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Al 분말의 수화 반응과 스파크 플라즈마 열처리법으로 제조된 알루미나 성형체 연구
엄영랑,이민구,이창규,Uhm Y. R.,Lee M. K.,Rhee C. K. 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.6
The $Al_2O_3$ with various phases were prepared by simple ex-situ hydrolysis and spark plasma sintering (SPS) process of Al powder. The nano bayerite $(\beta-Al(OH)_3)$ phase was derived by hydrolysis of commercial powder of Al with micrometer size, whereas the bohemite (AlO(OH)) phase was obtained by hydrolysis of nano Al powder synthesized by pulsed wire evaporation (PWE) method. Compaction as well as dehydration of both nano bayerite and bohemite was carried out simultaneously by SPS method, which is used to fabricate dense powder compacts with a rapid heating rate of $100^{\circ}C$ per min. under the pressure of 50MPa. After compaction treatment in the temperature ranges from $100^{\circ}C\;to\; 1100^{\circ}C$, the bayerite and bohemite phases change into various alumina phases depending on the compaction temperatures. The bayerite shows phase transition of $Al(OH)_3{\to}{\eta}-Al_2O_3{\to}{\theta}-Al_2O_3{\to}\alpha-Al_2O_3$ sequences. On the other hand, the bohemite experiences the phase transition from AlO(OH) to ${\gamma}-Al_2O_3\;at\;350^{\circ}C.$ It shows AlO(OH) ${\gamma}-Al_2O_3{\to}{\delta}-Al_2O_3{\to}{\alpha}-Al_2O_3$ sequences. The ${\gamma}-Al_2O_3$ compacted at $550^{\circ}C$ shows a high surface area $(138m^2/g)$.
신촉매 나노 구리산화물을 이용한 심혈관 의약품용 Dihydropyrimidine 제조 연구
엄영랑,이민구,이창규,Uhm Y. R.,Lee M. K.,Rhee C. K. 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.6
The copper oxide nano powders were synthesized by levitational gas condensation (LGC) method, and were applied to catalyst to fabricate 3,4-dihydropyrimidin-2-(1H)-one. Processes of adsorption of Biginelli reaction reagents on the copper nanooxide surface $Cu_2O{\circ}CuO$ were studied by IR-spectroscopy. It was shown that benzaldehyde coordination, acetoacetic ether on the oxide surface is carried out with participation of carbonyl fragments, urea by N-H bonds which affects positively on the reagents reactivity.
가수분해법에 의해 제조된 아산화구리 나노분말을 이용한 과산화수소 탈수 연구
엄영랑,김흥회,오정석,이창규,Uhm, Y.-R.,Kim, W.-W.,Oh, J.-S.,Rhee, C.-K. 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.1
$Cu_2O$ nano cubes with high catalase activity were synthesized by reduction of freshly prepared Cu in distilled water at $40^{\circC}$ and their catalase activities of $H_2O_2$ were studied. Transmission electron microscopy (TEM) observation showed that most of these nanocubes were uniform in size, with the average edge length of 30 nm. Selected area electron diffraction of TEM revealed that the nanocube consisted of single crystalline $Cu_2O$, but it changed to CuO phase. The catalase activity depends on the amount of both cuprite phase and surface area.
전기폭발법에 의해 제조된 자성 Fe<sub>2</sub>O<sub>3</sub> 나노 분말의 자기적 특성연구
엄영랑,김흥회,이창규 한국분말야금학회 2002 한국분말재료학회지 (KPMI) Vol.9 No.5
Nanoparticles of $Fe_2O_3$ with a mean particle size of 4-30 nm have been prepared by a pulsed wire evaporation method, and its structural and magnetic properties were studied by SQUID magnetometer and Mossbauer spectroscopy. From the main peak intensity of XRD and absorption rate of Mossbauer spectrum, the amounts of $\gamma-Fe_2O_3$ and $\alpha-Fe_2O_3$ in as-prepared sample are about 70% and 30%, respectively. The coercivity (53 Oe) and the saturation magnetization (14 emu/g) are about 20% of those of the bulk $\gamma-Fe_2O_3$. The low value of coercivity and saturation magnetization indicate that the $\gamma-Fe_2O_3$ phase nearly shows the spin glass-like behavior. Analysis of the set of Mossbauer spectrum indicates a distribution of magnetic hyperfine fields due to the particle size distribution yielding 20 nm of average particle size. The magnetic hyperfine parameters are consistent with values reported of bulk $\gamma-Fe_2O_3$ and $alpha-Fe_2O_3$. A quadrupole line on the center of spectrum represents of superparamagnetic phase of $\gamma-Fe_2O_3$ with a mean particle size of 7 nm or below.
