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The Synthesis of Maghemite and Hematite Nanospheres
Dar Mushtaq Ahmad,Ansari Shafeeque G.,Wahab Rizwan,Kim Young-Soon,Shin Hyung-Shik 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Maghemite and hematite nanospheres were synthesized by using the Sol-gel technique. The structural properties of these nanosphere powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and pore size distribution. Hematite phase shows crystalline structures. The mean particle size that resulted from BET and XRD analyses were 4.9 nm and 2 nm. It can be seen from transmission electron microscopy that the size of the particles are very small which is in good agreement with the FESEM and the X-ray diffraction. The BET and pore size method were employed for specific surface area determination.
E-24 : A Study of Diamond Film Growth by Thin Film Coating of Zinc on Si
( Dar Mushtaq Ahmad ),( S. G. Ansari ),조중희,서형기,김길성,김영순,신형식 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
Diamond thin films have been deposited on a variety of substrates using different techniques. Hot Filament Chemical Vapor Deposition has been a most commonly used technique due to its simple instrumentation and effectiveness in producing high quality diamond films. However the substrate temperature has to be maintained at relatively high temperature above ~ 700℃. This has resulted into use of substrates or coatings with melting point higher than substrate temperature held during the diamond film growth. In this communication we show using Atomic Force Microscopy, Scanning Electron Microscopy and Raman Spectroscopy that even low melting point zinc on scratched Si (100) substrate could produce good quality diamond film at substrate temperature ~ 750℃. A liquid substrate can support the growth of diamond film.
Mushtaq Ahmad Dar,Hatem Abuhimd,Iftikhar Ahmad,Mohammad Islam,Mohammad Rezaul Karim,Hyung-Shik Shin 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.7
An initial study on the nucleation and growth of diamond, using hot filament chemical vapor deposition(HFCVD) technique, was carried out on Co and CoO thin buffer layers on non-carbon substrates (Si (100)), and theresults were compared with conventional scratching method. The substrate temperature during the growth was maintainedat 750±50 oC. A mixture of CH4 and H2 (1 : 100 volume %) was used for deposition. The total pressure duringthe two hour deposition was 30±2 Torr. X-ray photoelectron spectroscopy (XPS) study showed the diamond nucleationat different time periods on the Co and CoO seed layers. It is observed that Co helps in nucleation of diamond eventhough it is known to degrade the quality of diamond film on W-C substrate. The reason for improvement in our studyis attributed to (i) the low content of Co (~0.01%) compared to W-C substrate (~5-6%), (ii) formation of CoSi2 phaseat elevated temperature, which might work as nucleation sites for diamond. SEM analysis reveals a change in the morphologyof diamond film grown on cobalt oxide and a significant reduction in the size of densely packed crystallites. Raman spectroscopic analysis further suggests an improvement in the quality of the film grown on CoO buffer layer.
신형식,김영순,강길선,Mushtaq Ahmad Dar,Shafeeque G. Ansari,Hyung-il Kim,Chu Van Chiem 한국화학공학회 2005 Korean Journal of Chemical Engineering Vol.22 No.5
Diamond films on the p-type Si(111) and p- type(100) substrates were prepared by microwave plasma chemical vapor deposition (MWCVD) and hot-filament chemical vapor deposition (HFCVD) by using a mixture of methane CH4 and hydrogen H2 as gas feed. The structure and composition of the films have been investigated by Xray Diffraction, Raman Spectroscopy and Scanning Electron Microscopy methods. A high quality diamond crystalline structure of the obtained films by using HFCVD method was confirmed by clear XRD-pattern. SEM images show that the prepared films are polycrystalline diamond films consisting of diamond single crystallites (111)-orientation perpendicular to the substrate. Diamond films grown on silicon substrates by using HFCVD show good quality diamond and fewer non-diamond components.
