Reaction morphology and the effect of pH on the preparation of TiO2 nanoparticles by a sol-gel method

임창성,류정호,Do-Hwan Kim,조성용,오원춘 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.6

SiC 기판상의 금속박막의 표면구조 및 임계하중

임창성 한국결정성장학회 1995 한국결정성장학회지 Vol.5 No.4

SIC와 금속박막의 반응에 의한 표면구조 및 부착력이 550$^{\circ}C$에서 1450$^{\circ}C$의 온도범위에서 조사되어졌다. SiC/Co계에서는 850$^{\circ}C$ 이상에서, SiC/Ni계에서는 650$^{\circ}C$ 이상에서 여러 가지 규소화물이 형성된 반응이 최초로 나타났다. 코발트는 1050$^{\circ}C$, 0.5 h에서 니켈은 950$^{\circ}C$, 2h에서 SiC와 완전히 반응하여 소모되었다. SiC/Co에서는 CoSi상이 SiC/Ni에서는 Ni$_{2}$Si상이 1250$^{\circ}C$와 1050$^{\circ}C$의 반응에서까지 각각 열역학적으로 안정하게 관찰되어졌다. 탄소는 SiC/Co 반응표면에서는 1450$^{\circ}C$ 이상에서 그리고 SiC/Ni 반응표면에서는 1250$^{\circ}C$ 이상에서의 온도에서 흑연으로 결정화되었다. SiC기판과 금속박막의 임계하중이 scratch test 방법에 의하여 정성적으로 비교되어져, 850$^{\circ}C$에서 1050$^{\circ}C$의 온도범위에서 SiC/Ni couple이 20~33N의 상대적으로 높은 값을 나타내었다. Surface structure and adhesion by the reaction between thin metal films and SiC were studied at temperatures between 550 and $1450^{\circ}C$ for various times. The reaction with the formation of various silicides was initially observed above $850^{\circ}C$ for SiC/Co system and $650^{\circ}C$ for SiC/Ni system. The cobalt reacted with SiC and consumed completely at $1050^{\circ}C$ for 0.5 h and the nickel at $950^{\circ}C$ for 2 h. The observed CoSi phase in SiC/Co and Ni$_2$Si phase in SiC/Ni are thermodynamically stable in the reaction zone up to 125$0^{\circ}C$ and $1050^{\circ}C$ respectively. Carbon was crystallized as graphite above $1450^{\circ}C$ for SiC/Co reaction surface and $1250^{\circ}C$ for SiC/Ni. The critical loads of the thin metal films on SiC substrate were qualitatively compared in terms of the scratch test method. At temperatures between 850 and $1050^{\circ}C$, relatively higher values of 20~33 N were observed for SiC/Ni couples.

Titanium tetra-isopropoxide를 이용한 $TiO_2$ Nanopowder 제초와 pH의 영향

임창성,오원춘,류정호,오근호 한국결정성장학회 2002 한국결정성장학회지 Vol.12 No.2

Titannium tetra-isoporpoxide의 가수분해 반응을 이용하여 nanosize의 $TiO_2$powder를 합성하고, 가수분해 반응에 있어서 촉매로 사용되는 HCI과 $NH_4$OH의 첨가량에 따른 반응양상과 생성된 $TiO_2$분말의 특성의 변화를 조사하였다. 염기성 촉매인 $NH_4$OH,를 사용하였을 경우에 균질한 형상의 powder 형태의 $TiO_2$를 합성할 수 있었으며, 산성 촉매인 HCI을 사 용하여 p보가 5.04 이하일 경우에는 괴상이나 과립의 형태로 생성되었다. 사용한 촉매의 종류와 양에 따라 저온의 결정상인 anatase의 생성속도와 보다 안정한 rutile상으로의 상전이 속도가 영향을 받았다. $TiO_2$ nanopowder was successfully prepared using a titanium tetra-isopropoxide. Subsequently, the effect of pH on the characteristics of the prepared $TiO_2$ nanopowder was evaluated depending on the amounts of the catalysts such as HCI and NH40H. The morphology and phase transformation of $TiO_2$ powder prepared by hydrolysis of titanium tetraisopropoxide were strongly influenced by the presence of the catalysts. In the case of using $NH_4$OH, the morphology of the $TiO_2$ powder exhibited powder form. For the HCI catalyst, it showed bulk or granule form. The phase transformations of amorphous $Ti(OH)_4$ to anatase $TiO_2$ and the anatase to rutile was significantly influenced by the kind and amount of the catalysts.

