NISCAIR Online Periodicals Repository Collection: IJC-A Vol.51A(08) [August 2012]

Electrical conductivity of cuprous bromide in the temperature range of 30-490 °C

Title: Electrical conductivity of cuprous bromide in the temperature range of 30-490 °C

Authors: Singh, Kaman; Yadav, B C; Singh, Vimalesh Kumar

Abstract: The electrical conductivity (dc) of solid CuBr has been determined employing the cell configuration Cu/CuBr/Cu over a wide range of temperature (30 – 490 °C) which allowed the phase transformations: -CuBr ↔ β-CuBr and β-CuBr ↔ α-CuBr. With the measured conductivities, activation energy and pre-exponential factors have been evaluated over the studied range of temperature. Transport properties in the respective phases are discussed and compared with those reported in the literature. Though the order of magnitude of observed conductivity is same as that reported in literature, the observed values are higher than those reported earlier. The electrical conductivity of -CuBr increases rapidly with temperature, from 2.51 × 10^-3 Ω^-1m^-1 at 50 °C to 16.08 Ω^-1m^-1at 400 °C. After the first phase transition of -CuBr ↔ β-CuBr, the electrical conductivity attains a value of 148 Ω^-1m^-1 and increases further with increase in temperature. The conductivity increases by about 30 % on β-phase ↔ α-phase transition (maximum value 377.60 Ω^-1m^-1 at 487 °C). Activation energies for conduction of -CuBr are found to be 85.58 kJ mol^-1 (30-225 °C) and 145.35 kJ mol^-1 (320-380 °C) whereas for β-CuBr it is 22.45 kJ mol^-1 and for the superionic α-phase it is 2.38 kJ mol^-1.

Page(s): 1090-1094

Non-ionic surfactant mediated preparation of κ-carrageenan/calcium carbonate biocomposite

Title: Non-ionic surfactant mediated preparation of κ-carrageenan/calcium carbonate biocomposite

Authors: Kumar, Sanjay; Prasad, Kamalesh; Siddhanta, A K

Abstract: Non-ionic surfactants mediated biocomposites of k-carrageenan have been prepared by incorporating CaCO₃ particles generated in situ under microwave heating. The CaCO₃ particles generated in presence of a sugar surfactant (SUC-PEO) has near spherical shape in comparison to that prepared in presence of Brij 35. The products have been characterized for their thermal stability, swellability in aqueous medium, crystallinity and microstructures. Reasonable degree of porosity is introduced in the biocomposites by chelating out CaCO₃ particles using EDTA.

Page(s): 1085-1089

Synthesis of Ti–β zeolite membrane over porous α–alumina tubular support

Title: Synthesis of Ti–β zeolite membrane over porous α–alumina tubular support

Authors: Sasidharan, Manickam; Bhaumik, Asim

Abstract: Three-dimensional large-pore titanosilicate analogue of zeolite Beta membrane has been synthesized for the first time through hydrothermal method over porous α-alumina tubular support. Crack-free continuous intergrown membranes are obtained after four repeated syntheses over the same alumina support but with different synthesis gels. The thickness of the calcined Ti–β membrane is found to be ≈9 ± 2 μm. The calcined composite membranes have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray analysis, UV-visible diffuse reflectance spectroscopy and elemental analysis by inductively coupled plasma studies. The XRD patterns of composite membrane and powder sample collected from the reactor suggest the formation of pure crystalline titanium Beta phase. The UV-visible spectrum confirms the presence of titanium predominantly in the tetrahedral position. The gas permeability of the membranes at room temperature at different inlet pressure is of the order of 10^–8. Prior to calcination, the composite membranes do not show any gas permeability indicating high compactness of the synthesized membrane.

Page(s): 1080-1084

Two step one-electron transfer reaction of chromium(III) complex containing carbidopa and inosine with N-bromosuccinimide

Title: Two step one-electron transfer reaction of chromium(III) complex containing carbidopa and inosine with N-bromosuccinimide

Authors: Abdel-Khalek, Ahmed A; Abdel-Hafeez, Mahmoud M

Abstract: Oxidation of [Cr^III(CD)(Ino)(H₂O)₄]²⁺(where CD = carbidopa, Ino = inosine) with N-bromosuccinimide (NBS) was studied kinetically in aqueous media over varying ranges of concentrations of complex (1.0-5.0) × 10^-4 mol dm^-3and NBS (0.5-5.0) × 10^-2 mol dm^-3,pH,ionic strength and temperature. The reaction is first order with respect to [Cr^III] and [NBS]. The rate of reaction increases with increasing pH over the studied range (6.76-7.84). The anionic surfactant, sodium dodecyl sulphate is found to increase the rate of the oxidation in the range (0.0-1.0) × 10^-3mol dm^-3. Thermodynamic activation parameters have also been calculated. The rate of oxidation obeys the equation d[Cr^VI]/dt = {k₃+ k₂(1/[H⁺])}[NBS][[Cr^III(CD)(Ino)(H₂O)₄]²⁺]. The experimental rate law is consistent with the proposed mechanism in which the protonated and deprotonated species are involved in the rate determing step. It is proposed that a two step one-electron transfer takes place via an inner sphere mechanism.

Page(s): 1073-1079