 F g−1 and an energy density of 23.89 Wh kg−1. Especially, the capacitor also exhibited a wide liquid range from −50 to 100 °C. Although the addition of H2O may reduce the electrochemical stability window of DEE, it can improve ionic conductivity and decrease viscosity, thereby improving capacitance and rate performance. This work may promote understanding and extend the application of DEE in supercapacitors.

Characterization and formation mechanism of non-metallic inclusions in single bcc-phase high entropy alloy

This work aims to provide a fundamental study of inclusion characteristics in the single bcc-phase high entropy alloy (HEA), Mn-rich and Al-contained multicomponent system (Al-Cr-Mn-Fe-Co-Ni) was selected as the prototype alloy in this study. According to the differential thermal analysis (DTA) measurements, the solidus (TS) and liquidus (TL) temperatures of this alloy were in the range of 1225–1228 °C (1226 ± 2 °C) and 1268–1271 °C (1270 ± 2 °C), respectively. Non-metallic inclusions were investigated in a two-dimensional (2D) cross-section method as well as extracted by a three-dimensional (3D) electrolytic extraction method. It was found that AlN was the dominant inclusion phase, also a small amount of Al2O3 inclusions were observed. They formed in the liquid alloy and mostly presented as Al2O3-AlN agglomerates, where the size range of the AlN inclusions was larger than that of Al2O3. The theoretical calculation showed that AlN inclusion has a higher coagulation coefficient and collision rate than those of Al2O3 inclusions, which agrees well with the experimental observations. The inclusion characteristics of Al2O3 and AlN were closely related to the relative contents of O and N in the presence of high Al content in the alloy. The impurity elements of N and O were the key issues in controling the stable inclusion phase in high entropic alloy.

Assessment of thermal stability of two N-ethoxyethyl-N-methylpiperidinium borate ionic liquids by non-Arrhenian incremental kinetic method

Thermal stability of two borate-based ionic liquids (ILs) recently proposed as effective additive for high voltage batteries, N-ethoxyethyl-N-methylpiperidinium bis(oxalato)borate (BOB) and N-ethoxyethyl-N-methylpiperidinium difluoro(oxalato)borate (DFOB), was investigated. Thermogravimetry–differential thermal analysis measurements performed under nitrogen at 1, 2, 4, and 7 °C min−1 show gradual mass loss above 220 °C for both compounds. The TG curves were processed by isoconversional kinetic analysis under the assumption of non-Arrhenian behavior. The outcome of the analysis suggests that even the initial decomposition stages occur by a complex mechanism, probably via competing evaporation–decomposition paths with relative contributions varying with the heating rate. The service lifetimes estimated by the kinetic analysis result in a stability of DFOB up to 10-times higher than that of BOB in the 25–125 °C range. Further experiments were carried out by the Knudsen effusion mass spectrometry (KEMS) in order to get information on the composition of the vapor phase produced upon heating under effusion conditions. The mass spectra of the vapor phase showed a rapid onset of decomposition at 110 °C and 130 °C for BOB and DFOB, respectively, with a large release of the ion species with m/q = 98. This decomposition path dominates the simple evaporation to neutral ion pairs, which was nonetheless observed at m/q = 172 (integer cation). All the results seem to point toward a higher stability of DFOB compared to BOB, most probably due to the charge-stabilizing inductive effect of fluorine atoms.

Lithium ion conductivity, crystallization tendency, and microstructural evolution of LiZrxTi2-x(PO4)3 NASICON glass-ceramics (x = 0 - 0.4)

In this research, NASICON type (LiZrXTi2-X(PO4)3) glass-ceramics were fabricated (x = 0.1, 0.2, 0.3, 0.4). Lithium-ion conductivity along with the crystallization tendency and microstructural features were examined in this regard. Parent glasses obtained through melt quenching were converted to the glass-ceramic specimens after one-step heat treatment procedure. The resultant glass-ceramics were deeply explored by means of different techniques including scanning electron microscope, differential thermal analysis, X-ray diffractometry, and ionic conductivity measurements. According to the obtained results, presence of Zr4+ ions in the glass network and its gradual increase caused the enhanced crystallization temperature as well as declined crystallinity and microstructure coarsening. In all studied glass-ceramics, LiT2(PO4)3 solid solution was the dominant crystalline phase and Zr4+ ions partly substituted in the structure of this crystalline phase. Moreover, presence of Zr4+ ions in the glass composition resulted in diminished lithium-ion conductivity of corresponded glass-ceramics at ambient temperature. Consequently, total conductivity of specimen with the highest level of ZrO2 (x = 0.4) was measured to be 0.78 x 10-5 Scm-1, being considerably less than ionic conductivity of the base (x = 0) glass-ceramic (3.04 x 10-5 Scm-1). It seems that less crystallinity of ZrO2 containing glass-ceramics decreases required connectivity between the lithium-ion free paths and is responsible for the diminished ionic conductivity of these specimens.

