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991.
Davinder Singh Nafa Singh Sunil Dutta Sharma Chander Kant C. P. Sharma R. R. Pandey K. K. Saini 《Journal of Sol-Gel Science and Technology》2011,58(1):269-276
Nickle and iron doped TiO2 thin films were prepared on glass substrates by sol–gel dip coating process. Indirect and direct optical energy gaps were
calculated with the incorporation of different concentrations of both the ions. Indirect bandgap was found to be a strong
function of the dopant concentration, whereas direct energy gap has negligible dependence on the nature of dopant and its
concentration. Direct energy gap has always been found to retain a value higher than the indirect energy gap. Variation of
observed energy gap properties shows a trend similar to that reported on the basis of numerical calculations or the samples
obtained by other techniques. Increase in refractive index and corresponding density of the film sample does not support the
change in turn over frequency. The influence of crystalline phase change is also ruled out by XRD investigations. It is concluded
that red shift of band edge absorption takes place by incorporation of dopant and sol–gel dip coating technique offers an
effective low cost route to the production of these coatings. 相似文献
992.
The dimethyl phenyl phosphine (DMPP) initiated polymerization of methyl methacrylate (MMA) in dimethylsulfoxide was studied. Polymerization of MMA in this system required the presence of transition metal ions like Fe3+ or Cu2+. Kinetic studies showed that the propagation was free radical in nature. An interaction between DMPP and MMA was detected spectrophotometrically. A proposed mechanism involves a transition metal ion-activated dipole interaction between the carbonyl oxygen and the phosphorus atom with the ultimate formation of a methyl methacrylate type of free radical. 相似文献
993.
Four new grid forming hydrazone ligands substituted with methoxy and dimethylamino groups were synthesised. Combination of these ligands with zinc triflate in acetonitrile resulted in self-assembly to form grids as indicated by 1H NMR and ES-MS. 1H NMR also showed thermally induced rotation of the intercalated phenyl ring in both the new grids, and in three previously reported grid compounds. Of these seven, five were amenable to study by variable temperature 1H NMR. Though the observed rates varied by more than an order of magnitude depending upon ligand structure and level of deprotonation, activation energies were similar (~60 kJ/mol) for all complexes studied. This suggests a model in which dissociation of the central pyrimidine ligand precedes phenyl group rotation with an enthalpy of dissociation near zero. The rate of rotation of the phenyl ring increases with an introduction of electron-donating substituents on the phenyl ring, possibly due to an increased repulsion between π systems. 相似文献
994.
995.
Satyaki Dutta 《Advances in Mathematics》2010,224(2):525-538
In this paper, we prove that under a lower bound on the Ricci curvature and an assumption on the asymptotic behavior of the scalar curvature, a complete conformally compact manifold whose conformal boundary is the round sphere has to be the hyperbolic space. It generalizes similar previous results where stronger conditions on the Ricci curvature or restrictions on dimension are imposed. 相似文献
996.
Subhendra Mohanty Varun Sahni S. Chakraborty Ashok Goyal Sukanta Dutta Debajyoti Choudhury Shobhit Mahajan Amitabha Mukherjee Hatem Widyan Urjit Yajnik S. Mohanty J. A. Grifols Uma Mahanta Sarira Sahu Varun Sahni Tarun Souradeep Albert Stebbins Ioav Waga Vikram Soni N. Panchapakesan R. Brandenberger 《Pramana》1998,51(1-2):273-286
The astroparticle physics working group witnessed intense discussion and activity covering a broad range of topics ranging
from supergravity and baryogenesis to compact stars and the large scale structure of the Universe. A summary of some of the
subject areas in which collaborations were initiated during WHEPP-5 is presented below. 相似文献
997.
Clint D. Gamlin Naba K. Dutta Namita Roy Choudhury 《Polymer Degradation and Stability》2003,80(3):525-531
The thermal degradation behavior of a range of ethylene-propylene-diene (EPDM) elastomers, covering the whole range of composition, has been examined under isothermal conditions between 410 and 440 °C using thermogravimetric analysis. The kinetic parameters of degradation for the polymers have been evaluated using different mathematical models based on different proposed mechanisms of degradation. The experimental data were fitted to the models using non-linear regression analysis technique based on Marquardt-Levenberg algorithm. It appears that the degradation of EPDMs follows the Avrami-Erofeev two-dimensional nucleation model or a random chain-scission mechanism. No observable trend was found between the ethylene content of EPDM and the activation energy of degradation. 相似文献
998.
High-energy ball milling of monoclinic ZrO2–30 mol% anatase TiO2 mixture at different durations results in the formation of m-ZrO2–a-TiO2 solid solution from which the nucleation of nanocrystalline cubic (c) ZrO2 polymorphic phase sets in. Post-annealing of 12 h ball-milled sample at different elevated temperatures for 1 h results in almost complete formation of c-ZrO2 phase. Microstructure of the unmilled, all the ball milled and annealed samples has been characterized by Rietveld's X-ray powder structure refinement method. Particle size, rms lattice strain, change in lattice parameters and phase content of individual phases have been estimated from Rietveld analysis, and are utilized to interpret the results. In course of milling, (1 1 1) of cubic lattice became parallel to () plane of monoclinic lattice due to the orientation effect and cubic phase may have been formed on the (0 0 1) of the m-ZrO2–a-TiO2 solid solution lattice. A comparative study of microstructure and phase transformation kinetics of ZrO2–10, 20 and 30 mol% a-TiO2 ball-milled and post-annealed samples reveals that rate of phase transformation m→c-ZrO2 increases with increasing a-TiO2 concentration and 30 mol% of nanocrystalline c-ZrO2 phase can be obtained within 4 h of milling time in the presence of 30 mol% of a-TiO2. The post-annealing treatment at 773, 873 and 973 K for 1 h duration each reveals that rate of c-ZrO2 formation with increasing temperature is retarded with increasing a-TiO2 concentration but the amount of c-ZrO2 becomes almost equal (95 mol%) at 973 K. It suggests that almost fully stabilized nanocrystalline c-ZrO2 can be formed by adding a tetravalent solute to m-ZrO2. 相似文献
999.
1000.
Jun Wang Meng-Wei Dong Dong Liu Lu Lu Xiren Wu Archisman Dutta 《Supramolecular chemistry》2019,31(5):361-368
A 2D coordination polymer [Zn2(betc)(bip)2]·3H2O (1) has been synthesised by deploying mixed ligand strategy . The photoluminescence properties of 1 in different solvents have been investigated and its sensing properties to detect nitroaromatic compounds (NACs) have been explored. 1 displayed selective sensing for 4- nitrotoluene (4-NT) with lower limit of detection (LOD) 0.62 ppm. The probable mechanism for sensing of NACs by 1 ha s been addressed using quantum chemical calculations. Also photocatalytic properties of 1 to photo-decompose model aromatic dyes viz. methyl violet (MV) and 20 rhodamine B (Rh B) have been evaluated. The experiments indicated that 1 displayed better photocatalytic performance in photo-degrading MV than Rh B. The plausible mechanism through which 1 displayed photocatalytic degradation of aromatic dyes had been revealed using density of states (DOS) and partial DOS calculations.
The probable mechanism for the photocatalytic property and emission quenching of 1 has been proposed with the aid of density of states and partial density of states calculations. 相似文献