NASA Scientific and Technical Aerospace Reports

As part of an ongoing effort to develop materials for resin transfer molding (RTM) of high performance/high temperature
composites, a new phenylethynyl containing imide designated as PETI-375 has been under evaluation. PETI-375 was prepared
using 2,3,3 ,4 - biphenyltetracarboxylic dianhydride (a-BPDA), 1,3-bis(4-aminophenoxy)benzene and 2,2 -
bis(trifluoromethyl)benzidine and endcapped with 4-phenylethynylphthalic anhydride. This material exhibited a stable melt
viscosity of 0.1-0.4 Pa sec at 280 C. High quality, void-free laminates were fabricated by high temperature RTM using unsized
T-650 carbon fabric and evaluated. After curing for 1 hour at 371 C, the laminates exhibited a glass transition temperature of
approx. 375 C by thermomechanical analysis. The laminates were essentially void and microcrack free as evidenced by optical
microscopic examination. The chemistry, physical, and composite properties of PETI-375 will be discussed.
Author
High Temperature; Resin Transfer Molding; Glass Transition Temperature; Synthesis (Chemistry)
20040074332 NASA Glenn Research Center, Cleveland, OH, USA
Characterization of C/Enhanced SiC Composite During Creep-Rupture Tests Using an Ultrasonic Guided Wave Scan
System
Roth, Don J.; Verrilli, Michael J.; Martin, Richard E.; Cosgriff, Laura M.; May 2004; 22 pp.; In English; 28th Annual
International Conference and Exposition on Advanced Ceramics and Composites, 25-30 Jan. 2004, Cocoa Beach, FL, USA
Report No.(s): NASA/TM-2004-213055; E-14333-1; No Copyright; Avail: CASI; A03, Hardcopy
An ultrasonic guided wave scan system was used to nondestructively monitor damage over time and position in a
C/enhanced SiC sample that was creep tested to failure at 1200 C in air at a stress of 69 MPa (10 ksi). The use of the guided
wave scan system for mapping evolving oxidation profiles (via porosity gradients resulting from oxidation) along the sample
length and predicting failure location was explored. The creep-rupture tests were interrupted for ultrasonic evaluation every
two hours until failure at approx. 17.5 cumulative hours.
Author
Silicon Carbides; Creep Rupture Strength; Porosity; Oxidation; Failure; Damage
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INORGANIC, ORGANIC AND PHYSICAL CHEMISTRY
Includes the analysis, synthesis, and use of inorganic and organic compounds; combustion theory; electrochemistry; and
photochemistry. For related information see category 34 Fluid Dynamics and Thermodynamics. For astrochemistry see category 90
Astrophysics.
20040068147 NASA Ames Research Center, Moffett Field, CA, USA
A Monte Carlo Sensitivity Analysis of CF2 and CF Radical Densities in a c-C4F8 Plasma
Bose, Deepak; Rauf, Shahid; Hash, D. B.; Govindan, T. R.; Meyyappan, M.; January 2004; 12 pp.; In English
Contract(s)/Grant(s): NAS2-99092; Copyright; Avail: CASI; A03, Hardcopy
A Monte Carlo sensitivity analysis is used to build a plasma chemistry model for octacyclofluorobutane (c-C4F8) which
is commonly used in dielectric etch. Experimental data are used both quantitatively and quantitatively to analyze the gas phase
and gas surface reactions for neutral radical chemistry. The sensitivity data of the resulting model identifies a few critical gas
phase and surface aided reactions that account for most of the uncertainty in the CF2 and CF radical densities. Electron impact
dissociation of small radicals (CF2 and CF) and their surface recombination reactions are found to be the rate-limiting steps
in the neutral radical chemistry. The relative rates for these electron impact dissociation and surface recombination reactions
are also suggested. The resulting mechanism is able to explain the measurements of CF2 and CF densities available in the
literature and also their hollow spatial density profiles.
Author
Monte Carlo Method; Radicals; Sensitivity Analysis; Fluorocarbons; Plasmas (Physics)
20040068242 Lockheed Martin Corp., Syracuse, NY, USA
Corrosion Behavior of 304 Stainless Steel in High Temperature, Hydrogenated Water
Ziemniak, S. E.; Hanson, M.; May 2001; 40 pp.; In English
Report No.(s): DE2004-821681; LM-01K046; No Copyright; Avail: Department of Energy Information Bridge
The corrosion behavior of an austenitic stainless steel (UNS S30400) has been characterized in a 10,000 hour test
conducted in hydrogenated, ammoniated water at 260 degrees C. The corrosion kinetics were observed to follow a parabolic
rate dependency, the parabolic rate constant being determined by chemical descaling to be 1. 16 mg dm(sup -2) hr(sup -1/2).
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