S. Baskaran et al., FIBROUS MONOLITHIC CERAMICS .4. MECHANICAL-PROPERTIES AND OXIDATION BEHAVIOR OF THE ALUMINA NICKEL SYSTEM, Journal of the American Ceramic Society, 77(5), 1994, pp. 1256-1262
Fibrous monolithic ceramics were fabricated in the alumina/nickel syst
em. The microstructure consists of high-aspect-ratio polycrystalline c
ells of alumina separated by thin cell boundaries of nickel. The nicke
l content in the material is 3 to 8 vol%. The fibrous monolith with un
iaxially aligned cells fails noncatastrophically in flexure. Bridging
ligaments of nickel, crack deflection along cell boundaries, and crack
branching in the axial direction are observed in flexure bars and not
ched beams. Strength values range from 246 to 375 MPa. Indentations ca
use controlled damage on the surface but do not introduce strength-deg
rading flaws. The alumina/nickel fibrous monoliths also show potential
for use at high temperatures in oxidizing environments. Noncatastroph
ic fracture behavior is observed at room temperature after 10 h at 120
0-degrees-C in air. The Ni cell boundary network is oxidized to a dept
h of 50 to 100 mum by this heat treatment. The NiO oxidation product i
n the cell boundaries reacts partly with alumina from the cells to for
m NiAl2O4, which would provide better protection.