Differential Thermal Analysis Curves Research Articles

Mineralogy and a New Fertility Index of Alunite in the Fanshan Lithocap, Luzong Basin, Anhui Province, China

Alunite is used as a representative mineral for indicating deposits in lithocaps, and lithocaps are generally related to the porphyry–(high-sulfidation) epithermal mineralization system. The study of alunite is of theoretical and exploration significance for prospecting potential underlying porphyry and epithermal deposits. Studies on alunite geochemistry have made breakthroughs, but there is little research on alunite mineralogy, for example, using scanning electron microscopy (SEM) images, differential thermal analysis (DTA), and Fourier-transform infrared spectroscopy (FT-IR). This study mainly focuses on alunite micromorphological characteristics, weight loss changes with temperature, and ionic group structure, aiming to identify the relationship between these features and indications for prospecting. The Fanshan lithocap is located in the northwest part of the Luzong basin, Anhui province of China, and it can potentially be used for exploring porphyry and epithermal deposits. Fanshan alunite is formed in two stages with three types of alunite. IA alunite is formed in the early hydrothermal stage and replaces felsic minerals in the Zhuanqiao Formation, IB alunite is formed in the later hydrothermal stage and fills in open spaces with bladed particles, and II alunite is the product of pyrite oxidation and reaction with other minerals in the supergene stage. Alunite electron microprobe data and energy-dispersive spectroscopy data further confirm temperature decreases with hydrothermal evolution, and the presence of a high-sulfidation epithermal system in the Luzong basin. Aside from the forming environment, SWIR, and geochemistry of alunite, there are other indication indexes; for example, the larger peak values at 3480 cm−1 and smaller peak values at 1080 cm−1 in FT-IR spectra and the deeper exothermic valleys at 750 °C and steeper weight loss slopes in the DTA curve suggest a favorable formation environment for alunite and provide valuable indications for deposit exploration and assessments of mineralization potential.

Study on mechanical performance and mesoscopic simulation of nano-SiO2 modified recycled aggregate concrete

Utilizing nano-SiO2 (NS) to reinforce the old mortar and the weak interfacial transition zone (ITZ) in recycled coarse aggregate (RCA) is a productive approach to enhance the quality of RCA. Throughout this paper, RCA was immersed in NS solutions with different concentrations (2, 5, 10 and 30 wt%). Subsequently, a systematic evaluation of the crushing index and water absorption of the treated NS modified recycled coarse aggregate (SRCA) was conducted. In addition, the calcium hydroxide (CH) content of RCA before and after modification was analyzed by Thermogravimetric and Differential Thermal Analysis (TG-DTA) curves. This study finds that the performance of SRCA modified with 2% concentration achieves comparable modification effects to other concentrations. Additionally, this paper delves into the impact of NS powder on the slump characteristics and compressive strength of concrete. Considering the above research and economic costs, this study adopts 2% concentration of NS for RCA modification and further investigates the stress-strain relationship of NS modified recycled aggregate concrete (SRAC) with various SRCA replacement ratios. Moreover, this paper establishes mesoscopic models of SRAC for various replacement rates and proposes constitutive models corresponding to these rates. The results indicate that when the SRCA replacement rate is within 60%, the stress-strain curve shape of SRAC closely resembles that of natural aggregate concrete (NAC); when the replacement rate exceeds 60%, the descending segment of the SRAC stress-strain curve becomes more precipitous, showing a higher tendency towards fragility in the concrete.

