Reversible,repeatable and low phase transition behaviour of spin coated nanostructured vanadium oxide thin films with superior mechanical properties

Smooth, uniform and crystalline vanadium oxide thin films were deposited on quartz by spin coating technique with four different rpm i.e., 1000, 2000, 3000 and 4000 and subsequently post annealed at 350, 450 and 550?°C in vacuum. Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were utilized for microstructural characterizations and phase analysis, respectively, for vanadium oxide powder and deposited film. Nanorods were observed to be grown after vacuum annealing. X-ray photoelectron spectroscopy (XPS) technique was utilized to study the elemental oxidation state of deposited vanadium oxide films. Thermo-optical and electrical properties such as solar transmittance (τ_s), reflectance (ρ_s), absorptance (α_s), infrared (IR) emittance (ε_ir) and sheet resistance (R_s) of different thin films were evaluated. Based on the optical characteristics the optimized condition of the film processing was identified to be spin coated at 3000?rpm. Subsequently, the nanoindentation technique was utilized to measure hardness and Young's modulus of the optimized film. The measured nanomechanical properties were found to be superior to those reported for sputtered vanadium oxide films. Finally, temperature dependent phase transition characteristics of optimized vanadium oxide films were studied by differential scanning calorimetry (DSC) technique. Reversible and repeatable phase transition was found to occur in the range of 44–48?°C which was significantly lower than the phase transition temperature (i.e., 68?°C) of bulk VO₂.     

Evaluation of surface/interface quality,microstructure and mechanical properties of hybrid additive-subtractive aluminium parts

A disadvantage of selective laser melting (SLM) processes for the manufacture of large parts is their slow build time per unit volume. A hybrid route is to generate core simple shapes traditionally, for example by machining, followed by adding final features by SLM. Here the mechanical integrity of such hybrid parts is studied, choosing the building of AlSi10Mg by SLM on a machined AA6082 base, in the shape of a tensile test piece, as a simple example. These materials are chosen for their relevance to lightweight parts. As-built parts fail at the SLM/machined interface but standard heat treatments transfer failures to the machined material. Optimised SLM processing conditions and microstructures of the SLM and interfacial regions are reported.     

Influence of microstructural inhomogeneities on the fracture toughness of modified 9Cr–1Mo steel at 298–823 K

Quasistatic fracture behaviour of two heats of modified 9Cr–1Mo steel for steam generator applications have been assessed at 298, 653 and 823 K. J–R curves were established and the elastic–plastic fracture toughness values at 0.2 mm crack extension (J_0.2) were determined. The fracture mechanisms were entirely different for the two steels at 298 K, with brittle fracture controlled by cleavage crack initiation in one and ductile fracture in the other by void nucleation and growth. At 653 and 823 K, fracture in both materials was by ductile crack growth. The difference in behaviour between the two steels at 298 K was attributed to the differences in microstructure, distribution and density of inclusions as well as phosphorous contents.     

Morphology,Mineralogy and Mixing of Individual Atmospheric Particles Over Kanpur (IGP): Relevance of Homogeneous Equivalent Sphere Approximation in Radiative Models

Estimation of the direct radiative forcing (DRF) by atmospheric particles is uncertain to a large extent owing to uncertainties in their morphology (shape and size), mixing states, and chemical composition. A region-specific database of the aforementioned physico-chemical properties (at individual particle level) is necessary to improve numerically-estimated optical and radiative properties. Till date, there is no detailed observation of the above mentioned properties over Kanpur in the Indo-Gangetic Plain (IGP). To fill this gap, an experiment was carried out at Kanpur (IITK; 26.52°N, 80.23°E, 142 m msl), India from April to July, 2011. Particle types broadly classified as (a) Cu-rich particles mixed with carbon and sulphur (b) dust and clays mixed with carbonaceous species (c) Fe-rich particles mixed with carbon and sulfur and (d) calcite (CaCO₃) particles aged with nitrate, were observed. The frequency distributions of aspect ratio (AR; indicator of extent of particle non-sphericity) of total 708 particles from April to June reveal that particles with aspect ratio range >1.2 to ≤1.4 were abundant throughout the experiment except during June when it was found to shift to high AR range, >1.4 to ≤1.6 (followed with another peak of AR i.e. >2 to ≤2.4) due to dust storm conditions enhancing the occurrence of more non-spherical particles over the sampling site. The spherical particles (and close to spherical shape; AR range, 1.0 to ≤1.2) were found to be <20% throughout the experiment with a minimum (11.5%) during June. Consideration of Homogeneous Equivalent Sphere Approximation (HESA) in the optical/radiative model over the study region is found to be irrelevant during the campaign.     

