Emanation Thermal Analysis Research Articles

In-situ monitoring of microstructure changes during the heating of amorphous ruthenia by means of Emanation Thermal Analysis

Results of Emanation Thermal Analysis (ETA), Thermogravimetry (TG) and Differential Thermal Analysis (DTA) of hydrous ruthenia measured during heating in argon from 20 to 1000°C are presented. The ETA results were interpreted using comparison with the results of TG, DTA, X-ray diffraction, transmission electron microscopy and surface area measurement. An agreement of the results was found. The ETA made it possible to monitor microstructure changes under in situ conditions of heat treatment of the samples.

Characterization of new silicate/oxide lamellar nanocomposites by emanation thermal analysis

Emanation thermal analysis was applied for the characterization of LaCo(fsa) 2en-montmorillonite nanocomposites [(fsa) 2en = N,N′-bis(3-carboxysalicydene)ethylenediamine], and the results were compared to the data given by thermogravimetry and evolved gas analysis. The emanating rate of Na-montmorillonite increases up to 250°C with the elimination of the intercalated water, and then decreases progressively, however, with a shoulder at about 650°C when the layers are dehydroxylated. On the other hand, the emanating rate of LaCo(fsa) 2en-montmorillonite increases up to 370°C, i.e., until the decomposition of the intercalated complex is achieved. Above 450°C, there is a rapid decrease of this rate, with only a slightly remarkable shoulder at about 650°C. The decrease of the emanating rate is characteristic for a decrease of surface area and porosity of the material, indicating that the thermal stability of LaCo(fsa) 2en-montmorillonite is rather lower than that of Na-montmorillonite.

Characterization of Montmorillonite Saturated with Various Cations

Emanation thermal analysis (ETA) supplemented by thermogravimetry (TG and DTG) and evolved gas analysis (water) were used for the characterization of the thermal behavior of montmorillonite samples saturated with lithium, sodium, magnesium and aluminum cations. The ETA revealed microstructure changes that occur during the gradual heating of the clay. These changes are associated with the dehydration, dehydroxylation and formation of an amorphous meta-montmorillonite phase, and its subsequent annealing and recrystallization. On the basis of the ETA results it was demonstrated that exchangeable metallic cations have a great effect on the thermal behavior of montmorillonite.

Thermal Behaviour of Silica Waste from a Geothermal Power Station and Derived Silica Ceramics

The silica waste originating from a geothermal power plant in Mexico was investigated with the aim of finding its applicability as a raw secondary material for ceramics production. The thermal behaviour of the original silica waste (containing NaCl and KCl from marine brine) and of the purified silica was characterized by means of DTA/TG, emanation thermal analysis (ETA) and thermodilatometry (TD). The reactivity of the purified silica waste mixed with CaCO3 (1.8 mass%) was characterized by means of ETA, DTA and TG. The microstructures and phase compositions of the final products prepared by heating in air were tested by means of X-ray diffraction and of scanning electron microscopy coupled with electron probe X-ray microanalysis. The thermal analysis methods allowed determination of the optimal conditions for thermal treatment of the silica waste in order to obtain partly sintered porous materials for use as refractory bricks.

Thermochemical Properties of Chemically Modified Zeolite

Zeolites chemically modified with 1, 4 or 6 M aqueous solutions of NaOH were studied by DTA, TG and ETA (emanation thermal analysis) in the temperature range 201–200°C. The structural changes in the modified zeolites at room temperature and in the modified zeolites annealed at 1000°C were studied by XRD analysis. Thermal analysis demonstrated dehydration, dehydroxylation, structural changes and a glass transition. A gradual loss in crystallinity of the chemically modified zeolites was also observed. XRD analysis revealed structural changes caused by chemical treatment and also by annealing.

