Decrease in Fullerene Productivity Due to Air Leakage in Carbon Arc Method

Abstract

Fullerene productivity was investigated in the carbon arc discharge method when air was deliberately introduced into He-filled arc apparatus. Values of fullerene yield and production rate did not vary until the air leakage rate, denned as an increase in the ratio of air partial pressure relative to He pressure, was 0.2%/min. Fullerene productivity drastically decreased when the air leakage rate increased above 0.2%/min. Emission spectroscopic measurement of the arc plasma suggested the possibility that this decrease in productivity was related to an increase in the formation of carbon-air combined molecular species, e.g., CN, in the plasma.     

Control of Fullerene Generation Through the Macroscopic Parameters of Carbon Plasma Arc

The erosion of graphite electrodes in the dc electric arc has been studied in fullerene synthesis process for various arc current between 50 and 120 A. The rapid expansion of carbon vapour appears to be the main factor hampering the high efficiency formation of the fullerenes.     

Control of Fullerene Generation Through the Macroscopic Parameters of Carbon Plasma Arc

Abstract

The erosion of graphite electrodes in the dc electric arc has been studied in fullerene synthesis process for various arc current between 50 and 120 A. The rapid expansion of carbon vapour appears to be the main factor hampering the high efficiency formation of the fullerenes.     

Kinetics of Fullerene Formation in a Contact Arc Generator

Abstract

A kinetic model of the fullerene growth process in a contact arc generator is developed. On the basis of the kinetic model, the yield of the magic fullerenes C₆₀ and C₇₀ is calculated. The fullerene yield is determined by the temperature gradient in the fullerene formation zone, the carbon vapor concentration and the helium jet velocity in the interelectrode space. We found that the upper boundary value of the magic fullerene yield was about 20%.     

Kinetics of Fullerene Formation in a Contact Arc Generator

A kinetic model of the fullerene growth process in a contact arc generator is developed. On the basis of the kinetic model, the yield of the magic fullerenes C₆₀ and C₇₀ is calculated. The fullerene yield is determined by the temperature gradient in the fullerene formation zone, the carbon vapor concentration and the helium jet velocity in the interelectrode space. We found that the upper boundary value of the magic fullerene yield was about 20%.     

Anisotropies in Carbon Nanotube Synthesis by the Hydrogen Arc Plasma Jet Method

Single-wall carbon nanotubes were prepared under hydrogen gas atmosphere with a DC arc discharge maintained between the tip of a sharpened graphite cathode and an anode formed by a catalytic mixture of graphite, FeS, Ni, Fe and Co compressed powders. The cathode is placed with an inclination with respect to the anode, so that the plasma jet of the discharge is deviated towards the empty space of the growth chamber. Samples were classified and analyzed according to their type and growth positions relative to the direction of the plasma jet flow. Characterization of the samples was performed with mass spectrometry, Raman spectroscopy and transmission electron microscopy. A subtle variation is found in the properties of the nanotubes obtained in different locations due to the directionality of the plasma jet flow. Observed differences in sample properties may be qualitatively understood in terms of accepted mechanisms of SWNT growth.     

Macroparticle Acceleration in a Carbon Arc

Consideration is given to the mechanisms of acceleration of carbon macroparticles forming a cathode coating in a carbon arc under the conditions of fullerene formation. Based on experimental data and theoretical estimates, the macroparticle velocity is determined. It is shown that on collision of particles with the cathode surface the conditions are realized in the zone of contact where graphite fusion can occur.     

Radiation-Induced Trichloromethylation of C60 Fullerene in Carbon Tetrachloride

The radiolysis of C₆₀ in CCl₄ has been studied in detail from the organic chemistry point of view. Solutions of C₆₀ in CCl₄ have been treated with γ radiation at 25, 50, 150, and 600 kGy, and the resulting products have been studied by electronic absorption spectroscopy, FT-IR spectroscopy, solid state ¹³C-MAS-NMR and by thermogravimetric analysis. The products have also been separated by liquid chromatographic analysis (HPLC). C₆₀ undergoes a multiple trichloromethylation reaction and on average about 6 trichloromethyl radicals add to the fullerene cage. The trichloromethylation reaction is accompanied by the dimerization and trimerization of C₆₀ fullerene. Also the oligomers appear to be trichloromethyl-substituted.

