Direct pyrolysis and ultrasound assisted preparation of N, S co-doped graphene/Fe3C nanocomposite as an efficient electrocatalyst for oxygen reduction and oxygen evolution reactions

Bifunctional electrocatalysts to enable efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential for fabricating high performance metal–air batteries and fuel cells. Here, a defect rich nitrogen and sulfur co-doped graphene/iron carbide (NS-GR/Fe3C) nanocomposite as an electrocatalyst for ORR and OER is demonstrated. An ink of NS-GR/Fe3C is developed by homogeneously dispersing the catalyst in a Nafion containing solvent mixture using an ultrasonication bath (Model-DC150H; power − 150 W; frequency − 40 kHz). The ultrasonically prepared ink is used for preparing the electrode for electrochemical studies. In the case of ORR, the positive half-wave potential displayed by NS-GR/Fe3C is 0.859 V (vs. RHE) and for the OER, onset potential is 1.489 V (vs. RHE) with enhanced current density. The optimized NS–GR/Fe3C electrode exhibited excellent ORR/OER bifunctional activities, high methanol tolerance and excellent long-term cycling stability in an alkaline medium. The observed onset potential for NS–GR/Fe3C electrocatalyst is comparable with the commercial noble metal catalyst, thereby revealing one of the best low-cost alternative air–cathode catalysts for the energy conversion and storage application

Efficiency of Organic Draw Solutions in a Forward Osmosis Process Using Nano-filtration Flat Sheet Membrane

The aim of this study is to investigate the performance of specific organic osmotic agents, namely, Sucrose draw solution and Glucose draw solution against deionized water in a Forward Osmosis (FO) process using NF flat sheet membrane. The key parameters affecting the FO process studied were: temperature, flow rates of osmotic agent and feed water, and concentration of osmotic agent. The experimental results showed that increasing the concentration of osmotic agents yield lower water flux, recovery percentage and permeability, along with an apparent increase in the specific energy consumption. Although the findings indicated superior performance of Glucose over Sucrose as a better osmotic agent, it has to be emphasized that both organics were ineffective draw solutions against deionized water for the Nano-filtration (TFC-SR2) membrane used in this study and the given operating parameters

Fabrication of Spiny-like Spherical Copper Metal–Organic Frameworks for the Microextraction of Arsenic(III) from Water and Food Samples before ICP-MS Detection

Spiny-like spherical copper metal–organic frameworks (SSC-MOFs) were prepared and characterized via SEM, TEM, EDS, XRD, FTIR and the BET surface area. The fabricated SSC-MOFs were applied to develop a procedure for the microextraction of trace arsenic(III) for preconcentration. The results show that a copper- and imidazole-derived metal–organic framework was formed in a sphere with a spiny surface and a surface area of 120.7 m2/g. The TEM confirmed the perforated network structures of the SSC-MOFs, which were prepared at room temperature. The surface functional groups were found to contain NH and C=N groups. The XRD analysis confirmed the crystalline structure of the prepared SSC-MOFs. The application for the process of microextracting the arsenic(III) for preconcentration was achieved with superior efficiency. The optimum conditions for the recovery of the arsenic(III) were a pH of 7 and the use of a sample volume up to 40 mL. The developed SSC-MOF-derived microextraction process has an LOD of 0.554 µg·L−1 and an LOQ of 1.66 µg·L−10. The developed SSC-MOF-derived microextraction process was applied for the accurate preconcentration of arsenic(III) from real samples, including food and water, with the promised performance efficiency

Synthesis and Characterization of Efficient ZnO/g-C3N4 Nanocomposites Photocatalyst for Photocatalytic Degradation of Methylene Blue

