Examination of milled h-BN addition on sintered Si3N4/h-BN ceramic composites

Silicon nitride (Si3N4) ceramics containing 1 and 5 wt.% of hexagonal boron nitride (h-BN) were prepared by attrition milling and hot-isostatic pressing. Thorough morphological characterizations have been carried out to reveal the influence of the milling parameters on the size of the h-BN additives. The results confirmed significant decrease in h-BN particle size by increasing milling time. The transmission electron microscopy observations revealed that the h-BN particles were incorporated into the ceramic matrix. The results showed that the increase of the h-BN content decreased significantly the hardness of materials. Moreover, the hardness values were higher when the size of h-BN was larger. The same tendency was observed in the case of Young?s modulus.