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Angular absorptance and thermal degradation analysis of TiB2/Ti(B,N)/SiON/SiO2 multilayer solar absorber coating
No full textMultilayer solar selective absorber coatings have been developed in the last few decades. The thermal stability in terms of microstructure gives an insightful understanding of the optical properties of such coatings. In this context, we extensively utilized transmission electron microscopy (TEM) analysis to establish the thermal stability of TiB2/Ti(B,N)/SiON/SiO2 coating, under thermal cycling/continuous heating to 500°C in vacuum for 250 h. In particular, this work reports the variation in the solar absorptance of TiB2/Ti(B,N)/SiON/SiO2 coating with different angles of incidence of the solar radiation. Extensive analysis using the TEM technique reveals the presence of oxide interlayers that act as diffusion barrier layers to enhance the thermal stability of the coating. Computational simulation using SCOUT software validates the measured reflectance spectrum of the developed multilayer coating. The minor changes in absorptance and emissivity after heat treatment in vacuum at 500°C, together with high solar absorptance over a broad angular variation, establish the potential application of TiB2/Ti(B,N)/SiON/SiO2 as a selective coating in concentrated solar power systems
Control of flow separation over an axisymmetric flared body using ramped vanes
No full textExperiments were performed at Mach 2 to assess the effectiveness of Ramped Vanes (RVs) in delaying the onset of shock-induced flow separation due to an axisymmetric compression corner. A cone–cylinder-flare model with a 24° flow deflection angle at the cylinder/flare juncture was selected for this study. A single row of RVs was placed 50 mm (10) upstream of the compression corner, to manipulate the incoming boundary layer and thereby bring alterations to the shock–boundary layer interaction flowfield. RVs with three sub-boundary layer heights viz. 1.4 mm, 2.1 mm and 2.8 mm (h/
, 0.50 and 0.67 respectively) were employed and their separation control performance was compared. Counter-rotating vortices originated from these devices, generating alternate upwash and downwash bands within the boundary layer. When the shorter devices were used, early and delayed onset of separation were noticed along the upwash and downwash regions respectively. However, as the devices grew taller, the increase in separation length along the upwash region seemed to diminish. Ultimately, when the tallest devices (h=2.8 mm) were introduced, the entire corrugated separation line was successfully pushed downstream of the uncontrolled separation line. Besides instigating these variations in the separation scale, the vortices also caused topological changes within the separation region. But, despite achieving a substantial delay in separation, the RVs were unable to shift the separation shock’s oscillations to higher frequencies
Low cost, contamination-free, and damage-free fabrication of PZT MEMS on SOI substrate
No full textThis paper reports a generalised process flow for the fabrication of lead zirconate titanate based piezoelectric micro electromechanical system devices. The optimised process can be used to realise several devices with different 1D and 2D geometries on a single wafer. All the state-of-the-art fabrication methods introduce some damage to the active piezoelectric material. This damage entails the need for an additional step of recovery anneal in the fabrication process. Our process was designed and optimised to avoid any such damage to the Lead Zirconate Titanate (PZT) layer. Remnant polarisation and effective transverse piezoelectric coefficient (e31, f) were used as metrics to quantify the damage to the PZT layer. It is shown that our process does not damage the PZT thin film during the fabrication, and hence no recovery anneal is required. We observe a ∼3× improvement in remnant polarisation and ∼2× improvement in e31, f of PZT thin film compared to the PZT thin film subjected to our previous fabrication process. Moreover, the process explained here uses only wet chemical methods for patterning of contaminating agents (PZT and platinum), making it a cost-effective process
Tensile behavior of ceramic matrix minicomposites with engineered interphases fabricated by chemical vapor infiltration
No full textCeramic matrix composites (CMCs) exhibit quasi-ductile behavior beyond the initial elastic region driven by a weak fiber-matrix interface that can be further engineered by introducing a finite thickness interphaseleading to enhanced strength and toughness. The current work explores the engineering of interphases in CMCs by a controlled variation of fabrication process parameters. C/BN/SiC minicomposite configurations have been fabricated by chemical vapor infiltration (CVI) with the intent of varying interphase thickness and constituent volume fractions by varying the interphase and matrix infiltration durations. The effect of processing durations on the resulting microstructure, tensile response, and damage mechanisms up to and during ultimate failure of CMC minicomposites have been investigated. The presented results highlight the significant influence of processing duration on the tensile and failure behavior of CMC minicomposites thereby providing an insight into the processing-microstructure-tensile response relationship in CMCs
Kinematic and Dynamic Analysis of Primary FCS Circuits of Typical 25 Seater Transport Aircraft
No full texthis research work presents kinematic and dynamic analysis of primary flight control surface actuation mechanisms including aileron, elevator and rudder of typical mechanically controlled transport aircraft. The 3D CAD models of the actuation mechanisms are constructed using SolidWorks. The circuit assemblies are exported to MSC ADAMS for detailed kinematic and force analysis. An elaborate simulation model is built in MSC ADAMS to understand the kinematic relations and to estimate the forces acting on all links, brackets and joints under the action of aerodynamic loads on the control surfaces. Analytical formulations are developed to verify the results of the force analysis. Further, the effect of inertia of control surfaces on the pilot forces is studied in detail and discussed