Preparing of CuCo2O4 compound by Sol-gel method and studying its structural properties

The CuCo2O4 compound has been prepared by the Sol-gel method starting with cobalt sulfate CoSO4.7H2O and copper nitrate, using Pectin as a stabilizer. The samples have been annealed at different temperatures (400-1000°C) to produce CuCo2O4. Thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) techniques have been used to characterize the compositional properties of the prepared compound. The optimum temperature for synthesis is found at 600°C. According to X-ray diffraction patterns, CuCo2O4 spinel has a face-centered cubic crystal (FCC) and belonged to the Fd3m space group. The lattice constants, unit cell volume, and number of formulas have been calculated. Their values are 8.044 Å, 520.49 Å3, and 8, respectively. It is found that the grain size of the compound is 17.4nm. The experimental results for d corresponded to the reference card values with an accuracy of 99.5% as a minimum. The theoretical and experimental density of the prepared compound have been calculated and the results are approximately identical. The differential thermal analysis curves showed five thermal effects, the most important of which are the exo-thermal peak at 390°C and end-thermal peak at 740°C, which indicate to start forming and decomposition of Cu respectively. The IR spectroscopy encouraged our results during the bonding vibrations of Co-O, Cu- O.

Conductive nano-Al/polyaniline composites prepared via mechanical milling

The conductive nano-Al/polyaniline composites were prepared by the milling method in the solid state. Here, aluminum nanostructures were prepared in two different mechanical methods, wire drawing and wire milling in the presence of lubricant oil. The effects of the preparation methods on the structures and morphologies of aluminum nanostructures were investigated by XRD and FESEM. The results show that the shape and size of aluminum nanoparticles in the preparation by the wire drawing method are significantly different than the wire milling method. The aluminum nanostructures were prepared by milling method have flake-like nanosheets while the wire drawing method leads to the formation of spherical ultrafine nanoparticles, which particles size are in the range of 30–60 nm. Then, polyaniline was produced using a solid-state polymerization process by the chemical reaction between aniline hydrochloride and potassium peroxydisulfate. Finally, nano-Al/polyaniline composites were prepared by mechanical milling at room temperature. The quantitative analysis was carried out with the materials analysis using diffraction (MAUD) method and weight fraction for aluminum and PANI were calculated 6.66% and 93.34%, respectively. Electrical conductivity measurements show the conductivity (1.2 × 10−2 S cm−1 at 25 °C) for polyaniline emeraldine salt and (1.02 × 10−3 S cm−1 at 25 °C) in nanocomposite respectively. The results show that by adding aluminum nanoparticles to the polymer the conductivity of nanocomposite (Al/PANI-ES) is lower than that for pure (PANI-ES). Thermogravimetry and differential thermal analysis curves show pure (PANI-ES) and nanocomposite (Al/PANI-ES) have a similar thermal degradation process. The total weight loss in TG curve of pure PANI-ES, in the temperature range 45–800 °C is 46.28% but, total weight loss observed in nanocomposite is 38.67%. Therefore, nanocomposite has higher thermal stability than that of the pure PANI-ES.

Investigating the thermal behavior of acyclovir

Viruses are a significant health, economic and social issue. Acyclovir (ACV) is an antiviral agent analogous to the guanine nitrogenous base that acts by interrupting the multiplication of DNA of virus in infected cells. The thermal decomposition mechanism of ACV was evaluated by thermoanalytical techniques Thermogravimetry/derivative thermogravimetry (TG/DTG), differential thermal analysis (DTA), evolved gas analysis by thermogravimetry coupled to vibrational infrared spectrometry in gas phase (TG-FTIR), differential scanning calorimetry (DSC), hot stage microscopy (HSM) and mass spectrometry (MS). TG/DTG and DTA curves were performed under N2 and air atmospheres. Under N2, four stages of mass loss were observed from the TG curve between 523-1273 K, while under air decomposition occurred in a similar way, however, the additional burning of carbonaceous material was found in air. DSC curves were obtained in heat-cool-heat mode, from 233 to 543 K, under N2 atmosphere and presented two endothermic peaks related to water loss and phase transition followed by exothermic crystallization of a new form, followed by melting associated with decomposition in agreement with HSM images. Powder X-ray diffraction (PXRD) profiles confirmed the phase transitions. From the TG-FTIR characterization, it was suggested that decomposition undergoes by release of water, 1,3-dioxolane, isocyanic acid, carbon dioxide, carbon monoxide, and ammonia. MS spectrum of the residue collected at 543 K revealed the presence of guanine free base as decomposition product in agreement with the release of dioxolane ring in gas phase.

