Search Results (4,460)

A graphene sample (EGr) was obtained in a single-step synthesis by electrochemical exfoliation of graphite rods. A combination of 0.05 M ammonium sulfate and 0.05 M ammonium thiocyanate was employed, leading to a graphene sample composed of few-layer, multi-layer and graphene oxide flakes. Due to the mild exfoliation conditions, large sheets with linear sizes in the range of tens to hundreds of micrometers were produced. The LSV technique gave information about the effect of catechol concentration on the electrochemical signal of bare and graphene-modified electrodes. Based on the resulting calibration plots, the corresponding analytical parameters (linear range, sensitivity, limit of quantification and limit of detection) were calculated for each electrode. In the case of the EGr/GC electrode the linear range was from 6 × 10⁻⁷ to 1 × 10⁻⁴ M catechol. The detection limit was low (1.82 × 10⁻⁷ M) while the quantification limit was 6 × 10⁻⁷ M. The sensitivity was five times higher than that corresponding to bare GC, proving the excellent electro-catalytic properties of the graphene-modified electrode. The practical applicability of the graphene-modified electrode was tested in tap water, obtaining an excellent recovery of 102%. Full article

Harnessing solar energy offers a sustainable alternative for powering electrolysis for green hydrogen production as well as wastewater treatment. The high costs and logistical challenges of electrolysis have resulted in limited widespread investigation and implementation of electrochemical technologies on an industrial scale. To overcome these challenges, this study designs and tests a new approach to chemical experiments and wastewater treatment research using a portable standalone open-source solar photovoltaic (PV)-powered station that can be located onsite at a wastewater treatment plant with unreliable electrical power. The experimental system is equipped with an energy monitoring data acquisition system. In addition, sensors enable real-time monitoring of gases—CO, CO₂, CH₄, H₂, H₂S, and NH₃—along with temperature, humidity, and volatile organic compounds, enhancing safety during electrochemical experiments on wastewater, which may release hazardous gases. SAMA software was used to evaluate energy-sharing scenarios under different grid-connected conditions, and the system can operate off the power grid for 98% of the year in Ontario, Canada. The complete system was tested utilizing a laboratory-scale electrolyzer (electrodes of SS316L, Duplex 2205, titanium grade II and graphite) with electrolyte solutions of potassium hydroxide, sulfuric acid, and secondary wastewater effluent. The electrolytic cell specifically developed for testing electrode materials and wastewater showed a Faraday efficiency up to 95% and an energy efficiency of 55% at STP, demonstrating the potential for use of this technology in future work. Full article

Graphite, a critical material for furnace walls, is pivotal to the reliability of the carbon-free hydrogen production industry through methane pyrolysis catalyzed by molten metals. This study systematically investigates the corrosion behavior of molten CuSn alloy on three typical commercial graphite materials—low-density graphite (LDG), high-density graphite (HDG), and pyrolytic graphite (PyG)—with a focus on their corrosion resistance and the underlying mechanisms responsible for graphite corrosion over a period of up to 1000 h at 1100 °C. The experimental results show that LDG suffered the most severe corrosion, with a mass loss of up to 60.09% and a hardness decrease from 0.73 GPa to 0.17 GPa, whereas PyG demonstrated the best corrosion resistance, with only a 5.64% mass loss and a hardness drop from 0.52 GPa to 0.35 GPa. SEM and XRD analyses revealed that the porous structures of LDG and HDG suffered significant macroscopic corrosion, caused by the stress from molten metal infiltration and aggregation in the pores, leading to structural collapse. Interestingly, all three types of graphite, including the non-porous PyG, exhibited disordered microstructural degradation as detected by Raman spectroscopy. Molecular dynamics (MD) simulations confirmed that the thermal motion of Cu and Sn atoms primarily drives the microstructural corrosion of graphite, suggesting that the corrosion process involves both micro- and macro-level damage. These findings provide crucial insight into the compatibility of different graphite materials with molten CuSn alloy and valuable guidance for material selection in methane pyrolysis devices. Full article