Study of a Betavoltaic Battery Using Electroplated Nickel-63 on Nickel Foil as a Power Source
엄영랑,최병건,김종범,Dong-Hyuk Jeong,Kwang Jae Son 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.3
A betavoltaic battery was prepared using radioactive 63Ni attached to a three-dimensional single trenched P–N absorber. The optimum thickness of a 63Ni layer was determined to be approximately 2 μm, considering the minimum self-shielding effect of beta particles. Electroplating of radioactive 63Ni on a nickel (Ni) foil was carried out at a current density of 20 mA/cm2. The difference of the short-circuit currents (Isc) between the pre- and postdeposition of 63Ni (16.65 MBq) on the P–N junction was 5.03 nA, as obtained from the I–V characteristics. An improved design with a sandwich structure was provided for enhancing performance.
엄영랑,유권모,최상무,김진주,손광재 한국방사선산업학회 2015 방사선산업학회지 Vol.9 No.4
Radioisotope (Nuclear) battery using 63Ni was prepared as beta cell. The electroplated63Ni on Ni foil is fabricated, and beta cell and photovoltaic hybrid battery was designed to use atboth day and night in space project. A Ni-plating solution is prepared by dissolving metal particlesincluding 62Ni and 63Ni from neutron irradiation of (n,γ). Electroplating solution of a chloridebath consists on nickel ions in HCl, H3BO3, and KOH. The deposition was carried out at currentdensity of 10 mA cm-2. The prepared beta source was attached on a PN junction and measuredI-V properties. The power output at activity of 0.07 mCi and 0.45 mCi were 0.55 pW and 2.69 nW,respectively.
Magnetic Properties and Dispersion Stability of Carbon Encapsulated Fe Nano Particles
엄영랑,이히민,김철성,이창규 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61
Carbon-encapsulated Fe nanoparticles were synthesized by using levitational gas condensation (LGC). The morphologies of the carbon-coated Fe nanocrystallites were characterized by using transmission electron microscopy (TEM). All as-made materials were composed of nanocapsules with a uniform particle size at and below 10 nm. The nanocapsules consisted of outer carbon layers of multi-shell. M¨ossbauer spectroscopy revealed that the carbon-coated Fe nanoparticles were made of α-Fe, γ-FeC, and Fe3 C. The magnetization curves were measured at 60 and 300 K. The hysteresis loop demonstrated that the carbon-coated metal nanocrystallites exhibited a superparamagnetic behavior. The dispersion stability of the solvent increased in the following order: water, ethanol, and ethylene glycol. Flocculation due to a coalescing reaction between the nanoparticles was insignificant due to carbon layers on the surfaces of the nanoparticles.
부양가스응축법에 의해 제조된 철산화물 나노 분말의 자기적 특성연구
엄영랑,김흥회,이창규 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.1
Nanoparticles of iron oxides have been prepared by the levitational gas condensation (LGC) method, and their structural and magnetic properties were studied by XRD, TEM and Mossbauer spectroscopy. Fe clusters were evaporated from a surface of the levitated liquid Fe droplet and then condensed into nanoparticles of iron oxide with particle size of 14 to 30 nm in a chamber filled with mixtures of Ar and $O_2$ gases. It was found that the phase transition from both $\gamma$-$Fe_2O_3$ and $\alpha$-Fe to $Fe_3O_4$, which was evaluated from the results of Mossbauer spectra, strongly depended on the $O_2$ flow rate. As a result, $\gamma$-$Fe_2O_3$ was synthesized under the $O_2$ flow rate of 0.1$\leq$$Vo_2$(Vmin)$\leq$0.15, whereas $Fe_3O_4$ was synthesized under the $O_2$, flow rate of 0.15$\leq$$Vo_2$(Vmin)$\leq$0.2.