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Development of TSA anodized/MnVO sealed coating using a statistical approach for Al 7075 alloy and a study of its corrosion behaviour
No full textIn this work we propose a statistical approach which optimizes the operating parameters of tartaric sulfuric acid anodizing (TSA) and MnVO oxyanion sealing on Aluminium 7075 alloy. Here we used Response Surface Methodology and Taguchi Design to find an optimum condition for the surfaces with maximum corrosion resistance. This manuscript aims to provide a mathematical model which correlates coating thickness to anodizing parameters like voltage, temperature, sulfuric acid concentration, agitation, duration and tartaric acid concentration. Such combinatory approach has not been introduced or reported till now in optimizing the sealed anodic oxide layer to exhibit improved corrosion resistance. The surface of optimized TSA-MnVO sealed anodized coatings qualified 1000 h of salt spray exposure. The optical microscopic images clearly show the coating has excellent barrier and self-healing corrosion resistance behaviour in NaCl environment. The X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy of sealed anodized surface confirmed the presence of polymerized decavanadate species. The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test results revealed the resistance value of the coating is >15 MΩcm2 and corrosion current density (icorr) value of 4.5 nA/cm2 respectively, indicating excellent protective behaviour of the optimized coating in aggressive chloride environment
Densification, mechanical, and tribological properties of ZrB2-ZrCx composites produced by reactive hot pressing
No full textZrB2‐ZrCx composites were produced using Zr:B4C powder mixtures in the molar ratios of 3:1, 3.5:1, 4:1, and 5:1 by reactive hot pressing (RHP) at 4‐7 MPa, 1200°C for 60 minutes. X‐ray diffraction analyses confirmed the formation of nonstoichiometric zirconium carbide (ZrCx) with different lattice parameters and enhanced carbide formation by increasing the Zr mole fraction. An increase in applied pressure from 4 to 7 MPa was responsible for the improved relative density (RD) of 4Zr:B4C composition from 86% to 99%. Microstructural studies on Zr‐rich composites showed a reduction in unreacted B4C particles and enriched elongated ZrB2 platelets. Reaction and densification mechanism in 4Zr:B4C composition were studied as a function of temperature increased from 600 to 1200°C at an applied constant pressure of 7 MPa. After 1000°C, <40 vol.% of unreacted Zr was observed during the densification process. Concurrently, low energies of carbon diffusion and carbon vacancy formation were found to enhance nonstoichiometric ZrCx formation, which was found to be responsible for the completion of the reaction. The plastic deformation of unreacted Zr was responsible for the densification of the ZrB2‐ZrCx composite. The results clearly showed that the applied pressure is five times lower than the reported values. Moreover, a temperature of 1200°C was sufficient to produce dense ZrB2‐ZrCx composites. The improved microhardness, flexural strength, fracture toughness, and specific wear rate were 8.2‐15 GPa, 265‐590 MPa, 2.82‐6.33 MPa.m1/2, and 1.43‐0.376 × 10−2 mm2/N, respectively
Anti-inflammatory and wound healing potential of a clove oil emulsion
No full textEmulsion formulations of essential oils are of major interest due to their relative biosafety, biocompatibility and good pharmacological potential. Their structural constituents (oil and water phase) facilitate ready solubilization of incorporated hydrophilic/lipophilic actives for their targeted delivery. In the present study, m5S cells were tested for their viability at various concentrations of clove oil and an alkyl polyglucoside emulsifier, viz., Montanov 202™. Thereafter, good cell viable concentrations of oil (10 %) and emulsifier (4%) were used at their optimised ratio (1:0.4) to formulate an oil in water emulsion using phase inversion technique followed by ultrasonication for particle size reduction. Gas chromatography-mass spectrometry (GC–MS) analysis of clove oil revealed eugenol (76.11 %) and eugenyl acetate (12.41 %) as major constituents. The formulated clove oil emulsion was then characterised with respect to its size, zeta potential, microscopic and thermal analysis and the presence of liquid crystals were observed in the same. It was further studied for its anti-inflammatory potential in female Wistar rats wherein topical treatment with the emulsion inhibited paw swelling induced by carrageenan model by 40−60% over 30−180 min compared to untreated animals. Similarly, the emulsion’s wound healing potential was also significant with respect to wounds induced by both incision (wound breaking strength of 338.91 ± 5.02 g) and excision (95 % wound contraction by 16th day) model in these animals, with a re-epithelization period of 10.67 ± 1.67 days and results being comparable with diclofenac gel and neomycin cream (positive controls). Histopathology of the skin sections showed accelerated healing with early granular tissue and collagen formation in emulsion treated animals. It is hence envisaged that this clove oil emulsion can substitute chemical based topical products for anti-inflammatory and wound healing applications due to its biological constituents as well as because of the presence of liquid crystals in its formulation
Design of a two spool contra-rotating turbine for a turbo-fan engine.
