arXiv subjects

B. Das

Publications and source records attributed to B. Das.

32 records · Page 2Linked to original sources

arXiv2018

Non-linear Thermoelastic Analysis of an Anisotropic Rectangular Plate

Three-dimensional thermoelastic analysis in presence of electro magnetic field is investigated of a rectangular plate. In the context of Green-Naghdi model-II, fractional order energy equation is adopted for a rotating anisotropic rectangular plate which is subjected to simply supported and isothermal on its four lateral edges. Normal mode analysis is adopted to the governing equations to formulate a Vector-matrix differential equation. The analytical closed form solution of the Vector-matrix differential equation is obtained for the physical parameters using eigen value approach methodology. Numerical results are represented graphically with a sinusoidal spatial variations of the stress applied on the top surface of the plate.

physics.class-ph↗

arXiv2017

Room temperature ferromagnetism in transparent and conducting Mn-doped $SnO_{2}$ thin films

The magnetization as a function of magnetic field showed hysteretic behavior at room temperature. According to the temperature dependence of the magnetization, the Curie temperature $(T_{C})$ is higher than 350 K. Ferromagnetic Mn-doped tin oxide thin films exhibited low electrical resistivity and high optical transmittance in the visible region (400-800 nm). The coexistence of ferromagnetism, high visible transparency and high electrical conductivity in the Mn-doped $SnO_{2}$ films is expected to be a desirable trait for spintronics devices.

cond-mat.mtrl-sci↗

arXiv2017

Evidence of the Antimagnetic rotation in an odd-odd nucleus: The case of 142Eu

The present work reported a conclusive evidence for anti-magnetic rotational (AMR) band in an odd-odd nucleus 142Eu. Parity of the states of a quadrupole sequence in 142Eu was firmly identified from polarization measurements using the Indian National Gamma Array and lifetimes of some of the states in the same structure were measured using the Doppler shift attenuation method. The decreasing trends of the deduced quadrupole transition strength B(E2) with spin, along with increasing J(2) / B(E2) values conclusively established the origin of these states as arising from Antimagnetic rotation. The results were well reproduced by numerical calculations within the framework of a semi-classical geometric model.

nucl-ex↗

arXiv2017

Solution of generalized magnetothermoelastic problem by using finite difference method

A magnetothermoelastic problem is considered for a nonhomogeneous, isotropic rotating hollow cylinder in the context of three theories of generalized formulations, the classical dynamical coupled (C-D) theory, the Lord and Shulman's (L-S) theory with one relaxation time parameter as well as the Green and Lindsay's (G-L) theory with two relaxation time parameters. The inner surface of the cylinder is subjected to a time dependent exponential thermal shock at its inner boundary. The inner and outer surfaces of the hollow cylinder are assumed to be traction free and the temperature gradient vanishes at its outer surface. The problem is solved numerically using finite difference method by developing Crank-Nicolson implicit scheme. The numerical computations of the displacement component, temperature distribution, radial and hoop stresses have been estimated. A comparison has been made under the effect of different parameters by representing several figures.

physics.class-ph↗

arXiv2017

Generalized Magnetothermoelastic Interaction for a Rotating Half Space

A generalized magnetothermoelasticity, in the context of Lord-Shulman theory, is employed to investigate the interaction of a homogeneous and isotropic perfect conducting half space with rotation. The Laplace transform for time variable is used to formulate a vector-matrix differential equation which is then solved by eigenvalue method. The continuous solution of displacement component while the discontinuous solutions of stress components, temperature distribution, induced magnetic and electric field have been analyzed in an approximate manner using assymptotic expansion for small time. The graphical representations also prove this continuity and discontinuity of the solutions.

physics.class-ph↗

arXiv2016

Swift Heavy Ion Irradiation Induced Modifications in Structural, Microstructural, Electrical and Magnetic Properties of Mn Doped $SnO_{2}$ Thin Films

In this paper, we have presented the impact of swift heavy ion beam irradiation on the structural, microstructural, electrical and magnetic properties of $Sn_{0.9}Mn_{0.1}O_{2}$ thin films. The structural and electrical results have been interpreted by using properties of native or point defects, whereas the magnetic and morphological variations have been explained in terms of conductivity of material. Efforts have been made to summarize the properties of all possible charged and neutral point defects ($V_{Sn}^{4-}$, $Sn_{i}^{4+}$, $V_{O}^{0}$, $O_{i}^{2-}$, $Sn_{O}^{4+}$, $O_{Sn}^{2-}$, $H_{O}^{+}$) and afterwards from the correlation between experimentally-observed and theoretically-calculated results various interesting conclusions have been drawn.