For reference the C₆₀ solutions in CCl₄ have also been photolyzed with UV light. Similar product as those observed in the radiolysis experiment have been detected. The main difference is that the photolysis products appear both chlorinated and trichloromethylated while the radiolysis product appear almost exclusively trichloromethylated.     

Diffusion of Carbon in Steel Grippers Due to Cyclic Contact Stress

The stress-assisted diffusion of carbon atoms due to high-stress cyclic loading of serrations on a case-hardened steel gripper, leading to the redistribution of carbon near the surface of the serrations is explored in this paper. An elastic plastic finite element model coupled with simulation of stress-assisted diffusion of carbon is employed for the study. Kinematic hardening rule is used to estimate the dissipated plastic strain energy due to the contact stress and these results are transferred to the nodes of a very fine square grid. Potential gradient due to dissipated plastic strain energy coupled with modified Fick’s law are employed to simulate the stress-assisted diffusion of carbon near the surface of a serration on the gripper jaw. Measures for quantifying the redistribution of carbon are introduced, and the effect of the number of cycles and loading condition on the redistribution of carbon in steel are explored.     

Radical-scavenging Ability of Hydrophilic Carbon Nanoparticles: From Fullerene to Its Soot

We have recently developed a facile synthetic method for highly water-soluble fullerene, so-called fullerenol, for the treatment of fullerene with hydrogen peroxide. This method was applied to fullerene soot to yield the corresponding new hydrophilic carbon materials, and the obtained products were subjected to infrared spectroscopy and elemental analysis. The DLS particle size analysis demonstrated the relatively high dispersion of hydrophilic fullerene soot with a diameter of ?70 nm in water, while the hydrophilic activated carbon obtained by the same treatment showed the larger aggregation with diameters of 200 and 970 nm. The surface analysis using FE-SEM showed the difference in morphology between fullerene soot and activated carbon as well as between before and after hydrophilic treatment of the soot with hydrogen peroxide. Moreover, this hydrophilic fullerene soot exhibited high antioxidant activity (%AOA) up to 87% compared with fullerenol C₆₀(OH)₃₆ (54%) and C₆₀ (50%) evaluated by β-carotene bleaching method.     

提速对列车空调系统的影响

分析了列车提速对空调系统的不利影响，讨论了新风量计算应考虑的因素，并提出了改善空调系统性能的措施。     

富勒烯和碳纳米管在润滑体系中的研究进展

纳米材料改善润滑体系是摩擦学研究的热点之一.综述了富勒烯和碳纳米管改善流体润滑体系、固体润滑体系(固体膜、碳基、聚合物基、金属基、陶瓷基润滑体系)摩擦性能的研究进展.富勒烯和碳纳米管可使体系的摩擦系数减小、磨损率减小、硬度增大,从而优化摩擦性能.富勒烯和碳纳米管具有优良的自润滑性,有成为"分子滚珠(轴)"润滑添加剂的潜力.     

Study of the Submerged Electric Arc in Hexane in Presence of C60 Fullerene

The effect of the electric arc between graphite electrodes submerged in n-hexane solutions of C₆₀ fullerene has been studied by electronic absorption spectroscopy, liquid chromatographic analysis (HPLC-DAD), and FT-IR spectroscopy. The experimental results show that C₆₀ does not appear able to inhibit the polyynes' formation at the concentration used. Polyynes are formed in large amounts as usual from the graphite arc, and polycyclic aromatic hydrocarbons have been detected as by-products. Prolonged arcing causes the disappearance of C₆₀ from the solution. There is experimental evidence that C₆₀ undergoes radical addition reactions during the early stages of arcing.     