The study introduces new technologies of microfinishing, which are primarily aimed at cylindrical surfaces but with machining effectiveness, precision, and surface longevity. In the newly proposed dual-zone microfinishing method, symmetrical abrasive film feeding systems are adapted with a lever mechanism and a pivoting pressing assembly to simultaneously conduct processing in two zones. With such a design, uniform force distribution is ensured, while mechanical deformation is reduced to raise the utility of the abrasive film and lower scraps for better economic performance. Also, the application of microfinishing operations combined with carbon layer deposition using graphite-impregnated abrasive films is introduced as a novel method. This process combines surface refinement and the forming of wear-resistant carbon coatings into one single operation, resulting in increased wear resistance and reduced forces of friction. Further stabilization of the conditions for microfinishing is achieved by immersing the processing zone in a fluid medium due to increased lubrication, improvement in heat dissipation, and the optimization of surface properties. It is particularly suitable for high-precision applications and a maintenance-free environment such as military, vacuum, and low-temperature systems. The experimental results show the effectiveness of the proposed methodologies, underscoring their ability to create remarkably smooth surfaces and very robust carbon textures simultaneously. Full article

Nuclear power plants have the lowest life-cycle greenhouse gas emissions intensity and produce more electricity with less land use compared to any other low-carbon-emission-based energy source. There is growing global interest in Generation IV reactors and, at the same time, there is great interest in using small modular reactors. However, the development of new reactors introduces new engineering and chemical challenges critical to advancing nuclear energy safety, efficiency, and sustainability. For Generation III+ reactors, water chemistry control is essential to mitigate corrosion processes and manage radiolysis in the reactor’s primary circuit. Generation IV reactors, such as molten salt reactors (MSRs), face the challenge of handling and processing chemically aggressive coolants. Small modular reactor (SMR) technologies will have to address several drawbacks before the technology can reach technology readiness level 9 (TRL9). Issues related to the management of irradiated graphite from high-temperature reactors (HTR) must be addressed. Additionally, spent fuel processing, along with the disposal and storage of radioactive waste, should be integral to the development of new reactors. This paper presents the key chemical and engineering aspects related to the development of next-generation nuclear reactors and SMRs along with the challenges associated with them. Full article

The molten-salt electrolytic method was employed to recycle spent SCR catalyst to prepare TiC compound. A systematic investigation has been carried out through thermodynamic calculation and experimental analysis. The effects of graphite content, cell voltage, electrolyzing temperature, and electrolyzing time on electrolytic products were explored. The results show that a suitable amount of graphite content, high cell voltage, and a high electrolyzing temperature are beneficial to promote the formation of TiC compounds. It has also been found that the electroreduction of spent SCR catalyst/graphite can completely transform it into TiC compound in a relatively short time. The final electrolytic product is confirmed to be a solid solution of (Ti, W, Si, V)C. Meanwhile, the electrolytic process and reaction mechanism were investigated through the analysis of intermediates and the thermodynamic calculation. The electrolytic product has a potential application as reinforcement in metal matrix, which is a high additional-value utilization for spent SCR catalysts. Full article

This work presents results on nanosecond laser ablation of a titanium (Ti) plate immersed in a liquid medium using the fundamental wavelength (1064 nm) of a nanosecond Nd:YAG laser system. The laser radiation was focused on the target surface as scanning was accomplished by an XY translation stage. The laser processing of the Ti targets took place in two organic liquids—liquid paraffin and diesel oil. The morphology of the structured surfaces and the structure and phase composition of the samples were studied; their dependences on the processing parameters are discussed. With both liquid media used, crack formation on the surface of the laser-treated Ti target was observed. Formation of a titanium carbide (TiC) phase was found whose properties could be tuned by varying the laser irradiation parameters. Raman measurements were utilized to analyze the carbon structure formed in the resulting coatings. The results of surface electron microscopy reveal that the thickness of the resulting coatings reached 20 µm. Some of the obtained coatings demonstrated about three times higher hardness compared to the native Ti sample. The technique proposed can be used in surface modification of materials in view of improving their mechanical properties. Full article

Research on converting methane to hydrogen has gained more attention due to the availability of methane reserves and the global focus on sustainable and environmentally friendly energy sources. The decomposition of methane through catalysis (CDM) has excellent potential to produce clean hydrogen and valuable carbon products. However, developing catalysts that are both active and stable is a highly challenging area of research. Using titanium isopropoxide as a precursor and different loadings of TiO₂ (10 wt.%, 20 wt.%, and 30 wt.%), alumina has been coated with TiO₂ in a single-step hydrothermal synthesis procedure. These synthesized materials are examined as possible support materials for CDM; different wt.% of iron is loaded onto the synthesized support material using a co-precipitation method to enhance the methane conversion via a decomposition reaction. The result shows that the 20 wt.% Fe/20 wt.% Ti-Al (20Fe/20Ti-Al) catalyst demonstrates remarkable stability and exhibits superior performance, reaching a conversion rate of methane of 94% with hydrogen production of 84% after 4 h. The outstanding performance is primarily due to the moderate interaction between the support and the active metal, as well as the presence of the rutile phase. The 20Fe/30Ti-Al catalyst exhibited lower activity than the other catalysts, achieving a methane conversion of 85% and hydrogen production of 79% during the reaction. Raman and XRD analysis revealed that all the catalysts generated graphitic carbon, with the 20Fe/20Ti-Al catalyst specifically producing single-walled carbon nanotubes. Full article

