8369 research outputs found
Sort by
2D Boron Nanosheets for Photo- and Electrocatalytic Applications
No full textBorophene, a new member of the two-dimensional (2D) materials family, has attracted researchers since its first experimental synthesis. Borophene (2D boron nanosheet) differs significantly from other 2D materials due to its low energy requirement to form defects, anisotropy, electron-deficient structure, multicentered bonding, etc. The uniqueness in properties of borophene compared to other 2D materials makes it suitable for applications in catalysis, sensing, energy storage, etc. The present review summarizes the development of borophene synthesis and emphasizes its applications in catalysis. Different synthesis approaches and their advantages and limitations are discussed briefly as substantial reviews are available on borophene synthesis. The applications of pristine borophene and their modified heterostructure in the field of catalysis were thoroughly reviewed, focusing on the electrocatalysis applications. Finally, the review discussed the future scope of borophene in designing new materials as well as opportunities to be utilized for other application fields. Since there is a lack of a good number of experimental reports on the applications of borophene and its derivatives, a huge opportunity is waiting for the researchers to explore the unknown world of borophene. In this regard, this review will help the researchers in an excellent manner. Two-dimensional boron nanosheets (borophene) exhibit promising catalytic properties for energy and environmental applications. This review summarizes the theoretical and experimental applicability of borophene and its heterostructures towards efficient hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), CO2 reduction reaction (CO2RR), N2 reduction reaction (N2RR), photocatalytic degradation, etc. imag
Achieving Exceptional Strength-Ductility Synergy via Nano-precipitation Hardening in a Ni-Fe-Cr-Co-Al Alloy
No full textIn the present work, a Ni-Fe-Co-Cr-Al-based medium entropy alloy (MEA) was developed by exploring the vast compositional space provided by the birth of high-entropy alloys (HEAs). The composition was designed via the CALPHAD approach and the designed alloy was melted through the vacuum induction melting (VIM) technique using commercial elements. Post-homogenization treatment, the material was cold deformed up to 73 pct reduction in thickness. This cold-rolled material was annealed with varying duration at a fixed temperature of 900 degrees C for a better understanding of the static recrystallization mechanism. The systematic static recrystallization study was performed to design a heterogeneous grain distribution within the matrix via partial recrystallization. Post-establishment of the annealing schedule, ageing treatment at 600 degrees C for 5 hours was carried out. The room temperature mechanical properties were evaluated for selected ageing conditions. An excellent strength of > 950 MPa accompanied by an appreciable ductility of 60 pct was obtained for the fully recrystallized and aged specimen. The obtained results surpassed the strength-ductility synergy exhibited by various solid solution-strengthened (SS) Ni-based superalloys and heterogeneous HEAs and hold the potential to be explored for elevated temperature applications. A systematic study has also been carried out to estimate the contribution of various strengthening factors in the designed alloy and the predicted results corroborate well with the experimental findings. (C) The Minerals, Metals & Materials Society and ASM International 2024
Down-conversion luminescence nanocomposites based on nitrogen-doped carbon quantum dots@bioplastic for applications in optical displays, LEDs and UVC tubes
No full textCarbon quantum dots (CQDs)-based composites as luminous down-conversion materials are becoming more popular due to several advantages such as steady fluorescence, ease of functionalization, tailoring of emission in the visible range, and so on. We report an inexpensive and environmentally sustainable synthesis of fluorescent nitrogen doped-CQDs produced from Cissus quadrangularis, a low-cost plant precursor with therapeutic value. The morphological, structural, and physicochemical features of the material were carefully investigated. Under UV stimulation (365 nm), almost spherical-shaped N-CQDs with an average diameter of 5.1 nm were discovered to generate yellow-green fluorescence, have excellent photostability, strong water solubility, with a quantum yield of up to 5 %. Furthermore, as a solid-phase dispersion matrix for CQDs, ecologically friendly, biodegradable bioplastic is appealing. The down-conversion of solid-state fluorescence of LEDs and UVC tubes was demonstrated by creating a nanocomposite by inserting N-CQDs into the solid matrix of a wheat starch-based bioplastic. Furthermore, employing constructed quantum dot-based optical displays, down-converted LEDs, and UVC tubes, the impacts of varied CQD concentrations and pH sensitivity were examined
