Emanation Thermal Analysis Research Articles

Mechanochemically Synthesised Zn<sub>x</sub>Cd<sub>1-x</sub>S Nanoparticles for Solar Energy Applications

The mechanochemical solid-state synthesis of ZnxCd1-xS nanoparticles from zinc acetate, cadmium acetate and sodium sulphide in a planetary laboratory mill is described. Through changing the molar ratio of the Zn and Cd precursors, ZnxCd1-xS nanoparticles of different composition were prepared. Structural, surface and morphological properties were investigated by XRD, XPS, SEM and UV-VIS. Diffusion structural diagnostics was characterised by the emanation thermal analysis (ETA) results measured on heating of the samples. The cubic phase was found to be stable under mechanochemical treatment, as determined by XRD. The mixed phases were found to have ideal solution behaviours. In addition, microstructural characterisation indicated that mechanochemical treatment resulted in a structural refinement with a surface weighted crystallite size about 2 nm. The additional information of microstructure development and transport properties of the samples on heating was obtained by ETA. The calculated lattice parameters of mixed crystals linearly depend on the composition of ZnxCd1-xS nanoparticles. The S(2p), Zn(2p) and Cd(3d) core levels of the ZnxCd1-xS nanocrystallites reveal two different types of sulphur, zinc and cadmium unlike bulk CdS and ZnS. The calculated results indicate that the quantum-size effect in the nanoparticles is not negligible. The differences in the absorption edge and the emission peak position of the nanoparticles depend not only composition. Applied high-energy milling is a facile, efficient, and scalable process that does not require a solvent and can be performed under ambient conditions. Therefore, it is a promising candidate for the production of nanocrystalline materials.

Use of emanation thermal analysis to characterize microstructure development during Portland cement hydration

Portland cement hydration has been investigated by emanation thermal analysis (ETA), based on the application of radon atoms as radioactive indicators. This method enabled us to characterize continuously changes in the microstructure of the cement paste at selected temperatures. The numerical simulation of time dependences of the emanating rate during cement hydration was carried out. An agreement between the mathematical model and experimental results of the ETA was obtained.

Hydration of tricalciumsilicate (Ca3SiO5) investigated by emanation thermal analysis

The method of emanation thermal analysis (ETA), based on the measurement of radon release from samples, has been used in the investigation of the tricalcium-silicate (Ca3SiO5) to characterize the microstructure development during the sample hydration. Results of the ETA made it possible to obtain the diffusion structural diagnostics of the material under in situ conditions of it is hydration. The influence of temperature and surface area of the tricalcium-silicate sample on kinetics of the sample hydration was characterized. Computer modeling of time dependences of radon release rate during hydration of tricalcium-silicate was carried out. A good agreement of the numerical model with the experimental results of the radon release was found.

Diffusion structural diagnostics of polycrystalline boron-doped diamond films

Emanation thermal analysis (ETA) has been used to characterize the thermal behavior of boron-doped diamond polycrystalline film samples prepared by microwave plasma-assisted chemical vapor deposition (MPCVD). The mobility of radon atoms in the diamond film samples was evaluated from the ETA results. From the diffusion structural diagnostics achieved by evaluating the ETA results it followed that the O-plasma treatment of the sample enhanced the mobility of radon atoms in the range of 50–200 °C, due to both structure disordering and removal of graphitic carbon. The structure disordering was suggested by the high-resolution XPS results. From the diffusion structural diagnostics data it followed that the annealing of the structure irregularities in the polycrystalline diamond films took place in the range of 250–450 °C, the annealing was more intense for the O-plasma-treated sample compared to the H-plasma-treated one, due mostly to the initially greater degree of structure irregularities.

ChemInform Abstract: The Role of Thermal Analysis in the Study of Oxide Superconductors

Since the discovery of high temperature oxide superconductors in 1986, synthesis became an important area in the direction of getting new materials with still higher J{sub c} and J{sub c} values. The various synthesis procedures have played a significant role in the nature of products and in turn on their physical properties. An optimization of the synthesis procedure is always desired and there is a need to establish new synthetic routes or to modify the existing ones. Thermal techniques, e.g., TG, DGAA, DSC, dilametry and so forth, in conjunction with other techniques, like X-ray diffraction, gas chromatography, and mass-spectrometry, play a significant role in the synthetic solid-state chemistry. Modern thermoanalytical techniques, like emanation thermal analysis (ETA), or thermopiezic techniques are of immense importance to study the various aspects of solids. The effect of oxygen partial pressure on the final product is also discussed in this review article. Other techniques, like high temperature XRD, thermodilatometry, and temperature programmed reduction (TPR), are also covered to elucidate several microscopic properties of the oxide superconductors. An emphasis is also made on thermoelectrometry and thermomagnetometry techniques.

