Search Results (28)

The development of lightweight composites with superior mechanical properties and electromagnetic interference (EMI) shielding performance is essential for various structural and functional applications. This study investigates the effect of hybrid nanocarbon (graphene nanosheet (GNS) and carbon nanotube (CNT)) reinforcements on the properties of magnesium (Mg) matrix composites. Specifically, the GNS-CNT hybrid, which forms a three-dimensional interconnected network structure, was analyzed and compared to composites reinforced with only GNSs or CNTs. The objective was to determine the benefits of hybrid reinforcements on the mechanical strength and EMI shielding capability of the composites. The results indicated that the GNS-CNT/Mg composite, at a nanocarbon content of 0.5 wt.% and a GNS-CNT ratio of 1:2, achieved optimal performance, with a 55% increase in tensile strength and an EMI shielding effectiveness of 70 dB. The observed enhancements can be attributed to several key mechanisms: effective load transfer, which promotes tensile twinning, along with improved impedance matching and multiple internal reflections within the GNS-CNT network, which enhance absorption loss. These significant improvements position the composite as a promising candidate for advanced applications requiring high strength, toughness, and efficient electromagnetic shielding, providing valuable insights into the design of high-performance lightweight materials. Full article

This study developed a highly facile method to synthesize Zn-decorated and nitrogen-doped hierarchical porous carbons for carbon dioxide (CO₂) adsorption. Zeolitic imidazolate framework-8 (ZIF-8) was used as the raw material, which was subjected to a thermal treatment to obtain ZIF-8-derived carbons (ZDCs) in order to develop nanocarbons with a stable framework structure, a high CO₂ adsorption capacity, and high selectivity under normal pressure. The crystallinity evolution of the samples changed from the typical ZIF-8 structure to having features of graphite carbons upon heating. The average particle sizes of the products were between 34 and 105 nm, and the specific surface areas ranged from 618 to 1862 m²/g. The nitrogen and zinc contents gradually decreased with increasing carbonization temperatures, but the changes in the distributions of the functional groups were different. The interactions between CO₂ and the ZDCs were significantly enhanced, resulting in a higher isosteric heat of adsorption. The ZIF-8 carbonized at 1123 K exhibited the highest CO₂ uptake, i.e., 3.57 mmol/g at 298 K and 101.3 kPa, while higher CO₂ uptakes at 15 kPa occurred on the ZIF-8 carbonized at 923 and 1023 K due to their high isosteric heat of adsorption of CO₂. The higher adsorption selectivity of Z8-650 for CO₂ over N₂ may be due to its higher V_<0.7nm/V_mi ratio and nitrogen and zinc contents. Consequently, the micropore area ratio and surface functional groups primarily determined the CO₂ adsorption capacity at 15 kPa. In addition, an appropriate metal Zn to Zn²⁺ ratio may have a positive effect on CO₂ adsorption. On the other hand, the ultramicropore volume ratio, micropore volume ratio, micropore area, and SSA played more significant roles at 101.3 kPa of pressure. Full article

Carbon dots (CDots) are classically defined as small carbon nanoparticles with effective surface passivation, which, in the classical synthesis, has been accomplished by surface organic functionalization. CDot-like nanostructures could also be produced by the thermal carbonization processing of selected organic precursors, in which the non-molecular nanocarbons resulting from the carbonization are embedded in the remaining organic species, which may provide the passivation function for the nanocarbons. In this work, a mixture of oligomeric polyethylenimine and citric acid in the solid state was used for efficient thermal carbonization processing with microwave irradiation under various conditions to produce dot samples with different nanocarbon content. The samples were characterized in terms of their structural and morphological features regarding their similarity or equivalency to those of the classical CDots, along with their significant divergences. Also evaluated were their optical spectroscopic properties and their photoinduced antimicrobial activity against selected bacterial species. The advantages and disadvantages of the thermal carbonization processing method and the resulting dot samples with various features and properties mimicking those of classically synthesized CDots are discussed. Full article

In this paper, VGCF/304L stainless steel composite was prepared using spark plasma sintering (SPS) with 2 vol.% nanocarbon fiber. Then, phase content, grain size, and mechanical properties were evaluated. The results showed that the Vickers hardness of 304L sintered stainless steel and the composite prepared by SPS under the condition of 950 °C for 10 min were 244 HV and 310 HV, respectively, which is an increase of about 27.0%. The yield strength ascended from 587.1 MPa to 890.2 MPa, registering an increase of approximately 51.6%. Concurrently, the ultimate tensile strength rose from 821.5 MPa to 1064.7 MPa, with an approximate increase of 29.6%. This method for improving the mechanical properties of stainless steel is expected to be widely adopted for producing fiber-reinforced metal matrix composites with excellent overall performance. Full article

