Pulsed Plasma Assisted Growth of Vertically Aligned Carbon Nanotubes at Low Temperature on Mo Substrate

Plasma Chemistry and Plasma Processing - Aligned carbon nanotubes (CNTs)/carbon nanofibers (CNFs) are synthesized at temperatures of 350, 400 and 450 °C using pulsed plasma enhanced...     

Electrical and Optical Characterization of Acetylene RF CCP for Synthesis of Different Forms of Hydrogenated Amorphous Carbon Films

Plasma Chemistry and Plasma Processing - We present an electrical and spectroscopic characterization of Acetylene plasma used for deposition of different forms of hydrogenated amorphous carbon...     

Plasma Assisted Catalytic Conversion of CO2 and H2O Over Ni/Al2O3 in a DBD Reactor

Plasma Chemistry and Plasma Processing - We present an innovative approach for reacting carbon dioxide and water to give syngas by combining heterogeneous catalysis and non-thermal plasma...     

Application of a Novel CO2 DC Thermal Plasma Torch Submerged in Aqueous Solution for Treatment of Dissolved Carboxylic Acid

Plasma Chemistry and Plasma Processing - A novel direct current (DC) plasma torch, operating with a gas mixture consisting of carbon dioxide and hydrocarbon (methane), has been adapted and used for...     

Hydrogen Production from Methane Decomposition Using a Mobile and Elongating Arc Plasma Reactor

Plasma Chemistry and Plasma Processing - Hydrogen and solid carbon were produced through methane decomposition in a plasma reactor with a parallel set of screw type helix and rod-like electrodes....     

Analysis of functional groups on the surface of plasma-treated carbon nanofibers

Plasma chemically modified carbon nanofibers were characterized by X-ray photoelectron spectroscopy with regard to the content of carbon, oxygen, and nitrogen and the contribution of carboxylic groups or ester, carbonyl and hydroxylic groups or ether on the surface. Unfortunately, X-ray photoelectron spectroscopy only provides an average value of the first 10 to 15 molecular layers. For comparison, depth profiles were measured and wet chemical methods were applied to estimate the thickness of the functionalized layer and the distribution of oxygen-containing functional groups within the near-surface layers. The results indicate that the fiber surface is covered by a monomolecular oxygen-containing layer and that plasma treatment allows a complete oxygen functionalization of the uppermost surface layer. The best conditions for plasma treatment found within the set of parameters applied to generate complete functionalization are: plasma gas O(2)/Ar ratio 1:1, gas pressure 1-1.5 hPa, plasma power 80 W, treatment time >or= 5 min. Additionally, three quick and easy methods are presented to estimate the efficiency of plasma treatment with regard to surface functionalization: pyrolysis, contact angle measurements, and light permeability measurements of aqueous carbon nanofiber suspensions.     

Increase in the plasma protein binding of weakly basic drugs in carbon tetrachloride-intoxicated rats.

Plasma protein binding of weakly basic drugs such as propranolol and quinidine was determined in rats with carbon tetrachloride (CCl4)-induced hepatic disease. Free fractions of propranolol and quinidine in the plasma of rats at 24 h after CCl4-intoxication were decreased by 41 and 30%, respectively, compared to those of control rats. An addition of Tris (butoxyethyl) phosphate (TBEP), a specific displacer for basic drugs from alpha 1-acid glycoprotein (AGP), to the plasma increased the free fractions of the basic drugs, resulting in no difference in the extent of the plasma free fraction of each drug between control and CCl4-intoxicated rats. Plasma concentration of AGP in CCl4-intoxicated rats was elevated 2.7-fold of that in control rats at 24 h after the CCl4 intoxication and reached a peak of 4.8-fold elevation at 48 h. A regression analysis revealed a high degree of positive correlation between ratios of bound to free fraction of propranolol and plasma concentrations of AGP. These results suggest that the plasma protein binding of the basic drugs was increased mainly due to the rise in the plasma AGP concentration in CCl4-intoxicated rats.     

New studies of the plasma emission detector

Being an element-selective detector, the plasma emission detector was used to determine carbon in organic compounds. Experiments were carried out with the aid of osculating interference filters and lock-in amplifiers. The obtained signals were processed by a fast-Fourier-transform analyzer to study their frequency spectra. Results are given for the detection of carbon. Furthermore studies on the influence of angle-adjustment, microwave power, photomultiplier voltage and oscillation frequency on the determination of fluorine in organic compounds were carried out and results for detection limits and dynamic range of this method are presented.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Carburizing of titanium with plasma jets under reduced pressure

The carburizing of titanium with argon-methane (0.1%) and argon-methane (0.1%)-hydrogen (2%) plasma jets at a pressure of 200 Torr was studied. The carburizing of titanium was not successful with the argon-methane plasma jet because the specimen was covered with graphitic carbon. A hard and thick TiC layer was formed by the argon-methane-hydrogen plasma jet in a short time without the deposition of graphitic carbon. Emission spectra from the plasma jets show that the addition of hydrogen increases the amount of CH radicals as well as decreases the amount of C₂ and C in the plasma jet. The decrease of C₂ and C suppresses the deposition of graphitic carbon and enhances the TiC formation.Partly presented at Gordon Research Conference on Plasma Chemistry, August 11–15, 1986, Tilton, New Hampshire.     