Czochralski법에 의한 ZnWO₄ 단결정 성장 및 특성분석

임창성,Lim, Chang-Sung 한국분석과학회 2010 분석과학 Vol.23 No.2

Czochralski법에 의한 $ZnWO_4$ 단결정을 [100], [010], [001] 방향으로 성공적으로 성장시켰다. $ZnWO_4$ 단결정 성장을 위한 종자결정은 백금 침을 사용하여 용융액으로부터 모세관 현상을 응용한 결정성장으로 얻을 수 있었다. 각 축 방향에 따른 성장조건이 rotation speed, pulling rate, 성장된 결정의 직경등의 변수를 가지고 조사되어졌다. 성장된 결정의 냉각시 발생되는 균열을 annealing 효과에 의하여 방지할 수 있었다. 성장된 결정의 방위는 Laue back reflection으로 결정하였다. 각 축 방향으로 성장된 결정의 미세구조적 특징이 논하여졌으며, 경도, 열팽창계수 및 유전상수의 물리적 특성이 평가되어졌다. Single crystals of $ZnWO_4$ with [100], [010] and [001] directions were successfully grown by the Czochralski method. The seed crystals for the single crystal growth of $ZnWO_4$ could be induced by the crystal growth using platinum wires applied by the capillary action from the melt. The growth conditions in each direction were investigated in terms of the variations of rotation speed, pulling rate and diameter of the grown crystals. The formation of cracking in the grown crystals during the cooling process could be prevented by annealing effect. The growth directions of the grown crystals were determined using Laue back reflection. The microscopic characteristics of the grown crystals in each direction were discussed, and their physical properties were evaluated for hardness, thermal expansion coefficients and dielectric constants.

Synthesis of NaY(WO4)2:Ho3+/Yb3+ Phosphors via The Microwave-Modified Sol-Gel Route and Their Upconversion Photoluminescence Properties

임창성 한국세라믹학회 2015 한국세라믹학회지 Vol.52 No.1

NaY1-x(WO4)2:Ho3+/Yb3+ phosphors with doping concentrations of Ho3+ and Yb3+ (x = Ho3+ + Yb3+, Ho3+ = 0.05, 0.1, 0.2, and Yb3+ = 0.2, 0.45) were successfully synthesized via the cyclic microwave-modified sol-gel route; their upconversion properties were investigated. Well-crystallized particles showed a fine and homogeneous morphology with particle sizes of 2-5 μm. Under excitation at 980 nm, the synthesized particles exhibited yellow emissions based on a strong 550-nm emission band in the green region and a very strong 655-nm emission band in the red region. The Raman spectra of the doped particles indicated the domination of strong peaks at higher and lower frequencies induced by the incorporation of the Ho3+ and Yb3+ elements into the Y3+ sites in the crystal lattice, which resulted in unit cell shrinkage that accompanied a new phase formation of the WO4-x group.

SiC/Co 반응의 계면화학

임창성,Hubertus Nickel 한국결정성장학회 1995 韓國結晶成長學會誌 Vol.5 No.2

SiC/Co 반응커플을 Ar/4 vol% $H_2$분위기하에서 $950^{\circ}C$에서 $1250^{\circ}C$ 범위에서 4시간에서 100시간까지 열처리하였다. $950^{\circ}C$ 이상의 온도에서의 고상반응으로 여러 가지 규소화물과 탄소석출이 형성되었다. 이 반응 zone에 있어서의 전형적인 반응층의 순서는 $SiC/CoSi + C/Co_2Si + C/Co_2Si/Co_2Si + C/{\cdots\cdots}/Co_2Si/Co$이었다. 그리고 탄소 석출거동을 동반한 주기적인 띠구조의 형성기구가 반응운동학과 열역학적인 고찰을 통하여 조사되어졌고 논하여졌다. 이 반응의 zone의 서장은 시간의 함수관계를 가지며 이러한 반응운동학이 반응상수의 측정을 통하여 제시되어진다. 또한 microhardness 측정을 통하여 반응 zone의 기계적인 물성이 조사되어졌다. Reaction coulples of SiC with cobalt were annealed in an Ar/4 vol% $H_2$ atmosphere at temperatures between $950^{\circ}C$ and $1250^{\circ}C$for various times between 4 and 100 h. At temperatures above $950^{\circ}C$, solid state reactions lead to the formation of various silicides with carbon precipitates. The typical reaction layer sequence was $SiC/CoSi + C/CozSi + C/CozSi/CozSi + C/{\cdot\cdot\}/CO_2Si/CO$ in the reaction zone. The mechanism of the periodic band structure formation with the carbon precipitation behaviour was examined and discussed in terms of reaction kinetics and thermodynamic considerations. The growth of the reaction zone has a square root of time dependence. The reaction kinetics is proposed to estimate the effective reaction constant from the parabolic gowth of the reaction zone. The mechanical properties of the reaction zones were determined by the microhardness test.