In this work, the influence of surface functionalization due to synthesis conditions of graphene oxide quantum dots GOQDs was evaluated for dopamine (DA) detection. GOQDs were synthesized using HNO₃ (6 M or 8 M) through a liquid-phase oxidation method. The characterization (HRTEM, FTIR, Raman, and XRD) and evaluation by amperometry (AMP) and differential pulse voltammetry (DPV) showed that GOQDs-8 synthesized with higher oxygen content were more sensitive and selective in DA detection than GOQDs-6. The synergistic effects of electrostatic attraction from glassy carbon electrode negatively charged surface, functionalization for inner-sphere mechanism, and edge effect from lower particle size resulted in amplified electrochemical signal achieving detection at nanomolar level using AMP and DPV. When evaluated using AMP, GCE/GOQDs-8 showed a sensitivity of 0.0422 μA μM^–1, a limit of detection (LOD) of 17.6 nM, a linear range from 0.1 to 100 μM, and minimal interference for uric acid, levodopa, and acetaminophen. In contrast, using DPV, the GCE/GOQDs-8 exhibited a sensitivity of 0.0616 μA μM^–1, a LOD of 506 nM, and a linear range from 0.1–30 μM with remarkable selectivity from all interferent species. The assay of GOQDs-8/GCE sensor in normal human serum proved to be feasible for the practical determination of DA. The recovery obtained was in the range of 94.1 to 112.8% with a relative standard deviation (RSD), n = 3 of less than 3.62%. The oxygen-rich material showed a promising performance that can be further improved with additional nanocarbon or conducting polymers supports. Full article

The development of easy and direct real-time monitoring of welded joint quality instead of surface damage analysis is crucial to improve the quality of industrial products. This work presents the results of high-density polyethylene (HDPE)-based composites with various carbon black (CB) content (from 20 to 30 vol.%) for use as a heating element and strain sensor in electrofusion-welded polymer joints. The pyroresistive heating process was used to determine the effect of generated Joule heat during welding on the structure and sensor properties of polymer–carbon composites. It is shown that the generation of Joule heat depends on the nanocarbon content and affects the crystallinity of the polymer matrix. The partial disruption of the conductive path of carbon black particles was observed and, as a result, a decrease in electrical conductivity for composites with lower CB content after welding was found. For the highest CB amount, conductivity increased, which is caused by smaller particle-to-particle distance for filler paths. Therefore, the best balance between pyroresistive and sensor properties was found. Full article

CQDs are a type of fluorescent nanocarbon material that possess excellent optical properties. They have a wide range of raw material sources, making them a versatile option for various applications. The use of fluorescent materials to enhance the solar energy capture capacity of chloroplasts has the potential to significantly improve natural photosynthesis. CQDs and N-CQDs were prepared from natural Salix wood powder using a simple, green, and environmentally friendly hydrothermal method. These materials can effectively capture ultraviolet (UV) light and were used for photosynthesis to enable chloroplasts to utilize UV light that cannot be absorbed by them. The chlorophyll content of leaves treated with CQDs and N-CQDs increased, with the N-CQDs 25 mg/L treated group showing a 35.6% increase compared to the untreated group. Additionally, the treatment of CQDs and N-CQDs positively affected the transfer of electrons from photosystem II, further enhancing photosynthetic activity. This study presents ideas for expanding the use of solar energy, optimizing the photosynthesis charge transfer pathway, and improving solar energy conversion efficiency. Full article

This study presents the effect of iron chloride addition on the production of nanocarbon fibers from softwood Organosolv lignin. It was shown that adding 2% FeCl₃ to the lignin solution before electrospinning to produce lignin nanofibers increased the thermal resistance of lignin fibers during stabilization. FTIR and XPS analyses of the lignin fibers stabilized with and without FeCl₃ revealed that the temperature rate could be increased in the presence of FeCl₃ from 1 to 3 °C/min. The optimal temperature to stabilize the lignin fibers was found to be 250 °C, as higher temperatures led to thermal degradation. Also, carbon fibers were successfully produced from pure softwood Organosolv lignin fibers. Carbonization tests were conducted under nitrogen and the best parameters were determined to be a ramp of 10 °C/min until 600 °C with a holding time of 2 h. Furthermore, the effect of 2% FeCl₃ addition in the lignin solution was investigated during these processes. XPS analysis showed a 93% carbon content for fibers carbonized with and without FeCl₃ addition, while SEM images revealed some surface roughness in fibers with FeCl₃ after carbonization. These results confirm that FeCl₃ addition influences the carbon nanofiber production. Full article

