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.

Frequency Selective Surfaces based High Performance Microstrip Antenna

Abstract: In order to fulfill the growing demand high-performance low RCS antenna in stealth technology, FSS-based antenna is found to be the better candidate. In view of this, the design and analysis of microstrip patch antennas (MPA) loaded with (i) FSS-based HIS (high-impedance surface) ground plane and (ii) FSS-based superstrate are presented in this book with proper formulations and graphical presentations.

Preparation of zirconia and silicon carbide whisker biphasic powder mixtures by carbothermal reduction of zircon powders

Abstract: Carbothermic reduction of zircon powders has been studied under argon and nitrogen gas pressures of 0.15 MPa in order to obtain biphasic composite powder mixtures containing zirconia and silicon carbide whiskers. The reduction has been carried out using different mole ratios of carbon and zircon. Carbon was used in the form of activated charcoal (specific surface area ∼1000 m2g−1) or carbon black (specific surface area ∼300 m2g−1). Whilst complete decomposition to m-ZrO2 was obtained in the argon atmosphere at 1700 °C, under the nitrogen atmosphere the conversion was incomplete even at 1700 °C. However, the extent of conversion to zirconia at 1650 °C under nitrogen was found to be more than that under argon gas. In a few cases, particularly under the nitrogen atmosphere, minor amounts of other forms of zirconia e.g., tetragonal (t)-ZrO2 or orthorhombic (o)-ZrO2 were formed along with the major monoclinic (m)-ZrO2 phase. The rate of reaction was found in general to increase with an increase in the carbon content. The studies particularly indicate that activated charcoal is a better reducing agent than carbon black owing probably to its enormous surface area. Further, it was also noted that cobalt chloride and sodium chloride act as a catalyst and a space forming agent respectively. They aid silicon carbide whisker formation and growth and hence the reaction is appreciably accelerated and reaches completion at 1650 °C in the argon atmosphere.

Situation and Threat Assessment in BVR Combat

Abstract: Modern fighter aircraft are equipped with Beyond Visual Range (BVR) missiles that can be fired at the enemy from very long distances. Since BVR combat occurs outside the range of the pilot's vision, they must rely on information from the on-board and off-board sensors and sources to determine the location of an opposing aircraft. Pilots make decisions based on the air surveillance picture portraying tracks of airborne targets that is obtained by mentally fusing the information coming from several sources. The workload on the pilots increases as the number of targets in combat arena grows or the situation becomes complex. Therefore to reduce the workload on the pilots, it is required to automate some of the decision making activity. In this paper, a decision support system named Intelligent System for Situation Assessment in Air-Combat (ISSAAC) is developed based on Fuzzy logic and Bayesian Network hybrid technique to assist the pilots participating in BVR combat. The main focus is on the development of the mental model of pilot. The developed system is an integration of platform models, sensor models, pilot mental models and data processing algorithms. The capability of the system is demonstrated by simulating an air-to-air combat scenario consisting of six targets.

Characterization And Microhardness Of Electrodeposited Ni-W Coatings Obtained From Gluconate Bath

Abstract: Ni–W alloy coatings are electrodeposited with direct and pulse current using gluconate bath at pH5. Effects of direct current (DC) and pulse current (PC) on structural characteristics of the coatings have been investigated by energy dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). EDXS shows that W contents are 13.3 and 12.6 at.% in DC and PC (10:40) Ni–W coatings, respectively. FESEM analysis exhibits the homogeneous coarse nodular morphology in DC plated deposits. DSC studies reveal that Ni–W coatings are thermally stable up to 400°C. XPS studies demonstrate that DC plated coating has significant amount of Ni and W in elemental form along with their respective oxidized species. In contrast, mainly oxidized metals are present in the as-deposited coatings prepared with PC plating. The microhardness of pulse current (100:400) deposited Ni–W coating is about 750 HK that is much higher than DC plated coating (635 HK). Heat treatment of the deposits carried out at different temperatures show a significant increase in microhardness which can be comparable with hard chromium coatings.

Biocompatible response of hydroxyapatite coated on near-β titanium alloys by E-beam evaporation method

Abstract: Biomedical implants such as dental and orthopedic implants fails due to poor mechanical and biological properties. In order to solve this problem, Electron beam (e-beam) evaporations is used as one of the methods to deposit the hydroxyapatite (HA) on Ti-13Nb-13Zr (near β titanium alloy) and the coated implant may play a significant role in increasing the mechanical and biological properties. In the present study, Ti-13Nb-13Zr was coated with hydroxyapatite (HA) by e-beam evaporation technique. The coated alloys were morphologically analyzed by FESEM and AFM, and it demonstrates that there is an increase in the growth of calcium phosphate layer. In-vitro corrosion behavior of the coated and uncoated titanium alloys were performed by electrochemical impedance spectroscopy (EIS) studies in simulated body fluid solution. The results show that the corrosion resistance of the hydroxyapatite-coated alloy higher than that of the uncoated alloys and it evident that the HA-coated alloy have better corrosion protection for the implant application. The bioactivity of the HA-coated composites were evaluated by Hanks’ solution immersed them for seven days. The ratio Ca/P was increased gradually after soaking it for seven days. The cell viability results indicates that HA coated alloys support increase in the Osseo integration and it can be used for bone implant application.