Development of ceramic matrix composites for application in the ceramic technology for advanced heat engines project

Technical Report · Wed Apr 01 00:00:00 EST 1992

OSTI ID:7019848

Yeh, H; Solidum, E; Karasek, K; Stranford, G; Yuhas, D; Schienle, J; Bradley, S ^[1]

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1. Allied-Signal Aerospace Co., Torrance, CA (United States). Garrett Ceramic Components Div.

The objective of this effort (Phase II of a multi-phase program) was to maximize the toughness of a high-temperature Si{sub 3}N{sub 4} (GN-10) by the near-net-shape fabrication technology established previously (Phase I). Acid-etched American Matrix SiC whiskers were selected as the reinforcement. Extensive green forming and densification process optimizations were conducted. The results showed that whisker addition increased the toughness slightly, but decreased the strength of the material. It has been recommended to discontinue the whisker reinforcement approach, and to instead pursue the in-situ grown-whisker reinforcement approach. To address future needs for the composite technology, two supplemental efforts were conducted using monolithic GN-10 Si{sub 3}N{sub 4}. These were nanometer deposition of sintering aids and ultrasonic characterization of drying. Spray drying, polymerization, basic precipitation, and evaporation yielded more uniform sintering aid distributions than conventional ball milling. Spray drying was selected for scale-up study. Improved mechanical properties were demonstrated. The results of the ultrasonic study showed that variations in ultrasonic compressional velocity in slip-cast components are more complex than anticipated. Specifically, it was found that the sonic velocity, as a function of moisture content, was double-valued. This behavior, together with the problems associated with maintaining uniform couplant, precludes the use of ultrasonics as a routine means of monitoring moisture content.

• Research Organization: Oak Ridge National Lab., TN (United States); Allied-Signal Aerospace Co., Torrance, CA (United States). Garrett Ceramic Components Div.
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 7019848
• Report Number(s): ORNL/Sub-85-22008/2; ON: DE92041378
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
20 FOSSIL-FUELED POWER PLANTS
36 MATERIALS SCIENCE
HEAT ENGINES
COMPOSITE MATERIALS
SILICON NITRIDES
TENSILE PROPERTIES
CERAMICS
DRYING
MATRIX MATERIALS
PROGRESS REPORT
REINFORCED MATERIALS
SILICON CARBIDES
SINTERING
WHISKERS
CARBIDES
CARBON COMPOUNDS
CRYSTALS
DOCUMENT TYPES
ENGINES
FABRICATION
MATERIALS
MECHANICAL PROPERTIES
MONOCRYSTALS
NITRIDES
NITROGEN COMPOUNDS
PNICTIDES
SILICON COMPOUNDS
330100* - Internal Combustion Engines
200104 - Fossil-Fueled Power Plants- Components
360201 - Ceramics
Cermets
& Refractories- Preparation & Fabrication
360203 - Ceramics
Cermets
& Refractories- Mechanical Properties