Gupta, Ankur

The optofluidic microreactor, a convergence of optics and microfluidics, offers advanced functionalities that can be pivotal in the rapid assessment of nanocatalysts for tackling environmental contamination issues. This article presents an efficient approach for degrading Methylene blue (MB) dye, commonly used in the textile industry, within a cost-effective polydimethylsiloxane (PDMS) based continuous flow optofluidic microreactor. This microreactor combines graphene quantum dots (QDs) and NH2-MIL-125 (MOF(Ti)) as a highly effective photocatalyst coating within its microchannels. By directly incorporating graphene QDs@MOF(Ti) into the microchannels, the photocatalytic medium is brought into close proximity with the flowing MB dye solutions, thereby reducing the necessary interaction time and enhancing purification efficiency. Furthermore, the findings demonstrate an impressive degradation efficiency of ∼99% for MB dye at a flow rate of 50 μL min−1 under visible light irradiation, achieved in a single pass. Additionally, the microfluidic reactor exhibits prolonged stability of the photocatalyst, enabling its reuse without significant efficiency loss. In addition, a comparative analysis highlights the advantages of microreactor-based photocatalysis over traditional methods. These advancements in the features of the graphene QDs@MOF(Ti) nanocomposite substantiate their demonstrated superiority in degradation efficiency.

This study delves into the microstructure and mechanical properties of a dissimilar metal weld (DMW) joining Incoloy 800HT and P91 steel. The P91 was buttered with Inconel 82 (ERNiCr-3) filler layers, and the final DMW weld was fabricated using Inconel 617 (ERNiCrCoMo-1) filler. Weld interface regions were characterized using electron backscatter diffraction (EBSD) and scanning electron microscopy. EBSD uncovered unique microstructural characteristics across the DMW. Extensive investigation was conducted on the heat-affected zone (HAZ) of Incoloy 800HT, revealing a consistently stable austenitic microstructure characterized by random grain orientations. Nevertheless, the weld fusion zone (WFZ) exhibits an intricate microstructure characterized by dendrites that extend into packets. The WFZ and the buttering layer interaction exhibited a predominantly face-centered cubic (FCC) structure. Recrystallization was indicated in this region. During tensile testing, the DMW specimens experienced failures at different locations and exhibited varying mechanical properties. A standard specimen made of Incoloy 800HT base metal experienced failure during welding. The DMW exhibited a maximum ultimate tensile strength (UTS) of 671 MPa and a yield strength (YS) of 234 MPa. The buttering process helped avoid the post-weld heat treatment to a certain extent. A maximum of 98 ± 5 J Charpy impact toughness was observed in the WFZ of the DMW failing in a complete ductile mode.

Dissimilar metal welded (DMW) joint plays a crucial role in constructing and maintaining ultra-supercritical (USC) nuclear power plants while presenting noteworthy environmental implications. This research examines different welding techniques utilized in DMWJ, specifically emphasizing materials such as P91. The study investigates the mechanical properties of these materials, the impact of alloying elements, the notable difficulties encountered with industrial materials, and the concept of buttering. The USC nuclear power plants necessitate welding procedures appropriate for the fusion of diverse metal alloys. Frequently employed methodologies encompass shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and flux-cored arc welding (FCAW). Every individual process possesses distinct advantages and limitations, and the choice of process is contingent upon various factors, including joint configuration, material properties, and the desired weld quality. The steel alloy known as P91, which possesses high strength and resistance to creep, is extensively employed in advanced ultra-supercritical (AUSC) power plants. P91 demonstrates exceptional mechanical characteristics, encompassing elevated-temperature strength, commendable thermal conductivity, and notable resistance against corrosion and oxidation. The presence of alloying elements, namely chromium, molybdenum, and vanadium, in P91, is responsible for its improved characteristics and appropriateness for utilization in (AUSC) power plant applications. Nevertheless, the utilization of industrial materials in DMW joint is accompanied by many noteworthy concerns, such as the propensity for stress corrosion cracking (SCC), hydrogen embrittlement, and creep deformation under high temperatures. The challenges mentioned above require meticulous material selection, process optimization, and rigorous quality control measures to guarantee the dependability and sustained effectiveness of DMW joint. To tackle these concerns, a commonly utilized approach referred to as buttering is frequently employed. When forming DMW joint in nuclear facilities, it is customary to place a buttering coating on ferritic steel. This facilitates the connection between pressure vessel components of ferritic steel and pipes of austenitic stainless steel. The primary difficulty in DMW joint manufacturing is in mitigating the significant disparity in material characteristics resulting from carbon migration and metallurgical alterations along the fusion interface between ferritic steel and austenitic stainless steel. The process of buttering entails the application of a compatible filler material onto the base metal before the deposition of the desired weld metal. The intermediate layer serves as a mediator, enhancing the metallurgical compatibility, diminishing the probability of fracture, and enhancing the overall integrity of the joint. Buttering is still a new research area with a wide scenario of scope in terms of development, which could revolutionize developing high-temperature. These long-term sustainable joints could serve under critical conditions like AUSC power plants and reduce CO2 emissions by increasing the overall efficiencies of the systems.

