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Electrokinetics and deposit nanostructure Plenary lecture RSE SEE 2 Symposium

Pietro Luigi Cavallotti with S.Franz, L.Nobili, A.Vicenzo, F.Zhao. Dep. Chemistry, Materials & Eng. Chemistry “G.Natta” Politecnico Milano Italy. Electrokinetics and deposit nanostructure Plenary lecture RSE SEE 2 Symposium Belgrade June 9 2010. Outline. P NI and SCP

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Electrokinetics and deposit nanostructure Plenary lecture RSE SEE 2 Symposium

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  1. Pietro Luigi Cavallotti with S.Franz, L.Nobili, A.Vicenzo, F.Zhao Dep. Chemistry, Materials & Eng. Chemistry “G.Natta” Politecnico Milano Italy Electrokinetics and deposit nanostructure Plenary lecture RSE SEE 2 Symposium Belgrade June 9 2010

  2. Outline • PNI and SCP • 2. Texture and electrokinetics • 3. Cellular electrodeposition • 4. Electroforming of Ni-Co alloys • PNI and SCP • 2. Texture and electrokinetics • 3. Cellular electrodeposition • 4. Electroforming of Ni-Co alloys

  3. Mg Mgz+ + z e Mc Maqz+ + z e The Born Haber cycle Ideal galvanic cell M / M  H / SHE Cell reaction M + zH+ = Mz+aq + (z/2) H2 ionization neutralization h°ion atomization condensation hydration dehydration h°hydr h°at h°cell

  4. The cell enthalpy change and voltage

  5. ° ° ° ° ° ° ° ° ° ° ° ° The Electrochemical Electronegativity For the Metal: ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° For Hydrogen: ° ° ° ° ° °

  6. ° ° ° ° ° ° ° ° ° ° ° ° The normality-inertia parameter ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° °

  7. Enthalpic contributions to the Born Haber cycle Standard emf in aqueous solutions and Normality-Inertia parameter of some ECD metals

  8. The exchange current density

  9. Metal ion exchange current density and PNI

  10. Hydrogen exchange current density and PNI

  11. Secondary Current Pulse Technique deposition cd secondary pulse cd

  12. Transient Behaviour during SCP iP = iC + iF iC = Cads exp(T) ddt iF = iD exp(T) • (t) = BT ln [ (iP/iD) -(iP/iD-1) exp(-iD t / BT Cads)] • BT transient Tafel slope • Cads adsorption pseudo-capacitance

  13. (t) = BT ln [ (iP/iD) -(iP/iD-1) exp(-iD t / BT Cads)]+ +RT/zF (t/)1/2Sand equation i1/2=zFCb(D/4)1/2 CbD1/2= i 1/2 / 1/2F constant parameter SCP with modification of adsorbed layer

  14. Outline • PNI and SCP • 2.Texture and electrokinetics • 3. Cellular electrodeposition • 4. Electroforming of Ni-Co alloys

  15. Normal Metals

  16. Pb ECD overvoltage on Pb single crystals

  17. Pb21M pH 2 T room 5mA/cm2 1h 20 18 16 14 12 ( m 10 V) h 8 6 4 2 0 -2 0 500 1000 1500 2000 2500 3000 3500 m time ( s) 5k Pb (111) 4k Pb (200) 3k Pb (311) a.u. Pb (331) Pb (220) 2k Pb (420) Sub Pb (400) Pb (222) 1k Pb (422) Sub Sub Sub Sub Sub Sub Sub 0 20 30 40 50 60 70 80 90 100 q a 2 Cuk SCP 10, 15, 25, 35 mA/cm2 Bt14mV/dec Cads30F/cm2

  18. Intermediate elements

  19. Cu ECD on Cu single crystals

  20. CuSO41M, H2SO40.5M T room, 10mA/cm2 SCP 20, 50, 90, 130mA/cm2 Bt95mV/dec Cads20F/cm2 20ms

  21. Inert metals

  22. SCP of Co ECD solutions Co21M H3BO30.5M pH 4 10 mA/cm2 B 162 mV/dec Cads 55mF/cm2 Co21M Sulfamide 5mM pH 6 10 mA/cm2 B 50 mV/dec Cads 122mF/cm2

