Arc Plasma Method Research Articles

Characterization of NiO nanoparticles by anodic arc plasma method

NiO nanoparticles with average particle size of 25 nm were successfully prepared by anodic arc plasma method. The composition, morphology, crystal microstructure, specific surface area, infrared spectra, particle size distribution of product were analyzed by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected-area electron diffraction (SAED), Fourier transform infrared spectrum (FTIR) and Brunauer–Emmett–Teller (BET) N 2 adsorption. The experiment results shown that the NiO nanoparticles are bcc structure with spherical shape and well dispersed, the particle size distribution ranging from 15 nm to 45 nm with the average particle size is about 25 nm, and the specific surface area is 33 m 2/g.The infrared absorption band of NiO nanoparticles show blue-shifts compared with that of bulk NiO.

アークプラズマ法による金属ナノ粒子の生成速度に及ぼす諸因子の解析

Fe nanoparticles were prepared by DC arc plasma method under Ar, Ar-25%H2, Ar-50%H2, Ar-75%H2 and H2 flow. The diameter of arc plasma decreased significantly with increasing H2 mixing ratio, which was due to hydrogen induced thermal pinch effect. The generation rate of the Fe nanoparticles was significantly enhanced with the pinched arc plasmas. The numerical simulation with taking into consideration of Fe vaporization was carried out, and it was indicated that the arc temperature drastically increased due to the thermal pinch effect, and thereby Fe anode was efficiently heated, leading to the enhancement of Fe vaporization. Thus, the thermal pinch effect plays an important role on the generation rate of metallic nanoparticles in Ar-H2 arc plasma method.

Preparation and Characterization of NiO Nanoparticles by Anodic Arc Plasma Method

NiO nanoparticles with average particle size of 25 nm were successfully prepared by anodic arc plasma method. The composition, morphology, crystal microstructure, specific surface area, infrared spectra, and particle size distribution of product were analyzed by using X‐ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectrum, and Brunauer‐Emmett‐Teller (BET) N2 adsorption. The experiment results show that the NiO nanoparticles are bcc structure with spherical shape and well dispersed, the particle size distribution ranging from 15 to 45 nm with the average particle size is about 25 nm, and the specific surface area is 33 m2/g. The infrared absorption band of NiO nanoparticles shows blue shifts compared with that of bulk NiO.

Particle Size and Pore Structure Characterization of Silver Nanoparticles Prepared by Confined Arc Plasma

In the protecting inert gas, silver nanoparticles were successfully prepared by confined arc plasma method. The particle size, microstructure, and morphology of the particles by this process were characterized via X‐ray powder diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED). The N2 absorption‐desorption isotherms of the samples were measured by using the static volumetric absorption analyzer, the pore structure of the sample was calculated by Barrett‐Joyner‐Halenda (BJH) academic model, and the specific surface area was calculated from Brunauer‐Emmett‐Teller (BET) adsorption equation. The experiment results indicate that the crystal structure of the samples is face‐centered cubic (FCC) structure the same as the bulk materials, the particle size distribution ranging from 5 to 65 nm, with an average particle size about 26 nm obtained by TEM and confirmed by XRD and BET results. The specific surface area is 23.81 m2/g, pore volumes are 0.09 cm3/g, and average pore diameter is 18.7 nm.

Influence of Hydrogen Induced Thermal Pinch on Nanoparticle Formation in Arc Plasma

Fe nanoparticles were prepared by DC arc plasma method under Ar, Ar-50%H2 or H2 flow. The arc plasma was well constricted due to thermal pinch effect when Ar-50%H2 or H2 was used, and the generation ration of the Fe nanoparticles was significantly enhanced with the pinched arc. Our numerical simulation indicated that the Fe anode can be efficiently heated (close to boiling point of Fe) due to the thermal pinch effect, and thereby the generation ratio can be increased. Since the thermal pinch effect enhanced the arc flow velocity as well, the size of the resulting Fe nanoparticles was also influenced.

Fabrication and characterization of TiN–Ag nano-dice

TiN–Ag nanocomposite was synthesized by dc arc-plasma method. Microstructures of TiN–Ag nanocomposite were carefully characterized by powder X-ray diffraction method and transmission electron microscopy, and nano-morphologies by three-dimensional electron tomography. It was found that the surface of nanocrystalline TiN matrix was densely covered by finely dispersed Ag nanoparticles, and it was found that they were physically attached but not chemically bonded from their orientation relationships.

