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Sessile drop contact angles between liquid aluminum alloys and solid beryllium, 'boron carbide, and graphite were measured to 840°C under vacuum and in helium. Little wetting occurred between most of the combinations, but at 20% magnesium the contact angle on beryllium decreased to 6 8 ' .Low contact angles were noted for the binary aluminum alloys on graphite coated with titanium.

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Wetting tests were performed with refractory metalceramic combinations selected on the basis of previous compatibility studies. Sessile drop contact angles between liquid Cr, V, Pt, Rh, Mo, and Mo-Re alloy and solid Thoz, HfOz, ZrOz, HfC, TaC, and ZrC were measured at temperatures up to 2800°C in helium. Little wetting occurred between these metals and the refractory oxides, but Mo and the Mo-Re alloy did wet the refractory carbides. Microscopic examination of the metalceramic interfaces showed that HfC-Mo-40 wt% Re and ZrC-Mo-40 wt% Re had highly desirable wetting and solubility characteristics for making cermets. Specimens were fabricated from these two systems with 25 and 50 vol% metal by cold-pressing and sintering and by hotpressing. The microstructures of these cermets consisted of small, uniformly dispersed carbide particles in Mo-Re matrixes. The hardnesses and transverse rupture strengths of these cermets indicate that they have considerable promise for high-temperature applications.

Moessbauer effect spectroscopic studies were made on Na-FeSi02 glasses before and after wetting experiments on steel in an Ar atmosphere. The glasses prepared under reducing conditions contained Fe3+ ions. The Fez+/Feq+ ratio for all glasses increased a5 the time at wettability test temperature was increased. Iron in the glasses (according to isomer-shift data) was possibly octahedrally coordinated. The Fe environment in glasses very nearly saturated with Fe oxide was most symmetrical. The glasses prepared under reducing conditions exhibited more symmetrical Fe environments than those prepared under oxidizing conditions. The structural symmetry in the glasses very nearly saturated with Fe oxide facilitated the electron transfer reaction, 2Fe"++ Feo= 3Fep+; the conversion to Fez+ occurred to the greatest extent in these glasses.