Growth of Aligned Carbon Nanotubes through Microwave Plasma Chemical Vapor Deposition

Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550~C. The experimental results show that both the self-bias potential and the density of the catalyst particles are responsible for the alignment of CNTs. When the catalyst particle density is high enough, strong interactions among the CNTs can inhibit CNTs from growing randomly and result in parallel alignment.     

Electric-Arc Plasma Installation for Preparing Nanodispersed Carbon Structures

An electric-arc plasma installation operated in the hidden anode arrangement is constructed and used for the preparation of carbon nanostructures. A contracted plasma arc generated by a plasma torch using an inert gas is used as heat source. The average mass temperature of arc is higher than 10^4 K, while its power density, which is directly transferred onto the electrode （anode）, is - 2 kW/mm^2. The anode contact area formed on the electrode moves against the arc by way of shifting the electrode and is hidden completely in the interior of plasma gas stream moving towards it. As a result of both the direct plasma attack and the opposite movement of streams in the hidden anode contact area, a temperature higher than 6000 K is reached. Thus, intensive vaporization takes place, which forms a saturated plasma-gas-aerosol phase of the initial material of electrode （anode）. This gas phase is mixed in and carried by the plasma stream. Over that mixed plasma stream, a controlled process of quenching （fixation） is carried out by twisted turbulent fluid streams. After the fixation, the resultant carbon nano-structures are caught by a filter and collected in a bunker.     

Plasma Syntheses of Carbon Nanotube-Supported Pt-Pd Nanoparticles

It is reported that the highly dispersed Pt nanoparticles on carbon nanotubes can be synthesized under mild conditions by in situ plasma treatment.The carbon nanotube was pretreated by O₂ plasma to transform into oxide carbon nanotubes（O-CNTs）,and then it was mixed with the precursors（the mixture of H₂ PtCl₆and PdCl₆）.After that,the O-CNTs and the precursors were simultaneously treated by H₂ plasma.The precursors were transformed into Pt-Pd nanoparticles（NPs）and the O-CNTs transformed into CNT.The synthesized CNT-based Pt-Pd nanoparticles were characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy.All the analysis showed that the Pt-Pd nanoparticles were deposited on CNT as a form of face-centered cubical structure.     

Plasma Modification of Activated Carbon Fibers for Adsorption of SO_2

Viscose-based activated carbon fibers(VACFs)were treated by a dielectric-barrier discharge plasma under the feed gas of N_2.The surface functional groups of VACFs were modified to improve the adsorption and catalysis capacity for SO_2.The surface properties of the untreated and plasma-treated VACFs were diagnosed by SEM,BET,FTIR,and XPS,and the adsorption capacities of VACFs for SO_2 were also compared and discussed.The results show that after the plasma treatment,the external surface of VACFs was etched and became rougher,while the surface area and the total pore volume decreased.FTIR and XPS revealed that nitrogen atoms were introduced onto the VACFs surface and the distribution of functional groups on the VACFs surface was changed remarkably.The adsorption characteristic of SO_2 indicates that the plasmatreated VACFs have better adsorption capacity than the original VACFs due to the nitrogen functional groups and new functional groups formed in modification,which is beneficial to the adsorption of SO_2.     

A New Grade Carbon Black Produced by Thermal Plasma Process

This paper presents a new route about producing carbon black,by wich the natural gas cracking is carried out in the absence of oxygen thanks to an electric energy supply externally given by a plasma jet.The carbon black produced by this process has a narrow size distribution and a small average diameter of 38nm as well as a highly branched aggregate.The higher DBP value of 1.40ml/g shows it should be a high structure carbon black.The FTIR spectra shows that there are lots of aromatic c-c bonds and a large amount of nitrogen-coutaining functional groups on the carbon blacks surface,such as-NH,-CN as we3ll as -CH,-OH,-COOH groups.     

