Elastic anisotropy in hot-pressed Si{sub 3}N{sub 4} composites: Role of in-situ {beta}-Si{alpha}{sub 3}N{sub 4} grains and added {beta}-Si{sub 3}N{sub 4} whiskers
Conference
·
OSTI ID:96540
- Univ. of Hawaii, Honolulu, HI (United States); and others
The elastic anisotropy in hot-pressed samples of {beta}-Si{sub 3}N{sub 4} monolithic polycrystalline composites and in composites with 5 to 35% {beta}-Si{sub 3}N{sub 4} whiskers have been investigated at room temperature by high precision acoustic interferometery. All of the samples, including the monolithic Si{sub 3}N{sub 4}, show anisotropy characterized as transverse isotropic about the hot-pressing (HP) direction and are described using the five elastic stiffness moduli for hexagonal symmetry. The principal anisotropy is revealed in the shear modulus difference, (C{sub 66} -C{sub 44})/C{sub 44}, which increases from 7% in the monolithic sample to 15% in samples with 10% or more whiskers. All the stiffness moduli except for C{sub 44} increase with the addition of whiskers. Young`s modulus in the HP direction is 5% smaller than in the HP plane in all samples. The whiskers enhance the shear anisotropy produced by the in-situ elongated {beta}-grains.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 96540
- Report Number(s):
- CONF-940416--
- Country of Publication:
- United States
- Language:
- English
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