  23. Electrokinetics and structure of CoECD PO [00.1] PO [11.0] PO [10.0]+[11.0]

  24. Lateral growth PO 00.1 BT<RT/F stable hydrolysed species with surface inhibition maximum nucleation activity, easy epitaxial growth Outgrowth PO 11.0 RT/F<BT<3RT/2F inhibition relatively low and confined to the interface weak nucleation activity and easy growth pH intermediate with hydrolytic products only at surface Clustergrowth PO10.0+11.0 BT=2.5÷3RT/F complexes at the surface with boric acid twinned nuclei from cooperative adsorption Cobalt Growth Modes

  25. Texture of Co electrodeposits Cellular cobalt Twinned cobalt

  26. Outline • PNI and SCP • 2. Texture and electrokinetics • 3. Cellular electrodeposition • 4. Electroforming of Ni-Co alloys

  27. Cellular cobalt electrodeposition Co(NH2SO3)2 1M pH 6.0 cd 10 mA/cm2 22°C BT 50 mV/dec Cads 122 F/cm2

  28. Cellular and dendritic cobalt

  29. Co cellular growth

  30. Morphological instability in electrodeposition stabilization instability • H amplitude of mode • y coordinate normal to the surface • k surface curvature • v molar volume of the deposited metal • surface excess free energy • electrochemical potential of metal ion in solution z metal ion charge • overvoltage D.Barkey Adv. Electrochem. Sci&Eng Vol.7 p.151 2002

  31. Cellular growth interpretation ks solution conductivity  Nernst diffusion layer thickness Fe electrostatic field Fc concentration field Fs surface excess free energy term Wc concentration Wagner number Wa activation Wagner number

  32. Cellular growth interpretation If i << iL : Introducing a surface profile: y = H sinx with  = 2/ the sign of will depend on the sign of : with = 2 2 The values for Co in its solution are: v=7 10-6m3/mole; =0.3J/m2; z=2; F=105C/eq; ks=1-1cm-1 and assuming i=70A/m2we obtain:

  33. Cellular growth interpretation The strong inhibition conditions can decrease the conductivity in the adsorbed layer to very low values ks= 0.01 -1cm-1 and also the surface tension could be less e.g. 0.15 J/m2, in this case: The influence of the current density is to decrease , in agreement with the experimental results

  34. Cellular coatings Surface definition is crucial for further developments, such as dry lubrication, with a solid lubricant deposited or adsorbed between the columns

  35. Wear behaviour of Co cellular coating

  36. Conclusions on cellular electrodeposition • When the growth front is controlled by strong inhibition inhibition, lateral growth can be established giving rise to cellular growth. • Cellular growth occurs in intermediate conditions between normal and dendritic growth. • It was observed for Cobalt, Cobalt-Platinum, Copper, Zinc and Gold. • Immediate application regards dry lubrication and hard magnetic features.

  37. Outline • PNI and SCP • 2. Texture and electrokinetics • 3. Cellular electrodeposition • 4. Electroforming of Ni-Co alloys

  38. Nickel Nickel–Cobalt Electroforming for avionic profiles

  39. NiCo electroforming Co2+ = 5 g/l Co(SO3NH2)2 3.3 or 8.5 10-2M Ni–30Co

  40. Tensile test

  41. Texture of Ni and NiCo deposits

  42. XRD peaks of NiCo deposits Sample elf1 10 mA/cm2 grain size ≈ 19.7 nm microstrain ≈ 1.5×10–4 Sample elf6 15 mA/cm2 grain size ≈ 25.4 nm Microstrain ≈ 3.3×10–4

  43. Williamson Hall approach Sample elf1 10 mA/cm2 d≈19.7 nm ε≈1.5×10–4 Sample elf6 15 mA/cm2 d≈25.4 nm ε≈3.3×10–4

  44. Micrograph of the NiCo surface

  45. Indentation test Vickers 200mN 10s 200mN reload 50% 20 cycles

  46. Tensile test Young modulus 220GPa

  47. Tensile test

  48. Deposit stress analyzer

  49. Hardness and Yield stress

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