碳纳米管表面化学镀Co的研究

碳纳米管因其优异的力学、物理性能,是一种理想的复合材料增强体,但其与基体金属的润湿性较差.通过对镀钴前碳纳米管的微波、氧化、敏化和活化处理,改善了碳纳米管的表面性能并在碳纳米管表面增加了活化点,成功地在碳纳米管表面镀上一层较为连续的金属钴,以改善碳纳米管与金属基体的润湿性,增强与金属基体的界面结合力.并用XRD、TEM对镀钴后的碳纳米管进行了表征.     

Thermophysical and Magnetic Properties of Carbon Beads Containing Cobalt Nanocrystallites

Magnetic Co-beads were fabricated in the course of a three-step procedure comprising preparation of a metal–acrylamide complex, followed by frontal polymerization and finally pyrolysis of the polymer. The composites obtained were composed of cobalt nanocrystallites stabilized in a carbon matrix built of disordered graphite. The crystallite size, material morphology, fraction of the magnetic component, and thus the magnetic properties can be tailored by a proper choice of the processing variables. The samples were subjected to an alternating magnetic field of different strengths (H = 0 to 5 kA · m⁻¹) at a frequency of f = 500 kHz. From the calorimetric measurements, we concluded that the relaxation processes dominate in the heat generation mechanism for the beads pyrolyzed at 773 K. For the beads pyrolyzed at 1073 K, significant values of magnetic properties, such as the coercive force and remanence give substantial contribution to the energy losses for hysteresis. The specific absorption coefficient (SAR) related to the cobalt mass unit for the 1073 K pyrolyzed beads (SAR = 1340   W ·g^-1 _cobalt){({\it SAR} = 1340 \, \, {\rm W} \cdot {\rm g}^{-1 }_{\rm cobalt})} is in very good conformity with the results obtained by other authors. The effective density power loss, caused by eddy currents, can be neglected for heating processes applied in magnetic hyperthermia. The Co-beads can potentially be applied for hyperthermia treatment.     

锂空气电池用碳纳米管/钴锰氧化物复合电极材料的制备及电化学性能

采用沉淀法合成了不同钴锰含量的碳纳米管(CNTs)/钴锰氧化物纳米复合材料. 利用XRD、SEM、TEM、BET和FT-IR等方法对材料进行了表征, 考察了不同复合材料对锂空气电池放电及充电过程的影响, 同时对循环性能进行了研究. 结果表明: 钴锰比例为4:0与0:4时, 产物为CNTs/Co₃O₄与CNTs/Mn₃O₄, 钴锰比例为3:1、2:2、1:3时, 产物为CNTs/(Co, Mn)(Co, Mn)₂O₄。产物具有良好的分散性能, 氧化物负载在碳管表面, 其中CNTs/Mn₃O₄的分散性能最好。随着锰含量的增加, 电池的放电性能提高, CNTs/Mn₃O₄的放电电压达到2.92 V。随着钴含量的增加, 电池的充电性能提高, 充电电压最低为3.80 V。钴锰比为3:1时的产物充放电过电势(△V)仅为1.05 V, 5次循环后依然保持着良好的放电性能。     

Stabilising Cobalt Sulphide Nanocapsules with Nitrogen-Doped Carbon for High-Performance Sodium-Ion Storage

Conversion-type anode materials with a high charge storage capability generally su er from large volume expansion, poor electron conductivity, and sluggish metal ion transport kinetics. The electrode material described in this paper, namely cobalt sulphide nanoparticles encapsulated in carbon cages(Co9S8@NC), can circumvent these problems. This electrode material exhibited a reversible sodium-ion storage capacity of 705 mAh g^-1 at 100 mA g^-1 with an extraordinary rate capability and good cycling stability. Mechanistic study using the in situ transmission electron microscope technique revealed that the volumetric expansion of the Co9S8 nanoparticles is bu ered by the carbon cages, enabling a stable electrode–electrolyte interface. In addition, the carbon shell with high-content doped nitrogen significantly enhances the electron conductivity of the Co9S8@NC electrode material and provides doping-induced active sites to accommodate sodium ions. By integrating the Co9S8@NC as negative electrode with a cellulose-derived porous hard carbon/graphene oxide composite as positive electrode and 1 M NaPF6 in diglyme as the electrolyte, the sodium-ion capacitor full cell can achieve energy densities of 101.4 and 45.8 Wh kg^-1 at power densities of 200 and 10,000 W kg^-1, respectively.     