Biodiesel Production From High-free Fatty Acids Podocarpus falcatus Oil and Identification of Fatty Acid Methyl Esters by FT-IR, NMR (1H and 13C) and GC/MS Studies
No full textBiodiesel occupies a prominent place as the alternative fuel to fossil diesel owing to socio-economic and environmental factors. In this present study, Podocarpus falcatus oil (PFO), having undergone a storage effect, was converted into biodiesel. PFO had a high fatty acid content (FFA = 8.19%). For this reason, a two-step transesterification procedure was developed to convert this high-free fatty acid (FFA) oils into their corresponding monoesters. In the initial step, an acid-catalyzed esterification was employed to lower the FFA content of the oil to below 2%. Subsequently, a second step involving an alkaline catalysis transesterification process was used to convert the product obtained in the first step into monoesters and glycerol. The methyl esters obtained were analyzed using nuclear magnetic resonance (H-1, C-13 NMR), Fourier transform infrared spectroscopy (FT-IR), Thermal gravimetric analysis (TGA), carbon, hydrogen, nitrogen, and sulfur (CHNS), and Gas chromatography-mass spectrometry (GC-MS) analysis. The identity FAME were Hexadecanoic acid, methyl ester (C16:0), 9,11-Octadecadienoic acid, methyl ester, (E, E)- (C18:0), 6-Octadecenoic acid, methyl ester, (Z)- (C18:2), Methyl stearate (C18:1), Methyl (Z)-5,11,14,17-eicosatetraenoate (C20:5), 11,14-Eicosadienoic acid, methyl ester (C20:3), 11-Eicosenoic acid, methyl ester (C20:2). The study examined the thermal stability of synthesized biodiesel, revealing it remained stable up to 189 degrees C. Furthermore, the physicochemical properties of biodiesel were validated using ASTM6751 standards
Flotation performance and kinetics study of low-grade limestone with fatty acids-rich oilseed residue as green collector
No full textWith the depletion of mineral resources and increasing environmental protection requirements, researching and developing efficient and environmentally friendly flotation agents is crucial for the comprehensive utilization of mineral resources. Low-grade limestone deposits with high impurities pose a challenge for efficient processing and direct industrial applications. This study explores a novel and sustainable approach to address this challenge by evaluating the prospective use of a fatty-acid-rich oilseed residue as a bio-collector (referred to as collector SSFA ) to recover carbonates from a low-grade limestone, characterized by high acid insolubles content and its influence on the kinetics of the flotation process. The bio-collector ( SSFA ) outperformed the conventional collector sodium oleate (referred to as SSO ) by significantly increasing the recovery of total carbonates (TC) while simultaneously reducing acid insolubles (AI). A low-grade limestone feed containing 78.40 % TC and 20.90 % AI was upgraded through both mechanical and column flotation techniques. Mechanical flotation yielded a product with 92.9 % TC, 93.48 % TC recovery, 4.0 % AI, and 77.58 % yield at an SSFA dosage of 0.87 kg/t. Column flotation, at the same dosage, yielded a product with slightly higher TC content (94.20 %), lower TC recovery (91.02 %), similar AI content (4.07 %), and slightly lower yield (74.68 %). The kinetics of the flotation process indicated that the limestone sample exhibited fast-floating behavior, attributed to the enhanced selectivity of the SSFA collector. The bio-collector SSFA stands out as a promising and sustainable alternative to conventional collectors for large-scale low-grade limestone flotation due to its remarkable ability to selectively recover total carbonates while minimizing acid insoluble
Stretch Flangeability of Low Carbon Micro-alloyed Ferrite-Pearlite and Ferrite-Bainite Steel
