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서동석,이종국,김환,Seo, Dong-Seok,Lee, Jong-Kook,Kim, Hwan 한국세라믹학회 2000 한국세라믹학회지 Vol.37 No.7
Titanium hydroxide precipitate was obtained by the reaction of 0.5M TiOCl2 and 5M NH4OH solutions, then anatase TiO2 powder with nanotubes was prepared by the digestion of the heat-treated powder in 5M NaOH solution. Nanotube was formed for anatase TiO2 powder digested at 10$0^{\circ}C$ above, and the amount and length of nanotube increased with the digestion temperature. In the case of the powder digested at 15$0^{\circ}C$ for 12h, the formed nanotube was 100~150nm in length, 10~20 nm in diameter, and 2nm in width of the walls on both sides of the nanotube. The powder digested at 15$0^{\circ}C$ for 12h showed the highest specific surface area of 270$m^2$/g.
서동석,이종국,유해근,김환,Seo, Dong-Seok,Lee, Jong-Kook,You, Hae-Geun,Kim, Hwan 한국세라믹학회 2001 한국세라믹학회지 Vol.38 No.4
TiOCl$_2$수용액과 암모니아수의 반응으로부터 얻은 titanium hydroxide 침전물에 대해 각각 NaOH 또한 HCl 처리를 통하여 비교적 낮은 온도에서 결정성이 우수하고, 높은 비표면적을 갖는 결정형 TiO$_2$나노분말을 제조하였다. 저온처리 조건을 변화시킴으로써 TiO$_2$분말의 결정상과 입자 모양을 제어할 수 있었는데, NaOH 처리한 다음 산처리한 분말에는 아나타제와 루틸상이 함께 형성되었으며 구형입자와 긴 스핀들 모양의 입자들로 이루어져 있었고, 비등수 처리 시에는 열처리를 통해 아나타제상의 구형 입자들을 얻을 수 있었다. Titanium hydroxide를 0.1M과 0.5M에 산처리한 분말은 모두 아나타제상을 나타내었는데, 0.1M의 분말은 구형입자로 이루어져 있었고, 0.5M의 경우는 대부분 구형입자들로 이루어져 있었지만 스핀들 모양의 입자들도 소량 관찰되었으며, 2M에 산처리한 분말은 루틸상으로서 모두 스핀들 모양의 입자들로 이루어져 있었고, 제조된 분말의 비표면적은 약 240-250$m^2$/g을 나타내었다.
상용 인산칼슘계 분말로 제조된 생체세라믹스의 표면용해 특성
서동석,김환,이종국,Seo D. S,Kim H,Lee J. K 한국재료학회 2004 한국재료학회지 Vol.14 No.1
In this study, dissolution characteristics of four types of commercial calcium phosphate ceramics were investigated in distilled water with respect to chemical composition and microstructure. For all samples, no significant damage was observed after 3 days of immersion. Following the 7 days of immersion, surface dissolution of the ceramics containing a crystalline phase susceptible to water such as TCP, even pure hydroxyapatite, was initiated at grain boundaries and the dissolution was extended interior to the material along the grain boundaries. In the considerably dissolved area, there was grain separation followed by the formation of 20 $\mu\textrm{m}$ of cavities. In at least one case, the residual pores on the surface appeared to initiate dissolution. In a dissolved area, a crack during the fracture propagates along the grain boundaries resulting in intergranular fracture, while transgranular fracture occurs in a dense area without significant dissolution.
