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Co 질산염과 TiO(OH)<sub>2</sub> 슬러리를 이용한 초미립 TiC-5%Co 제조 및 WC-Co 분말과의 혼합에 따른 소결체 특성
홍성현,김병기,Hong, Seong-Hyeon,Kim, Byoung-Kee 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.2
Ultrafine TiC-5%Co powders were synthesized by spray drying of aqueous solution of TiO$(OH)_2$ slurry and cobalt nitrate, followed by calcination and carbothermal reaction. The oxide powders with carbon powder was reduced and carburized at $900^{\circ}C{\sim}1250^{\circ}C$ under hydrogen atmosphere. During reduction, CO gas was mainly evolved by reducing reaction of oxides. Ultrafine TiC-5%Co powders were easily formed by carbothermal reaction at $1250^{\circ}C$ due to using ultrafine powders as raw materials. The ultrafine WC-TiC-Co alloy prepared by sintering of mixed powder of ultrafine WC-13%Co powder and ultrafine TiC-5%Co powder has higher sintered density and mechanical properties than WC-TiC-Co alloy prepared by commercial WC, TiC and Co powders.
마그네슘환원에 의한 C/N 조성제어 초미립 TiC<sub>x</sub>N<sub>y</sub> 분말 합성
이동원,김병기,윤중열,유지훈,김용진,Lee, Dong-Won,Kim, Byoung-Kee,Yun, Jung-Yeul,Yu, Ji-Hoon,Kim, Yong-Jin 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2
The ultrafine titanium carbonitride ($TiC_xN_y$) particles below 100 nm in mean size, including various carbon and nitrogen contents (x=0.55~0.9, y=0.1~0.5), were successfully synthesized by new Mg-thermal reduction process. Nanostructured sub-stoichiometric titanium carbide ($TiC_x$) particles were initially produced by the magnesium reduction of gaseous $TiCl_4+x/2C_2Cl_4$ at $890^{\circ}C$ and post heat treatments in vacuum were performed for 2 hrs to remove residual magnesium and magnesium chloride mixed with $TiC_x$. Finally, well C/N-controled $TiC_xN_y$ phases were successfully produced by nitrification heat treatment under normal $N_2$ gas atmosphere at $1150^{\circ}C$ for 2 hrs. The values of purity, mean particle size and oxygen content of produced particles were about 99.3%, 100 nm and 0.2 wt.%, respectively.
정전 분무 공정으로 제조된 Fe-Cr-Al 분말 다공체 금속의 고온 산화 특성에 미치는 기공 크기의 영향
오재성,공영민,김병기,이기안,Oh, Jae-Sung,Kong, Young-Min,Kim, Byoung-Kee,Lee, Kee-Ahn 한국분말야금학회 2014 한국분말재료학회지 (KPMI) Vol.21 No.1
Fe-Cr-Al powder porous metal was manufactured by using new electro-spray process. First, ultra-fine fecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid (0.05~0.5% powders) was dispersed on Polyurethane foam through the electro-spray process. And then degreasing and sintering processes were conduced. In order to examine the effect of cell size ($200{\mu}m$, $450{\mu}m$, $500{\mu}m$) in process, pre-samples were sintered for two hours at temperature of $1450^{\circ}C$, in $H_2$ atmospheres. A 24-hour thermo gravimetric analysis test was conducted at $1000^{\circ}C$ in a 79% $N_2$ + 21% $O_2$ to investigate the high temperature oxidation behavior of powder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased with increasing cell size. In the $200{\mu}m$ porous metal with a thinner strut and larger specific surface area, the depletion of the stabilizing elements such as Al and Cr occurred more quickly during the high-temperature oxidation compared with the 450, $500{\mu}m$ porous metals.
