等离子体条件下煤基富勒烯的制备及生成机理

以淄博贫煤为原料,用射频等离子体法合成碳纳米管（carbon nanotubes,CNTs）和纳米洋葱状富勒烯（nano—structured onion—like fullerenes,NSOFs）,运用场发射扫描电子显微镜（FE—SEM）和高分辨透射电子显微镜（HRTEM）对产物进行了表征和分析．结果表明：以淄博贫煤为原料制备出CNTs和NSOFs,CNTs直径分布均匀,约为10nm左右,准球状的NSOFs直径分布在8nm-30nm之间,石墨化程度较高;并对不同变质程度的煤制备富勒烯的生成机理进行了比较与讨论．     

以煤炭直接液化残渣为原料制备炭纳米管

以煤炭直接液化残渣为原料,采用直流电弧放电法成功制备出炭纳米管.采用扫描电子显微镜、透射电子显微镜、高分辨透射电镜以及X射线衍射等手段对炭纳米管的形貌和结构进行了表征.结果表明,所得直而长的多壁炭纳米管具有很好的石墨化程度;其长度达几微米,内径约80 nm,外径约120 nm;残留在液化残渣中的黄铁矿及液化过程中产生的磁黄铁矿对炭纳米管的形成有催化作用.     

CALENDAR OF EVENTS

To elucidate the adhesion mechanism of carbon nanotubes (CNTs) designed to mimic natural contact surfaces in the gecko, their contact behavior was investigated using a scanning electron microscope (SEM) equipped with manipulation stages. The normal adhesion of CNTs increases in direct relation with a preload, which is true also for gecko setae. The CNT shear strength increases concomitantly with increasing CNT length, indicating that the length is an important factor enabling conformation to the surface roughness and enabling generation of a strong contact by side contact. Results revealed the CNT configuration and surface physics as important factors for synthetic gecko adhesion.     

紫外光辐照ABS/碳纳米管的研究

丙烯腊—丁二烯—苯乙烯共聚物(ABS)在室温、氮气环境下，通过紫外光辐照，在其分子链上引入了碳纳米管(CNTs)。通过荧光光谱分析，ABS／CNTs在418nm处有强的荧光发射峰；透射电子显微镜观察发现，CNTs在端头处打开及转弯处打断，被ABS包覆，ABS/CNTs的体积电阻率随CNTs的加入量增多而降低；紫外光辐照ABS/CNTs的导电性显著优于熔融共混ABS/CNTs；扫描电子显微镜表明，CNTs在紫外光辐照ABS基体中均匀分布。     

Imaging of CNTs in a polymer matrix at low accelerating voltages using a SEM

As continued work of scanning electron microscope visualization of carbon nanotubes (CNTs) in epoxy matrix at high accelerating voltage (from 3 to 15 kV), this study focuses on the low accelerating voltage range (from 0.3 to 5.0 kV). In the CNT/epoxy composite, the CNT contrast is observed to invert two times as the accelerating voltage increases from 0.3 to 5.0 kV. At 0.7 kV the CNT contrast shifts from bright to dark, and after 1.5 kV bright CNTs are observed again. The contrast inversion and imaging mechanism of CNTs are interpreted in correlation with the secondary electron (SE) yield curve of epoxy. At 0.3–0.6 kV the epoxy is positively charged, which results in influx of electrons (from the ground) through the CNTs. These electrons lower the potential of the CNTs and enhance the local SE emission. The bright CNTs contrast at >1.5 kV is attributed to the high SE yield resulting from the trapping of injected primary electrons (PEs) in the CNTs. At 0.7 and 1.0 kV the dark CNT contrast may be attributed to the weak PEs–CNTs interaction or to the slight charging of epoxy. Further observation suggests that latter is more likely to occur.     

化学气相沉积法碳纳米管的制备及性能研究

开发以煤气为碳源采用化学气相沉积法制备单壁碳纳米管，并对其作为超级电容器电极的电化学性能进行研究。通过电子扫描电镜、电子透射电镜、拉曼光谱以及X射线衍射等手段对产品的形态、结构及性质进行表征分析，并对单壁碳纳米管的生长机理进行讨论；分别通过循环伏安、恒压充放电实验对单壁碳纳米管电极进行电化学性能分析。     

Experimental assessment on potential for processiblity of carbon nanotubes/epoxy system used as nanocomposites

