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In-situ deposited CdS NPs on pH induced fully exfoliated layered titanate-biopolymeric composite and its photocatalytic activity
No full textHerein, pH mediated in-situ formation, stabilization, exfoliation of layered titanate has been explored for various types of exfoliation of the stacked layered titanate (H2Ti2O5·H2O). Based on exfoliation, a CdS NPs/exfoliated layered titanate based crosslinked biopolymeric nanohybrid has been developed via in-situ approach. The synthetic strategy of polymeric hybrid-composite follows simultaneous increase of the degree of polymerisation, in-situ controlled decomposition/hydrolysis of the pre-stage stacked layered titanate and its full exfoliation, followed by the growth of CdS NPs on the surface of exfoliated titanate nanosheets at 75 °C. Further, the investigation on photocatalytic degradation has been carried out in details to correlate the advantages of exfoliation and deposition of CdS NPs on stacked/unstacked titanate towards degradation of toxic 2,4-dichlorophenol under sunlight irradiation
Study on hydrogen embrittlement and dynamic strain ageing on low-alloy reactor pressure vessel steels
No full textTensile tests in air with hydrogen pre-charged smooth specimens and slow strain rate tests with smooth and notched specimens in hydrogenated high-temperature water (HTW) at elevated tempera- tures (250 −288 °C) on low-alloy reactor pressure vessel (RPV) steels revealed a softening in strength and a pronounced reduction in ductility, where the magnitude of hydrogen embrittlement (HE) increased with the dynamic strain ageing (DSA) susceptibility of the RPV steels. In hydrogen pre-charged specimens and in hydrogenated HTW, shear dominated transgranular fracture by microvoid coalescence with increasing amounts of macrovoids, quasi-cleavage regions and secondary cracking were observed. Thermal desorp- tion spectroscopy showed an increase in the concentration of trapped hydrogen in high binding energy traps (vacancies & voids) induced by straining in DSA regime. The observed hydrogen effects on frac- ture behaviour is a consequence of plasticity localization resulting from the interaction between DSA and hydrogen. HESIV and HELP are the dominant HE mechanisms
Attainment of high specific hardness and specific modulus in spark plasma sintered aluminium-copper-silicon carbide-titanium carbide hybrid compositeHohe spezifische Harte und spezifisches Schubmodul von einem sparkplasmagesinterten Aluminium-Kupfer-Siliziumkarbid-Titankarbid-Verbundwerkstoff
No full textAluminium matrix hybrid composites have been consolidated effectively by spark plasma sintering with new combinations of reinforcement and high volume percentage of ceramic particulates to maximize specific hardness and specific modulus through the powder metallurgy route. The aforementioned techno-scientific accomplishment with regard to metal matrix composite aims to meet a continuous increase in the global demand for a material with minimum structural weight and high-modulus for structural (automotive and aerospace) applications. The new aluminium based hybrid composite developed by incorporating ceramic particulate reinforcements (12.5 wt.% silicon carbide and 12.5 wt.% titanium carbide) along with 22.5 wt.% copper as the metallic reinforcement attains significantly high specific hardness (85 HV/gcm(-3)), specific Young's modulus (33.56 GPa/g cm(-3)), specific bulk modulus (27.97 GPa/g cm(-3)) when compared with the reported range of specific hardness (13 HV/g cm(-3)-89 HV/g cm(-3)), specific Young's modulus (24 GPa/g cm(-3)-27 GPa/g cm(-3)) and specific bulk modulus (20 GPa/g cm(-3)-22 GPa/g cm(-3)) possessed by structural steels. This is accredited to the genesis of a novel microstructure that consists of fine copper, silicon carbide and titanium carbide particulates together with a nominal in-situ originated aluminium-copper equilibrium phases distributed in a highly substructured aluminium based matrix with a significant dislocation density (7.56 . 10(14) m(-2))
An overview on chemical processes for synthesis of graphene from waste carbon resources
No full textGraphene, the wonder material has brought a revolutionary change in the feld of nanotechnology owing to its tremendous
properties. Though diferent methods for the synthesis of graphene have been reported, the chemical synthesis route ofers
a scalable and high-volume production of graphene. The unreliability of graphite and hydrocarbon resources to serve as
steady supplies of carbon resources and further in the synthesis of graphene has led to the exploration and use of alternative
low-cost carbon-rich resources (coal, graphite, rice husk, sugarcane bagasse, peanut shells, waste tyres, etc.) as precursors for
graphene synthesis. The use of untraditional carbon resources reduces dependence on traditional resources (coal, graphite),
reduced cost, increased reliability, and provides a way for the management of waste biomass. This review hence focuses on
the synthesis of graphene by the most common approachable method, oxidation–reduction of graphite, along with the vari-
ous other chemical methods of synthesis from varied carbon resources
Development of corrosion-resistant electroplating on AZ91 Mg alloy by employing air and water-stable eutectic based ionic liquid bath
No full textThe present investigations construe study of Ni electroplating on AZ91 alloy in novel ChCl- ethylene glycol eutectic based ionic liquid using non-fluoride and non-chromium surface pretreatments and sandwiched electroless Ni-P layer. The electroplating employed Ce(NO3)(3) containing pretreatment offered highest corrosion resistance with corrosion current density similar to 0.9 mu A cm(-2) and sustained 10 h salt spray exposure without failure. The coating produced with Ce(NO3)(3) pretreatment showed highest critical load similar to 15.53 N and exhibited better adhesion strength than that produced using NiCO3. The coating performance is correlated with porosity index and NiP2 phase evolved after heat treatment
Effect of Beam Oscillation on Creep Properties of Electron Beam Welded AISI 316L Stainless Steel
