Carbon Letters最新文献

Crystallinity has long been regarded as the hallmark of carbon fiber thermal stability; however, our findings reveal that increased structural order does not invariably translate to enhanced thermal resistance. In this study, we graphitized PAN-based carbon fibers up to 2700 °C and performed a comprehensive multiscale analysis of their structure and oxidation behavior, challenging the conventional assumption that greater crystallinity guarantees better thermal stability. Heat treatment did improve the graphitic alignment, microvoid evolution, and tensile modulus across all samples. Yet under oxidative conditions, a surprising reversal was observed: among T300B, T700S, and T800H, the least graphitized fiber (T300B) exhibited the highest thermal resistance, outperforming its high-modulus counterparts. This unexpected behavior is attributed to a dual mechanism: once thermal conductivity exceeds a critical threshold it accelerates oxidative degradation, while pronounced radial heterogeneity (skin–core transition zones) in the fiber structure impedes heat and oxygen penetration. These findings reshape the design paradigm for high-performance carbon fibers. They suggest that maximizing crystallinity alone is insufficient; instead, controlling thermal transport properties and internal structural gradients in tandem is crucial for engineering fibers capable of withstanding extreme oxidative environments.

This study evaluates underwater non-thermal plasma (UNTP) as a reagent-free process for the complete mineralization of oxalic acid, a major chelating agent in nuclear decontamination effluents. Quantitative assessment was based on total organic carbon (TOC) removal and stable carbon isotope tracing with uniformly labeled ¹³C-oxalic acid. TOC and ion chromatography (IC) analyses demonstrated complete mineralization within 60 min at ≤ 300 ppm (k = 0.120, 0.100, 0.042 min⁻¹; t₉₀ = 19.2, 23.0, 55.0 min), whereas at 450 ppm partial mineralization remained (TOC 25.4 mg C/L after 60 min). At higher concentrations (1000–2000 ppm), TOC removal was restricted to 25–57% with rate constants decreasing to 0.008 and 0.003 min⁻¹ (t₉₀ = 288, 767 min); at 3000 ppm, reaction nearly stagnated (k = 0.0009 min⁻¹; t₉₀ ≈ 2558 min). Energy yield peaked at low/intermediate concentrations (0.9–1.3 g-C kWh⁻¹; 1.1 g-C kWh⁻¹ at 450 ppm) but declined to 0.9, 0.3, and 0.2 g-C kWh⁻¹ at 1000, 2000, and 3000 ppm. Mechanistic profiling showed that both glyoxylic and formic acids remained below the method detection limits (LOD) throughout the treatment period, supporting that a predominantly direct mineralization pathway to CO₂ was operative. Critically, ¹³C tracer experiments (300 ppm, 60 min) yielded δ¹³C = + 5702‰ (~ 7.0 atom % ¹³C), confirming the presence of substrate-derived carbon in the evolved CO₂. No solids or carbonate byproducts were detected, consistent with a nearly closed carbon balance. Bulk temperatures remained ≤ 40 °C under all conditions, confirming non-thermal operation. These findings establish TOC-based kinetics and isotopic evidence of oxalic acid mineralization, define a practical operating window (≤ 2000 ppm), and support UNTP as a sustainable route for treating chelating agents in decontamination effluents.

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The inherent non-degradation and potential toxicity of pure carbon nanomaterials in vivo remain the main obstacles to clinical translation. This study attempts to prepare a novel biodegradable caramelized hollow mesoporous carbon nanospheres (CHMCNs) with mesoporous shells and a large cavity, which can be decomposed into small particles (~ 5 nm) within 7 days under physiological conditions. By varying the synthesis parameters and templates, CHMCNs with different morphologies can be obtained to meet different application requirements. Meanwhile, CHMCNs exhibit excellent biocompatibility and high drug-loading efficiency, enabling effective delivery of anticancer drugs (DOX) into cells. In addition, due to the good photothermal efficiency (PTT, 29.7%), CHMCNs facilitate pH/NIR dual-responsive drug release under NIR irradiation, resulting in an excellent synergistic chemo-photothermal therapy effect. The results indicate that CHMCNs is a promising drug delivery carrier. In conclusion, this work addresses the non-degradable defects of traditional mesoporous carbon nanomaterials (MCN) and proposes a novel nanocarrier system for tumor treatment.