No full textThe application of low carbon micro-alloyed steel sheets in chassis and frame parts of automobiles demands high formability during hot or cold forming operations to produce various intricate shapes. In view of the forming applications, stretch flangeability is considered as one of the most important critical parameters for these steel grades. The stretch-flangeability of micro-alloyed steels, with three different types of microstructure consisting of mainly single-phase ferrite, ferrite-pearlite and ferrite-bainite micro-constituents, is evaluated in this investigation based on hole expansion ratio (HER). The desired microstructures of the low carbon steels micro-alloyed with Nb, Nb-V and Nb-V-Ti steels were obtained at three different coiling temperatures by systematically varying the plant operating process parameters. While Micro-alloying elements largely affect the mechanical strength and ductility of the steel, its direct impact on HER value and fracture behavior are not correlated. The correlation of microstructure with tensile strength and ductility have been attempted for the studied low carbon micro-alloyed steels and described in this paper. It is observed that single-phase steel consisting of soft ferritic matrix as well as steel with 5 to 15 pct pearlite uniformly distributed in ferrite matrix has better stretch flangeability and strength to hole expansion ratio correlation in comparison to ferrite-bainite steel
Mechanistic investigation of hydrogen generation from water and magnesium catalyst reaction: Advanced reactive molecular dynamics simulation
No full textMagnesium is an effective catalyst for producing hydrogen through thermochemical water splitting. However, the slow reaction between Mg and water prevents this catalyst from being commercially useful. In this study, reactive MD simulations with accurate force fields and reactive potential energy surfaces are used to comprehend the slow-kinetics of the Mg-water reaction. At room temperature, water is split when it interacts with Mg nanoparticles and forms a Mg–H bond. Furthermore, at temperatures above 1200 K, Mg–H bonds begin to dissociate, resulting in the generation of hydrogen radicals from the Mg–H bond. The percentage of H–H bonds is almost zero until the reaction pathway reaches temperature 2000K, after which H radicals combine to form hydrogen gas. The analysis of temperature dependent data reveals that oxygen and hydrogen atoms combine with Mg elements to form massive stable linear and branched chains, resulting in slow Mg-water reaction kinetics for hydrogen production. Therefore, current studies utilizing reactive molecular dynamics can provide a means of improving the kinetics of the Mg-water reaction
Mineralogical compositions and distributions of trace and rare earth elements in Eocene carbonaceous sediments of Western India: implications for paleoenvironment during peat accumulation
No full textThe mineralogical compositions and distributions of trace and rare earth elements (REEs) in carbonaceous sediments provide valuable insights into the paleoenvironmental conditions during peat formation. Given the increasing demand for REEs in modern technologies, understanding their occurrence and economic potential is critical. However, the precise mineral hosts of trace and REEs in these sediments and their implications for the paleoenvironment during the Eocene epoch in India remain less explored. Therefore, this study examines Eocene carbonaceous sediments from the Saurashtra Basin in western India to uncover mineralogical controls on trace and REEs distribution and to infer paleoenvironmental conditions during peat accumulation. A total of 15 samples were collected from two mines (Surkha-lignite and Khadsaliya-shale). X-ray Diffraction (XRD), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and Inductively Coupled Plasma Optical Emission Spectroscopy ICP-OES analysis were utilized to know the mineralogy, REEs, and trace elements distribution. The total REE concentrations in shale and lignite were low, while for in shale (avg. 195.89 ppm) was relatively higher than lignite (avg. 177.32 ppm), with cerium (Ce) being the most abundant element in both rock types. The concentrations of REEs in the studied lignite samples followed the order Ce>Nd>La>Y>Sc>Gd>Pr>Sm>Dy>Er>Yb>Eu>Ho>Tb>Tm>Lu, while in shale samples the order was Ce>Y>Nd>La>Sc>Gd>Pr>Dy>Sm>Er>Yb>Eu>Ho>Tb>Tm>Lu. The REE concentrations in the studied samples are notably lower than global averages, yet the presence of critical REEs suggests potential economic value. The outlook coefficient (Coutl) values