M. R. Udupa

Bio: M. R. Udupa is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Thallium & Infrared spectroscopy. The author has an hindex of 3, co-authored 6 publications receiving 19 citations.

Thallium(I)‐Uranates(VI)

Abstract: The solid state preparation, thermal and hydrolytic characteristics of thallium(I)—uranates(VI) are described. The phases identified were Tl2UO4, Tl2U2O7 and a range of solid solution (Tl2O. 2,33 UO3Tl2O. 6 UO3). The thallium uranates are isostructural with the corresponding potassium uranates. Tl2U2O7 is the stable phase formed from the other uranates on hydrolytic treatment. The thallium uranates lose thallium(I) oxide on heating to temperatures above 750°C and the order of thermal stability is Tl2U6O19∼Tl2U3O10∼Tl2U2O7»Tl2UO4. Thallium(I)-uranate(VI) Die Darstellung (durch Festkorperreaktion), die thermischen und die hydrolytischen Eigenschaften der Thallium(I)-uranate(VI) werden beschrieben. Als Phasen wurden identifiziert: Tl2UO4, Tl2U2O7 und ein Gebiet fester Losungen (Tl2O. 2,33 UO3Tl2O. 6 UO3). Die Thalliumuranate haben gleiche Strukturen wie die entsprechenden Kaliumuranate. Tl2U2O7 ist die stabile Phase, die sich auch bei der Hydrolyse anderer Uranate bildet. Beim Erhitzen der Uranate uber 750°C verfluchtigt sich Tl2O; die Reihenfolge der thermischen Stabilitat ist: Tl2U6O19∼Tl2U3O10∼Tl2U2O7»Tl2UO4.

Preparation and Characterisation of a New Thallium(I) Uranate(VI), Tl4UO5

Abstract: A new thallium(I) uranate(VI) of composition Tl4UO5 was isolated and characterised by X-ray, i. r. and chemical analyses. The compound dissociated into thallium(I) oxide and Tl2UO4 on heating to 230°C and its subsequent thermal behaviour depended on the volatilisation and oxidation characteristics of the thallium(I) oxide released. Darstellung und Charakterisierung eines neuen Thallium(I)- uranates, Tl4UO5 Ein neues Thallium(I)-uranat(VI), Tl4UO5, wurde dargestellt und durch Rontgen-, IR- und chemische Analyse charakterisiert. Beim Erhitzen auf 230°C dissoziiert die Verbindung in Tl2O und Tl2UO4, und das weitere thermische Verhalten ist gekennzeichnet von der Fluchtigkeit und Oxydationscharakteristik des freigesetzten Tl2O.

Solid state reaction between dichromates and oxalates

Abstract: The thermal investigation of the reaction taking place between dichromates and oxalates in the solid state has been done taking two systems of potassium dichromate-potassium oxalate and sodium dichromate-sodium oxalate. The techniques employed include thermogravimetry, differential thermal analysis, infrared spectroscopy and X-ray diffraction studies. The results indicate a stoichiometric reaction of dichromate and oxalate in 1∶1 ratio to give the corresponding chromate as the sole product.

Solid state reactions in the potassium iodate and molybdenum(VI) oxide system

Abstract: The reaction between potassium iodate and molybdenum(VI) oxide in mixtures of different mole ratios has been investigated employing TG and DTA techniques in static air atmosphere. The products are characterised by infrared spectroscopy, chemical analysis and X-ray diffraction studies. The studies indicate the formation of mono-, di-, tri- and tetramolybdates of potassium from mixtures with 2∶1, 1∶1, 2∶3 and 1∶2 mole ratios of KlO3∶MoO3. The kinetics of the reaction was followed and the energy of activation values were computed.

Thermal behaviour of thallous perchlorate

Abstract: Thermal decomposition characteristics of thallous perchlorate are investigated in nitrogen and in air using TG and DTA techniques. Isothermal studies at 380°, 400°, 420° and 440° in air and in nitrogen showed that the relative amounts of the decomposition products, namely, thallic oxide and thallous chloride, depend upon both the temperature and the atmosphere around the sample. At low pressures (5×10−1 mm/Hg) there is volatilization of thallous perchlorate even at 200°.

