Search Results (604)

In the present work, the synthesis and decomposition of low-dimensional materials from a Ni${}_{15}$Mo${}_{25}$W${}_{10}$C${}_{50}$ system produced by mechanical alloying was reported. During the milling process, the resultant phases were WMoC and NiC, and after sintering and quenching, MoNi${}_3$, WMo, Ni${}_4$W, WC, MoNi and Mo${}_2$C were found. The samples were analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Nanotubes with the lengths ranging from 500 nm to 2 $\mathsf{\mu }$m, spheres and novelty globular particles with sizes ranging from 40 to 600 nm as well as “petal-like” estructure were observed. The results revealed the formation of a microstructure with morphology similar to spinodal decomposition followed by a sequence of invariant reactions leading the production of modulated and novel branched structures. We proposes a theoretical mechanism of formation that is associated with the modulated structure observed after quenching. Full article

Biochar is a biomaterial obtained by pyrolysis with high porosity and high specific surface area (SSA), which is widely used in several fields. The yield of biochar has an important effect on production cost and utilization efficiency, while SSA plays a key role in adsorption, catalysis, and pollutant removal. The preparation of biochar materials with better SSA is currently one of the frontiers in this research field. However, traditional methods are time consuming and laborious, so this paper developed a machine learning model to predict and study the properties of biochar efficiently for engineering through cross-validation and hyper parameter tuning. This paper used 622 data samples to predict the yield and SSA of biochar and selected eXtreme Gradient Boosting (XGBoost) as the model due to its excellent performance in terms of performance (yield correlation coefficient R² = 0.79 and SSA correlation coefficient R² = 0.92) and analyzed it using Shapley Additive Explanation. Using the Pearson correlation coefficient matrix revealed the correlations between the input parameters and the biochar yield and SSA. Results showed the important features affecting biochar yield were temperature and biomass feedstock, while the important features affecting SSA were ash and retention time. The XGBoost model developed provides new application scenarios and ideas for predicting biochar yield and SSA in response to the characteristic input parameters of biochar. Full article

A simple method is presented for the continuous generation of carbon nanotube forests stably anchored on stainless-steel surfaces using a reactive-roll-to-roll (RR2R) configuration. No addition of catalyst nanoparticles is required for the CNT-forest generation; the stainless-steel substrate itself is tuned to generate the catalytic growth sites. The process enables very large surfaces covered with CNT forests to have individual CNT roots anchored to the metallic ground through primary bonds. Fog water harvesting is demonstrated and tested as one potential application using long CNT-covered wires. The RR2R is performed in the gas phase; no solution processing of CNT suspensions is used, contrary to usual R2R CNT-based technologies. Full or partial CNT-forest coverage provides tuning of the ratio and shape of hydrophobic and hydrophilic zones on the surface. This enables the optimization of fog water harvesters for droplet capture through the hydrophobic CNT forest and water removal from the hydrophilic SS surface. Water recovery tests using small harp-type harvesters with CNT-forest generate water capture of up to 2.2 g/cm²·h under ultrasound-generated fog flow. The strong CNT root anchoring on the stainless-steel surfaces provides opportunities for (i) robustness and easy transport of the composite structure and (ii) chemical functionalization and/or nanoparticle decoration of the structures, and it opens the road for a series of applications on large-scale surfaces, including fog harvesting. Full article

Water contamination is a pervasive global crisis, affecting over 2 billion people worldwide, with pharmaceutical contaminants emerging as a significant concern due to their persistence and mobility in aquatic ecosystems. This review explores the potential of activated hydrochars, sustainable materials produced through biomass pyrolysis, to revolutionize the removal of pharmaceutical contaminants from water sources. These materials possess high surface area, porous structure, and exceptional adsorption capabilities, making them a promising solution. The impact of pharmaceutical contaminants on aquatic ecosystems and human health is far-reaching, affecting biodiversity, water quality, and public health. To address this complex issue, a diverse range of techniques, including adsorption, biodegradation, and advanced oxidation processes, are employed in the pharmaceutical industry. Activated hydrochars offer substantial adsorption capacity, sustainable feedstock origins, and a minimal carbon footprint. This review highlights their potential in pharmaceutical contaminant removal and their broader applications in improving soil and air quality, resource recovery, and sustainable waste management. Interdisciplinary collaboration and the development of intelligent treatment systems are essential to fully unlock the potential of activated hydrochars. Regulatory support and policy frameworks will facilitate their responsible and widespread application, promising a cleaner and more sustainable future. This paper aims to inform scientists, environmental experts, policymakers, and industry stakeholders about the promising role of activated hydrochars in addressing pharmaceutical contaminant challenges. Full article