ranging from 0.82 to 2.59 indicate promising REE sources within the basin. XRD studies revealed the presence of various mineral phases in the analyzed samples, including quartz, kaolinite, dickite, zeolite, coesite, anatase, pyrite, gypsum, calcite, biotite, clinopyroxene, montmorillonite, and magnetite. The dominance of kaolinite and quartz indicates that felsic rocks are the primary source of inorganic sediments in the paleomire. The major and trace element ratios suggest that the deposition of the studied lignite and shales occurred under conditions of increased oxygen deficiency, ranging from dysoxic-suboxic to anoxic environments. The transition from lake water to brackish water conditions was also evident with limited terrestrial influx in the basin. Furthermore, the Ce anomalies observed in the samples, ranging from 3.51 to 5.05 in shales and 3.92 to 4.13 in lignite, suggest shales were formed under oxidizing conditions and lignites in more restricted, potentially freshwater environments
Petrology and association of rare earth elements in magmatically altered high‑ash coal of Indian origin
No full textThe extraction of valuables from waste has gained momentum. Thermal influence alters both the organic and inorganic
components of coal. Insufficient knowledge on the association of rare earth elements (REEs) with the parent matrix of thermally altered high-ash coals (63% ash) limits the potential for such coals being utilized for isolation of valuables. In this study, we analyzed the distribution and occurrence modes of REEs within a magmatically altered high-ash coal via nine-step sequential extraction, combining Tessier and BCR methods. The total concentration of REEs in the coal sample, on whole coal basis, was found to be 820 ppm, which is significantly higher than the world average. Major mineral oxides were deduced to be those of Si, Fe, Al, Ca, Mg, and Ti. Sequential extraction confirmed that about 66% of HREE and 25% of LREE were included in the residual fraction. LREEs were concluded to be primarily in ionic form, whereas HREEs were speculated to be associated with the TiO2 phase. XRD analyses showed that thermal alteration affected the dolomite phase specifically, which selectively got removed where carbonate-bound elements were assessed. Petrographic analysis supported the magmatic influence and demonstrated the presence of mosaic structures and pores containing unfused vitrinite, with a reflectance value of 3.6. To summarize, the present study pertaining to delineation of association of valuables in high-ash heat-altered coals from an Eastern coalfield in India can potentially open up new avenues for utilizing such coals, which are otherwise considered waste
In-process monitoring of the ultraprecision machining process with convolution neural networks
No full textIn-process monitoring and quality control are the most critical aspects of the manufacturing industry, especially in ultra-precision machining (UPM) at an industrial scale. However, in-process ensuring product quality has been difficult, as any subtle change in the process influences the UPM process dynamics and the process outcome. In order to meet the increasingly soaring demand for precision components, intelligent monitoring of the machining process is essentially important and much needed. Capturing complex signal patterns through conventional signal processing for the UPM process is often challenging due to the comparably high noise levels in the industrial environment. Signals obtained during UPM are inherent transients and non-stationary, necessitating extensive and accurate features for classification. Accurate detection of anomalies may allow for quick corrective actions, reducing the degree of damage. Earlier research revealed multi-sensor analysis, which yields richer signal feature information, but the unavoidable sensor failure in conjunction with heterogeneous sensing made it challenging. In order to address the challenges, this paper investigates the feasibility of convolution neural network (CNN) for classifying abnormal and normal machining in the UPM process. The vibrational signals obtained from B&J 4533-B accelerometer during diamond turning are transformed into time-frequency-based log-spectrogram images. These images are classified using CNN, and the results show that a proposed convolutional neural network algorithm has demonstrated an accuracy of 85.92% in classifying images and thus the corresponding in-process machining status