Structure, thermal and crystallization behavior of lead-bismuth silicate glasses

Lead-bismuth silicate glasses were synthesized using a standard melt-quenching technique, varying the compositions within the range of (80-x-y)PbO–(10+x)Bi2O3–(10+y)SiO2, where x and y were between 0 and 20 wt%. The glasses were subjected to comprehensive analysis, including X-ray diffraction, Fourier-transform infrared spectroscopy, differential thermal analysis, and dilatometry, to investigate their crystallization behavior, thermal properties, and structure. The obtained glass samples were confirmed to be amorphous through X-ray diffraction and scanning electron microscopy. Fourier-transform infrared spectra analysis indicated that the glasses consisted mainly of PbO4, BiO6, and SiO4 structural units. Differential thermal analysis curves were used to estimate the glass transition, crystallization, and melting temperatures, and the results showed increased thermal stability and decreased crystallization tendency with increasing SiO2 content in the glass. X-ray diffraction analysis was utilized to identify the specific crystalline phases that were formed after the glass was subjected to heat treatment. Dilatometric measurements demonstrated that the investigated glasses possess a wide range of coefficient of thermal expansion values (6.8–11.1 ppm/°C), a low glass transition temperature (335–475°С), and a low dilatometric softening temperature (355–505°С). These results have significant implications for developing oxide glasses with specific thermal characteristics suitable for a wide range of applications.

Effect of eggshell powder on the microstructural and thermal behavior of Al7075/waste eggshell surface composites produced by solid-state friction stir processing developed for potential thermal applications

Lightweight composite materials for potential thermal applications are the contemporary demand for manufacturing and aircraft industries where the possibility to improve and tailor the desired properties is based on the application. Carbonized eggshell powder is a solid lubricant with absorbent capability and has proven as a reinforcement for metallic base composites. In the present work, an attempt is made to investigate the effect of carbonized chicken eggshell powder (3 to 9% by weight) on the microstructural and thermal properties of Al7075 alloy processed by solid-state friction stir processing. An infrared thermography and three K-type thermocouples equipped with the base plate at three equal distances are used to measure the temperature with respect to time. The comparative study of microstructure and grain structure analysis has been done by light microscopy, scanning electron microscopy, and electron backscattered diffraction methods. The findings explored the dynamic recrystallization and grain recovery with a reduced grain size of 6.2 to 10.3 µm at a varying percentage of eggshell powder (3 to 9%) in the stir zone. The thermal conductivity and coefficient of thermal expansion (CTE) were measured for the temperature range of 50 to 400 °C. In addition to it, differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), and derivative thermo-gravimetric analysis (DTG) are conducted for the temperature range of 25 to 900 °C to discuss the endothermic, exothermic nature, and degradation characteristics. The result revealed the decreasing trend of thermal conductivity, and CTE values were found in the range of 97 to 53 W/mK and 26.6 to 24 × 10−6 K−1 (heating cycle), 27.2 to 23.8 × 10−6 K−1(cooling cycle), respectively. Furthermore, the higher and lower thermal conductivity of 108 W/mK and 62 W/mK is observed at higher and lower terminal voltages, 250 V and 100 V, respectively. The DTA, TGA, and DTG curves explored the maximum weight loss, which varies up to 5.25% with exothermic peaks and decomposition steps for each surface composite.

Simultaneous photocatalytic removal of organic dye and heavy metal from textile wastewater over N-doped TiO2 on reduced graphene oxide