We examine the photocatalytic activity (PCA) of ZnO/graphitic carbon nitride g-C3N4 (g-CN) composite material for methylene blue (MB) degradation under visible-light irradiation (VLI). The polymeric g-CN materials were fabricated by the pyrolysis of urea and thiourea. More importantly, ZnO/g-CN nanostructured composites were fabricated by adding the different mounts (60, 65, 70, and 75 wt.%) of g-CN into ZnO via the simple hydrothermal process. Among fabricated composites, the 75% ZnO/g-CN nanocomposites displayed a superior PCA for MB degradation, which were ~three-fold an enhancement over the pure ZnO nanoparticles. The fabricated materials have been evaluated by X-ray diffraction (XRD), UV-Vis, Fourier transform infrared (FT-IR) spectroscopy, and electron microscopy. More importantly, the photodegradation of MB could get 98% in ZnO/g-CN could be credited to efficient separation of photo-induced charge carriers between ZnO and g-CN. Also, the recycling efficiency of the as-prepared composites was studied for multiple cycles, which shows that the photocatalysts are stable and suitable to carry out photocatalytic degradation in the logistic mode. Additionally, the probable photocatalytic mechanism has also discussed. The synthetic procedure of ZnO/g-CN based materials can be used in numerous fields such as environmental and in energy storage applications

Synthesis, Characterization and Single Crystal X-ray Diffraction Analysis of Fused Triazolo/Thiadiazole Clubbed with Indole Scaffold

The present synthetic strategy involves the synthesis of indolyl-triazolo-thiadiazole heterocyclic ring systems 8–13 from the condensation of 4-amino-5-(1H-indol-2-yl)-3H-1,2,4-triazole-3-thione 1 with the aromatic carboxylic acid derivatives 2–7 in presence of POCl3 for 1 h. All compounds were obtained in very good yields and have been well-characterized using spectroscopic techniques. Exclusively, good quality crystals from the target organic hybrid 8-(1H-indol-2-yl)-5-(p-tolyl)-[1,2,4]triazolo [3,4-b][1,3,4]thiadiazole 9 were obtained and found suitable for X-ray single crystal diffraction measurement, which is used to confirm and analyze the molecular and supramolecular structure aspects of 9. The solid-state structure of the synthesized molecule 9 agrees very well with other characterizations. The packing of 9 is dominated by the N…H, S…H, C…C and S…C non-covalent interactions, which agree with the Hirshfeld surface analysis. The percentages of these contacts are calculated to be 20.3%, 5.4%, 9.4% and 4.3%, respectively.peerReviewe

Mechanical and Microstructural Properties of Ultra-High Performance Concrete with Lightweight Aggregates

Although ultra-high-performance concrete (UHPC) presents superior mechanical properties and durability compared to conventional concrete; its spalling resistance to elevated temperatures is much lower compared to conventional concrete due to the high compactness and absence of capillary pores. This paper investigated the influence of lightweight aggregate (LWA) on the strength properties and microstructure of UHPC to enhance its resistance to elevated temperatures. UHPC specimens prepared with LWA as a partial replacement of silica sand were produced. The study evaluated the compressive and flexural strengths, failure mode, mass loss, and microstructure of the specimens, using SEM. The results showed that the compressive strength of the UHPC specimen was reduced with increasing the content of LWA at ambient temperature, but the compressive strength of the UHPC specimens prepared with LWA improved when exposed to elevated temperatures. The replacement of 10% of the silica sand with LWA led to an increase in the compressive strength from 100 MPa to 110 MPa after exposure to 200 °C; however, the flexural strength decreased from 23.6 MPa to 18.3 MPa. On the contrary, the flexural strength of UHPC increased with the inclusion of LWA at an ambient temperature but reduced with high-temperature exposure. The failure mode of UHPC was not significantly affected by the variation in LWA content and temperature. In addition, the SEM result confirms that LWA is an effective internal curing material for enhancing the microstructure and compressive strength of UHP

Manufacturing of carbon fiber reinforced thermoplastics and its recovery of carbon fiber: A review

Polymer matrix composites are excellent materials for a variety of industrial applications. They have superior mechanical, thermal and electrical properties, making them preferable to traditional materials such as metal. To make polymer matrix composite materials, thermosetting, elastomers and thermoplastic polymers are mainly the three types of polymers that can be utilized as matrices. In comparison to thermosetting and elastomers polymers, carbon fiber reinforced thermoplastic (CFRTP), is the subject of this research, are gaining popularity in many industrial sectors due to its recyclability, simplicity of processing, good characteristics, flexibility, and less production time. This review covers conventional and state-of-the-art manufacturing techniques of CFRTP. Moreover, the potential and existing of CFRTP's application as well as the techniques of carbon fiber recovery and recycling methods of such materials were also examined. Overall, this study considers the research and development on manufacturing CFRTP and recycling techniques of polymer composites to recover carbon fiber materials