Santosh Chaudhary

Effect of different acid oxidation on morphology, dispersion and optical band-gap of multi-walled carbon nanotubes

ABSTRACT In this paper the effect of different acid oxidation on morphology, dispersion and optical band gap of multi-walled carbon nanotubes (CNTs) is reported. Oxidation of CVD synthesized MWCNTs were carried out in 8M HNO3, 8M H2SO4, 8M HNO3/H2O2 and 8M H2SO4/HNO3. Oxidized nanotubes sample were characterized by XRD, SEM, FT-IR, TGA, UV-Vis spectroscopy and Raman analysis. Oxidized-nanotubes show a lower shift in XRD peak and an increase in d-spacing, which implies deterioration of MWNTs. New peaks in FT-IR spectra of oxidized-nanotube samples at around 1742 cm−1 confirms the presence of carbonyl groups. Optical bandgap, molar absorptivity coefficient is estimated for pristine and oxidized nanotubes sample using UV-Vis spectroscopy data and Tauc plot. It is observed that optical bandgap decreases on oxidation and lowest bandgap 2.92 eV is observed for H2SO4 treated MWNTs. The information on the optical bandgap of the MWNTs is of great importance for the development of optoelectronic devices.

Design of Octagonal and Decagonal Lattice Photonic Crystal Fiber for Achieving Ultra Low Flattened Dispersion

This paper presents some key concepts of design and optimization of solid core photonic crystal fiber (PCF) based on different geometries for broadband applications. The three different geometrical structures, hexagonal, octagonal, and decagonal of photonic crystal fiber, are designed for different air filling fractions at pitch length 2 μm. The parameters affecting the light propagation through PCF structure such as effective refractive index, chromatic dispersion, mode effective area, nonlinear coefficient, and V parameter are numerically analyzed and compared using finite element method (FEM) on COMSOL Multiphysics software.

Design and Analysis of Spiral Photonic Crystal Fiber for Ultra-Flattened Dispersion for C+L+U

A design of two-dimensional photonic crystal fiber with circular air hole, and it analyzes for large fattened dispersion for diameter 0.6 um in the wavelength range 1.55–1.78 µm. A step-by-step design optimization is demonstrated and maximum optimized value of total dispersion for diameter of 0.6 µm at 1.25 µm is 3.65 ps/nm.km. The PCF has spiral layout. There are five rings around the air core. Three layouts of spiral PCF are designed for different diameter of air hole and compared with layout having decagonal structure using finite element method. The optimized design can be used as dispersion control and as well as dispersion shifted photonic crystal fiber.

Partial slip and thermal radiation effects on hydromagnetic flow over an exponentially stretching surface with suction or blowing

This paper is devoted to analyze computational simulation to study the partial slip and thermal radiation effects on the flow of a viscous incompressible electrically conducting fluid through an exponentially stretching surface with suction or blowing in presence of magnetic field. Using suitable similarity variables, the nonlinear boundary layer partial differential equations are converted to ordinary differential equations and solved numerically by Runge-Kutta fourth order method in association with shooting technique. Effects of suction or blowing parameter, velocity slip parameter, magnetic parameter, thermal slip parameter, thermal radiation parameter, Prandtl number and Eckert number are demonstrated graphically on velocity and temperature profiles while skin friction coefficient and surface heat transfer rate are presented numerically. Moreover, comparison of numerical results for non-magnetic case is made with previously published work under limiting cases.