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| Abstract No.: |
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Scheduled at:
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Thursday, June 08, 2017, Hall 26 11:20 AM
Characterization & Testing Methods I
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| Title: |
Porosity measurements on heat treated suspension plasma sprayed YSZ coatings using NMR cryoporometry
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| Authors: |
Johanna Ekberg* / Chalmers University of Technology, Sweden
Uta Klement / Chalmers University of Technology, Sweden
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| Abstract: |
Suspension plasma sprayed coatings are built up by fine powder particles and consist of pores in various size ranges. Characterization and quantification of pores within these coatings, especially the nano-sized pores, requires an analytical method with high accuracy and high resolution. Nuclear magnetic resonance (NMR) cryoporometry is a new promising technique for measuring porosity and pore size distribution in different materials. The technique is able to measure pore sizes between a few nanometer up to hundreds of nanometer of open connected pores. In addition, with NMR cryoporometry it is possible to estimate the shape of the pores.
Here, the technique is applied on topcoats of thermal barrier coatings (TBCs). The topcoats consisted of 8 wt.% yttria stabilized zirconia and were produced by axial suspension plasma spraying. Both, as-sprayed and heat treated coatings were investigated to evaluate how the porosity changes when exposed to the operational temperature of a turbine. The results show that sintering occurs in connection with the heat treatments and that porosity decreases in all investigated samples (especially for small and large pores). The NMR cryoporometry technique and the obtainable results will be discussed in detail. NMR cryoporometry will also be compared to other techniques used for measuring porosity in TBCs, such as image analysis, mercury intrusion porosimetry (MIP), and X-ray microscopy.
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