Differential thermal analysis techniques as a tool for preliminary examination of catalyst for combustion

The need for more economical catalysts for various combustion reactions is continuously driving catalyst development. We present Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC) as suitable techniques for fast examination of catalyst activity for combustion reactions. The heat of reaction ΔHr generated at the catalyst in a combustible atmosphere is the measure for estimating the capability of the catalyst. Present investigations verify the reliability of both methods for the pre-selection of catalysts for further extensive investigations. To simplify the measurements and the result evaluation, a new measurement routine is introduced which is more suitable for rapid catalyst investigation than the conventional approach. For initial investigations, oxidation of 1% methane on a cobalt oxide catalyst was used. First, DTA measurements were performed. The vessel size and the amount of catalyst are considered as factors influencing the thermal signal. Simultaneous mass spectrometry measurements were used to better understand the formation of the DTA response. Comparable DSC investigations were then conducted. Finally, the behavior of catalyst was compared with two commercial palladium/alumina catalysts using DTA and DSC. Our investigations show that DTA and DSC are powerful methods to identify potential catalysts in a fast and reproducible manner, provided that all parameters influencing the thermal signal are kept constant.

Multi-stimuli, color switchable emitter by solvent induced polymorph synthesis

Polymorphism has drawn great attention in tuning organic solid-state luminescent materials by alteration of molecular packing structure and has considerable potential application in optoelectronic devices and fluorescence sensors. Herein, two polymorphs based on dicyanodistyrylbenzene (DCS) compound were obtained by solvent induced synthesis. We have comprehensively investigated photophysical properties (such as photoluminescence colors, lifetime and PL quantum yield) of the two polymorphs, blue one αDCFDCS (Aqua) and green one αDCFDCS (Green). The single crystal structure analysis and XRD powder pattern shows that there is a slightly packing dislocation in a-axis account for the difference between the two phases. Mechanical grinding can lead to an alternation in photoluminescence color from blue to green. The differential thermal analysis (DTA) measurement discloses αDCFDCS (Aqua) is the metastable state of the compound. Both of two polymorphs show thermochromic and can be reversibly switched upon heating and cooling, which is attributing to the crystal cell expansion with the temperature increasing revealed by in situ XRD. Moreover, fuming with NH3 also causes the color change via Lewis acid base reaction. Upon heating or being exposed to HCl, it will return to the original state. The results of the polymorphism not only provide an insight into molecular packing and emission properties, but also pave the way for understanding the solid luminescence change by the multi-stimuli response.

Impact of MnO on the structural, physicochemical, and dissolution properties of phosphate-based glasses

In this work, manganese was suggested to improve the durability of 50P2O5–33·33K2O–(11·11−x/2) CaO−(5·56−x/2) MgO –xMnO glasses with 0≤x≤ 2 mol%. Indeed, its effect on the glass structure, thermal properties, physicochemical properties, and in particular, dissolution behaviours have been studied. The conventional melt-quenching technique was used to produce glasses at 1000°C and they were characterised by differential thermal analysis, density and molar volume measurements, x-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. Dissolution behaviours were tracked by measuring weight loss and pH. Molar volume measurements showed that phosphate glasses become more compact by incorporating MnO. Structural characterisation using Raman and infrared spectra proved that the glass network is composed mainly of metaphosphate chains. The dissolution results showed that incorporating manganese was an effective method to change the phosphate glasses’ chemical durability due to their ionic crosslinking between the nonbridging oxygen atoms of the phosphate chains, corresponding to the change in thermal properties (Tg, Tc and Tf).

Compositional and thermophysical study of Al–Si- and Zn–Al–Mg-based eutectic alloys for latent heat storage

Abstract In this study, the eutectic temperature and latent heat of Al–Si- and Zn–Al–Mg-based eutectic alloys were determined using differential thermal analysis (DTA) and differential scanning calorimetry measurements in order to identify eutectic alloys for latent heat storage in the eutectic temperature ranges of 450–550 and 300–350°C. First, the eutectic compositions of the Al–Si–Cu–Mg–Zn and Zn–Al–Mg–Sn alloys were identified using scanning electron microscopy with energy-dispersive X-ray spectroscopy and DTA in two steps. In the second step, metallographic analysis was repeated until a uniform eutectic microstructure was obtained. Thermophysical analysis revealed that the eutectic temperatures of several types of Al–Si- and Zn–Al–Mg-based eutectic alloys were within the targeted temperature ranges with relatively high latent heat. These results confirmed that Al–Si- and Zn–Al–Mg-based eutectic alloys have suitable properties as phase change materials for use in the 300–350 and 450–550°C temperature ranges.

Phase transitions in multiferroic Bi1−xEuxFeO3 synthesized by sol-gel method

Bi1-xEuxFeO3 micropowders were synthesized by sol-gel method. X-ray diffraction shows that the crystal structure changes from rhombohedral to cubic symmetry at Dielectric properties and loss factor were investigated as a function of temperature. Neel temperature of the compounds was measured by differential scanning calorimetry and found to decrease from 668 K to 646 K for and bounce to 667 K for The Curie temperature TC which corresponds to the transition from ferroelectric to paraelectric phases was checked out using differential thermal analysis measurements. The TC value increases from 1130 K to 1135 K for while no transition was detected for in accordance with the structural transition from R3c to centrosymmetric Pm3m phase.

