Ravi Kumar
Articles written in Bulletin of Materials Science
Volume 14 Issue 3 June 1991 pp 545-549 International Conference On Superconductivity—II
Characteristics of laser-induced plasma from high
G Padmaja A V Ravi Kumar V Vidyalal P Radhakrishnan V P N Nampoori C P G Vallabhan
The spectroscopic analysis of the emission from the plasma produced by irradiating a high
Volume 20 Issue 5 August 1997 pp 667-675
Elastic properties of ZnF2-PbO-TeO2 glasses doped with certain rare earth ions
The elastic moduli (
Volume 21 Issue 4 August 1998 pp 341-347 Electrical Properties
Dielectric properties of LiF-B2O3 glasses doped with certain rare earth ions
A V Ravi Kumar B Apparao N Veeraiah
Dielectric constant
Volume 22 Issue 3 May 1999 pp 251-255 High Tc Superconductors: Thin Films And Vortex Pinning
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S K Arora Ravi Kumar D Kanjilal G K Mehta S Khatua R Pinto Vijay Kumar A K Gupta
Effect of 250 MeV107Ag ion irradiation induced columnar defects on the noise properties of the YBCO superconductor in the normal and superconducting state have been investigated. Magnitude of the spectral density of the noise is found to scale inversely with the frequency and exhibit a quadratic dependence on the bias current confirming that the noise arises due to the resistance fluctuations. The magnitude of
Volume 22 Issue 5 August 1999 pp 905-915 Polymers
Chitin and chitosan fibres: A review
Chitin is the most abundant natural amino polysaccharide and estimated to be produced annually almost as much as cellulose. It has become of great interest not only as an underutilized resource, but also as a new functional material of high potential in various fields and the recent progress in chitin chemistry is quite noteworthy. The purpose of this review is to take a closer look at fibres made of chitin and its derivatives. Based on the current research and existing products, some new and futuristic approaches, in the development of novel fibres and their applications have been thoroughly discussed.
Volume 34 Issue 4 July 2011 pp 683-687
Thermoluminescence properties of 𝛾-irradiated Bi doped BaS nanostructures
Surender Singh Ankush Vij S P Lochab Ravi Kumar Nafa Singh
Bismuth doped barium sulphide nanocrystallities were prepared and characterized by XRD. Thermoluminescence (TL) studies of these samples after exposure to gamma radiation were carried out. The TL glow curve of the phosphors have two peaks at 403 K and 658 K while in their bulk counterparts these peaks were reported at 486 K and 570 K (Rao 1986). We noted that TL intensity increases with gamma exposure time in the range 30 min – 41 h which may be explained on the basis of track interaction model (TIM) and a high surface to volume ratio for the nanostructures. The kinetic parameters at various heating rates namely activation energy (E), order of kinetics (b) and frequency factor (s) of BaS : Bi (0.4 mol%) sample was determined using Chen’s method. The deconvolution of curve was done using the GCD function suggested by Kitis. The effect of different heating rates and different amount of dose has also been discussed.
Volume 35 Issue 2 April 2012 pp 253-258
Balwinder Kaur Monita Bhat F Licci Ravi Kumar K K Bamzai P N Kotru
High-resolution X-ray diffraction technique, employing a three-crystal monochromator–collimator combination is used to study the irradiation induced defects in flux grown Sr-hexaferrite crystals irradiated with 50 MeV Li3+ ion beams at room temperature with a fluence value of 1 × 1014 ions/cm2. The diffraction curves of the irradiated crystals suggest the possibility of creation of low angle grain boundaries and other point/clusters of defects causing amorphization in the irradiated crystals. The perfection of the irradiated and unirradiated (0001) cleaved surfaces of the crystals is studied using the bulk method of X-ray topography. The topographs supplement the findings suggestive of modifications in the crystalline quality of SrFe12O19 on irradiation with SHI of Li3+. Etching of the (0001) cleaved surfaces in H3PO4 at 120°C suggests that the dissolution characteristics of the surfaces get affected on irradiation with SHI of Li3+, besides supporting the findings of HRXRD and X-ray topography regarding modifications in the perfection of SrFe12O19 on irradiation.