快中子活化分析检测爆炸物方法研究

叙述了快中子活化法检测隐蔽爆炸物的原理、方法及其优点。采用K-400高压倍加器产生的14MeV快中子对TNT、黑索金、硝胺及土制炸药等4种炸药、10余种常见物品和用土壤层覆盖的TNT样品进行快中子活化分析,测定各种样品的氮氧含量,建立被测物单位质量氮和氧计数率的二维分布,取得了爆炸物识别特征区,并用计算机模式识别方法进行判别。结果表明,此方法误判率和漏判率较低。Monte-Carlo模拟结果显示,在距中子源15m以外,基本无辐射剂量,被测物经检测1h后,总剂量小于环境本底剂量。本方法可用于远程控制快中子活化多探测器阵列检测爆炸物。     

Carbon Dioxide Reforming of Methane to Syngas by Thermal Plasma

Experiments were conducted on syngas preparation from dry reforming of methane by carbon dioxide with a DC arc plasma at atmospheric pressure. In all experiments, nitrogen gas was used as the working gas for thermal plasma to generate a high-temperature jet into a horizontal tube reactor. A mixture of methane and carbon dioxide was fed vertically into the jet. In order to obtain a higher conversion rate of methane and carbon dioxide, chemical energy efficiency and fuel production efficiency, parametric screening studies were conducted, in which the volume ratio of carbon dioxide to methane in fed gases and the total flux of fed gases were taken into account. Results showed that carbon dioxide reforming of methane to syngas by thermal plasma exhibited a larger processing capacity, higher conversion of methane and carbon dioxide and higher chemical energy efficiency and fuel production efficiency. In addition, thermodynamic simulation for the reforming process was conducted. Experimental data agreed well with the thermodynamic results, indicating that high thermal efficiency can be achieved with the thermal plasma reforming process.     

Performance of Cobalt-Based Fischer-Tropsch Synthesis Catalysts Using Dielectric-Barrier Discharge Plasma as an Alternative to Thermal Calcination

Co-based catalysts were prepared by using dielectric-barrier discharge （DBD） plasma as an alternative method to conventional thermal calcination. The characterization results of N2-physisorption, temperature programmed reduction （TPR）, transmission electron microscope （TEM）, and X-ray diffraction （XRD） indicated that the catalysts prepared by DBD plasma had a higher specific surface area, lower reduction temperature, smaller particle size and higher cobalt dispersion as compared to calcined catalysts. The DBD plasma method can prevent the sintering and aggregation of active particles on the support due to the decreased treatment time （0.5 h） at lower temperature compared to the longer thermal calcination at higher temperature （at 500~C for 5 h）. As a result, the catalytic performance of the Fischer-Tropsch synthesis on DBD plasma treated Co/Si02 catalyst showed an enhanced activity, C5＋ selectivity and catalytic stability as compared to the conventional thermal calcined Co/SiO2 catalyst.     

臭氧氧化改性碳纳米管对铀的吸附性能

通过臭氧氧化改性方法制备含有大量含氧官能团的改性碳纳米管(CNT)。采用有机元素分析、X射线光电子能谱(XPS)元素分析以及Boehm滴定法分别测得样品的表面含氧量、总含氧量以及不同含氧官能团含量,并对产物的比表面积、孔体积和孔径进行测定。结果表明,改性后含氧功能团数量增加了3~7倍,并且这种臭氧改性技术受温度影响显著。然后,考察了改性CNT对铀的吸附性能,对吸附条件进行优化。结果表明,未经改性的CNT样品的吸附效果较差,铀去除率仅为78.0%,而改性后的CNT对铀的吸附效果有显著提高,铀去除率高达95.0%以上,表明含氧量的增加显著提高了改性物对铀的吸附效果。     

Surface Activation of Plane and Curved Automotive Polymer Surfaces by Using a Fittable Multi-Pin DBD Plasma Source

In this work, surface activation of automotive polymers using atmospheric pressure plasmas was investigated. The aim was to increase the polar fraction of the surface energy of both plane and convex polymer devices with a radius in the range of 30 mm. For this purpose, a fittable low temperature atmospheric pressure plasma source based on capacitively coupled multi-pin electrodes was set up and applied. Each single electrode generates a treatment spot of approximately 2 cm2 with a tunable power density of up to 1.4 W/cm2. The surface energy was evaluated by contact angle measurements. After treatment at a low energy density of 1.01 J/cm2, the polar fraction of the surface energy of the investigated polymers was increased by a factor of 3.3 to 132, depending on the polymer materials. It was shown that by applying the presented fittable plasma source, this effect is independent of the surface radius of the polymer sample.     