No full textContra-rotating turbines offer enhanced performance over their conventional co-rotating configurations. In addition, vaneless contra-rotating turbine stages offer lesser stage length along with improved performance. Contra-rotating turbines with a vaned LP stages offer a controlled work-split between the stages over a wider range of operating conditions by maintaining inlet swirl to the second rotor. The objective of the present work is to design an equivalent vaned contra-rotating turbine for an existing co-rotating configuration of a two-spool turbo fan engine. The contra-rotating turbine is designed by retaining the existing flow path and HP turbine, and redesigning the LP turbine for fixed radial distributions of inlet total temperature, pressure and swirl. A comparative study between performance of the co-rotating and contra-rotating turbines is carried out for different speeds. Cascade testing of the LP stator and rotor mean sections was carried out to validate the analysis. The LP stage of contra-rotating turbine exhibits a performance improvement by 2% points at design point, as per flow predictions. The reduced flow deflection in stator row is the primary reason for significant reduction in profile and secondary losses in contra-rotating turbine, which contributed to the performance improvement. A significant reduction of 23% in blade weight and 45% in LP stator vane count is obtained
El niño–southern oscillation (ENSO) impact on tea production and rainfall in south India
No full textEl Niño–Southern Oscillation (ENSO) is an aperiodic oscillation of sea surface temperature (SST)-induced interannual rainfall variability in south India (SI) that has a direct impact on rain-fed agricultural production and the economy of the region. The study analyzed the influence of ENSO-related rainfall variability on crop yield of south Indian tea-growing regions (SITR) for the period of 1971–2015. The relationship between SST anomalies from June to August over the Niño-3 sector of the tropical Pacific Ocean and tea production anomalies of SI shows a positive correlation. However, SST has a negative relationship with rainfall in the regions of the southwest monsoon but not with the northeast monsoon region of the Nilgiris. The correlation between rainfall and crop yield in SI (r = 0.045) is positively weak and statistically insignificant (p > 0.05). Tea production is influenced more by the cold phase than the warm phase of ENSO, whereas rainfall is greatly influenced by the warm phase. Tea production across the regions indicated that none of the ENSO phase categories based on Niño-3 has significantly greater production than any of the other ENSO phases. Therefore, the predictability of tea production on the basis of ENSO phases is limited. Our findings highlight that the crop production of SITR appeared to be less responsive to the ENSO phases. This may be due to improvements in production technology that mitigated the problems associated with rainfall variability
Citrate combustion synthesized Al-doped CaCu3Ti4O12 quadruple perovskite: synthesis, characterization and multifunctional properties
Get PDFThe facile synthesis of the Al-doped CaCu3Ti4O12 quadruple perovskite, a well-known and vastly studied material for various technological applications, using the modified citrate combustion route along with structural, microstructural, and X-ray photoelectron spectroscopic (XPS) characterization and magnetic, dielectric and electrical properties has been investigated and reported here. The possible applications of the material as a Schottky barrier diode (SBD) in optoelectronic devices and as a catalyst in methanol steam reforming (MSR) reaction for hydrogen generation, hitherto unreported in the open literature, have also been explored. The compound is crystallized in the cubic body centered Im[3 with combining macron] space group and the particle size is found to be in nanodimension with rather narrow size distribution. The enhanced resistivity could be attributed to the grain boundary effect, and consequently, it exhibits better performance as a SBD compared to the undoped sample. Desired cationic composition with expected valence states within the probe range is confirmed by XPS analysis. A better catalytic activity towards MSR is noticed for the Al-doped CaCu3Ti4O12 compared to the undoped composition. These new findings, namely MSR activity and applicability in the Schottky device, have highlighted further the multifunctional nature of the material in energy related issues and would thus be of interest to the materials community searching for functional materials
Properties of PVDF films stretched in machine direction.
