Carbon最新文献

The advancement in the miniaturization of carbon aerogels into micro-sized spheres represents a significant development in the creation of ultralight, broadband microwave absorbers. Notwithstanding this innovation, there is still a considerable challenge in optimizing microwave absorption (MA) performance through heterointerface engineering within aerogel microspheres. Herein, we have developed skin-core heterogeneous aerogel microspheres by the in situ generation of ZIF-67 nanocrystals on the wet-spun aramid nanofiber (ANF) aerogel microspheres, followed by a high-temperature carbonization process. The resulting Co@C nanoparticle-enshrouded ANF-derived carbon nanofiber aerogel microspheres (Co@C/CNFAMs) demonstrate an exceptional equilibrium between impedance matching and multi-faceted attenuation. Remarkably, the Co@C/CNFAM2 sample attains a maximum effective absorption bandwidth of 8.72 GHz, while maintaining an ultralow filler proportion of 1.5wt%. Moreover, the Co@C/CNFAM3 sample achieves a minimum reflection loss of − 72.34 dB with a filling ratio of 1.2 wt%. Our findings offer a refined approach to the intricate engineering of heterostructures, along with the strategic macrostructural design, paving the way for the development of aerogel-based microwave absorbers that represent the next step in material science innovation.

The surface conductivity of hydrogen-terminated diamond is a topic of great interest from both scientific and technological perspectives. This is primarily due to the fact that the conductivity is exceptionally high without the need for substitutional doping, thus enabling a wide range of electronic applications. Although the conductivity is commonly explained by surface transfer doping due to air-borne surface acceptors, there remains uncertainty regarding the main determining factors that govern the degree of band bending and hole density, which are crucial for the design of electronic devices. Here, we elucidate the dominant factor influencing band bending by creating shallow nitrogen-vacancy (NV) centers beneath the hydrogen-terminated diamond surface through nitrogen ion implantation at varying fluences. We measured the photoluminescence and optically detected magnetic resonance (ODMR) of the NV centers, as well as the surface conductivity, as a function of the nitrogen implantation fluence. The disappearance of the conductivity with increasing nitrogen implantation fluence coincides with the appearance of photoluminescence and ODMR signals from negatively charged NV centers. This finding indicates that band bending is not exclusively determined by the work-function difference between diamond and the surface acceptor material, but by the finite density of surface acceptors. This work emphasizes the importance of distinguishing work-function-difference-limited band bending and surface-acceptor-density-limited band bending when modeling the surface transfer doping, and provides useful insights for the development of devices based on hydrogen-terminated diamond.

SiO₂/C foams with carbon particles as raw material were prepared using emulsion template combined with SiO₂ sol-gel technology. One significant hurdle lies in achieving scalable and cost-effective fabrication of bulk materials endowed with customized porosity, along with an optimal blend of attributes such as high mechanical strength, super-hydrophilicity, thermal insulation, and effective absorption of electromagnetic waves. SiO₂/C foams with varied pore sizes and porosities were synthesized by manipulating the water-oil volume ratio in the raw materials. The impact of pore size and porosity on the compressive strength, thermal insulation, super-hydrophilicity and electromagnetic wave absorption property of SiO₂/C foam materials were thoroughly investigated. The gel reaction involving inorganic SiO₂ not only could fix the bubbles in situ and impart sufficient mechanical properties but also confer super-hydrophilic characteristics to the SiO₂/C foam materials. The SiO₂/C foams exhibited adjustable porosity levels ranging from 57% to 78%.The SiO₂/C foams, characterized by a uniform pore size of approximately 8.33 μm, demonstrated low thermal conductivity. Additionally, the compressive strength of SiO₂/C foam with a porosity of 57% was measured at 3.5 MPa. For sample S4, the minimum reflection loss (RL_min) of -48 dB with an effective absorption bandwidth spanning 5.76 GHz, observed at a matching thickness of 2.2 mm. Due to their outstanding performances, characteristics, and the ease of scalable fabrication, the SiO₂/C foams developed in this study showcase significant potential for diverse applications.

Carbon fiber-reinforced plastics have become indispensable materials in energy saving and new energy technologies, such as automobiles, wind power generators, and hydrogen tanks for fuel cells. However, the lack of oxidation resistance limits the high-temperature applications of carbon fibers. In this study, we developed a coating technology for carbon fibers to improve their oxidative resistance. Carbon fibers with silicon carbide coatings were obtained by the adsorption of silica colloids on carbon fibers using electro adsorption, followed by heating. The resulting coating has small thickness and strong chemical connections. The thermogravimetric analysis confirmed that the oxidation start temperature of the coated carbon fibers was higher than that of carbon fibers. Moreover, the mechanical properties of the coated carbon fibers were maintained. Therefore, the proposed coating technology can broaden the application of carbon fibers as the alternative to some SiC fiber applications. Further, it is applicable for recycling carbon fibers to increase their value in terms of thermal oxidation stability.