THEORY OF EMANATION THERMAL ANALYSIS IX. Inert gas release during thermal decomposition of solids

In the Emanation Thermal Analysis the release of inert gas atoms previously incorporated in the sample is measured. Results of the statistical modelling of the inert gas release during thermal decomposition of solids are presented. The updated model supposing three components in the solid-state reaction system including the formation of an intermediate metastable component on the surface of the newly formed component was proposed for the modelling of the ETA curves. The release of inert gas atoms previously incorporated into the sample is used as a probe of microstructure changes. The random nucleation mechanism was considered in the modelling. The model can be used in modelling ETA curves of solid-solid, solid-gas and solid-liquid interactions where the existence of metastable intermediate component is supposed.

Emanation thermal analysis of low-density polyethylene irradiated by electron beam

The thermal behaviour of low-density polyethylene (LDPE) as powder and pellet have been characterised by means of the emanation thermal analysis (ETA) during heating in air. The ETA was used in the study of LDPE polymer before and after irradiation to various doses of high energy electrons. It was shown that the ETA reflects microstructure changes taking place as the result of thermal degradation and oxidation pyrolysis of the polymer samples. It was shown in the study of LDPE products, resulting after the electron-beam treatment, that the results of ETA reflect structural changes caused by the radiation over the range of absorbed doses from 0 to 20 MGy. The annealing chemical radicals produced by the electron-beam irradiation was assessed by comparing ETA curves measured during first and second heating runs.

Emanation Thermal Analysis of Intercalated Montmorillonitic clay

Emanation Thermal Analysis (ETA), based on the measurement of the release of radon from previously labelled samples, has been used for 'in-situ’ characterisation of the morphology changes of intercalated montmorillonitic clay. The thermal behaviour of hydroxyaluminium intercalated montmorillonite was monitored in course of the preparation of alumina pillared montmorillonite, making possible to determine optimal temperature for the isothermal treatment of the intermediate product. Moreover, the thermal stability of alumina pillared montmorillonite porous structure was determined from the ETA data. A good agreement of ETA data and surface area, XRD patterns. DTA, and TG resulted was found.

Use of emanation thermal analysis in characterization of the influence of grinding on textural and structural properties of nanosized titania powders

It is shown that emanation thermal analysis (ETA) is a very sensitive method for studying the textural and structural changes undergone during thermal and/or mechanical treatment of TiO2. It is shown that the activation energy for the bulk diffusion of radon into titania samples annealed at 1100 °C dramatically increases by increasing the prior grinding time of the sample at room temperature. These results demonstrate that grinding of TiO2 prior to the annealing treatment considerably improves sintering and densification of the material.

The study of the dehydration and dehydroxylation of smectites by emanation thermal analysis

The dehydration and dehydroxylation of the smectites, beidellite and montmorillonite (dioctahedral) and saponite and laponite (trioctahedral), were investigated by ETA, DTA, TG and X-ray diffractions. There are differences between the behaviors of di- and trioctahedral clays which are due to the differences in the ability of the exchangeable cations to migrate into hexagonal holes of the SiO4 network and due to the fact that the dehydroxylation and recrystallization of dehydroxylated trioctahedral smectites occur simultaneously, whereas there is a temperature gap of about 300°C between the dehydroxylation and the recrystallization of dioctahedral smectites.

The emanation thermal analysis of kaolinite clay minerals

Emanation thermal analysis (ETA) is based on the measurement of the rate of release of radon from solid samples previously labelled with trace concentrations of an inert radioactive nuclide (Thorium-228 or Ra-224). This method enables pointing out of the different steps that occur during the heating of kaolinite: pre-dehydroxylation, dehydroxylation, evolution of structural disorder in metakaolinite, segregation of amorphous silica and formation of precursors of high-temperature phases, crystallization and sintering of both mullite and cristobalite. The investigations of two kaolinite samples of quite different crystallinity demonstrates the role of the structural disorder of the mineral in the manifestation of these structural changes. The differences observed between the behaviour of the two samples are reflected by different diffusivities of radon which can be related to different morphology changes taking place in kaolinite during heating. The results obtained demonstrate the potential of ETA as a complementary method of conventional thermoanalysis and XRD methods.