Synthesis of Heterogenous Multi-Walled Carbon Nanotubes in a Carbon Arc in Water

Boron-doped multi-walled carbon nanotubes (MWCNTs) were generated by arc discharge in water by using B-doped graphite electrodes. The product morphology was studied by SEM and HRTEM microscopy. The electronic features were determinated by Raman and EELS spectroscopy. Optical emission spectroscopy (OES) was used to evaluate the temperature and C₂ content distributions in arc plasma.     

Fringing Field Formulas and Winding Loss Due to an Air Gap

The paper describes a simple treatment for the fringing fields of an air gap in the core of a magnetic component such as an inductor or a transformer. It verifies the derived analytical formulas for the fields by using numerical (finite-element) calculations. It then applies these formulas to the calculation of high-frequency eddy-current losses for two types of winding arrangements, both of which employ thin rectangular conductors. The rectangular conductors are commonly used in flex circuit windings, printed circuit windings, and thin-film windings. The two types of winding configurations are flat and barrel wound. Each behaves in a different way as a function of the position of the conductor.     

空气中一氧化碳、空气中二氧化碳气体标准样品的研制

叙述了气体报警仪标定和检测使用的空气中一氧化碳、空气中二氧化碳气体标准样品的制备,以气相色谱法对其均匀性和稳定性进行考核,确保其数据准确可靠。     

粗丝CO_2气体保护焊熔滴过渡与潜弧机理的研究

本文详细分析了粗丝CO_2气体保护潜弧焊熔滴过渡的特点和潜弧机理。潜弧状态可以分为三种类型:半潜弧(熔滴主要以较大的颗粒形式过渡)、临界潜弧(熔滴主要以较小颗粒的射滴形式过渡)和深潜弧(熔滴以细小射滴与射流混和形式过渡)。大电流、低电压、粗焊丝、反极性和氧化性气氛是形成潜弧过程的必要条件,其中电流是最重要的条件。潜弧后弧柱气氛改变,焊丝端部的弧根由集中形态扩展为覆盖整个端部形态,使得熔滴尺寸变得细小,熔滴过渡形式发生变化。采用临界潜弧区域的焊接规范参数施焊,飞溅小,工艺过程稳定,焊缝成形优良。     

红外图像融合在气体泄漏定位中的应用

研究了一种基于红外图像融合技术进行气体泄漏点定位的方法.通过对气体泄漏热传导过程的有限元模拟和泄漏节流温差的焦耳.汤姆逊系数计算,建立了被测对象的温度场模型.实验采用主动式冷却器对气体进行降温处理以增强现象,利用热像仪分别采集金属与非金属对象充入压缩空气前后的红外图像, 根据不同材质对象的导热特性分别建立泄漏诊断阈值并进行熵值融合计算,从而定位泄漏点.仿真和实验结果表明,红外热像图可以灵敏地反映泄漏点处温度变化,熵融合算法能够快速、准确地提取出多种材质对象的泄漏位置,并且有效克服了被测工件表面缺陷对温度场及定位的干扰.     

泵用低周向泄漏圆弧转子的新型线研究

为实现罗茨泵圆弧转子的低周向泄漏、无闭气现象、造型参数化和尺寸最优化。从7个方面构建出第1、2两类新型线的参数化方程;后以节圆半径和周向弧半角为设计变量, 转子副所占方体空间的轻量化为目标函数, 构建优化模型;最终就闭气现象, 给出谷部型线段上的新避让型线。结果表明:新型线的主圆弧圆心为不位于峰轴上的偏心圆弧;新型线的低周向泄漏是以降低最大形状系数和增加泵体积为代价的, 叶数越多、周向弧半角越大, 牺牲越大, 应优选2叶第1类新转子;谷部的新避让圆弧能有效消除闭气现象, 且简化加工等。为泵其它型线的低周向泄漏, 提供一种全参数设计与造型方法。