Oxidation Behaviour of Graphite /B₄C/SiC/ZrB₂ Composite in Dry and Moist Atmospheres

Abstract

High temperature oxidation tests from 600 to 1400•Ž were carried out for graphite/B4C/SiC/ZrB2 compo site in different atmospheres such as dry air, dry oxyg

Oxidation of ZrB[sub 2]-Based Ceramics in Dry Air

“…The introduction of second phases ͑i.e., SiC, ZrC͒ has succeeded in obtaining structurally stronger ZrB 2 -based composites with improved resistance to ablation/oxidation. [3][4][5]9,11,14,18,19 Chemical interactions between the reaction scale ͑formed during oxidation͒ and phases present in the bulk are very complex and strongly influence oxidation behavior. Alternative fabrication technology was recently investigated to produce near net shape components.…”

Preparation and Properties of Self‐Healing Coating for C/SiC Brake Materials

“…It was found that the oxidation of the coated C/SiC brake material was controlled by the area of the coating flaw such as microcracks and micropores. At the beginning of oxidation, the rate of oxidation of the coated C/SiC was very slow because oxidation was retarded by the glassy borosilicate coating that covered the active sites on the surface 10,16 . As the oxidation proceeded, the rate of the oxidation remained very slow because coating flaws such as the microcracks and micropores were sealed by the borosilicate glass owing to its lower viscosity, which allows it to self‐seal (as shown in Fig.…”

The effect of a graphite addition on oxidation of ZrB2–SiC in air at 1500°C

“…The layer provides passive oxidation behavior resulting in parabolic mass gain kinetics, which reduces the oxidation rate compared to pure ZrB 2 . 25,27 The SiO 2 -rich glassy scale remains protective up to at least 1600 • C on pure SiC. 27 For ZrB 2 -SiC, the SiO 2 is significantly less volatile than B 2 O 3 (∼10 5 times lower vapor pressure for SiO 2 than B 2 O 3 at 1500 • C), resulting in passive oxidation protection over a much greater temperature range for ZrB 2 -SiC than has been reported for pure ZrB 2 .…”

“…22 A number of additives have been used to improve the oxidation resistance of ZrB 2 -based materials. [23][24][25][26] The addition of SiC improves oxidation resistance at temperatures above 1200 • C by promoting the formation of a borosilicate glass layer, which reduces oxygen permeability on exposed surfaces. The layer provides passive oxidation behavior resulting in parabolic mass gain kinetics, which reduces the oxidation rate compared to pure ZrB 2 .…”