Reaction thermodynamics of carbon nanospheres prepared by CaC2-CHCl3 system

利用CaC2-CHCl3体系反应合成纳米碳球,利用X射线衍射仪(XRD)和扫描电镜(SEM)对产物的物相、形貌和显微结构进行分析。对该体系进行吉布斯自由能和反应热效应计算,结合实验结果,研究采用无机化学反应法制备微纳米碳球的中间态成碳机理。结果表明:从理论上证实CaC2-CHCl3体系热解产物可能为石墨、金刚石和C3原子气;标准状态(298 K)下CaC2-CHCl3体系的吉布斯自由能、反应热效应和绝热温度分别为?1 847.5 kJ/mol、?1 945.5 kJ/mol和6 184 K;C3原子气是低温反应条件下无机碳源制备纳米碳球的中间态碳源前驱体。用CaC2-CHCl3体系可制备最大直径200~300 nm左右的碳球。Carbon nanospheres were prepared via CaC2-CHCl3 system,and the phase,morphology and microstructure of the pyrolytic products were detected by X-ray diffraction（XRD） and scanning electron microscope（SEM）.Gibbs free energies and reaction thermodynamics of the system were theoretically calculated.Combining with experimental analysis,the mechanism for intermediate state carbon formation of carbon nanospheres by inorganic chemical reaction technology was studied.The results show that the pyrolytic products of CaC2-CHCl3 system are probably graphite,diamond and C3 atom gas.The Gibbs free energies,the reactive thermal effect and the adiabatic temperature of CaC2-CHCl3 system are-1 847.5 kJ/mol,-1 945.5 kJ/mol and 6 184 K,respectively.C3 atom gas is the intermediate carbon precursor of carbon nanospheres under the low temperature reaction and inorganic carbon source.Carbon nanospheres with maximum diameter of 200-300nm can be synthesized via CaC2-CHCl3 system.广西大学有色金属及材料加工新技术教育部重点实验室开放基金资助项目(GXKFJ-18);国家重点基础研究发展计划(973计划)资助项目(2006CB600901);广西科学基金资助项目(桂青科0991015);广西教育厅项目(200808MS083

Carbon spheres prepared via solvent-thermal reaction method and their microstructures after high temperature treatment

Carbon spheres with size of 50-300 nm were synthesized via a solvent-thermal reaction with calcium carbide and chloroform as reactants in a sealed autoclave.The morphologies and microstructures of carbon spheres before and after high temperature treatment(HTT) were characterized by X-ray diffractometry(XRD) ,scanning electronic microscopy(SEM) ,energy diffraction spectroscopy(EDS) ,and transmission electron microscopy(TEM) .The formation mechanism of carbon spheres was discussed.The results indicate that the carbon spheres convert to hollow polyhedron through HTT.Carbon spheres are composed of entangled and curve graphitic layers with short range order similar to cotton structure,and carbon polyhedron with dimension of 50-250 nm and shell thickness of 15-30 nm.The change of solid spheres to hollow polyhedron with branches gives a new evidence for formation mechanism of hollow carbon spheres.Project(2006CB600901) supported by the National Basic Research Program of China;Project(0991015) supported by Guangxi Natural Science Foundation,China;Project(200808MS083) supported by Guangxi Education Department Foundation,Chin

CO2 对 La0.6Sr0.4CoO3-δ阴极影响

La0.6Sr0.4CoO3-δ (LSC) perovskite represents one kind of cathode materials for intermediate- and low-temperature cells having high electronic conductivity and high ionic conductivity as well as high catalytic activity for oxygen reduction. The stability of LSC cathode against CO2 in air is an important aspect for practical application. In this work, we investigated the adsorption of CO2 on LSC, reaction of CO2 with LSC and thereof the effect of CO2 on cathode performance.La0.6Sr0.4CoO3-δ (LSC) perovskite represents one kind of cathode materials for intermediate- and low-temperature cells having high electronic conductivity and high ionic conductivity as well as high catalytic activity for oxygen reduction. The stability of LSC cathode against CO2 in air is an important aspect for practical application. In this work, we investigated the adsorption of CO2 on LSC, reaction of CO2 with LSC and thereof the effect of CO2 on cathode performance

PREPARATION AND ELECTROCHEMICAL PROPERTIES OF CARBON NANOSPHERES FROM CaC2 - CCl4 SYSTEM

以碳化钙和四氯化碳为碳源,反应物通过无机化学反应在密封高压釜中制备了纳米碳球。用XRD、SEM、EDS、TEM、HRTEM和BET法对碳球的形貌和结构进行表征,并采用恒流放电法研究其作为锂离子电池负极材料的电化学性能。研究结果表明:合成的纳米碳球具有棉花状结构,直径分布为80～250nm,其d002为0.336～0.340nm,属于无定形碳结构,BET比表面积为98m2/g。纳米碳球作为负极材料首次充放电比容量分别为787mA·h/g和390mA·h/g,充放电效率为49.6%;5次循环后放电比容量衰减到239mA·h/g,但效率均保持在95%以上。Carbon nanospheres were synthesized by an inorganic chemical reaction with calcium carbide and chloroform as carbon sources in a sealed autoclave. The morphology and microstructure of the carbon spheres were characterized by XRD, SEM,EDS, TEM, HRTEM, and BET specific surface area, and the electrochemical properties of the carbon spheres as anode material for lithium- ion batteries were investigated by use of chronopotentiometry （CP） . The results indicate that the carbon spheres are composed of the cottonstructure spheres with the diameter between 80 nm and 250 nm. The d002 of the carbon spheres are in the range of 0. 336 ～0. 340 nm and the BET area surface is 98 m2/g. The first charge/discharge specific capacities of the carbon spheres as negative electrodes are 787 mA·h/g and 390 mA· h/g, respectively, and the first efficiency is 49. 5%. After 5 times cycles,the discharge specific capacity decreases to 239 mA· h/g,but the efficiency keeps above 95%.国家重点基础研究发展计划(973计划)资助项目(2006CB600901