Thermal behaviour of titanium dioxide nanoparticles prepared by precipitation from aqueous solutions

Thermogravimetry-differential thermal analysis, emanation thermal analysis, mass spectrometry detection, Fourier transform infrared and XRD were used to characterize thermal behaviour of titanium dioxide photocatalyst precursors prepared by precipitation at various conditions from peroxotitanic acid sols. The transmission electron microscopy HRTEM technique was used to characterize the surface microstructure. The sols contained TiO2 anatase particles of approximately 10 nm in diameter. During heating of the air dried samples, their chemical degradation took place giving rise to anatase. On further heating, the crystallization of anatase and formation of rutile phase was observed. To test the photocatalytic activity of the samples, the decomposition of 4-chlorophenol (4-CP) under ultraviolet and visible irradiation was monitored. It was shown that photocatalytic activities of the samples are comparable to the Degussa P25 photocatalyst reference material.

Use of emanation thermal analysis and evolved gas analysis in thermal study of zinc(II) benzoate complex compounds

Thermal behaviours of three zinc(II) benzoate complex compounds (two new with caffeine and urea), namely Zn(C6H5COO)2, Zn(C6H5COO)2·caf2, Zn(C6H5COO)2·u2, were characterized by using thermogravimetry (TG/DTG), differential thermal analysis (DTA), evolved gas analysis (EGA) with mass spectrometry (MS) detection and emanation thermal analysis (ETA). Temperature intervals of the stability of the compounds as well as the mechanisms of their thermal degradation were determined. From TG and DTA results it followed that the oxidative degradation of urea with CO2 or caffeine with CO2 from the investigated Zn(II) benzoate complex compounds takes place as the first step of their thermal degradation. In the second step of thermal degradation diphenylketone was release. The evolved gas analysis has been used to determine intermediate products of thermal degradation and temperature ranges of their evolution from the samples. From the emanation thermal analysis results it followed that changes in the surface area and microstructure accompanied the thermal degradation of the compounds studied and that no microstructure changes can be supposed in the resulting zinc oxide on heating from 650 up to 850 °C.

High surface area α-alumina preparation by using urban waste

A new method for preparing high surface area α-alumina from urban waste is proposed. The method consists of the precipitation of a precursor that contains bohemite mixed with a linear polymer and subsequently the thermal decomposition of the precursor by heating in nitrogen and air to 1200 °C. The resulting α-alumina consists of nanocrystals of about 100 nm aggregated into larger particles with relatively high surface area (12 m 2 g −1) and a significant macropore volume of 0.545 cm 3 g. Methods of X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) were used to characterize microstructure of prepared materials. Results of differential thermal analysis, thermogravimetry and emanation thermal analysis characterized the thermal behaviour of α-alumina precursors.

Characterization of layered double hydroxide Mg-Al-CO3 prepared by re-hydration of Mg-Al mixed oxide

Abstract Emanation thermal analysis, differential thermal analysis, thermogravimetry, X-ray diffraction, scanning electron microscopy (SEM) and surface area and porosity determination from nitrogen adsorption/desorption measurements were used to characterize the Mg-Al-CO3 LDH compound with the Mg:Al ratio 3:1 prepared by re-hydration of the Mg-Al mixed oxide. The mixed oxide was obtained after heating of the intial Mg-Al-CO3 LDH compound in air at 500°C for 2 h. The samples were re-hydrated by two ways namely in a distilled water at 20°C for 5 days or by moistening at 60°C in air with RH 80% during 10 days, respectively. The characteristics of the re-hydrated LDH samples were compared with the initial Mg-Al-CO3 compound. The influence of the re-hydration conditions on the microstructure, surface morphology and thermal stability of the regenerated Mg-Al-CO3 LDHs samples is discussed. It was demonstrated that the re-generation of the layered structure by the hydration of the mixed oxide in water or in air,...

