The microstructures of SCS-6 and SCS-8 SiC reinforcing fibers

Conference · Wed Jan 01 00:00:00 EST 1992

OSTI ID:5701746

Sattler, M L; Kinney, J H; Zywicz, E ^[1]; Alani, R ^[2]; Nichols, M C ^[3]

---

1. Lawrence Livermore National Lab., CA (United States)
2. Gatan, Inc., Pleasanton, CA (United States)
3. Sandia National Labs., Livermore, CA (United States)

The microstructures of SCS-6 and SCS-8 SiC fibers have been examined and analyzed using high resolution transmission electron microscopy (HRTEM), microdiffraction, parallel electron energy loss spectroscopy (PEELS), x-ray diffraction and x-ray spectroscopy. The results of the study confirm findings from earlier studies wherein the microstructure of the fibers have been described as consisting of {beta}-SiC grown upon a monofilament turbostratic carbon core. The present study, however, provides much more detail regarding this microstructure. For example, PEELS spectroscopy and x-ray microscopy indicate that the composition of the SiC varies smoothly from SiC plus free C near the carbon core to SiC at the midradial boundary. The SiC stoichiometry is roughly preserved from the midradial boundary to the exterior interface. HRTEM, microdiffraction, and dark field images provide evidence that the excess carbon is amorphous free carbon which is most likely situated at the grain boundaries of the SiC. The x-ray microscopy results are also consistent with the presence of two phases near the core which consist of SiC and free carbon having density less than graphite (2.25 g/cc). This complex microstructure may explain the recent observations of nonplanar failure in composites fabricated with SCS fibers.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5701746
• Report Number(s): UCRL-JC-107929; CONF-920144-5; ON: DE92010449
• Resource Relation: Conference: 16. annual conference on composites, materials, and structures, Coca Beach, FL (United States), 13-16 Jan 1992
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
SILICON CARBIDES
MICROSTRUCTURE
FIBERS
FRACTURES
MECHANICAL PROPERTIES
THICKNESS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
CARBIDES
CARBON COMPOUNDS
COHERENT SCATTERING
CRYSTAL STRUCTURE
DIFFRACTION
DIMENSIONS
ELECTRON MICROSCOPY
FAILURES
MICROSCOPY
SCATTERING
SILICON COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360203 - Ceramics
Cermets
& Refractories- Mechanical Properties