In this study, carboxylic acid functionalized carbon nanotubes (CNTs) were used to modify epoxy with intent to develop a nanocomposite matrix for hybrid multiscale composites combining benefits of nanoscale reinforcement with well‐established fibrous composites. CNTs were dispersed in epoxy by using high energy sonication, followed by the fabrication of epoxy/CNTs composites. The processibility of CNTs/epoxy systems was explored with respect to their dispersion state and viscosity. The dependences of viscosity, mechanical and thermomechanical properties of nanocomposite system on CNTs content were investigated. The dispersion quality and reagglomeration behavior of CNTs in epoxy and the capillary infiltration of continuous fiber with the epoxy/CNTs dispersion were characterized using optical microscope and capillary experiment. As compared with neat epoxy sample, the CNTs nanocomposites exhibit flexural strength of 126.5 MPa for 1 wt% CNTs content and impact strength of 28.9 kJ m^?2 for 0.1 wt% CNTs content, respectively. A CNTs loading of 0.1 wt% significantly improved the glass transition temperatures, T_g, of the nanocomposites. Scanning electron microscopy (SEM) was used to examine the fracture surface of the failed specimens. It is demonstrated that the properties of CNTs/epoxy system are dispersion‐dominated and interface sensitive. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Direct measurement of organic sulphur in coal

A method of direct determination of the organic sulphur content of coal has been developed using the transmission electron microscope. An electron beam is focussed on a thinned section of coal and X-rays emitted from the elements in the volume irradiated by the electrons are measured by X-ray emission spectroscopic methods. Both the characteristic K_α line of sulphur and the bremsstrahlung from the material in the irradiated volume are detected by a solid-state detector. An analytical method has been developed which uses these two measurements for a direct determination of the organic sulphur concentration. Minerals can easily be avoided since they are plainly seen by conventional electron microscope techniques. Several measurements of the organic sulphur concentration in coals have been made; they agree with the conventional chemical values reported for these coals. Of most importance, though, is the use of this technique to detect spatial variations of sulphur over small distances within the coal maceral.     

Effect of surface treatment for carbon nanotubes on morphological and rheological properties of poly(ethylene oxide) nanocomposites

Poly(ethylene oxide) nanocomposites filled with functionalized multi‐walled carbon nanotubes are prepared and characterized using rheological and morphological measurements. This study investigates how the surface treatment of carbon nanotubes (CNTs) affects the CNT dispersion state. It is found that the nanocomposites have a higher effective volume fraction than the real volume fraction of the CNTs. The dispersion state of the CNTs is identified by using field emission scanning electron spectroscope and transmission electron microscope. The rheological findings indicate that there exists a percolated network structure of the CNTs in the nanocomposites, which was confirmed by electrical conductivity measurements as well as morphological observation. POLYM. ENG. SCI., 46:1350–1357, 2006. © 2006 Society of Plastics Engineers     

Thermal conductivity of poly vinylidene fluoride composites filled with expanded graphite and carbon nanotubes

The composites composed of Poly (vinylidene fluoride), expanded graphite (EG), and carbon nanotubes (CNTs) have been prepared by solution mixing, followed by compression. The structure of the composites was examined with scanning electron microscope and their electrical and thermal properties were investigated. About 1.2 wt % content of CNTs could present a percolated network in the polymer matrix, characterized by the electrical conductivity. The incorporation of EG and CNTs in the polymer caused an enhancement in thermal conductivity for the composites. However, a hybrid of EG and CNTs as filler of the polymer yielded a further improvement in thermal conductivity as compared to single component filler. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ash deposition during the co-firing of bituminous coal with pine sawdust and olive stones in a laboratory furnace

This article describes an experimental study on ash deposition during the co-firing of bituminous coal with pine sawdust and olive stones in a laboratory furnace. The main objective of this study was to relate the ash deposit rates with the type of biomass burned and its thermal percentage in the blend. The thermal percentage of biomass in the blend was varied between 10% and 50% for both sawdust and olive stones. For comparison purposes, tests have also been performed using only coal or only biomass. During the tests, deposits were collected with the aid of an air-cooled deposition probe placed far from the flame region, where the mean gas temperature was around 640 °C. A number of deposit samples were subsequently analyzed on a scanning electron microscope equipped with an energy dispersive X-ray detector. Results indicate that blending sawdust with coal decreases the deposition rate as compared with the firing of unblended coal due to both the sawdust low ash content and its low alkalis content. The co-firing of coal and sawdust yields deposits with high levels of silicon and aluminium which indicates the presence of ashes with high fusion temperature and, thus, with less capacity to adhere to the surfaces. In contrast, in the co-firing of coal with olive stones the deposition rate increases as compared with the firing of unblended coal and the deposits produced present high levels of potassium, which tend to increase their stickiness.     

