Papers by Author: B.K. Singh

Abstract: Multiwalled carbon nanotubes (MWNTs) were fabricated by thermal chemical vapor deposition (CVD) using monometallic and bimetallic Co and Ni on MgO as the catalyst. The mixture of H2/C2H2 gas was used as carbon source. The prepared CNTs have different sizes/shapes and morphologies with minimal formation of carbon particles. The maximum yield of CNTs was obtained with 50% Co catalyst at 600 oC. The morphology of the CNTs with 50% Co loading generates curved structure while 50% Ni results in the formation of linear structure with aligned graphene walls. Intensity ratio of D and G-peaks (ID/IG) was measured from Raman spectra. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) was done for the structural analysis of the prepared MWNTs.

Abstract: CaAl2O4:Eu2+ with high brightness and long persistent luminescence were prepared by solid state reaction method. The phosphor compositions with varying Eu2+ were investigated by powder X-ray diffractometer (XRD), SEM, TEM, photoluminescence excitation and emission spectra. Broad band UV excited luminescence of the CaAl2O4:Eu2+ was observed in the blue region (λmax = 440 nm) due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ ion. The particle size also plays a role deciding the luminescence characteristics of these phosphors. The decay time of the persistence indicated that the persistent luminescence phosphor has bright phosphorescence and maintains a long duration.

Abstract: Carbon nanofibers (CNFs) with different compositions (MgONixCoy, x and y= 0.0 to 0.5) and morphologies were synthesized by the CVD method using H2/C2H2 gas over a bimetallic MgO supported catalyst. The techniques such as Raman spectroscopy, SEM and TEM were used to characterize the as-synthesized nanofibers. The maximum yield for the longest of CNFs having widest diameter was obtained with MgONi0.0Co0.5 catalyst at 600°C, while bi-metallic composition MgONi0.25Co0.25 produced CNFs with good crystalline features. The nanostructure of the CNFs with MgONi0.5Co0.0 generates onion/flake like structure.