Hyung-Shik Shin,Mushtaq Ahmad Dar,김영순,서형기,Gil-Sung Kim,Rizwan Wahab,Zubaida A. Ansari,서재명,신형식 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.3
A comparative study for the nucleation of diamond was carried out using surface treatment like (i) surface scratching with 1 μm diamond paste and (ii) surface etching using chlorine plasma at different RF powers (50, 100 and 150 W). Atomic force microscopic study shows variation in roughness from 31 nm to 110 nm. Scratching results in random scratches, whereas plasma etches a surface uniformly. Scanning electron microscopic observations show well faceted crystallites with a predominance of angular shaped grains corresponding to <100> and <110> crystallite surfaces for the scratched as well as plasma etched substrate. Surface etching at 150W plasma power results in a better growth in comparison with 50 and 100 W plasma powers. Chlorine-radical is found responsible for the changes in the growth morphology. Raman spectroscopy shows a sharp peak at 1,332 cm−1 and a peak at ~1,580 cm−1 for both samples
Superior lithium storage in nitrogen-doped carbon nanofibers with open-channels
Park, Sung-Woo,Kim, Jae-Chan,Dar, Mushtaq Ahmad,Shim, Hyun-Woo,Kim, Dong-Wan Elsevier 2017 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.315 No.-
<P><B>Abstract</B></P> <P>Increasing porosity and nitrogen doping are the most effective strategies for enhancing lithium storage in carbon-based anodes for lithium-ion batteries (LIBs). In this study, we prepare nitrogen-doped carbon nanofibers with open channels (N-CNFO) using a simple electrospinning method with subsequent two-step carbonization using polyacrylonitrile, waste poly(vinyl butyral) (W-PVB), and urea. The W-PVB induce open channels including pores of various sizes, and the urea increase the nitrogen content of the carbon fibers. N-CNFO exhibit excellent electrochemical properties as an anode material for LIBs, including high reversible capacity (734mAhg<SUP>−1</SUP> at 0.2C), superior rate capability (388 and 358mAhg<SUP>−1</SUP> at 3C and 5C, respectively), and excellent cycling performance (330mAhg<SUP>−1</SUP> at 1C after 500 cycles). These properties are imparted to the material owing to the high electrical conductivity of the web structure, the increased number of active sites derived from the open channel structure, and the high nitrogen content, specifically that of N-5 species. This facile synthesis using a waste resource may offer a new direction for the design of superior carbon-based anode materials for high-energy LIBs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nitrogen-doped carbon nanofibers are prepared by an electrospinning process with 2-step carbonization. </LI> <LI> The addition of waste poly(vinyl butyral) induces the open channels on the surface of nanofibers. </LI> <LI> The urea plays a role in the increases of the nitrogen contents of nanofibers. </LI> <LI> The carbon nanofibers exhibit high reversible capacity and long-term cycling stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Taek-Seung,Song, Hee Jo,Dar, Mushtaq Ahmad,Lee, Hack-Jun,Kim, Dong-Wan Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.439 No.-
<P><B>Abstract</B></P> <P>Magnetic metal/carbon nano-materials are attractive for pollutant adsorption and removal. In this study, ultrafine nickel/carbon nanoparticles are successfully prepared via electrical wire explosion processing in ethanol media for the elimination of pollutant organic dyes such as Rhodamine B and methylene blue in aqueous solutions. High specific surface areas originating from both the nano-sized particles and the existence of carbon on the surface of Ni nanoparticles enhance dye adsorption capacity. In addition to this, the excellent dispersity of Ni/C nanoparticles in aqueous dye solutions leads to superior adsorption rates. The adsorption kinetics for the removal of organic dyes by Ni/C nanoparticles agree with a pseudo-second-order model and follow Freundlich adsorption isotherm behavior.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultrafine Ni/C nanoparticles are synthesized by electrical wire explosion process. </LI> <LI> Ni/C nanoparticles exhibit superparamagnetic behavior at room temperature. </LI> <LI> Basic adsorption properties of Ni/C nanoparticles are evaluated. </LI> <LI> Excellent dispersity of Ni/C nanoparticles leads to superior adsorption rates. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>