Analytical investigation of plasma-treated carbon fibres

As-grown and heat-treated vapour grown carbon fibres (VGCF) in the as-prepared state, washed in HCl/H(2)O, and treated in O(2) plasma for different periods have been investigated by means of XPS and scanning electron microscopy (SEM). The surface energy of the carbon fibres before and after plasma treatment was determined from the wetting contact angle. Washing introduced hydroxyl, carbonyl and carboxyl groups onto the fibre surfaces and oxygen plasma treatment increases the total atomic concentration of oxygen up to 17%. This is in good agreement with the value of the polar component of the surface energy. Plasma treatment also enhanced the fibre surface porosity (by etching).     

Plasma polymerization of cyano compounds

Plasma polymerizations of three cyano compounds—acrylonitrile (AN), 1,2-dicyanoethylene (FN), and tetracyanoethylene (TCE)—were investigated by FT IR and XPS, and the transforamtion of cyano groups during the plasma polymerization was discussed. The results pointed out an aspect of the preparation of plasma films with cyano groups. Plasma polymerizations of AN, FN, and TCE deposited brown or dark brown films that contained carbon, nitrogen, and oxygen. The elemental composition of the plasma films, especially N/C atomic ratio, showed a monomer dependence but no rf power dependence. The plasma films contained amide and amino groups, and ketene-imine and conjugated — C = N — structures as well as cyano groups as nitrogen functionalities, and carbonyl and carboxyl groups as oxygen functionalities. For the preparation of plasma films with cyano groups, compounds with more than two cyano groups themselves are not suitable as monomers. The operation of plasma polymerization under mild plasma conditions at low rf power and in no oxygen atmosphere is favorable for the preparation of plasma films with cyano groups. © 1992 John Wiley & Sons, Inc.     

Products of high-temperature plasma conversion of solid production and consumption wastes. Comparative quality assessment of plasma conversion and incineration products

The plasma technology provides the possibility to prevent hazardous industrial waste formation. Moreover, it is reasonable to include into the pyrogas treatment technology the catalytic stages of steam and carbon dioxide reforming and Fischer-Tropsch hydrocarbon synthesis. Plasma technology allows waste to serve as an inexhaustible source of raw materials for production of electricity, hydrogen, and fuels.     

射频放电等离子体中CO2及CO2-H2混合气转化反应的原位研究

Currently, worldwide attention is focused on controlling the continually increasing emissions of greenhouse gases, especially carbon dioxide. To this end, a number of investigations have been carried out to convert the carbon dioxide molecules into value-added chemicals. As carbon dioxide is thermodynamically stable, it is necessary to develop an efficient carbon dioxide utilization method for future scaled-up applications. Recently, several approaches, such as electrocatalysis, thermolysis, and non-thermal plasma, have been utilized to achieve carbon dioxide conversion. Among them, non-thermal plasma, which contains chemically active species such as high-energy electrons, ions, atoms, and excited gas molecules, has the potential to achieve high energy efficiency without catalysts near room temperature. Here, we used radio-frequency (RF) discharge plasma, which exhibits the non-thermal feature, to explore the decomposition behavior of carbon dioxide in non-thermal plasma. We studied the ionization and decomposition behaviors of CO₂ and CO₂-H₂ mixtures in plasma at low gas pressure. The non-thermal plasma was realized by our custom-made inductively coupled RF plasma research system. The reaction products were analyzed by on-line quadrupole mass spectrometry (differentially pumped), while the plasma status was monitored using an in situ real-time optical emission spectrometer. Plasma parameters (such as the electron temperature and ion density), which can be tuned by utilizing different discharge conditions, played significant roles in the carbon dioxide dissociation process in non-thermal plasma. In this study, the conversion ratio and energy efficiency of pure carbon dioxide plasma were investigated at different values of power supply and gas flow. Subsequently, the effect of H₂ on CO₂ decomposition was studied with varying H₂ contents. Results showed that the carbon dioxide molecules were rapidly ionized and partially decomposed into CO and oxygen in the RF field. With increasing RF power, the conversion ratio of carbon dioxide increased, while the energy efficiency decreased. A maximum conversion ratio of 77.6% was achieved. It was found that the addition of hydrogen could substantially reduce the time required to attain the equilibrium of the carbon dioxide decomposition reaction. With increasing H₂ content, the conversion ratio of CO₂ decreased initially and then increased. The ionization state of H₂ and the consumption of oxygen owing to CO₂ decomposition were the main reasons for the V-shape plot of the CO₂ conversion ratio. In summary, this study investigates the influence of power supply, feed gas flow, and added hydrogen gas content, on the carbon dioxide decomposition behavior in non-thermal RF discharge plasma.     

