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3차원 혼합기로 볼밀링한 W-Cu 복합분말의 미세구조 변화와 소결거동
김진천 한국분말야금학회 1998 한국분말재료학회지 (KPMI) Vol.5 No.3
The W-Cu composite powders were synthesized from W and Cu elemental powders by ball-milling process, and their microstructural changes and sintering behaviors were evaluated. The ball milling process was carried out in a 3-dimensional mixer (Turbula mixer) using zirconic ($ZrO_2$) ball and alumina ($Al_2O_3$) vial up to 300 hrs. The ball-milled W-Cu powders revealed nearly spherical shape. Microstructure of the composite powders showed onion-like structure which consists of W and Cu shells due to the moving characteristic of Turbula mixer. The W and Cu elements in the composite powders milled for 300 hrs were homogeneously distributed, and W grain size in the ball-milled powder was smaller than 0.5 $\mu\textrm{m}$. Fe impurity introduced during ball milling process was very low as of 0.001 wt%. The relative sintered density of ball-milled W-Cu specimens reached about 94% after sintering at $1100^{\circ}C$.
MIB-II 기반 계층적 네트워크 구조 분석 및 패킷우회 검출 알고리즘
김진천 한국정보통신학회 2003 한국정보통신학회논문지 Vol.7 No.7
네트워크 관리는 메일, 화상회의, 웹, 데이터베이스 등이 작동하는 네트워크 환경에서 더욱 중요한 문제가 되고 있다. 패킷의 적절한 경로를 발견하기 위하여 라우터간에 정보를 교환하는 라우팅 프로토콜이 사용되고 있으나 관리자의 실수로 만들어진 비정상적인 라우팅 테이블로 인하여 데이터를 전송하는 브리지 또는 라우터가 네트워크 디자인의 관점에서 비효율적인 경로로 전송할 수 있다. 이 논문에서는 네트워크상에서 발생할 수 있는 우회 경로를 발견하는 문제를 논의한다. SNMP, MIB로부터의 정보를 사용 계층적 네트워크 구조 분석을 기반으로 우회경로 패스를 발견하는 새로운 알고리즘을 제시하고. 제안된 알고리즘을 검증하기 위해 미리 선언된 데이터를 이용한 시뮬레이션을 수행하였다. Network Management become more and more important issue in the network environment in which many applications such as Mail, teleconferencing, WWW and database software are operated. It can be possible for The Bridge and Router forwarding data to select next hop device which results in routing incorrect path from the viewpoint of network design. In this paper we address the problem of finding the detour routing path due to incorrect setting on routing devices. We propose the new algorithm for finding detour muting path based on hierarchical network structure analysis using information from SNMP MIB. To prove the correctness of the unposed algorithm we have done simulation with predefined data. Simulation results show that the algorithm finds detour path correctly.
기계적 합금방법으로 제조한 극초미세 조직의 W-Cu 복합분말의 금속사출성형 연구
김진천 한국분말야금학회 1998 한국분말재료학회지 (KPMI) Vol.5 No.2
W-Cu alloy is attractive to thermal managing materials in microelectronic devices because of its good thermal properties. The metal injection molding (MIM) of W-Cu systems can satisfy the need for mass production of the complex shaped W-Cu parts in semiconductor devices. In this study, the application of MIM process of the mechanically alloyed (MA) W-Cu composite powders, which had higher sinterability were investigated. The MA W-Cu powders and reduction treated (RT) powders were injected by using of the multicomponent binder system. The multi-stage debinding cycles were adopted in $N_2$ and $H_2$ atmosphere. The isostatic repressing treatment was carried out in order to improve the relative density of brown parts. The brown part of RT W-Cu composite powder sintered at 110$0^{\circ}C$ had shown the higher sinterability compared to that of MA powder. The relative sintered density of all specimens increased to 96% by sintering at 120$0^{\circ}C$ for 1 hour. The relationship between green density and the sintering behavior of MA W-Cu composite powder was analyzed and discussed on the basis of the nanostructured characteristics of the MA W-Cu composite powder.
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.
기상응축법으로 제조한 나노 WC및 WC-Co분말의 후속 열처리에 의한 상 및 협상 변화
김진천,하국현,김병기 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.2
Nanosized WC and WC-Co powders were synthesised by chemical vapor condensation(CVC) process using the pyrolysis of tungsten hexacarbonyl(W(CO)$_6$) and cobalt octacarbonyl(Co$_2$(CO)$_8$). The microstructural changes and phase evolution of the CVC powders during post heat-treatment were studied using the XRD, FE-SEM, TEM, and ICP-MS. CVC powders were consisted of the loosely agglomerated sub-stoichimetric WC$_{1-x}$ and the long-chain Co nanopowders. The sub-stochiometric CVC WC and WC-Co powders were carburized using the mixture gas of CH$_4$-H$_2$ in the temperature range of 730-85$0^{\circ}C$. Carbon content of CVC powder controlled by the gas phase carburization at 85$0^{\circ}C$ was well matched with the theoretical carbon sioichiometry of WC, 6.13 wt%. During the gas phase carburization, the particle size of WC increased from 20 nm to 40 nm and the long chain structure of Co powders disappeared.