NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Collections About News Help Login
Back to Results
Tensile Strength and Microstructural Characterization of Uncoated and Coated HPZ Ceramic FibersTensile strengths of as-received HPZ fiber and those surface coated with BN, BN/SiC, and BN/Si3N4 have been determined at room temperature using a two-parameter Weibull distribution. Nominally approx. 0.4 micron BN and 0.2 micron SiC or Si3N4 coatings were deposited on the fibers by chemical vapor deposition using a continuous reactor. The average tensile strength of uncoated HPZ fiber was 2.0 +/- 0.56 GPa (290 +/- 81 ksi) with a Weibull modulus of 4.1. For the BN coated fibers, the average strength and the Weibull modulus increased to 2.39 +/- 0.44 GPa (346 +/- 64 ksi) and 6.5, respectively. The HPZ/BN/SiC fibers showed an average strength of 2.0 +/- 0.32 GPa (290 +/- 47 ksi) and Weibull modulus of 7.3. Average strength of the fibers having a dual BN/Si3N4 surface coating degraded to 1.15 +/- 0.26 GPa (166 +/- 38 ksi) with a Weibull modulus of 5.3. The chemical composition and thickness of the fiber coatings were determined using scanning Auger analysis. Microstructural analysis of the fibers and the coatings was carried out by scanning electron microscopy and transmission electron microscopy. A microporous silica-rich layer approx. 200 nm thick is present on the as-received HPZ fiber surface. The BN coatings on the fibers are amorphous to partly turbostratic and contaminated with carbon and oxygen. Silicon carbide coating was crystalline whereas the silicon nitride coating was amorphous. The silicon carbide and silicon nitride coatings are non-stoichiometric, non-uniform, and granular. Within a fiber tow, the fibers on the outside had thicker and more granular coatings than those on the inside.
Document ID
19960047999
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Bansal, Narottam P. (NASA Lewis Research Center Cleveland, OH United States)
Wheeler, Donald R. (NASA Lewis Research Center Cleveland, OH United States)
Dickerson, Robert M. (NYMA, Inc. Brook Park, OH United States)
Date Acquired
September 6, 2013
Publication Date
July 1, 1996
Subject Category
Nonmetallic Materials
Report/Patent Number
NASA-TM-107254
E-10312
NAS 1.15:107254
Report Number: NASA-TM-107254
Report Number: E-10312
Report Number: NAS 1.15:107254
Accession Number
96N33517
Funding Number(s)
CONTRACT_GRANT: NAS3-27186
PROJECT: RTOP 505-63-12
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Related Records

There are no records associated with this record.
No Preview Available