Ultra-Responsive MEMS Sensing Chip for Differential Thermal Analysis (DTA).

Ultra-responsive single-crystal silicon MEMS thermopiles for differential thermal analysis (DTA) are developed. Facilitated by a unique "microholes interetch and sealing (MIS)" technique, pairs of suspended thermopiles are batch fabricated in a differential form, with high-density (54 pairs) n-type/p-type single-crystal silicon thermocouples integrated within each thermopile (sample area ~0.045 mm2). The fabricated MEMS thermopile sensors exhibit outstanding power responsivity of 99.5 V/W and temperature responsivity of 27.8 mV/°C, which are more than 4 times higher than those reported for material thermal analysis. The high-responsivity MEMS DTA chips allow us to accurately measure the indium melting point at different heating rates of ~1-100 °C/s. We also perform DTA measurement of the dehydration process of CuSO4·5H2O and the crystals show three stages of losing water of crystallization before becoming anhydrous copper sulfate salt. Our high-performance, cost-effective MEMS sensing chips hold promise for rapid and accurate DTA characterization for a wide range of applications.

Structural, Vibrational, and Magnetic Characterization of Orthoferrite LaFeO3 Ceramic Prepared by Reaction Flash Sintering.

LaFeO3 perovskite ceramics have been prepared via reaction flash technique using Fe2O3 and La2O3 as precursors. The obtained pellets have been investigated using several techniques. The formation of LaFeO3 has been clearly confirmed by X-ray diffraction. The scanning electron microscopy micrographs have shown the microporous character of the obtained pellets due to the low temperature and dwell time used in the synthesis process (10 min at 1173 K). The orthorhombic-rhombohedral phase transition has been observed at approximately 1273 K in differential thermal analysis measurements, which also allows us to determine the Néel temperature at 742 K. The fitted Mössbauer spectra exposed the presence of a single sextet ascribed to the Fe+3 ions in the tetrahedral site. Finally, magnetic measurements at room temperature indicate the antiferromagnetic character of the sample.

Investigation of physical and optical properties of ZnO doped lithium boro bismuthate glasses

Lithium Bismuth Borate glasses with ZnO addition was examined in relation to their physical, structural, and optical properties from Differential Thermal Analysis and density measurement. Infrared absorption (IR) spectra were recorded to know structural details. The optical properties of these glasses were investigated by UV–VIS absorption spectra. The optical band gap obtained from Tauc’s plots had shown an increasing trend. The rising trend in optical band gap and descendant trend in cut-off wavelength is due to a reduction in NBOs this is evidenced by IR.

A new method in the synthesis of conductive polymers; synthesis, characterization, and investigation of photocatalytic properties of polyaniline.

As known, in the synthesis of conductive polyaniline polymer from aniline monomer, the polymerization medium must be acidic. In order to make the polymerization medium acidic, protonic acids such as HCl and H2SO4 are generally used. In this study, two acids have been used to make the polymerization medium acidic. One of them, as we know, is H2SO4 as a protonic acid. The other acid is the zinc ion, which is a Lewis acid. The metal ion has never been used for this purpose up to now. Two polyaniline polymers have been synthesized to prove that conductive polymers can also be synthesized in the presence of metal ions instead of protonic acid. One of them is the polyaniline polymer, synthesized in the presence of H2SO4(PANI). The other polymer is polyaniline polymer, synthesized in the presence of zinc ions as acid (PANI-Zn-PSS). The synthesized polymers have been characterized by using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), X-ray diffraction diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), Ultraviolet-visible spectrophotometer (UV-vis.), thermal analysis techniques (thermo-gravimetric analysis, TGA)/differential thermal analysis, DTA) and electrical conductivity measurements kit. The photocatalytic activities of polymers synthesized have been investigated by the degradation of methylene blue (MB) dye in aqueous medium under UV light.

One-Pot Terpolymerization of Macrolactones with Limonene Oxide and Phtalic Anhydride to Produce di-Block Semi-Aromatic Polyesters.

The synthesis of novel block copolymers, namely poly(limonene-phthalate)-block-poly(pentadecalactone) and poly(limonene-phthalate)-block-poly(pentadecalactone) is here described. To achieve this synthesis, a bimetallic aluminum based complex (1) was used as catalyst in the combination of two distinct processes: the ring-opening polymerization (ROP) of macrolactones such as ω-pentadecalactone (PDL) and ω-6-hexadecenlactone (HDL) and the ring-opening copolymerization (ROCOP) of limonene oxide (LO) and phthalic anhydride (PA). The synthesis of di-block polyesters was performed in a one-pot procedure, where the semi-aromatic polyester block was firstly formed by ROCOP of LO and PA, followed by the polyethylene like portion produced by ROP of macrolactones (PDL or HDL). The obtained di-block semiaromatic polyesters were characterized by NMR and GPC. The structural organization was analyzed through XRD. Thermal properties were evaluated using differential thermal analysis (DSC) and thermogravimetric measurements (TGA) either in air or in nitrogen atmosphere.