石墨碎锂电池负极材料包覆炭化的研究

以煤沥青为包覆材料,煤油为溶剂,对除杂整形后的石墨碎进行包覆炭化改性处理,得到的样品进行物理特性分析,并组装电池进行电性能测试。结果表明,随着包覆量的增加,颗粒平均粒度也增加,但增加幅度较小,为1~2μm;样品的比表面积随着包覆量的增加而降低,经过沥青包覆和石墨化后,样品的比表面积由6.715 m~2/g大幅度降低到1.618 m~2/g;振实密度随着包覆量的增加而提高,最高可达1.05 g/cm~3。经过包覆后样品的层间距d002有所增加。包覆后样品的表面逐渐平滑,棱角少,并且炭化后的沥青炭填充了部分石墨颗粒的孔隙,降低了比表面积,未包覆的样品表面粗糙,有较多的沟壑、孔隙。样品随着包覆量的增加,首次放电容量和首次充放电效率都呈现出增加的趋势,首次放电容量由316.56 m A·h/g升至330.82 m A·h/g,首次放电效率由89.09%升至94.45%,当沥青包覆量达10%时,首次放电容量和首次充放电效率均达最大。     

沉积工艺对致密热解炭密度及显微组织的影响

以乙炔、丙烯为碳源气体,采用流化床-化学气相沉积工艺于燃料颗粒表面沉积致密热解炭包覆层,在1 150～1 230℃沉积温度及碳源气体体积分数为7％～21％下开展正交实验,研究沉积温度及碳源气体浓度对致密热解炭密度的影响.采用阿基米德原理测量致密热解炭密度,用场发射扫描电镜观察致密热解炭微观结构.研究结果表明,致密热解炭...     

高温气冷堆包覆燃料颗粒疏松热解炭层包覆工艺研究

疏松热解炭层是高温气冷堆包覆燃料颗粒的主要组成部份，本文介绍了疏松热解炭层对高温气冷堆技术研究和发展的贡献，它在包覆燃料颗粒中的功能及对它的要求，密度低于５０％理论密度的疏松热解炭层的包覆工艺研究和结果。     

树脂包覆对石墨化中间相沥青炭微球电化学性能的影响

以中间相沥青炭微球(SSGMCMB)为核、酚醛树脂(PR)热解炭为壳，采用浸渍一固化一炭化手段制备出树脂热解炭包覆SSGMCMB复合材料，并对其电化学性能进行了研究。通过SEM、XRD、恒电流充放电测试等手段研究了不同树脂包覆量对该复合材料的形态、结构及其电化学行为的影响，结果表明：树脂热解炭对SSGMCMB有较好的包覆作用，保持了SSGMCMB的球形形态，有利于锂离子的嵌入／脱出反应，对其电化学性能有一定的提高，改进了酚醛树脂热解炭有较大电压滞后的问题。     

C/C复合材料中基体炭的微观结构表征

采用扫描电子显微镜、金相偏光显微镜对不同结构基体炭，包括热解炭、沥青炭、树脂炭进行形貌表征和分析。通过试验观察到热解炭的微观结构主要分为粗糙层结构、光滑层结构、过渡层结构和各向同性结构，热解炭表面为球冠形结构；沥青炭的主要形貌结构主要有镶嵌型结构，区域与镶嵌并存结构，区域与流线型并存结构，流线型结构；树脂碳的结构主要为表面光滑的块状结构。     

不同变质程度煤衍生硬炭的储钠行为研究

煤具有碳含量高、芳香结构发达、成本低廉等优点,是制备钠离子电池硬炭负极材料的优质前驱体。然而煤种类繁多且含有无机杂质,不同种煤热解成炭后材料的石墨化度、碳层间距和表面化学组成各异,导致煤基硬炭负极的电化学性能优化难以展开。选择四种不同变质程度的煤,采用酸洗脱灰、高温炭化的方法制备了系列煤基硬炭,研究了变质程度、炭化温度对煤基硬炭微晶结构和表面杂原子组成的影响,并考察了其相应的储钠行为。其中,褐煤1400℃炭化得到的硬炭性能最佳,在0.02 A·g^-1电流密度下表现出338.8 mA·h·g^-1的比容量和81.1%的首次库仑效率。优异的电化学性能归因于褐煤硬炭较大的碳层间距和丰富的储钠缺陷位点,提供了高嵌入和吸附储钠容量。     

