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Upgrading of vacuum residue in batch type reactor using Ni-Mo supported on goethite catalyst
Sahu, R.,Song, B.J.,Jeon, Y.P.,Lee, C.W. Korean Society of Industrial and Engineering Chemi 2016 Journal of industrial and engineering chemistry Vol.35 No.-
<P>It is imperative to develop an efficient catalyst to convert vacuum residue (VR) into low boiling point liquid products via an environmentally benign pathway. Ni-Mo bimetal was impregnated on goethite supports and well characterized using various analytical techniques. VR hydrocracking catalytic activities were investigated in a batch reactor. The 1%Ni-4.5%Mo/Goethite catalyst showed a high yield of low boiling point liquid products, 69.8%, with 80% VR conversion at 420 degrees C in the presence of 70 bar initial hydrogen pressure in 3 h. In these liquid products, 8.6% of naphtha, 51.4% of middle distillate, 9.8% of vacuum gas oil (VGO) with 28.1% of saturates, 62.5% of aromatics, 8.4% of resins and >1% of asphaltenes were confirmed by TGA and SARA analysis, respectively. The experimental findings indicated that the formation of low boiling point liquid products depends on physical parameters and chemical composition of the catalyst. This paper describes the synthesis of the supported catalysts, influences of the active metal composition, metal/support interaction, and process parameters for hydrocracking of VR into high value, low boiling point liquid products. (C) 2015 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.</P>
Wen, Long,Kumar, Manish,Sahu, B.B.,Jin, S.B.,Sawangrat, C.,Leksakul, K.,Han, J.G. Elsevier 2015 Surface & coatings technology Vol.284 No.-
<P><B>Abstract</B></P> <P>Al doped ZnO films are prepared in dual-confined plasmas (rectangular side-ways and one top-side) in DC magnetron sputtering system without intentional substrate-heating. Present confinement shows improved transparent-conductive properties in Al doped ZnO thin films, when compared to those of deposited by conventional and facing-target confinement. As a function of working pressure and power density, plasma diagnostics is carried out at substrate location using optical emission spectroscopy, thermal energy transfer and net current density measurements. The optical, and electrical properties of the synthesis AZO films were studied and correlated to plasma conditions. It is found that high electron temperature, higher plasma density and highly ionization of oxygen play a key role in enhancing the deposition rate and transmittance ~90% along with minimizing resistivity in the order of 10<SUP>−4</SUP> Ωcm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Developed advanced DC magnetron sputtering system to deposit highly conductive and transparent Al doped ZnO thin films. </LI> <LI> Presented plasma diagnostics using OES, net current density and thermal energy transfer at substrate location. </LI> <LI> Presented the effects of partial pressure and power density on transparent-conductive performances. </LI> <LI> Shown the advantage of present process over conventional DC magnetron sputtering systems. </LI> </UL> </P>
Sahu, B.B.,Kim, Seok H.,Lee, J.S.,Han, Jeon G. Elsevier 2019 Vacuum Vol.160 No.-
<P><B>Abstract</B></P> <P>Conventional and multiple-hole hollow cathode (MHHC) showerhead electrodes of an RF capacitively coupled plasma (CCP) source were experimentally studied to investigate their capability of plasma generation and suitability of plasma application like PECVD. The plasma characteristics of the CCPs were critically examined for the PECVD plasmas produced by various showerhead configurations. The optimum performance in terms of high-density plasma generation and high emission intensity of excited species was observed for the operation using MHHC discharge. The MHHC discharge is characterized by an anode glow and a strong low-frequency fluctuation in the range of ∼ a few kHz that is measured by the Langmuir probe (LP). The LP measurements in a broad pressure range revealed the scenario of hollow cathode discharge characterized by the enhanced electron temperature and the highest plasma density around 120 mTorr. It is realized that the bulk plasma intrusion inside the hole of the electrodes of the showerhead and the enhanced ionization in the plasma sheath regions of each hole facilitated the generation of high-density plasmas when the hole diameter is slightly bigger than twice or thrice the sheath length. The effectiveness of MHHC PECVD for high rate and low-temperature deposition of a-SiN<SUB>x</SUB>:H thin films is realized.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CCPs with different showerhead electrodes were designed and studied for the plasma and radical generation. </LI> <LI> Multiple-hole hollow cathode (MHHC) electrode has shown the best performance for high density plasma production. </LI> <LI> MHHC plasma is characterized by a strong low-frequency floating potential fluctuation f in the range of ~ a few kHz. </LI> <LI> The efficacy of MHHC PECVD for high rate deposition of a-SiN<SUB>x</SUB>:H thin films on flexible substrate is verified. </LI> </UL> </P>
ECCD Performance Analysis of Future KSTAR ECH Systems for Extended Applications
B. B. Sahu,Y. S. Bae,J. H. Jeong,M. Joung,J. G. Kwak,W. S. Han,I. Rhee 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.8
The ability of the KSTAR 170 GHz electron cyclotron (EC) wave launcher to drive a localizedcurrent is analyzed by means of the TORAY-GA ray-tracing code looking at extended physicsapplication of the EC current drive (CD) in the KSTAR. Computation reveals that the EC-drivenCD performance (JCD), as compared to the plasma’s boot-strap current (JBS), i.e., the ratioJCD/JBS, for the normalized minor radius, > 0.5, is not good for the current design of the 1-MW170-GHz launcher. Calculations at a lower frequency of 105 GHz have shown improved values for theJCD. Depending upon the launcher port’s availability, computations are carried out to find the pivotposition for future proposed launchers by optimizing the figures of merit at respective locations. These computations show that Z = +30 cm gives the maximum figure of merit. Computations alsoshow a possible synergy between the two launchers, one pivoted at Z = +30 cm and the other at Z= −25.2 cm. The main aim of this study is to provide guidance for the design of both launchers inorder to optimize their performance according to the physics application.
