Oxidation Behavior of SiC Platelet‐Reinforced ZrB₂ Ceramic Matrix Composites

Abstract

Zirconium diboride (ZrB 2 ) ceramic matrix composites reinforced by silicon carbide platelets (SiC pl ) were prepared by hot pressing. Five groups of specimens were prepared, in which the contents of SiC platelets were 0, 5, 10, 15 and 20 vol%, respectively. The oxidation behaviors of specimens at different temperatures from 8001 to 16001C for 1 h and at 12001C for different times from 0.5 to 4 h were investigated. With the increase of SiC pl content, the mass gain exhibited a decreasing trend. Oxidation thermodynamics and kinetics of the SiC pl /ZrB 2 composites were discussed. A characteristic structure of hollow quadrangular prismy ZrO 2 crystal emerged on the sample surface after oxidation was found and the possible formation mechanism was also presented. The surface element analysis indicated that the main products of oxidation were m-ZrO 2 , SiO 2 , and borosilicate (aluminosilicate).

Modeling Oxidation Kinetics of SiC‐Containing Refractory Diborides

“…1 Several additions and compositional refinements are being tried to enhance their oxidation resistance, but SiC-containing ZrB 2 or HfB 2 are the most studied, with sufficient data to enable a modeling-based analysis and understanding of their oxidation behavior. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The oxidation behavior is dominated by parabolic kinetics despite formation of a porous oxide of the refractory metal. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The oxidation behavior is dominated by parabolic kinetics despite formation of a porous oxide of the refractory metal.…”

Oxidation behavior of ZrB2/SiC laminates: Effect of composition on microstructure and mechanical strength

“…sintered by spark plasma synthesis 21 or by pressureless sintering at 2150 • C. 22 In all cases the densification can be enhanced by using proper sintering aids; among them SiC has proved to be very effective. The addition of SiC can also improve flexure strength, 4,5,8 K Ic 5,17 and creep behavior. 23 Oxidation behavior of ZrB 2 and some ZrB 2 /SiC composites (containing from 10 to 30 vol.% of SiC) has been well investigated in the temperature range from 800 to 2000 • C 5,6,[9][10][11][12][13][14][15][16]18,19,21 and recently well reviewed by Fahrenholtz and Hilmas.…”

“…20 Pure ZrB 2 undergoes oxidation starting from 800 • C according to the reaction: ZrB 2(s) + 5/2O 2(g) ↔ ZrO 2(s) + B 2 O 3(s,l) (1) The liquid layer of B 2 O 3 grants protection from oxidation up to 1100-1200 • C. Above 1200 • C the volatilization of B 2 O 3 , which exposes the underlying porous ZrO 2 scale, dramatically worsens the oxidation resistance of ZrB 2 . 16,17,20 The addition of SiC particles to a ZrB 2 matrix greatly improves oxidation behavior at high temperatures since it changes the oxide scale microstructure. 5,14,[16][17][18]20,21 Below 1200 • C ZrB 2 /SiC composites behave like pure ZrB 2 since they undergo oxidation more quickly than SiC thus giving a passive B 2 O 3 glassy surface layer.…”

“…16,17,20 The addition of SiC particles to a ZrB 2 matrix greatly improves oxidation behavior at high temperatures since it changes the oxide scale microstructure. 5,14,[16][17][18]20,21 Below 1200 • C ZrB 2 /SiC composites behave like pure ZrB 2 since they undergo oxidation more quickly than SiC thus giving a passive B 2 O 3 glassy surface layer. Above this temperature also SiC quickly oxidizes according to the reaction:…”

“…5,[9][10][11][12][13][14][15][16][17][18][19][20][21] It consists of an external borosilicate glassy layer and an underlying layer made of a skeleton of crystalline ZrO 2 , with voids filled in by the glassy phase. The B 2 O 3 content within the glassy phase decreases with the temperature increase owing to evaporation and at around 1500 • C the glassy layer facing the atmosphere mainly consists of silica.…”