Analysis of Elevated Temperature Flow Behavior of 316LN Stainless Steel Under Compressive Loading

To understand the flow behavior of a newly developed austenitic stainless steel 316LN with 0.14 wt% nitrogen, isothermal compression tests have been carried out in the hot working domain. From the analysis of flow behavior, it is observed that the nitrogen enhanced steel, in its hot working domain exhibits strain and strain rate hardening with thermal softening. The flow behavior analysis also demonstrates the coupled effect of strain–temperature and strain rate temperature on the flow stress. To depict the flow behavior of the material, strain compensated Arrhenius (SCA) equation and Model D8A have been used. The SCA predicts the flow curves with an average absolute error of 9.27% and a correlation coefficient of 0.977, whereas the prediction by Model D8A gives the average absolute relative error as 10.86% with a correlation coefficient of 0.966. For high temperature and intermediate strain rate, both Model D8A and SCA equation depict the flow behavior of 316L (0.14)N SS with good correlation and generalization. However, at low temperature and high strain rate domain, both the models are unable to depict the behavior; this is attributed to the fact that the material shows two slope behaviors where the constants have been calculated assuming a linear relationship between stress and strain rate.     

Flow Behaviour of Modified 9Cr–1Mo Steel at Elevated Temperatures

In this investigation, the flow behaviour of modified 9Cr–1Mo steel at elevated temperatures is reported. To understand the flow behaviour of the steel, tensile tests were performed at nominal strain rate of 3 × 10^?3 s^?1 and temperatures in the range of 300–823 K. The yield strength and ultimate tensile strength were found to decrease with increase in temperature with a plateau in a intermediate temperature regime (523–673 K). Serrations were also observed in the tensile curve at intermediate temperatures which caused plateau/peak in tensile behaviour of material and was a typical manifestation of dynamic strain ageing. An attempt was made to represent the flow behaviour of the material using different constitutive equations viz., Hollomon, Ludwik, Swift, Ludwigson and Voce. It was observed that the Voce equation could describe the experimental flow curve at different temperatures quite well. Instantaneous work hardening rate with respect to flow stress exhibited two stages of hardening especially at relatively lower temperatures.     

Isolation and identification of phosphate‐solubilizing microorganisms and distribution of orthophosphate in different seasons from sewage‐fed East Kolkata Wetland

This study focused on isolation and identification of possible phosphate‐solubilizing bacteria (PSB ) from the sewage‐fed East Kolkata Wetland (EKWL ), a prospective water resource for pisciculture. In addition, different limnological parameters have been correlated with orthophosphate and seasonal variations. PSB have been isolated in Pikovskaya medium and identified morphologically and biochemically and finally analysed by 16S rDNA gene sequence. Limnological studies involving temperature (potentiometric), pH (potentiometric), dissolved oxygen (iodometric), ammonia‐nitrogen (spectrophotometric) and orthophosphate (spectrophotometric) concentrations were conducted. The results of this study established the presence of Bacillus megaterium , a potential PSB in EKWL . The activity of B. megaterium is also supported by the seasonal orthophosphate variations. The changes in concentration of other limnological parameters were also prominent. The water quality parameters of temperature (r  = 0.886), dissolved oxygen (r  = 0.729) and ammonia‐nitrogen (r  = 0.396) concentrations exhibited a positive correlation with orthophosphate and a negative correlation with pH (r  = ?0.699). The B. megaterium obtained in this study, exhibited a significant alteration in regard to orthophosphate content and relationships with other factors. Further experiment on the soluble phosphorus solubilization potential of B. megaterium revealed the biological availability of phosphorus was increased by threefold after 120 hr of incubation, with the decreasing pH value, although the phytase activity was 0.419 U/ml. PSB have a vital function in plant nutrition in supplying phosphate, essential nutrients and its uptake results in appropriate functioning and metabolism of different aquatic plants and organisms. PSB are competent biofertilizer to amplify aquaculture production for sustainable development.