Ultra-High Temperature Oxidation Resistant Nanocrystalline Oxides Stabilized by Carbon Networks
Abstract
The proposed research shall elucidate the nature of hafnium carbide-oxide interlayers, ananomalous phase observed to form upon oxid"ation of hafnium carbide that some believeprovides the greatest known resistance among oxide-based materials to oxygen permeation inthe ultra-high temperature regime. An assessment of the literature indicates that the interlayerphase bears resemblance to silico"n oxycarbides, with the preponderance of available evidencesupporting the presence of nanocrystalline or amorphous hafnia stabilize""d by graphenicnanodomains. If the interlayer phase can be regarded as an analogue to more familiar siliconoxycarbides (i.e., hafni""um ~oxycarbide~), then analogous treatment of its formationthermodynamics predicts that the interlayer phase can only exist under d""istinct ranges ofcarbon and oxygen activities that can be, but have not previously successfully been, reproducedin the laboratory." These thermodynamic quantities will be systematically varied across manyorders of magnitude to selectively oxidize hafnium carbide specimens to form the interlayer~oxycarbide~ phase in bulk quantities while avoiding complete and irreversible oxidation tomonocl"inic hafnia. The structure, thermodynamics, and mass transport properties of theinterlayer phase will be characterized via atom pro""be tomography, small angle x-ray scattering,magic angle spinning nuclear magnetic resonance spectroscopy, micro Raman spectroscopy,""differential scanning calorimetry, oxygen bomb calorimetry, and time of flight secondary ionmass spectrometry, among other support"ing investigations into glass transition andcrystallization behavior. The detailed understanding of the interlayer phase that shall thuslyemerge will provide critical insights into materials discovery and design leading to oxidationresistantcoatings for long-du"ration, multi-use hypersonic and propulsion applications.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712495
Entities
People
- David W. Lipke
Organizations
- Alfred University
- Office of Naval Research
- United States Navy