Graphene quantum dot (GQD) is a new type of carbon nanometer material. In addition to the excellent properties of graphene, it is superior due to the quantum limit effect and edge effect. Because of its advantages such as water solution, strong fluorescent, small size, and low biological toxicity, it has important application potential in various fields, especially in sensors and biomedical areas, which are mainly used as optical electrical sensors as well as in biological imaging and tumor therapy. In addition, GQDs have very important characteristics, such as optical and electrical properties. There are many preparation methods, divided into top-down and bottom-up methods, which have different advantages and disadvantages, respectively. In addition, the modification methods include heterogeneous doping, surface heterogeneity, etc. There are still many challenges in developing GQDs. For example, the synthesis steps are still hard to conduct, but as the inquiry continues to deepen, GQDs will be revolutionary materials in the future. In this work, the literature concerning research progress on GQDs has been reviewed and summarized, while the key challenges of their application have been pointed out, which may bring new insights to the application of GQDs. Full article

In recent times, biochar has emerged as a promising and sustainable solution for COD reduction in wastewater treatment. This study explores the potential of chemically modified biochars as efficient adsorbents for the removal of organic contaminants, specifically oils, fats, and grease (OFG), from wool scouring wastewater. Proximate analysis revealed distinct properties among the biochars, with KOH-treated biochar demonstrating the most promising characteristics, including lower volatile matter, higher fixed carbon content, and reduced ash content, indicating a stable and carbon-rich structure. A meticulous examination of the KOH-treated biochar’s surface characteristics revealed the presence of elevated carbon and nitrogen content, complemented by an expansive surface area measuring 724.4 m²/g. This surface area was at least twice as extensive as that observed in the other post-treated biochar samples. The kinetic adsorption of COD and soluble COD was well fitted by the pseudo-first-order model, with equilibrium achieved in approximately 200 min. The KOH-treated biochar exhibited the highest equilibrium adsorption capacities for both COD and soluble COD in both Dorset wool (Dorset) and Bluefaced Leicester (BFL) wastewater, highlighting its efficacy in OFG removal. Despite these promising results, further research is needed to explore biochar’s surface characteristics, pore structure, and performance under diverse conditions, as well as its integration with existing treatment processes and potential for regeneration and reuse. This study contributes to advancing sustainable wastewater treatment methods using chemically modified biochars. Full article

We conducted a large set of ab initio density functional theory computations to model a variety of hammer-terminated graphene nanoflakes—finite counterparts of armchair graphene nanoribbons. We focused on the relationships among the length and width of the nanoflakes, the stoichiometry and the conformation of the hydrogen saturation of the caps, and the resulting electronic structure. The energetics and the thermodynamic stability of the nanoflakes were investigated as well. Based on this study, we provide a recipe for determining the most stable saturation of the dangling bonds at the caps, which is generally disregarded in theoretical studies, and we prove that this step is crucial for a reliable description of the electronic structure of these systems. Data analysis proved that flakes far from the most stable C–H pattern exhibited electronic properties that were typical of an unsaturated bonding structure. Based on thermodynamics, we also proved that, for any given flake, there was a well-defined hydrogen content and a conformation of H atoms at the caps, which were favored across a wide range of environmental conditions. Full article