Ca/P 비에 따른 수산화아파타이트 생체재료의 표면용해 특성
서동석,김환,이종국,Seo, Dong-Seok,Kim, Hwan,Lee, Jong-Kook 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.1
Ca/P 비가 각각 1.62, 1.67, 1.72인 수산화아파타이트(Hydroxyapatite, HA) 세라믹스를 제조하고, HA 표면에서 수용액에 의하여 일어나는 용해현상을 고찰하였다. 수용액에서 3일간 침적시킨 경우 입계에서부터 용해가 시작되었으며, 침적시간이 10일로 증가하면서 이러한 입계용해에 의한 HA 세라믹스의 미세구조적 분해 현상은 비화학양론적 조성, 즉 Ca/P 비가 1.62 또는 1.72인 시편에서 두드러지게 나타났다. 주목할만한 것은, 용해가 진행되는 동안 세라믹스의 표면에는 골식세포의 흡수 과정에서 흔히 볼 수 있는 표면 결함(lacunae)과 매우 유사한 모양을 갖는 원형의 빈 공간(cavity)이 형성되었다. Hydroxyapatite (HA) ceramics with the Ca/P ratios of 1.62, 1.67 and 1.72 were prepared and their dissolution behaviors in distilled water at $37^{\circ}C$ were investigated. It appeared that surface dissolution of the ceramics was initiated from grain boundaries after 3 days of immersion in water. Following 10 days of immersion, microstructural disintergration of HA was severs for non-stoichiometric compounds, I.e Ca/P ratios of 1.62 and 1.72. Notably, a micron-sized circular cavity similar to lacunae, which can be generally formed in osteoclastic resorption process, was observed.
서동석(Dong-Seok Seo),윤경민(Kyung-Min Yun),배현웅(Hyun-Ung Bae),임남형(Nam-Hyoung Lim) 한국철도학회 2014 한국철도학회 학술발표대회논문집 Vol.2014 No.10
최근 철도가 고속화되어감에 따라 철도수송의 안전성에 대한 요구뿐만 아니라 더 빠른 속도와 더 무거운 축중에 견딜 수 있는 레일중량화 그리고 장대레일화를 진행해왔다. 궤고강성에 절대적인 영향을 미치는 침목의 연구에 대해서는 별다른 진전을 보이지 못했으나, 근래에 궤도 강성 증대와 궤도틀림 저감을 위한 기존의 일자형 PC침목에 비해 높은 저항특성을 갖는 H형 침목이 개발되어 시험부설된 바 있다. 본 논문에서는 유한요소해석을 통하여 다지형침목 부설 시 도상에 미치는 영향을 기존형식의 침목과 비교하여 분석하였다. The demand for safety of rail transportation is increasing as speed up of railways currently. Also, Increase of rail weight and prolongation of rail length with welding have been carried out to endure high speed and heavy axle load. However, the research on ties that influence the track stiffness dominantly has not been much progress. Recently H type sleeper was developed to increase the track stiffness and reduce the track irregularities which has the high resistance rather than existing mono ties. In this paper, through F.E. analysis, the effect on ballast when applying H type sleeper in the track was compared with existing sleeper(Cross sleeper).
서동석(Dong-Seok Seo),김재영(Jae-Young Kim),정재황(Jae-Hwang Jeong),박학수(Hak-Soo Bark),유욱준(Wook-Joon Yu),고상범(Sang-Beom Go),김정헌(Jeong-Heon Kim),장동혁(Dong-Hyouk Jang),서무엽(Mu-Yeb Seo),조빈행(Bin-Haing Cho),성하정(Ha-Jung 한국농약과학회 2003 농약과학회지 Vol.7 No.4
To investigate the toxicological effects of technical of IAP-3006, we performed subchronic oral toxicity study in Sprague-Dawley (SD) rats. In the subchronic dietary study, rats of both sexes were fed diets containing technical of IAP-3006 at concentrations of 0, 1000, 10,000, or 15,000 ppm for 90 days. No clinical signs and mortality were observed in animals treated with technical of IAP-3006 throughout the experimental period. There were also no significant changes in body weights, feed consumption, and any gross or histopathological lesions. Although there were statistically significant differences between the control and treated groups in some relative and absolute organ weights, and hematological and biochemical analyses, the data were in biologically normal ranges and did not show a dose-dependent manner. From these results, it is suggested that subchronic oral toxicity NOEL of technical of IAP-3006 in rats may be over 15,000 ppm.