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김형수,나형용 ( H . S . Kim,H . Y . Ra ) 한국주조공학회 1982 한국주조공학회지 Vol.2 No.3
N/A In this study, the influenced of graphite shape on the boriding of cast iron and boride structure was investigated. Gray cast iron, ferritic and pearlitic ductile cast iron were borided at 750,850,900 and 950 ℃ for 1,3 and 5 hours by powder pack method with the mixture of B₄C_9 Na₂B₄O_7, KBF₄and Shc. The boride layer was consisted of FeB(little), Fe₂B (main) and graphite. Some possibility of the existence of unknown Fe-B-C compound in the boride layer was suggested. And precipitates in the diffusion zone was Fe₃(B,C). The concentration of Si and precipitation of Fe₃(B,C) in the α layer raised the hardness of this Zone. The depth and hardness of boride layer increased with the increase of treating temperature and tim. But high temperature (over 950℃) caused pore at graphite position and long treating time (5hrs) sometimes caused formation of graphite layer beneath the boride layer. So, for the practical application of borided cast iron, treating in short time and at low temperature was recommended. And for ductile cast iron, ferritizing or pearlitizing heat treatment was seemmed to be possible at the same time with boriding. The graphite in the boride layer was deeply concerned with the qualitx and characteristics of the boride layer. And it greatly influenced on the shape of the boride phase, structure of the boride layer. Generally speaking, the existance of graphite restrained the growth of the boride phase. But the boundary between the graphite and the matrix acted as the shortcut of boron diffusion. So, for gray cast iron, the graphite layed length-wise led the formation of boride layer.
Ball-milling Effect on the Sinterability of the $UO_2$ ex-AUC Powder
김형수,박춘호,박철주,최창범,정성훈,석호천,Kim, H.S.,Park, C.H.,Park, C.J.,Choi, C.B.,Jung, S.H.,Suk, H.C. Korean Nuclear Society 1994 Nuclear Engineering and Technology Vol.26 No.2
AUC 공정으로 변환된 $UO_2$ 분말의 ball-milling 효과를 관찰하기 위하여 ball-milling 시간에 따른 소결성을 연구하였다. Ball-milling된 분말은 구형화 형태를 보이며, 그의 입자 크기 분포는 bimodal 양상을 나타냈다. 분말크기 분포가 bimodal인 경우, 그의 packing ratio가 monomodal gaussian 분포에 비해 높다. Ball-milling된 분말의 소결밀도 증가는 packing ratio에 의한 영향이 컸으며, ball-milling 시간이 길어질수록 packing ratio는 증가 하였다. AUC 공정으로 변환된 $UO_2$ 분말은 ball-milling을 함으로써, 그의 소결성이 향상됨을 확인하였다. In order to investigate the ball-milling effect on the property changes of UO$_2$ ex-AUC powder, the sinterability of ball -milled powder was studied in terms of the ball -milling time. Spherical shape was found to be kept for ball-milled UO$_2$ powder and the particle size showed a bimodal distribution, which seems to have a higher packing ratio compared with those having monomodal gaussian distribution. The increase of sintered density of the ball -milled UO$_2$ powder is assumed to be mainly affected by the packing ratio, which increase with longer ball -milling time. It is confirmed that the sinterability of UO$_2$ ex-AUC powder is improved by the ball-milling process.