On the Adhesion between Fine Particles and Nanocontacts

For adhesion forces measured between identical
contacts, two kinds of variations were observed: a
fast, random noise and slower fluctuations. Random
noise is due to thermal vibrations and noise in the
detection system. No intrinsic statistical process is
required to explain it. The slower fluctuations are
probably caused by plastic deformation and structural
changes in the material at the nanocontact. On
homogeneous, smooth surfaces, the distribution of
adhesion forces measured with nanocontacts can be as
narrow as 1.1%. Adhesion force versus humidity curves
measured between hydrophilic surfaces can be
interpreted by assuming capillary condensation of
water into the contact region, which causes a
meniscus force. All types of dependencies observed
can be explained by appropriate and realistic tip
shapes. As a possible simple model, we introduce the
two-sphere model with surface roughness. The often
observed changes in these dependencies when repeating
experiments are interpreted as changes in tip
geometry in the 1-10 nm length scale caused by tip wear.

Autorentext
Mahdi Farshchi Tabrizi studied physics at Bu-Ali Sina and Razi Universities,IR,Iran. After receiving his PhD in 2007 at the Siegen University and Max-Planck-Institute (MPIP), he went as a postdoct to MPIP, Mainz, Germany. From 2001-8 he using AFM to measured surface forces. He is asistant professor and researche at University in Iran and MPIP.

Klappentext
For adhesion forces measured between identical contacts, two kinds of variations were observed: a fast, random noise and slower fluctuations. Random noise is due to thermal vibrations and noise in the detection system. No intrinsic statistical process is required to explain it. The slower fluctuations are probably caused by plastic deformation and structural changes in the material at the nanocontact. On homogeneous, smooth surfaces, the distribution of adhesion forces measured with nanocontacts can be as narrow as 1.1%. Adhesion force versus humidity curves measured between hydrophilic surfaces can be interpreted by assuming capillary condensation of water into the contact region, which causes a meniscus force. All types of dependencies observed can be explained by appropriate and realistic tip shapes. As a possible simple model, we introduce the two-sphere model with surface roughness. The often observed changes in these dependencies when repeating experiments are interpreted as changes in tip geometry in the 1-10 nm length scale caused by tip wear.