The Density Functional Theory (DFT) And DFT+U Study of The Effect of The on-Site Coulomb Repulsion Parameter U on The Structural and Magnetic Properties of Ceo2 Nanoparticles

a

Fe Doped Mno2 Nanostructured Thin Films: Synthesis and Characterization for Biosensor applications

Iron (Fe), a magnetic transition metal, doped manganese oxide (MnO2) nanostructured thin films were deposited onto glass substrates by a spray pyrolysis deposition technique at 450oC substrate temperature for glucose sensing performance. Fe concentration greatly affects the film surface morphology. The film was found to be more compact and porous for 4 at % Fe doping. The glucose response was measured by electrical four probe method using the pure MnO2 and 2, 4, 6, 8 at% Fe doped MnO2 thin films as an active electrode. It was determined that 4 at % Fe: MnO2 thin film with 20 nm crystallite size has high sensitivity, fast glucose response and recovery time. Optical band gap measurement indicated that the sensitivity increased as the band gap decreased up to 4 at% Fe concentration. The highest glucose sensing response was recorded about 29 % in 5 minutes. Bangladesh Journal of Physics, 27(1), 1-12, June 2020

Structural Analyses of [Li Salt+Triglyme)] and Ionic Transport in Li-Air Battery Using Molecular Dynamics Simulation

In this work, molecular dynamics (MD) study of triglyme (G3) solution containing lithium bis (trifluoro methyl sulfonyl) amide (Li[TFSA]) were investigated using classical atomistic force fields. G3 is a typical solvent used in non-aqueous Li-air battery. It shows here coordination of Li+ with G3 and [TFSA]- does not significantly change with increasing the concentration of G3 but self-diffusion coefficient of all the ions increases with increasing G3 concentration. The density of [Li(G3)[TFSA] complex decreases with increasing G3 concentration which lead to accelerate diffusivity of ions. Bangladesh Journal of Physics, 27(1), 13-22, June 2020

Impact of Thickness and Substrate on Optical Properties of Zno Thin Films

During the last decades, ZnO has emerged as the most promising material in optoelectronic and optical applications in the visible region as well as in the infrared and UV region. It is because of the broad direct band gap of 3.37 eV at ambient temperature and high exciton binding energy of 60 meV allowing it to utilize the ultraviolet region. In this investigation, the optical characteristics of ZnO thin film of various thicknesses (300 nm, 600 nm, 900 nm) deposited on Quartz, Fused silica and Sapphire have been studied as a function of wavelength and photon energy. To obtain this, the equations for thin film have been derived, simulated and visualized by Matlab coding language. It is observed that with the increase in the photon energy, the refractive index and extinction coefficient show an increasing tendency. The results represent that among three substrates Fused silica has the lowest refractive index, reflectance and absorbance. In the visible region, the transmission spectra show that the average transmittance of all films is 85%-95%, which is superior for solar continuums. The performance of Fused silica as transparent conducting material is better than other substrates. The present investigation might provide an environment friendly and low cost material for optoelectronic and solar cell devices. Bangladesh Journal of Physics, 27(1), 59-68, June 2020

Effects of Pump-Pulse Width and Temperature on Experimental Brillouin Gain Spectrum Obtained from Brillouin Optical Time-Domain Analysis Sensors

In this paper, the characteristics of Brillouin gain spectrum (BGS) obtained from a Brillouin optical time-domain analysis (BOTDA) sensor are investigated and analyzed experimentally. The measured BGSs obtained for various pump-pulse widths and temperatures are fitted with different spectrum profiles using nonlinear least-squares curve fitting technique. The fitting performances of used profiles are presented and analyzed. Based on such performances, the proper spectrum profile to be used in the fitting process is determined and used to extract key parameters of the measured BGSs accurately. The variations of such key parameters with pump-pulse widths and temperatures are also investigated and analyzed. The results reveal that pump-pulse widths and temperatures have significant effects on the extracted key parameters of the measured BGSs obtained from BOTDA sensors. Bangladesh Journal of Physics, 27(1), 69-80, June 2020

Phase Transition, Dielectric Relaxation and Impedance Spectroscopy of Perovskite xBa0.95Sr0.05Tio3-(1‒X)BiFe0.9Sm0.1O3 Ceramics

Polycrystalline xBa0.95Sr0.05TiO3-(1‒x)BiFe0.9Sm0.1O3[xBST-(1‒x)BFSO] ceramics were synthesized. The structural phase transitions were studied and it was found that structure of the compound transformed from rhombohedral to cubic phase. The compound exhibited a dielectric anomaly in the vicinity of Néel temperature of BiFeO3 except for x = 0.25. Enhanced dielectric properties were noticed and this might be attributed to the reduction of oxygen vacancies. Studies of electrical conductivity over a wide temperature range showed that the ceramics behaved like a semiconductor with the negative temperature coefficient of resistance. Contribution of grains in conduction mechanism of the materials dominated and the grain resistance was found to be decreased with the increase in temperature. A Non-Debye type relaxation was seen in the material. The impedance data were re-plotted using the modulus formulae to avoid the ambiguity arising out of the presence of grain/grain boundary effect. Activation energy was found to be 0.18 to 0.33 eV in modulus study which was very close to complex impedance observation and it was implied that the charge carrier had the same energy barrier during the relaxation. Bangladesh Journal of Physics, 27(1), 23-42, June 2020