The hybrid structure of Graphene and ZnO (Graphene/ZnO) is emerging as a novel material used to achieve the high performance of photocatalysis. In this study, we examined the ZnO characteristics that affect the photocatalytic activity of graphene/ZnO using a lamellar structure of graphene and ZnO thin films. Graphene samples were synthesized via chemical vapor deposition, and a typical wet process was applied to transfer them on sputter-deposited ZnO thin films with and without annealing. We confirmed that graphene-deposited ZnO demonstrated more efficient photocatalytic behavior toward the decomposition of methylene blue (as a model organic compound) with ordinary sputtered ZnO thin films. Again, ZnO thin films annealed at 1000 °C in an N₂ gas atmosphere with graphene performed better than unannealed films. XRD analysis confirmed that pre-thermal treatment of a ZnO thin film promoted re-crystallization, which had less impact on the photocatalytic improvement. The attachment of graphene to the film is considered to contribute to the enhancement. Raman analysis revealed that the graphene coverage areas on the post-annealed ZnO increased by two times compared to that of an unannealed film where the unannealed film had a higher graphene layer. The results presented in this study demonstrate that an annealed ZnO thin film forms a better attachment with graphene, resulting in a larger graphene coverage area with fewer multilayers, which effectively improves the photocatalytic activity in composite structures. Full article

Sulphur-doped graphene was fluorinated using molecular fluorine (F₂). First, the fluorination conditions were adapted in order to be mild enough to maintain S in the carbon lattice and form S-F bonds. An unusually weakened C-F bonding for an F/C ratio of 0.71 was then achieved, which allowed enhanced performances when used as a cathode in primary lithium batteries. The material prepared at a moderate fluorination temperature of 70 °C for a period of 60 min exhibits a high mid-discharge reduction potential of 3.11 V at 10 mA/g and a power density of 3605 W/kg at a discharge rate of 2C. These electrochemical properties make the fluorine/sulfur co-doped graphene a promising material. Full article

Chlorella vulgaris is an inexpensive microalga that could be employed for environmental remediation, but further investigations are needed to assess its suitability and optimal treatment methodology. With this aim in mind, this study focused on the raw biomass and the biochar and hydrochar obtained from it, analyzing their physicochemical properties and testing them to capture cadmium from an aqueous environment. The adsorption/absorption tests assessed the effect of adsorbent dosage, pH, Cd concentration, and contact time, and the results were analyzed through a structural equation model. Biochar and hydrochar performed similarly and better than the raw biomass, with the highest Cd removal observed at an adsorbent dosage of 0.8 g L⁻¹, an initial concentration of Cd solution of 30 mg L⁻¹, a pH of 6, and a contact time of 30 min. The adsorption isotherm data for Cd could be well-described by the Langmuir and Temkin models. The results from the structural equation modeling revealed that the variables material type, dosage, and concentration all contributed to Cd removal in water, with time mediating these effects. Full article

The considerable expenses associated with carbon fiber (CF) production have imposed limitations on its widespread application across diverse industries, primarily due to the costs of precursor materials and energy−intensive post−treatment procedures. This research explores the potential utilization of Alberta oilsands asphaltenes (AOAs), a carbon−rich by−product derived from oilsands extraction, as a more cost−effective precursor for CF production. Polystyrene and poly(styrene–butadiene–styrene) were also used as polymer additives. In addition to conventional thermal post−treatment, microwave plasma was employed for the carbonization process. The CFs generated through this approach were subjected to a comprehensive analysis involving SEM, FTIR, TGA, XRD, and Raman spectroscopy. The best tensile strength and Young’s modulus of the AOA carbon fibers when using conventional thermal post−treatment were 600 MPa and 70 GPa, respectively. The microwave plasma process indicates the higher temperature and promise of eliminating heteroatoms of AOA carbon fibers. The temperature for microwave plasma modelling was set using COMSOL^TM, with the modelling temperature and detection temperature being established at 1600 K and 1568 K, respectively. Full article

