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The study area is the peaty bed of Nyíres-tó mire which is situated in the northeastern Alföld on the Bereg Plain. For this paper we used a digital photo interpretation method with which we reconstructed the former vegetation from black and white aerial photos, and made chronosequence of vegetation maps. The image segmentation method dissolves the photo into different objects (segments) by spectral and textural parameters. The segments consist of similar pixels, representing a unique ground object. We made the segmentation with the Definiens Inc. eCognition software. The stability of the mire was calculated with GRID-files. The historical vegetation maps show, that after many arid years, the tree or shrub dominant associations increased until the eighties. Later, the sufficient precipitation and the artificial flooding stabilised the tree covering. The analysis of GRID-files shown, that 45.77% of the pixels get code 1 (stable), 44.32% get code 2 (slightly changeable) and only 9.91% get code 3 (changeable). It means that almost half of the mire’s vegetation is the same as in 1952.

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Abstract  

The thermal behaviour of kaolinites intercalated with formamide, dimethyl sulphoxide and hydrazine has been studied by simultaneous TG-DTG-DTA-EGA and TG-MS techniques. The complexes can be decomposed completely without dehydroxylating the mineral. It was found that the amount of intercalated guest molecules per inner surface OH-group is close to unity for the formamide and dimethyl sulphoxide intercalates. For the intercalation of hydrazine it was found that hydrazine is locked in the expanded mineral as hydrazine hydrate and its amount is somewhat higher than that obtained for the other two reagents. The thermal evolution patterns of the guest molecules revealed that all the three reagents are bonded at least in two different ways in the interlayer space.

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Abstract  

The thermal behaviour of mechanochemically treated kaolinite has been investigated under dynamic and controlled rate thermal analysis (CRTA) conditions. Ten hours of grinding of kaolinite results in the loss of the d(001) spacing and the replacement of some 60% of the kaolinite hydroxyls with water. Kaolinite normally dehydroxylates in a single mass loss stage between 400 and 600°C. CRTA technology enables the dehydroxylation of the ground mineral to be observed in four overlapping stages at 385, 404, 420 and 433°C under quasi-isobaric condition in a self-generated atmosphere. It is proposed that mechanochemical treatment of the kaolinite causes the localization of the protons when the long range ordering is lost.

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Abstract  

The thermal behaviour of ordered kaolinites from Hungary and Australia intercalated with potassium acetate, cesium acetate and urea has been investigated by simultaneous TG-DTG-DTA, TG-MS, Raman microscopy and XRD. Remarkable changes in the thermal decomposition pattern of the intercalates were obtained as a function of the nature of the intercalating re-agents. Replacing the potassium cation to cesium leads to a change in the OH environments resulting in a more complicated dehydroxylation pattern. The urea intercalates can be decomposed completely without dehydroxylating the mineral, although further treatments are necessary to restore the original d-spacing.

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Journal of Thermal Analysis and Calorimetry
Authors:
F. Paulik
,
J. Paulik
,
M. Arnold
,
J. Inczédy
,
J. Kristóf
, and
A. Langier-Kuzniarowa
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Journal of Thermal Analysis and Calorimetry
Authors:
A. Langier-Kuzniarowa
,
J. Inczédy
,
J. Kristóf
,
F. Paulik
,
J. Paulik
, and
M. Arnold
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Journal of Thermal Analysis and Calorimetry
Authors:
Sara Palmer
,
J. Kristóf
,
Veronika Vágvölgyi
,
Erzsébet Horváth
, and
R. Frost

Abstract  

The mechanism for the decomposition of hydrotalcite remains unsolved. Controlled rate thermal analysis enables this decomposition pathway to be explored. The thermal decomposition of hydrotalcites with hexacyanoferrate(II) and hexacyanoferrate(III) in the interlayer has been studied using controlled rate thermal analysis technology. X-ray diffraction shows the hydrotalcites have a d(003) spacing of 10.9 and 11.1 Å which compares with a d-spacing of 7.9 and 7.98 Å for the hydrotalcite with carbonate or sulphate in the interlayer. Calculations show dehydration with a total loss of 7 moles of water proving the formula of hexacyanoferrate(II) intercalated hydrotalcite is Mg6Al2(OH)16[Fe(CN)6]0.5·7H2O and 9.0 moles for the hexacyanoferrate(III) intercalated hydrotalcite with the formula of Mg6Al2(OH)16[Fe(CN)6]0.66·9H2O. CRTA technology indicates the partial collapse of the dehydrated mineral. Dehydroxylation combined with CN unit loss occurs in two isothermal stages at 377 and 390°C for the hexacyanoferrate(III) and in a single isothermal process at 374°C for the hexacyanoferrate(III) hydrotalcite.