Vaporization mechanism from Sn–Ag mixture by Ar–H 2 Arc for nanoparticle preparation

The purpose of this paper was to describe the synthesis of Sn–Ag nanoparticles by an arc plasma method. Sn–Ag nanoparticles have been successfully prepared by DC arc plasma with hydrogen addition. The prepared nanoparticles were characterized by X-Ray diffraction, transmission electron microscopy and inductively coupled plasma-atomic emission spectrometry. The obtained results indicated that the nanoparticles have high-purity and spherical shape. The average diameter of the nanoaprticles with 100%-Ar arc was 19.8 nm and that with 50%-H 2 arc was 56.5 nm. Another purpose of this work is to investigate the vaporization behavior from molten Sn–Ag mixture with Ar and Ar–H 2 arc. We confirmed the vaporization enhancement of Sn from Sn–Ag mixture by hydrogen in arc plasma.

Corrosion behavior of TiN, TiAlN, TiAlSiN thin films deposited on tool steel in the 3.5 wt.% NaCl solution

TiN, TiAlN and TiAlSiN hard coatings were deposited onto AISI H13 tool steel by cathodic arc plasma method. X-ray diffraction (XRD) analysis confirmed that incorporation of Al and Si into TiN led to refinement of microstructure. From the results of potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) test conducted in an aerated 3.5% NaCl solution, the TiAlSiN film showed the best corrosion resistance with the lowest corrosion current density and porosity, the highest protective efficiency and total resistance (pore resistance plus charge transfer resistance).

A new approach towards improving the quality and yield of arc-generated carbon nanotubes

The paper reports the deterministic effects of a focusing electric field in improving the purity and yield of the arc-generated carbon nanotubes (CNTs). The method utilizes a focusing electrostatic field, which was superimposed on the arc symmetrically. The focusing voltage was varied from 0 to 1200 V at steps of 200 V and a number of cathode deposits, thus generated, were collected and thoroughly analysed in their totality with the help of weight balance, Raman spectroscopy, transmission electron microscopy and thermogravimetry. With the optimally configured focusing electric field, the arc generator is found to utilize nearly 85% of the consumed anode material, for converting into cathode deposit consisting of CNTs, as compared with about 35% in the conventional arc plasma method. The sample prepared under optimized conditions exhibited high oxidation temperature (851 °C) in the thermogravimetric analysis, negligible D band intensity along with a reduced G band line-width (14 cm−1) in the Raman spectrum, confirming the presence of high purity CNTs with a high relative yield.

Preparation and structure of carbon encapsulated copper nanoparticles

Carbon-encapsulated copper nanoparticles were synthesized by a modified arc plasma method using methane as carbon source. The particles were characterized in detail by transmission electron microscope, high-resolution transmission electron microscopy, selected-area electron diffraction, X-ray diffraction, thermogravimetric and differential scanning calorimetry. The encapsulated copper nanoparticles were about 30 nm in diameter with 3–5 nm graphitic carbon shells. The outside graphitic carbon layers effectively prevented unwanted oxidation of the copper inside. The effect of the ratio of He/CH4 on the morphologies and the formation of the carbon shell were investigated.

Effect of the Atmosphere on the Products of Arc Plasma Method

Plasma techniques have been used to synthesis of metal, metal compounds, and surface modification. In that processing, atmosphere is more important to the compositions and properties of nanoparticles and films. We found that the atmosphere has not only effected the compositions, but also plays a significant role on the morphologies of the products. By changing atmosphere based on different requirement, we obtained spherical Mn3O4 nanoparticles, mixture of hexangular Mn3O4 nanosheets and Mn+3O(OH) nanorods, and Mn6N2.58 nanoparticles coated with graphite layer. The compositions, structure and morphologies of the products were determined by x‐ray diffraction (XRD) and transmission electron microscopy (TEM), and electron diffraction (ED). Finally, we preliminarily discussed the reason of the effect of the atmosphere to the final products of arc plasma method.

Superconducting properties of in situ powder-in-tube-processedMgB2 tapes fabricated with sub-micrometre Mg powder prepared by an arc-plasmamethod

We fabricated in situ powder-in-tube-processedMgB2/Fe tapes using sub-micrometre Mg powder prepared by applying an arc-plasma method. Wefound that the use of this sub-micrometre Mg powder was very effective in increasing theJc values. Thetransport Jc value of 10 mol% SiC-added tapes fabricated with this sub-micrometre Mg powder reached275 A mm−2 at 4.2 K and 10 T. This value was about six times that of 5 mol% SiC-added tapesfabricated with commercial Mg powder. Microstructure analyses suggest that thisJc enhancement is primarily due to the smallerMgB2 grain size.

Preparation of manganese and their derivate compounds by arc plasma method

We synthesized a series of compounds by changing the plasma atmosphere. Besides manganese nanoparticles using hydrogen and helium as the plasma atmosphere, sheet-like MnC 8 and spherical Mn 6N 2.58 are also obtained adopting liquid steam as plasma atmosphere entirely by modifying arc plasma method. The compositions, structure and morphologies of the product were determined by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Finally, we preliminarily discussed the reason of the effect of the atmosphere to the final products of arc plasma method.

