National Aerospace Laboratories
National Aerospace Laboratories Institutional RepositoryNot a member yet
7121 research outputs found
Sort by
Microstructure and functional behaviour of shape memory annealed Ni 24.7 Ti 50.3 Pd 25 and Ni 24.7 Ti 49.3 Pd 25 Sc 1 alloys
No full textNi24.7Ti50.3Pd25 and Ni24.7Ti49.3Pd25Sc1 high-temperature shape memory alloys were thermo-mechanically processed and characterized in the present study. The microstructural characteristics of cold-worked alloys showed the presence of shear/deformation bands and defects. TEM observation of cold-worked and annealed (400 to 500 °C) microstructures revealed the emergence of small fraction of newly formed martensite twins at 400 °C. With the increase in the annealing temperature from 400 to 500 °C, the fraction of the martensite twins in the microstructure was found to increase. The Ni24.7Ti50.3Pd25 and Ni24.7Ti49.3Pd25Sc1 alloys showed martensite finish temperature of ~180 °C and ~136 °C with an hysteresis of ~10 °C and ~9 °C, respectively. Ni24.7Ti50.3Pd25 and Ni24.7Ti49.3Pd25Sc1 alloys showed a recovery strain of 1.5% and 1.7% at a stress of 175 MPa. During cycling under load, the residual strain for the Ni24.7Ti49.3Pd25Sc1 alloy was found to be negligible as compared to ~0.2% in the Ni24.7Ti50.3Pd25 alloy. The results of the study indicate that these alloys have potential for use as high-temperature thermal actuator materials
Optical properties of sputter deposited nanocrystalline CuO thin films
No full textBlack copper oxide thin films with high solar absorptance (α), high thermal emittance (ε), low diffused reflectance and moderate electrical conductivity are required for various light absorption applications and are conventionally prepared using processes involving carcinogen chemicals. Therefore, there is a need to develop these coatings using eco-friendly processes. In this paper, CuO thin films have been deposited on copper, glass and Si substrates using reactive direct current magnetron sputtering of Cu target. The structural, chemical and morphological characterization of the coatings was carried out using X-ray diffraction, micro-Raman spectroscopy, X-ray photoelectron spectroscopy and field emission scanning electron microscopy techniques. The results showed that both oxygen flow rate and sputtering time have a significant effect on the optical properties of the films. The optimized films were found to be of the composition CuO with α and ε of 0.955 and 0.52, respectively. The emissivity could be further increased to 0.78 after sandblasting of the substrate
Spatially resolved structure and domain wall propagation in defect induced SmCo/Co exchange spring magnet
No full textSmCo5/Co exchange-coupled films with high saturation magnetization, and hence high energy product were fabricated on MgO substrates by sequential deposition of elemental Sm and Co layers at 450 °C followed by subsequent annealing at the same temperature for 1 h. Formation of defects induced multi-layered structures and the composition of individual layers were confirmed through high resolution Scanning Transmission Electron Microscopy (HRSTEM) imaging acquired on high angle annular dark field (HAADF) detector and Energy Dispersive X-ray (EDX) spectroscopy. Micromagnetic simulations and magnetic measurements further confirmed that the observed structure is coupled in rigid phase between soft and hard magnetic layers and the enhancement in coercivity results due to the domain wall pinning at the defects sites. This leads to the magnetic energy density in the film of the order of 22.2 MGOe which is close to the bulk value and have potential applications towards Micro-Electro-Mechanical Systems
Multifunctional properties of ceria nanocubes synthesized by a hydrothermal method
No full textNanosized ceria is an extremely versatile and commercially valuable material because of its industrially important applications. The present work describes the synthesis of ceria nanocubes by a simple hydrothermal method. The size of the synthesized ceria nanocubes are 8–20 nm. The formation of ceria phase has been corroborated by X-ray photoelectron spectroscopy and X-ray diffractometry. Selected area electron diffraction patterns obtained for the nanocubes are also precisely indexed to the cubic ceria phase. The synthesized ceria nanocubes exhibit a high surface area of 26 m2 g−1 and also high catalytic activity. The work also investigates the influence of ceria nanocubes on the corrosion resistance of sol–gel hybrid coatings in 3.5% NaCl solution on AA2024 substrates. The corrosion behaviour of the sol–gel coatings revealed that ceria nanocubes reinforce the barrier properties of the sol–gel coatings and confer longer active protection to the metallic substrate
Synthesis, Characterization, and Mechanical Properties Evaluation of Mg-Ti3AlC2 Composites Produced by Powder Metallurgy/Hot Pressing
No full textMagnesium (Mg)-titanium aluminum carbide (Ti3AlC2) composites were produced by hot pressing (HP) at 0.15 to 1 MPa, 923 K (650 °C) for 30 minutes; Mg-Ti3AlC2 (10 to 30 vol pct) composite produced at 0.15 MPa, 923 K (650 °C) for 30 minutes exhibited 95 to 99 pct relative density (RD), while Mg-40Ti3AlC2 produced at 1 MPa, 923 K (650 °C) for 30 minutes exhibited full density. Improved densification results are mainly due to the flow of liquid Mg between the Ti3AlC2 particles. The monolithic Mg processed at 5 MPa, 873 K (600 °C) for 5 minutes also exhibited full density. Further, Mg-Ti3AlC2 composites produced at low pressure (1 MPa) exhibited maximum density as compared to other research works. Monolithic Mg exhibited a microhardness of 62 ± 8 HV0.5. Besides, as the Ti3AlC2 content was varied from 10 to 40 vol pct, the microhardness of Mg-Ti3AlC2 composites increased from 62 ± 5 to 158 ± 11 HV0.5. The compressive strength of Mg-Ti3AlC2 (10 to 40 vol pct) composite at room temperature (RT) was in the range of 180 ± 10 to 617 ± 13 MPa. The compressive strengths of Mg-Ti3AlC2 (30 and 40 vol pct) composites at 473 K (200 °C) were 366 ± 20 and 480 ± 71 MPa, respectively. The flexural strength of Mg-Ti3AlC2 composites (20 to 40 vol pct) was determined to be in the range of 335 ± 12 to 513 ± 3 MPa