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Investigation of RuO2-IrO2-SnO2 thin film evolution

A thermoanalytical and spectroscopic study

Journal of Thermal Analysis and Calorimetry
Authors:
Elizabet Horváth
,
J. Kristóf
,
L. Vázquez-Gómez
,
Á. Rédey
, and
V. Vágvölgyi

Abstract  

The thermal evolution process of RuO2–IrO2–SnO2 mixed oxide thin films of varying noble metal contents has been investigated under in situ conditions by thermogravimetry-mass spectrometry (TG-MS), infrared emission spectroscopy (IR) and cyclic voltammetry (CV). The gel-like films prepared from aqueous solutions of the precursor compounds RuOHCl3, H2IrCl6 and Sn(OH)2(CH3COO)2–xClx on titanium metal support were heated in an atmosphere containing 20% O2 and 80% Ar up to 600C. Chlorine evolution takes place in a single step between 320 and 500C accompanied with the decomposition of the acetate ligand. The decomposition of surface species formed like carbonyls, carboxylates and carbonates occurs in two stages between 200 and 500C. The temperature of chlorine evolution and that of the final film formation increases with the increase of the iridium content in the films. The anodic peak charge shows a maximum value at 18% iridium content.

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Thermal decomposition of sabugalite

A controlled rate thermal analysis study

Journal of Thermal Analysis and Calorimetry
Authors:
R. Frost
,
J. Kristóf
,
W. Martens
,
M. Weier
, and
E. Horváth

The mineral sabugalite (HAl)0.5[(UO2)2(PO4)]2⋅8H2O, has been studied using a combination of energy dispersive X-ray analysis, X-ray diffraction, dynamic and controlled rate thermal analysis techniques. X-ray diffraction shows that the starting material in the thermal decomposition is sabugalite and the product of the thermal treatment is a mixture of aluminium and uranyl phosphates. Four mass loss steps are observed for the dehydration of sabugalite at 48°C (temperature range 39 to 59°C), 84°C (temperature range 59 to 109°C), 127°C (temperature range 109 to 165°C) and around 270°C (temperature range 175 to 525°C) with mass losses of 2.8, 6.5, 2.3 and 4.4%, respectively, making a total mass loss of water of 16.0%. In the CRTA experiment mass loss stages were found at 60, 97, 140 and 270°C which correspond to four dehydration steps involving the loss of 2, 6, 6 and 2 moles of water. These mass losses result in the formation of four phases namely meta(I)sabugalite, meta(II)sabugalite, meta(III)sabugalite and finally uranyl phosphate and alumina phosphates. The use of a combination of dynamic and controlled rate thermal analysis techniques enabled a definitive study of the thermal decomposition of sabugalite. While the temperature ranges and the mass losses vary due to the different experimental conditions, the results of the CRTA analysis should be considered as standard data due to the quasi-equilibrium nature of the thermal decomposition process.

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Abstract  

The formation mechanism of thermally prepared IrO2/SnO2 thin films has been investigated under in situ conditions by thermogravimetry combined with mass spectrometry (TG-MS) and infrared emission spectroscopy (IRES). Mixtures of varying composition of the precursor salts (SnCl22H2O dissolved in ethanol and IrCl33H2O dissolved in isopropanol) were prepared onto titanium metal supports. Then the solvent was evaporated and the gel-like films were heated in an atmosphere containing 20% O2 and 80% Ar to 600C. The thermogravimetric curves showed that the evolution of the oxide phases take place in several decomposition stages and the final mixed oxide film is formed between 490 and 550C, depending on the noble metal content. Mass spectrometric ion intensity curves revealed that below 200C crystallization water, residual solvent, and hydrogen-chloride (formed as a result of an intramolecular hydrolysis) are liberated. The decomposition of surface species (surface carbonates, carbonyls and carboxylates) formed via the interaction of the residual solvent with the precursor salts takes place up to 450C as evidenced by emission Fourier transform infrared spectrometry.

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