镀钴碳纳米管的制备及其电磁特性

在碳纳米管表面镀覆磁性金属粒子,可获得电磁性能优异的复合材料.对碳纳米管进行预处理,再用化学镀法在其表面包覆钴金属制备碳纳米管-维复合材料.用透射电子显微镜(TEM)、能谱仪、振动样品磁强计、矢量网络分析仪分析了复合材料的形貌、成分及电磁性能,并研究了化学镀工艺对镀层沉积速率的影响.结果表明:镀覆后碳管表面包覆了一层钴...     

Co修饰的碳载Pt纳米粒子催化剂的制备与表征

质子交换膜燃料电池阴极需要使用高活性的电催化剂来加速氧还原反应(ORR)速率,而提高活性成分贵金属铂(Pt)的功能反应利用率可解决其关键问题.本工作利用过渡金属钴Co(Ⅱ)?有机框架(Co?MOF)为前驱体合成ORR催化剂载体Co/C,并采取浸渍?液相还原法负载Pt纳米粒子制备了合金Pt?Co/C催化剂.通过对样品的孔隙结构、物相结构、微观形貌等表征,证实了载体Co/C具有较大的比表面积和相互连通的分级介孔结构,其独特的形貌、丰富的孔隙结构使负载的Pt纳米颗粒均匀分布、粒径范围窄,平均粒径约为6.8 nm.进一步对催化剂进行电化学性能评价,其电化学活性表面积(ECSA)接近于商用Pt/C催化剂的值,结果表明合金催化剂中活性成分Pt具有较高的利用率,同时还表现出载体独特的孔隙结构优势.     

聚碳硅烷/纳米钴粉的热裂解研究

本文运用ＩＲ、ＸＲＤ和ＴＧ等分析手段研究了掺混纳米钴粉的聚碳硅烷的热裂解过程。发现热裂解过程可分为有机硅聚合物转化为无机无定形态和无定形态生长为微晶态两个过程，较慢的升温速率有利于得到高的陶瓷产率。钴在热裂解产物中的主要存在形态是ＣｏＳｉ。纳米钴粉的引入促进了热裂解过程中β－ＳｉＣ晶粒的生长，对其催化机理做了初步探讨。     

Electrochemical Properties of Carbon Electrodes Modified with Cobalt Hexacyanoferrate and Nickel Hexacyanoferrate Nanoparticles

Inorganic Materials - C/KCoHCF-1, C/KNiHCF-2, C/KNiCoHCF-3, and C/KCoNiHCF-4 composite materials have been produced via surface modification of activated carbon. Structural characteristics of the...     

Carbon Nanotubes Prepared by Catalytic Decomposition of Benzene Over Silica Supported Cobalt Catalysts

Carbon nanostructures were prepared by catalytic decomposition of benzene on Co/SiO₂ catalysts at 873 K. As a function of particle size and reactive mixture, carbon filaments and nanotubes were obtained and various shapes observed such as straight, curved and helically-coiled nanotubes. Particularly, it was shown that the helically-coiled nanotubes do not present an ordered atomic structure as it was predicted theoretically. However, the active catalytic particle as well as the reactive environment may play an important role in the growth of such nanostructures.     

Strongly Coupled Nickel–Cobalt Nitrides/Carbon Hybrid Nanocages with Pt‐Like Activity for Hydrogen Evolution Catalysis

Designing non‐precious‐metal catalysts with comparable mass activity to state‐of‐the‐art noble‐metal catalysts for the hydrogen evolution reaction (HER) in alkaline solution still remains a significant challenge. Herein a new strongly coupled nickel–cobalt nitrides/carbon complex nanocage (NiCoNzocage) is rationally designed via chemical etching of ZIF‐67 nanocubes with Ni(NO₃)₂ under sonication at room temperature, following nitridation. The as‐prepared strongly coupled NiCoN/C nanocages exhibit a mass activity of 0.204 mA µg^?1 at an overpotential of 200 mV for the HER in alkaline solution, which is comparable to that of commercial Pt/C (0.451 mA µg^?1). The strongly coupled NiCoN/C nanocages also possess superior stability for the HER with negligible current loss under the overpotentials of 200 mV for 10 h. Density functional theory (DFT) calculations reveal that the excellent HER performance under alkaline condition arises from the robust Co²⁺→Co⁰ transformation achieved by strong (Ni, Co)? N‐bonding‐induced efficient d‐p‐d coupled electron transfer, which is a key for optimal initial water adsorption and splitting. The high degree of amorphization urges the C‐sites to be an electron‐pushing bath to promote the inter‐layer/sites electron‐transfer with loss of the orbital‐selection‐forbidden‐rule, which uniformly boosts the surface catalytic activities up to a high level independent of the individual surface active sites.     