Investigation on the quality of silicon extracted from the Padma river sand using magnesio-aluminothermic process

Investigation on the quality of the extracted Silicon (Si) from the sand of the Padma river of Bangladesh using the Magnesio-Aluminothermic process has been presented in this work. Magnesio-Aluminothermic process, which is low-energy, low-cost and CO2 free compared to conventional carbothermic process, was used for the extraction of Si from the sand. By performing the thermite process, Si was extracted as a eutectic mixture of Aluminium and Si, following that, several cycles of acid leaching were used to obtain highly pure polycrystalline silicon. After grinding the cleaned sand and making a homogeneous mixture with associated chemicals and ignition materials, modified Aluminothermic reaction was performed to produce a eutectic mixture of Si and Al. Grinded eutectic mixture of Si and Al was then purified with acid leaching and finally above 97% pure crystalline Si was extracted. XRD (X-ray diffraction) and Raman Spectroscopy confirmed the polycrystalline nature of Si where XRF (X-ray fluorescence) and EDX (Energy Dispersive X-ray Spectroscopy) corroborated the high purity of extracted Si describing the chemical composition. Bangladesh Journal of Physics, 26(2), 33-40, December 2019

Establishment of a new nuclear medicine facility: fundamental structure and their shielding

This work was an attempt to propose a model to set up for newly establishment of Nuclear Medicine facility. Medical physicist should establish a major guideline to set up a model of a new nuclear medicine facility; draw the fundamental structure and calculate the corresponding shielding. The various layouts such as the diagnostic (In-Vivo and In-Vitro) and therapeutic layouts of fundamental structure were been made on the primacies as controlled, supervised and non-supervised area according to radiation exposure rate. Some shielding calculations of various facilities such as the diagnostic and therapeutic facility have to provide on instrumentation and radiation safety with the required layout according to maximum activity of radionuclide into the controlled area. Bangladesh Journal of Physics, 26(2), 41-49, December 2019

Effect of calcium carbonate filler and alkali treatment on physical and elastic properties of jute mat reinforced polyester resin composites

Polyester resin-jute mat reinforced composites with different wt% of calcium carbonate (CaCO3) filler were fabricated using a simple cold press molding method. The effects of CaCO3 filler and alkali (NaOH) treatment on various physical and elastic properties were evaluated. Water absorption (WA) increases with the increase of soaking time and load. The maximum WA was observed for 5 wt% addition of CaCO3 and for more CaCO3, WA decreases. The ultimate tensile strength (UTS) and flexural strength (FS) decreases with the addition of CaCO3 for 0.5 wt% NaOH treated composites but for 5 wt% NaOH treated composites UTS and FS increases with the addition of CaCO3 filler. The optimum filler addition is about 5 wt% CaCO3. With the addition of CaCO3, tangent modulus increases for 0.5 wt% NaOH treated composites and for 5 wt% NaOH treated composites it increases up to a maximum value and then decreases. The effect of load on tensile and flexural properties is also discussed. Bangladesh Journal of Physics, 26(2), 61-68, December 2019

Effect of Sr-substitution on the structural and magnetoelectric properties of Ni-Zn ferrites

Spinel type polycrystalline Ni0.6-xZn0.4SrxFe2O4 (x = 0.0, 0.05, 0.10, 0.15 and 0.20) ferrites are synthesized by solid state reaction method. X-ray diffraction (XRD) pattern reveals the formation of spinel structure with two secondary phases Sr2FeO4 and SrFe12O19 for higher concentration of Sr (0.15 and 0.20). An increase in lattice constant is observed with the increase of Sr content in the lattice. The density of the samples is found to decrease whereas porosity increases with the substitution of Sr2+ ions. Microstructural investigation shows that the grain size increases with the increase of Sr content. Magnetic hysteresis is investigated at room temperature. All the samples exhibit lower coercivity values indicating that the materials belong to the class of soft ferrites. The saturation magnetization is found to decrease with Sr content which is attributed to Néel’s two sub-lattice model of ferrites. The real permeability of the samples remains almost constant up to a certain frequency and then falls rapidly. Improved dielectric constant is observed in the Sr2+ substituted samples. The electrical conduction in these ferrites is explained on the basis of hopping mechanism between the Fe2+ and Fe3+ ions. Bangladesh Journal of Physics, 26(2), 1-20, December 2019