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.

Electroless deposition of Ni–Cu–P, Ni–W–P and Ni–W–Cu–P alloys

Abstract: Interest in electroless plating of nickel-based ternary alloys has increased because of their excellent corrosion, wear, thermal and electrical resistance. They also possess good magnetic properties. In the present investigation, the effect of copper and tungsten in alkaline electroless nickel baths has been studied in depositing Ni–Cu–P and Ni–W–P alloys and also the synergistic effect of ions in depositing Ni–W–Cu–P alloys. Deposits were characterized using XRD, scanning electron microscopy (SEM), energy-dispersive analysis of X-ray (EDX) and atomic force microscopy (AFM) techniques. XRD results revealed that not much variation in structure and grain size has been found in Ni–Cu–P deposit. A decrease in phosphorus content and a marginal increase in grain size have been observed due to the tungsten addition in the Ni–P deposit. Addition of copper in Ni–W–P baths has resulted in a quaternary deposit, Ni–W–Cu–P, with increased crystallinity. SEM studies showed that presence of coarse nodules in ternary Ni–Cu–P and Ni–W–P deposits. Addition of copper in Ni–W–P baths has resulted in a very smooth deposit. Studies by AFM on deposits have proved that the copper has suppressed coarse nodules by inhibiting their growth in quaternary deposit. No considerable change in hardness has been noticed in both as-plated and heat-treated deposits due to the inclusion of copper in Ni–W–P deposit. A marginal improvement in corrosion resistance has been observed in quaternary alloy compared to ternary (Ni–Cu–P or Ni–W–P) alloys.

A study on the influence of process parameters on the Mechanical Properties of 3D printed ABS composite

Abstract: Additive Manufacturing (AM) technologies have been emerged as a fabrication method to obtain engineering components within a short span of time. Desktop 3D printing, also referred as additive layer manufacturing technology is one of the powerful method of rapid prototyping (RP) technique that fabricates three dimensional engineering components. In this method, 3D digital CAD data is converted directly to a product. In the present investigation, ABS + hydrous magnesium silicate composite was considered as the starting material. Mechanical properties of ABS + hydrous magnesium silicate composite material were evaluated. ASTM D638 and ASTM D760 standards were followed for carrying out tensile and flexural tests, respectively. Samples with different layer thickness and printing speed were prepared. Based on the experimental results, it is suggested that low printing speed, and low layer thickness has resulted maximum tensile and flexural strength, as compared to all the other process parameters samples.

Solid state synthesis and thermal stability of HAP and HAP - beta-TCP composite ceramic powders.

Abstract: Powders of pure β-tricalcium phosphate (β-TCP), hydroxyapatite (HAP) and a biphasic composite mixture of HAP+β-TCP were prepared by solid state reaction between two commercially available calcium-based precursors namely, tricalcium phosphate (TCP) and calcium hydroxide (Ca(OH)2). These reactants mixed in the molar ratios ranging from 3 : 0 to 3 : 4 (designated T0 to T4) in deionized water, milled and slip-cast into discs were heat treated in the temperature range of 600°C to 1250°C. The products formed were characterized by X-ray diffraction (XRD) and i.r. spectroscopic techniques for identification of phases formed and functional groups present in them. While tricalcium phosphate and calcium hydroxide taken in the molar ratio of 3 : 2 and 3 : 3 resulted in pure HAP when heat treated at 1000°C for 8 h, the 3 : 1 and 3 : 1.5 molar ratio compositions resulted in a biphasic mixture of HAP+β-TCP for similar heat treatments. Heat treatment of 3 : 4 molar ratio composition of tricalcium phosphate and calcium hydroxide at 1000°C yielded HAP with free CaO as the secondary phase. Products of heat treatment at higher temperatures (1150 and 1250°C) for even shorter duration (2 h) while not differing from the products obtained from T0 and T2 cases at 1000°C (pure β-TCP and pure HAP), change in the case of T1, T1.5, T3 and T4 to products with lesser percentages of HAP containing β-TCP (in the case of T1 and T1.5) or CaO (in the case of T3 and T4) as the secondary phase.

Raman spectroscopy studies on the thermal stability of TiN, crN, TiAlN coatings and nanolayered TiN/CrN, TiAlN/CrN multilayer coatings

Abstract: About 1.5-um-thick single-layer TiN, CrN, TiAlN coatings and nanolayered TiN/CrN, TiAlN/CrN multilayer coatings were deposited on silicon (111) substrates using a13; reactive direct current magnetron sputtering process. Structural characterization of the coatings was done using x-ray diffraction (XRD) and micro-Raman spectroscopy. All13; the coatings exhibited NaCl B1 structure in the XRD data. Raman spectroscopy data of as-deposited coatings exhibited two broad bands centered at 230x2013;250 and 540x2013;630 cmx2212;1.13; These bands have been assigned to acoustical and optical phonon modes, respectively. Thermal stability of the coatings was studied by heating the coatings in air in a13; resistive furnace for 30 min in the temperature range 400x2013;900 xB0;C. Structural changes as a result of heating were characterized using Raman spectroscopy and XRD. Raman13; data showed that TiN, CrN, TiN/CrN, TiAlN, and TiAlN/CrN coatings started to oxidize at 500, 600, 750, 800, and 900 xB0;C, respectively. To isolate the oxidation-induced spectral changes as a result of heating of the coatings in air, samples were also annealed in vacuum at 800 xB0;C under similar conditions. The Raman data of vacuum-annealed coatings showed no phase transformation, and intensity of the optical phonon mode increased and shifted to lower frequencies. The origin of these spectral changes is discussed in terms of defect structure of the coatings. Our results indicate that the thermal stability of nanolayered multilayer coatings is superior to the13; single-layer coatings.