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Kinetics and Energetics of Interfacial Mixing in Co-Cu system

KIMM 상변태 열역학 분과 통합 심포지움. Kinetics and Energetics of Interfacial Mixing in Co-Cu system. Seung-Suk Yoo 3 , Sang-Pil Kim 1,2 , Seung-Cheol Lee 1 , Kwang-Ryeol Lee 1 and Yong-Chae Chung 2 1. Future Technology Research Division, KIST 2. Department of Ceramic Engineering, Hanyang University

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Kinetics and Energetics of Interfacial Mixing in Co-Cu system

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  1. KIMM 상변태 열역학 분과 통합 심포지움 Kinetics and Energetics of Interfacial Mixing in Co-Cu system Seung-Suk Yoo3, Sang-Pil Kim1,2, Seung-Cheol Lee1, Kwang-Ryeol Lee1 and Yong-Chae Chung2 1. Future Technology Research Division, KIST 2. Department of Ceramic Engineering, Hanyang University 3. School of Materials Science & Engineering, Seoul National University

  2. Motivation Interfacial Mixing for binary system Miscible system? Immiscible system?  Co-Al, Co-Ti, Ni-Al, Fe-Al …  Co-Cu, Fe-Cu, Fe-Ag, Fe-Au… Surface energy difference or Strain energy difference (lattice mismatch) • Co-Al system : large surface energy difference (Δγ = 60 %) large lattice mismatch (Δa0 = 14 %) • Co-Cu system : Δγ = 28.5 %, Δa0 = 1.8 %

  3. Surface alloy formation for Co-Al * N.R. Shivaparan, Surf. Sci. 476 152 (2001) Co on Al (001)* 4ML Co on Al(001) Low Activation Barrier In spite of room temp. (300K) and very low incident energy of adatom(0.1eV), spontaneous surface alloy was formed.  Local acceleration Co/Al(001)

  4. Intermixing of immiscible system C. Zimmermann et al., PRB 64, 085419 (2001). D.A. Stewart et al., PRB 68, 014433 (2003). After annealing at 750K ~ 1000K  Burrowed Co nanoparticle on Cu(001) surface  Interfacial mixing effects

  5. z[001] x[100] y[010] 300K Initial Temperature 300K Constant Temperature Fix Position Computational Procedure (001) Substrate • 1024 Substrate Atoms, 300K • Step Time : 1.0 fs • Case I : Co/Cu (001) • Case II : Cu/fcc-Co(001) • Incident Energy : 0.1eV, 1.0eV, 3.0eV, 5.0eV XMD 2.5.32 code : MD program  http://www.ims.uconn.edu/centers/simul

  6. EAM Potential for Co-Cu system* * X. W. Zhou et al., Acta. Mater., 49, 4005 (2001).

  7. Results for low incident energy 0.1eV Cu on Co (001) 0.1eV Co on Cu (001) Top View 128 atoms 384 atoms 128 atoms 384 atoms Side View  Mixing Ratio : 0.0 %  Mixing Ratio : 1.56%

  8. Results for 5.0 eV Co on Cu (001) Cu on Co (001) Top View 128 atoms 384 atoms 128 atoms 384 atoms Side View »  Mixing Ratio : 21.1%  Mixing Ratio : 0.78 %

  9. Analysis Related Factors for Mixing Kinetic Factor Calculate activation barrier on an interfacial mixing Energetic Factor Check the system energy evolutions

  10. Local Acceleration Phenomena* Co on Cu(001) Cu on Co(001) 2.63 eV 2.89 eV Local AccelerationContour (001) Surface * S. –P. Kim et al., J. Korean Phys. Soc., 44, 18 (2004).

  11. Atomic Behaviors Mixed mechanism Side view Top view Unmixed mechanism Side view

  12. Kinetic Energy Evolutions  K.E. of each atoms around incident atom Unmixed case Mixed case NOBottom Absorption Bottom Absorption Induced Collision Bump Up Mixing 1 1 4 2 4 2 3 3

  13. Exchange Barrier of Intermixing Exchange Mechanism Cu on Co(001) Co on Cu(001) 0.553 eV 1.21 eV Total Energy Changing : + 0.419 eV  Mixing is very difficult! Total Energy Changing : - 0.476 eV  Mixing can be happened!

  14. Energy Barrier Energy Barrier Energy Reduction Energy Increase Cont. 16 Co Atoms Mixed on Cu(001) 9 Cu Atoms forced Mixing on Co(001) • Energy Barrier for Mixing in Cu/Co(001) is 2.5 times higher than Co/Cu(001) • Effective Induced Collision happened Only in Co/Cu(001) • Kinetically Mixing can be happened in Co/Cu(001) • Kinetically Mixing hardly be happened in Cu/Co(001)

  15. Summary • Through the molecular dynamics approach, quantitative analysis in detail for atomic mixing behaviors were investigated. • In spite of immiscible system, interfacial mixing of Co on Cu(001) can be observed. • Intermixing barrier of Cu on Co(001) is much higher than that of Co on Cu.1.21 eV >> 0.553 eV • In the case of Co on Cu is energetically stable (-0.476 eV), but Cu on Co is unstable. (+0.419 eV)

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