This study examines the welded joint between P91 steel and Incoloy 800HT using the activated tungsten inert gas (A-TIG) welding process. The focus is on analyzing the microstructure and evaluating the mechanical properties of joints made with different compositions of activating flux. Owing to the reversal of the Marangoni effect in which the conventional direction of molten metal flow in the weld pool is reversed due to the application of oxide-based fluxes, a complete depth of penetration of 8 mm was successfully achieved. Conducting mechanical tests, such as microhardness, tensile, and Charpy impact toughness tests, elucidates the behavior of the welded specimens under different loading conditions. The findings highlight the effects of grain size, dislocations, and the evolution of fine-sized precipitates in the high-temperature matrix. This study highlights the importance of choosing suitable flux compositions to achieve consistent penetration and dilution in the base metals. Insights into different failure modes and the influence of temperature on the tensile strength were evaluated. Beneficial mechanical properties of the joints (meeting the criteria of ISO and ASTM standards) were found: ultimate tensile strength of 585 ± 5 MPa, elongation 38 ± 2%, impact toughness of 96 ± 5 J, and maximum microhardness of 345 ± 5 HV.

Laser-induced graphene (LIG) has been emerging as a promising electrode material for supercapacitors due to its cost-effective and straightforward fabrication approach. However, LIG-based supercapacitors still face challenges with limited capacitance and stability. To overcome these limitations, in this work, we present a novel, cost-effective, and facile fabrication approach by integrating LIG materials with candle-soot nanoparticles. The composite electrode is fabricated by laser irradiation on a Kapton sheet to generate LIG material, followed by spray-coating with candle-soot nanoparticles and annealing. Materials characterization reveals that the annealing process enables a robust connection between the nanoparticles and the LIG materials and enhances nanoparticle graphitization. The prepared supercapacitor yields a maximum specific capacitance of 15.1 mF/cm2 at 0.1 mA/cm2, with a maximum energy density of 2.1 μWh/cm2 and a power density of 50 μW/cm2. Notably, the synergistic activity of candle soot and LIG surpasses the performances of previously reported LIG-based supercapacitors. Furthermore, the cyclic stability of the device demonstrates excellent capacitance retention of 80% and Coulombic efficiency of 100% over 10000 cycles.

The growth of zinc oxide nanowires (ZnO NWs) on metal-seeded substrates is crucial for photonics, electronics, and sensing applications. Traditionally, NWs are grown using seed sintering on rigid substrates at high-temperature. However, the rise of flexible electronics, which use substrates unable to withstand high temperatures, has shifted focus to metal-assisted synthesis methods that do not require high-temperature sintering. This method has gained increasing attention due to its compatibility with flexible substrates. This article focuses on understanding the underlying growth mechanisms and achieving controlled growth of ZnO NWs on metal seeded flexible substrates. Furthermore, a parametric analysis is carried out to elucidate the correlation among different growth conditions in the chemical bath deposition (CBD) technique. Through a meticulously planned experimental design, the study investigates the influence of different growth conditions on synthesis outcomes. This leads to the formulation of predictive models using advanced machine learning (ML) methods particularly, artificial neural network (ANN). Following validation and training, the ANN model exhibits a remarkable ability to predict synthesis outcomes, yielding R2 values of 0.92 for diameter and 0.96 for length of NWs. Notably, the highest aspect ratio (AR) of ∼24 is attained following the growth conditions: 25 mM precursor concentration, 60 min growth time, and a growth temperature of 95 °C. Additionally, this method of growing ZnO NWs on a metal-seeded substrate offers an alternative approach for fabricating nanodevices for various emerging applications.