Nitin Kumar; Vinay Kumar; Jitendra Sharma
Abstract
The relaxation behavior of gelatin aqueous solutions has been investigated by time resolved dynamic light scattering (TRDLS) measurements at different temperatures spanning the entire sol to gel phase transition behavior of the system (i.e. from 5 min to 1440 min after a sudden quench from high temperature ...
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The relaxation behavior of gelatin aqueous solutions has been investigated by time resolved dynamic light scattering (TRDLS) measurements at different temperatures spanning the entire sol to gel phase transition behavior of the system (i.e. from 5 min to 1440 min after a sudden quench from high temperature sol to low temperature gel state), when the chosen gelatin concentration in water was maintained at 5 % (w/v), well over the overlap threshold. The quantity of interest, structure factor S (q,τ), has been obtained from the experimentally measured autocorrelation function, g2(τ), allowing appropriate heterodyne contribution. The nonlinear regression analysis of the obtained scattering profiles (variation of structure factor vs. delay time) exhibited good fits to the function S(q,τ) ~A exp(-Dq 2 τ) + B exp(-(τ/τc) β ), up tosystem evolution time of 360 min, whereas the data obtained after 360 min showed appropriate fits to S(q,τ) ~A exp(-Dq 2 τ)+ Cτ -α + B exp(-(τ/τc) β ). The temporal behavior of different fit parameters defining the transient structural network formed in the system has been quantified and analyzed under the purview of well-defined theories. Furthermore, the evolution of particle dynamics from fast to slow and then to almost frozen behavior has been explored through the continuous evaluation of ‘Gelation factor (κ)’ at different stages of system evolution times during the measurements.
Vinay Kumar; Jitendra Sharma; O.M. Ntwaeaborwa; H.C. Swart
Abstract
In this letter, the thermoluminescence response and surface properties of Sr3B2O6:Dy 3+ nanophosphor prepared by combustion method exposed to γ–rays are reported. The crystalline structure of nanophosphors was confirmed by X-ray powder diffraction. The result indicates rhombohedral nanocrystalline ...
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In this letter, the thermoluminescence response and surface properties of Sr3B2O6:Dy 3+ nanophosphor prepared by combustion method exposed to γ–rays are reported. The crystalline structure of nanophosphors was confirmed by X-ray powder diffraction. The result indicates rhombohedral nanocrystalline structure with an average grain size of 41 nm. The microstructure and morphology were studied by transmission electron microscopy, which show nanowire like structure with an average diameter of 42 nm. The samples were irradiated with a γ-dose using 60Co source in the range of 100 Gy - 5000 Gy. The kinetic parameter such as activation energy (E), order of kinetics (b), and frequency factor (s) of the main glow peaks of the Sr3B2O6:Dy 3+ sample at 5000 Gy and different heating rates were determined using both the TLAnal program and Chen’s method. The effect of different heating rate at a fixed dose is discussed. X-ray photoelectron spectroscopy was used to study the surface chemical composition and the electronic states.