Interaction of two micro-propellers in coplanar and coaxial arrangement for UAV application
No full textIn the present work, we have focused on the
understanding of the effect of gap between micro propellers in coplanar and in coaxial arrangements on the thrust generation experimentally. In a way it’s a preliminary optimization of the spacing and placement of the micro propellers in a multirotor
UAV system. APC 12-inch diameter (D) (12X8 E) and Master air screw (MAS) 11-inch diameter (11X6) propellers each 2 in numbers were considered in the study. A static testing rig was built with a provision to mount the propellers in coplanar and in coaxial arrangements. A thrust was measured using a single component load cell. Parameters like current consumption by BLDC motors and propeller RPM were also monitored. For coplanar arrangement, there is no influence of gap (G) between the propellers on the coefficient of thrust (CT). However, for G/D<0.2 random variation in CT is observed. Similarly, for propellers in coaxial arrangement, for smaller gap between the
propellers along the axis is found to generate higher thrust. This optimization of the gap between the propellers may be lead to a compact multi-rotor UAV system having higher payload carrying capacity or higher enduranc
Reclamation of thermal power plant waste as a distributed phase in electrodeposited Ni composite coating
Get PDFIn the exploration for newer and inexpensive distributed phases that can be used in electrodeposited Ni-composite coatings, cenosphere particles which are one of the constituents of fly ash, the waste product of thermal power plants has been explored as a potential candidate material. An attempt was made to prepare electrodeposited Nicenosphere composite coating. The as-received cenosphere particles could be codeposited only after reducing the particle size by ball milling. The loading of cenosphere particles in the Ni-sulphamate bath was varied (25, 75 and 100 g L−1) and a maximum microhardness of 430 HK at 50 gF load was obtained for the coating deposited from 100 g L−1 cenosphere containing bath. The Ni-cenosphere composite coating with higher microhardness exhibited lower wear rate. Thus cenosphere, a waste product from thermal power plants is a potential candidate for a greener surface engineering strategy for improving the wear resistance of electrodeposited Ni composite coating
Sol-Gel synthesis and phase evolution studies of yttrium silicates
No full textAbstract Yttrium silicate powders were synthesised through acid catalysed sol-gel route using Y(NO3)3.6H2O and tetra ethyl ortho silicate (TEOS) as precursors. The crystallographic phases evolved from the prepared gel on calcination at 1100°C were correlated with the experimental parameters used for synthesis. The optimised experimental condition resulted in well defined and crystallised phases of Yttrium disilicate (YDS), yttrium monosilicate (YMS) and biphasic mixture (YDS + YMS) powders on calcinations to 1100°C to 1500°C for 2 h. Surface morphology and structure of the final powders were investigated by XRD, SEM, particle size analysis, FTIR and Raman spectroscopy. The powders show particle size in the range 0.8 μm to 10μm. The YDS, YMS and YDS + YMS powders were pelletised and sintered at 1400°C for 2 h leading to 83 ± 1% dense products
Solution combustion synthesis of calcia-magnesia-aluminosilicate powder and its interaction with yttria-stabilized zirconia and co-doped yttria-stabilized zirconia
No full textThermal Barrier Coatings (TBCs) play a significant role in improving the efficiency of gas turbines by increasing their operating temperatures. The TBCs in advanced turbine engines are prone to silicate particles attack while operating at high temperatures. The silicate particles impinge on the hot TBC surfaces and melt to form calcia-magnesia-aluminosilicate (CMAS) glass deposits leading to coating premature failure. Fine powder of CMAS with the composition matching the desert sand has been synthesized by solution combustion technique. The present study also demonstrates the preparation of flowable yttria-stabilized zirconia (YSZ) and cluster paired YSZ (YSZ-Ln2O3, Ln = Dy and Gd) powders by single-step solution combustion technique. The as-synthesized powders have been plasma sprayed and the interaction of the free standing TBCs with CMAS at high-temperatures (1200 °C, 1270 °C and 1340 °C for 24 h) has been investigated. X-ray diffraction analysis of CMAS attacked TBCs revealed a reduction in phase transformation of tetragonal to monoclinic zirconia for YSZ-Ln2O3 (m-ZrO2: 44%) coatings than YSZ (m-ZrO2: 67%). The field emission scanning electron microscopic images show improved CMAS resistance for YSZ-Ln2O3 coatings than YSZ coatings
Machine-learning for classification of naval targets
No full textNaval target classification is one of the prominent area of research in defence to safeguard ships and to provide guidelines for shipping channels. This work mainly explains the machine learning approach for naval target classification by examining the radar kinematics. The Artificial Neural Network (ANN) model is developed to classify various ship models. The Radar Cross-Section (RCS) data has been used for identification and classification of the naval target. The RCS database for ships are generated by simulating the open domain CATIA models