An appropriate combination of electrode-electrolytes has the competence to augment the supercapacitive behaviour to a greater range of excellence. Following this, a binary polymeric composite PPy/o-CNTs (PC) has been synthesized via in-situ chemical oxidative polymerization of polypyrrole (PPy) in the presence of oxidized carbon nanotubes (o-CNTs) and its electrochemical performance has been evaluated in difference electrolytic environments viz. 1/2/3 M KCl and 1/2/3 M H₂SO₄. The composite PC elucidated the highest specific capacitance of 364.5 F g^− 1 (at 100 mV s^− 1) and 487.4 F g^− 1 (at 1 A g^− 1) in 3 M KCl and 729.9 F g^− 1 (at 100 mV s^− 1) and 559.7 F g^− 1 (at 1 A g^− 1) in 3 M H₂SO₄ respectively. The synthesized composite also showed significantly improved cyclic behaviour with capacitance retention up to 94.65% in 2 M KCl for 2000 GCD cycles. The improved electrochemical performance of PC could be attributed to the presence of o-CNT which not only provided a conductive network throughout the electrode materials to facilitate charge transfer kinetics but also provided a mechanically stable support thereby anchoring the polymeric chain to enhance the overall cyclic stability. Further, the lower value of solution resistance and charge transfer resistance also affirmed the ameliorated supercapacitive behaviour of PC.

A sustainable and cost-effective approach was developed for synthesizing carbon nanostructures namely carbon nanotubes (CNTs), carbon spheres (CSs), and carbon fibers (CFs). The process employed pyrolyzed hydrochar derived from treated rice straw, kaolin, zeolite or hydrochar as supports for Fe–Ni bimetallic catalysts, while hydrochar, camphor, or cotton fiber served as carbon sources. The resulting nanostructured materials were characterized using FE-SEM, XRD, FTIR, and N₂ adsorption analyses. These tools demonstrated that morphology and structure of the carbon materials produced are governed by the carbon precursor, catalyst support, and catalyst-carbon interactions. The resultant carbon nanostructures have distinctive graphitic characteristics and surface functions that improve adsorption performance. The adsorption performance of the synthesized nanostructures was evaluated using methylene blue (MB) as a model pollutant. Among them, CNTs exhibited the highest adsorption capacity (~ 130 mg/g), which was attributed to its a large specific surface area and abundant π–π interaction sites. Adsorption behavior of MB dye followed the Langmuir isotherm and pseudo-second-order kinetic models, indicating monolayer chemisorption with multiple rate-controlling steps. This work highlights an efficient route for valorizing agricultural waste into functional carbon nanostructures for wastewater remediation.

As the global need for clean and sustainable energy sources grows, research into alternatives to fossil fuels has intensified. Metal halide perovskite solar cells (PSCs) stand out among new photovoltaic technologies due to their impressive efficiencies and cost-effective, solution-based production. However, their long-term instability poses a significant challenge to their commercialization. This review offers a thorough examination of recent advancements in improving PSC performance by incorporating carbon-based materials, such as carbon dots, carbon nanotubes, graphene, and carbon black into various components of the devices. These materials provide distinct benefits, including outstanding chemical stability, high electrical conductivity, environmental durability, and compatibility with scalable manufacturing methods. By evaluating synthesis methods, interfacial engineering techniques, and performance results, this article demonstrates how carbon materials can enhance device efficiency, mechanical flexibility, and operational stability simultaneously. The review concludes by identifying future opportunities and research directions for carbon-enhanced PSCs, paving the way for cost-effective, durable, and sustainable next-generation solar technologies.

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The rapid increase of global solid waste poses significant environmental challenges. In this work, two abundant wastes—red mud and apple peel—were used as precursors to prepare zero-valent iron biochar for efficient pollutant removal. This study innovatively developed a green, low-temperature in-situ hydrogen reduction strategy via one-step copper-catalyzed ethanol decomposition, which generated in-situ hydrogen and uniformly dispersed high-load Fe⁰ without the need for external hydrogen or hazardous reagents. Compared with N₂ pyrolysis, in-situ H₂ treatment enlarged the pore size by 17.2%, increased surface oxygen functionalities, and enhanced active site exposure and electron transfer, markedly improving reactivity. The composite exhibited high saturation magnetization (33.13 emu g^–1) for rapid magnetic separation, low iron leaching (≤ 0.13 mg L^–1), and retained over 63% removal efficiency after four cycles. Removal efficiencies reached 87.77 − 98.50% for MB, RhB, and TC in single-dye systems, and remained high at 70.09 − 84.32% in multi-dye wastewater. Synergistic mechanisms involving porous adsorption, Fe–O coordination, π–π interaction, and NZVI-mediated reduction contributed to superior performance. This sustainable strategy enhances the waste value and provides effective and environmentally safe solutions for complex wastewater treatment, promoting resource recovery and pollution control.

