Applications of Atomic Force Microscopy in Particle Technology
Fritzsche, J., TU Bergakademie Freiberg, Freiberg, Germany; Rudolph, M.,
Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource
Technology, Freiberg, Germany; Peuker, U.A., TU Bergakademie Freiberg, Freiberg,Germany;

Atomic force microscopy (AFM) with its manifold scanning modes and especially withthe colloidal probe mode allow the direct measurement of particle interactions andsurface geometry. Thus, it is the direct way to evaluate the adhesion of particles tosurfaces or to each other. With the direct measurement, it is significantly easier toquantify the effect of changing surface properties on the interaction forces. Several
surface as well material properties influence the interaction forces like surface
roughness, local chemical composition (e.g. adsorbed surfactants), electrostatic
charge, magnetic polarization and surface energies.
Phase contrast AFM
The non-contact as well as the tapping mode imaging of AFM allow characterizing
the composition of a heterogeneous surface like that of a nano-composite material,with a high resolution, which is comparable to TEM [1]. For this method, it is notnecessary to prepare translucent samples, but only to minimize the surface
roughness, e.g. by polishing to avoid a secondary signal. Other approaches apply
phase contract for the detection of the presence of nano-bubbles, which otherwise
can be characterized with topography measurements in the non-contact mode.
Colloidal Probe AFM (dry)The colloidal probe provides the real adhesion effects taking into account both theroughness of the substrate as well as that of the particle [2].
Colloidal Probe AFM (wet - liquid cell)
The colloidal probe measurements in the liquid phase allow quantifying the surface
modification due to adsorption from the aqueous phase to the substrate, or to theparticle at the cantilever itself [3, 4]. With these interaction forces, it becomes
possible to predict the stability of agglomerates and flocks. The adsorption of
surfactants like modifiers or flotation collectors can be quantified [5] as well as aninteraction of the surface with one component of a water-alcohol mixture.

Literature[1] M. Rudolph, K. Bauer, U.A. Peuker, Phasenkontrast-Rasterkraftmikroskopie fürdie Charakterisierung der Verteilung von Nanopartikeln in Verbundwerkstoffen.
Phase-contrast Atomic Force Microscopy for the Characterization of theDistribution of Nanoparticles in Composite Materials, Chemie Ingenieur Technik,
82 (2010) 2189-2195.
[2] O. Laitinen, K. Bauer, J. Niinimäki, U. Peuker, Validity of the Rumpf and theRabinovich adhesion force models for alumina substrates with nanoscaleroughness, Powder Technology, 246 (2013) 545-552.
[3] J. Fritzsche, U.A. Peuker, Particle adhesion on highly rough hydrophobic
surfaces: The dirstibrution of interaction mechanisms, Colloids and Surfaces A:
Physicochemical and Engineering Aspects, 459 (2014) 166-171.
[4] J. Fritzsche, U.A. Peuker, Wetting and adhesive forces on rough surfaces - Anexperimental and theoretical study, in: World Congress on Particle Technology,Beijing, 2014.
[5] M. Rudolph, U.A. Peuker, Mapping hydrophobicity combining AFM and Raman
spectroscopy, Minerals Engineering, 66 (2014) 181-190.