cond-mat.mtrl-sci↗

arXiv2016

Role of Carrier Concentration in Swift Heavy Ion Irradiation Induced Surface Modifications

Highly conducting $SnO_{2}$ thin films were prepared by chemical spray pyrolysis technique. One set of as-deposited films were annealed in air for 2 h at 850$^{o}$C. These as-deposited and annealed films were irradiated using $Au^{9+}$ ions with energy of 120 MeV at different fluences ranging from $1\times10^{11}$ to $3\times10^{13}$ $ions/cm^{2}$. Electrical measurement shows that as-deposited $SnO_{2}$ films are in conducting state with n = $3.164 \times 10^{20}$ $cm^{-3}$ and annealed $SnO_{2}$ films are in insulating state. The amorphized latent tracks are created only above a certain threshold value of $S_{e}$, which directly depends on the free electron concentration (n). The electronic energy loss ($S_{e}$) of 120 MeV $Au^{9+}$ ions in $SnO_{2}$ is greater than the threshold energy loss ($S_{eth}$) required for the latent track formation in annealed $SnO_{2}$ thin film, but is less than $S_{eth}$ required for as-deposited $SnO_{2}$ film. Therefore, the latent tracks are formed in the annealed $SnO_{2}$ film and not in the as-deposited $SnO_{2}$ film. Thermal spike model is used for the calculation of threshold energy loss and radius of melted zone. The possible mechanism of the structural changes and surface microstructure evolutions is briefly discussed in the light of ion's energy relaxation processes and target's conductivity. The atomic force microscopy (AFM) study of films shows that the morphologies of irradiated films are linked with carrier concentration of target materials.

cond-mat.mtrl-sci↗

arXiv2012

Structural/microstructural, optical and electrical investigations of Sb-SnO2 thin films deposited by spray pyrolysis

The structural, optical and electrical properties of spray deposited antimony (Sb) doped tin oxide (SnO2) thin films, prepared from SnCl4 precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0 to 1.5 wt.% of Sb. The analysis of x-ray diffraction patterns revealed that the as deposited doped and undoped tin oxide thin films are pure crystalline tetragonal rutile phase of tin oxide which belongs to the space group P42/mnm (number 136). The surface morphological examination with field emission scanning electron microscopy (FESEM) revealed the fact that the grains are closely packed and pores/voids between the grains are very few. The transmittance spectra for as-deposited films were recorded in the wavelength range of 200 to 1000 nm. The transmittance of the films was observed to increase from 57% to 68% (at 800 nm) on initial addition of Sb (up to [Sb]/[Sn] = 0.5 wt.%) and then it is decreased for higher level of antimony doping ([Sb]/[Sn] > 0.5 wt.%). The sheet resistance of tin oxide films was found to decrease from 48 Ω/sq for undoped films to 8 Ω/sq for antimony doped films.

cond-mat.mtrl-sci↗

arXiv2012

XPS evidence for molecular charge-transfer doping of graphene

By employing x-ray photoelectron spectroscopy (XPS), we have been able to establish the occurrence of charge-transfer doping in few-layer graphene covered with electron acceptor (TCNE) and donor (TTF) molecules. We have performed quantitative estimates of the extent of charge transfer in these complexes and elucidated the origin of unusual shifts of their Raman G bands and explained the differences in the dependence of conductivity on n- and p-doping. The study unravels the cause of the apparent difference between the charge-transfer doping and electrochemical doping.

cond-mat.mtrl-sci↗

arXiv2011

Synthesis and structural/microstructural characteristics of antimony doped tin oxide $(Sn_{1-x}Sb_{x}O_{2-δ})$

