Oxidation Behavior at 1600 °C of Si‐SiC‐ZrB₂ Composites Produced by Si Reactive Infiltration

Abstract

Si–SiC–ZrB2 are produced by the reactive infiltration with molten silicon in porous SiC–C–ZrB2 preforms. It is observed that oxidized Si–SiC–ZrB2 ceramics present a layered structure composed of an outer layer of silica and a borosilicate glass intermediate layer with ZrO2 particles and the unoxidized bulk material. The graphs show that the passivation is very effective already after 5 min of oxidation. The thermograms do not vary significantly when the oxidation times are increased.

Effect of ZrB2 addition on the oxidation behavior of Si-SiC-ZrB2 composites exposed at 1500°C in air

“…The relative volume amounts of Si, SiC and ZrB 2 phases have been determined from both image analysis and an X-ray diffraction (XRD)–based external standard method, as already described in our previous paper (14).…”

“…They showed the following layered structure: a surface borosilicate layer rich in silica, an underlying borosilicate glassy layer including ZrO 2 particles (BSZ) and the unoxidized bulk material. It should be noted that the formation of the “SiC-depleted region,” which many authors report for oxidized ZrB 2 -SiC materials, was not observed (14-16).…”

“…In our previous work (14), we investigated the properties of Si-SiC-ZrB 2 materials after short oxidation times. They showed the following layered structure: a surface borosilicate layer rich in silica, an underlying borosilicate glassy layer including ZrO 2 particles (BSZ) and the unoxidized bulk material.…”

Pressureless sintering of (ZrB2–SiC–B4C) composites with (Y2O3+Al2O3) additions

“…ZrB 2 has been investigated for its oxidation performance since 1960s [40,41]. During this period the reported findings were reviewed by many researchers [42][43][44]. Upon heating in air the monolithic ZrB 2 , oxidizes to form skeleton of ZrO 2 and B 2 O 3 liquid at temperatures as low as 450°C.…”

Cyclic Ablation Behaviors of ZrB2–SiC Composites Sintered with Nano‐Sized Particles

“…However, the pure metal diborides do not fully possess oxidation resistance necessary to survive the oxidizing environment typical for hypersonic re‐entry into the earth atmosphere. Therefore, some additives, especially for SiC, are often used in the densification processes to enhance the sinterability and density, and improve the mechanical properties by reducing the grain sizes …”