Thermal decomposition kinetics of potassium iodate

Abstract: The effect of gamma ray irradiation on the rate and kinetics of thermal decomposition of potassium iodate (KIO3) has been studied by thermogravimetry (TG) under non-isothermal conditions at different heating rates (3, 5, 7, and 10 K min−1). The thermal decomposition data were analyzed using isoconversional methods of Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Friedman. Irradiation with gamma rays increases the rate of the decomposition and is dependent on the irradiation dose. The activation energy decreases on irradiation. The enhancement of the rate of the thermal decomposition of KIO3 upon irradiation is due to the combined effect of the production of displacements and extended lattice defects and chemical damage in KIO3. Non-isothermal model fitting method of analysis showed that the thermal decomposition of irradiated KIO3 is best described by the contracting sphere model equation, with an activation energy value of ~340 kJ mol−1.

SYNTHESIS AND HYDROGEN ABSORPTION KINETICS OF V4Cr4Ti ALLOY

Abstract: V4Cr4Ti alloy is synthesized by aluminothermy process followed by electron beam refining. Hydrogen absorption characteristics of the alloy have been evaluated by measuring the pressure composition isotherm (PCIT) at 57 °C temperature. Two plateau pressures are observed in the PCIT curve. Substantial decrease in the hydrogen absorption capacity of the alloy as compared to vanadium has been recorded. Hydrogen absorption kinetics of the alloy was investigated in the temperature range of 200–500 °C. Three-dimensional diffusion appears to be the rate controlling step of the hydrogen absorption. The apparent activation energy was calculated as 0.16 eV/atom-hydrogen.

Hydrogen absorption kinetics of V–Al alloy

Abstract: The vanadium–aluminum alloy has been prepared by aluminothermy process. The alloy ingot obtained was refined by electron beam melting and homogenized by vacuum arc melting technique. The refined alloy was crushed into small pieces. These pieces were kept isothermally in a thermobalance attached to the Sieverts apparatus for the hydrogen charging. Reacted fraction α was calculated using isothermal thermo-gravimetry method. The reacted fraction α–t data thus obtained have been linearly fitted over a suitable reaction mechanism function. Rate constants at different temperatures are determined using slope of these linearly fitted curves. Activation energy of hydrogen charging has been calculated using Arrhenius equation.

Overcoming Crystallinity Limitations of Aluminium Metal-Organic Frameworks by Oxalic Acid Modulated Synthesis.

Abstract: A modulated synthesis approach based on the chelating properties of oxalic acid (H2 C2 O4 ) is presented as a robust and versatile method to achieve highly crystalline Al-based metal-organic frameworks. A comparative study on this method and the already established modulation by hydrofluoric acid was conducted using MIL-53 as test system. The superior performance of oxalic acid modulation in terms of crystallinity and absence of undesired impurities is explained by assessing the coordination modes of the two modulators and the structural features of the product. The validity of our approach was confirmed for a diverse set of Al-MOFs, namely X-MIL-53 (X=OH, CH3 O, Br, NO2 ), CAU-10, MIL-69, and Al(OH)ndc (ndc=1,4-naphtalenedicarboxylate), highlighting the potential benefits of extending the use of this modulator to other coordination materials.

Thallium(I) Uranate(V)

Abstract: Reduction of thallium(I) uranates(VI) by diverse methods led to formation of only one thallium(I) uranate(V), namely, T1UO3. T1UO3 unlike KUO3 exhibits the pyrochlore structure. Its physical and chemical characteristics were examined and rationalised. Thallium (I)-uranat(V) Die Reduktion von Thallium(I)-uranaten(VI) fuhrst stets nur zu einem einzigen Thallium(I)-uranat(V), namlich T1UO3. Im Gegensatz zu KUO3 Pyrochlorstruktur. Seine physikalischen und chemischen Eigenschaften werden beschrieben.