Sahu, B B,Shin, Kyung S,Han, Jeon G IOP 2016 PLASMA SOURCES SCIENCE AND TECHNOLOGY Vol.25 No.1
<P>This study investigates low-temperature plasma nitriding of hydrogenated silicon (SiN<SUB> <I>x</I> </SUB>:H) film in radio frequency (RF) and RF–ultra-high frequency (UHF) hybrid plasmas. To study the optimized conditions for the deposition of SiN<SUB> <I>x</I> </SUB>:H film, this work adopts a systematic plasma diagnostic approach in the nitrogen–silane and nitrogen–silane–ammonia plasmas. This work also evaluates the capability of plasma and radical formation by utilizing different plasma sources in the PECVD process. For the plasma diagnostics, we have purposefully used the combination of optical emission spectroscopy (OES), intensified CCD (ICCD) camera, vacuum ultraviolet absorption spectroscopy (VUVAS), and RF compensated Langmuir probe (LP). Data reveal that there is significant enhancement in the atomic nitrogen radicals, plasma densities, and film properties using the hybrid plasmas. Measurements show that addition of a small amount of NH<SUB>3</SUB> can significantly reduce the electron temperature, plasma, and radical density. Also, optical and chemical properties of the deposited films are investigated on the basis of plasma diagnostics. Good quality SiN<SUB> <I>x</I> </SUB>:H films, with atomic nitrogen to hydrogen ratio of 4:1, are fabricated. The plasma chemistry of the hybrid plasmas is also discussed for its utility for plasma applications.</P>
Sahu, B B,Yin, Y,Lee, J S,Han, Jeon G,Shiratani, M IOP 2016 Journal of Physics. D, Applied Physics Vol.49 No.39
<P>Although studies of silicon (Si) quantum dots (QDs) were started just a few years ago, progress is noteworthy concerning unique film properties and their potential application for devices. In particular, relating to the Si QD process optimization, it is essential to control the deposition environment by studying the role of plasma parameters and atomic and molecular species in the process plasmas. In this work, we report on advanced material processes for the low-temperature deposition of Si QDs by utilizing radio frequency and ultrahigh frequency dual frequency (DF) plasma enhanced chemical vapor deposition (PECVD) method. DF PECVD can generate a very high plasma density in the range ~9 × 10<SUP>10</SUP> cm<SUP>−3</SUP> to 3.2 × 10<SUP>11</SUP> cm<SUP>−3</SUP> at a very low electron temperature (<I>T</I> <SUB>e</SUB>) ~ 1.5 to 2.4 eV. The PECVD processes, using a reactive mixture of H<SUB>2</SUB>/SiH<SUB>4</SUB>/NH<SUB>3</SUB> gases, are carefully studied to investigate the operating regime and to optimize the deposition parameters by utilizing different plasma diagnostic tools. The analysis reveals that a higher ion flux at a higher plasma density on the substrate is conducive to enhancing the overall crystallinity of the deposited film. Along with high-density plasmas, a high concentration of atomic H and N is simultaneously essential for the high growth rate deposition of Si QDs. Numerous plasma diagnostics methods and film analysis tools are used to correlate the effect of plasma- and atomic-radical parameters on the structural and chemical properties of the deposited Si QD films prepared in the reactive mixtures of H<SUB>2</SUB>/SiH<SUB>4</SUB>/NH<SUB>3</SUB> at various pressures.</P>