NOPR Collection:

Bond order conservation model studies of H₂ , O₂ and CO dissociation on metallic nanostructures

2017-02-07T09:42:34Z

Title: Bond order conservation model studies of H₂ , O₂ and CO dissociation on metallic nanostructures Authors: Khanra, Badal C Abstract: The bond order conservation - Morse potential (BOC - MP) model has been used to study the dissociation of H₂, O₂ and CO molecules on Ag, Cu, Ni, Pd and Pt nanostructures. For particles with total number of atoms (N_T) upto 500, a moderate increase in the chemisorption energy with particle size has been found in qualitative agreement with the experimental results. For N_T in the range of 40 to 200, the activation for dissociation, DE drops exponentially; and for N_T > 400, DE decreases very slowly. DE for O₂ dissociation on Cu and Ni is found to change sign from positive to negative at N_T between 80 and 140; while DE for O₂ dissociation on Ag, Pt and Pd remains positive for all sizes of the nanostructures. Page(s): 585-589

EPR studies on local structure of 70V₂O₅-30P₂O₅ glass at 4K

2017-02-07T09:38:48Z

Title: EPR studies on local structure of 70V₂O₅-30P₂O₅ glass at 4K Authors: Das, B B Abstract: From the obtained spin-Hamiltonian parameters of the axially symmetric lineshape of the glass at 4K it is concluded that the paramagnetic site in the glass is vanadyl ion, VO²⁺. The vanadium is in distorted octahedral environment of six oxygens forming a O- VO₄..O unit. This geometry of C_4v symmetry leads to the value of the coefficient of 3d_xy orbital β as 0.96 and the Fermi contact term the measure of the vanadium 4sorbital contribution to bonding as 0.75. The crystal field splitting energy, tetragonal distortion energy and spin-orbit coupling constant are found to be 23186, 12056 and 169 cm^-1, respectively. From the above values, it is concluded that O- VO₄_•••O unit has highly 'squeezed' VO₄ group with moderate axial compression. The vanadium 3d¹ small polaron gets localized on a ⁵¹V(I= 7/2)site at 4s due to the 'Anderson localization' and thereby the symmetry of the local structure of the glass is reflected in its EPR lineshape. Page(s): 590-593

Thbrmodynamics of molecular interactions in some water + nonelectrolyte

2017-02-07T09:32:31Z

Title: Thbrmodynamics of molecular interactions in some water + nonelectrolyte Authors: Sharma, V K; Yadav, O P; Singh, Jaibir Abstract: Molar excess volumes, V^E, and molar excess enthalpies, H^E, for the various water(i)+pyridine or + α- or + β- or + γ-picoline(j) mixtures have been determined as a function of composition at 298.15 and 308.15 K. The observed data have been analysed by graph theoretical approach which suggest that while water exists as il mixture of dimer and trimer pyridine or α- or β- or γ-picolines exists as a dimer or an equilibrium mixture of monomer and dimer in pure state. Further these mixtures are charaeterised predominantly by the presence of 1:1 molecular complex. Page(s): 594-601

Effect of temperature on the rates of aqueous polymerization of vinyl acetate initiated by SO free radIcals produced from potassIum persulphate and the redox reaction of ferrous ammonium sulphate and potassium persulphate

2017-02-07T09:14:45Z

Title: Effect of temperature on the rates of aqueous polymerization of vinyl acetate initiated by SO free radIcals produced from potassIum persulphate and the redox reaction of ferrous ammonium sulphate and potassium persulphate Authors: Mitra, Subhash C; De, Niharendu; Guchhait, Sukumar; Konar, Ranajit S Abstract: The aqueous polymerization of vinyl acetate (VA) initiated by the redox system, ferrous ammonium sulphate (FAS) and potassium persulphate (KPS) has been studied over a wide range of temperature, 5 , to 65°C. It is noted that the separating polymer phase is a stable colloid, milky white at or below 10°C, but yellow at temperatures above 20°C. It is deep yellow above 50°C, but very faint yellow between 10 to 20°C. The colloidal stability (CS) of the latex solutions first decreases slightly and remains approximately constant between 20 to 40°C, and follows an increasing trend again above 40°C. The rates of polymerizations have been found to be maximum at (25 ± 2)°C, above or below which the rates decrease. The purified polymer, polyvinyl acetate (PVA),is found to contain iron and it is found to be insoluble in common solvents of PYA. Arrhenius plot for the activation energy (E_a) of the aqueous polymerization of VA in the system, FAS-VA-KPS, over the temperature range 5 to 65°C, is a curved line. (E_a) is about (+) 10.0 kJ/mol between 5 to 20°C, and about (-) 45.97 kJ/mol between 40 to 65°C. In the KPS-VA system, the initial rates of polymerization are found to increase with temperature (50 to 65°C), but the (CS) decreases with temperature. The latex solutions are always white and do not change colour with temperature.PVA is soluble in common solvents. E_a for the formation of PVA in the KPS-VA system is (+) 108.18 kJ/mol. Page(s): 602-610

NOPR Collection:

Bond order conservation model studies of H2 , O2 and CO dissociation on metallic nanostructures

EPR studies on local structure of 70V2O5-30P2O5 glass at 4K

Thbrmodynamics of molecular interactions in some water + nonelectrolyte

Effect of temperature on the rates of aqueous polymerization of vinyl acetate initiated by SO free radIcals produced from potassIum persulphate and the redox reaction of ferrous ammonium sulphate and potassium persulphate

Bond order conservation model studies of H₂ , O₂ and CO dissociation on metallic nanostructures

EPR studies on local structure of 70V₂O₅-30P₂O₅ glass at 4K