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High‐Temperature Oxidation at 1500° and 1600°C of SiC/Graphite Coated with Sol–Gel‐Derived HfO 2
Author(s) -
Shimada Shiro,
Aketo Takeshi
Publication year - 2005
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2005.00202.x
Subject(s) - graphite , materials science , scanning electron microscope , coating , isothermal process , layer (electronics) , sol gel , silica gel , analytical chemistry (journal) , chemical engineering , composite material , nanotechnology , chemistry , organic chemistry , physics , engineering , thermodynamics
Oxidation of SiC compositionally graded (SCGed) graphite coated with HfO 2 derived from HfCl 4 by a sol–gel process was performed at 1500° and 1600°C in a flowing gas mixture of Ar and O 2 (80/20 kPa). SCGed graphite was produced by reaction of graphite with either molten Si or SiO gas at 1450°C. The sol–gel‐derived HfO 2 precursor was deposited on SCGed graphite by a dip‐coating method. Isothermal and cyclic oxidation of uncoated‐ and HfO 2 ‐coated SCGed graphite was studied by monitoring overall weight change using an electro‐microbalance. Scanning electron microscopy with energy‐dispersive X‐ray analysis was used to observe the surfaces and cross‐sections of the oxidized HfO 2 ‐coated SCGed graphite. The formation of HfSiO 4 was confirmed on the outer layer of the oxidized sample, beneath which a thin silica layer was formed. The improved oxidation resistance of SCGed graphite by coating with HfO 2 is discussed on the basis of the formation of these two layers.