Methylene blue (MB) and hexavalent chromium(Cr(VI)) are hazardous pollutants in textile waste and cannot be completely removed using conventional methods. So far, there have been no specific studies examining the synthesis and activity of N–TiO2/rGO as a photocatalyst for removing MB and Cr(VI) from textile wastewater. This work especially highlights the synthesis of N–TiO2/rGO as a photocatalyst which exhibits a wider range of light absorption and is highly effective for simultaneous removal of MB-Cr(VI) under visible light. Titanium tetrachloride (TiCl4) was used as the precursor for N–TiO2 synthesis using the sol-gel method. Graphite was oxidized using Hummer's method and reduced with hydrazine to produce rGO. N–TiO2/rGO was synthesized using a hydrothermal process and then analyzed using several characterization instruments. The X-ray diffraction pattern (XRD) showed that the anatase N–TiO2/rGO phase was detected at the diffraction peak of 2θ = 25.61. Scanning electron microscopy and transmission electron microscopy (SEM-EDS and TEM) dispersive X-ray spectrometry images show that N–TiO2 particles adhere to the surface of rGO with uniform size and N and Ti elements are present in the N–TiO2/rGO combined investigated. Gas absorption analysis data (GSA) shows that N–TiO2/rGO had a surface area of 77.449 m2/g, a pore volume of 0.335 cc/g, and a pore size of 8.655 nm. The thermogravimetric differential thermal analysis (TG-DTA) curve showed the anatase phase at 500–780 °C with a weight loss of 0.85%. The N–TiO2/rGO composite showed a good photocatalyst application. The photocatalytic activity of N–TiO2/rGO for textile wastewater treatment under visible light showed higher effectiveness than ultraviolet light, with 97.92% for MB and 97.48% for Cr(VI). Combining N–TiO2 with rGO is proven to increase the light coverage in the visible light region. Removal of MB and Cr(VI) can be carried out simultaneously and results in a removal efficiency of 95.96%.

Crystallization kinetics analysis of Ge18BixSe82-x chalcogenide glasses alloys by using non-isothermal methods

The melt quench method is used to prepare the chalcogenide glass Ge18BixSe82-x (x: 0.5, 2, 4, 6, and 8 at percent). The samples are characterized using X-ray diffraction (XRD) and a scan electron microscope (SEM). The kinetics of crystallization of the chalcogenide glasses under consideration are investigated by using Differential Thermal Analysis (DTA) under non-isothermal conditions. Different models are used to calculate the activation energy of crystallization (Ec). The Kissenger-Akahira-Sunose (KAS) method is used to calculate the change of activation energy with crystallization volume fraction (Ecα). As well, the activation energy of glass transitions is measured by using different models. The results of fitting the experimental DTA data to the computed DTA curves show that the Johnson-Mehl-Avrami (JMA) model cannot represent the crystallization process of Ge18BixSe82-x glass. Our findings show that the Sestak-Berggren (SB) model is better suited to describe the crystallization process for the glass under investigation.

Role of Sm2O3 on surface to bulk crystallization and thermal properties of Fe2O3-V2O5-B2O3-SiO2 glasses

Non-isothermal crystallization kinetics of SiO2-B2O3-V2O5-Fe2O3-Sm2O3 glass and glass-ceramics are investigated using experimental and theoretical approaches. In order to gain insight into the thermal behaviour of the glasses, Sm2O3 is systematically replaced with Fe2O3 in the glass composition. Differential thermal analysis (DTA) curves of glass and glass-ceramics are obtained at various heating rates. The DTA-derived characteristic temperatures are used as inputs for different theoretical models. Sm2O3 addition in place of Fe2O3 increases the tendency of surface to bulk crystallization with glass formation tendency in the present samples. The highest activation energy of crystallization is observed for the 40SiO2-40B2O3-10V2O5-10Fe2O3 (SM-0) sample. The activation energy is observed in the range of 220-425 kJ/mol. It is comparable to other glasses.

Non-isothermal crystallization kinetics of CaO-SiO2-B2O3-TiO2 glass studied by differential thermal analysis in the case of “site saturation”

