National Aerospace Laboratories

About: National Aerospace Laboratories is a facility organization based out in Bengaluru, India. It is known for research contribution in the topics: Coating & Corrosion. The organization has 1838 authors who have published 2349 publications receiving 36888 citations.

Synthesis and characterization of manganese tetroxide (Mn3O4) nanofibers by electrospinning technique

Abstract: Manganese tetroxide (Mn3O4) nanofibers were prepared by electrospinning homogeneous viscous solution of 20 wt%, 28 wt% and 36 wt% manganese acetate in poly vinyl alcohol (PVA) and calcining the nanofibers at 1000 °C for 2 h. Electrospinning was carried out at 9 kV DC with tip to collector distance (TCD) of 7 cm. Thermo gravimetric analysis (TGA) of the fibers indicates the pure phase of manganese oxide above 500 °C. XRD analysis of calcined (at 1000 °C) nanofibers indicates the formation of phase-pure tetragonal Mn3O4. Scanning electron microscopy (SEM) studies show the fibers cylindrical with the diameters in the range of 100–600 nm and aspect ratio > 1000. In general, the average diameter of the green fibers decreases with the increase in manganese acetate concentration. The diameter of calcined nanofibers is reduced by 34%.

Effect of anodization and annealing on corrosion and biocompatibility of NiTi alloy

Abstract: Anodization of NiTi alloy was carried out on a biomedical grade NiTi alloy in phosphoric acid based electrolyte and subjected to post treatment by annealing. The morphology of anodized surface was porous with irregularly distributed pores and annealing resulted in the formation of nodules of titanium oxides on the porous structure. Studies showed that the corrosion potential shifted to more noble direction after annealing and there was one order decrease in corrosion current density compared to as-anodized surface. Cyclic potentiodynamic polarization behavior of mechanically polished and anodized surfaces was almost similar and both the surfaces exhibited positive hysteresis loop on reversing the scan direction. The formation of negative hysteresis loop in the case of annealed anodized alloy showed that the surface was capable of retaining its passive behavior even at higher potentials. Dynamic impedance spectroscopy studies carried out on annealed anodized surfaces showed that on increasing the potential from open circuit potential (ocp) to higher potentials (0.8 V), the thickness of the oxide layer also increased, but behaved as a leaky capacitor. In terms of bioactivity, the entire surface of the annealed sample was covered with hydroxyapatite after 12 days of immersion in Hanks' solution and the nickel released (370 ppb) was comparatively less than bare NiTi surface (633 ppb).