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: Thermal decomposition & Chromium. The author has an hindex of 6, co-authored 31 publications receiving 133 citations.

Thermal decomposition of potassium perchlorate in presence of chromium(III) oxide and nickel(II) chromite(III)

Abstract: A study of the thermal decomposition of intimate mixtures of different molar ratios of potassium perchlorate and chromium(III) oxide, and potassium perchlorate and nickel(II) chromite(III) was conducted employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. Upon heating to 400°C Cr(III), in 2:1 molar ratios, is oxidized to potassium dichromate. Only a stoichiometric amount of Cr(III) was oxidized from molar ratios less than 2:1, leaving behind excess Cr2O3 and NiCr2O4 whereas from molar ratios greater than 2:1, Cr(III) was completely oxidized and the excess KClO4 started decomposing around 410°C which is much below the decomposition temperature of pure KClO4.

The thermal decomposition of potassium bromate in the presence of chromium(III) oxide

Abstract: Thermal decomposition studies of intimate mixtures of different molar ratios of potassium nitrate and chromium(III) oxide were made by employing thermogravimetry differential thermal analysis, chemical analysis, infrared spectral measurements and X-ray powder diffraction patterns. Potassium nitrate in the presence of chromium(III) oxide starts decomposing around 350°C which is much below the decomposition temperature of pure potassium nitrate. Chromium(III) is completely oxidized into its hexavalent state when the mole ratio of KNO3 to Cr2O3 is greater than three.

Thermal behaviour of morpholinium perchlorate

Abstract: Morpholine is a base of moderate strength, comparable with that of ammonia, and capable of forming -onium-type salts. Extensive studies [1,2] have been made on the thermal stability of ammonium perchlorate because of its technological use as an oxidant in solid state rocket propellants. The preparation, characterization and thermal behaviour of morpholinium perchlorate are reported in this note. The study was followed by XRD, IR, TG, DTA and mass spectral techniques.

The structure and stability of sulfated alumina and titania

Abstract: The oxidation of H2S or SO2 in excess O2 over Al2O3 or TiO2 (anatase) yields, for either catalyst under anhydrous conditions, an infrared spectrum which is characterized by an intense sharp band near 1380 cm−1 and a broad band or doublet near 1040 cm−1. The same spectrum arises from the impregnation of Al2O3 with either (NH4)2SO4 or Al2(SO4)3 · 18H2O or of TiO2 with (NH4)2SO4 or TiOSO4 and heating the dried mixture at 450 °C under vacuum. The sulfated surface does not exchange with 18O2 but does with H218O and only one new shifted high-wavenumber band is produced for partial or complete oxygen-18 exchange. The infrared spectrum changes in the presence of H2O at 20 °C and resembles that of a more traditional bidentate type sulfate species and we postulate that, in the absence of OH groups or water the sulfate has a structure resembling (M3O3)SO [M = Al or Ti], whereas in the presence of H2O or excess surface OH groups this is converted to type groups, thus accounting for the increased Bronsted acidity. Finally, the sulfated Al2O3 surface is more thermally stable and more resistant to reduction in H2 than is the TiO2 surface and the ramifications are discussed in terms of the use of these oxides for SOx transfer catalysts or in air pollution abatement.

Combustion Synthesis of Metal Chromite Powders

Abstract: Fine-particle metal chromites (MCr2O4, where M = Mg, Ca, Mn, Fe, Co, Ni, Cu, and Zn) have been prepared by the combustion of aqueous solutions containing the respective metal nitrate, chromium(III) nitrate, and urea in stoichiometric amounts. The mixtures, when rapidly heated to 350°C, ignite and yield voluminous chromites with surface areas ranging from 5 to 25 m2/g. MgCr2O4, sintered in air at 1500°C for 5 h, has a density of 4.0 g/cm3.

Lattice vibration spectra. LIX. Single crystal infrared and Raman studies of spinel type oxides

Abstract: The infrared reflection and Raman spectra of spinel type oxides M Cr 2 O 4 ( M = Mg, Mn, Fe, Co, Ni, Cu, Zn), M Fe 2 O 4 ( M = Ni, Cu), and Mn 3 O 4 (single crystals, pressed pellets) including Kramers-Kronig analyses and oscillator-fit calculations are presented. The spectra are discussed with respect to the true space group and ionicities of these compounds as well as the vibrational modes, phonon energies, and resonance Raman effects compared with the respective spectra of spinel type halides, sulfides, and selenides. Because of the relatively high porosity of the pellets obtainable the true frequencies of the IR allowed phonons can only be determined from single crystal spectra.

Effect of Transition Metal Oxides on Decomposition and Deflagration of Composite Solid Propellant Systems: A Survey

Abstract: Introduction T metal oxides (TMO) like Fe2O3, CuO, MnO2, CuCr2O4, etc., form a very popular group of catalysts for burning rate modification of composite solid propellants. Although it is well known that these oxides affect the decomposition characteristics of polymers and oxidizers like ammonium perchlorate (AP)' and potassium perchlorate, (KP) the exact mechanism of the effect on solid propellants is by no means clear even today. Much fragmentary literature is available on the effect of these oxides on propellant burning and decomposition, oxidizer burning and decomposition, and sandwich and condensed mixture combustion. It is the purpose of this review to bring the material together so that a comprehensive picture can be drawn of the mechanism of the action of these catalysts. It may be mentioned here that these oxides also catalyze hydrocarbon oxidation reactions by inducing free radical decomposition of hydroperoxides (formed by the contact of oxidizer and hydrocarbon).

Aminophosphines: their chemistry and role as ligands and synthons

Abstract: In recent years, research in organophosphorus chemistry has mainly focused in designing newer and better phosphorus ligands for synthesizing novel metal complexes with improved catalytic activities. Aminophosphines [tricoordinate phosphorus(III)–nitrogen systems] are considered as versatile compounds owing to the presence of nitrogen centres which, in principle, can influence additional reactivity features. They are quite sensitive to air and moisture due to the presence of polar PN bond(s). In spite of this, research in aminophosphine chemistry is gaining momentum day-by-day and this is due mainly to one reason: their rich behaviour as ligands in metal complex chemistry and subsequently in catalysis. Their role as synthons in inorganic heterocyclic chemistry has also helped produce new types of heterocycles. In this paper, the chemistry of simple acyclic aminophosphines (synthesis, characterization, reactivity and applications) is covered and particular focus is given to their ability to form chalcogenides along with their role played as ligands in coordination chemistry and as synthons in inorganic heterocyclic chemistry. Copyright © 2009 John Wiley & Sons, Ltd.