8369 research outputs found
Sort by
Boron addition to AISI A213/P91 steel: Preliminary investigation on microstructural evolution and microhardness at simulated heat-affected zoneZugabe von Bor zum Stahl X10CrMoVNbN9-1: Voruntersuchung zu Gefugeentwicklung und Mikroharte in simulierter Warmeeinflusszone
No full textThe motivation behind present investigation has been a step to create preliminary understanding towards structure-property correlation i. e., microstructure and microhardness in presence of boron in P91 steel and in its subzones of heat-affected zone with Gleeble simulation. For microstructure characterization and its comparison amongst selected two steels, light microscopy for prior austenite grain size, morphology of prior austenite grain boundaries and scanning electron microscopy at low-resolution and high-resolution in order to study evolution of sub-structure i. e. martensitic lath block structure and nano-precipitates were employed. Electron backscatter diffraction measurements of all coupons were done to understand the distribution and contribution of relative fraction of various grain and sub-grain boundaries within local microstructure. Main effects of addition of 100 ppm boron to standard P91 steel as observed from present microstructural evaluation are; existence of fine nano-precipitates P91-coarse grained heat affected zone than its P91B counterpart, grain refinement in fine-grained heat-affected zone of both steels with partial dissolution of nano-precipitates, coarsened nano-precipitates in P91-fine-grained heat-affected zone after post weld heat treatment, mixed-structure of partially transformed martensite and coarsened undissolved prior austenite grains with nano-precipitates in P91-inter-critical heat-affected zone than P91B-inter-critical heat-affected zone. However, difference in microhardness was primarily owing to variation of nano-precipitates fraction area. In addition, present work induced grounds for microstructure stability i. e., grain boundary hardening in P91B weldments that suppresses type IV failure
Effect of carbide precipitation on Coffin-Manson relationship of a polycrystalline nickel-based superalloy
No full textThis study explores the dual-slope Coffin-Manson (C-M) behavior of a polycrystalline nickel-based superalloy, EA, used in turbine engine applications with an emphasis on discerning the micro-mechanisms responsible for it. The motivation for distinguishing the micro-mechanisms responsible for bi-linear C-M behavior stemmed from the earlier evolved comprehensions that state that the fatigue life estimation based on the extrapolation of any single line gives inaccurate results. Transmission electron microscopy (TEM) investigations of fatigue fractured specimens at low strain amplitudes, Delta epsilon/2, revealed that dislocations are homogeneously distributed in the gamma-channels and occasionally form networks at gamma/gamma ' interface. Whereas deformation is heterogeneous at high Delta epsilon/2 owing to the complex dislocation reactions. Cr23C6 carbides are precipitated during the high Delta epsilon/2 fatigue tests, which act as obstacles for dislocations. The deformation heterogeneity resulting from the dislocation-gamma ' precipitate interactions and the dislocation-M23C6 carbide interactions accounts for the dual-slope C-M behavior
Simultaneous in Situ Exfoliation of Titanate and Zn-Cr Layered Double Hydroxides with a Copolymer for Photocatalytic Degradation of Organic Pollutants
No full textA binary polymeric hybrid nanocomposite has been synthesized by simultaneous grafting of vinylic monomers on dextrin, followed by in situ exfoliation of layered titanate (LT) and Zn-Cr layered double hydroxide (LDH) (g-Dext/LT/LDH). Here, the self-assembling between in situ exfoliated titanate and LDH nanosheets has been carried out by monitoring pH between 6.5 and 7, where the oppositely charged nanosheets experience maximum electrostatic interactions among them. The g-Dext/LT/LDH nanohybrid reveals a higher activity around 96% degradation of ciprofloxacin under natural sunlight irradiation in comparison to the bare LT, LDH, and LT/LDH, providing strong evidence for the superiority of the intimate hybridization between two nanosheets. The improvement of photocatalytic performance of g-Dext/LT/ LDH is attributed to the formation of a heterolayer structure by combining oppositely charged nanosheets, which synergistically improves the photocatalysis process by increasing the surface area and optical absorption property via reducing the migration distance of the photogenerated electron-hole pair and efficiently promoting their separation. Additionally, the antibacterial properties of g-Dext/LT/LDH have also been investigated against Bacillus pumilus (Gram-positive) and Enterobacter cloacae (Gram-negative) bacteria by the disc diffusion study
Advancement of brazing filler alloy: An Overview
