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권대환(Dae-Hwan Kwon),임정규(Jeong-Gyu Lim),정세교(Se-Kyo Chung),이대식(Dae-Sik Lee) 전력전자학회 2006 전력전자학술대회 논문집 Vol.- No.-
A high voltage power supply is developed for driving an image intensifier tube(ⅡT). The ⅡT is used for a night vision devices to observe an object in the dark. The ⅡT power supply needs three high voltage outputs of 5000[V], -900[V], -900[V] for the screen, multichannel plate and photocathode. A push-pull resonant converter topology is used for generating these voltages. The experimental results and provided to verify the operation of the developed power supply.
기계적합금화법을 이용한 고온 고강도 Al-Nb-Zr 합금 제조 및 특성 평가
권대환,안인섭,김상식,이광민,박민우,Kwon, Dae-Hwan,Ahn, In-Shup,Kim, Sang-Shik,Lee, Kwang-Min,Park, Min-Woo 한국재료학회 2000 한국재료학회지 Vol.10 No.7
최근에 고온용 항공기 구조 재료로 Ti, Zr, V, Nb 및 Ta 등의 천이금속을 첨가한 Al 합금계 제조와 특성에 관한 연구가 되어져 왔다. 본 연구에서는 Al-Nb합금에 Zr을 첨가하여 상형성거동을 연구하였다. Al-1.3at.%(Nb+Zr) 합금에서 Nb와 Zr의 원자비를 1:3, 1:1 및 3:1로 하여 기계적합금화하였다. 기계적합금화하는 동안 Al-Nb-Zr의 형태변화와 미세구조를 SEM, XRD 및 TEM으로 관찰하였다. X-선 회절 시험에 의하여 $Nb_2Al$ 과 $Al_3Zr_4$가 생성됨을 확인하였다. $500^{\circ}C$에서 1시간동안의 진공열처리에 의하여 $Al_3Zr$, $Al_3Zr_4$ 등의 금속간화합물을 형성하였다. 30시간동안 기계적 합금화한 분말을 열처리하여 TEM으로 관찰한 결과 100nm 이하의 금속간화합물 입자들을 관찰하였다. Recently there have been many investigations on the synthesis and properties of transition metal trialuminides based on Ti, Zr, V, Nb and Ta for use aircraft structure materials in an elevated environment. The effect of Zr additions on the formation behaviour of Al-Nb alloy was investigated. Al-1.3at.%(Nb+Zr) alloys with different Nb to Zr atomic 1:3, 1:1 and 3:1 were prepared by mechanical alloying(MA). The morphological changes and microstructural evolution of Al-Nb-Zr powders during MA were investigated by SEM, XRD and TEM. The intermetallic compound phase of $Nb_2Al\; and\; Al_3Zr_4$ was identified by X-ray diffraction. The intemetallic compound of $Al_3Zr,\; Al_3Nb$ and $Al_3Zr_4$ were formed by heat treatment for 1 hour at $500^{\circ}C$. The size of intermetallic compounds observed by TEM were approximately below 100nm, when they were heat treated after mechanically alloying for 30 hours.
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.