SALIENT FEATURES OF THERMAL-EXPANSION OF MULTILAYER CERMET COMPOSITES

The linear thermal expansion coefficient (LTEC) of multilayer brazed c ermet composites made of alternating plates of Si3N4 and Cu (ZrO2 and Cu) has been studied. The coefficient was observed to be anisrotropic parallel and perpendicular to the planet of brazing. In the first case the coefficient of the composite was practically equal to that of sil icon nitride and in the second case reached or at times even exceed th at of copper. Moreover the LTEC was considerably higher than the value calculated for the composite an the basis of the additivity principle , the assumption being that the copper and silicon nitride expand inde pendently. The anisotropy observed in the LTEC of the composite can be attributed to the anisotropy of copper expansion in such a material. The linear dimension of the same sample, heated repeatedly, was observ ed to decrease in the lateral direction; this is due to plastic deform ation of The copper and the resultant thinning of the sample.