Using a drop calorimeter, the heat content of TiC was measured between 1274° and 2799°K, and that of ZrC between 1275° and 2788°K.

High temperature strengthening mechanism of hafnium carbide in a tungstenrhenium matrix AIP Conf.

The heat contents of γ-phase uranium from 1205° to 1394°K and of molten uranium from 1415° to 1579°K were measured using a drop calorimeter.

During the liquid-phase sintering of W-Ni-Fe composites, solid tungsten single crystal spheroids are surrounded by a molten matrix of W-Ni-Fe. These spheroids grow in a regulated manner If either the sintering time Is Increased or if the sintering temperature is raised. Since the slope of the log diameter-log time plot Is 1/3, and should remain constant because it is based on the dissolution of tungsten from the small spheroids with simultaneous precipitation of tungsten from the molten matrix onto the larger spheroids, one should be able to characterize the behavior of any new composite composition by just one sintering experiment In a calibrated temperature gradient.A low matrix volume composite (95% K-3.5% N1-1.5Z Fe) sintered in a temperature gradient showed anomalous behavior In that the spheroid aize did not decrease with decreasing temperature in the gradient, and the average spheroid size was much larger than expected based on constant sintering temperature experiments. Furthermore, composites of higher matrix volume (92% W-or 892 W with the same nickel to iron ratio) behaved differently in that they had a smaller average spheroid aize at the lower temperatures in the gradient. Since copper and tungsten are mutually insoluble, and since copper is dissolved readily by the matrix, copper was injected into both presintered and liquid-phase sintered composites to follow matrix flow during subsequent sintering treatments. The copper concentration decreased with distance from the hot zone for high volume matrix alloys, pretty much in accordance with liquid diffusion theory, but in the low volume matrix alloys where the volume of solid tungsten spheroids Is higher and should impede matrix motion even more, the copper was distributed almost uniformly throughout the matrix that was molten during the sintering. Since the spheroid compositions, matrix compositions, matrix densities, spheroid surface tensions, matrix surface tensions, and aost other properties are the same for all specimens, the seemingly anomalous behavior Is attributed to some mechanism dependent on capillary action since the decreased pore radius between the spheroids in the low matrix volume composites Increases the capillary forces by about 25Z.

No abstract