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Si(5 5 12)-2×1 표면에 벤젠과 피리딘의 결합구조
장상훈(S. H. Jang),오승철(S. Oh),한재량(J. R. Hahn),정호진(H. Jeong),정석민(S. Jeong) 한국진공학회(ASCT) 2006 Applied Science and Convergence Technology Vol.15 No.1
Si(5 5 12)-2×1 표면에 벤젠과 피리딘의 흡착구조를 80 K 온도에서 주사 터널링 현미경과 density functional theory 계산 방법으로 연구했다. 벤젠 분자는 기울어진 butterfly 형태로 Si(5 5 12)-2×1의 D2, D3 유닛에 두 개의 adatom과 강하게 결합된다. 흡착 벤젠 분자에 두개의 C=C 이중 결합이 있으며 탄소와 Si adatom 사이에 di-σ 결합이 있다. 피리딘 분자는 Si-N dative 결합 또는 di-σ 형태로 D2와 D3 유닛의 adatom과 결합을 한다. 질소 원자의 홀전자쌍에 의해 결합된 dative 결합은 수직 형태의 구조를 띠며 di-σ 결합보다 더 안정한 것으로 나타났다. Di-σ 결합은 Si-C2와 Si-C5 또는 Si-N1와 Si-C4으로 형성된다. We investigated the adsorption of benzene and pyridine on Si(5 5 12) -(2x1) at 80 K by using variable-low temperature scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The benzene molecule most strongly binds to two adatoms on the D3 and D2 units in a tilted butterfly configuration, which consists of di-σ bonds between C atoms and Si adatoms and two C=C double bonds in the benzene molecule. Pyridine molecules interact with adatom(s) on the D2 and D3 units through both Si-N dative bonding and di-σ bonds. The dative bonding through the lone pair electrons of N atom produces a vertical configuration (pyridine-like), which is more stable than di-σ bonds. Di-σ bonds can be formed either through Si-N1 and Si-C4 or Si-C2 and Si-C5.
김정두(J.D.Kim),노일환(I.H.Noh),성석현(S.H.Sung),김원묵(W.M.Kim),오승철(S.C.Oh),이달호(D.H.Lee),권기문(K.M.Kwan),전영학(Y.H.Jeon),김흥기(H.K.Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Recently, emerging as major tasks are grobal warming prevention, and earth environment conservation and preservation, and the resolution of environmental issues is crucial in the 21st century and needs to jointly be tackled by all nations in cooperation with each other. this research developed dry cols air grinding system, and this ensured cold effects of machine tools and dressing effects against loading phenomenon of grinding wheel, thus extending the tool life of grinding wheel.
급냉응고/분말야금법으로 제조한 Al-Fe-V-Si-Ti-W 합금의 고온크립거동
김인수,김낙준,남수우,위당문,오승철,최상우 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.11
The elevated temperature creep properties and microstructural stability of RS/PM Al-10Fe-1.3V-2Si-1Ti-1W(wt.%) alloy have been investigated. The alloy showed high stress exponent of 12 to 18 and activation energy of 237 to 808 kJ/㏖, which was strongly dependent on the temperature and stress. The unusual creep behavior of the dispersion strengthened alloys cannot be described satisfactorily by current creep laws, Recently, Ro¨sler and Arzt proposed a new model assuming thermally activated dislocation detachment from dispersoids exerting an attractive force. In the present study, experimental evidence was achieved for the presence of attractive interaction between the dislocation and the dispersoids using TEM observations. The creep behavior of the alloy was analyzed using the model proposed by Ro¨sler and Arzt, and the experimental data were consistent with the prediction based on the model. It has been confirmed that the high temperature deformation of the alloy was dominated by the dislocation creep at the temperature range of 400 to 480℃, but the diffusional creep at the interface between powders also contributed to the deformation above 430℃.