石油焦煅烧过程中热解炭膜的形成及其对煅后焦性能的影响

研究了石油焦煅烧过程中煅后焦表面热解炭膜的形成条件和形成原因,对比了不同煅烧方式对热解炭膜形成的影响,同时研究了热解炭膜的形成对煅后焦的沥青浸润性、电阻率、抗氧化性等性质的影响。结果表明:封闭式煅烧有利于热解炭膜的形成,热解炭膜的存在有利于改善沥青对石油焦的浸润性,同时有效抑制了煅后焦的空气反应性、CO2反应性,但热解炭膜的存在却又明显增加了煅后焦的电阻率。     

不同沥青包覆球形天然石墨负极材料结构和性能研究

通过选用3种不同软化点及组分含量的石油沥青,采用固相包覆法对球形天然石墨进行包覆,考察了软化点不同的沥青对包覆后球形天然石墨负极材料的结构和电化学性能的影响。结果表明:高软化点及高TI和QI组分含量的沥青,炭化过程中分子分解聚合反应更为平缓,挥发分气体逸出少,具有更高残炭率,包覆炭化后能在球形天然石墨表面形成致密无定形碳层,改性后的石墨负极材料具有更高的可逆容量和更好的循环性能,经过高软化点沥青包覆后的球形天然石墨样品,常温1 C下循环200次容量保持率由55.8%提升至96%以上。     

流化床中包覆燃料颗粒的制备及应用

包覆燃料颗粒由燃料核芯、疏松热解炭层、内致密热解炭层、碳化硅层和外致密热解炭层组成.本工作设计建造了不同直径和结构的流化床沉积炉系统,探讨了流化床的结构、气体流量对颗粒流化状态的影响采用化学气相沉积方法生产出的包覆燃料颗粒不仅应用于我国10 MW高温气冷堆燃料元件的制备,而且探讨了包覆燃料颗粒的其它应用.     

不同炭基体对炭/炭复合材料力学性能的影响

结合化学气相沉积（CVD）和前驱体浸渍裂解工艺,分别以丙烯、糠酮树脂和煤沥青为前驱体制备了密度在1.85g/cm3以上的三维炭/炭（C/C）复合材料,对比研究了沥青炭、热解炭+沥青炭以及热解炭+树脂炭结构（分别为A、B、C组）的等三种不同炭基体C/C复合材料的增密效率与力学性能,采用排水法表征C/C复合材料的孔隙率及密度,利用扫描电镜进行炭基体的微观结构表征,采用万用电子力学试验机进行拉伸强度、压缩强度、剪切强度等力学性能表征。结果表明,在热解炭质量含量相同的前提下,树脂浸渍裂解增密速率低于沥青浸渍裂解工艺,树脂炭基体孔隙率低于沥青炭基体。不同炭基体结构的C/C复合材料力学性能次序为：热解炭+树脂炭双元炭基体最高,纯沥青炭基体次之,热解炭+沥青炭双元炭基体最低,分析原因为热解炭与树脂炭双元炭基体的界面结合强度高,而沥青炭为混乱无序碳结构,热解炭和沥青炭双元炭基体界面结合强度弱,因此力学强度最低。     

An Sn-Fe/carbon nanocomposite as an alternative anode material for rechargeable lithium batteries

Sn-Fe/carbon nanocomposites were synthesized by the mechanochemical treatment of Sn with various amounts of an Fe/C composite through the pyrolysis of Fe(III) acetylacetonate. The composites were then evaluated as alternative anode materials for rechargeable lithium batteries. Based on the obtained ex situ X-ray diffraction (XRD) data, X-ray absorption spectroscopy (XAS) results, and differential capacity plots (DCPs), a reaction mechanism was suggested. It was found that increasing the amounts of the SnFe phase and pyrolyzed carbon in the composite improved its electrochemical characteristics in terms of its capacity retention.     

