Development of ceramic matrix composites for application in Ceramic Technology for Advanced Heat Engine program

Technical Report · Wed Apr 01 04:00:00 EST 1992

OSTI ID:7267601

Buljan, S T; Baldoni, J G; Huckabee, M L; Neil, J; Hefter, J ^[1]

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1. GTE Labs., Inc., Waltham, MA (United States)

The objectives of the program are to develop an advanced toughened silicon nitride composite and a process for near net shape part fabrication. This program was initiated in 1985. The initial phase of the program considered particulate and whisker-reinforced composites and examined the effect of TiC and SiC dispersoids on fracture toughness of Si{sub 3}N{sub 4}. The best results were obtained with whisker reinforcements. Silicon carbide whisker-reinforced Si{sub 3}N{sub 4} was selected for further development. A predictive model that relates microstructure-fracture toughness dependence developed and scrutinized in the course of these studies has shown that fracture toughness of polycrystalline ceramics could be affected by changes of grain size and shape as well as strength of intergranular bond. Accordingly, it was shown that a deflection/debonding mechanism could utilize Si{sub 3}N{sub 4} whiskers to toughen Si{sub 3}N{sub 4} body. Si{sub 3}N{sub 4}-SiC composites offer a number of distinct advantages over monolith,'' which in addition to their improved thermal shock and wear resistance (due particularly to improved conductivity and hardness), Si{sub 3}N{sub 4}-SiC composites are tailorable with respect to high-temperature properties. It was considered that in heat engine applications, Si{sub 3}N{sub 4}-SiC whisker composites, due to their higher hardness, thermal conductivity, thermal shock, and wear resistance, have a definite advantage and warrant further development. In the current program (Phase 11), 1987--1989, the properties were further improved to achieve nearly two times higher fracture toughness and considerably improved elevated temperature (1400{degrees}C) strength of the composite. These improvements were obtained through optimization of processing and modifications of composite phase assembly, primarily intergranular phase.

• Research Organization: Oak Ridge National Lab., TN (United States); GTE Labs., Inc., Waltham, MA (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 7267601
• Report Number(s): ORNL/Sub-85-22011/2; ON: DE92041379
• Country of Publication: United States
• Language: English

Related Subjects

20 FOSSIL-FUELED POWER PLANTS
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33 ADVANCED PROPULSION SYSTEMS
330100* -- Internal Combustion Engines
36 MATERIALS SCIENCE
360203 -- Ceramics
Cermets
& Refractories-- Mechanical Properties
CARBIDES
CARBON COMPOUNDS
CERAMICS
COMPOSITE MATERIALS
CRYSTAL STRUCTURE
CRYSTALS
DOCUMENT TYPES
ENGINES
FRACTURE PROPERTIES
HEAT ENGINES
MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
MONOCRYSTALS
NITRIDES
NITROGEN COMPOUNDS
PNICTIDES
PROGRESS REPORT
REINFORCED MATERIALS
SILICON CARBIDES
SILICON COMPOUNDS
SILICON NITRIDES
WHISKERS