Crystallization characteristics of the CaO-SiO2-B2O3-TiO2 glass have been studied using scanning electron microscopy, X-ray diffraction and differential thermal analysis techniques. The crystallization kinetic parameters of this glass were estimated under non-isothermal conditions using the Matusuta-Sakka equation. Glass with fine particles (<74 μm), case referred to as ‘‘site saturation’’, was used to obtain the non-isothermal differential thermal analysis curves. Bulk glass-ceramics with dense and nonporous morphology are obtained after the heating treatment indicating the strong heterogeneous nucleation at the junction of gain boundaries in the case of “site saturation”. As the content of TiO2 exceeds 18%, the predominant crystal phase changes from CaSiO3 to CaTiSiO5, until CaTiSiO5 becomes the only crystal phase of the glass at 26% TiO2. The crystallization activation energies, EG, are in the range of 245–514 kJ/mol. As TiO2 increases from 10% to 18%, crystallization ability of the glass decreases gradually and the crystallization corresponds to one-dimensional growth mechanism or surface crystallization, while as TiO2 further increases from 18% to 26%, not only does the glass show an increasing crystallization ability, but also the crystal growth changes to the two-dimensional growth mechanism. Within the range of 22%–26%, TiO2 plays the role of strengthening the crystallization of the glass by acting as a major component in the glass to form Ti-bearing compound. From the standpoint of glass-ceramics preparation, the glass containing more TiO2 (such as 26%) with CaTiSiO5 as the only crystal phase is favorable in the present study.

Mechanical, Oxidative Properties, and Wear Behaviors of CrAlSiN Coatings Applied on Cutting Tools

In this study, we investigated the mechanical and oxidation properties of WC-Co and CrAlSiN-coated turning inserts and analyzed their wear behaviors. CrAlSiN films were synthesized by radio-frequency magnetron sputtering from alloy targets. X-ray diffraction analysis indicated that all the prepared films have a cubic structure without any hexagonal phase. The average microhardness increased from 27 GPa for WC-Co up to 37 GPa for CrAlSiN, whereas the average frictional coefficient decreased from μ＝0.50 for WC-Co down to μ＝0.17 for CrAlSiN. During dynamic oxidation, the maximum exothermic peak in the differential thermal analysis curve was observed at 549 ℃ for WC, the main component of WC-Co, and at 1384 ℃ for CrAlSiN. Corresponding to the exothermic reactions, the mass gain determined by thermogravimetric analysis increased from 23% for WC to 6% for CrAlSiN. The wear behaviors of WC-Co and CrAlSiN-coated inserts were verified through the in situ measurement of cutting resistance and the observation of their flank wear after cutting tests. The minimum cutting resistance and width of flank wear were confirmed for CrAlSiN-coated inserts.

Thermal decomposition study of cadmium telluride (CdTe)

Pure CdTe crystalline material is synthesized at 1073 K temperature in a closed tube under vacuum in horizontal tubular furnace. The synthesized material is found to be stoichiometric having atomic % of Cd: 49.31 and Te: 50.69 as determined by energy dispersive analysis of X-ray. The material is CdTe phase with cubic unit cell structure possessing lattice parameters of a = b = c = 6.48 Å as determined by X-ray diffraction. The morphology of the as-synthesized material is studied by scanning and transmission electron microscopy. The morphology showed clusters of varying sizes ranging from sub-micron to nano having stacked layers. The Raman spectroscopy showed three peaks positioned at 91, 120 and 140 cm−1, corresponding to CdTe. The thermogravimetric, differential thermogravimetric and differential thermal analysis curves of synthesized CdTe are recorded in the temperature range of ambient to 1233 K for three heating rates of 10, 15 and 20 K⋅min−1. The thermocurves demonstrated one-step decomposition of the as-synthesized CdTe material. The thermodynamic parameters, such as activation energy (Ea), activation enthalpy change (ΔH*), Gibb’s free energy change (ΔG*), activation entropy change (ΔS*) and phonon frequency factor (A) are calculated by model-free isoconversional methods. The obtained data and outcomes are discussed thoroughly.

Fabrication of Efficient and Non-Enzymatic Electrochemical Sensors for the Detection of Sucrose.