The arrangement of a water thermal accumulator (WTA) containing phase change materials (PCM) is presented and analyzed. The hot or cool water is used as a working body. The accumulator contains two concentric cylindrical tubes. The inner tube is used for hot or cool water flowing, while the volume between the inner and outer tubes is filled with PCM. The thermal energy in the accumulator is stored as a result of flowing the hot water through the inner tube due to the phase transition in PCM. This accumulated energy can be extracted from PCM as a result of flowing the cool water through the inner tube. For the enhancement of the thermal conduction coefficient, the PCM is doped with the nanocarbon particles having a thermal conductivity coefficient exceeding that of PCM by 4–5 orders of magnitude. The thermal balance of the accumulator is calculated on the basis of the solution of the time-dependent heat conduction equation by taking into account the heat absorbed and released as a result of the phase transition as well as the convection thermal exchange in the melted PCM. The calculation results determine the interconnection between the thermal conductivity of PCM and the characteristic time of thermal exchange between PCM and the working body. The calculations indicate that the characteristic thermal exchange time decreases as the thermal conduction coefficient enhances, so that the dependence becomes close to saturation at the thermal conductivity coefficient of about 5 W/m K. Such a coefficient can be reached by doping the paraffin-based PCM with a reduced graphene oxide at a content of about 2% (weight). Full article

The composites with multiple types of nano-carbon fillers have better electrical conductivity and piezoresistive properties as compared with composites with a single type of nano-carbon fillers. As previously reported, the nano-carbon fillers with various aspect ratios, such as carbon nanotube (CNT) and carbon black (CB), have synergistic enhanced effects on the piezoresistive performance of composite sensors. However, most of the works that have been reported are experimental investigations. The efficient and usable numerical simulation investigation needs to be further developed. In this study, based on an integrated 3D statistical resistor network model, a numerical simulation model was created to calculate the piezoresistive behavior of the CNT/CB/ Polyvinylidene Fluoride (PVDF) composite. This model also takes into account the tunneling effect between nearby nano-fillers. It is found from numerical simulation results that the piezoresistive sensitivity of composite simulation cells can be influenced by the fraction of CNT and CB. In the case that the CNT content is 0.073 wt.%, the best force-electrical piezoresistive sensitivity can be achieved when the CB loading is up to 0.2 wt.%. To verify the validity of the simulation model, the previous experimental investigation results are also compared. The experimental results confirm the validity of the model. The investigation is valuable and can be utilized to design a strain sensor for this nano-composite with increased sensitivity. Full article

Among nanocomposite materials, multifunctional polymer nanocomposites have prompted important innovations in the field of sensing technology. Polymer-based nanocomposites have been successfully utilized to design high-tech sensors. Thus, conductive, thermoplast, or elastomeric, as well as natural polymers have been applied. Carbon nanoparticles as well as inorganic nanoparticles, such as metal nanoparticles or metal oxides, have reinforced polymer matrices for sensor fabrication. The sensing features and performances rely on the interactions between the nanocomposites and analytes like gases, ions, chemicals, biological species, and others. The multifunctional nanocomposite-derived sensors possess superior durability, electrical conductivity, sensitivity, selectivity, and responsiveness, compared with neat polymers and other nanomaterials. Due to the importance of polymeric nanocomposite for sensors, this novel overview has been expanded, focusing on nanocomposites based on conductive/non-conductive polymers filled with the nanocarbon/inorganic nanofillers. To the best of our knowledge, this article is innovative in its framework and the literature covered regarding the design, features, physical properties, and the sensing potential of multifunctional nanomaterials. Explicitly, the nanocomposites have been assessed for their strain-sensing, gas-sensing, bio-sensing, and chemical-sensing applications. Here, analyte recognition by nanocomposite sensors have been found to rely on factors such as nanocomposite design, polymer type, nanofiller type, nanofiller content, matrix–nanofiller interactions, interface effects, and processing method used. In addition, the interactions between a nanocomposite and analyte molecules are defined by high sensitivity, selectivity, and response time, as well as the sensing mechanism of the sensors. All these factors have led to the high-tech sensing applications of advanced nanocomposite-based sensors. In the future, comprehensive attempts regarding the innovative design, sensing mechanism, and the performance of progressive multifunctional nanocomposites may lead to better the strain-sensing, gas/ion-sensing, and chemical-sensing of analyte species for technical purposes. Full article

