IMPROVED THERMOCHEMICAL STABILITY IN CARBON-REINFORCED BORIDE MATRIX COMPOSITES

REFRACTORY BORIDE MATRICES (ZRB(2), HFB(2)) REINFORCED WITH HIGH MODULUS CARBON FIBERS SHOW PROMISE AS ULTRAHIGH TEMPERATURE STRUCTURAL MATERIAL. THE MAXIMUM USE TEMPERATURE IS LIMITED BY THE MUTUAL REACTIVITY OF THE CONSTITUENT MATERIALS AND THE FORMATION OF LIQUID PHASES WITH SIGNIFICANTLY LOWER MELTING TEMPERATURES THAN EITHER THE MATRIX OR REINFORCING PHASE. THE PROPOSED RESEARCH WILL EXAMINE, THROUGH DETAILED THERMOCHEMICAL MODELING, THE FEASIBILITY OF INTERMETALLIC COMPOUND AND OTHER INTERFACIAL BARRIER LAYERS TO RETARD DIFFUSIVE TRANSPORT BETWEEN THE MATRIX AND REINFORCING PHASES, THUS PERMITTING UTILIZATION OF THESE COMPOSITES AT HIGHER TEMPERATURES FOR LONGER PERIODS OF TIME.