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RISS 인기검색어
- 검색키워드
- 저자 : M.S. El-Shall (검색결과 3 건)
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O. A. FOUAD,M. S. EL-SHALL 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.5
Copper, nickel and cobalt metals and oxides needle-like shape nanoclusters have been synthesized successfully by chemical reduction in solution without using a surfactant. XRD analyses showed that copper and nickel metals could be synthesized in a short time period by a microwave irradiation (MWI) — assisted step wise reduction of metal ions in basic solution using hydrazine as a reducing agent whereas cobalt was mainly precipitated in the form of either hydroxide or oxide. TEM images showed that the size of needle-like shape nanoclusters varying from about 5 nm to few hundred nanometers length. On the other hand, copper and cobalt showed high catalytic activity toward CO oxidation than that of nickel. The mechanism of catalytic oxidation reactions over unsupported metals and oxides are also discussed.
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STRUCTURAL, OPTICAL AND GAS SENSING PROPERTIES OF ZnO, SnO2 AND ZTO NANOSTRUCTURES
Osama A. Fouad,G. GLASPELL,M. S. EL-SHALL 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2010 NANO Vol.5 No.4
Tetrapods, nanobelts and polyhedron-shape like zinc oxide (ZnO), tin dioxide (SnO2) nanostructures and ZnO/ZnSnO3/Zn2SnO4 (ZTO) composite functional semiconducting nanostructures have been synthesized successfully by the vapor–solid growth process. XRD analyses showed that ZnO with wurtzite, SnO2 with rutile and zinc stannate (ZnSnO3) and/or dizinc stannate (Zn2SnO4) with polyhedral crystal structure were condensed from the vapor phase when Zn and/or Sn metal powders individually or mixed were used as the starting materials. The driving forces for growth of these nanostructures were found to be vapor density, temperature, pressure and place of deposition from the source materials. Typically, the ZnO nanobelts have lengths of several hundred of nanometers and widths of about 10–15 nm. The average particle size of SnO2 are in the range of about 10–20 nm. Uniform hexagonal-shaped crystals of ZnO/ZnSnO3/Zn2SnO4 composite in the range of 50–300 nm as estimated from TEM images are observed. Based on the TEM, optical absorption and emission studies and the CO gas sensing characteristics of the prepared materials showed good crystal quality implying that the ZnO, SnO2 and ZnO/ZnSnO3/Zn2SnO4 nanostructures may suggest possible applications in optoelectronic devices and chemical gas sensors.
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MAGNETISM OF NANOPHASE IRON PARTICLES LASER EVAPORATED IN A CONTROLLED OXYGEN ATMOSPHERE
T. Turkki,B.J. Jönsson,V. Ström,H. Medelius,M.S. El-Shall,K.V. Rao 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
Magnetic nanoparticles of iron and iron oxide have been prepared in a modified upward thermal diffusion cloud chamber using pulsed laser evaporation. SEM/TEM studies of these particles reveal a size distribution with a mean diameter of about 60 Å. FTIR spectrum measurements are used to investigate the difference in oxidation level between nanoparticles prepared at different partial oxygen pressures. The complex magnetic behaviour of these particles was studied using DC- and AC-susceptibility measurements. All samples exhibit superparamagnetism with blocking temperatures ranging from 50 K to above room temperature. The coercivity fields as well as the dependence of the blocking temperature on measuring frequency have been studied. Magnetic anisotropy constants are found to be one order of magnitude higher than is known for the bulk values. The mean particle size estimated from the magnetic data is found to be in perfect agreement with the TEM observations.
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