Implanting Atomic Cobalt within Mesoporous Carbon toward Highly Stable Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries hold great promise to serve as next‐generation energy storage devices. However, the practical performances of Li–S batteries are severely limited by the sulfur cathode regarding its low conductivity, huge volume change, and the polysulfide shuttle effect. The first two issues have been well addressed by introducing mesoporous carbon hosts to the sulfur cathode. Unfortunately, the nonpolar nature of carbon materials renders poor affinity to polar polysulfides, leaving the shuttling issue unaddressed. In this contribution, atomic cobalt is implanted within the skeleton of mesoporous carbon via a supramolecular self‐templating strategy, which simultaneously improves the interaction with polysulfides and maintains the mesoporous structure. Moreover, the atomic cobalt dopants serve as active sites to improve the kinetics of the sulfur redox reactions. With the atomic‐cobalt‐decorated mesoporous carbon host, a high capacity of 1130 mAh g_S^?1 at 0.5 C and a high stability with a retention of 74.1% after 300 cycles are realized. Implanting atomic metal in mesoporous carbon demonstrates a feasible strategy to endow nanomaterials with targeted functions for Li–S batteries and broad applications.     

碳/碳复合材料基体用中间相沥青

中间相沥青具有高残碳率、高密度、低的密度变化及易石墨化等优点 ,是较理想的碳 /碳 (C/C)复合材料基体前驱体。本文从 C/ C复合材料制备工艺的角度 ,阐述了制备 C/ C复合材料用的中间相沥青的主要特性 ,其中包括中间相沥青的流动性、在碳化过程中的稳定化、微观结构以及中间相沥青基 C/ C复合材料的界面结构。     

Co@CNT复合电磁波吸收剂的制备及其吸波性能

以石墨相氮化碳(g-C₃N₄)和六水合硝酸钴为原料制备Co@CNT复合电磁波吸收剂,调节Co元素含量以提高其电磁波吸收性能。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、拉曼光谱、扫描电镜(SEM)、能谱分析(EDS)和透射电镜(TEM)等手段表征其微结构和物相组成,使用矢量网络分析仪测量复合物电磁参数并进行Matlab模拟得到反射损耗图。结果表明,Co@CNT-1与石蜡质量比为1：3的材料,其吸波性能最优,厚度为4.1 mm时对电磁波的吸收最强,最小反射损耗(RL_min)为-45.5 dB;厚度仅为1.5 mm的材料,有效吸收带宽(RL<-10 dB)最大为4.42 GHz。     

Highly Efficient Carbon Dioxide Hydrogenation to Methanol Catalyzed by Zigzag Platinum–Cobalt Nanowires

Carbon dioxide (CO₂) hydrogenation is an effective strategy for CO₂ utilization, while unsatisfied conversion efficiencies remain great challenges. It is reported herein that zigzag Pt–Co nanowires (NWs) with Pt‐rich surfaces and abundant steps/edges can perform as highly active and stable CO₂ hydrogenation catalysts. It is found that tuning the Pt/Co ratio of the Pt–Co NWs, solvents, and catalyst supports could well optimize the CO₂ hydrogenation to methanol (CH₃OH) with the Pt₄Co NWs/C exhibiting the best performance, outperforming all the previous catalysts. They are also very durable with limited activity decays after six catalytic cycles. The diffuse reflectance infrared Fourier transform spectroscopy result of CO₂ adsorption shows that the Pt₄Co NWs/C undergoes the adsorption/activation of CO₂ by forming appropriate carboxylate intermediates, and thus enhancing the CH₃OH production.     

炭/炭复合材料纤维束界面层的形成过程

通过对炭/炭复合材料纤维束界面不同成型阶段结构和性能的研究, 探索束界面在制备过程中的形成规律. 采用顶出实验、SEM、Micro-CT、XRD以及Raman对不同成型阶段的炭/炭复合材料中纤维束/基体界面剪切强度、界面层结构进行了分析. 结果发现材料密度较低时, 石墨化程度增加不利于束界面剪切强度的提高; 随着材料密度的增大, 束界面剪切强度明显升高. 通过对其界面结构进行分析, 可以看出在沥青浸渍、炭化和石墨化的制备过程中, 炭基体优先在束内形成, 然后逐步向束界面层及束间空间发展, 最后束界面层组织结构趋于完善. 随着热处理温度的升高, 其界面层组织结构的石墨化程度逐渐增强, 其结晶程度也不断增强.