Plasma-Prepared Ni/Al2O3: Preparation, Characterization and Toluene Hydrogenation

Nano-nickel particles were prepared using hydrogen arc plasma method and new nano-nickel hydrogenation catalysts were prepared through calcinating mixtures of the plasma-prepared nano-nickel particles and a ?-alumina support. The catalysts were characterized by using SEM, XRD, and TPR. The activities of the catalysts were evaluated through the hydrogenation of toluene in a fixed be microreactor. Catalysts prepared by conventional comulling and impregnation methods were also examined for comparative purposes. The characterization results showed that the nano-nickel catalysts had an egg-shell structure in terms of nickel-alumina distribution, with most of the nickel located at the outer surface of the catalyst particles. The hydrogenation experiments showed that the nano-nickel catalyst provided much higher activities than those co-precipitated and impregnated nickel catalysts with similar nickel contents. However, both types of catalysts followed first-order reaction kinetics and similar activation energies were observed.

One-step synthesis of porous palladium nanostructures by H2+He arc plasma method

Porous palladium nanostructures were prepared on a copper sheet previously fixed over the plasma high-temperature area by H2+He arc plasma method. However, dispersed palladium nanoparticles with diameters in 50–90 nm were obtained on the inner wall of vacuum chamber. SEM, TEM, EDXA, XRD and BET were employed to characterize the palladium porous materials. SEM images show that porous palladium nanostructures are composed of spherical particles with diameters of 35 ± 3 nm. This special structure with large surface to volume ratio can be recycled easily for application in the field of catalysis.

Praparation of metal oxide particles by an arc plasma method

Praparation of metal oxide particles by an arc plasma method

Synthesis and phase structure of tantalum nanoparticles

In this work we report the synthesis of tantalum nanoparticles from bulk tantalum by hydrogen arc plasma method. The product obtained was investigated by ultraviolet (UV)–visible spectrum, X-ray diffractometer (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) analysis. The size of these particles is less than 10 nm and there are few defects on their surface. A strong ultraviolet absorption below 320 nm was observed. XRD analysis revealed that the product consist of tantalum and hexagonal δ-TaO nanoparticles. The tantalum nanoparticles were easily oxidized in the air to form δ-TaO due to high activity. The thermal stability of sample was analyzed by thermogravimetry/differential scanning calorimetry (TG/DSC) in the ambience of dry N 2 (containing less than 1% of oxygen).

Investigation of carbon nanotube deposits and their formation conditions by an arc-plasmamethod in water

In a DC arc-plasma method, in deionized water, used to synthesize multi-walled carbonnanotubes (MWCNTs), hard deposits collected on the surface of the cathode are the mainproduct rich in MWCNTs and they are easier to collect than the products collected inwater. The top surface of the deposit bestrewed with column-shaped clumps also gives ahint as to potential applications of the field emission. In order to increase the yield of thedeposits on the cathode surface, different parameters are used to investigate theirformation. An auto-formed chamber between two electrodes during the arc discharge isfound to have a determining effect on the formation of deposits on the cathode surface.Deposits are examined using SEM and TEM to investigate their structure and the CNTs inthem.

The effect of thermal treatment on the electrical properties of titanium nitride thin films by filtered arc plasma method

In this work, the titanium nitride (TiN) films were prepared by filtered arc plasma (FAP) method with thickness ranging from 7 to 75 nm. The structure of TiN film was determined by X-ray diffraction (XRD). Sheet resistance ( R □) and TCR were measured by four-point probe station and TCR measurement system respectively. The results indicate that R □ and TCR of TiN films are strongly thickness-dependent. After annealed above their individual critical temperature ( T c), all films experienced huge resistance increases and color variations. While annealed below T c, most of TiN films exhibited better resistance stability and repeatability than as-deposited TiN film. For extremely thin TiN film, like 7 nm, after annealed below T c, its TCR turned from positive to negative. T c for different TiN film was found strongly thickness-dependent from 200 to 600 °C.

A novel form of carbon micro-balls from coal

A novel form of ball-like carbon material with its size in micrometer range was prepared from coal with nickel as catalyst by arc plasma method. The carbon material has been systematically studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and ultraviolet laser Raman spectroscopy. The SEM observation shows that the novel carbon material exists in various forms such as individual balls, net-like and plate-like forms, all of which have a quite smooth surface. The diameters of these carbon spheres are quite uniform and in a narrow range of 10–20 μm. The EDS analysis reveals that the ball-like carbon material contains more than 99.5% of carbon and a little amount of other elements such as nickel, silicon and aluminum. The XRD and UV–Raman results reveal that the novel carbon material is a kind of highly graphitized carbon. The growth mechanism of the ball-like carbon material was proposed and discussed in terms of arc plasma parameters and the chemical structure of coal-based carbon.