The microstructures of the SRBSN specimens are presented in Figures 3(a) and 3(b).
In order to determine the dependency of the evaporation loss of MgO on its particle size, the residual contents of Mg species in both the RBSN and SRBSN samples were measured by ICP and XRF, respectively.
The area fractions of [Si.sub.3][N.sub.4] grains in different sizes in the SRBSN samples are plotted in Figure 4.
Therefore, it is reasonable to conclude that the coarser MgO additive contributed to the inhomogeneous distribution of the liquid phase in the SRBSN sample during the postsintering process, which has a significant influence on the high thermal conductivity by promoting the abnormal grain growth.
In this study, the effects of the particle size of MgO when used as an additive on the microstructure and thermal conductivity of SRBSN were systematically investigated.
Knitter, "Processing of microcomponents made of sintered reaction-bonded silicon nitride (SRBSN).
Caption: Figure 1: Measurement of densities and nitridation degree for the SRBSN fabricated by the postsintering of RBSN.
Caption: Figure 2: XRD patterns and phase analysis for the RBSN (a) and SRBSN (b) specimens.
Caption: Figure 3: SEM micrographs ((a) Ac and (b) Af) and image analysis ((c) Ac and (d) Af) of the SRBSN.