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.

Improved corrosion protection of aluminium alloy AA 2024 by sol-gel hybrid coatings after surface pretreatment by silanisation

Abstract: Sol–gel derived organic–inorganic hybrid coatings have been investigated as a potential replacement for the environmentally hazardous chromate conversion coatings for corrosion protection of aerospace aluminium alloy AA 2024 Sol–gel hybrid coatings were prepared using a sol mixture (1∶1 volume ratio) of 3-glycidoxypropyl trimethoxysilane and tetraethoxysilane and doped with cerium nitrate and deposited on AA 2024 by dip coating and spray coating techniques The effect of surface pretreatment on the corrosion protection efficiency of the sol–gel hybrid coatings was studied The corrosion resistance of the coatings in 3·5% sodium chloride solution was evaluated by potentiodynamic polarisation measurements, electrochemical impedance spectroscopy and salt spray tests The results showed that a sol–gel coating system with a simple silanisation as surface pretreatment exhibited improved corrosion protection for AA 2024

Preparation and Characterization of SnO2 Nanofibers by Electrospinning

Abstract: Tin oxide (SnO2) nanofibers are successfully prepared by electrospinning homogeneous viscous solutions of tin acetate in polyvinyl alcohol (PVA) in the ratios of 20:80, 25:75 and 30:70 (by weight). The electrospinning is carried out by applying a DC voltage of 7 kV to the tip of a syringe and maintaining the tip to collector distance (TCD) of 7 cm, i.e. at DC electric field of 1 kV.cm−1. The electrospun nanofibers are calcined at 1000°C for 2 h. Both as spun and heat treated nanofibers are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), etc. The specific surface area of the as spun nanofibers is 110 m2.g−1. TGA of nanofibers indicates complete decomposition of the organics at 550°C. XRD analysis of calcined nanofibers confirms the formation of pure tin oxide. SEM study shows cylindrical fibers with diameter in the range of 20-200 nm with aspect ratio >1000. In general, average diameter of the green fibers decreases with the decrease of PVA co...

Interannual Variability of Tropical Rainfall Characteristics and the Impact of the Altitude Boost from TRMM PR 3A25 Data

Abstract: Global and regional interannual variations of rainfall characteristics over the tropics were examined by applying empirical orthogonal function (EOF) analysis to TRMM PR 3A25 data from December 1997 to December 2007. The TRMM PR 3A25 data and other TRMM datasets detect the interannual variation of rainfall over the tropics, in concert with the SST change, which is closely related to the El Nino/La Nina cycle, including the pseudo-El Nino periods in 2002 and 2004. In addition, we examined the impact of the altitude boost of the TRMM satellite from 350 km to 400 km in August 2001 and found that the boost affects the annual cycle in light rain rates (total, convective, and stratiform). A baseline shift occurs in the annual cycle of light convective rain rate (convRainH) with more (less) frequent occurrence before (after) the boost. In addition, amplitude changes were observed in the annual cycle of light stratiform and total rain rates with more (less) frequent occurrence before (after) the boost. However, for the interannual variation, the coherent spatio-temporal structure of the El Nino/La Nina cycle is evident, and the interannual variation does not indicate any boost impact. In contrast, for heavy convRainH, the number events decreases after the boost, especially over land; however, it is difficult to conclude that this reduction is related to the boost.