| AVS 55th International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF-TuM |
| Session: | Applications of Atomic Layer Deposition |
| Presenter: | N.A. Isomäki, Beneq Oy, Finland |
| Authors: | K.M. Nevalainen, Tampere University of Technology, Finland R.J. Suihkonen, Tampere University of Technology, Finland N.A. Isomäki, Beneq Oy, Finland C. Hintze, Technical University of Chemnitz, Germany P.S. Eteläaho, Tampere University of Technology, Finland J.E. Vuorinen, Tampere University of Technology, Finland P.K. Järvelä, Tampere University of Technology, Finland |
| Correspondent: | Click to Email |
A recently developed process to form homogenously dispersed nano-sized titanium dioxide (TiO2) particles within a polymer matrix was introduced and compared to traditionally melt-compounded nanofillers. Micron-sized polyamide particles were pre-coated with thin TiO2 films by atomic-layer-deposition (ALD). ALD coating was performed at 40 °C by alternately exposing polyamide powder to titanium tetrachloride and water, separated by nitrogen purge steps. TiO2 coatings on polyamide particles possessed nominal thicknesses of 10 nm or 40 nm. The ALD-coated polyamide particles and the composites manufactured from the two different commercial TiO2 nanofillers were melt-compounded using a 5 cm3 micro-compounder. The dispersion of the crushed TiO2 shells in the polyamide matrix were studied after extrusion using a transmission electron microscopy and the results suggested very different morphology from the traditional TiO2 nanocomposites. The ALD-created TiO2 appeared as ribbons in the polyamide matrix whereas the commercial TiO2 fillers formed spherical clusters. The effect of these TiO2 morphology changes on the mechanical response of the specimens subjected to tensile and impact loading was investigated. The results demonstrated that the nanocomposites based on ALD-coated polyamide particles possess 50-150% higher Young’s modulus than pure and commercially filled polyamide matrix whereas yield strength is only slightly increased for 10 nm ALD-coated composite and in fact somewhat decreased for 40 nm ALD-coated composite. Furthermore, the ductility upon tensile loading is significantly affected. A transition from ductile to brittle deformation occurs for both ALD-coated nanocomposites. Notched impact strength experiments supported this phenomenon showing that the impact strength of ALD-coated composites decreased 50% compared to pure and traditionally filled polyamide matrix whereas the traditional TiO2 nanocomposites showed no significant changes. The fracture surfaces of the nanocomposites examined with scanning electron microscope suggested that the nanoparticle dispersion was good but some impurities in the matrix were found and their origin is discussed. The tribological properties of the selected specimens were also determined using pin-on-disc type apparatuses and the effect of the titanium dioxide fillers on the friction and wear properties of polyamide matrix is examined.