STM Observation of Grain Ripening during Air Exposure of the Passive Film Formed on Iron

Stable scanning tunneling microscopy (STM) images during the early stages of air exposure of the passive film on iron were successfully captured by a humidity-controlled method. The passive film formed at -0.4 V SCE in pH8.4 borate buffer solution was first kept in humid air (47% relative humidity) at 15"C for 24 h and then exposed to dry air (<30% RH) at room temperature. Upon exposure to the dry air, the surface structure underwent a distinctly three-stage transformation, concluding with a grain ripening process that has not previously been observed in passive films.

[1]  H. Nanjo,et al.  Reconstruction in Air of an Iron Passive Film Formed at −0.4 V in a Borate Buffer Solution , 2004 .

[2]  P. Gorostiza,et al.  Direct Evidence of the Electronic Conduction of the Passive Film on Iron by EC-STM , 2003 .

[3]  H. Nanjo,et al.  Temperature Dependence of Surface Crystal Structures of Iron Passivated at −400 mV in a Borate Buffer Solution , 2003 .

[4]  D. Mcphail,et al.  An STM Study of the Nanocrystalline Structure of the Passive Film on Iron , 2002 .

[5]  P. Gorostiza,et al.  First Stages of Electrochemical Growth of the Passive Film on Iron , 2001 .

[6]  M. Toney,et al.  The Structure of the Passive Film That Forms on Iron in Aqueous Environments , 2000 .

[7]  D. Meier,et al.  An AFM study of the properties of passive films on iron surfaces , 1998 .

[8]  M. Toney,et al.  Atomic Structure of the Passive Oxide Film Formed on Iron , 1997 .

[9]  G. Thompson,et al.  An STM Study of the Passive Film Formed on Iron in Borate Buffer Solution , 1995 .

[10]  M. Salmeron,et al.  Imaging the Condensation and Evaporation of Molecularly Thin Films of Water with Nanometer Resolution , 1995, Science.

[11]  J. Bockris,et al.  In Situ Scanning Tunneling Microscopy Studies on Passivation of Polycrystalline Iron in Borate Buffer , 1991 .

[12]  J. Bardwell,et al.  Nature of the passive film on Fe–Cr alloys as studied by 18O secondary ion mass spectrometry: reduction of the prior film and stability to ex situ surface analysis , 1991 .

[13]  J. Bardwell,et al.  Composition and growth of anodic oxide films on iron , 1990 .

[14]  R. W. Hoffman,et al.  A Mössbauer Spectroscopy Study of the Potential Dependence of Passivated Iron Films , 1989 .

[15]  M. Graham,et al.  Stability and Growth of Passive Films on Pure Iron in Borate Buffer as Investigated by 18O/SIMS , 1987 .

[16]  W. O'grady.  Mössbauer Study of the Passive Oxide Film on Iron , 1980 .

[17]  J. E. Burke,et al.  RECRYSTALLIZATION AND GRAIN GROWTH , 1952 .