Non-thermal plasma technology for the conversion of CO2

The conversion of carbon dioxide is vital if we are to avoid the catastrophic consequences that will result from further global temperature rise as a result of burning fossil fuels. Current techniques, such as catalytic conversion and biochemical processes, are each associated with their own drawbacks such as catalyst deactivation and high energy input. Plasma processes are gaining increasing interest as they have the potential to reduce a greater amount of atmospheric environmental pollutants at any one time due to an increased throughput, whilst using a smaller reactor with improved energy efficiency and near-zero emissions. Non-thermal plasma can dissociate stable molecules, such as CO₂, at temperatures as low as room temperature. It is this key feature which makes plasma conversion such a promising technology in the conversion and utilisation of CO₂. Furthermore, possible products from plasma processes include fuels and chemicals, such as methanol and syngas, which have a high market value; hence potentially making the process feasible on an industrial scale. This paper discusses recent advances in the use of plasma processes for carbon dioxide conversion, along with the future outlook of this technology and the impact these techniques could have on the chemical and energy industries.     

Tuning the Surface Properties of Oxygen-Rich and Nitrogen-Rich Plasma Polymers: Functional Groups and Surface Charge

Controlling the concentration and nature of functional groups in plasma polymer films by adjusting the flow ratio of constituent precursor gases can be exploited to tune the surface charge of the resulting coating. Plasma polymer films containing various concentrations of nitrogen and oxygen functional groups were deposited in a low-pressure capacitively-coupled glow discharge reactor by plasma polymerization of binary gas mixtures of a hydrocarbon (ethylene or butadiene) and a heteroatom source gas (ammonia and/or carbon dioxide). Increasing the flow ratio of heteroatom to hydrocarbon gases increased the concentration of bonded nitrogen or oxygen, including that of primary amine or carboxylic groups as determined by X-ray photoelectron spectroscopy and chemical derivatization procedures. The zeta potential of samples was measured using an electro-kinetic analyser in a diluted sodium chloride solution. The deposition parameters controlled the composition of the coatings, allowing to tune the surface charge to either positive (ammonia based films)—or negatively (carbon dioxide base films) values at physiological pH.     

Titanium-supported nickel-copper oxide catalysts for oxidation of carbon(II) oxide

Nickel-copper compositions for catalytic oxidation of carbon(II) oxide to carbon(IV) oxide were prepared by impregnation of oxide films on titanium surface, obtained by plasma electrolytic oxidation followed by annealing. Plasma electrolysis oxide coatings with a layer thickness of 5 to 50 μm were generated using different electrolytes. The compositions were studied by X-ray powder diffraction, X-ray spectral analysis, and electron microscopy, and moisture absorption of the initial plasma electrolytic structures was estimated. A linear correlation was found between the overall concentration of nickel and copper (4 to 25 mol %) in the surface layer of ∼2–5-μm compositions and their catalytic activity. The overall concentration of nickel and copper was found to increase in parallel with the moisture absorption of plasma electrolytic oxidation coatings. Nickel-copper compositions based on plasma electrolytic oxidation coatings generated in a silicate electrolyte displayed the best catalytic, mechanical, and adhesion properties.     

Three-Dimensional Non-equilibrium Modeling on the Characteristics of the Dual-Jet Direct-Current Arc Plasmas

Plasma Chemistry and Plasma Processing - In this paper, the three-dimensional (3-D) two-temperature modeling on the characteristics of the dual-jet DC arc argon plasmas under different plasma...     

The Effect of the Process Parameters on the Composition and Properties of Silica-Like Films Deposited by Atmospheric Pressure PECVD in the System TEOS-He-O2

Plasma Chemistry and Plasma Processing - In this paper we report on a study of an atmospheric pressure plasma enhanced chemical vapor deposition process based on a simple dielectric barrier...     

Numerical Study of Jet–Target Interaction: Influence of Dielectric Permittivity on the Electric Field Experienced by the Target

Plasma Chemistry and Plasma Processing - This work presents a study of the influence of dielectric permittivity on the interaction between a positive pulsed He plasma jet and a 0.5 mm-thick...     

Gasification of Municipal Solid Wastes in Plasma Arc Medium

Many thermal processes have been developed in order to eliminate the municipal solid wastes or produce energy from them. These processes include a wide range of applications from the simplest burning system to plasma gasification. Plasma gasification is based on re-forming of molecules after all molecules convert to smaller molecules or atoms at high temperatures. In this work, the production of fuel gas is aimed by plasma gasification of municipal solid wastes in high temperatures. Because of this, a plasma reactor of the capacity of 10 kg h^?1 was designed which can gasify municipal solid wastes. Plasma gasification with and without steam and oxygen was performed in temperatures of 600, 800, 1000, 1200, 1400 and 1600 °C in the reactor. A gas mixture containing methane, ethane, hydrogen, carbon dioxide and monoxide, whose content varies with temperature, was obtained. It was found that plasma gasification (or plasma pyrolysis, PG), plasma gasification with oxygen (PGO) and plasma gasification with steam (PGS) were more prone to CO formation. A gas product which was consisted of 95% CO between 1200 and 1400 °C was produced. It was observed that a gas with high energy capacity may be produced by feeding oxygen and steam into the entrance of the high temperature region of the reactor.