The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Surface Bonding: From Molecules to Microparticles

Jukka Katainen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Engineering Physics and Mathematics for public examination and debate in Auditorium K at Helsinki University of Technology (Espoo, Finland) on the 9th of January, 2007, at 13 o'clock.

Overview in PDF format (ISBN 978-951-22-8569-3)   [770 KB]
Dissertation is also available in print (ISBN 978-951-22-8568-6)

Abstract

Surfaces play an active role in many applications ranging from molecular level to macroscopic phenomena. On a molecular level, surface bonds are utilized e.g. in catalysis, sensor applications and coating technology. Bonds in the molecular level are usually formed between single atoms with very limited interaction range originating from the charge transfer between the species. On the macroscopic side, surfaces or interfaces between bulk objects have interaction even when the surfaces are inert in the chemical sense. The attractive interaction is caused by long range electrostatic forces acting on the whole interface. However, the interactions between bulk objects are usually localized in the range of hundreds of nanometers or some micrometers due to the surface roughness present on all practical surfaces. This interaction is exploited e.g. in pharmaceutical industry but it has also disadvantages e.g. in energy production, where ash particles contaminate heat exchanger surfaces.

This work consist of two parts including studies with a well defined surface in ultra high vacuum and studies with practical surfaces in ambient conditions.

Low energy electron diffraction (LEED) has been utilized in determination of the adsorption structures of benzene on Co(0001) surface. The adsorption geometry has been studied using tensor LEED and Density Functional Theory calculations. The studies revealed two adsorption structures in different temperatures. The saturation coverage is 0.143 monolayers and the benzene ring lays flat on an hcp site. The carbon–hydrogen bonds of the benzene ring are slightly bend away from the substrate.

Adhesion of small oxide particles to oxide surfaces has been studied using scanning force microscope. The surface geometry was observed to play very important role in the adhesion. Particularly, the relative lengthscale of the particles and surface features has an important effect. A new model for estimating adhesion on rough surfaces has been developed. By tuning the surface features, the strength of adhesion may significantly be changed. Adhesion in humid conditions has been studied experimentally as well as with numerical simulations. In humid conditions, when the surfaces are hydrophilic, a capillary bridge forms between the particle and the surface increasing the adhesion. The bridge changes the nature of adhesion from van der Waals type to surface tension induced adhesion. The shape and size of the particle and the geometry of the surface all contribute to the adhesion behavior in humid conditions.

This thesis consists of an overview and of the following 5 publications:

  1. K. M. E. Habermehl-Ćwirzeń, J. Katainen, J. Lahtinen, and P. Hautojärvi, An Experimental Study on Adsorption of Benzene on Co(0001), Surface Science 507-510, 57-61 (2002). © 2002 Elsevier Science. By permission.
  2. K. Pussi, M. Lindroos, J. Katainen, K. Habermehl-Ćwirzeń, J. Lahtinen, and A. P. Seitsonen, The (√7̅ × √7̅ )R19.1°-C6H6 Adsorption Structure on Co{0001}: a Combined Tensor LEED and DFT Study, Surface Science 572, 1-10 (2004). © 2004 Elsevier Science. By permission.
  3. J. Katainen, M. Paajanen, E. Ahtola, V. Pore, and J. Lahtinen, Adhesion as an Interplay Between Particle Size and Surface Roughness, Journal of Colloid and Interface Science 304, 524-529 (2006). © 2006 Elsevier Science. By permission.
  4. O. H. Pakarinen, A. S. Foster, M. Paajanen, T. Kalinainen, J. Katainen, I. Makkonen, J. Lahtinen, and R. M. Nieminen, Towards an Accurate Description of the Capillary Force in Nanoparticle-Surface Interactions, Modelling and Simulation in Materials Science and Engineering 13, 1175-1186 (2005). © 2005 Institute of Physics Publishing. By permission.
  5. M. Paajanen, J. Katainen, O. H. Pakarinen, A. S. Foster, and J. Lahtinen, Experimental Humidity Dependency of Small Particle Adhesion on Silica and Titania, Journal of Colloid and Interface Science 304, 518-523 (2006). © 2006 Elsevier Science. By permission.

Keywords: adsorption, benzene, adhesion, pull-off force

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© 2007 Helsinki University of Technology

Last update 2011-05-26