氟化石墨工艺技术研究

气相法制备氟化石墨由于工艺简单、产品纯度高而成为合成氟化石墨最常用的方法。氟化石墨的合成过程涉及高温与活性单质氟气两方面的因素,安全控制十分重要。从原料、反应时间、反应温度、反应设备和纯化方法等方面对合成氟化石墨的工艺技术进行对比,旨在避免生产过程中出现潜在的危险,寻求提高氟化石墨产品质量的新方法,提升氟化石墨整体制备工艺的安全性。     

Electrical characteristics of fluorinated carbon black‐filled poly(vinylidene fluoride) composites

Dispersion and electrical properties of fluorinated carbon black‐filled poly(vinylidene fluoride) (PVDF) composites were studied as a function of the fluorine content. It was found that with increasing the fluorine content carbon particles tend to stick together to form large aggregates. The percolation concentration increases to a high concentration, whereas the percolation process becomes gradual. The temperature dependence of resistivity measurements show that the fluorinated carbon black‐filled PVDF composites exhibit a high PTC intensity and a low NTC effect. These phenomena were discussed in terms of thermodynamic interactions between fluorinated carbon and the PVDF matrix. The dielectric behavior was also investigated in this study. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1063–1070, 2001     

Discharge characteristics of graphite fluorides prepared via graphite intercalation compounds in nonaqueous lithium cells

Two types of graphite fluorides (C₂F)_n and (CF)_n were prepared by refluorination of thermally decomposed ionic graphite intercalation compounds of fluorine. Discharge behavior and effect of the heat treatment of graphite fluoride were investigated. This method drastically decreased the reaction time compared with the direct fluorination of graphite. OCV of (C₂F)_n was higher by 0.3 V than that of the conventionally prepared one, however, overpotential was the same at the constant current density of 0.5 mA cm⁻². On the other hand, the same OCV and less overpotential by 0.3 V were observed for (CF)_n. The heat treatment of these samples in fluorine atmosphere at higher temperatures increased the discharge capacity and provided a more flat discharge potential.     

Laser raman studies on carbons

Laser Raman spectra were studied of natural graphite (SP-1) and carbonaceous materials including pyrolytic graphite, carbon black, glassy carbon, coal, “white” carbon and sputtered carbon. All of these carbons have two Raman bands at 1580 cm^?1 and 1360 cm^?1, except for natural graphite which has a single sharp Raman band at 1580 cm^?1. The relative intensity of the 1360 cm^?1 band to the 1580 cm^?1 band and the half band width increase going from graphite through glassy carbon to carbon black. The 1360 cm^?1 band in glassy carbon becomes sharper and stronger with the increase of heat-treatment temperature (HTT), while the addition of iron to the glassy carbon matrices results in a decrease in intensity and half band width of this band with increasing HTT and iron content. Sputtered carbon and “white” carbon, prepared from graphite irradiated by a high power laser, showed an additional broad band around 2140cm^?1. This band is believed to originate from conjugated acetylenic bands (—CC—)_n.     

天然鳞片石墨/环氧树脂复合材料的制备及导热性能研究

以天然鳞片石墨为导热填料,E44型环氧树脂为基体,采用超声分散法制备天然鳞片石墨/环氧树脂复合导热材料.系统考察了天然鳞片石墨用量、石墨粒度和炭黑添加量等因素对复合材料导热性能的影响.结果表明:随着天然鳞片石墨用量增加,复合材料的导热系数增大,抗压强度先增加后减小;复合材料的导热系数随天然石墨粒径的增大而增大,抗压强度先减小后增加;在石墨/环氧树脂复合导热材料中添加不同用量的炭黑时,随着炭黑添加量的增加,复合材料的抗压强度增大,导热系数先增大后减小.制备天然鳞片石墨/环氧树脂复合导热材料的最佳配方为天然鳞片石墨用量45％,粒径≤270 μm,炭黑用量2％.     