Green synthesis of ITO nanoparticles using Carica papaya seed extract: impact of annealing temperature on microstructural and electrical properties of ITO thin films for sensor applications
No full textThis paper reports the synthesis of indium tin oxide (ITO) nanoparticles and the effect of annealing temperature on the microstructural and electrical properties of ITO thin films. The synthesized ITO (90:10) nanoparticles are deposited at 29°C using E beam evaporation to form ITO thin films and annealed at 200, 400 and 500°C. The microstructural properties are investigated using XRD and AFM , and electrical properties such as temperature coefficient of resistance (TCR) and gauge factor are investigated using four-probe and four-point beam bending method, respectively. The investigations results reveal an increase in grain size, carrier concentration and gauge factor with an increase in the annealing temperature. The absolute value of TCR is constant at high temperatures for the film annealed at 500°C. The ITO thin film annealed at 500°C shows improved morphological and electrical properties and can be used for the development of sensors operating at high temperature
Correlating in-plane strength anisotropy with its microstructural counterpart for a hot rolled line pipe steel
No full textThe present study focuses on the microstructural entities, emphasizing the role of precipitates on the in-plane directional tensile responses, including the strain hardening behaviour of a hot rolled X-65 Line pipe graded steel. Tensile samples have been prepared from four different directions lying on the RD-TD (rolling direction-transverse direction) plane at the varying angle of 0°, 30°, 60°, and 90° with respect to the RD of the hot-rolled plate. Superior mechanical properties have been evidenced in the 90° sample compared to other orientations in terms of maintaining yield continuity and better strength-ductility combination. The yielding behaviour and tensile response have been explained from the viewpoint of grain/grain boundary characteristics, dislocation-precipitation interaction, and elasto-plastic incompatibility across grain boundaries. The role of interaction of dislocations with fine precipitates along with the Elastic Modulus (EM) and Schmid Factor (SF) differences across high angle grain boundaries (HAGBs) have been found to be significant in determining the superiority of the mechanical properties of 90° sample
Reaction, densification, and mechanical properties of Ti2AlCx ceramics at low applied pressure and temperature
No full textTi2AlCx ceramic was produced by reactive hot pressing (RHP) of Ti:Al:C powder mixtures with a molar ratio of 2:1:1–.5 at 10–20 MPa, 1200–1300°C for 60 min. X-ray diffraction analysis confirmed the Ti2AlC with TiC, Ti3Al as minor phases in samples produced at 10–20 MPa, 1200°C. The samples RHPed at 10 MPa, 1300°C exhibited ≥95 vol.% Ti2AlC with TiC as a minor phase. The density of samples increased from 3.69 to 4.04 g/cm3 at 10 MPa, 1200°C, whereas an increase of pressure to 20 MPa resulted from 3.84 to 4.07 g/cm3 (2:1:1 to 2:1:.5). The samples made at 10 MPa, 1300°C exhibited a density from 3.95 to 4.07 g/cm3. Reaction and densification were studied for 2Ti–Al–.67C composition at 10 MPa, 700–1300°C for 5 min showed the formation of Ti–Al intermetallic and TiC phases up to 900°C with Ti, Al, and carbon. The appearance of the Ti2AlC phase was ≥1000°C; further, as the temperature increased, Ti2AlC peak intensity was raised, and other phase intensities were reduced. The sample made at 700°C showed a density of 2.87 g/cm3, whereas at 1300°C it exhibited 3.98 g/cm3; further, soaking for 60 min resulted in a density of 4.07 g/cm3. Microhardness and flexural strength of Ti2AlC0.8 sample were 5.81 ± .21 GPa and 445 ± 35 MPa
Effect of minute element addition on the oxidation resistance of FeCoCrNiAl and FeCoCrNi2Al high entropy alloy
No full textThe effect of Ti0.1 and Ti0.1Si0.1 addition on the high temperature isothermal oxidation behavior of dense FeCoCrNiAl and FeCoCrNi2Al high entropy alloy (HEA) consolidated by vacuum hot pressing were investigated by X-ray diffraction, Scanning Electron Microscopy and Raman Spectroscopy. Mechanical properties such as hardness, Young's modulus, and thermal properties such as differential scanning calorimetry (DSC) and coefficient of thermal expansion (CTE) were also investigated. The weight gain recorded after isothermal oxidation for 5,25,50 and 100 h at 1050 °C was found to be parabolic in nature. X-ray diffraction analysis (XRD), as well as Raman spectroscopy analysis of HEA's oxidized at 1050 °C for 100 h, shows the formation of the Al2O3 phase. A homogeneous thin oxide scale without any discontinuity was observed throughout the cross-section. Ti and Si addition in 0.1 at. % improves mechanical properties, oxidation resistance, and reduces waviness of the oxide scale
Influence of AC-TIG weld current on dissimilar AA5083 and AA 7075 aluminium alloy
No full textDissimilar weld made of AA5083 and AA 7075 aluminium alloys using TIG welding (Current inthe range of 80120 amps) has investigated. Ultimate tensile strength of different weld joints fabricated at different current considered for assessing the joint quality. The results demonstrated that an optimum weld current of 100 amp yielded ~ 283 MPa tensile strength. Compositional analysis across weld pool has shown a signature of Mg vaporisation and Zn retention resulting in yielding high weld strength. The dilution curves of the Zn in 7075 side of TIG welded specimens show a gradual decrease in Zn fraction in HAZ leads to failure of tested samples along the HAZ side of AA7075. It has found that in the weld microstructure,there is a tendency in the weld zone for stabilising Mg by forming various intermetallic phases