用于储氢材料的碳/掺杂碳气凝胶研究

通过溶胶凝胶工艺,以间苯二酚和甲醛为原料,采用常压干燥法制备有机气凝胶和金属掺杂有机气凝胶;在氮气保护下,经1050℃高温碳化获得碳/掺杂碳气凝胶;通过CO₂活化工艺优化样品微结构、提高其比表面积,获得了比表面积达2582m²/g的碳气凝胶样品。使用比表面积与孔隙度分析仪、扫描电镜（SEM）、透射电镜（TEM）、X射线衍射仪（XRD）对样品微观结构和气体吸附性能进行表征。通过溶胶 凝胶工艺实现了过渡金属的均匀掺杂,并研究了金属掺杂对碳气凝胶微结构特性的影响。结果表明,适当的金属掺杂可提高样品的比表面积和微孔体积。     

A Study of Diamond-Like Carbon Thin Films Prepared by Microwave Plasma Chemical Vapour Deposition

In order to deposit good films, we need to study the uniformity of plasma density and the plasma density under different gas pressures and powers. The plasma density was diagnosed by a Langmuir probe. The optical emission spectroscopy （OES） of CH4 and H2 discharge was obtained with raster spectroscopy, with characteristic peaks of H and CH achieved. Diamond-like carbon films were achieved based on the study of plasma density and OES and characterized by atomic force microscope （AFM）, X-ray diffraction instrument （XRD）, Raman spectroscope and profiler.     

缓蚀剂SDS+CTAB复配溶液中碳钢电化学腐蚀性能的影响因素研究

通过中心复合设计（CCD）法设计实验并结合动电位极化曲线和电化学阻抗谱（EIS）的测量,研究了Cl^-浓度、温度、pH值、SDS浓度和CTAB浓度5种因素对碳钢腐蚀性能的影响,确定其显著性影响因素,从而探索有机缓蚀剂SDS和CTAB复配溶液配比及使用环境最佳区间。结果表明：SDS和CTAB及两者的复配溶液均对碳钢具有良好的缓蚀效果,两者混合使用的复配溶液具有很好的协同作用。Cl^-浓度为0.01 mol/L、pH值为12、温度为10 ℃、SDS浓度为150 ppm、CTAB浓度为20 ppm时缓蚀效果最佳。     

Signal Detection of Carbon in Iron-Based Alloy by Double-Pulse Laser-Induced Breakdown Spectroscopy

Although single-pulse lasers are often used in traditional laser-induced breakdown spectroscopy (LIBS) measurements, their measurement outcomes are generally undesirable be?cause of the low sensitivity of carbon in iron-based alloys. In this article, a double-pulse laser was applied to improve the signal intensity of carbon. Both the inter-pulse delay and the combina?tion of laser wavelengths in double-pulse laser-induced breakdown spectroscopy (DP-LIBS) were optimized in our experiment. At the optimized inter-pulse delay, the combination of a first laser of 532 nm and a second laser of 1,064 nm achieved the highest signal enhancement. The proper?ties of the target also played a role in determining the mass ablation enhancement in DP-LIBS con?guration.     

Effects of Dielectric Barrier Discharge Plasma Treatment on Pentachlorophenol Removal of Granular Activated Carbon

The pentachlorophenol(PCP)adsorbed granular activated carbon(GAC)was treated by dielectric barrier discharge(DBD)plasma.The effects of DBD plasma on the structure of GAC and PCP decomposition were analyzed by N_2 adsorption,thermogravimetric,scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and gas chromatographymass spectrometry(GC-MS).The experimental data of adsorption kinetics and thermodynamics of PCP on GAC were fitted with different kinetics and isotherm models,respectively.The results indicate that the types of N_2 adsorption isotherm of GAC are not changed by DBD plasma,while the specific surface area and pore volume increase after DBD plasma treatment.It is found that the weight loss of the saturated GAC is the highest,on the contrary,the weight loss of DBD treated GAC is the least because of reduced PCP residue on the GAC.The XPS spectra and SEM image suggest that some PCP on the GAC is removed by DBD plasma,and the surface of GAC treated by DBD plasma presents irregular and heterogeneous morphology.The GC-MS identification of by-products shows that two main dechlorination intermediate products,tetrachlorophenol and trichlorophenol,are distinguished.The fitting results of experimental data of adsorption kinetics and thermodynamics indicate that the pseudo-first-order and pseudo-second order models can be used for the prediction of the kinetics of virgin GAC and DBD treated GAC for PCP adsorption,and the Langmuir isotherm model fits better with the data of adsorption isotherm than the Freundlich isotherm in the adsorption of PCP on virgin GAC and DBD treated GAC.     

