Silicon Nitride Joining.
Annual rept. 1 Dec 80-31 Jan 82,
SRI INTERNATIONAL MENLO PARK CA
Pagination or Media Count:
The objective of this program is to investigate joining of ceramics through reactions between oxynitride melts and silicon nitride. The basis of the approach is to use joining materials that duplicate the composition of intergranular phases that exist in different types of hot-pressed or sintered Si3N4. A method has been devised to calculate average intergranular compositions from bulk analysis of Si3N4. Calculated compositions are similar to those determined by analytical electron microscopy. Oxynitrides that simulate the grain boundary phases in NC132 and NCX34 hot-pressed Si3N4 were prepared and used in joining experiments. The minimum joint thickness was 15 microseconds. The integrity of the joints is strongly dependent on the composition of the joining material and on the reaction temperature, but appears independent of the pressure of the nitrogen atmosphere, between 30 and 300 psi. Transmission electron microscopy studies of joined materials suggest that the liquid bonding material reacts with the ceramic surface, dissolving Si3N4 and penetrating into the ceramic. At the same time silicon oxynitride laths grow across the interface to form the joint. Author
- Physical Chemistry
- Ceramics, Refractories and Glass
- Fabrication Metallurgy