No full textThe brazing is a special type of joining technique for the complex parts of any engineering components, such as, heat exchangers, turbine engine parts of aircraft, spacecraft etc. In this method, joining area is significantly narrow (~1mm), which demands a specific joining method with optimum heat input to achieve a near net shape fabricated component. A suitable brazing filler alloy in this respect offers specific characteristics like adequate wetting, low thickness, narrow melting zone, avoidance of intermetallic formation and limited extent of stress generation at joint interface. The methodology is applicable for both similar and dissimilar combination of materials depending on particular requirement. Due to minimal thickness constraint, the brazing filler alloy is synthesized in the form of fine powders, paste, thin foils and controlled coating between / over the substrate to be joined. The thin foils (~50 µm thickness) are fabricated by rapid solidification technique. Paste of suitable composition is produced by mechanical alloying to obtain fine grain structure with overall chemical homogeneity. The mixed product is further wetted by chemical fluid, which is non-reactive to the components of mixture, however can provide substantial fluidity of the paste. There are several methods to produce thin foils. Once the composition is achieved by conventional melting and casting, the desired thickness is obtained by repetitive forging or rolling of the stock. Controlled coating of single / multiple metal can be produced by spattering, physical vapour deposition and chemical vapour deposition of pre-determined thickness over the substrate to be joined. The controlled thickness in all the above cases is apposite to bridge narrow crack or join components. This methodology is also lucrative considering ease in process control as the variables are limited to four only i.e. temperature, normal pressure, time and atmosphere. Thus a transition joint with satisfactory efficiency and structural homogeneity can be easily achieved
Treatment of industrial effluent to reclaim copper using adsorption technique
Get PDFThe effluent generated during metal finishing in industries contains a large amount of heavy metals, which get discharged into water bodies and create environmental pollution as well as loss of metal values. Present studies report the adsorption of copper (Cu) from the effluent using Tulsion T-42 resin. Experiments were carried out for the adsorption of Cu from the effluent of Chemical and Mechanical Polishing (CMP) industries using cationic resin Tulsion T-42 (adsorbent). To get the optimized adsorption condition for copper the studies were carried out with varying process parameters i.e., contact time, adsorbent dose, pH, etc. The result of the batch experiments
shows that 95% copper was adsorbed from the effluent containing 100 ppm copper using 0.1 g Tulsion T-42 in 50 mL feed solution at pH 4.0 in a contact time of 30 min. The obtained data from Cu adsorption studies fitted well with Freundlich adsorption isotherm and followed second-order rate reaction. The 99% copper was found to be eluted from loaded adsorbent using 10% sulfuric acid in 60 min contact time. FT-IR results confirmed that a complex with an active sulphonic group of Tulsion T-42 was formed. The findings of the studies will be useful for the reclamation of copper from the wastewater of metal-finishing industries
A composite electrode of 2D-Ti3C2 (MXene) and polyemeraldine salt of polyaniline for supercapacitor with high areal capacitance
No full textHere, we propose a composite system made of 2D-Ti3C2 and two different chemical forms of polyaniline (PANI) like polyemeraldine base (EB) and polyemeraldine salt (ES) to investigate their electrochemical performances as supercapacitor electrode material. Fundamentally, EB and ES are having different functionalities and electrical conductivities to affect their electrochemical performances. Thus, synthesis and electrochemical performances of the composites made of Ti3C2 and ES or EB with different compositions is discussed where Ti3C2/ES form of PANI appears as best performing supercapacitor electrode with the areal capacitance of 1.85 Fcm(-2) at 5 mVs(-1). A capacitance enhancement of 5.4 times was observed for Ti3C2/PANI-ES while compared to the same for bare Ti3C2 with capacity retention of 91.70% after 500 cycles at 1 Ag-1. This work has also explored the effect of composite compositions by varying the stoichiometric weight ratios of Ti3C2 and different forms of PANI to achieve high-performing supercapacitor electrode materials
Single potential step chronoamperometry for EC' reaction at rough electrodes: Theory and experiment
No full textThe theory is developed for the chronoamperometry of first order homogeneous catalytic chemical reaction coupled with electron transfer (EC') on a rough electrode. We obtained a solution for the diffusion problem on an arbitrary and random topography of the electrode to generalize Danckwerts' equation. Derived equation of random electrode roughness is used for developing theory of (statistically isotropic) self-affine fractal on limited length scales. The characteristics fractal morphological parameters, viz. D-H, l and l(tau), are varied for detailed analysis of current transient. The current transient shows anomalously enhanced response for a rough electrode. Our theoretical results explain both transient and steady-state behavior of the current response under the influence of roughness. The anomalous enhancement of steady-state current is only observed when RMS roughness is greater than bulk reaction-diffusion length (L-k). Finally, the theory is compared and validated with experimental data of ferrocyanide and ascorbic acid coupled system on rough Pt electrodes
