Ceramics with zero thermal expansion coefficients at room temperature (293K) were
investigated. We found the thermal expansion coefficient was controlled by a compounding ratio of
lithium aluminum silicate (LAS) and silicon carbide (SiC), which have negative and positive thermal
expansion coefficients respectively. Although it was difficult to densify the composite of the LAS and
SiC (LAS/SiC) in the sintering process, an addition of nitride improved the sinterability of the
LAS/SiC. In order to examine the effect of the nitride additive, at first, the melting point of the LAS
with silicon nitride (Si3N4) or aluminum nitride was measured by TG-DTA. The melting point of the
LAS decreased with existence of nitride. It is believed that the densification of the LAS/SiC was
promoted by the nitride, because the nitride causes the LAS/SiC to form a liquid phase, thereby
decreasing the melting point. Next, the lattice constant of the LAS with Si3N4 was measured by XRD
and it was verified that the a-axis was longer and the c-axis was shorter than those of the LAS without
additive. It is supposed that this phenomenon is due to the substitution of nitrogen for oxygen in the
LAS lattice, and the decrease of the melting point of the LAS with nitride seems to be influenced by
this substitution of nitrogen.
Thermal Expansion Coefficients of Unidirectional and Angle Plied Silicon-Carbide Fiber-Reinforced Aluminum Alloys
