Dr. K. S. Ojha
@nitrr.ac.in
Assistant Professor
National Institute of Technology Raipur
RESEARCH INTERESTS
Nano-materials and their applications
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
S.M. Saini and K.S. Ojha
Elsevier BV
Abstract Ni doped ZnSe nanospheres in presence of PVA have been synthesized via a cost effective and simple solvothermal method. The structural and rnorphological characterization of as undoped and doped samples have been made using X-ray diffraction (XRD) and FESEM imaging techniques and it reveals the formation of Ni doped ZnSe nanospheres with crystallite size 6 nm. The observed red shift in absorption edge of Ni doped ZnSe as compared to undoped sample also indicates the formation of nanospheres. The PL spectra of Ni doped sample shows red shift with enhanced intensity. The molecular vibrations of PVA capped Ni doped ZnSe nanospheres have been studied and four new vibrational modes have been observed and reported.
K. S. Ojha and A. K. Shrivastav
Springer Science and Business Media LLC
PVA passivated ZnSe nanorods have been synthesized using the solvothermal method. XRD analysis of the synthesized nanorods validates the cubic zinc blende structure with average particle size of 14 nm, and SEM analysis confi rms the formation of rods having a wide range of lengths. A twin nanorod along with a typical nanostructure of rods has been observed in SEM micrographs. The optical characterization of the synthesized nanorods has been made using UV-Vis and photoluminescence spectroscopy. An energy gap of 3.89 eV has been observed, which is blue shifted from the bulk ZnSe. The dielectric study of ZnSe nanorods has been also made and reported.
P. Mishra, K. S. Ojha, and A. Khare
Springer Science and Business Media LLC
Copper-doped zinc sulfide nanoparticles have been synthesized using a wet chemical method. The synthesized nanoparticles exhibit a zinc blende structure with the crystallite size of 3.8 nm. The morphological and optical studies of the synthesized nanoparticles have been performed. It is found that the band gap varies from 3.6 to 4.4 eV depending upon the concentration of copper. The room temperature photoluminescence of the synthesized nanoparticles has been also investigated.
K.S. Ojha
Elsevier BV
Abstract A novel nanostructure of CdSe in presence of CTAB, synthesized via solvothermal process, has been reported. The structural, morphological, optical and dielectric properties of the synthesized CdSe nanostructure have been studied. The synthesized CdSe nanostructure has pure wurtzite structure with average particle diameter of 16 nm and length 160 nm as confirmed by SEM. The band gap of the observed nanostructure is found to be 2.2 eV. The photoluminescence, FTIR and dielectric properties of the prepared nanostructutre have been discussed.
K.S. Ojha
Elsevier BV
Abstract Zinc sulphide (ZnS) nanostructured thin films have been prepared using CBD method on glass substrate at room temperature under three different concentrations of PVA. The structural and optical properties of the films have been studied. The XRD pattern suggests wurtzite structure with lattice constant 5.3876 A and average particle size of 4 nm which is confirmed by TEM micrographs. The bandgap of the synthesized ZnS nanoparticles are found to decrease with increase of PVA concentration. The Raman spectra of ZnS nanoparticles are also reported.
K.S. Ojha and Sadhana Agrawal
Elsevier BV
Abstract Substitution of both isovalent and aliovalent cations for the host ones in perovskite lattice plays a very important role in these modification mechanism. The polycrystalline (Bi 0.5 Na 0.5 )Zr 0.08 Ti 0.92 O 3 (BNZT) ferroelectric thin films were deposited by using CBD method. XRD analysis revealed a rhombohedral perovskite type structure with lattice constants a=b=c=3.790 A and α=89.65°. The morphological and dielectric studies have been also made.
Sadhana Agrawal, K.S. Ojha, and Dilip Sahu
Elsevier BV
Microcellular silicone rubber nanocomposites, filled with 2 phr multi-walled carbon nanotubes (MWCNTs), were prepared by a two roll mixing mill with different blowing agent concentrations. The distribution of the conductive nanoparticles has been investigated with scanning electron microscopy (SEM). The FTIR spectra of nanocomposites have been studied in the range of 500-4000 cm-1 and their corresponding peaks have been assigned. The effect of MWCNT on dielectric properties of microcellular silicone elestomer nanocomposites were studied in the frequency range of 100 Hz–5 MHz to understand the electrical conduction mechanism.
