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Co / Pd 및 Co / Pt 수직자기기록매체에 있어서 바닥층의 스퍼터링 압력과 M-H 거동의 관계
오훈상(H. S. Oh),이병일(B. I. Lee),주승기(S. K. Joo) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.4
Co/Pd and Co/Pt multilayered thin films for perpendicular magnetic recording media were fabricated by sputtering method and the effects of the sputtering pressure during the formation of Pd or Pt underlayers on the magnetization behavior and coercivity of the multilayers were investigated. It was found that the coercivity of Co/Pd multilayers was strongly dependent on the sputtering pressure of underlayer and could be enhanced to a large extent merely by increasing the sputtering pressure of underlayer, while in case of Co/Pt films, the degree of coercivity enhancement by controlling the sputtering pressure of underlayer was almost negligible. Coercivity variation of Co/Pd and Co/Pt multilayers with the underlayer material and deposition pressure of underlayer could be well explained in terms of the interface roughness of multilayer films induced by underlayer topology, which could also be correlated to the change of perpendicular anisotropy energy and magnetic reversal feature with the sputtering pressure of underlayer. Kerr rotation angle was hardly affected by the preparation conditions of underlayers.
제조조건에 따른 키토산의 이화학적 특성 및 Streptococcus mutans 에 대한 항미생물 효과
김용진(Y. J. Kim),장은정(E. J. Chang),이연형(Y. H. Lee),오훈일(H. I. Oh),조도현(D. H. Jo) 한국키틴키토산학회 2001 한국키틴키토산학회지 Vol.6 No.3
N/A Four kinds of chitosan were prepared by treating crude chitin with various NaOH concentrations. The physicochemical properties and antimicrobial activity of the chitosan against Streptococcus mutans, a primary causative bacterium of dental caries, were investigated. Moisture, crude ash and nitrogen contents of the prepared chitosans were ranged from 5.86-6.72%, 0.46-1.12% and 6.53-7.Iff), respectively. The molecular weights of chitosan-45,-50,-55 and -60 were determined as 59,000,33,000,26,000 and 12,000. respectively. Chitosans prepared with higher concentrations of NaOH solution showed a lower molecular weight. The degree of deacetylation of chitin and various chitosans determined by IR spectrum were 45% and 75-87%, respectively. Chitin had higher water holding and fat binding capacities than the chitosans. However, there were no significant differences among the four chitosans. In dye binding, chitin had a dye binding capacity of 9.32±1.6 mg/g sample, but chitosans except chitosan-45, almost did not bind the dye. It was asssumed that NH2 functional group in the chitosans was removed along with the acetyl group due to the strong deacetylation conditions. The addition of chitosan caused an initial rapid decrease in the population of S. mutans, which was followed by a delayed recovery. The viable cell counts of .S. mutans incubated with 40 ppm chitosan-50(M.W.33,000) were reduced dramatically and S. mutans was not detected after 8h. These results indicate that chitosan can be used for oral care products as anticaries agents.