Volume 42 Issue 5 October 2019 Article ID 0214
A series of glass composites [(Sb₂O₃)0.05(SiO₂)0.65]–[(PbO)(0.3−x):(Cr₂O₃)x ](0 ≤ x ≤ 0.01 mol%) were synthesized. Elastic, thermoluminescence, direct current (dc) conductivity and dielectric characteristics of these glass com-posite materials were studied. The investigations on these glass composites have indicated that the chromium ions exhibit two different oxidation states, such as Cr³⁺ and Cr⁶⁺. The variation in poison ratio (σ ) with micro-hardness (H) plots suggests that the glass composites were prepared with a strongly and covalently connected internal structure. The observed thermoluminescence output increased with an increase in the dose of UV-irradiation. The observed peak positions of these thermoluminescent curves were shifted towards higher temperature regions. The enhanced thermoluminescence output results even recommended that both e− and h+ trap cantres were created at the deeper trap levels and contribute to thermolu-minescence emissions at higher temperatures. The dc conductivity (σ_{dc}) and activation energy evaluations are also observed. Dielectric parameters such as density of energy states $N$($E$_{f} ), temperature region of relaxation and loss tangent (tan δ)were calculated. The linear relationship between variation in alternating current conductivity (σ_{ac}) and activation energy suggests that good amounts of polaron hopping with an increase in Cr₂O₃ concentration in these materials were observed. The grades of loss tangent and the number of energy states near the Fermi level suggest that the materials prepared are highly useful in dielectrics.
Volume 43 All articles Published: 12 February 2020 Article ID 0071
The glasses of the composition 25CaO–10(M$_2$O$_3$)–14P$_2$O$_5$–50B$_2$O$_3$:1Er$_2$O$_3$ (where M$=$Bi/Sb/Y) are prepared. The prepared samples are characterized by XRD, thermoluminescence (TL),UVand photoluminescence (PL) techniques. TL reports suggest that the sample of 10 mol%Y2O3 concentration (EY) exhibiting good shape symmetry factor ($u = 0.484$) and low AEs ($E_{\tau} = 1.189$, $E_{\delta} = 1.218$ and $E_{\omega} = 1.210$) under $\gamma$-irradiation might be a good TL asset. The optical absorptions of present glasses are studied well through the Judd–Ofelt theory.The evaluations such as Judd–Ofelt parameters are additionallyprojected. They are found to be the best ($\Omega_2 = 1.62 \times 10^{−21}$ cm$^2$, $\Omega_4 = 1.56 \times 10^{−21}$ cm$^2$ and $\Omega_6 = 0.59 \times 10^{−21}$ cm$^2$) for the sample of 10 mol% Y$_2$O$_3$ concentration (E$_{\rm Y}$), which may be a good optical asset to develop a novel class of laser resources. The radiative evolutions corresponding to the emissive transition ${}^4$S$_{3/2}$ $\to$ ${}^4$I$_{15/2}$ are assessed by PL technique. The evaluations are found to be the best ($A_t = 7089$ s$^{−1}$, $\tau_{\rm rad} = 140$ $\mu$s and $\beta = 96.1$%) for the sample of 10 mol% Y$_2$O$_3$concentration (E$_{\rm Y}$), which may be a useful luminescent resource.
Volume 43 All articles Published: 29 July 2020 Article ID 0173
Evaporation-driven self-assembly in the mixtures of micro and nanoparticles
RAVI KUMAR PUJALA DEVIKA VENKUZHY SUDHAKARAN SURAJIT DHARA
We report experimental studies on the self-assembly of silica microspheres and Laponite nanoplatelets (NPs) in evaporating sessile droplets and in thin films, respectively. A ring-like stain of the silica microspheres with positionalorder is observed after the evaporation of sessile droplets due to the coffee-ring effect. This effect is suppressed in the binary mixtures of silica microspheres and Laponite NPs. A depletion zone has been observed in the mixtures during the sessile droplet evaporation, the width of which can be tuned by varying the compositions. We demonstrate a simple method for preparing core–shell particles by evaporating thin films of binary mixtures in which the Laponite NPs self-assemble to form a crystalline shell on the amorphous silica microspheres.We present a possible orientation of the Laponite NPs in the shell.
Volume 45, 2022
All articles
Continuous Article Publishing mode
Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020
Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
Physical Sciences 2020
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