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  • Author or Editor: A. Venkataraman x
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Thermal techniques viz., TG/DTA/DSC methods have been employed in understanding the formation and decomposition of hydrogen ferrite phase (H-F) as a metastable intermediate in the conversion of γ-Fe2O3·xH2O, to α-Fe2O3. Magnetic hysteresis measurements carried out at liquid N2 and at room temperature for the vacancy ordered γ-Fe2O3 and its H-F phase also supplement these studies.

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Abstract  

Synthesis of monophasic ultrafine molybdenum oxide at low temperatures by thermal decomposition of molybdenum acetylacetonate sol-gel is reported. The sol-gel is obtained through a solvent extraction technique from the organic solvent with the reduction in oxidation state of molybdenum. The thermal behaviour of the sol-gel is studied from the thermal analysis traces. The structural changes accompanying the thermal decomposition of the gel and the formation of monophasic molybdenum oxide is also reported with the help of X-ray diffraction and scanning electron microscopy techniques.

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Cobalt ferrite was synthesised by the thermal decomposition of a citrate precursor through a novel self-propagating combustion reaction (SPCR) and the progress of this reaction is explained. Cobalt ferrite obtained by this reaction is compared with the products obtained by heat treatment of the citrate complex. The thermal behaviour and structures of the precursor, the synthesised ferrite, and the other decomposition products are investigated.

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D. C. electrical conductivity instrument is used as a supplementary technique in thermal analysis, especially to understand the behaviour of thermal dehydration and decomposition of some iron(II) carboxylates. This paper deals with the thermal studies on iron(II) maleate trihydrate under static air, dynamic nitrogen and dynamic air. The intermediates obtained during the decomposition are characterised by XRD pattern, infrared spectral studies and micro elemental analysis.

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Interpretation of partial thermal decomposition mechanism of Dy2(SO4)3·8H2O

Thermal, electrical and spectroscopic techniques

Journal of Thermal Analysis and Calorimetry
Authors:
S. Basavaraja
,
A. Venkataraman
, and
Arabinda Ray

Abstract  

Partial dehydration of Dy2(SO4)3·8H2O was studied employing TG, DSC, D.C. electrical conductivity and spectroscopic techniques. The possible mechanism for the loss of water molecules (partial dehydration) was found to be random nucleation obeying Mapel equation based on TG trace. The DSC traces are supports the results of TG traces and are also utilized to understand the enthalpy changes accompanying the partial dehydration and phase transition accompanying the dehydrated samples. D.C. electrical conductivity studies are attempted to supplement these TG studies. Attempts are made to explain the structural changes accompanying dehydration on the basis of infrared spectra and X-ray diffraction and scanning electron microscopic studies.

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A novel combustion method of employing poly(ethylene glycol) with the precursor in a fixed ratio for the synthesis of ultrafine γ-Fe2O3 through a self-propagating combustion synthesis is reported. Four different precursors viz. ferrous hydroxide, ferrous oxalate dihydrate, ferric 8-hydroxyquinoline and ferric acetylacetonate are employed in this study for the conversion of these precursors to ultrafine g-Fe2O3 particles. The as synthesized γ-Fe2O3 samples are characterized by XRD, SEM and thermal techniques. A case study for the synthesis of γ-Fe2O3 employing ferric acetyl acetonate as precursor is reported. The importance of employing thermal analysis techniques in understanding the combustion synthesis is envisaged.

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Iron(II) tartrate two and a half hydrate (FeC4H4O6·2.5H2O) was prepared and its thermal dehydration and decomposition were studied with a simultaneous thermal analyser (TG/DTA/DTG) under atmospheres of static air, dynamic dry nitrogen and dynamic air. This study was supplemented with the two-probe d.c. electrical conductivity technique under the same atmospheres. Under all the above atmospheres, the thermal dehydration was found to be a two-step process. However, the thermal decomposition process was quite complicated, involving the formation of various metastable intermediates, includingγ-Fe2O3. The final product of decomposition under all atmosphere wasα-Fe2O3.

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Ten fresh water samples of wells and rivers from the environment of Tarapur Maharashtra Site were analyzed to evaluate and establish the fall out level of 137Cs activity concentration using large volume of water samples. A radiochemical separation method suitable for the analysis of large volume of water sample based on the adsorption of Cs isotopes on coated acrylic fibres was standardized. 134Cs isotope was used for monitoring the radiochemical recovery of the analysis. Radiochemical recovery was obtained in the range of 74–98% for a sample volume of 250 L or more. The fall out level 137Cs concentration in river/dam water was found to be in the range of 0.205 to 0.268 mBq L−1. The fall out level annual effective dose through water ingestion pathway for a member of public was evaluated to be 2.27 × 10−9 Sv.

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Abstract

Polycarbonate with γ-Fe2O3 and CuO dispersions were carried out by solvent casting method to make polycarbonate-γ-Fe2O3 and polycarbonate-CuO composite films. These films were characterized for the molecular structure through FTIR spectroscopy and crystallinity by X-ray diffraction (XRD) measurements. The morphology of polycarbonate-γ-Fe2O3 was found to be different from that of polycarbonate-CuO composite films based on the scanning electron micrograph (SEM) images. The thermal traces of composites are different from that of pure polycarbonate which indicating the catalytic decomposition when compared with virgin polymer which is oxidative decomposition. An understanding of the structure, morphology, and thermal behaviour of the composite films are envisaged in the present study.

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