Molecularly imprinted polymers have been used for the creation of an electrochemical sensor for the detection of sucrose, which are modified by using functionalized graphene (fG). Using AIBN as the free radical initiator and sucrose as the template, imprinted polymers are synthesized. The monomer, 4,4'-diisocyanatodiphenylmethane (DPDI), has both proton donor groups (N-H or O-H) and lone-pair donor groups (C=O). By creating H-bonds with electron donor groups (C=O), the proton donor group in this polymer may interact with the sugar molecule serving as its template. The sensor signals have improved as a result of the interaction between the monomer and the template. Thermogravimetric and differential thermal analysis (TGA/DTA) curves, scanning electron microscopy (SEM), and FT-IR spectroscopy have been employed to characterize the fabricated receptors. The fabricated sensor has exhibited a limit of detection of 16 ppb for the target analyte that is highly sensitive, linear, reversible, regenerative, and selective. Moreover, the sensor's stability, reproducibility, and reusability have been evaluated for six months, following the device's manufacturing, and the results revealed similar responses with the percentage error of less than 1%. Most importantly, this sensor has demonstrated a quick response time, which is very sensitive, stable, and selective.

Physicochemical Analytical Studies on Yttrium‐Doped Triglycine Sulfate Single Crystals

Single crystals of pure triglycine sulfate (TGS) and yttrium-acetate (0.5 mol%)-doped triglycine sulfate (YTGS) crystals are synthesized and the crystals are grown from aqueous solution by slow evaporation solution growth method. The grown crystals are subjected to single crystal and powder X-ray diffraction studies to identify the morphology and structure. Both the grown crystals are packed in a monoclinic crystal system and the lattice parameters of YTGS crystal are a = 9.138 Å, b = 12.72 Å, and c = 5.728 Å, whereas the doped TGS are, a = 9.134 Å, b = 12.61 Å, and c = 5.723 Å. The lattice parameters are slightly distorted due to the incorporation of yttrium ion into the lattice sites of the TGS crystal. The thermal stability of the grown crystals is investigated by differential thermal analysis (DTA) and thermogravimetric studies. DTA curve shows a lower decomposition temperature for YTGS crystal than for pure TGS crystal. The functional groups of the grown crystals are identified by Fourier transform infrared spectral studies. The surface morphology of the crystals is examined by scanning electron microscopy. Dielectric studies are carried out to identify the phase transition temperature and to find the dielectric constant of the YTGS crystals.

THERMOMECHANICAL PROPERTIES OF COMPOSITE MATERIALS BASED ON MIXTURES OF HIGH AND LOW DENSITY POLYETHYLENES

The results of the research into the influence of polymer components ratio - high density polyethylene and low density polyethylene, into the regularity of changes in thermomechanical properties are presented. The deformation was measured at varying temperatures and at a constant load of 0.5 kg/cm2 . The concentration of low density polyethylene varied from 10 to 100 wt%. Depending upon the test temperature, two physical states were recorded: solid and viscous-flow. It found that as the concentration of low-density polyethylene in the composition of the polymer mixture rose, the transition temperature in the softened state and the transition temperature in the viscous-flow state dropped. The differential thermal analysis curves showed that at low concentrations of high density polyethylene, two-phase systems were formed in the polymer system. The study of composites based on aluminum hydroxide and a mixture of high and low density polyethylene revealed a wave-like change in softening and viscous-flow temperatures.

Controllable synthesis of SrO-B2O3-SiO2-TiO2 glass-ceramics: Insight into the crystallization kinetics and dielectric properties

SrO-B2O3-SiO2-TiO2 (SBST) glass and glass-ceramics were prepared using the melt-quenching process with controlled crystallization kinetics. The influence of the Sr/Ti ratio on the structure, crystallization kinetics, and dielectric characteristics of SBST glass and glass-ceramics was investigated in detail. The samples were characterized using Raman spectroscopy, XPS spectroscopy, differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results indicate that a defined glass transition peak and two crystallization peaks were observed in the DTA curves of the SBST glass. The crystallization mechanisms of the two peaks were nucleation occurred on both the surface and inner phase. Most importantly, the SBST glass-ceramics showed excellent frequency and temperature stability, and especially SBST-1.10 glass-ceramics samples had dielectric losses as low as 1.07 × 10−3 (100 kHz, room temperature) and had excellent temperature stability (Δεr/εr298K < 10%) in the 298–500 K temperature range.