K. S. Ojha
Informa UK Limited
Lead-free ferroelectric oxide materials have attracted considerable attention from the environmental viewpoint. Among lead-free piezoelectric materials, bismuth sodium titanate (Bi0:5Na0:5TiO3) is considered to be one of the excellent candidates. The crystal structures, phase transitions and physical properties of BNT in bulk have been widely investigated. However, BNT in thin film form has been rarely reported. In the present work, bismuth sodium titanate (Bi0.5Na0.5TiO3) thin films, synthesized by spin coating technique on alumina substrates, are annealed at different temperature from 100°C to 500°C to optimize the crystal structure. The structurally optimized BNT thin film is observed at 400°C which is confirmed by X-ray diffraction patterns and FWHM calculation of (012) peak. The crystallinity of BNT thin films increases with the increase of annealing temperature and exhibits a single phase of perovskite structure at annealing temperature of 400°C which is also confirmed by scanning electron micrographs. The dielelectric constant also increases with increase of annealing temperature and becomes maximum at 400°C while dielectric loss decreases with increase of annealing temperature and becomes minimum at annealing temperature 400°C which also confirms that the film deposited at 400°C is optimized.
K.S. Ojha and R. Gopal
Elsevier BV
Emission spectra of SiN radical are recorded in the region of 505-720 nm using laser ablation technique and the total 62 bands are observed. Out of total 62 bands, 44 bands are observed for the first time while the rest 18 bands are reported by earlier workers. The total 53 bands are analyzed into two new quartret-quartret band systems f(4)Σ(-)-d(4)Σ(-), g(4)Π-d(4)Σ(-) while the rest nine bands are analyzed into previously reported B(2)Σ(+)-X(2)Σ(+) system. The vibrational constants of these states are determined and reported.
K. S. Ojha, K. N. Singh, P. K. Bajpai, P. K. Bajpai, K. S. Ojha, and K. N. Singh
AIP
Sodium Bismuth Titanate (Na0.5Bi0.5TiO3) ceramics prepared using a high‐temperature solid‐state reaction method stabilizes in single phases with an ABO3 perovskite structure. Frequency and temperature dependence of the dielectric response and impedance relaxation were investigated. Broad dielectric constant peaks are observed over a wide temperature range with diffuse phase transition character. The complex impedance plot exhibited one impedance semicircle identified over the frequency range of 1 KHz–1 MHz, explained by the grain effect of the bulk. The centers of the impedance semicircles lie below the real axis, which indicates that the impedance response is a Cole‐Cole‐type relaxation. The dc conductivity of BNT ceramic has been reported. The apparent activation energy of the conduction process has been also discussed.
K. S. Ojha and R. Gopal
Informa UK Limited
ABSTRACT Laser-produced spectra of SiC molecule in region 370–590 nm were reinvestigated using laser ablation technique. Out of 117 bands of SiC molecule observed in this region, 108 bands were new, while the other nine bands of SiC molecule were reported previously. All these 117 bands of SiC molecule were assigned to three new transitions C1-X, C2-X, and C1-A and to one previously reported C3Π-X3Π transition. The molecular constants of C1, C2, C3Π, A3Σ−, and X3Π states were calculated and reported.
K.S. Ojha and R. Gopal
Elsevier BV
The laser produced spectrum of Si(2) molecule is recorded for the first time using laser ablation technique in the region of 540-1010 nm. About 110 bands are observed in the entire spectral region and all these bands are classified into three band systems, viz. E-X, F-X and G-X of Si(2) molecule lying in the region of 814-1010 nm, 630-900 nm and 546-710 nm, respectively. All these electronic transitions take place from ground state X(3)Sigma(g)(-) state. The molecular constants of all these states have been determined.
Subhash C Singh, K S Ojha, and R Gopal
Springer Science and Business Media LLC
Laser-induced breakdown spectrum has been recorded in the region of 380–455 nm using second harmonics of Nd:YAG laser, computer-controlled TRIAX 320 M monochromator with a reciprocal linear dispersion 2.64 nm/mm fitted with ICCD detector. The spectrum consists of 108 bands, which are classified into four new subsystems E0u+ (1Σu+) → A1g(3Πg), J0g±\\1g(3Σg+) → D1u(1Πu), F1u → A0g±(3Πg) and F1u → A2g(3Πg) along with additional bands of the known system E0u+(1Σu+) → A0g±(3Πg). The molecular constants for these systems have also been determined.