Publications by authors named "Helge Kristiansen"

2 Publications

  • Page 1 of 1

Enhancement of Thermal Boundary Conductance of Metal-Polymer System.

Nanomaterials (Basel) 2020 Apr 2;10(4). Epub 2020 Apr 2.

NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway.

In organic electronics, thermal management is a challenge, as most organic materials conduct heat poorly. As these devices become smaller, thermal transport is increasingly limited by organic-inorganic interfaces, for example that between a metal and a polymer. However, the mechanisms of heat transport at these interfaces are not well understood. In this work, we compare three types of metal-polymer interfaces. Polymethyl methacrylate (PMMA) films of different thicknesses (1-15 nm) were spin-coated on silicon substrates and covered with an 80 nm gold film either directly, or over an interface layer of 2 nm of an adhesion promoting metal-either titanium or nickel. We use the frequency-domain thermoreflectance (FDTR) technique to measure the effective thermal conductivity of the polymer film and then extract the metal-polymer thermal boundary conductance (TBC) with a thermal resistance circuit model. We found that the titanium layer increased the TBC by a factor of 2, from 59 × 10 W·m·K to 115 × 10 W·m·K, while the nickel layer increased TBC to 139 × 10 W·m·K. These results shed light on possible strategies to improve heat transport in organic electronic systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/nano10040670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7221886PMC
April 2020

Size-dependent mechanical behavior of nanoscale polymer particles through coarse-grained molecular dynamics simulation.

Nanoscale Res Lett 2013 Dec 21;8(1):541. Epub 2013 Dec 21.

NTNU Nanomechancial Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway.

Anisotropic conductive adhesives (ACAs) are promising materials used for producing ultra-thin liquid-crystal displays. Because the mechanical response of polymer particles can have a significant impact in the performance of ACAs, understanding of this apparent size effect is of fundamental importance in the electronics industry. The objective of this research is to use a coarse-grained molecular dynamics model to verify and gain physical insight into the observed size dependence effect in polymer particles. In agreement with experimental studies, the results of this study clearly indicate that there is a strong size effect in spherical polymer particles with diameters approaching the nanometer length scale. The results of the simulations also clearly indicate that the source for the increases in modulus is the increase in relative surface energy for decreasing particle sizes. Finally, the actual contact conditions at the surface of the polymer nanoparticles are shown to be similar to those predicted using Hertz and perfectly plastic contact theory. As ACA thicknesses are reduced in response to reductions in polymer particle size, it is expected that the overall compressive stiffness of the ACA will increase, thus influencing the manufacturing process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1556-276X-8-541DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3878413PMC
December 2013
-->