Carbon fiber reinforced composites are sophisticated materials that are blends of carbon fibers (CFs) with a polymer matrix, providing outstanding strength, stiffness, and lightweight properties. Petroleum asphaltenes, the heavy fraction of bitumen, offer high aromaticity and carbon content, making them a cost-effective and promising raw material to produce high-value CFs. This study investigates the utilization and effectiveness of asphaltene-derived carbon fibers (ACFs) in composites produced through additive manufacturing. The composites were 3D printed by incorporating different weight proportions (0%, 2.5%, 5%, and 7.5%) of chopped ACFs (length 3-4 mm, diameter ∼6-12 μm, tensile strength ∼500-1150 MPa, tensile modulus ∼40-90 GPa) without any post-treatment (without surface functionalization and sizing). Extensive characterizations were carried out on both ACFs and their derived composites to evaluate their mechanical (tensile, flexural, hardness, impact, etc.) properties to identify potential applications. Furthermore, the reinforcement ability of ACFs was assessed in contrast to composites produced from expensive commercial carbon fibers derived from polyacrylonitrile. Incorporating 7.5 wt% ACFs into the acrylonitrile butadiene styrene (ABS) matrix enhanced ABS’s flexural and tensile strengths by ∼20% and ∼5%, and its corresponding modulus values by ∼30% and ∼34%, respectively. In addition, ABS's hardness was improved by 31% with the inclusion of 7.5 wt% ACFs. This composite performance by incorporating ACFs is encouraging despite the lower surface roughness and surface energy of ACFs (due to the absence of surface functionalization and sizing) as well as their lower tensile strength and modulus properties as compared to commercial surface-functionalized and sized carbon fibers.

Metal-air batteries require the exploration of affordable electrocatalysts with exceptional catalytic performance for oxygen reduction reactions (ORR). One of the powerful ways to develop highly active and robust oxygen electrocatalysts is to load transition metal compounds onto a highly porous carbon aerogel. Here, we report a cell wall nanoengineeing strategy to transform natural balsa wood into a wood-derived carbon aerogel (WCA), following by loading FeP nanoparticles inside the hierarchical N, P-doped WCA for ORR electrocatalysts. Wood nanotechnology is applied to manipulate the microstructure of the porous carbon aerogel with low-tortuosity, multichannel, and aligned pore, which benefits to the electron transportation for boosting the ORR. Under 0.1 M KOH conditions, the initial potential, half wave potential and limit current of FeP@N,P-WCA are 0.95 V, 0.84 V, and 5.20 mA cm^-2 respectively, which are much higher than that of untreated wood and comparable to commercial Pt/C. The aqueous Zn-air batteries assembled with this catalyst exhibit a remarkable specific capacity of 775.5 mA h g^-1 and better charge-discharge cycling stability. The excellent electrocatalytic activity demonstrated by FeP@N,P-WCA for ORR is attributed to the inherent tri-pathway (lumen, pit, and ray cell) porous structure of wood, the high conductivity and specific surface area of WCA (584.2 m² g^-1), and the highly dispersed FeP nanoparticles. This work provides a structural design concept for achieving high electrocatalytic biobased WCA reactors by combining wood nanotechnology and electrocatalysts chemistry for energy storage and conversion.

Cell migration is a crucial parameter for disease progression in cancer. Reactive oxygen species (ROS) levels are involved in the regulation of the migration process, however, the exact role of free radical generation and where it occurs is unknown. Here we use a diamond-based quantum sensing technique to detect free radicals during cancer cell migration in real time with subcellular resolution. We investigated metastatic MDA-MB-231 human breast cancer cells and observed free radical formation after 16 hours of starvation and 24 h of migration under low-serum conditions. Intracellular diamond dynamics were monitored at different migration points (0, 12, and 24 h), and cell morphology was evaluated. Additionally, the number of focal adhesions was analyzed as an indicator of the migratory potential of the cells. We further measured free radical generation under nicotinamide adenine dinucleotide phosphate hydrogen NADPH oxidases 2 (NOX2) inhibition by apocynin. We found that free radical levels decreased after 24 h treatment with 36 μg/mL apocynin while the levels of ROS and the migratory capacity of the cells increased. Our results evidence the complexity of the redox regulation in migrating cancer cells and offer a novel approach to specifically and locally interrogate pivotal players of the oxidative network behind metastatic success.

This study explores the structural changes of hard carbon (HC) negative electrodes in sodium-ion batteries induced by insertion of Na ions during sodiation. X-ray Raman spectroscopy (XRS) was used to record both C and Na K-edge absorption spectra from bulk HC anodes carbonized at different temperatures and at several points during sodiation and desodiation. Comparing the ${\pi }^{\ast }$${\pi }^{\ast }$/${\sigma }^{\ast }$${\sigma }^{\ast }$ regions in the C K-edge spectra