Thermoelectric (TE) materials are of great interest to many researchers because they directly convert electric and thermal energy in a solid state. Various materials such as chalcogenides, ...clathrates, skutterudites, eutectic alloys, and intermetallic alloys have been explored for TE applications. The Ga-Sn-Te system exhibits promising potential as an alternative to the lead telluride (PbTe) based alloys, which are harmful to environments because of Pb toxicity. Therefore, in this study, thermodynamic optimization and critical evaluation of binary Ga-Sn, binary Sn-Te, and ternary Ga-Sn-Te systems have been carried out over the whole composition range from room temperature to above liquidus temperature using the CALPHAD method. It is observed that Sn-Te and Ga-Te liquids show the strong negative deviation from the ideal solution behavior. In contrast, the Ga-Sn liquid solution has a positive mixing enthalpy. These different thermodynamic properties of liquid solution were explicitly described using Modified Quasichemical Model (MQM) in the pair approximation. The asymmetry of ternary liquid solution in the Ga-Sn-Te system was considered by adopting the toop-like interpolation method based on the intrinsic property of each binary. The solid phase of SnTe was optimized using Compound Energy Formalism (CEF) to explain the high temperature homogeneity range, whereas solid solution, Body-Centered Tetragonal (BCT) was optimized using a regular solution model. Thermodynamic properties and phase diagram in the Ga-Sn-Te and its sub-systems were reproduced successfully by the optimized model parameters. Using the developed database, we also suggested several ternary eutectic compositions for designing TE alloy with improved properties.
We report the fluorination of electrically insulating hexagonal boron nitride (h-BN) and the subsequent modification of its electronic band structure to a wide bandgap semiconductor via introduction ...of defect levels. The electrophilic nature of fluorine causes changes in the charge distribution around neighboring nitrogen atoms in h-BN, leading to room temperature weak ferromagnetism. The observations are further supported by theoretical calculations considering various possible configurations of fluorinated h-BN structure and their energy states. This unconventional magnetic semiconductor material could spur studies of stable two-dimensional magnetic semiconductors. Although the high thermal and chemical stability of h-BN have found a variety of uses, this chemical functionalization approach expands its functionality to electronic and magnetic devices.
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Magnetic materials enjoy an envious position in the area of data storage, electronics, and even in biomedical field. This review provides an overview of low-dimensional magnetism in ...graphene, h-BN, and carbon nitrides, which originates from defects like vacancy, adatom, doping, and dangling bonds. In transition metal dichalcogenides, a tunable magnetism comes from doping, strain, and vacancy/defects, and these materials offer spintronics, as well as photoelectronic potentials, since they have an additional degree of freedom called valley state (e.g. MoS2). Strain- and layer-dependent magnetic ordering has been observed in layered compounds like CrXTe3, CrI3, and trisulfides. The magnetism in 2D oxides like MoO3, Ni(OH)2,and perovskites are also interesting as they are potential candidates for next-generation devices having faster processing and large data storage capacity. Quasi 2D magnetism in MXene and in atomically thin materials supported on 3D materials will also be discussed. Finally, some of the challenges related to the control of defects and imperfections in 2D lattice, promising approaches to overcome them will be covered.
Here we investigated the fluorination of graphene oxide nanoribbons (GONRs) using H2 and F2 gases at low temperature, below 200 °C, with the purpose of elucidating their structure and predicting a ...fluorination mechanism. The importance of this study is the understanding of how fluorine functional groups are incorporated in complex structures, such as GONRs, as a function of temperature. The insight provided herein can potentially help engineer application-oriented materials for several research and industrial sectors. Direct 13C pulse magic angle spinning (MAS) nuclear magnetic resonance (NMR) confirmed the presence of epoxy, hydroxyl, ester and ketone carbonyl, tertiary alkyl fluorides, as well as graphitic sp2-hybridized carbon. Moreover, 19F–13C cross-polarization MAS NMR with 1H and 19F decoupling confirmed the presence of secondary alkyl fluoride (CF2) groups in the fluorinated graphene oxide nanoribbon (FGONR) structures fluorinated above 50 °C. First-principles density functional theory calculations gained insight into the atomic arrangement of the most dominant chemical groups. The fluorinated GONRs present atomic fluorine percentages in the range of 6–35. Interestingly, the FGONRs synthesized up to 100 °C, with 6–19% of atomic fluorine, exhibit colloidal similar stability in aqueous environments when compared to GONRs. This colloidal stability is important because it is not common for materials with up to 19% fluorine to have a high degree of hydrophilicity.
