Synthesis and Characterization of NiMo Catalysts Supported on Fine Carbon Particles for Hydrotreating: Effects of Metal Loadings in Catalyst Formulation

The by-products collected during the synthesis of carbon nanohorns via the arc discharge synthesis method is comprised of other carbon particles (OCP). At a hydrotreating operating temperature of 370°C, preliminary investigations using a bimetallic catalyst with support originating from the fine fractions of other carbon particles (OCPf) and containing 13 wt% Mo and 2.5 wt% Ni resulted in an HDS and HDN conversion of 78 and 25%, respectively. Variation of metal compositions in catalyst formulation and its impact on hydrotreating activity was therefore considered in this study to enhance the hydrotreating activity of OCPf–supported catalyst, and to determine if the best NiMo/OCPf catalyst achieved from this study could be a viable catalyst for hydrotreating applications. The co-incipient wetness impregnation was used in preparing series of hydrotreating catalysts with Ni and Mo loadings within the range of (2.5–5.0 wt%) and (13–26 wt%) respectively. Overall, the catalyst samples with maximum Ni loading of 5.0 wt% and Mo loadings of either 13 or 19 wt% showed higher dispersion and the ability to form a Type II Ni-Mo-S phase with enhanced activity. The effects of metal compositions on both HDS and HDN activities were correlated with their physicochemical properties.

Effects of Ambience on Thermal-Diffusion Type Ga-doping Process for ZnO Nanoparticles

Various annealing atmospheres were employed during our unique thermal-diffusion type Ga-doping process to investigate the surface, structural, optical, and electrical properties of Ga-doped zinc oxide (ZnO) nanoparticle (NP) layers. ZnO NPs were synthesized using an arc-discharge-mediated gas evaporation method, followed by Ga-doping under open-air, N2, O2, wet, and dry air atmospheric conditions at 800 °C to obtain the low resistive spray-coated NP layers. The I–V results revealed that the Ga-doped ZnO NP layer successfully reduced the sheet resistance in the open air (8.0 × 102 Ω/sq) and wet air atmosphere (8.8 × 102 Ω/sq) compared with un-doped ZnO (4.6 × 106 Ω/sq). Humidity plays a key role in the successful improvement of sheet resistance during Ga-doping. X-ray diffraction patterns demonstrated hexagonal wurtzite structures with increased crystallite sizes of 103 nm and 88 nm after doping in open air and wet air atmospheres, respectively. The red-shift of UV intensity indicates successful Ga-doping, and the atmospheric effects were confirmed through the analysis of the defect spectrum. Improved electrical conductivity was also confirmed using the thin-film-transistor-based structure. The current controllability by applying the gate electric-field was also confirmed, indicating the possibility of transistor channel application using the obtained ZnO NP layers.

Synthesis of Carbon Nanotubes via Plasma Arc Discharge Method

CNTs are the element that exists with predominant physio-chemical properties, which have been extensive researched today. These properties make carbon nanotubes (CNTs) valuable in a wide potential range of applications. The production of high-quality carbon nano-tubes (CNTs) via different precursors has been reported for many years. The arc discharge is a pristine technique to form CNTs with a high-quality yield. This technique has been elucidated for a long time, but the growth condition and mechanism of affected synthesized parameters and coorelation between synthesized parameters and nucleation of carbon have not been explored. In this chapter, the authors present the factors affecting temperature, geometry, grain size, electrodes, pressure, catalyst, arc current, power supply, and growth mechanism of CNTs. The variation in parameters has been elicited along with challenges and gaps.

Synthesis of Lithium Phosphorus Oxynitride (LiPON) Thin Films by Li3PO4 Anodic Evaporation in Nitrogen Plasma of a Low-Pressure Arc Discharge

Thin amorphous films of LiPON solid electrolyte were prepared by anodic evaporation of lithium orthophosphate Li3PO4 in an arc discharge with a self-heating hollow cathode at a nitrogen pressure of 1 Pa. Distribution of the arc current between two electrodes having an anode potential provided independent control of the evaporation rate of Li3PO4 and the density of nitrogen plasma. Stabilization of the evaporation rate was achieved using a crucible with multi-aperture cover having floating potential. The existence of a threshold value of discharge current (40 A) has been established, which, upon reaching ionic conductivity over 10−8 S/cm, appears in the films. Probe diagnostics of discharge plasma were carried out. It has been shown that heating the films during deposition by plasma radiation to a temperature of 200 °C is not an impediment to achieving high ionic conductivity of the films. Dense uniform films of LiPON thickness 1 mm with ionic conductivity up to 1 × 10−6 S/cm at a deposition rate of 4 nm/min are obtained.

Study of ion separation mechanism in the multi-component vacuum arc discharge

The separation phenomenon of light and heavy ions was widely observed experimentally in the vacuum arc discharge with multi-component composite cathode. In this work, a two-dimensional axisymmetric multi-fluid model is used to study the separation mechanism in the multi-component composite cathode vacuum arc. The multi-component vacuum arcs are simulated as a whole which includes separate cathode spot jets, the mixing region, and common arc column. The results show that the plasma jets originated from the separate cathode spot mix together to form a common arc column after a certain distance from the cathode. Due to the rapid increase of ion temperature dozens of times in mixing region of cathode spot jet, the effect of pressure gradient becomes far greater than that of the collisions between light and heavy ions. This leads to a shift in the predominant ion motion mechanism from ion-ion collision (single cathode spot jet region) to pressure expansion (the mixing region). Finally, the light ions gain higher velocities under pressure expansion. In addition, the effect of thermal conductivity and viscosity leads to the wider high temperature regions for light ions, thus making a wider distribution of corresponding ion flux. The numerical results are qualitatively consistent with the experimental results. This paper provides an insight into ion separation mechanism in the multi-component vacuum arc.