MOCVD OF ALUMINOSILICATE CORROSION PROTECTIVE COATINGS

摘要

The use of silicon carbide fibers and composites in high temperature structural materials requires development of corrosion resistant coatings such as mullite 3Al_2O_3x2SiO_2. Single-source molecular precursors [Al(OSiMe_3)_3]_2 and [(acac)Al(OSiMe_3)_2]_2 as well as compatible precursors Al(acac)3 and [(acac)Al(OSiMe_3)_2]_2 were used to develop a process for low pressure metal-organic chemical vapor deposition (MOCVD) of aluminosilicate protective coatings. Smooth, amorphous, and transparent aluminosilicate coatings with average Al:Si ratios of 0.3-0.5 were deposited on SiC from single-source precursors at 550-650℃. Dark brown aluminosilicate coatings, comprised of small amorphous particles, were deposited from a mixture of the compatible precursors at 3:1 (Al:Si) ratio. Coating compositions were very sensitive to deposition temperature and varied from ～10:1 (550℃) to ～1.1:1 at 650℃. It was found that the CO_2 concentration also effects coating composition.