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A. Cakara, M. Bonta, P.H. Mayrhofer, A. Limbeck:
"Development of a LA-ICP-MS method for the quantitative analysis of Mo, Si and B in oxidation resistant coatings";
Poster: 2015 Euopean Winter Conference on Plasma Spectrochemistry, Münster, Germany; 02-22-2015 - 02-26-2015; in: "Book of Abstracts", (2015), 1 pages.

The application of materials in oxidative, and in particular in high temperature, environments represents a major challenge in terms of oxidation resistance. To extend the lifetime of the materials and to maintain the desired properties, it is necessary to provide oxidation protection by deposition of coatings on the material surface. Boron doped molybdenum silicide alloys show impressive oxidation resistance at high temperatures, as a protective borosilicate layer is formed, which acts as an oxygen diffusion barrier. The oxidation resistance of such Mo-Si-B layers is strongly influenced by the Si to B ratio in the system. Therefore, information about the exact composition of the coatings is required in order to control the production process and to ensure quality in application.
Within this work, a Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) procedure for the analysis of coatings with varying Mo, Si and B content deposited on an alumina substrate by magnetron sputtering has been developed. A set of 12 samples with different coatings was thoroughly characterized using liquid ICP-OES analysis after sample digestion, and subsequently applied for development of the LA-ICP-MS procedure. For none of the investigated elements a linear relationship between the observed LA-ICP-MS signals and the determined Mo, Si and B contents of the samples was obtained. Thus, no reliable bivariate calibration model could be established for signal evaluation. This outcome could be attributed to matrix effects during sample ablation, causing variations in ablation rate, aerosol generation, particle size and transport as well as ion formation in the plasma.
In order to overcome the problem of sample related matrix effects, a multiple linear regression model has been developed for quantification of LA-ICP-MS signals, enabling fast and accurate analysis of unknown Mo-Si-B layers. Cross-validation and external validation confirmed the reliability of the multivariate calibration model.

LA-ICP-MS, elemental analysis, oxidation resistant coatings