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Chemical stability of carbon-based inorganic materials for in situ x-ray investigations of ammonothermal crystal growth of nitrides

: Schimmel, S.; Künecke, U.; Meisel, M.; Hertweck, B.; Steigerwald, T.G.; Nebel, C.; Alt, N.; Schlücker, E.; Wellmann, P.


Journal of Crystal Growth 456 (2016), S.33-42
ISSN: 0022-0248
Fraunhofer IAF ()
solubility; solvents; x-ray diffraction; Ammonothermal crystal growth; inorganic compounds; nitrides

The chemical stability of diamond, silicon carbide, vitreous carbon, and boron carbide in supercritical ammonia containing different mineralizers was investigated. The materials were found to show good corrosion resistance in the presence of selective or all tested mineralizers.
Diamond was found to be virtually inert in both ammonoacidic and ammonobasic reaction media. Silicon carbide showed good chemical stability in varying ammonothermal reaction media. The chemical stability of vitreous carbon was found to depend on its manufacturing temperature. Corrosion of boron carbide strongly depends on the mineralizer used as well as on applied mechanical stress. Based on their chemical stability and mechanical properties, the applicability of the materials in the respective ammonothermal reaction media as construction materials is evaluated. Additionally, the applicability of the materials as a window material for both high energy in situ x-ray imaging and low energy in situ x-ray diffraction is discussed.