Effect of rare-earth dopant (Sm) concentration on total hemispherical emissivity and ablation resistance of ZrB2/SiC coatings. Issue 16 (December 2016)

• Record Type: Journal Article
• Authors: Tan, Winnie; Adducci, Mitchell; Petorak, Christopher; Thompson, Brian; Brenner, Anneliese E.; Trice, Rodney W.
• Is Part Of: Journal of the European Ceramic Society. Volume 36:Issue 16(2016)
• Page Start: 3833
• Page End: 3841
• Publication Date: 2016-12
• Subjects: Emissivity -- Hypersonic -- Samarium -- Zirconium diboride -- Ablation; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2016.04.013
• Languages: English
• ISSNs: 0955-2219

Abstract

Abstract: The temperature of leading edges during hypersonic flight can be reduced by maximizing the emissivity of their surface. In this study, the concentration of a known emissivity modifier (Sm) has been varied (3, 5, and 8 mol% Sm in ZrB2 /SiC coatings) and the total hemispherical emissivity and ablation resistance of the coatings has been evaluated. Maximum emissivity was observed to occur for the 5 mol% Sm ZrB2 /SiC coating, with a value of 0.9 measured at 1600 °C. All the ablated Sm-doped coatings have an oxide scale consisting of m-ZrO2 and c1 -Sm0.2 Zr0.9 O1.9, and/or Sm2 Zr2 O7 depending on the Sm concentration. Large amounts of porosity were observed in the oxide scale of the ablated 8 mol% Sm ZrB2 /SiC coating. This was attributed to viscosity reduction of the B2 O3 and SiO2 glassy phases by the Sm 3+ and their subsequent vaporization. The 5 mol% Sm-doped ZrB2 /SiC demonstrated the optimal emissivity properties and dense oxide scale formation.