近年来，光热驱动的海水淡化技术被认为是最具潜力的解决当下全球淡水资源短缺难题的方法之一。其中，太阳能界面水蒸发（SVG）是海水淡化效率的核心过程，其利用了太阳能作为唯一的能源输入，是保证光热海水淡化技术具有能量转换效率高、设备简单、成本效益高的关键。在所有高效SVG候选材料中，三维整体式碳基光热转换材料具有成本低、吸光效率高、结构可调性好、水蒸发速率高、无二次污染等优点。基于此，本综述首先简述了SVG 的基本原理，以此为依据介绍了高效 SVG 材料的工作机制和设计原则，最后系统归纳和概述了四种不同类型的三维整体式碳基光热转换材料的研究进展。所以本综述为未来三维整体式碳基光热转换材料的构建及其在SVG领域的应用研究提供理论基础和研究指导。
The mesophase-pitch-based carbon fibers (MPCFs) were prepared though controlling spinning temperature under a constant extrusion quantity using an industrial equipment in order to investigate the influence of spinning temperature on their microstructure mechanical properties and thermal conductivities. The results show that the microstructure of MPCFs shifts from ‘folded radial-split’ structure to ‘radial-split’ structure and presents a better graphite microcrystalline development as the spinning temperature increasing from 309 °C to 320 °C. Meanwhile, the thermal conductivity and tensile strength increase from 704 W·m−1·K−1 and 2.16 GPa to 1078 W·m−1·K−1 and 3.23 GPa, respectively. The lower viscosity of mesophase pitch and the weaker die-swell effect at the spinneret in the higher spinning temperature contribute to maintaining the orientation of mesophase pitch molecule forming in the spinneret, which plays a positive role in preparing MPCFs with larger crystal size and higher crystal orientation.
The high power density and excellent cyclic performance of micro-supercapacitors (MSCs) have garnered significant interest and offer a broad array of potential applications. However, there are still challenges in preparing MSCs electrodes with extremely high area capacitance and energy density. In this study, reduced graphene oxide aerogel (GA) and MoS2 were used as materials, combined with 3D printing and surface modification methods, and MSCs electrodes with ultra-high area capacitance and energy density were successfully constructed. Through 3D printing technology, we obtained electrodes with stable macro structure and GA crosslinked micropore structure. In addition, we used the solution method to load molybdenum disulfide nanosheets on the surface of the 3D printed electrode, further improving the electrochemical performance. The surface capacitance of the prepared electrode reached 3.99 F cm−2, the power density was 194 µW cm−2, and the energy density was 1997 mWh cm−2, showing excellent electrochemical performance and cycle stability. This research provides a simple and efficient method for preparing micro supercapacitor electrodes with high surface capacitance and high energy density, making them ideal for portable electronic devices. This research has important innovative significance in the field of MSCs electrodes.
It is meaningful to find a toughener with a low dosage and effective improvement of interlaminar toughness in carbon fiber composites. In this paper, the toughening effect of phenolphthalein-based poly (ether sulfone) (PES-C) on E51/ DETDA epoxy and its carbon fiber composites (CFCs) was investigated. The SEM results showed that PES-C/epoxy blends formed sea-island phase and bicontinuous phase structure, which were associated with reaction-induced phase separation. After adding 15 phr PES-C, the glass transition temperature (Tg) of blends was increased by 51.5 °C. Meanwhile, the flexural strength, impact strength and fracture toughness of the blends were improved by 41.1%, 186.2% and 42.7%, respectively. These improvements could be attributed to the phase separation structure of the PES-C/epoxy system. Moreover, PES-C film was used to improve the mode-II fracture toughness (GIIC) of CFCs. GIIC value of the 7 μm PES-C film toughened laminate was improved by 80.3% than that of control laminate. The increase in GIIC could be attributed to cohesive failure and plastic deformation in the interleaving region.
Interfacial adhesion between carbon fiber (CF) and polyetherketoneketone (PEKK) is a key factor that affects the mechanical performances of their composites. Therefore, it is of great importance to impregnate PEKK into CF bundles as efficiently as possible. Here we report that owing to the high dissolubility, PEKK can be introduced onto CF surfaces via a wet strategy. The excellent wettability of PEKK guarantees a full covering and tight binding on CFs, making it possible to evaluate the interfacial shear strength (IFSS) with the microdroplet method. Furthermore, the interior of CF bundles can be completely and uniformly filled with PEKK by the solution impregnation, leading to a high interlaminar shear strength (ILSS). The maximum IFSS and ILSS can reach 107.8 and 99.3 MPa, respectively. Such superior shear properties are ascribed to the formation of amorphous PEKK confined in the limited spacing between CFs.