Advanced structures in electrodeposited tin base anodes for lithium ion batteries

A novel composite anode material consisted of electrodeposited Sn dispersing in a conductive micro-porous carbon membrane, which was directly coated on Cu current collector, was investigated. The composite material was prepared by: (1) casting a polyacrylonitrile (PAN)/dimethylformamide (DMF) solution that contained silica particles on a copper foil, (2) removing the solvent by evaporation, (3) dissolving the silica particles by immersing the copper foil into an alkaline solution, (4) drying the copper foil coated by micro-porous membrane, (5) electrodepositing Sn onto the copper foil through the micro-pores in the micro-porous membrane, and (6) annealing as-obtained composite material. This method provided the composite material with high decentralization of Sn and supporting medium purpose of conductive carbon membrane deriving from pyrolysis of PAN. SEM, XRD and EDS analysis confirmed this structure. The characteristic structure was beneficial to inhibit the aggregation between Sn micro-particles, to relax the volume expansion during cycling, and to improve the cycleability of electrode. Galvanostatic tests indicated the discharge capacity of the composite material remained over 550 mAh g⁻¹ and 71.4% of charge retention after 30 cycles, while that of the electrode prepared by electrodepositing Sn on a bare Cu foil decreased seriously to 82.5 mAh g⁻¹ and 13%. These results show that the composite material is a promising anode material with larger specific capacity and long cycle life for lithium ion batteries.     

水热法改性凹凸棒石及其吸附性能的研究

分别以葡萄糖和淀粉为碳前驱体,凹凸棒石为原料,水热法制备有机改性凹凸棒石。通过扫描电镜(SEM)、红外吸收光谱(FTIR)、X射线衍射(XRD)以及吸附性能,考察葡萄糖和淀粉对凹凸棒石的形貌和性能的影响。结果表明,在制备改性凹凸棒石的过程中,碳前驱体对产物形貌和吸附性能有着明显的影响。葡萄糖分子在水热条件下碳化为直径50 nm碳颗粒,均匀负载在凹凸棒石表面,复合材料中含有─CH有机官能团;淀粉碳化为直径40~80 nm的碳球,不均匀的负载在凹凸棒石的表面,且表面含有─CH有机官能团。采用葡萄糖和淀粉为碳源的有机改性凹凸棒石对苯酚的去除率分别为70%和46%,分别是纯凹凸棒石对苯酚去除率的4倍和2.5倍。     

短碳纤维增强铝基复合材料

通过化学镀再电镀的方法,在碳纤维表面镀上Cu镀层,制备C/Cu复合丝,并在硼酸的保护下,利用非真空条件下的液态机械搅拌法制备短碳纤维增强铝基复合材料,研究了碳纤维在复合材料中的分散程度,铜镀层存在状态及C/Al复合材料的拉伸性能.实验结果表明：在硼酸存在下,大大降低了铜的氧化程度,碳纤维分散均匀且没有损伤,少量硼酸的加入,对复合材料的力学性能没有影响,该复合材料的抗拉强度随碳纤维含量的增加而增加,其抗拉强度较基体材料提高50%以上,但塑性指标却明显下降.     

Preparation, electrical and elastic properties of new anisotropic expanded graphite-based composites

New composite materials with application to catalyst supports or adsorbents are presented. They are made of compressed expanded graphite of various densities first impregnated by polyfurfuryl alcohol and next pyrolyzed and activated. The resultant materials are monoliths comprising a graphite backbone coated by a thin layer of active carbon. The electrical conductivity and the dynamic elastic moduli are measured on each kind of material, namely before and after carbonization, and finally after activation. The results are shown to be consistent with a percolation phenomenon: the conductivity and the rigidity thresholds are derived, and several theoretical considerations and comparisons with pure expanded graphite are made. The discussion leads to a better understanding of the structure of the materials before and after impregnation, namely the graphite backbone and the graphite-polymer or carbon composites. Besides, their conductive and elastic properties are shown to be very good. Hence, the materials are expected to have fair thermal conductivities, to be electrically regenerable (application as adsorbents) and to have an interesting life time (application as catalyst supports).     

