In-situ-diffraktion av Mo(Si,Al)2 för hållbara industriella uppvärmningstill´mpningar

Purpose and goal:

The project goal, to jointly with Kanthal "verify the applicability and compatibility of in-situ neutron/synchrotron diffraction to develop ceramic elements for industrial heating" has been met. Both neutron and synchrotron X-ray diffraction are applicable for measurements of the thermal expansion of different phases in Mo-silicide-based heating elements. A comparison between the two methods shows that X-ray diffraction is more efficient and more reliable for this type of investigations.

Expected results and effects:

The measurements performed together with Kanthal have provided quantitative information on the expansion of different phases in MoSi2 and Mo(Si,Al)2 during heating. This makes it possible to estimate internal strains in the material due to differences in expansion coefficients between phases. The ansiotropic expansion of the Mo5Si3 phase explains previously observed cracking.

The results point to the importance of reducing the anisotropy in Mo5Si3, and the project shows that in situ synchrotron X-ray diffraction is the most suitable method for further studies. Approach and implementation:

The thermal expansion in different crystal directions was determined for all phases in the material supplied by Kanthal using in situ diffraction experiments during heating to 1300 °C with both neutrons (GEM at ISIS) and synchrotron X-rays (P21.2 at PETRA III). The data were then analyzed by Rietveld refinement with GSAS II. As the synchrotron data contained hundreds of diffractograms per sample, sequential refinement was used.