Characterization of iron(III) oxide and oxide-hydroxide as Sr-sorbent

Iron(III) hydroxide and oxide-hydroxide samples prepared by precipitation of 0.2M iron(III) nitrate solution by 5M NaOH and subsequently aged at pH 12 for times of up to 50 h have been characterized. The sorption properties towards Sr2+ were characterized by radiotracer method using85Sr, morphology of the samples was characterized by Transmission Electron Microscopy and Emanation Thermal Analysis. X-ray diffraction patterns characterized the crystallinity of the samples aged for various times. The maximum (100%) sorption capacity for85Sr corresponding to amorphous iron(III) hydroxide decreased to 75% with the time of precipitate ageing (up to 40 h). This finding corresponds to the development in crystallinity and morphology of the sorbent.

Differences in the thermal behaviour of natural quartz before and after mechanical grinding as observed by emanation thermal analysis

Emanation thermal analysis, which measures the release rate of radon from a sample previously labelled with trace amounts of thorium-228 and radium-224 on its surface, makes it possible to reveal differences in the thermal behaviour of quartz sand before and after mechanical treatment by milling, and indicates the formation and thermal recrystallization of the highly disordered silica layer resulting from the mechanical activation of the sample.

The phase transformation of caffeine: Investigation by dynamic X-ray diffraction and emanation thermal analysis

Abstract The solid-solid phase transformation of caffeine has been studied with time- and temperature-resolved X-ray powder diffractometry (TXRD) and with emanation thermal analysis (ETA). The phase transformation of caffeine at 141°C has been followed by heating a sample of the low-temperature phase. After cooling again, the high-temperature phase converts only slowly back into the low-temperature phase. This transformation needs weeks or months at room temperature to complete. With TXRD, it was possible to study this slow transformation in situ at elevated temperatures. A nucleation-controlled transformation mechanism appears likely.

Thermal behaviour of iron(III) oxide hydroxides

Abstract

Emanation thermal analysis in the characterization of zinc sulfide thin films prepared from different precursors

Zinc sulfide thin films were prepared by the Atomic Layer Epitaxy (ALE) process from zinc acetate and zinc chloride and studied by emanation thermal analysis (ETA). The effects of different precursors and growth temperatures were evident in the ETA curves. In the films grown from zinc acetate, thermally induced changes were detected below 95 °C and above 400 °C which can plausibly be attributed to a higher amount of volatiles and to a polymorphic transition, respectively. The cubic to hexagonal transition was confirmed by DSC. Doping with terbium distorts the crystal structure and causes the peaks to become poorly discernible.

ETA-DTA study of mechanically ground gibbsite

Simultaneous emanation thermal analysis (ETA), DTA and TG measurements show that upon mechanical grinding the structure of gibbsite changes from well-crystallized to amorphous, with a small proportion undergoing mechanochemical dehydration to form amorphous alumina, a precursor of η-A1 2O 3, which then transforms to α-alumina by, it is proposed, a diffusion mechanism.

Thermoanalytical study on surface reactivity and characterization of oxide powders at elevated temperatures

Thermoanalytical studies on the surface reactivity and characterization of oxide powders have been reviewed on the basis of the author's work between 1967 and 1992. Gas-flow DTA apparatus and the emanation thermal analysis method using 226Ra as parent isotope were successfully applied for investigating the surface behavior of powders at elevated temperatures.

Thermal behaviour of amorphous Li2ZrO3 prepared by sol-gel technique

The results of the investigations of thermal behaviour of Li2ZrO3, prepared in the amorphous state by means of sol-gel technique are demonstrated. The thermal treatment was carried out in air under constant heating rate of 5 deg·min−1 and cooling rate of 2.5 deg·min−1. The methods of DTA, TG, Emanation Thermal Analysis (ETA) and dilatometry were used, for characterization of the thermal behaviour in dynamic conditions. The X-ray diffraction patterns were used for characterization of the phase changes observed by TA Methods.

Emanation thermal analysis and its application potential

The principle of emanation thermal analysis, based on the measurement of inert gas released from solids, is given. The labelling techniques for sample preparation and the mechanisms of the inert gas release are discussed. The potential of emanation analysis in various fields is outlined.