Vinay Kumar; Pranjala Tiwari; Lucky Krishnia; Reetu Kumari; Anshika Singh; Arnab Ghosh; Pawan K. Tyagi
Abstract
Silica, generally known as silicon dioxide is insulating in nature whereas silicon is semiconducting. These two materials are widely used in sensing and electronic devices. In order to full-fill demand of silicon, sources other than sand, have to explore for silicon extraction. In this report, bamboo ...
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Silica, generally known as silicon dioxide is insulating in nature whereas silicon is semiconducting. These two materials are widely used in sensing and electronic devices. In order to full-fill demand of silicon, sources other than sand, have to explore for silicon extraction. In this report, bamboo culms have been subjected to thermo chemical decomposition at high temperature (1250 °C) in an inert atmosphere. After pyrolysis, contents in residual of bamboo culms have been characterized by using scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Nanosized, pure crystalline Si has been formed. Si as well as charcoal is found to be crystalline in nature. No silicon carbide formation observed.
Reetu Kumari; Anshika Singh; Rajesh Kumar; Lucky Krishnia; Vinay Kumar; Nitin K. Puri; Pawan K. Tyagi
Abstract
In this report, we have illustrated the synthesis of the Ni-filled multiwalled carbon nanotubes (MWCNTs) on both metallic and non-metallic substrates, by using thermal CVD technique. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) have been used to characterize the surface morphology and ...
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In this report, we have illustrated the synthesis of the Ni-filled multiwalled carbon nanotubes (MWCNTs) on both metallic and non-metallic substrates, by using thermal CVD technique. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) have been used to characterize the surface morphology and crystalline nature of the MWCNTs encapsulated with Ni nanorod. These filled MWCNTs have exhibited strong magnetic response due to encapsulation of pure phase of Ni. Magnetic Force Microscopy (MFM) study of such filled tubes reveals the pole formation in the Ni nanorod and confirms magnetization direction perpendicular to tube axis. Filling occurs in a fragmented manner confirmed by MFM and each fragment found to have north and south poles along the axis perpendicular to the tube i.e. radial direction of tube.
Lucky Krishnia; Reetu Kumari; Vinay Kumar; Anshika Singh; Preeti Garg; Brajesh S. Yadav; Pawan K. Tyagi
Abstract
Filled or un-filled multiwalled carbon nanotubes (CNTs) used in this study have been synthesized by the floating catalyst method and fixed catalyst method, respectively. The thermal stability of filled/un-filled carbon nanotubes has been investigated by using Thermogravimetric analysis (TGA) and Derivative ...
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Filled or un-filled multiwalled carbon nanotubes (CNTs) used in this study have been synthesized by the floating catalyst method and fixed catalyst method, respectively. The thermal stability of filled/un-filled carbon nanotubes has been investigated by using Thermogravimetric analysis (TGA) and Derivative thermogravimetric (DTG) analysis. In this report, we have developed a methodology to distinguish between filled and un-filled carbon nanotubes. Filled-CNTs are found to be more resistant to oxidation than the un-filled carbon nanotubes. The calculated activation energy of as-grown filled CNTs, by using differential method, determined to be 3.29 ± 0.04 eV, which is higher than that of highly ordered pyrolytic graphite (HOPG). Carboneous impurities; amorphous carbon, catalyst and CNT of different diameter, which are structurally different, are identified by their reactivity and the resistance to oxidation.
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.