Improved graphitization and electrical conductivity of suspended carbon nanofibers derived from carbon nanotube/polyacrylonitrile composites by directed electrospinning

Single suspended carbon nanofibers on carbon micro-structures were fabricated by directed electrospinning and subsequent pyrolysis at 900 °C of carbon nanotube/polyacrylonitrile (CNT/PAN) composite material. The electrical conductivity of the nanofibers was measured at different weight fractions of CNTs. It was found that the conductivity increased almost two orders of magnitude upon adding 0.5 wt.% CNTs. The correlation between the extent of graphitization and electrical properties of the composite nanofiber was examined by various structural characterization techniques, and the presence of graphitic regions in pyrolyzed CNT/PAN nanofibers was observed that were not present in pure PAN-derived carbon. The influence of fabrication technique on the ordering of carbon sheets in electrospun nanofibers was examined and a templating effect by CNTs that leads to enhanced graphitization is suggested.     

Nano-porous Si/C composites for anode material of lithium-ion batteries

Nano-porous silicon composite incorporated with graphite and pyrolyzed carbon was synthesized and investigated as a promising anode material for lithium-ion batteries. The nano-porous Si/graphite composite was prepared via two-step ball-milling followed by etching process. Then carbon was incorporated by using different approaches. The nano-porous Si/graphite/C composite exhibits a reversible capacity of about 700 mAh/g with no capacity loss up to the 120th cycle at a constant current density of 0.2 mA/cm². The superior electrochemical characteristics are attributed to the nanosized pores in Si particles, which suppress the volume effect, and buffering action as well as excellent electronic and ionic conductivity of carbon materials.     

Chemical Vapor Deposition Synthesis Carbon Nanosheet–Coated Zirconium Diboride Particles for Improved Fracture Toughness

Carbon nanosheet–coated micron zirconium diboride particles were achieved by an atmospheric chemical vapor deposition in the presence of methane gas without catalyst. The microstructures and carbon structure for the novel particles were characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. In addition, the growth process of hybrid particles was analyzed by thermodynamic theory. The results showed that zirconium diboride particles were coated by carbon nanosheets uniformly. The carbon nanosheets/zirconium diboride particles were employed to fabricate ceramic composite using spark plasma sintering process. The fracture toughness of the composite was improved up to 5.9 MPa·m^0.5 with only 0.9 wt% of carbon nanosheets, which was 40.9% higher than that of the composite without carbon nanosheets. The toughening mechanisms were mainly known as carbon nanosheets crack bridging and pulling out which lead to the formation of crack deflection in the novel composite.     

Effect of heat treatment at 1300°C on W coating prepared by double-glow plasma on carbon/carbon composite

W-coated carbon/carbon composite has been considered as an attractive ITER plasma facing material in fusion devices. In this paper, W coating was prepared on the carbon/carbon composite substrate by double-glow plasma method using pure W as target. Argon was input into the chamber as the plasma and the reactive gas. W-coated carbon/carbon composite was heat-treated in vacuum furnace at 1300°C for 1 h. Phase and microstructure of W coating were examined by X-ray diffraction and scanning electron microscopy, respectively. The chemical composition of W coating was analyzed by energy dispersive spectroscopy. The micro-hardness of the W coating was estimated by nano-indentation instrument. The results indicated that a continuous and dense W-modified layer could be successfully coated on the carbon/carbon composite surface by double-glow plasma method. W coating completely reacted with C to form WC at 1300°C. WC almost completely diffused into the carbon/carbon composite after heat treatment. The great decrease in elemental W on the carbon/carbon composite surface after heat treatment led to a significant reduction in micro-hardness.     

Production of an iron-loaded carbonaceous material through pyrolyzing biomass impregnated with FeCl2

We propose a novel method for preparing iron-dispersed carbonaceous materials by utilizing low-grade materials and waste heat. Iron is loaded into the biomass through stirring it in a solution of FeCl₂ for 2 h and then pyrolyzed at 600–900 °C to prepare materials composed of iron and carbon. Further in order to investigate the reactivity of the sample, steam and CO₂ gasifications of the material was performed at 800–900 °C. Approximately 80% of the carbon in the biomass remained in the solid state during pyrolysis at 600 °C because of the effect of FeCl₂ in promoting the carbonization of the biomass. The prepared material displayed high reactivity during gasification due to the catalytic effect of loaded iron. This result indicated the possibility that the composite may be used as an iron and heat source for a steel converter. Furthermore, the high reactivity of the composite during steam gasification suggests its usefulness as a medium for hydrogen or carbon monoxide production.