Oxidation behavior of non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution powders in air

Abstract

Multi-component solid solutions with non-stoichiometric compositions are characteristics of ultra-high temperature carbides as promising materials for hypersonic vehicles. However, for group IV transition-metal carbides, the oxidation behavior of multi-component non-stoichiometric (Zr,Hf,Ti)Cx carbide solid solution has not been clarified yet. The present work fabricated four kinds of (Zr,Hf,Ti)Cx carbide solid solution powders by free-pressureless spark plasma sintering to investigate the oxidation behavior of (Zr,Hf,Ti)Cx in air. The effects of metallic atom composition on oxidation resistance were examined. The results indicate that the oxidation kinetics of (Zr,Hf,Ti)Cx are composition dependent. A high Hf content in (Zr,Hf,Ti)Cx was beneficial to form an amorphous Zr-Hf-Ti-C-O oxycarbide layer as an oxygen barrier to enhance the initial oxidation resistance. Meanwhile, an equiatomic ratio of metallic atoms reduced the growth rate of (Zr,Hf,Ti)O2 oxide, increasing its phase stability at high temperatures, which improved the oxidation activation energy of (Zr, Hf, Ti)Cx.

Binary temporary photo-response of ZnSe:Mn/ZnS quantum dots for visible time-domain anti-counterfeiting

“…The PL quenching would result in failure to achieve multi-level anti-counterfeiting. Moreover, degradation of the Se-rich ZnSe:Mn QDs would be caused by the photoanodic corrosion effect from the excess hole traps of un-passivated Se 2− 43,44 in accordance with the increased low-energy adsorption band with prolonged photo-irradiation time, as shown in Fig. S3(a) †…”

Mechanisms responsible for enhancing low‐temperature oxidation resistance of nonstoichiometric (Zr,Ti)C

“…Thus, the Zr–Ti–C–O layer in this work might be an oxycarbide. Moreover, an oxycarbide is also observed during the oxidation of (Hf–Ta–Zr–Nb)C 45 and (Zr,Hf,Ti)C x 46 .…”

“…Thus, the Zr-Ti-C-O layer in this work might be an oxycarbide. Moreover, an oxycarbide is also observed during the oxidation of (Hf-Ta-Zr-Nb)C 45 and (Zr,Hf,Ti)C x 46 . Figure 7 shows the microstructure of ZrC 0.8 after oxidation at 500 • C for 1 h. The oxidized sample consisted of two layers: a Zr-C-O and a Zr-C (substrate).…”

Low thermal conductivity of dense (TiZrHfVNbTa)Cxhigh-entropy carbides by tailoring carbon stoichiometry

“…Although the thermal conductivity of ZrC x can be effectively reduced by tailoring the carbon stoichiometry, the large-scale application of the transition metal carbides is still restricted due to the stringent requirement for applications in an ultra-high-temperature insulation system. Recently, the emerging high-entropy carbides have evoked extensive research, possessing excellent mechanical properties [4,5], corrosion and oxidation resistance [6,7], low thermal conductivity [8][9][10], prominent electrical properties [11], and electromagnetic wave absorbing properties [12]. Therefore, adjusting the carbon stoichiometry of the high-entropy carbides is feasible to further lower the thermal conductivity and maintain moderate mechanical properties at the same time, making them promising to be candidates for thermal protection materials.…”