Thermal fluorination effects on carbon nanotubes for preparation of a high-performance gas sensor

A high-performance NO gas sensor was prepared by inducing thermal fluorination of carbon nanotube semiconductors. Thermal fluorination of multi-walled carbon nanotubes (MWCNTs) was carried out at various temperatures (100 ∼ 1000 °C) to investigate the effects of the reaction temperature. The mechanism of high-performance NO gas sensor electrode was shown to depend on the fluorination temperature in a way that can be divided into three regions, separated at 400 and 1000 °C. In the first temperature region, the induction of fluorine functional groups onto MWCNTs showed the opposite trend in electrical resistance change comparing with traditional p-type MWCNTs. In the second temperature region, the induced fluorine functional groups were attenuated by generated fluorinated carbon gases resulting in the decomposition of MWCNTs and the recovery of traditional p-type gas sensor behavior. In the highest temperature region above 1000 °C, reoriented carbon structure was observed, showing bent nanotubes produced from destruction by fluorination and subsequent reorientation due to the high temperature. The gas sensing responsiveness was significantly improved by the thermal fluorination, which causes electrophilic attraction, creates adsorption sites for target NO gases and improve hydrophobicity for gas sensing stability in humid condition. In conclusion, a high-performance gas sensor was obtained by thermal-fluorination of MWCNTs.     

Electrochemical performance of low temperature fluorinated graphites used as cathode in primary lithium batteries

The present study highlights the electrochemical performance of two series of fluorinated graphites used as the cathode in primary lithium batteries. These compounds were prepared under fluorine gas at room temperature using a catalytic atmosphere made of boron or chlorine fluoride, and then thermally treated between 100 and 600 °C. The electrochemical properties are correlated to a complete physico-chemical characterization, already performed by XRD, NMR, FT-IR and EPR. In particular, important parameters are taken into account: C-F bonding, carbon hybridization, fluorine content (i.e. F/C ratio) and amount of intercalated catalyst residues. It is shown that the average discharge potential of fluorinated graphite used in primary lithium batteries can be predicted owing to the chemical shift values (δ_C-F) obtained by solid ¹³C NMR. On the other hand, the higher capacity values are achieved for low temperature fluorinated graphite treated at the highest temperatures, i.e. for high fluorination level. The electrochemical performance study of these materials is completed by the study of the effect of simulated storage. The differences between the various samples during electrochemical tests and those observed using different electrolytes are discussed. Fluorinated graphites obtained with a chlorine catalyst or post-treated at temperatures higher than 450 °C are unaffected by ageing.     

自蔓延高温技术制备ZrC粉体(英文)

采用自蔓延高温合成(self-propagating high-temperature synthesis,SHS)技术,以 Zr+C 为反应体系合成了 ZrC 粉末。研究了实验参数对 SHS过程中点火电流、燃烧温度的影响。采用了 3 种碳源,研究了其对最终产物形貌及化学组成的影响。通过添加不同含量的 NaCl 作为 SHS 稀释剂,控制产物粒径及形貌。结果表明:炭黑是高温自蔓延法制备 ZrC 粉体的最佳碳源。由该体系制备的 ZrC 粉末粒径在 0.5～1 μm之间,氧含量为 0.38%。随稀释剂 NaCl 含量增加,体系燃烧温度降低,产物粒径减小。当 NaCl 含量为 30% (质量分数)时,体系燃烧温度下降至 1 810 K,产物 ZrC 粉末的粒径减小至 50 nm。     

磷肥副产氟硅酸氨化制高补强白炭黑技术研究

利用磷肥副产氟硅酸为原料,采用氨水作为氨解剂制备高补强白炭黑。论述了白炭黑的制备原理,研究了氟硅酸浓度、氨水滴加速率、反应温度、陈化时间对白炭黑比表面积的影响。该方法所得白炭黑比表面积大,产品质量符合行业标准要求,经济效益和环境效益明显。     

Development of Fe-doped carbon electrode for mass-producing high-yield single-wall carbon nanotubes

High crystallinity single-wall carbon nanotubes (SWNTs) can be synthesized by arc discharge evaporation of Fe-doped carbon electrode in hydrogen mixed gas, but the purity of as-grown SWNTs is strongly affected by the kinds of Fe-doped carbon electrode. Various carbon materials (artificial graphite powder, carbon black, calcined coke, etc.) have been tried to prepare Fe-doped carbon electrodes. The calcined coke, a kind of graphitizing carbon, is suitable for preparing high-quality Fe-doped carbon electrode. Moreover, the heat-treatment of Fe-doped carbon electrode in vacuum at the temperature of 1600 °C also plays an important role. At present, the best carbon electrode containing 1 at.% Fe catalyst is capable of continuously generating SWNTs at a production rate of 8 mg/min, which can be easily purified to obtain high purity SWNTs.     

含氟废气的危害及其回收利用

针对磷化工生产排放的大量含氟废气对环境的污染问题,提出了以含氟废气为原料制取纳米白炭黑的实验研究方法;论述了氨化反应的基本原理、工艺流程特点以及白炭黑质量的影响因素;实验结果表明：用氟化铵溶液和氨吸收含氟废气得到氟硅酸铵溶液,进一步氨解得到高浓度的氟化铵溶液,由高浓度氟化铵可以制取系列高附加值的无机氟化物;该法克服了传...     