Emanation thermal analysis study of brannerite ceramics for immobilization of hazardous waste

Brannerite based ceramics, designed as a matrix for immobilization of high level radioactive waste (HLW), was investigated from the viewpoint of microstructure changes and atomic transport properties caused by leaching of the ceramics at pH 2 and 11, respectively. Scanning electron microscopy (SEM) and emanation thermal analysis (ETA) techniques were used for this purpose. Surface morphology, microstructure changes and transport properties of both ‘as-leached’ and ‘as-prepared’ samples were compared and the effect of leaching on the thermal behavior of the ceramics samples heated in the temperature range from 20 to 1250°C was characterized. The mobility of radon in the brannerite ceramics was evaluated by mathematical modeling from ETA results. The thermal behavior of the non-leached brannerite ceramics sample and its natural analogue brannerite mineral was compared using the ETA.

Transport properties and microstructure changes of talc characterized by emanation thermal analysis

Thermal behavior of talc samples (from locality Puebla de Lillo, Spain) were characterized by emanation thermal analysis (ETA), DTA and TG. The ETA, based on the measurement of radon release rate from samples, revealed a closing up of surface micro-cracks and annealing of microstructure irregularities of the talc samples on heating in the range 200–500°C. For ground talc sample a crystallization of non-crystalline phase formed by grinding, into orthorhombic enstatite was characterized as a decrease of radon mobility in the range 785–825°C and by a DTA exothermal effect with the maximum at 830°C. ETA results characterized the microstructure development of the talc samples on heating and served to evaluate their radon mobility and transport properties on heating and cooling. Transport properties of the talc samples were evaluated by using ETA experimental data measured during heating to 600 and 1300°C, respectively, and subsequent cooling to room temperature.

Transport properties and microstructure changes of alumina coatings characterized by emanation thermal analysis

Emanation thermal analysis was used to characterize the thermal behaviour of alumina coatings as deposited on EUROFER 97 steel surface by filtered vacuum arc technique. Temperature ranges of the healing of cracks and structure irregularities observed by SEM were determined from the ETA results. Transport properties of the alumina coatings were assessed from the ETA results by the evaluation of radon diffusion parameters in the temperature range from 50 to 300°C. Healing microstructure irregularities of the alumina coatings can be expected in the range 300–700°C as indicated by the decrease of the radon release rate. From the ETA results it followed that the onset of healing the cracks observed by the SEM on the surface of one alumina coating sample can be expected at 430°C.

Thermal characterization of montmorillonite clays saturated with various cations

Emanation thermal analysis (ETA), thermogravimetry and high temperature XRD were used to characterize the thermal behavior during dehydration of natural Na montmorillonite (Upton Wyoming, USA) and homoionic montmorillonite (MMT) samples saturated with different cations, i.e. Li+, Cs+, NH4+, Mg2+ and Al3+. ETA results characterized radon mobility and microstructure changes that accompanied the mass loss of the samples due to dehydration on heating in air. A collapse of interlayer space between the silicate sheets after water release from the MMT samples was characterized by a decrease of the radon release rate, ΔE. Decreases in c-axis basal spacing (d001) values determined from XRD patterns for the different montmorillonite samples follow the sequence: $$ Mg - MMT > Al - MMT > Li - MMT > Na - MMT > NH_4 - MMT > Cs - MMT $$ The decrease of the radon release rate (ΔE) determined by ETA that characterized microstructure changes due to collapse of interlayer space corresponded well to differences in the c-axis basal spacing (Δd001) values determined from the XRD patterns before and after samples dehydration.

Emanation thermal analysis study of N-doped titania photoactive powders

Thermal behaviour of N-doped titania powders prepared by heat treatment of anatase in gaseous ammonia at 550 and 575°C, respectively, was characterized by emanation thermal analysis (ETA). The ETA results were used to assess transport properties of the samples subsurface using the mobility data of radon atoms previously incorporated into the samples to the depth of 60 nm. It was demonstrated that the radon permeability of anatase in the temperature range 50–500°C was enhanced for the N-doped titania as compared to the non-doped titania powder. Microstructure changes accompanying the anatase-rutile transition were pointed out from the decrease of the radon release rate in the temperature range 850–1000°C. The results of surface area and porosity measurements, DTA results as well XRD patterns supported the ETA results.