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The sandwich structure with ceramic matrix composites (CMCs) skin and carbon form (CF) core is the ideal thermal structural components with excellent thermal protective and lightweight properties in hypersonic vehicles. However, the temperature gradient and mismatch of thermal conductivity between CMC skin and CF core result in the thermal stress in sandwich structures. Therefore, core material CF with matching thermal conductivity have become very important to prevent cracks and debonding of the sandwich structure. In this work, carbon nanotubes (CNTs) reinforced carbon foam composites with different microstructure were fabricated using simple phenolic resin foaming followed by CVI process. The prepared CF display a very low density of 0.075 g/cm³ and a relatively high compressive strength of 1.65 MPa. By controlling the distribution position and content of CNTs the thermal conductivity of core materials CF/CNTs (4.93 W·m^− 1·K^− 1 which is ~ 13 times higher than that of CF) can be regulated to compatibility with CMCs skin (3.5 ~ 6.0 W/m·K). And the thermal conductivity evolution mechanisms of the CF/CNTs from room temperature to 1200 ℃ were revealed. High interfacial thermal resistance by phonon scattering between the CF and CNTs blocks the solid conduction of materials at room temperature. With the increase of the temperature, radiative heat transfer between CF and CNTs becomes more violent and dominates the heat transfer path. The C/CMCs-CMCs sandwich structure was fabricated quickly by the in situ foaming method.

In the controlled synthesis of biomass-derived porous carbon materials, effective pretreatment strategies play a critical role in modulating the chemical activation process and optimizing material performance. However, existing studies predominantly focus on the macroscopic structural changes induced by pretreatment, often overlooking the important role of chemical composition evolution during activation. Herein, a coconut shell-based acidic hydrothermal pretreatment was designed to precisely control the evolution of the primary pore structure alongside the enhanced retention of oxygen species in the hydrochar. Subsequent chemical activation successfully yields a high-performance carbon material with a well-defined hierarchical porous structure. This material exhibits a high specific surface area of 1963 m² g⁻¹ and delivers an outstanding specific capacitance of 420 F g⁻¹ at a current density of 0.5 A g⁻¹. When assembled into a solid-state supercapacitor, the device achieves a high energy density of 12.97 Wh kg⁻¹. It also demonstrates excellent cycling stability, retaining 97.02% of its initial capacitance after 10,000 cycles at 10 A g⁻¹, along with a high Coulombic efficiency of 99.84%. Our findings reveal that appropriate acidic hydrothermal pretreatment not only establishes a continuous primary pore network within the precursor—facilitating the deep diffusion and uniform reaction of the activating agent—but also enhances activation efficiency synergistically through the anchoring effect of oxygen species. This work provides new insights and experimental support for the rational design of high-performance biomass-derived carbon materials.

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Rising industrial carbon dioxide emissions necessitate utilization technologies. Carbon dioxide solidification captures carbon dioxide by reacting with alkaline compounds in concrete, improving its properties. This study integrates a life cycle assessment (LCA) model to evaluate carbon reduction potential with Machine Learning (ML) models to predict complex production dynamics. It investigates solidification mechanisms. Results show co-solidification and external solidification achieve reductions of 676.45 and 704.9 kilograms per tonne, respectively, with notable environmental benefits. A comparison of three predictive models, namely Feedforward Neural Networks (FNN), Polynomial Regression, and Support Vector Regression, confirms that FNN is the optimal choice. It exhibits a lower mean absolute error (791) and a higher coefficient of determination (0.91). SHAP analysis revealed that ‘Coal consumption’ and ‘Electricity consumption’ were the primary drivers of the FNN prediction, confirming the model’s reliance on essential energy inputs, while the ‘date’ feature exerted minimum influence. Projections indicate China’s 2024 concrete production emissions could be 4.23 billion tonnes via synergistic curing, versus 4.37 billion tonnes with conventional external curing. Case and visual analyses further validate carbon dioxide curing’s advantages in improving concrete performance and cutting energy use.