Microwave-Modified Sol-Gel Process for Microcystalline KY(WO4)2: Ho3+/Yb3+ Phosphors and their Upconversion Photoluminescence Properties

임창성 한국세라믹학회 2015 한국세라믹학회지 Vol.52 No.6

KY1-x(WO4)2:Ho3+/Yb3+ yellow phosphors with doping concentrations of Ho3+ and Yb3+ (x = Ho3+ + Yb3+, Ho3+ = 0.05, 0.1, 0.2 and Yb3+ = 0.2, 0.45) were successfully prepared using the microwave-modified sol-gel method; their upconversion (UC) photoluminescence properties were investigated in detail. Well-crystallized particles, formed after heat-treatment at 900°C for 16 h, showed a fine and homogeneous morphology with particle sizes of 2-5 μm. Under excitation at 980 nm, the UC KY0.7(WO4)2:Ho0.1Yb0.2 and KY0.5(WO4)2Ho0.05Yb0.45 particles exhibited excellent yellow emissions based on a strong 545-nm emission band in the green region and a very strong 655-nm emission band in the red region. Pump power dependence and Commission Internationale de L'Eclairage chromaticity of the UC emission intensity were evaluated. The spectroscopic properties were examined comparatively using Raman spectroscopy.

Preparation and characterization of Ag incorporated ZnWO4/zeolite composites by cyclic microwave metathetic method

임창성,Jeong Ho Ryu,Jong Geun Choi,Chong Yeon Park,오원춘 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.2

A solid-state metathetic (SSM) route assisted by cyclic microwave irradiation was used to synthesize the Ag incorporated ZnWO4/zeolite composites under environmentally friendly conditions. The crystallized Ag incorporated ZnWO4/zeolite composites were formed at 600 oC for 3 h, showing a well immobilized morphology with sizes of 3-5 μm. The synthesized Ag incorporated ZnWO4/zeolite composites were characterized by scanning electron microscopy, energy-dispersed X-ray spectroscopy and Fourier transform infrared spectroscopy. Monoclinic-like crystals of ZnWO4 were primarily co-mixed with zeolite. Small spherical silver particles were immobilized in the ZnWO4/zeolite matrix.

Upconversion Photoluminescence Properties of PbY2(MoO4 )4:Er3+/Yb3+ Phosphors Synthesized by Microwave Sol–Gel Method

임창성 대한화학회 2016 Bulletin of the Korean Chemical Society Vol.37 No.4

PbY 2− x (MoO4 )4:Er3+/Yb3+ phosphors with the correct doping concentrations of Er3+ and Yb3+ (x = Er3+ + Yb3+, Er3+ = 0.05, 0.1, 0.2, and Yb3+ = 0.2, 0.45) were successfully synthesized using the microwave sol–gel method; their upconversion photoluminescence properties were investigated in detail. Well-crystallized particles, formed after heat-treatment at 900 °C for 16 h, showed a fine and homogeneous morphology with particle sizes of 2–5 µm. Under excitation at 980 nm, the PbY 1.7(MoO4 )4:Er0.1 Yb 0.2 and PbY 1.5(MoO4 )4:Er0.05 Yb 0.45 particles exhibited a strong 525-nm emission band, a weak 550-nm emission band in the green region, and a very weak 655-nm emission band in the red region. The Raman spectra of the doped particles indicated the presence of strong peaks at higher and lower frequencies induced by disordered structures of PbY 2− x (MoO4 )4 by the incorporation of the Er3+ and Yb3+ ions into the crystal lattice, which resulted in the unit cell shrinkage accompanying the new phase formation of the MoO 4−x group.

Interface chemistry and kinetics induced by SiC/Co solid state reactions

임창성 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.1

Interfacial chemistry and kinetics induced by SiC/Co solid state reactions were investigated at temperatures between 850 oC and 1450 oC for various times. The reaction mechanisms and the typical layer sequence in the reaction zone are discussed under the consideration of reaction kinetics and thermodynamics. The formation of silicides and carbon was first observed above 850 oC. At 1050 oC, and as the reaction proceeded, the initially formed Co2Si layer was converted to CoSi. The deposited cobalt thin film reacted completely with SiC after annealing at 1050 oC for 0.5 h. The thermodynamically-stable CoSi was the only observed silicide in the reaction up to 1450 oC. Reaction kinetics are proposed to estimate the effective reaction constant from parabolic growth of the reaction zone. An interfacial model is discussed to interpret the interfacial formation and phase distribution of this system.