The accumulation of waste tires has resulted in very urgent environmental problems. Pyrolysis has been regarded as a green eco-friendly technology to deal with waste tires, and it is vital to make use of the pyrolysis carbon. Herein, we propose a new way to utilize pyrolysis carbon, to prepare carbon nanotubes with the help of ferrocene. The optimal preparation processes were determined by optimizing the parameters including the solvent, temperature, time, etc. The results of scanning electron microscopy and transmission electron microscopy evidenced the successful formation of carbon nanotubes. Meanwhile, the Brunauer–Emmett–Teller (BET) method and N₂-adsorption showed that the yielded carbon nanotubes featured a large surface area and abundant pore structure in comparison with the pyrolytic carbon. Finally, the as-prepared carbon nanotubes were applied as the supports for Pt-based catalysts for the dehydrogenation of methylcyclohexane to produce hydrogen. The results showed that the Pt/carbon-nanotubes catalyst exhibited the highest conversion of methylcyclohexane (28.6%), stability, and hydrogen evolution rate (336.9 mmol/g_Pt/min) compared to the resulting Pt/commercial-activated-carbon (13.6% and 160.2 mmol/g_Pt/min) and Pt/pyrolytic-carbon catalysts (0.19% and 2.23 mmol/g_Pt/min). Full article

Since the Industrial Revolution, human economic activity and the global development of society in general have been heavily dependent on the exploitation of natural resources. The use of fossil fuels, deforestation, the drainage of wetlands, the transformation of coastal marine ecosystems, unsustainable land use, and many other unbalanced processes of human activity have led to an increase both in the anthropogenic emissions of climate-active gases and in their concentration in the atmosphere. It is believed that over the past ~150 years these phenomena have contributed to an increase in the global average temperature in the near-surface layer of the atmosphere by ~1 °C. Currently, the most pressing tasks facing states and scientific and civil societies are to reduce anthropogenic CO₂ emissions and to limit the global air temperature increase. In this regard, there is an urgent need to change existing production systems in order to reduce greenhouse gas emissions and to sequester them. In this review, we consider up-to-date scientific approaches and innovative technologies, which may help in developing roadmaps to reduce the emissions of climate-active gases, control rising temperatures, decarbonize economies, and promote the sustainable development of society in general. Full article

Films of a vitrimer based on the reaction between diglycidylether of bisphenol A and glutaric acid in the presence of 1-methylimidazole were processed using a solvent-based technique. The curing schedule was divided into two steps: first, a soluble linear polymer was formed through the reaction of the diacid and the diepoxide, and then the crosslinking was induced at a higher temperature via transesterification reactions. This epoxy–acid vitrimer was modified with multi-walled carbon nanotubes (MWCNTs) functionalized with β-hydroxyesters, produced by a robust and straightforward strategy based on a two-phase reaction between oxidized MWCNTs and phenylglycidylether. Nanocomposite vitrimer films were obtained by drop casting a dispersion of the functionalized MWCNTs in the linear polymer/cyclohexanone solution, followed by a thermal treatment. A high degree of dispersion of the carbon nanostructures was attained thanks to the β-hydroxyester functionalization when compared with oxidized MWCNTs. Nanocomposite films showed a significant photothermal effect (reaching 200 °C or above in 30 s) upon NIR light irradiation (850 nm) from a single LED (500 mW/cm²). The released heat was used to activate the shape memory effect and weld and heal the vitrimer matrix, proving the success of this easy strategy for the generation of remotely activated carbon-based vitrimer nanocomposites. Full article

The advancement of renewable energy technologies like water electrolysis and hydrogen fuel cells relies on the fabrication of effective and reliable catalysts for the hydrogen evolution process (HER). In this regard, we report gold nanoparticles embedded in laser-induced graphene electrodes for regulation of overpotential and electrocatalytic performance of hydrogen evolution reaction. Gold nanoparticles were deposited onto the LIG surface using electrode deposition via cyclic voltammetry (CV) at different cycle lengths. The catalyst fabrication technique enables the manipulation of many electrochemical parameters, such as overpotential value, charge transfer resistance, electrochemical active surface area, and tafel slope, through the adjustment of cyclic voltammetry (CV) cycles. The LIG-Au@50 sample demonstrates remarkable electrocatalytic characteristics, as evidenced by its low overpotential of 141 mV at a current density of 10 mA/cm² and reduced tafel slope of 131 mV/decade in an acidic environment. Furthermore, the presence of an augmented electrochemical active surface area, a mass activity of 8.80 A/g, and a high turnover frequency of 0.0091 s⁻¹ suggest elevated and significant accessibility to plentiful active sites. A significant decrease in charge transfer resistance resulted in an enhanced rate of the water-splitting reaction. Full article