Ciprofloxacin, a pharmaceutically active compound, is present as a micropollutant in wastewater, which cannot be removed by conventional techniques due to its recalcitrant nature. Therefore, in the ...present study, the photocatalytic degradation of this bio-toxic compound was demonstrated using a three-dimensional sulfur-doped graphitic-carbon nitride/zinc oxide hybrid, with enriched oxygen vacancies. The influence of various water matrices and experimental conditions on the ciprofloxacin degradation was optimized. The hybrid material showed 98.8% and 75.8% degradation efficiency under optimum experimental conditions (i.e., catalyst dose: 1 g/L; pH: 5; initial ciprofloxacin concentration: 20 mg/L; temperature: 27 °C) under ultraviolet (UV) and visible light, respectively. A neural-network-based multivariate approach was used to predict a significant model considering the experimental conditions that showed adequate statistical significance (R2: 0.992 and F-value: 8707.1). The relative significance of the experimental conditions was assessed, suggesting that the initial ciprofloxacin concentration has a more significant effect on the degradation efficiency than the other factors. The rate kinetics and reaction mechanisms for ciprofloxacin degradation were demonstrated, and the driving radicals involved were identified. A higher rate of reaction was found under UV irradiation (0.01702 min−1) than under visible light (0.00802 min−1). Superoxide radicals were identified as the main driving radicals, which caused substantial photocatalytic reactions among the hybrid and ciprofloxacin molecules. Microscopic and macroscopic analyses of the used hybrid were conducted, which confirmed the presence of higher defect concentrations, crystallinity, and interlinked stacked structure in the hybrid. Hence, the 3D hybrid can be efficiently used and reused for ciprofloxacin degradation. This advanced photocatalytic system can be widely used to remediate emerging contaminants in wastewater treatment.
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•The hybrid degraded ciprofloxacin up to 75.8% and 98.8% under visible and UV light.•Superoxide radicals were identified as main driving radicals.•Neural network based prediction model (R2: 0.992; F-value: 8707.1) for degradation.•Surface defects were almost similar for pristine and used hybrid (3D S–C3N4/ZnO).•Inductively coupled plasma-mass spectroscopy showed no metal ions in treated water.
Effect of manganese (Mn) addition (0.0, 1.0, 2.0 and 3 wt%) on the microstructural morphology, hardness, tensile properties and fracture behaviour of the gravity cast eutectic Al–12.6Si alloy has ...been studied through XRD analysis, chemical analysis, optical metallography, FESEM analysis, energy dispersive spectroscopy analysis, hardness test, tensile test and quantitative phase analysis. As-cast Al–12.6Si–0.0Mn alloy has a non-uniformly distributed coarser and irregular shape primary and eutectic silicon particles inside the α-Al phase, and both the Si phase have very sharp corners. Whereas, the 1 wt% Mn added alloy has uniformly distributed fine eutectic and primary Si particles with blunt corners. Further, the addition of 1.0 wt% Mn forms very few (0.26 vol %) irregular shape Al
15
(MnFe)
3
Si
2
intermetallic phase within the α-Al phase and eutectic Si phase. But, 2.0 wt% and 3 wt% Mn added alloy has an irregular shape coarse plate-like Al
15
(MnFe)
3
Si
2
intermetallic phase besides the primary and eutectic Si phase. The bulk hardness of the Al–12.6Si alloy is increased with an increase in Mn concentration as the harder Al
15
(MnFe)
3
Si
2
intermetallic phase forms and both the Si phase morphology modify. The microhardness of the constituent phases also varies with the change in Mn concentration in the alloy. The Mn addition improved the ultimate tensile strength, yield strength, and elongation (%) of the alloy. However, fractographs reveal that the brittle mode of fracture has been increased due to the presence of a higher volume of brittle Al
15
(MnFe)
3
Si
2
intermetallic in 2.0 and 3.0% Mn alloy. On the other hand, the amount of brittle and cleavage fracture of Si particles decreased, and ductile fracture with dimples formation increased in 1.0 wt%Mn added alloy.