Graphite intercalation compound of magnesium fluoride and fluorine

A graphite intercalation compound of C_xF(MgF₂)_y was prepared under a fluorine atmosphere of 1 atm at temperatures of 20–350°C. The 1st stage compound has the identity period of 9.3–9.4Å. ESCA and ¹⁹F NMR spectra indicate that the chemical interaction of intercalated fluorine with carbon is similar to that for graphite fluoride, however, with C_xF(MgF₂)_y having slightly mobile fluorine atoms chemically adsorbed on carbon atoms of graphite layers.     

Novel vapor sensor from polymer-grafted carbon black: effects of heat-treatment and γ-ray radiation-treatment on the response of sensor material in cyclohexane vapor

Polyethylene (PE) was grafted onto carbon black surface by γ-ray radiation of the PE-adsorbed carbon black. Vapor sensor composite materials were prepared from the PE-grafted carbon black and PE as a matrix polymer. The effects of heat-treatment and γ-ray radiation-treatment on the response of the electric resistance of the sensor material against cyclohexane vapor were investigated. The heat-treatment of the composite improved the crystallinity of the matrix PE, and thus increased the responsiveness against cyclohexane vapor about five times that of the untreated one. The γ-ray radiation-treatment slightly decreased the responsiveness against cyclohexane vapor, because the γ-ray radiation-treatment induced the crosslinking of PE. On the contrary, the stability and reproducibility of the vapor sensor material remarkably improved. By the heat-treatment followed by the γ-ray radiation-treatment, a novel stable and reproducible sensor material was obtained, which allowed to identify and to quantify certain vapors in air accurately.     

NMR and EPR studies of room temperature highly fluorinated graphite heat-treated under fluorine atmosphere

Semi-ionic carbon fluoride obtained by reaction of graphite with a gaseous mixture of IF₅, HF and F₂ was modified by a post-fluorination at various temperatures in the range 100-680 °C. The resulting materials were studied by ¹⁹F-NMR and EPR both at room temperature and at different experimental temperatures from 200 to 360 K and from 100 to 473 K for NMR and EPR experiments, respectively. ¹⁹F-NMR gives information about the residual intercalated iodine fluoride species (IF₅, IF₆⁻ and IF₇) such as the temperature of their removal from the host fluorocarbon matrix and their mobility into the interlayer space. The nature of the C-F bonding was investigated by ¹⁹F-NMR, MAS/¹³C-NMR, FT-IR spectroscopy and X-ray diffraction. The C-F bonding changes from semi-ionic to a mainly covalent character at a fluorination post-treatment temperature close to 450 °C. This transformation coincides with the removal of the iodine fluoride species from the host structure. The densities of the paramagnetic dangling bonds were studied by EPR; this technique allows also to investigate the local environment of the dangling bonds in the fully fluorinated samples (obtained with fluorination post-treatment temperatures higher than 450 °C). As a matter of fact, an hyperfine structure was observed for these samples; it results from interaction of the dangling bond electron with six neighboring fluorine nuclei. The role of the intercalated species (iodine fluoride compounds and HF) on the mechanisms of the extra-fluorination is also discussed.     

Characterisation of carbon blacks produced by solar thermal dissociation of methane

Solar methane dissociation appears as a possible route toward a hydrogen-based economy. The competitiveness of the process strongly depends on the carbon black properties and economic value. At CNRS-PROMES, a 50 kW tubular solar reactor was developed to produce carbon black and hydrogen from methane. The reaction was carried out in a graphite receiver crossed by seven graphite tubes heated up by concentrated solar radiations at the 1 MW CNRS solar furnace. The temperatures ranged between 1608 K and 1928 K and the methane flow-rates varied from 10.5 to 21 NL/min. Total methane dissociation was reached with hydrogen yield higher than 80% and the carbon yield was drastically affected by the acetylene by-product. The carbon samples were analysed in detail and their properties were compared to a commercial conductive grade carbon black. Transmission electron microscopy showed primary particles of 10–70 nm diameter. The crystallinity of the samples was characterised by Raman spectroscopy. It was also possible to correlate the specific surface area with the reaction temperature and with the concentrations of residual methane and of the acetylene by-product. The resistivity and the structure of the agglomerates were determined by simultaneous measurements of the conductivity and the density under compression.     