Polyether ether ketone (PEEK) has favorable mechanical properties. However, its high melt viscosity limits its applications because it is hard to process. In this study, PEEK nanocomposites modified with carbon nanotubes (CNTs) and polyether imide (PEI) were prepared using a direct wet powder blending method. The melt viscosity of the nanocomposites decreased by approximately 50%. Under optimal conditions, the addition of CNTs and PEI resulted in a synergistic increase in the toughness of the nanocomposites. The elongation at break increased by 129%, and the fracture energy increased by 97%. The uniformly dispersed CNTs/PEI powder reduces the processing difficulty of PEEK nanocomposites without affecting the heat resistance. The nanocomposites prepared by this method have lower melt viscosity. This improvement of the properties of PEEK would facilitate its use in the preparation of thermoplastic composites by powder impregnation or laser sintering technology.
To obtain excellent carbonaceous precursors, the oxidation reaction mechanism and kinetics of ethylene tar were investigated. The oxidation process of ethylene tar was divided into three stages (350-550 K, 550-700 K and 700-900 K) according to the thermogravimetric curve. To reveal the oxidation reaction mechanism of ethylene tar, the components of evolved gases at different stages were further analyzed online by mass spectrometry and infrared technology. Then, based on the thermogravimetric curve of ethylene tar at different reaction temperatures, the whole reaction process was divided into four parts to perform kinetics simulation calculation. With the help of the iso-conversional method (Coats-Redfern) to analyze the linear regression rates (R2) between 17 common reaction kinetics models and experimental data, the optimal reaction kinetics model for expressing oxidation process of ethylene tar was determined. The results show that: (1) In the oxidation process, the side chains of aromatic compounds firstly react with oxygen to form alcohols and aldehydes, leaving peroxy-radicals to aromatic rings. After that, the aromatic compounds with peroxy-radicals undergo polymerization/condensation reaction to form larger molecular. (2) The fourth-order of reaction model is adopted to describe the first three parts of the oxidation process, and the activation energies are 47.330 kJ·mol−1, 18.689 kJ·mol−1 and 9.004 kJ·mol−1 respectively. The three-dimensional diffusion model is applied to the fourth part of the oxidation process, and the activation energy is 88.369 kJ·mol−1.
锂硫电池因其高能量密度和低成本而成为最有发展前景的电化学储能器件之一。然而，多硫化物的“穿梭效应”、硫导电率低是锂硫电池商业化进程面临的主要挑战。本工作中，以九水合硝酸铁（Fe(NO)3·9H2O）为铁源，氟化铵（NH4F）为表面活性剂，通过简单的水热及煅烧处理制备了Fe2O3纳米棒修饰炭布（CC）的柔性Fe2O3/CC复合材料。其中，Fe2O3中介孔的存在有利于电解质的渗透和充放电过程中锂离子的传输和扩散，同时其密集阵列暴露出的丰富活性位点可以实现多硫化物的高效吸附和快速转化，降低多硫化物的穿梭效应。电化学分析显示：Fe2O3/CC正极在0.1 C（1 C=1672 mA g−1）的电流密度下具有1250 mAh g−1的高放电比容量，经过100圈循环后比容量保持在789 mAh g−1。在2 C的倍率下循环1000圈后仍能实现576 mAh g−1的放电比容量，容量保持率为70%，明显优于对比样品。上述结果表明，Fe2O3/CC能够很好地抑制多硫化物的穿梭，提高电池倍率性能和循环稳定性。
Designing efficient and robust catalysts for hydrogen evolution reaction (HER) is imperative for saline water electrolysis technology. Herein, NC@CoxP@NF catalyst composed of CoxP nanowires array cooperated with N-doped carbon nanosheets (NC) on Ni foam (NF) has been fabricated through in-situ growth strategies. In the preparation process, Co(OH)2 nanowires were in-situ transformed into Co-MOF nanosheets on NF via the dissolution-coordination process of endogenous Co2+ and 2-methylimidazole. Cactus-like microstructure endows NC@CoxP@NF with the exposure of abundant active sites and ion transport channels, promoting the HER catalytic reaction kinetics. Furthermore, the alternating growth of nanowires and free-standing nanosheets in hierarchical interconnected NC@CoxP@NF, further strengthening its structural stability. Most importantly, the formation of surface polyanions (phosphate) and NC nanosheets protective layer improve the anti-corrosive properties of catalysts. Ultimately, the NC@CoxP@NF-10 shows excellent performance, requiring the overpotentials of 107 and 133 mV for HER to achieve 10 mA cm−2 in 1.0 M KOH and 1.0 M KOH + 0.5 M NaCl, respectively. This in-situ transformation strategy provides new ideas to construct the highly-efficient HER catalysts for saline water electrolysis.