As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

Photocatalysis is considered as one of the promising routes to solve the energy and environmental crises by utilizing solar energy. Graphitic carbon nitride (g-C3N4) has attracted worldwide attention due to its visible-light activity, facile synthesis from low-cost materials, chemical stability, and unique layered structure. However, the pure g-C3N4 photocatalyst still suffers from its low separation efficiency of photogenerated charge carriers, which results in unsatisfactory photocatalytic activity. Recently, g-C3N4-based heterostructures have become research hotspots for their greatly enhanced charge carrier separation efficiency and photocatalytic performance. According to the different transfer mechanisms of photogenerated charge carriers between g-C3N4 and the coupled components, the g-C3N4-based heterostructured photocatalysts can be divided into the following categories: g-C3N4-based conventional type II heterojunction, g-C3N4-based Z-scheme heterojunction, g-C3N4-based p–n heterojunction, g-C3N4/metal heterostructure, and g-C3N4/carbon heterostructure. This review summarizes the recent significant progress on the design of g-C3N4-based heterostructured photocatalysts and their special separation/transfer mechanisms of photogenerated charge carriers. Moreover, their applications in environmental and energy fields, e.g., water splitting, carbon dioxide reduction, and degradation of pollutants, are also reviewed. Finally, some concluding remarks and perspectives on the challenges and opportunities for exploring advanced g-C3N4-based heterostructured photocatalysts are presented.

g-C3N4-Based Heterostructured Photocatalysts

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Numerical Heat Transfer And Fluid Flow

Engineering photocatalytic materials for renewable energy generation and environmental decontamination has always been a very exciting prospect to counter the global energy demands and pollution challenges. Graphitic carbon nitride (g-C 3 N 4 ), a polymeric, metal-free semiconductor with a mild band gap (2.7 eV) has become hot-spot in various scientific exploits such as environmental pollution mitigation, energy generation and storage, organic synthesis, sensors, etc. These applications exploit the interesting properties of g-C 3 N 4 such as good visible light absorption, graphene-like structure, good thermal and chemical stability and photocatalytic properties. In this review we begin with an overview of the fundamental aspects of photocatalysis as a pollution remediation strategy. This is followed by an introduction to graphitic carbon nitride as a photocatalyst, preparation strategies and its properties. Subsequently, a comprehensive and critical discussion of the various most recent developments towards enhancing the visible light photocatalytic properties of g-C 3 N 4 for pollution alleviation, selected results and important photocatalytic degradation mechanisms, is given. Summary remarks and future perspective conclude the review.

Graphitic carbon nitride (g-C3N4) nanocomposites: A new and exciting generation of visible light driven photocatalysts for environmental pollution remediation

The effects of non-metallic inclusions in nucleating acicular ferrite in steels during cooling from a weld or cooling from an austenitic temperature are reviewed. The influence of the acicular ferrite (AF) structure on mechanical properties of steels such as strength and toughness is briefly mentioned. The different factors affecting the formation of acicular ferrite, such as the soluble content of alloying elements in steel, cooling rate from austenitizing temperature, austenite grain size and inclusion characteristics in steel, are discussed. The mechanisms of acicular ferrite formation on non-metallic inclusions, such as reduction of interfacial energy, mismatch strain between the inclusion and ferrite/austenite, thermal strains at the inclusions and changes in matrix composition near the inclusions are also discussed. Finally, the effects of inclusion characteristics, such as size, number and composition are described and their effectiveness in nucleating acicular ferrite is discussed.

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On the Role of Non-metallic Inclusions in the Nucleation of Acicular Ferrite in Steels

Considerable research has been conducted over recent decades on the role of non‑metallic inclusions and their link to the machinability of different steels. The present work reviews the mechanisms of steel fractures during different mechanical machining operations and the behavior of various non-metallic inclusions in a cutting zone. More specifically, the effects of composition, size, number and morphology of inclusions on machinability factors (such as cutting tool wear, power consumption, etc.) are discussed and summarized. Finally, some methods for modification of non-metallic inclusions in the liquid steel are considered to obtain a desired balance between mechanical properties and machinability of various steel grades.

/pdf/the-effect-of-different-non-metallic-inclusions-on-the-2ykxd573g7.pdf

The effect of different non-metallic inclusions on the machinability of steels

The use of thermodynamic data in describing calcium modification of aluminium oxide inclusions has been summarised and reviewed. The majority of the published Al-S equilibrium diagrams, based on the following reaction:3CaO+3S+2Al=3CaS+Al2O3, vary significantly due to different sources for thermodynamic data, especially for the activity of CaO and Al2O3. Using ThermoCalc, the activities of CaO and Al2O3 have been calculated and compared to the published data. Calculations in the present work pertaining to the molten range of the system are in good agreement with the most recently published experimental data of Fujisawa et al.Based on the assessed thermodynamic data and observed phenomena during calcium modification of inclusions in steel melts of moderate sulphur content, a model for alumina modification by calcium treatment has been developed. According to the model, the reactions progress by the following sequence until the activity of Al2O3 becomes so low that precipitation of CaS occurs:Al2O3⇒CA6⇒CA2⇒CA⇒CAx(liquid)

Thermodynamics and Kinetics of the Modification of Al2O3 Inclusions

A rigorous evaluation of the usefulness of some existing models for prediction of sulphide capacity and sulphur distribution for industrial slags at Ovako Steel AB has been carried out. The results show that the best agreement between calculated and analysed sulphur distributions is obtained by calculating the alumina activity in the slag from an expression suggested by Ohta and Suito, 26) then using these data to calculate the oxygen activity in the molten steel, and finally by applying the KTH model4-6) to calculate the sulphide capacity and sulphur distribution. Therefore, the conclusion is that the KTH model4-6) is a useful tool for predictions of sulphur distributions for ladle slags.

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Application of the Sulphide Capacity Concept on High-basicity Ladle Slags Used in Bearing-Steel Production

A three-phase model of a gas-stirred steel bath covered with a slag layer has been developed. Predicted steel surface velocities have been shown to be in at least five times greater agreement with ...

Pär Jönsson

Papers

On the Role of Non-metallic Inclusions in the Nucleation of Acicular Ferrite in Steels

The effect of different non-metallic inclusions on the machinability of steels

Thermodynamics and Kinetics of the Modification of Al2O3 Inclusions

Application of the Sulphide Capacity Concept on High-basicity Ladle Slags Used in Bearing-Steel Production

Modeling of Fluid Flow Conditions around the Slag/Metal Interface in a Gas-stirred Ladle