Pure phase change materials (PCMs) have drawbacks such as low thermal conductivity and poor physical properties like flammability, which limit their further application in battery thermal management systems. This paper introduces an innovative flame-retardant composite phase change material (CPCM) made from paraffin, expanded graphite, chitosan (CS), ammonium polyphosphate (APP), and aluminum hypophosphite (AHP). The physicochemical properties and flame-retardant performance of CPCMs with five different flame-retardant ratios of 9%, 12%, 15%, 18%, and 21% are studied, and their application effects in battery thermal safety are revealed. The results show that the combination of flame retardants CS, APP, and AHP exhibits effective synergistic effects, and the prepared CPCM exhibits good flame-retardant properties and thermal management effects. The CPCM exhibits outstanding thermal management performance when the flame-retardant content is 12%. At a maximum discharge rate of 3C, compared to natural air-cooling conditions, the maximum battery temperature and temperature difference are controlled within the safe range of 41 °C and below 5 °C, respectively. The CPCM can play an important role in the thermal safety of lithium-ion batteries. Full article

Advanced oxidation processes based on either peroxydisulfate (PDS) or peroxymonosulfate (PMS), collectively termed persulfate-based advanced oxidation processes (PS-AOPs), show potential in wastewater treatment applications. In this work, the nitrogen (N) and sulfur (S) co-doped biochar (NSBC) was prepared via a one-step pyrolysis of coffee grounds at 400 to 800 °C as a PMS activator for degrading paracetamol (PCT). The non-metallic NSBC demonstrated exceptional catalytic activity in activating PMS. In the NSBC-800/PMS system, 100% of PCT was completely degraded within 20 min, with a high reaction rate constant (k_obs) of 0.2412 min⁻¹. The system’s versatility was highlighted by its degradation potential across a wide pH range (3–11) and in the presence of various background ions and humic acids. The results of various experiments and characterization techniques showed that the system relied on an NSBC-800-mediated electron transfer as the main mechanism for PCT degradation. Additionally, there was a minor involvement of ¹O₂ in a non-radical degradation pathway. The graphitic N and thiophene-S (C-S-C) moieties introduced by N/S co-doping, as well as the carbonyl (C=O) groups of the biochar, were considered active sites promoting ¹O₂ generation. The total organic carbon (TOC) removal rate reached 37% in 120 min, while the assessment of the toxicity of the degradation products also affirmed the system’s environmental safety. This research provides a novel method for preparing environmentally friendly and cost-effective carbon-based catalysts for environmental remediation. Full article

Adsorption chillers are distinguished by their low electricity consumption, lack of moving parts and exceptional reliability. However, their considerable weight, due to the low sorption capacity of conventional adsorbents, remains a key limitation. This study investigates the effect of introducing thermally conductive additives—aluminium powder, copper powder and graphite flakes—at 5, 15 and 25 wt.% to silica-gel-based adsorbent beds on the enhancement of heat transfer. In contrast to other works, this study also includes a novel analysis of the thermal properties of dry sorbents, since the moisture content affects the thermal conductivity. Additives improve the thermal conductivity, as measured by the laser flash method (LFA), of the bed by up to 20.7% while maintaining a reasonable sorption capacity, as measured by the dynamic vapor sorption (DVS). Additions of copper at 5–15 wt.% and graphite flakes at 15–25 wt.% provide an optimal compromise between thermal conductivity and sorption capacity. Aluminium powder, on the other hand, offers flexibility over a wider range (5–25 wt.%). The increased thermal conductivity of these modified materials is expected to lead to more efficient heat transport, which suggests the hypothesis that it could reduce the cycle time and increase the efficiency of adsorption chillers. Full article

The copper-based steel backing material is prepared using a combination of mechanical alloying and secondary sintering methods. The effect of Y₂O₃ content on the microstructure, hardness, and tribological properties of the copper-based self-lubricating layer is investigated. The results demonstrate that the addition of Y₂O₃ enhances the strength of the copper-based self-lubricating layer. Graphite and Y₂O₃ act synergistically to form a three-dimensional supporting framework, thereby boosting the overall strength of the copper-based composite material and increasing its Brinell hardness by 27%. Additionally, the incorporation of Y₂O₃ effectively improves the tribological properties of the composite material, significantly reducing wear during the friction process and decreasing the wear rate by 77%. Under the experimental conditions, the optimal Y₂O₃ content is determined to be 1 wt%. Full article

