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Titābar, India

Buragohain P.,CSIR - Central Electrochemical Research Institute | Saikia P.P.,CSIR - Central Electrochemical Research Institute | Saikia P.P.,NNS College | Barua N.C.,CSIR - Central Electrochemical Research Institute
Tetrahedron Letters

Triphenylphosphine dibromide (TPPDB) has been found to be a very effective catalyst for the one pot three-component Mannich reactions of aryl aldehyde, acetophenone, and benzyl carbamate under solvent-free condition at room temperature. The advantageous features of this methodology are operational simplicity, shorter reaction time, cost-effectiveness, and excellent yields. The catalyst possesses distinct advantages over other catalysts used for this conversion. © 2013 Published by Elsevier Ltd. Source

The effects of variable viscosity and thermal conductivity on free convective oscillatory flow of a viscous incompressible and electrically conducting fluid past a vertical plate in slip flow regime with periodic plate temperature when suction velocity oscillates in time about a constant mean is discussed. The fluid viscosity and thermal conductivity are assumed to be inverse linear functions of temperature. The problem is governed by acoupled non-linear system of partial differential equations. Explicit finite difference method is employed to solve the equations. The effects of viscosity variation parameter, thermal conductivity variation parameter, magnetic parameter on the velocity distribution dna temperature distribution for Pr∞=0.7 fluid and for rarefaction parameter h=0 and h=0.4 are discussed and shown graphically. Also the effects of these parameters on the skin friction coefficient and on the rate of heat transfer are calculated. Source

Baruah M.K.,NNS College | Saikia P.P.,Darang College | Paul T.,Darang College | Barua M.,DCB Girls College
Journal of Materials and Environmental Science

Structural changes of char prepared by thermal treatment of Assam coal in absence and presence of mixed metal oxide nanoparticles (cobalt ferrite) have been studied here. Thermogravimetric (TG) analyses were carried out in nitrogen atmosphere up to 250°C at a heating rate of 5°C per minute. TG studies for the raw coal sample shows no weight change in the temperature range 110-245°C suggesting phase transition with the formation of a softening state while there appeared minor weight gain in this temperature range for the mixed metal oxide nanoparticles blended coal sample. The effect of nanoparticles in the thermal treatment of coal is apparent and thus restricting the devolatilization to certain extent, due to the increase of thermally stable components. The chars prepared from these samples at 250°C in inert atmosphere, have been used to compare the changes of structure in the absence and presence of nanoparticles by using FTIR studies. Modification of structure of the raw coal char by the formation of oxygen containing species and increase of aromaticity in the char of the blended coal sample has been reported here. It appears that the presence of mixed metal oxide nanoparticles has been playing a dominant role in the structural changes of coal during thermal treatment in inert atmosphere. This work has some considerable technological interest. Source

Borah D.,DCB Girls College | Baruah M.K.,NNS College | Saikia P.P.,NNS College | Senapoty K.K.,Indian Institute of Technology Guwahati | And 2 more authors.
Journal of Materials and Environmental Science

In this paper, ZnO nanoflower was successfully obtained by precipitation method using zinc nitrate and sodium hydroxide at pH 11.5. The aggregate sturucture evolutions were characterized by XRD, SEM, and FESEM while the elemental composition of the materials was determined by EDX. The petals of the nanoflower are of varying sizes. The crystalline size of the nanoparticles is in the range 39.5-53.1 nm and the calculated surface area has been found to be 27.1 g/m2. Infrared study reveals that the nano crystals are not homogeneous and the chemical structural environment has shown hydroxide layer attached on the surface of the ZnO nanoparticles. This work has provided some knowledge on the structural and surface properties of ZnO nanomaterials. Source

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