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Comparative Study of Annealing Effects on the Structural Properties of TiN and TiAlN Coatings
공명호,김현우,양학희 대한금속·재료학회 2008 ELECTRONIC MATERIALS LETTERS Vol.4 No.3
In a comparative study of the influence of thermal annealing processes on TiN and TiAlN coatings prepared by DC magnetron sputtering, we characterized the samples by using x-ray diffraction and scanning electron microscopy. The annealing temperature significantly affected the structural properties of the coatings. The TiO2 phase was generated in the TiAlN coatings by thermal annealing at a higher temperature than in the TiN coatings
Fabrication of SnO2/Zn Core-shell Nanowires and Photoluminescence Properties
공명호,김현우,권용중,조홍연 한국진공학회 2014 Applied Science and Convergence Technology Vol.23 No.5
We have fabricated SnO2/Zn core-shell nanowires by employing a sputtering techniquewith a Zn target. Scanning electron microscopy indicated that the surface of the nanowiresbecame rougher by the coating. X-ray diffraction of the coated nanowires exhibited thehexagonal Zn diffraction peaks. TEM image of coated structures showed that shell layer wasmainly comprised of hexagonal Zn phase. EDX spectra suggested that the shell layer consistedof Zn elements. The photoluminescence spectrum of the coated nanowires in conjunctionwith Gaussian fitting analysis revealed that the emission was disconvoluted with threeGaussian functions, which are centered at 2.1 eV in the yellow region, 2.4 eV in the greenregion, and 3.3 eV in the ultraviolet region. We speculated the possible mechanisms of theseemission peaks.
수열합성법을 이용한 세륨산화물 나노분말의 특성 및 합성에 대한 연구
공명호,나한길,김현우,양학희,Kong, Myung-Ho,Na, Han-Gil,Kim, Hyoun-Woo,Yang, Hack-Hui 한국반도체디스플레이기술학회 2010 반도체디스플레이기술학회지 Vol.9 No.2
We have successfully synthesized $CeO_2$ nanopowders by means of the hydrothermal method, in a low temperature range of $100-200^{\circ}C$. In order to investigate the structure and morphology of the nanopowders, scanning electron microscopy and X-ray diffraction have been employed. In addition, for exploring the optical properties, Raman spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy have been used. In the optimized condition, with the pH, velocity, and time of 4.5, 600 rpm, and 60 h, the $CeO_2$ nanopowders with a diameter ranging from 50 to 150 nm have been synthesized. The nanopowders exhibited the visible emission mainly in the blue region. With comparing the reaction time, it is revealed that the extinction of functional groups at 60 h contributed to the growth and homogenization of the $CeO_2$ powders. Since the overgrowth and agglomeration of nanopowders were found, we suggest that the cracking/growth process is more favorable mechanism than the dissolution/precipitation process.
이억섭,박원구,김병기,황선근,공명호 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.2
Complex tungsten carbides of fine grain sire and Ni as a binding metal were developed with TiC and SiC as additives. The process to produce cemented carbides based on (W-Si-Ti)C-10wt.%Ni consisted of mixing W and TiC powders with liquid glass(SiO₂) and carbon powder and carburizing at 1500∼1550℃ to form SiC coating, adding 10wt.% of Ni powders and sintering. As a result, we obtained a fine grain size in the range of 0.4∼1.0 ㎛, a high micro-Vickers hardness of 1830 ㎏/㎟ and a relative density higher than 97%. TiC appeared to retard grain growth and enhance hardness by forming (W, Ti)C and Ni₃Ti. This was evidenced by the morphological features of (W, Ti)C and WC phases as well as the distribution characteristics of the elements observed by electron microscopy.
Decoration of MgO nanowires with Gd2O3 nanoparticles: structure and photoluminescence properties
강우승,나한길,권용중,조홍연,강성용,박재영,이종무,공명호,김현우 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.4
We decorated coated Gd2O3 nanoparticles on MgO nanowires by means of Gd sputtering and subsequent thermal annealing. The samples were characterized by X-ray diffraction, scanning electron microscope (SEM), and transmission electron microscopy. The surface roughness observed by SEM was revealed to be Gd2O3 nanoparticles in terms of TEM observation. The PL spectra exhibited a 2.9 eV-peak, which originated from the MgO nanowires, and thermal annealing produced green emission at about 2.4 eV, which is directly associated with the Gd2O3 structure. An additional weak peak at 2.0 eV was found to be related to impurities in the Gd2O3 structure.
Fabrication and annealing effects of SnO2/SiOx nanocables sheathed by the sputtering technique
김현우,Seung Hyun Shim,Jong Woo Lee,Hyo Sung Kim,Mesfin Abayneh Kebede,나한길,양주찬,공명호,이종무 한국물리학회 2010 Current Applied Physics Vol.10 No.1
We reported an approach, in which we have produced the nano-sized crystalline tin oxide (SnO2) particles with rutile structure. SnO2 nanowires were coated with a shell layer of SiOx via a sputtering method. Transmission electron microscopy and elemental mapping investigations revealed that the nanostructures consisted of a crystalline SnO2 core surrounded by an amorphous SiOx sheath. The annealing effects on the core-shell nanowires were investigated, revealing that the outer surface became rougher by the thermal annealing. For core-shell nanowires, a room-temperature PL measurement with a Gaussian fitting showed yellow, blue, and violet light emission bands, with the relative intensity of the yellow band showing an increase after thermal annealing. Possible PL emission mechanisms are discussed. This study reveals that the sputtering is effective for preparing the shell layers of nanocables.
Structure, Raman, and photoluminescence properties of SnO2/MgO core-shell nanowires
허훈,No-Hyung Park,Han Gil Na,Dong Sub Kwak,안진호,Heon Ham,심광보,최창환,장준혁,이종무,강인필,공명호,소대섭,Joon Woo Lee,김현우,Kyoung Hun Kim 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.6
We prepared MgO-coated SnO2 nanowires, by means of fabricating SnO2 core nanowires and subsequently evaporating an MgB2powder onto the core nanowires. We investigated changes in the morphological, structural, Raman, and photoluminescence (PL) characteristics resulting from application of the coating process and of a thermal annealing process. The surface of the nanowires became roughened by the MgO coating. While the core nanowires corresponded to the tetragonal rutile SnO2structure, the shell was comprised of the cubic MgO phase. Raman spectra revealed that the core-shell nanowires exhibited a weak line for MgO-associated with surface phonon modes in a TO-LO phonon gap, in addition to the SnO2-related lines. The room-temperature PL spectrum of core SnO2 nanowires exhibited a 2.1 eV-centered broad band and the peak position was invariant not also by the shell coating but also by the subsequent thermal annealing. The PL intensity was increasd by the MgO coating, being attributed to a diffusion effect. The PL reduction by the subsequent thermal annealing is ascribed to oxygen incorporation into the SnO2 core nanowires.