No full textButt-joints of AISI-316L stainless steel sheets were produced by electron beam welding process using both static and oscillating beams. The creep properties of the joints were investigated by conducting open-atmosphere creep rupture tests at 650 and 700 degrees C under an applied stress of 200 MPa. Such tests demonstrated higher creep-rupture life (more than twice) for oscillating beam joints than the static beam joint. Better creep properties for oscillating beam joints have been attributed to their narrow weldment region with homogenous microstructure and 6-ferrites of lathy morphology
Effect of Grain Refiner on Microstructural Feature Influence Hardness and Tensile Properties of Al-7Si Alloy
No full textThe effect of grain refiner on microstructural features, casting defects, formation of precipitates and eutectic Si particles, which influence the hardness and tensile properties of Al-Si alloys, is investigated in this study. The A-7Si alloy was prepared through melting and casting route with varying wt.% of Ti up to 0.2%. XRD, SEM and HRTEM analyses characterize the phases and aluminide (TiAl3 and Ti7Al5Si12) precipitates. The thermodynamic analysis, carried out by using FactSage software, confirms the presence of aluminides particle in the microstructure, which is formed at the liquid stage. The microstructure of as-cast Al-7Si alloy contains primary alpha-Al phase with dendritic morphology and eutectic phase having plate-like eutectic Si particle which is distributed at interdendritic regions. The morphology of primary alpha-Al grains is altered from dendrite network to fine equiaxed rosette type structure. Secondary dendrite arm spacing (SDAS) is reduced after adding grain refiner (Al-5Ti-1B) to the Al-7Si alloy. The eutectic Si is also refined to fine fibrous type particles. The shrinkage porosity and microcracks are also reduced after the addition of a grain refiner. The yield strength, ultimate tensile strength and elongation to fracture increase from 84, 117 MPa and 16% to 112 MPa, 148 MPa and 22%, respectively, after the addition of 0.1% Ti due to significant reduction in SDAS. Elongation decreases when the percentage of Ti increases more than 0.1%. The fracture mechanism of grain-refined alloy is changed from brittle to ductile fracture
Modified coke breeze distribution in Iron ore sintering - A Novel technique of reducing energy consumption and improving quality
No full textIn normal sintering of iron ore, there is a wide difference in temperature of the sinter bed between top and bottom; i.e. the flame front temperature of the sinter bed gradually increases towards the bottom because the lower part gets longer time for drying and preheating by exit gas. Therefore, the top part may have insufficient fusion and the bottom is excessively fused. Thus, sinter quality may become inhomogeneous and the coke breeze requirement becomes higher than the actual thermal requirement. If it is charged in multiple layers; e.g. higher amount of coke at the top and a lower amount of coke at the bottom, heat will be homogeneously distributed and the actual coke requirement would be lower than the existing. However, no study has been done so far on this. Therefore, the current study explores the possibility of reducing energy consumption in iron ore sintering by reducing the coke ratio from top to bottom without deteriorating the sinter property. 12% reduction in coke breeze rate has been found and the sinter quality has been improved by the use of a triple layer of sinter mix with a lower coke rate towards the bottom. Further, when 5-vol% of oxygen has been enriched in suction gas along with using a triple layer of sinter mix, up to an 18-wt% reduction in coke breeze has been found
Processing of Low-Carbon Deep-Drawing Steel with High Plastic Anisotropy Using Two-Stage Batch Annealing Cycle
No full textAnisotropy in texture determines capacity of the steel to achieve maximum plastic flow in the plane of the sheet and maximum resistance to flow in a direction perpendicular to the sheet. Present work has been carried out to explore the potential of maximizing plastic anisotropy (r(m)) value in extra deep-drawing steel. Industrial heat was made with low carbon (0.03 wt.%), low manganese (0.15 wt.%), and low sulfur (0.007 wt.%) levels. Continuously cast slabs were hot-rolled and then cold-rolled to 1 mm thickness. The cold-rolled sheets were subsequently subjected to annealing in an annealing simulator furnace adopting specially designed two-stage batch annealing cycle. In batch-annealed steel samples, grains were found to be recrystallized and had undergone grain growth preferentially along the longitudinal direction with strong gamma fiber, comparable to that of Interstitial Free steel. Excellent combination of strength and forming properties, in terms of yield strength 190 MPa, ultimate tensile strength 290 MPa, and total elongation 45%, YS/UTS: - 0.66 with very high plastic anisotropy (r(m)): 2.45, could be achieved. Properties achieved have been correlated with the alloy chemistry, processing path history, percentage reduction, two-stage batch annealing cycle and the resultant grain size, microstructure and texture
Distribution of scandium in red mud and extraction using Gluconobacter oxydans
No full textThe aim was to study bioleaching of rare earth elements from red mud by a chemoorganotrophic microorganism,
and to investigate the microbe-mineral interactions. Red mud is a promising resource for scandium, whose
concentration was 92 and 54 mg/kg in two samples from Germany and India, respectively; however, both
showed appreciably high concentration of zirconium. A gluconic acid-producing bacterium, Gluconobacter oxydans
(DSMZ 46616), was used in the bioleaching experiments under parametric variation of inoculum concentration,
pulp density, and culture adaptation. At a solid load of 10% (w/v) red mud with 10% (v/v) bacterial
inoculum at 37 ◦C, a maximum solubilisation of 83% and 94% Sc was observed after 18–20 d of incubation for
Indian and German red mud, respectively. The total amount of gluconic acid excreted by the bacteria increased
with an increase in pulp density up to 10% (w/v). After bioleaching, SEM-EDAX analysis of the solid residue
depicted enrichment of zirconium associated with the silicate matrix, and the bacterial cells were adhered to the major mineral matrix