Effect of Addition of Ni metal catalyst onto the Co and Fe supported catalysts for the formation of carbon nanotubes

Production of novel porous material is a major target in current material science research due to its wide applications. As carbon nanotube (CNTs) is a one dimensional hollow structure it is also one of the promising materials in applications ranging from electronics to hydrogen storage medium. Catalytic chemical vapor deposition (CCVD) is a method whereby CNTs can be produced in large amount. Thus, in this work, we have synthesized CNTs via pyrolysis of acetylene using various supported transition-metal catalysts in a fixed-bed reactor. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to investigate the CNTs structure. The structures of nanotubes formed by acetylene pyrolysis were dependent on the catalysts used. It was found that alumina supported Ni/Fe catalyst inhibited the formation of CNTs growth while alumina supported Ni/Co catalyst gave high density of CNTs. However, nanotubes grown over alumina supported Ni/Fe catalyst were less dense due to the deactivation of the catalyst at the early stage of the pyrolysis process.     

Effect of Addition of Ni metal catalyst onto the Co and Fe supported catalysts for the formation of carbon nanotubes

Production of novel porous material is a major target in current material science research due to its wide applications. As carbon nanotube (CNTs) is a one dimensional hollow structure it is also one of the promising materials in applications ranging from electronics to hydrogen storage medium. Catalytic chemical vapor deposition (CCVD) is a method whereby CNTs can be produced in large amount. Thus, in this work, we have synthesized CNTs via pyrolysis of acetylene using various supported transition-metal catalysts in a fixed-bed reactor. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to investigate the CNTs structure. The structures of nanotubes formed by acetylene pyrolysis were dependent on the catalysts used. It was found that alumina supported Ni/Fe catalyst inhibited the formation of CNTs growth while alumina supported Ni/Co catalyst gave high density of CNTs. However, nanotubes grown over alumina supported Ni/Fe catalyst were less dense due to the deactivation of the catalyst at the early stage of the pyrolysis process.     

PCL/CNTs复合材料的性能

以聚己内酯(PCL)和碳纳米管(CNTs)为主要材料,采用熔融共混制备PCL/CNTs复合材料。随着CNTs含量增加,以直径为10 nm的CNTs(简称CNTs10)制备的PCL/CNTs10复合材料的拉伸强度先增加后降低,以直径为5 nm的CNTs(简称CNTs5)制备的PCL/CNTs5复合材料的拉伸强度先减小后增大,断裂伸长率先降低后增加,体积电阻率逐步降低。CNTs含量相同时,PCL/CNTs5复合材料的体积电阻率小于PCL/CNTs10;CNTs5含量分别为12%和14%时,复合材料的体积电阻率分别为0.92Ω·cm和0.52Ω·cm。扫描电子显微镜分析发现,随着CNTs含量增加,复合材料表面暴露的CNTs5数量逐渐增多,当CNTs10含量≥12%和CNTs5含量≥10%时出现一定的团聚。CNTs5含量为12%的复合材料综合性能最佳,其体积电阻率为0.92Ω·cm、拉伸强度为26.4 MPa、断裂伸长率为267.7%、撕裂强度为46.0 N/cm;在3.7 V直流电压下通电12 min,可从28℃上升到36℃,20 min后达到38℃,随后温度缓慢上升,该复合材料在热敷保健和医疗器械领域具有良好的应用前景。     

Scale formation in coal liquefaction reactor using FeS catalysts

The origin and formation behavior of scale in a coal liquefaction reactor, in which disposable catalysts such as red mud-sulfur were used, has been investigated by means of model experiments. The scale formed in the continuous coal liquefaction reactor which operated at a throughput of 0.1 t/d was analyzed with an electron probe microanalyzer (EPMA), scanning electron microscope (SEM), X-ray and scanning Auger electron microscope (SAM) techniques. It was observed in the model experiments that the scale formed on the surface of stainless steel (SUS-316) at temperatures higher than 250°C. The amount of scale formed was found to depend on the reaction temperature, the exposure time and the sulfur content of the catalyst. The scale formed in the continuous reactor collected on the walls of the tube, preheater and reactor. It was found that the scale was derived from two sources, the coal paste (catalyst, inorganic components in coal and unreacted coal) and the sulfidation of reactor materials.     