The design and necessity of corrosion-resisting nanocarbon nanocomposites have been investigated for cutting-edge aerospace applications. In this regard, nanocarbon nanofillers, especially carbon nanotubes, graphene, nanodiamond, etc. have been used to fill in various polymeric matrices (thermosets, thermoplastics, and conducting polymers) to develop anti-rusting space-related nanocomposites. This review fundamentally emphases the design, anti-corrosion properties, and application of polymer/nanocarbon nanocomposites for the space sector. An electron-conducting network is created in the polymers with nanocarbon dispersion to assist in charge transportation, and thus in the polymers’ corrosion resistance features. The corrosion resistance mechanism depends upon the formation of tortuous diffusion pathways due to nanofiller arrangement in the matrices. Moreover, matrix–nanofiller interactions and interface formation play an important role in enhancing the corrosion protection properties. The anticorrosion nanocomposites were tested for their adhesion, contact angle, and impedance properties, and NaCl tests and scratch tests were carried out. Among the polymers, epoxy was found to be superior corrosion-resisting polymer, relative to the thermoplastic polymers in these nanocomposites. Among the carbon nanotubes, graphene, and nanodiamond, the carbon nanotube with a loading of up to 7 wt.% in the epoxy matrix was desirable for corrosion resistance. On the other hand, graphene contents of up to 1 wt.% and nanodiamond contents of 0.2–0.4 wt.% were desirable to enhance the corrosion resistance of the epoxy matrix. The impedance, anticorrosion, and adhesion properties of epoxy nanocomposites were found to be better than those of the thermoplastic materials. Despite the success of nanocarbon nanocomposites in aerospace applications, thorough research efforts are still needed to design high-performance anti-rusting materials to completely replace the use of metal components in the aerospace industry. Full article

Solvothermal synthesis of mesoporous materials based on amphiphilic molecules as structure-directing agents can be enhanced using non-conventional technologies for stirring and thermal activation. Here, we disclose a green synthesis approach for the preparation of cerium-modified hexagonally ordered silica sieves. Ultrasound micromixing enabled us to obtain well-dispersed Ce in the self-assembled silica network and yielded ordered materials with high cerium content (Ce/Si molar ratio = 0.08). Microwave dielectric heating, applied by an innovative open-end coaxial antenna, was used to reduce the overall hydrothermal synthesis time and to improve the surface area and textural properties. These mesoporous materials were used as a Ni catalyst support (10 wt.% metal loading) for the ethanol steam reforming reaction. The new catalysts featured complete ethanol conversion, high H₂ selectivity (65%) and better stability, compared to the same catalyst prepared with magnetic stirring and conventional heating. The Ce-promoted silica sieves offered a suitable support for the controlled growth of nanocarbon that does not result in catalyst deactivation or poisoning after 6 h on stream. Full article

Heavy metal pollution in agricultural soil is a serious problem, which threatens the environment and human safety. In this study, the effects of biochar (BC), activated carbon (AC), and nanocarbon (NC) on the growth of peach trees under chromium (Cr) stress were investigated through pot experiments. The experimental results showed that under Cr stress, BC, AC, and NC could increase the soil nutrient content and enhance the soil enzyme activity. Moreover, all carbon forms promoted the conversion of Cr speciation; decreased the content of exchangeable (EXE), carbonate-bound (CARB), and iron–manganese-oxide-bound (FeMnO) Cr in the soil; increased the organic-bound (Org) and precipitated (Pre) Cr content; and reduced Cr availability. After BC, AC, and NC treatment, the content of Org-Cr in the soil increased by 86.05%, 72.97%, and 65.02%; the content of EXE-Cr decreased by 75.30%, 75.33%, and 73.10% compared with the control under severe Cr treatment, respectively. Moreover, the accumulation of Cr in plants decreased by 29.70%, 22.07%, and 20.52%, respectively. At the same time, these three carbons reduced the accumulation of Cr in various parts of the peach tree, alleviated the oxidative damage caused by Cr stress, effectively protected the photosystem of the leaves, improved the photosynthetic capacity, and promoted the growth of the peach tree. Compared with the control, the dry matter accumulation increased by 20.81%, 9.54%, and 6.95% with BC, AC, and NC treatment under severe Cr treatment. Therefore, BC, AC, and NC can all effectively alleviate soil Cr toxicity, and BC has the best effect, which can be popularized in production. Full article

Novel hybrid carbon–mineral materials were synthesized by the mechanochemical activation of a mixture of tannin and bentonite in a ball mill with further pyrolysis in an argon atmosphere at 800 °C. The influence of the initial mixture ingredients content on the structural, textural, and thermal characteristics of biochars has been described using X-ray diffraction, Raman and Fourier-transform infrared spectroscopy, nitrogen adsorption–desorption, and scanning electron microscopy. The influence of bentonite clay on the carbon phase characteristics due to the formation of more heat-resistant and structured nanocarbon particles in biochars has been proven. The adsorption effectiveness of the materials towards methylene blue was studied. The adsorption data were analyzed applying Langmuir and Freundlich isotherms with high determination coefficients (R²) in the range of 0.983–0.999 (Langmuir) and 0.783–0.957 (Freundlich). The maximum adsorption amount of MB was 5.78 mg/g. The adsorption efficiency of biochars with respect to phenol was also examined. It was shown that the hybrid biochars show differentiated selectivity to the adsorption of organic compounds. It was concluded that the physicochemical properties of the surface of biochars play an important role in the adsorption effectiveness, making them a good candidate for water and wastewater remediation processes. Full article