Bulk samples of $(Sn_{1-x}Sb_{x}O_{2-δ})$ with x = 0.00, 0.10, 0.20, 0.30 are synthesized by solid-state reaction route. Samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis spectroscopy. The x-ray diffraction patterns indicate that the gross structure/phase of $(Sn_{1-x}$ $Sb_{x}O_{2-δ})$ do not change with the substitution of antimony (Sb) up to x = 0.30. The surface morphological examination with SEM revealed the fact that the grain size in the antimony doped sample is larger than that of undoped one and hence pores/voids between the grains increase with Sb concentration up to 0.30. TEM image of undoped sample indicates that the $SnO_{2}$ grains have diameters ranging from 25 to 120 nm and most grains are in cubic or spherical shape. As antimony content increases, the nanocubes/spheres are converted into microcubes/spheres. The reflectance of $Sn_{1-x}Sb_{x}O_{2-δ}$ samples increases whereas absorbance of these samples decreases with the increased concentration of antimony (Sb) for the wavelength range 360 - 800 nm. The energy bandgap of Sb doped - $SnO_{2}$ samples were obtained from optical absorption spectra by UV-Vis absorption spectroscopy. Upon increasing the Sb concentration the bandgap of the samples was found to increase from 3.367 eV to 3.558 eV.

cond-mat.mtrl-sci↗

arXiv2011

Flux Pinning by Nano Particles Embedded in Polycrystalline Y-123 Superconductors

Bulk superconductor samples of YBa2Cu3-xZnxO7-δ with x = 0, 0.01, 0.03 are synthesized by solid-state reaction route. The structural characterisation of all samples has been carried out by x-ray-diffraction (XRD) and transmission electron microscopy (TEM) techniques. The x-ray diffraction patterns indicate that the gross structure/phase of YBa2Cu3-xZnxO7-δ do not change with the substitution of Zn up to x=0.03. In TEM investigations of Zn-doped Y-based cuprates a number of ZnO nano-flower and nano-rod of Y-211 phase are found dispersed in regular YBa2Cu3-xZnxO7 matrix. These dispersed nano-flowers of ZnO and nano-rods of Y-211 phase may serve as flux-pinning centers. These pinning centers enhance critical current density (Jc) value of these HTSC samples.

cond-mat.supr-con↗

arXiv2011

Microstructural and Superconducting Properties of YBa_2Cu_{3-x}Co_xO_{7-δ} System

Bulk superconductor samples of YBa2Cu3-xCoxO7-δ with x = 0, 0.01, 0.03, 0.05 are synthesized by solid-state reaction route. Both x-ray diffraction and electron microscopy have been employed to study the phase identification, intergrowths, dislocations and the local structure of these samples. Transition temperature of the samples has been determined by four probe resistivity measurements. The x-ray diffraction patterns indicate that the gross structure/ phase of YBa2Cu3-xCoxO7-δ do not change with the substitution of Co up to x=0.05. The zero resistance critical transition temperature [Tc(R=0)] is found to decrease and critical current density (Jc) increases with the increased concentration of cobalt in the compound. The Jc enhancement for the cobalt doped samples may be resulting due to flux pinning from some defects such as planar defects, stacking faults and micro defects (twin, domains etc.) and the rapid suppression in Tc may be due to the cooper pair breaking and the hole filling in the CuO2 planes.

cond-mat.supr-con↗

arXiv2009

`Zero-spin-photon hypothesis' finds another important application: Could possibly solve the `infinity-problem' of QED without the need of renormalization

`Zero-spin-photon hypothesis' as proposed in an earlier paper [1] states that: `due to inevitable consequence of the second-law of thermodynamics and spin-conservation, the `zero-spin-photon' is generated in pair-production process (of elementary particles), which decays into neutrino and antineutrino'. The zero-spin photon hypothesis explains [1] several riddles of physics and universe. In the present paper, it is shown that `the zero-spin photon hypothesis' when incorporated into the higer-order Feynman diagram (with a closed-loop) could possibly solve the half-a-century-old and famous `infinity-problem' of QED, and thus could avoid the need of the so called `re-normalization' procedure.

physics.gen-ph↗

arXiv2009

Zero-spin-photon hypothesis: `Zero-spin-photon generation in pair-production and its subsequent decay into neutrino and antineutrino' - solves many-riddles of physics and universe

`What is work and what is heat' is re-investigated from the perspective of second law of thermodynamics. It is shown that the inevitable consequence of second law of thermodynamics and spin conservation necessitates the possible generation of zero spin photon in pair production process, and its subsequent decay explains the birth of neutrino and antineutrino. The proposed neutrino-genesis, solves many riddles of physics and universe. The riddles considered and explained are about: (i) mysterious neutrino (and antineutrino) and its bizarre properties such as handed-ness and parity-violation, (ii) questionable asymmetry/ excess of matter over antimatter, (iii) possibility of existence of antimatter world and (iv) parity (P) violation and aspects of CP and CPT violation or restoration in the universe.

physics.gen-ph↗