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기계화학적 고상반응에 의한 YAG 분말의 합성 및 상 형성 거동에 관한 연구
정현기,황길호,임광영,이영훈,강성군,Jung Hyun-Gi,Hwang Gil-Ho,Lim Kwang-Young,Lee Young-Hun,Kang Sung-Goon 한국분말야금학회 2006 한국분말재료학회지 (KPMI) Vol.13 No.4
Yttrium aluminum garnet (YAG) powders were synthesized via mechanochemical solid reaction using $Y_2O_3$ with three types of aluminum compounds. $Y_2O_3$ reacted mechanochemically with all A1 compounds and formed YAM (yttrium aluminum monoclinic), YAG and YAP (yttrium aluminum perovskite) phases depending on the starting materials. The ground samples containing ${\gamma}-A1_2O_3$ showed the best reactivity, whereas the ground sample containing A100H, which had the largest surface area, exhibited pure YAG after calcination at $1200^{\circ}C$. The sample containing Al had the least reactivity, producing YAP along with YAG at $1200^{\circ}C$. The types and grinding characteristics of the starting materials and grinding time are believed to be important factors in the mechanochemical synthesis of YAG.
Cu 미세 배선을 위한 무전해 Ni-B 확산 방지막의 Cu 확산에 따른 상변태 거동
최재웅,황길호,송준혜,강성군,Choi J. W.,Hwang G. H.,Song J. H.,Kang S. G. 한국재료학회 2005 한국재료학회지 Vol.15 No.11
The phase transformation of Ni-B diffusion barrier by Cu diffusion was studied. The Ni-B diffusion barrier, thickness of 10(Inn, was electrolessly deposited on the electroplated Cu interconnect. The specimens were annealed either in Ar atmosphere or in $H_2$ atmosphere from $300^{\circ}C\;to\;800^{\circ}C$ for 30min, respectively. Although the Ni-B coated specimens showed the decomposition of $Ni_3B$ above $400^{\circ}C$ in both Ar atmosphere and $H_2$ atmosphere, Ni-B powders did not show the decomposition of $Ni_3B$. The $Ni_3B$ was decomposed to Ni and B in hi atmospherr: and the metallic Ni formed the solid solution with Cu and the free B was oxidized to $B_2O_3$. However, both the boron hydride and free B were not observed in the diffusion barrier after the annealing in $H_2$ atmos There. These results revealed that the decomposition of $Ni_3B$ by Cu made the Cu diffusion continued toward the Ni-B diffusion barrier.
무전해 도금법으로 제조된 Ni-B 확산 방지막의 Cu 확산 거동
최재웅,황길호,한원규,이완희,강성군,Choi, Jae-Woong,Hwang, Gil-Ho,Han, Won-Kyu,Lee, Wan-Hee,Kang, Sung-Goon 한국재료학회 2005 한국재료학회지 Vol.15 No.9
Thin Ni-B layer, $1{\mu}m$ thick, was electrolessly deposited on Cu electrode fabricated by electro-deposition. The purpose of the layer is to encapsulate Cu electrodes for preventing Cu oxidation and to serve as a diffusion barrier. The layers were annealed at $580^{\circ}C$ with and without pre-annealing at $300^{\circ}C$ for . 30minutes. In the layer with pre-annealing, the amount of Cu diffusion was lower about 5 times than the layer without pre-annealing. The difference in Cu concentration may be attributed to $Ni_3B$ formation prior to Cu diffusion. However, the difference in Cu concentration decreased during the annealing time of 5 h due to the grain growth of Ni.
무전해 Ni-B 도금을 이용한 플라즈마 디스플레이 버스 전극용 확산방지막의 열처리 영향
최재웅,황길호,홍석준,강성군,Choi Jae Woong,Hwang Gil Ho,Hong Seok Jun,Kang Sung Goon 한국재료학회 2004 한국재료학회지 Vol.14 No.8
Thin Ni-B films, 1 ${\mu}m$ thick, were electrolessly deposited on Cu bus electrode fabricated by electro deposition. The purpose of these films is to encapsulate Cu electrodes for preventing Cu oxidation and to serve as a diffusion barrier against copper contamination of dielectric layer in AC-plasma display panel. The layers were heat treated at $580^{\circ}C$(baking temperature of dielectric layer) with and without pre-annealing at $300^{\circ}C$($Ni_{3}B$ formation temperature) for 30 minutes. In the layer with pre-annealing, amount of Cu diffusion was lower about 5 times than that in the layer without pre-annealing. The difference of Cu concentration could be attributed to Cu diffusion before $Ni_{3}B$ formation at grain boundaries. However, the diffusion behavior of the layer with pre-annealing was similar to that of the layer without pre-annealing after $Ni_{3}B$ formation. With increasing annealing time, Cu concentration of both layers increased due to grain growth.
