Somnath Biswas

Diluted magnetic semiconductors of Zn-doped CeO2 nanoparticles synthesized by a chemical precursor method

Nanocrystalline Zn-doped CeO2 (Ce1-xZnxO2, x=0, 0.05, 0.10 (x% CZO)) were synthesized following a simple chemical precursor method. Structural analysis of the samples revealed their stable face-centred cubic (fcc) crystal structure of Fm3m space group. The optical band gap (Eg) in the samples showed a red shift from 3.30 eV to 3.16 eV with the increase in the Zn concentration from 0 to 10 wt%. Raman analysis confirmed the formation of oxygen vacancies (Vo) in the lattice due to Zn doping.Nanocrystalline Zn-doped CeO2 (Ce1-xZnxO2, x=0, 0.05, 0.10 (x% CZO)) were synthesized following a simple chemical precursor method. Structural analysis of the samples revealed their stable face-centred cubic (fcc) crystal structure of Fm3m space group. The optical band gap (Eg) in the samples showed a red shift from 3.30 eV to 3.16 eV with the increase in the Zn concentration from 0 to 10 wt%. Raman analysis confirmed the formation of oxygen vacancies (Vo) in the lattice due to Zn doping.

Mechanical Behaviour under Quasi-Static Loading of Open-Cell Foams of 6061-T6 Al Alloys Processed by Pressurized Salt Infiltration Technique

Here, we report the mechanical behaviour of open-cell foams of 6061-T6 Al-alloys under quasi-static loading. The foams were processed by pressurized salt infiltration technique with efficient control over pore size and distribution. Spherical salt beads of NaCl of required size distribution were used as preforms. The molten alloy was infiltrated into the preforms under an inert gas pressure of 2 bar followed by cooling and leaching of the salt pattern in a suitable aqueous medium. The pressurized infiltration process is convenient to overcome the capillary forces arising from the non-wetting conditions between salt beads and molten alloys and offers a versatile and economical route for the production of open-cell foams. The shape, size and distribution of the pores were studied with optical microscope and X-ray computed tomography (X-ray CT). The developed foam samples were cut into required dimensions following ASTM E9-09 standard and their mechanical properties were analyzed under quasi-static compressive loading.

Effects of Ni Concentration on the Structural and Magnetic Properties of NiZnFe2O4 Ferrites Synthesized via a Polymer Precursor

In this paper, we report the experimental observations of the effects of Ni concentration on the structural and magnetic properties of NixZn1-xFe2O4 (x=0.2-0.8) ferrite nanoparticles synthesized by a chemical method via a polymer precursor. The synthesis process involves a reaction of aqueous solutions of metal salts (Fe3+, Zn2+ and Ni2+) with an aqueous poly-vinyl alcohol (PVA)-sucrose solution at 65-70oC. Controlled growth of the ferrite nanoparticles was achieved by encapsulation of the nucleating sites in the PVA-sucrose polymer micelles. Structural properties of the derived samples were analyzed with X-ray diffraction (XRD) and X-ray absorption near edge spectroscopy (XANES) studies. The magnetic properties of the NixZn1-xFe2O4 (x=0.2-0.8) nanoparticles were evaluated at room temperature with a vibrating sample magnetometer (VSM). XRD analysis confirmed the formation of single phase cubic spinel ferrite structure. The local structural analysis of the Ni-Zn ferrite crystal system performed with XANES studies at Fe K-edge revealed the migration of Fe3+ ions from the octahedral sites to tetrahedral sites with the increase in Ni2+concentration in the ferrite structure.It was observed that the magnetization increases with the increase in Ni concentration till the maximum saturation magnetization was observed in the composition Ni0.5Zn0.5Fe2O4. Further increase in Ni concentration reduces the magnetization. The obtained results were analyzed in correlation with the cationic distributions at the lattice sites in these ferrite nanoparticles.

Effects of Annealing on Pulsed Laser Deposited TiO2 Thin Films

Mixed phase TiO2 thin films of rutile and anatase type crystal orientations were deposited on Si substrates by pulsed laser deposition (PLD) technique. When annealed at 800°C at 1 mbar oxygen pressure for 3 h, the deposited films transform into a single phase of rutile type. Structural and morphological studies of the as-deposited and annealed films were performed with X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), Raman spectroscopy, and atomic force microscopy (AFM). Photoluminescence (PL) spectroscopy was used for optical characterization of the annealed thin films.

Epitaxial thin films of half-metallic CrO 2 deposited on oxidized Si substrates by PLD using Cr 2 O 3 target

Epitaxial thin films of half-metallic compound CrO2 with (110) crystal orientation have been deposited on oxidized Si (100) substrates by pulsed laser deposition (PLD) technique using KrF excimer laser and Cr2O3 target. The deposited films were characterized with XRD, SEM, FTIR, surface profilometry, AFM and spectroscopic ellipsometry.

Modeling of Indentation Studies of Reduced Porous Ni-8YSZ Anode and Electrolyte Structures

Department of Mining and Geological Engineering, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA We present a finite element model to simulate the indentation of NiO-8YSZ anode /8YSZ electrolyte structure for solid oxide fuel cell applications. The model focuses on the study of mechanical integrity of structure subject to mechanical load. Simulations showed that brittle cracks start to form within the anode due to high