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.

Autocatalytic duplex Ni–P/Ni–W–P coatings on AZ31B magnesium alloy

Abstract: Autocatalytic duplex Ni-P/Ni-W-P coatings were deposited on AZ31B magnesium alloy using stabilizer free nickel carbonate bath Some of the coated specimens were passivated in chromate solution with and without heat treatment Plain Ni-P coatings were also prepared for comparison Coatings were characterized for their surface morphology, composition and corrosion resistance Energy dispersive analysis of X-ray (EDX) showed that the phosphorous content in the Ni-P coating is 6 wt% and for Ni-W-P it reduced to 3 wt% due to the codeposition of tungsten in the Ni-P coating Marginal increase in P and W contents was observed on passivated coupons along with Cr (018 wt%) and O (28 wt%) contents Field emission scanning electron microscopy (FESEM) examination of these coating surfaces exhibited the nodular morphology Chromate passivated surfaces showed the presence of uniformly distributed bright Ni particles along with nodules Potenfiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies were carried out in deaerated 015 M NaCI solution to find out the corrosion resistance of the coatings Among the coatings developed, duplex-heat treated-passivated (duplex-HIP) coatings showed lower corrosion current density (i(corr)) and higher polarization resistance (R-p) indicating the improved corrosion resistance The charge transfer resistance (R-ct) value obtained for the duplex-HIP was about 170 times higher compared to that for Ni P coating (c) 2013 Elsevier BV All rights reserved

The structural and electrical properties of TiO2 thin films prepared by thermal oxidation

Abstract: Thin films of TiO 2 were grown on n-type Si substrate by thermal oxidation of Ti films deposited by dc sputtering. The phase purity of TiO 2 was confirmed by Raman spectroscopy, and secondary ion mass spectroscopy was used to analyze the interfacial and chemical composition of the TiO 2 thin films. Metal–oxide–semiconductor capacitors with Al as the top electrode were fabricated to study the electrical properties of the TiO 2 films. The current conduction mechanisms in thermally grown TiO 2 films were observed to follow the space charge-limited current mechanism followed by a Schottky emission process both at and above room temperature. Three orders of magnitude of reduction in current density were observed for thermally grown samples while measured the I – V characteristics at 77 K and Fowler–Nordheim (F–N) tunneling was found to be a dominant conduction mechanism at higher biasing voltages.

Fluid Density Sensing Using Piezoelectric Micromachined Ultrasound Transducers

Abstract: We report on the suitability of a Piezoelectric Micromachined Ultrasound Transducer (PMUT) based system for fluid density measurement in both static and dynamic conditions. We exploit the well-known phenomenon of the virtual added mass induced changes in the resonant frequency of a structure vibrating in a fluid medium to design, fabricate and test a unique PMUT-fluid-PMUT (PFP) system as a fluid density sensor. The proposed system uses through-transmission of ultrasound waves from one PMUT transducer to another identical transducer with the test fluid in between and records the shift in the resonant peak of the receiver PMUT. We also study the sensitivity of the system using different sized PMUTs with resonant frequencies ranging from 140 kHz to 1.8 MHz and show how the system can be designed for a desired sensitivity. Further, we carry out experiments with dynamic density changes by mixing fluids to study how the system could be used to track changes in the density of a flowing liquid in real-time. We also study the effect of the distance separating the transmitter and the receiver to establish the utility of the system in both micro and macro scales in static as well as dynamic conditions.

Active radar cross section reduction : Theory and applications

Abstract: This book discusses the active and passive radar cross section (RCS) estimation and techniques to examine the low observable aerospace platforms. It begins with the fundamentals of RCS, followed by the dielectric, magnetic and metamaterials parameters of the constituent materials and then explains various methods and the emerging trends followed in this area of study. The RCS estimation of phased array including the mutual coupling effect is also presented in detail in the book. The active RCS reduction is carefully touched upon through the performance of phased arrays, sidelobe cancellers and mitigation of multipath effect. Providing information on various adaptive algorithms like least mean square (LMS), recursive least square (RLS) and weighted least square algorithms, the authors also mention the recent developments in the area of embedded antennas, conformal load bearing antenna, metamaterials and frequency selective surface (FSS) based RCS reduction.

Studies on Tensile and Interlaminar Shear Strength Properties of Thermally Cured and Microwave Cured Glass-Epoxy Composites

Abstract: Experimental studies are carried out on two different glass-epoxy composites (one room temperature curing epoxy-amine system and the other, an elevated temperature curing epoxy-amine system) subjected to two different curing techniques (thermal and microwave), in order to investigate the effects on their thermomechanical properties. Microwave (MW) curing is carried out using a laboratory scale, custom-built, multi-mode microwave cure chambery operating at a frequency of 2450 MHz. Tensile and interlaminar shear strength (ILSS) properties of the MW cured composites either compared well, or were superior, to those of their thermally cured counterparts, offering the added advantages of reduced cure cycle time, uniformity of cure, and substantial energy savings. Further, the glass transition temperature (Tlt;subgt;glt;/subgt;) values of MW cured composite laminates are slightly superior to those of thermally cured laminates. amp;copy; 2006 SAGE Publications.