Effect of nickel addition on enhancing nano-structuring and suppressing TRIP effect in Fe40Mn40Co10Cr10 high entropy alloy during high-pressure torsion
No full textThe present work unravels the effect of nickel (Ni) addition on the deformation mechanism and hardness evolution in a Fe40Mn40Co10Cr10 high entropy alloy (HEA) during high-pressure torsion (HPT) processing. For this purpose, two variants of the high entropy Cantor alloy, with compositions (atomic%) Fe40Mn40Co10Cr10 (Ni0 alloy) and Fe35Mn35Co10Cr10Ni10 (Ni10 alloy) were selected. The study revealed a transition in the predominant plasticity mechanism with addition of Ni from TRIP in Ni0 to dislocation slip in Ni10 alloy. Such transition of plasticity mechanism was the direct consequence of an increase in the free energy of phase transformation, delta G(gamma ->epsilon) towards a more positive value with Ni addition. Interestingly, the Ni10 alloy showed a greater extent of nano-structuring than the Ni0 alloy with nearly three-fold refined grain sizes, that is, lesser than 30 nm in Ni10 alloy and ~90 nm in Ni0 alloy. Furthermore, a 3-4 times higher dislocation density was observed in the FCC phase of the Ni10 alloy compared to that in the transformed HCP phase in the Ni0 alloy for any given HPT processing conditions. These differences in mechanism(s) of deformation and the extent of nano-structuring manifested as a greater ability of Ni added Ni10 alloy to harden itself during HPT. The present study suggests that a large fraction of hard HCP phase originating from TRIP effect in the Ni0 alloy has a lower hardening ability than the high dislocation density and nano-structuring in the Ni10 alloy
Effect of strip entry temperature on the interfacial layer and corrosion behavior of galvanized steel
No full textThe present work investigates the effect of three different strip entry temperatures (SETs) (500, 575, and 650 ?) on the extremely thin aluminum (Al)-rich inhibition layer formed at the substrate-coating interface during galvanization in a Zn-0.2 wt% Al bath and its correlation with the corrosion behavior in freely aerated 3.5 wt% NaCl solution. The scanning electron microscopy confirms that the morphology of the interfacial layer becomes coarser with an increase in SET. Moreover, the rate of Al uptake at the interfacial layer increases with increasing the SET due to an increase in the effective reaction temperature for the nucleation of Fe-Al crystals at the substrate liquid zinc interface. X-ray diffraction also reveals that the texture coefficient (TC) of the preferred high atomically dense (0002) basal plane of Zn coating is pronounced at lower SETs. It has been found that the coating prepared at 500 degrees C has the lowest corrosion rate of 0.142 mm/y as compared to that prepared at 575 degrees C (0.245 mm/y) and 650 degrees C (0.266 mm/y). Electrochemical impedance spectroscopy also follows a similar trend. It has been observed that the dominance of the highest packing density (0002) crystal plane, compact interfacial layer as well as uniform and compact pore-free coating surface have resulted in the lowest corrosion rate of the coating made at the lowest SET of 500 degrees C
A New Era of Integrative Ice Frozen Assembly into Multiscale Architecturing of Energy Materials
No full textThe ice templating assembly has been investigated to construct macroporous channels of functional nanomaterials with well-defined homogeneous morphology. Recently, this templating method has been revisited integrating with other materials' synthesis and processing methodologies (such as, spinning, spraying, filtration, hydrothermal, oxygenation, gelation, and 3D printing) for electrochemical energy conversion and storage applications. Herein, the recent progress on "integrative ice frozen assembly" focusing on the hierarchical structures and chemistries of functional nanomaterials such as, organic, inorganic, carbon, and composite materials for a rational design of energy application-oriented materials is comprehensively reviewed. This integrative process allows functional nanomaterials to be assembled into various dimensions, such as, 0D, 1D, 2D, and 3D macrostructures, as well as, into larger bulk objects such as, fibers, films, monoliths, and powders. The fundamental understanding of the integrative ice frozen assembly is thermodynamically and kinetically discussed with the help of primitive freeze casting domain knowledge and the energy conversion and storage performances of the as-designed electrodes with their hierarchical structures and chemistries are further correlated. The applications of the as-assembled electrodes into batteries, supercapacitors, fuel cells, and electrocatalysis are also addressed. Finally, the perspective on the current impediments and future directions in this field is discussed