用碳纳米管从硝酸溶液中回收镅

研究了用碳纳米管从放射性废硝酸溶液中进行镅的回收。在浓硝酸溶液中,碳纳米管对镅的吸附率小于1％;随着硝酸浓度的降低,镅的吸附率迅速升高,当溶液的pH值大于5时,碳纳米管对镅的吸附率达到99.95％以上。用1．5mol／L硝酸进行解吸,一次解吸能够从碳纳米管回收99％以上的镅。     

Plasma treatment for enhancement of the sorption capacity of carbon fabric

In this work we carried out an experimental investigation into enhancement of the sorption capacity of carbon fabric using plasma treatment methods.Carbon fabric is based on viscose fiber and is hydrophobic by nature.Enhancement of the fabric sorption capacity is required for its application in medicine.For this purpose,two plasma treatment methods were considered,i.e.atmospheric nonequilibrium radiofrequency(RF)discharge and a vacuum RF plasma source with an external magnetic field.Samples treated by atmospheric discharge demonstrated aging effects during the first week after treatment.The sorption capacity of samples treated by the RF plasma source was stable over the same period and reached values as high as 0.95.Parameters of the beam created by the vacuum RF plasma source were analyzed and dependences of the fabric sorption capacity and specific surface area on plasma treatment time were investigated.We found that sorption capacity reached its maximum value after 30 min of treatment and did not change significantly if processing was continued,while the specific surface area reached its maximum after 3 min of treatment and quickly decreased after that.It was found that the micropore structure of the fabric remained almost the same during plasma treatment.The volume of mesopores in a unit of the fabric mass(specific volume)doubled during the first 5 min of treatment and returned to initial values after 30 min of treatment.The sorption capacity continued to increase even when the specific surface area decreased after reaching its peak value.This indicates the important role of surface functional groups formed on carbon fibers during plasma treatment.This is consistent with the results of x-ray photoelectron spectroscopy analysis showing changes in surface oxidation during plasma treatment.     

Incorporation of Nitrogen into Amorphous Carbon Films Produced by Surface-Wave Plasma Chemical Vapor Deposition

In order to study the influence of nitrogen incorporated into amorphous carbon films, nitrogenated amorphous carbon films have been deposited by using surface wave plasma chemical vapor deposition under various ratios of N2/CH4 gas flow. Optical emission spectroscopy has been used to monitor plasma features near the deposition zone. After deposition, the samples are checked by Raman spectroscopy and x-ray photo spectroscopy (XPS). Optical emission intensities of CH and N atom in the plasma are found to be enhanced with the increase in the N2/CH4 gas flow ratio, and then reach their maximums when the N2/CH4 gas flow ratio is 5%. A contrary variation is found in Raman spectra of deposited films. The intensity ratio of the D band to the G band (ID/IG) and the peak positions of the G and D bands all reach their minimums when the N2/CH4 gas flow ratio is 5%. These show that the structure of amorphous carbon films has been significantly modified by introduction of nitrogen。     

Solving the Stand-off Problem for Magnetized Target Fusion: Plasma Streams as Disposable Electrodes, Together with a Local Spherical Blanket

In a fusion reactor based on the magnetized target fusion approach, the permanent power supply has to deliver currents up to a few mega-amperes to the target dropped into the reaction chamber. All the structures situated around the target will be destroyed after every pulse and have to be replaced at a frequency of 1–10 Hz. In this paper, an approach based on the use of spherical blanket surrounding the target, and pulsed plasma electrodes connecting the target to the power supply, is discussed. A brief analysis of the processes associated with creation of plasma electrodes is presented.     

Study of Coincidence Doppler Broadening in Carbon Nanotubes

Coincidence Doppler broadening measurements of positron annihilation for multi- walled carbon nanotubes, double-walled carbon nanotubes, single-walled carbon nanotubes and graphite were performed. The ratio curves of the Doppler broadening for these samples to silicon were obtained. It is shown that there are distinct peaks at the position of 10xl0-arn0c for both carbon nanotubes and graphite, however the amplitudes of the peaks are not the same. We have the opinion that these peaks arise from the annihilation of positron with the 2s and 2p electron of carbon element.