Prevention of SiC‐fiber decomposition via integration of a buffer layer in ZrB ₂ ‐based Ultra‐high temperature ceramics

A ZrB2-based ceramic, containing short Hi-Nicalon SiC fibers, was fabricated with a Mo-impermeable buffer layer sandwiched between bulk and the outermost oxidation resistant ZrB2–MoSi2 layer, in order to prevent inward Mo diffusion associated fiber degradation reactions. This additional consisted of ZrB2 doped either Si3N4 or polymer-derived ceramics (PDCs) SiCN SiHfBCN. Scanning electron microscopy imaging elemental mapping via energy-dispersive X-ray spectroscopy showed that this tailored sample geometry provides an effective barrier fibers from deterioration due reactions Mo-compounds. In contrast, structure reference without is strongly degraded by MoSi2 into core. The comparison three buffer-layer systems moderate alteration case addition, whereas PDC-doped samples hardly any structural change within observed. stepwise reaction mechanism deduced, based on continuous progression zone propagates toward top layer. such as consequence different eutectic melts forming layers, is, first SiC-fiber-containing bulk, then itself, finally at high temperature, allows for separation fibers. Subsequent 1500°C 1650°C 15 min did not affect efficiency all since no changes regarding were observed, compared non-oxidized samples.