Graphic Abstract
Effective nitrogen removal in wastewater treatment is crucial for environmental preservation, and recent research has focused on biofilm reactors, particularly examining the simultaneous ...nitrification and denitrification (SND) and simultaneous partial nitrification, anammox, and denitrification (SNAD) pathways. While these pathways show promise, challenges persist due to complex microbial interactions and process stability concerns. This study underscores the importance of addressing these challenges to maximize the potential of SND and SNAD processes, with a specific focus on the transformative role of 3D printed carriers. These carriers offer customization, tailored microenvironments, increased surface area, and superior biomass retention capabilities, presenting solutions to overcome the limitations of conventional carriers. By applying 3D printed carriers in wastewater treatment processes, the efficiency of nitrogen removal can be enhanced, leading to a sustainable and environmentally friendly approach. This review provides a comprehensive perspective on the potential of 3D printed carriers in addressing challenges associated with SND and SNAD, highlighting their significance in the evolving landscape of wastewater treatment.
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•MBBR performance was evaluated with emphasis on carrier modifications.•Critical operational parameters influencing SND and SNAD were evaluated.•Role of 3D printed bio-carriers was explored in nitrogen removal pathways.•Enhanced properties of 3D printed carriers reduce the startup period of the reactor.
Carbon nanotubes can be chemically modified by attaching various functionalities to their surfaces, although harsh chemical treatments can lead to their break-up into graphene nanostructures. On the ...other hand, direct coupling between functionalities bound on individual nanotubes could lead to, as yet unexplored, spontaneous chemical reactions. Here we report an ambient mechano-chemical reaction between two varieties of nanotubes, carrying predominantly carboxyl and hydroxyl functionalities, respectively, facilitated by simple mechanical grinding of the reactants. The purely solid-state reaction between the chemically differentiated nanotube species produces condensation products and unzipping of nanotubes due to local energy release, as confirmed by spectroscopic measurements, thermal analysis and molecular dynamic simulations.
Optimized designing of highly active electrocatalysts has been regarded as a critical point to the development of portable fuel cell systems with high power density. Here we report a facile and ...cost-effective strategy to synthesis of ultrafine Pd nanoparticles (NPs) supported on N and S dual-doped graphene (NS-G) nanosheets as multifunctional electrocatalysts for both direct formic acid fuel cell and direct methanol fuel cell. The incorporation of N and S atoms into graphene frameworks is achieved by a thermal treatment process, followed by the controlled growth of Pd NPs via a solvothermal approach. Owning to the unique structural features as well as the strong synergistic effects, the resulting Pd/NS-G hybrid exhibits outstanding electrocatalytic performance toward both formic acid and methanol electro-oxidation, such as higher anodic peak current densities and more exceptional catalytic stability than those of Pd/Vulcan XC-72R and Pd/undoped graphene catalysts. These findings open up new possibility in the construction of advanced Pd-based catalysts, which is conducive to solving the current bottlenecks of fuel cell technologies.
Ciprofloxacin is a pharmaceutically active compound which belongs to a class of micropollutants that cannot be removed using conventional water treatment systems. In this study, photocatalytic ...degradation using materials with high surface area and active sites was proposed to remove such contaminants. We demonstrated an easily scalable and simple synthesis route to prepare a 3D porous sulfur-doped g-C3N4/ZnO hybrid material, and the preparation process parameters were optimized using response surface methodology targeting Ciprofloxacin degradation. The hybrid material removed up to 98% of the bio-toxic Ciprofloxacin from synthetic water. The porous, defect engineered, thermally stable, and chemically interconnected hybrid material presented an 18 and 38% improved degradation efficiency compared to ZnO and sulfur-doped g-C3N4 (or S–C3N4), respectively. Based on our experimental results, an empirical relation correlating synthesis process parameters and degradation efficiency was developed using face-centered central composite design (FCCD) and response surface methodology (RSM). The current model can be used to design catalytic materials for removing bio-toxic and other micropollutants from water.
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•Facile synthesis of atomically-thin S–C3N4/ZnO hybrid degrading Ciprofloxacin.•The FCCD conjoined with RSM was used to optimize the synthesis process parameters.•Hybrid consists of interlinked 2D S–C3N4 sheets and 3D ZnO nanoplates.•Interaction between 2D S–C3N4 sheets and 3D ZnO nanoplates causes surface defects.•Hybrid has degraded the Ciprofloxacin up to 98.80% and mineralized it up to 98.32%.
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