연질 Cu 분말-가스분무 Ni계 벌크 비정질 복합분말의 방전플라즈마 소결에 관한 연구
김진천,김용진,김병기,김지순,Kim, Jin-Chun,Kim, Yong-Jin,Kim, Byoung-Kee,Kim, Ji-Soon 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.5
Ni based($Ni_{57}Zr_{20}Ti_{18}Si_2Sn_3$) bulk metallic glass(BMG) powders were produced by a gas atomization process, and ductile Cu powders were mixed using a spray drying process. The Ni-based amorphous powder and Cu mixed Ni composite powders were compacted by a spark plasma sintering (SPS) processes into cylindrical shape. The relative density varied with the used SPS mold materials such as graphite, hardened steel and WC-Co hard metal. The relative density increased from 87% to 98% when the sintering temperature increased up to $460^{\circ}C$ in the WC-Co hard metal mold.
권대환,홍성현,김병기,Kwon, Dae-Hwan,Hong, Seong-Hyeon,Kim, Byoung-Kee 한국재료학회 2003 한국재료학회지 Vol.13 No.12
Ultrafine TaC powders were synthesised by spray drying using tantalum oxalate solution. The spray dried powders were spherical shape and less than 30 $\mu\textrm{m}$ in size. The powders calcined at 500 and X$700^{\circ}C$ showed amorphous structures and $Ta_2$$O_{5}$ phase was obtained by calcining at $700^{\circ}C$. The particle size and shape remains constant after calcination. The calcined spherical powders were composed of an agglomerate of primary particles under 50 nm in size. The complete formation of TaC could be achieved by heat treatment at $1050^{\circ}C$ for 6 hrs. The observed size of TaC powders by TEM was less than 200 nm.
김송이(Song-Yi Kim),최성환(Sung-Hwan Choi),윤중열(Jung-Yeul Yun),공영민(Young-Min Kong),김병기(Byoung-Kee Kim),이기안(Kee-Ahn Lee) 한국표면공학회 2011 한국표면공학회지 Vol.44 No.1
This study investigated the high temperature oxidation behavior of Fe-22%Cr-5.8%Al alloy and the oxidation kinetics of the alloy were discussed. Bulk samples were prepared by VAM (vacuum arc melting) and hot forging. High temperature oxidation testes were isothermally conducted up to 100 hours in 79%N₂+ 21%O₂ environment at three different temperatures (900℃, 1000℃, 1100℃). The weight gain was measured after oxidation according to oxidation time (2, 4, 6, 8, 10, 15, 20, 25, 30, 60, 80, 100 hours). The weight gain significantly increased with increasing oxidation temperature. As the temperature increased, the oxidized samples showed sequential formation of Al₂O₃, Cr-rich oxide, Fe-rich oxide. The activation energy of high temperature oxidation was obtained as 306.63 KJ/㏖. Al₂O₃ were developed on the surface in the early stage of oxidation, representing protective role of oxidation. However, Fe-based and Cr-based oxides leaded to breakaway of oxide layer, thus resulted in the significant increase of additional oxidation.
김진천,하국현,최철진,김병기,Kim Jin-Chun,Ha Gook-Hyun,Choi Chul-Jin,Kim Byoung-Kee 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.4
1990년도 초반에 개발되어 나노분말의 제조 공정으로 집중적으로 연구되어온 화학기상응축공정은 고강도용 나노분말 소재이외에 기능성 자성재료로의 응용에 주로 이용되어 왔다. 최근에는 이러한 응용이외에 나노분말의 표면을 다양한 이종 소재로 응용하고자하는 나노캡슐(혹은 core/shell)화 제조 공정으로 진보되어 다양한 합금 시스템으로 발전하게 되었다. 특히 최근 Particles 2005, Surface Modification in Particle Technology 학회에서는 나노금속 혹은 세라믹 분말에 PMMA, PE등 polymer의 유기화합물의 코팅하여, DNA나 RNA를 부착하거나 추출해내는 나노캡슐화 공정 연구가 매우 활발하게 진행됨을 보여주고 있으며, 이들 나노 캡슐의 개발은 약물전달계(Drug delivery system), 온열치료용 및 MRI 조영제 등의 바이오재료로의 응용가능성이 크게 기대되어 이에 대한 연구들이 활발하게 진행될 것으로 예상된다.