Thermal behavior of ground talc mineral

Microstructure development and thermal behavior of ground talc mineral samples (from locality Puebla de Lillo, Spain) was characterized by X-ray diffraction, scanning electron microscopy(SEM),surface area measurements differential thermal analysis, thermogravimetry and emanation thermal analysis (ETA).A vibratory mill and grinding time 5 min. was used to prepare the ground talc sample. It was found that grinding caused an increase in the surface area of the natural talc from 3 m2g-1 to 110 m2g-1. A decrease of particle size after sample grinding was observed by SEM. The increase of structure disorder of the ground sample and the crystallite size reduction from 40 to 10 nm were determined from the XRD results. ETA results revealed a closing up of surface micro-cracks and healing of microstructure irregularities on heating in the range 200-500?C of both un-ground and ground talc samples. For the ground talc sample a crystallization of non-crystalline phase into orthorhombic enstatite was characterized as by a decrease of radon mobility in the range 785-825?C and by a DTA exothermal effect with the maximum at 830?C. ETA results were used for the assessment of transport properties of the talc samples on heating.

Effect of grinding on thermal reactivity of ceramic clay minerals

The effect of grinding on thermal behavior of pyrophyllite and talc as commonly used ceramic clay minerals was investigated by DTA, TG, emanation thermal analysis (ETA), B.E.T. surface area (s.a.) measurements, X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Use of emanation thermal analysis to characterize thermal reactivity of brannerite mineral

Emanation thermal analysis (ETA) was used to characterize the thermal reactivity of amorphous brannerite mineral of general formula U1–xTi2+xO6 (locality El Cabril, near Cordoba, Spain). It was demonstrated that on sample heating up to 880°C microstructure changes taking place in the sample were accompanied by the formation of new radon diffusion paths, followed by their closing up during the final transformation of amorphous to crystalline brannerite in the range 900–1020 °C. Relative changes in structure irregularities that served as radon diffusion paths during heating and subsequent cooling of the sample to temperatures of 300, 550, 750, 880, 1020 and 1130°C, respectively, were determined from the ETA results. Mass losses in temperature ranges of 230–315, 570–760 and 840–1040°C were observed by thermogravimetry. Mass spectrometry indicated the release of CO2 mainly due to the decomposition of minor carbon amount in the brannerite mineral sample.

Preparation and characterization of titania based nanowires

A new method for preparation of titania nanowires with diameter around 10 nm and length up to 2–3 μm is described. The precursor was prepared from sodium titanate by adding ethylene glycole (EG) and heating at temperature of 198°C for 6 h under reflux. The sodium titanate glycolate formed by this way aggregated into 1D nanostructures and was subsequently transformed into titania glycolate during a chemical treatment with 98% sulfuric acid. Titania nanowires with variable amount of anatase and rutile were prepared by heating to temperatures in the range 350–1000°C. The precursor as well as titania based samples were characterized by X-ray diffraction, Infrared spectroscopy, Scanning electron microscopy, High resolution transmission microscopy, Thermogravimetry, Differential thermal analysis, Evolved gas analysis and Emanation thermal analysis. The nitrogen adsorption/desorption was used for surface area and porosity determination. The photoactivity of the prepared titania samples was assessed by the photocatalytic decomposition of 4-chlorophenol in an aqueous slurry under UV irradiation of 365 nm wavelength.

Thermal behaviour of ground vermiculite

Thermal behaviour of natural vermiculite (Santa Olalla, Huelva, Spain) was investigated by TG, DTA, emanation thermal analysis (ETA) and high temperature XRD on heating in the temperature range from 30 to 1100°C before and after vibratory mill grinding. Microstructure changes of natural and ground vermiculite samples were characterized by using ETA under in situ conditions of heating. By comparing the ETA and XRD results it was demonstrated that a decrease of radon release rate measured by ETA characterized the decrease in the interlayer spacing of the vermiculite samples that followed the dehydration.

Thermal behavior of Mg–Al–CO3 layered double hydroxide characterized by emanation thermal analysis

Abstract Emanation thermal analysis (ETA) was used to characterize microstructure changes during heating of Mg–Al–CO3 layered double hydroxide (LDH) in the temperature range of 293–1473 K. It was confirmed by ETA that the formation of an intermediate phase with grafted CO32– anions in the hydroxide layers took place in the temperature range of 508–523 K and the formation of Mg–Al mixed oxide (MO) occurred in the range 623–773 K. The small peak of the emanation rate at 603 K indicated the degradation of the layered structure and the broad peak in the range of 1073–1273 K characterized the onset of the separation of the decomposition products of MO into MgO and Mg2Al4O7. The ETA results revealed that dehydration of the product with grafted CO32– anions occurred at lower temperatures than that of the initial Mg–Al–CO3 LDH.