Ni-based supported catalysts from layered double hydroxides: Tunable microstructure and controlled property for the synthesis of carbon nanotubes

The carbon nanotubes (CNTs) with straight and helical nanostructures have been synthesized by catalytic chemical vapor deposition of acetylene over a series of Ni-based supported catalysts, which were formed from Ni–Mg–Al layered double hydroxide precursors (LDHs) synthesized through homogenous decomposition of urea under hydrothermal conditions. The materials were characterized by power X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), temperature-programmed reduction experiments (TPR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The results showed that the introduction of Mg into Ni-based supported catalysts could effectively improve the catalytic activities for the growth of CNTs, mainly proceeding from the inhibition effect of spinel phases formed in calcined LDHs on the agglomeration of metallic Ni particles. Furthermore, it is found interestingly that the addition of Mg also could induce the formation of helical structured CNTs with outer diameters of 20 nm and that the higher Mg content gave rise to the more helical nanotubes. The present work provides a simple and facile way to prepare metal-supported catalysts with a good dispersion of catalytically active metal particles for the growth of straight and helical CNTs.     

碳纳米管/炭复合材料的制备及其性能的研究

对碳纳米管（CNTs）／炭复合材料的形态结构及力学性能进行了研究。采用XRD、Instronl211万能实验机等手段研究了碳纳米管的加入量对复合材料的结构和性能的影响，得出了CNTs／C复合材料的d002、石墨化度、Lc及La与CNTs加入量之间的相关性。结果表明，随着碳纳米管含量的增加，复合材料d002呈下降趋势，石墨化度呈上升趋势。材料的拉伸强度主要和碳纳米管与基体之间的结合力以及它们之间的界面积有关；随着碳管含量的增加，在开始阶段其拉伸强度呈增加的趋势，当碳纳米管含量达到25％时，拉伸强度达到最大值25．5MPa，随后下降，当CNTs含量增加到30％，拉伸强度降到10．6MPa，之后保持不变；而拉伸模量在最初阶段增加缓慢，当碳纳米管含量大于22％时，则一直呈上升趋势。     

Thermal and electrical properties of carbon nanotubes based polysulfone nanocomposites

Carbon nanotubes (CNTs)-reinforced polysulfone (PSU) nanocomposites were prepared through solution mixing of PSU and different weight percent of multi-walled carbon nanotubes (MWCNTs). Thermal properties of nanocomposites were characterized using thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA studies revealed an increase in thermal stability of the PSU/MWCNTs nanocomposites, which is due to the hindrance of the nanodispered carbon nanotubes to the thermal transfer in nanocomposites and also due to higher thermal stability of CNTs. Morphological properties of nanocomposites were characterized by high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscope (FESEM). The influence of CNTs loading on electrical properties of PSU/MWCNTs nanocomposites was studied by the measurement of AC and DC resistivity. Dielectric study of nanocomposites was carried out at different frequencies (10 Hz–1 MHz) by using LCR meter. An increase in dielectric constant and dielectric loss was observed with increase in CNTs content, which is due to the interfacial polarization between conducting CNTs and PSU.     

Functional cellulose fibers via polycarboxylic acid/carbon nanotube composite coating

In this study, carbon nanotubes (CNTs) were stabilized on a cotton surface using 1,2,3,4-butanetetracarboxylic acid (BTCA) as a crosslinking agent and sodium hypophosphite as a catalyst. The influence of CNTs on the performance of the cellulose fiber was investigated using a Raman spectrophotometer, thermogravimetric analyzer, a scanning electron microscope, electrical contacting equipment, and an electromagnetic field detector. The possible interactions between CNTs, a crosslinking agent, and cellulose functional groups at the surface were elucidated by Raman spectroscopy. The results indicate that the stabilized CNTs modify the surface of the fibers and increase the functionality and thermal stability of the substrate. SEM showed a uniform coating of CNTs on the fiber surface.     

The imaging mechanism, imaging depth, and parameters influencing the visibility of carbon nanotubes in a polymer matrix using an SEM

Visualization of embedded carbon nanotubes (CNTs) in polymer using a scanning electron microscope (SEM) has been established as a convenient technique to evaluate CNT dispersion. This technique is known as voltage contrast imaging and is different from material contrast and topographic contrast imaging. By investigating CNT/epoxy composites the voltage contrast imaging theory is further understood. Trapping of electrons at the CNT/epoxy interface induces a local potential difference which enhances the image contrast. By coating the composite with a polymer film of different thicknesses the imaging depth (i.e. from how deep the CNTs can be seen) is determined to be up to 250 nm, and is a function of the accelerating voltage of the SEM. Visibility of CNTs is found to be sensitive to the CNT dispersion and concentration, as well as to the accelerating voltage.