电解制氟与石墨阳极表面氟化石墨钝化层的研究

合成氟化石墨的关键原料是单质氟气。利用自制的电解装置,通过电解熔盐KF·2HF成功地制取了氟气。采用特制的“阳极罩”使电解制得的F2与H2隔离,提高了安全性。用石墨材料作阳极,表面易生成不利于电解电流通过的“钝化层”,经红外光谱测试分析,其组成为富含F-C健的氟化石墨,而用无定型炭材料作电解阳极,不易生成该钝化层,且使用寿命较长。     

Preparation and characterization of superhydrophobic conductive fluorinated carbon blacks

Superhydrophobic conductive carbon blacks were prepared by covalent bonding of perfluorocarbon and perfluoropolyether chains on the conductive carbon black surface. Perfluorodiacyl and perfluoropolyether peroxides were used as reagents for the chemical treatment. Their thermal decomposition produced respectively, perfluoroalkyl and perfluoropolyether radicals that directly bonded the polycyclic aromatic structure of carbon black surface. Measurements of contact angles with water on molded pellets made with carbon black powder demonstrated that water droplets were enduringly stable on the treated carbon blacks. Contact angle values were significantly high, exceeding the superhydrophobicity threshold. On the contrary, the droplets were adsorbed in few seconds by the native carbon black. Conductivity measurements showed that the covalent linkage of fluorinated chains weakly modified the electrical properties of the conductive carbon black, even if the surface properties changed so deeply. The relationship between the linkage of fluorinated chains and the variations of physical–chemical properties were studied combining electron spectroscopy, resistivity measurements, X-ray diffraction, scanning electron microscopy, surface area analysis and thermal gravimetric analysis. The superhydrophobic conductive carbon blacks were compared with a superhydrophobic carbon black obtained by direct fluorination of conductive carbon black with elemental fluorine, F₂.     

Preparation,structure and electrical conductivity of graphite intercalation compound with titanium fluoride

The graphite intercalation compound (GIC) of titanium fluoride has been prepared in a fluorine atmosphere. The GICs prepared from natural graphite and pitch-based carbon fiber were mostly stage-2 compounds with repeat distance 11.28–11.59 Å and composition C_11–15TiF_4.5–6.2. The ESCA spectrum indicates that intercalated TiF₆²⁻ anions are mainly in a bridged state. The slight decrease in the repeat distance with increasing fluorine pressure is ascribed to the nestling of TiF₆²⁻ anions in benzene rings of carbon layers due to the increase in nonbridging TiF₆²⁻ anion. X-ray powder diffraction data indicate the high regularity in the orientation of intercalated species between carbon layers. The highest electrical conductivity was 2.4 × 10⁵ Scm⁻¹, which is 13 times higher than that of pristine HOPG.     

Direct fluorination of poly(p-phenylene)

Because of its good chemical and thermal stability due to the π-delocalization along the polymer chain, poly(p-phenylene) was used as starting material for fluorination to obtain new carbon fluoride. A complete characterization of both the virgin polymer, in order to define parameters such as the chain length and the degree of crystallinity, and the fluorinated materials was performed by complementary techniques (¹⁹F, ¹H and ¹³C NMR, XRD, FT-IR and EPR). From these data, possible fluorination mechanisms are discussed. Finally, tribological properties have been also studied for the fluorinated samples and compared to those of conventional graphite fluorides.     

氟气氟化含氢氟聚醚制备双端官能团全氟聚醚

以含氢氟聚醚（E10H）为原料，利用氟氮混合气进行氟化制备了双端羟基全氟聚醚（F-E10H-AL），分别探索了常温氟化、低温氟化及先低温后常温氟化的3种氟化工艺。然后与双三氟甲烷磺酸亚胺锂（LiTFSI）制备成锂离子电解质。采用红外光谱、核磁氢谱和氟谱分析氟化后的产物结构，并采用电化学工作站测试了阻抗和计时电流。结果表明，低温氟化工艺具有较高的氟化效率，在-10℃对E10H直接氟化12h后，分子链上有21.0%的H被F取代，但是产生较多的封端基团CF3O-。当利用六氟环氧丙烷二聚体酯化保护E10H上的羟基时，采用先低温后常温氟化工艺，分子链上有48.3%的H被F取代。最后将氟化产物还原，得到F-E10H-AL，分子链末端基本没有CF3O-，含量为0.7%。结合阻抗和计时电流的数据，计算出F-E10H-AL/LiTFSI的离子迁移数为0.32，高于PFPE-OH/LiTFSI（0.07）。