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.

Effect of oxygen plasma immersion ion implantation on the formation of nanostructures over Ni–Ti alloy

Abstract: Ni–Ti alloy has been implanted with oxygen ions by plasma immersion ion implantation (PIII-O). Ni–Ti–O nanotubes are formed by anodic oxidation of PIII-O Ni–Ti alloy. The surface of the modified alloy samples has been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The corrosion behaviors of the Ni–Ti substrate, PIII-O and anodized PIII-O samples have been investigated through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies in simulated body fluid (Hanks' solution). It has been observed that oxygen ion implantation leads to the formation of a thin oxide layer on the Ni–Ti alloy. Anodization of the implanted alloy results in Ni–Ti–O nanotubes. Corrosion resistance of the PIII-O and anodized PIII-O samples shows better corrosion resistance compared to that of untreated alloy.

Strength of rhenium from x-ray diffraction experiments under nonhydrostatic compression to 250 GPa

Abstract: Polycrystalline rhenium in the form of a powder contained in a two-stage gasket was compressed in a diamond anvil cell. No pressure medium was used to ensure that maximum nonhydrostatic stresses that rhenium can support were produced. The pressure was increased in steps to a maximum of 250 GPa and the diffraction pattern recorded at each pressure using energy dispersive technique. The differential stress t, a measure of the compressive strength, was determined at any given pressure from the offset between the measured unit cell volume and volume computed from the pressure-volume relation under hydrostatic pressure. The data suggest that t is 2.5 GPa at a pressure of 5 GPa and increases linearly to 26 GPa at 250 GPa. The present data agree well with those obtained from the radial diffraction data to 37 GPa in an earlier study but differ significantly from the results of another study. Though comparable with the theoretical strength of ideal solids, the observed strengths are extremely large for a polycrystalline aggregate of a solid. The pure pressure effect on the strength described by the shear modulus scaling is inadequate to account for such a large increase of strength with pressure . It is suggested that the major contribution to strength comes from the strain hardening of rhenium that arises due to plastic deformat ion of the sample during nonhydrostatic compression in a diamond anvil cell.

Acoustic Characterization of Jet Interaction with Launch Structures During Lift-Off

Abstract: The structures that constitute the environment surrounding the launch vehicle affect the noise levels experienced by it during liftoff. Earlier studies modeled the launch scenario by incorporating ...

Simultaneous LIF and Mie scattering measurements for branch-like spray cluster in industrial oil burner

Abstract: A technique for planar measurement of size, velocity and liquid volume or surface area of droplet clusters in sprays and the identification of fluid flow structures, which may be responsible for droplet clustering, is reported. The technique was applied in water sprays with added Rhodamine dye at appropriately adjusted concentration to ensure volume dependency of the fluorescence intensity. The spray was injected in a liquid-fuelled burner for a domestic boiler. Combined droplet laser induced fluorescence and Mie scattering images were recorded, using two CCD cameras and appropriate optical filtering, and the ratio of the two light intensity images allowed measurement of instantaneous spatial distribution of droplet Sauter mean diameter (SMD). It was found that droplet clusters formed in regions of high droplet density, but low SMD values compared to the surrounding spray. The identified droplet clusters were tracked between time delayed images and cross-correlation techniques quantified the instantaneous cluster velocity. In the vicinity of droplet clusters, flow structures are identified, using Particle Image Velocimetry, which may be responsible for the formation of droplet clusters. The droplet velocity field was measured by cross-correlation techniques from the Mie scattering and Fluorescence images and agreed well with the velocity of mean droplet diameters corresponding to the Area Mean Diameter (D20) and Volume Mean Diameter (D30) respectively, as measured with the Phase Doppler technique.