Dm. Liu et al., THERMAL-DIFFUSIVITY, HEAT-CAPACITY AND THERMAL-CONDUCTIVITY IN AL2O3-NI COMPOSITE, Materials science & engineering. B, Solid-state materials for advanced technology, 31(3), 1995, pp. 287-291
Thermal diffusivity, heat capacity, and thermal conductivity of Al2O3-
Ni composite with 5 vol.% of Ni particulate were investigated. The the
rmal conductivity of the composite increases monotonically with increa
se of Ni particle size, and approaches a limiting value for Ni particl
es of 2 mu m or larger. The reduced conductivity at smaller particle s
izes is due primarily to the increased interfacial resistance related
to the increase of Al2O3/Ni contact area, even though metal Ni has hig
her value of thermal conductivity than that of Al2O3. The mode of heat
conduction in the composite with the smallest Ni particulate, i.e. D=
0.1 mu m, is a result of both phonons and interfacial defects, and thi
s leads to the composite characterizing with a lower temperature-depen
dent thermal conductivity. The Kapitza radius of the composite was exp
erimentally determined as approximately 0.6-0.7 mu m, at which the Ni
conductivity is balanced by interfacial resistance, resulting in compo
site conductivity=matrix conductivity. This suggests that a minimum Ni
particle size of similar to 1.4 mu m is essentially required for the
improvement of the overall thermal conductivity in Al2O3-Ni composite.