No full textPolyvinylidene fluoride (PVDF) films possess superior piezoelectric properties due to the β-phase obtained by methods, such as addition of nanofillers, application of high electric field, use of polar solvents and mechanical stretching. Simultaneous stretching and heating of the films can reduce porosity, increase transformation from α-phase to β-phase, and hence, improve their piezoelectric properties. This article presents the effects of stretching PVDF films on the β-phase formation and the resulting mechanical properties. A custom-designed stretching unit with roller mechanism and heating provision was employed for the purpose. The 200% stretched films at 100°C showed 86.79% β-phase, which is in correlation with X-ray diffraction peaks at 2 θ = 20.3–20.6°. Transmission electron microscopy and scanning electron microscopy of the stretched films revealed spherulitic to lamellar transformation and decrease in porosity. Stretching increased crystallinity from 32.99% to 44.84%. Nanoindentation results showed increase in hardness and Young’s modulus from 23.33 MPa to 93.3 MPa and 0.483 GPa to 1.816 GPa, respectively. Tensile strength increased from 4.72 MPa to 21.02 MPa. The experiments were conducted using L 9 orthogonal array and the results were analyzed using analysis of variance and gray relational analysis
Vapour phase synthesis and characterisation of Cf/SiC composites with self-healing Si-B-C monolayer coating
No full textCarbon fibre reinforced CVI-SiC matrix (Cf/SiC) composite is well known for its superior properties such as low density, high specific modulus, high fracture toughness, and high temperature mechanical properties. In the present work, 2.5-Directional Cf/SiC composites with (PyC/SiC) n=4 multilayer interface having two different thicknesses with a density of ~2.1 g cm-3 are prepared through isobaric isothermal chemical vapour infiltration technique. High temperature tensile properties of the prepared composites with and without Si-B-C seal coating are studied and the results are presented. Samples prepared without seal coat exhibited a KICof ~ 30 MPa m1/2, and tensile strength of ≥200 MPa at room temperature. Si-B-C seal coated Cf/SiC composites has shown significant increase (28%) in high temperature tensile strength at 1200 °C and 1500 °C respectively compared to uncoated composites. Microstructural observations, XRD, and XPS studies support the observed thermomechanical behaviour of these composites at 1200 °C and 1500 °C
Fluid Density Sensing Using Piezoelectric Micromachined Ultrasound Transducers
No full textWe report on the suitability of a PiezoelectricMicromachined Ultrasound Transducer (PMUT) based systemfor fluid density measurement in both static and dynamicconditions. We exploit the well-known phenomenon of thevirtual added mass induced changes in the resonant fre-quency of a structure vibrating in a fluid medium to design,fabricate and test a unique PMUT-fluid-PMUT (PFP) system asa fluid density sensor. The proposed system uses through-transmission of ultrasound waves from one PMUT transducerto another identical transducer with the test fluid in betweenand records the shift in the resonant peak of the receiverPMUT. We also study the sensitivity of the system usingdifferent sized PMUTs with resonant frequencies ranging from140 kHz to 1.8 MHz and show how the system can be designed for a desired sensitivity. Further, we carry out experimentswith dynamic density changes by mixing fluids to study how the system could be used to track changes in the densityof a flowing liquid in real-time. We also study the effect of the distance separating the transmitter and the receiver toestablish the utility of the system in both micro and macro scales in static as well as dynamic condition
Multifunctional KBiFe2O5 thick film: advances in functional properties
No full textThis paper presents the preparation of KBiFe2O5 thick film and its optical (bandgap), ferroelectric, and photovoltaic properties. The XRD of KBiFe2O5 film reveals orthorhombic crystal structure. The polarization study with an electric field (P–E) shows unsaturated and leaky nature of the hysteresis loop. The film shows fatigue-free polarization till 107 switching cycles. A weakly ferromagnetic behavior is observed in the KBFO film at room temperature arising from the canting of G-type antiferromagnetic spins. The film shows spin-frozen behavior below 125 K. The bandgap value of KBiFe2O5 film is found to be 1.67 eV, which is appropriate for visible light absorption. The photovoltaic study on KBiFe2O5 film gives Voc = 1.89 V, Jsc = − 3.04 × 104 A/cm2, and photovoltaic efficiency 0.11%. The photo-ferroelectric coupling in KBiFe2O5 film is established from the directional change in photocurrent with the polarization switching under forward and reverse fields and also from the enhancement of polarization under light illumination