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2단 Gifford-McMahon 극저온냉동기의 특성실험
박성제,고득용,유창종,김의준,최헌오,Park, S.J.,Koh, D.Y.,Yoo, C.J.,Kim, E.J.,Choi, H.O. 대한설비공학회 1993 설비공학 논문집 Vol.5 No.3
Experimental results of two stage Gifford-McMahon cryorefrigerator are described. In-prototype experiments, drive mechanism is Scotch Yoke type driven by stepping motor, copper meshes and lead balls are used for regenerator's materials in the first stage and the second stage, respectively. To find optimal conditions of the cryopump, no load temperature and refrigeration capacity according to the variation of cycle frequency and operating pressure are measured, and the cool down and load characteristics at particular cycle frequencies are presented. In general, as the cycle frequency is lowered, no load temperature is dropped but refrigeration capacity is diminished. As the representative result, in a case that the cycle frequency is 70rpm and steady state pressure is 14 atm, no load temperature of second stage is lowered to 10.5K in 55 minuters, and in this situation the refrigeration capacity of the first stage is 42W at 80K, that of the second stage is 11 W at 20K.
Diffusion couple 을 이용한 Ni3Al 의 상평형 연구
이찬규,이재현,유창종,조창용,김현철 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.6
Three solid phases are involved in the phase equilibria of the important intermetallic compound Ni₃Al near its melting point, β, γ' (Ni₃Al) and γ. The generally-accepted phase diagram involves a eutectic reaction between γ' and γ, but some recent studies agree with an older diagram due to Schramm, which has a eutectic reaction between the β and γ' phases. This study uses diffusion couple experiments to evaluate the equilibria at temperatures just below the liquidus. The Ni/NiAl diffusion couples were prepared at 1249, 1340, 1355, 1365℃. where the γ' phase formed between β and γ after diffusion heat treatment. The formation of the γ' layer was found to be controlled by volume diffusion. The composition range of the γ' phase with increasing temperatures were increased to the higher Ni composition, which agrees with the Schramm diagram. The interdiffusion coefficient in the γ and β phases has been also determined from the composition profiles of the diffusion couples.