Characterizing hydrogen storage behavior of Mg-based materials catalyzed by S2− and O2− ions

Composites of Mg90Ce5Y5 + 5.0 wt % MoS2/MoO2 were produced by vacuum refining technology. The phase-composition and microstructure of the specimens were analyzed using X-ray diffraction, transmission electron microscopy, electron diffraction, and inductively coupled plasma optical emission spectrometry. The performance of hydrogen storage was analyzed using thermogravimetric and differential thermal analysis curves and a semi-automatic Sievert-type device. The results indicated that the catalytic MoS2 as a single phase was uniformly distributed in the matrix. However, the doping of MoO2 introduced O2− ions, which combined with Mg and Ce to form MgO and CeO2 phases, respectively. The MoS2-catalyzed alloy exhibited faster hydrogen absorption and desorption rates, which could absorb 4.5 wt % H2 in 120 s (at 573 K) and release 3 wt % H2 in 330 s (at 633 K). The initial dehydrogenation temperatures of the MoS2- and MoO2-catalyzed alloys were 467.7 and 475.7 K, respectively. The dehydrogenation activation energy of MoS2- and MoO2-catalyzed alloys were 103.7 and 110.2 kJ mol−1 respectively. Addition of MoO2 and MoS2 modified the decomposition enthalpy and entropy values, but these changes were very limited. Generally, S2− was superior to O2− ions in enhancing the hydrogen storage properties of the alloy.

Thermal and electrical transport property study of direct vapour transport grown Cu2SnS3 single crystals

Copper tin sulphide (Cu2SnS3) (CTS) single crystals are grown by vapour transport technique of direct (DVT) type. The stoichiometric compositional analysis; Cu: 40.78 % (37.21 %), Sn: 31.09 % (34.35 %) and S: 28.13 % (28.15 %); showed the crystals to be slightly copper rich and tin deficient, bracket values are standard data. The X-ray diffraction showed the CTS to possess cubic unit structure having lattice parameter of 5.43 Å. The high resolution transmission electron microscopy substantiated the crystalline character. The thermal analysis are carried out by recording simultaneous thermogravimetric, differential thermogravimetric and differential thermal analysis curves. These analysis are done in inert atmosphere for three heating rates of 10, 15 and 20 K⋅min−1 in the range from ambient to 1023 K. The thermocurves are analyzed by two standard methods of Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The thermodynamic parameters like activation energy, changes of entropy, enthalphy and Gibbs free energy are determined using KAS and FWO methods. These determined thermodynamic parameters of as-grown CTS single crystals matches each other stating the validity of the analysis. Temperature variation of electrical transport properties like dc electrical resistivity (ρ) and Seebeck coefficient (S) are measured in the temperature range of 323 K to 473 K. The values of ‘ρ’ decreases with temperature, stating semiconducting nature of crystals. The observed ‘S’ values are found to be positive in entire temperature range, stating crystals to be of p-type semiconducting nature.

Effect of natural phosphate content on the growth kinetics of hydroxyapatite crystals grown from kaolin clay

In the present study, the kinetics of hydroxyapatite formation in different kaolin-natural phosphate mixtures was investigated using X-ray diffraction (XRD) and differential thermal analysis (DTA) measurements. The XRD patterns revealed the presence of both kaolinite and hydroxyapatite phases in all of the mixtures and full disappearing of kaolinite phase in the heat-treated samples. According to the DTA curve results, both the peak temperature formation of hydroxyapatite and the relative fraction-transformed increased as the heating rate increased and the amount of phosphate in the mixture decreased. The activation energy of hydroxyapatite phenomenon was estimated using Kissinger and Ligero analytical methods. The obtained values of the activation energy were in the range of ∼196.5 and 210.6 kJ/mol. The growth morphology parameters n and m were both found to be near to half unity indicating that the surface nucleation with plate-like growth was dominant in hydroxyapatite formation controlled by diffusion.