무전해 코발트 코팅된 금속계 SOFC분리판의 제조 및 특성 평가
한원규,주정운,황길호,서현석,신정철,전재호,강성군,Han, Won-Kyu,Ju, Jeong-Woon,Hwang, Gil-Ho,Seo, Hyun-Seok,Shin, Jung-Chul,Jun, Jae-Ho,Kang, Sung-Goon 한국재료학회 2010 한국재료학회지 Vol.20 No.7
For this paper, we investigated the area specific resistance (ASR) of commercially available ferritic stainless steels with different chemical compositions for use as solid oxide fuel cells (SOFC) interconnect. After 430h of oxidation, the STS446M alloy demonstrated excellent oxidation resistance and low ASR, of approximately 40 $m{\Omega}cm^2$, of the thermally grown oxide scale, compared to those of other stainless steels. The reason for the low ASR is that the contact resistance between the Pt paste and the oxide scale is reduced due to the plate-like shape of the $Cr_2O_3$(s). However, the acceptable ASR level is considered to be below 100 $m{\Omega}cm^2$ after 40,000 h of use. To further improve the electrical conductivity of the thermally grown oxide on stainless steels, the Co layer was deposited on the stainless steel by means of an electroless deposition method; it was then thermally oxidized to obtain the $Co_3O_4$ layer, which is a highly conductive layer. With the increase of the Co coating thickness, the ASR value decreased. For Co deposited STS444 with 2 ${\mu}m$hickness, the measured ASR at $800^{\circ}$ after 300 h oxidation is around 10 $m{\Omega}cm^2$, which is lower than that of the STS446M, which alloy has a lower ASR value than that of the non-coated STS. The reason for this improved high temperature conductivity seems to be that the Mn is efficiently diffused into the coating layer, which diffusion formed the highly conductive (Mn,Co)$_3O_4$ spinel phases and the thickness of the $Cr_2O_3$(S), which is the rate controlling layer of the electrical conductivity in the SOFC environment and is very thin
Heterocoagulation 법으로 제조된 이차전지용 MWNT/SnO<sub>2</sub> 나노복합음극재의 전기화학적 특성
한원규,홍석준,황길호,좌용호,오승탁,조진기,강성군,Han, Won-Kyu,Hong, Seok-Jun,Hwang, Gil-Ho,Choa, Yong-Ho,Oh, Sung-Tag,Cho, Jin-Ki,Kang, Sung-Goon 한국재료학회 2008 한국재료학회지 Vol.18 No.9
Through the electrostatic interaction between the poly-diallydimethylammonium chloride (PDDA) modified Multi-walled carbon nanotube (MWNT) and $SnO_2$ suspension in 1mM $NaNo_3$ solution, MWNT-$SnO_2$ nanocomposites (MSC) for anode electrodes of a Li-ion battery were successfully fabricated by colloidal heterocoagulation method. TEM observation showed that most of the $SnO_2$ nanoparticles were uniformly deposited on the outside surface of the MWNT. Galvanostatic charge/discharge cycling tests showed that MSC anodes exhibited higher specific capacities than bare MWNT and better cyclability than unsupported nano-$SnO_2$ anodes. Also, after 20 cycles, the MSC anode fabricated by heterocoagulation method showed more stable cycle properties than the simply mixed MSC anode. These improved electrochemical properties are attributed to the MWNT, which adsorbs the mechanical stress induced from volume change and increasing electrical conductivity of the MSC anode, and suppresses the aggregation between the $SnO_2$ nanoparticles.
기계적 합금화법과 방전 플라즈마 소결법으로 제조된 Al-25Ti-8Mn 금속간 화합물의 산화 거동
최재웅,김기홍,황길호,홍석준,강성군,Choi J. W.,Kim K. H.,Hwang G. H.,Hong S. J.,Kang S. G. 한국재료학회 2005 한국재료학회지 Vol.15 No.7
The oxidation behavior and the thermal stability of nanocrystalline Al-25Ti-8Mn intermetallic compound were investigated. $Al_3Ti$ intermetallic compound, which has a potential for high temperature structural material, was fabricated by mechanical alloying(MA) with $8at.\%$ Mn to enhance the thermal stability and ductility. And Al-25Ti-8Mn intermetallic compound was sintered by spark plasma sintering(SPS) at $700^{\circ}C$. After sintering process, cubic $Ll_2$ structure was maintained without phase transformation and the grain size was about 50nm. To investigate the oxidation behavior of the specimens, thermal gravimetric analysis(TGA) was performed at 700, 800, 900, and $1000^{\circ}C$ for 24 h in $O_2$. As the temperature increased from $700^{\circ}C\;to\;900^{\circ}C$ the weight gain of specimens increased. However at $1000^{\circ}C$, unlike the oxidation behavior of $700^{\circ}C\;to\;900^{\circ}C$, the weight gain of specimen decreased drastically and the transition from linear rate region to parabolic rate region occurred rapidly due to the dense $\alpha-Al_2O_3$.
Inconel 738LC의 Pt Modified-pack Aluminizing 내산화 코팅의 산화저항성에 미치는 Palladium 완충층의 영향
한원규,최재웅,홍석준,황길호,강성군,Han W. K.,Choi J. W.,Hong S. J.,Hwang G. H.,Kang S. G. 한국재료학회 2005 한국재료학회지 Vol.15 No.4
In this study, the effects of Pd buffer layer on the oxidation resistance of Pt modified-pack aluminized Inconel 738LC, used for gas turbine, were investigated. Pd was electroplated on Inconel 738LC, and Pt was electroplated on the electroplated Pd surface. Thus, the thickness of electroplated Pt/Pd was $10\;{\mu}m$ and the atomic ratio of Pt : Pd was about 6 : 4. After Pt/Pd electroplating, Inconel 738LC was pack aluminized to form the oxidation resistant layer. To investigate the oxidation resistance of Pt/Pd modified-pack aluminized Inconel 738LC, iso-thermal oxidation and cyclic oxidation were performed. The iso-thermal oxdation and the cyclic oxidation data indicated that the Pt/Pd modified-pack aluminized Inconel 738LC was more oxidation resistant than the Pt modified-pack aluminized Inconel 738LC. It was thought that the difference of thermal expansion coefficient between Inconel 738LC and Pt was lowered by the Pd buffer layer.