Vacancy defect graphitic carbon nitride (g-C₃N₄) and conjugated polyimide (PI) polymer photocatalysts have become increasingly recognized as metal-free photocatalysts featuring an appropriate bandgap. The narrow absorption spectrum of visible light and the rapid recombination rate of the photoexcited charge carriers in PI polymers and g-C₃N₄ impede its photocatalytic performance. The presence of oxygen vacancies (OVs) in PI polymer photocatalysts, as well as nitrogen vacancies (NVs) and carbon vacancies (CVs) in g-C₃N₄, can significantly enhance the migration of photogenerated electrons. Adding vacancies to improve the electronic structure and band gap width can greatly enhance the photocatalytic efficiency of PI polymers and g-C₃N₄. Defect engineering is important for increasing the photocatalytic ability of PI-polymer and g-C₃N₄. There remains a notable absence of thorough review papers covering the synthesis, characterization, and applications of vacancy-rich PI-polymer and g-C₃N₄ in photocatalysis. This review paper examines the roles of OVs in PI-polymer, NVs, and CVs in g-C₃N₄ and thoroughly summarizes the preparation approaches employed before and after, as well as during polymerization. This review scrutinizes spectroscopic characterization techniques, such as EPR, XPS, PAS, XRD, FTIR, and NMR, for vacancy defect analysis. We also reviewed the role of vacancies, which include light absorption, photogenerated charge carrier separation, and transfer dynamics. This review could serve as a comprehensive understanding, a vacancy-engineered design framework, and a practical guide for synthesizing and characterizing. Full article

Numerous fire disasters have involved thermoplastic expanded polystyrene (EPS) external thermal insulation composite systems (ETICS) on building façades. This study evaluates the flame-retardant efficiency of expandable graphite (EG)-blended EPS ETICS across different scales: micro-scale thermogravimetric (TG) analysis, small-scale bench tests, and large-scale LEPIR 2 tests. TG analysis confirmed EG’s primary role as a physical intumescent, with no significant chemical interactions detected. While EG effectively reduced heat penetration in both small-scale and large-scale fire tests, challenges arose from char layer detachment and oxidation at elevated temperatures (exceeding 540 °C). Despite these limitations, the EG-treated façade exhibited significantly lower peak temperatures compared to the untreated control in the large-scale LEPIR 2 test, with a measured temperature difference of approximately 470 °C. These findings demonstrate the potential of EG to enhance the fire safety of EPS ETICS. The small-scale test bench proved effective for preliminary material screening, providing valuable insights into ignition resistance and flame-retardant properties before proceeding to more resource-intensive large-scale evaluations. Full article

Carbon nitrides are polymeric materials with a broad range of applications, including photocatalysis. Among them, graphitic carbon nitride (g-C₃N₄), a low-cost material, is an excellent photocatalyst under visible light irradiation owing to its features such as correct band positions, high stability and non-toxicity. g-C₃N₄ is a metal-free material that is easily synthesized by polymerizing nitrogen-rich compounds and is an efficient heterogeneous catalyst for many reaction procedures due to its distinctive electronic structure and the benefits of the mesoporous texture. In addition, in situ or post-modification of g-C₃N₄ can further improve catalytic performance or expand its application for remediating environmental pollution. Water pollution from organic compounds such as pesticides and pharmaceuticals is increasing dramatically and is becoming a serious problem around the world. These pollutants enter water supplies in a variety of ways, including industrial and hospital wastewater, agricultural runoff, and chemical use. To solve this problem, photocatalysis is a promising technology. Without the use of other oxidative chemicals, g-C₃N₄ uses renewable solar energy to transform harmful pollutants into harmless products. As a result, much recent research has focused on the photocatalytic activity of g-C₃N₄ for wastewater treatment. For this reason, the main objective of this paper is to contribute a chronological overview of the bibliometrics on g-C₃N₄ for the removal of pesticides and pharmaceuticals from water using the tools BibExcel, Bibliometrix and R-Studio IDE. A bibliometric analysis was performed using the Science Citation Index Expanded (WoS^©) database to analyze the scientific literature published in the field over the last 10 years. The results were used to identify limitations and guide future research. Full article