Dynamic oxidation mechanism of carbon fiber reinforced SiC matrix composite in high-enthalpy and high-speed plasmas

Abstract

This work employed an inductively coupled plasma wind tunnel to study the dynamic oxidation mechanisms of carbon fiber reinforced SiC matrix composite (Cf/SiC) in high-enthalpy and high-speed plasmas. The results highlighted a transition of passive/active oxidations of SiC at 800–1600 °C and 1–5 kPa. Specially, the active oxidation led to the corrosion of the SiC coating and interruption of the SiO2 growth. The transition borders of active/passive oxidations were thus defined with respect to oxidation temperature and partial pressure of atomic O in the high-enthalpy and high-speed plasmas. In the transition and passive domains, the SiC dissipation was negligible. By multiple dynamic oxidations of Cf/SiC in the domains, the SiO2 thickness was not monotonously increased due to the competing mechanisms of passive oxidation of SiC and dissipation of SiO2. In addition, the mechanical properties of the SiC coating/matrix and the Cf/SiC were maintained after long-term dynamic oxidations, which suggested an excellent thermal stability of Cf/SiC serving in thermal protection systems (TPSs) of reusable hypersonic vehicles.

Unveiling surface stability and oxygen vacancy segregation of Yb2SiO5 and Lu2SiO5 by first‐principles calculations

“…𝐸 rel = 𝐸 𝑑 − 𝐸 unrel (10) where 𝐸 unrel is the total energy of the unrelaxed defective slabs. Figure 7B,D depicts the defect formation energies, chemical bond-breaking energies, and structural relaxation energies of the above five oxygen vacancies under 1500 K and 1 atm.…”

“…1,[4][5][6] However, CMCs are easily oxidized and corroded when exposed to a high-temperature environment containing molten CaO-MgO-Al 2 O 3 -SiO 2 (CMAS) and water vapor. [7][8][9][10][11] To avoid oxidation or corrosion on the CMCs components, therefore, there is an urgency to develop the environmental barrier coating (EBC). [12][13][14][15][16] Much attention and academic investigations have gone to the surface and related defects of EBC materials as they are believed to play a crucial role in various physical and chemical properties when applied in the engineering sector.…”

“…As an alternative to the Ni‐based superalloys, they can serve as hot sections for the next‐generation gas turbine engines which could be operated under higher temperatures 1,4–6 . However, CMCs are easily oxidized and corroded when exposed to a high‐temperature environment containing molten CaO–MgO–Al 2 O 3 –SiO 2 (CMAS) and water vapor 7–11 . To avoid oxidation or corrosion on the CMCs components, therefore, there is an urgency to develop the environmental barrier coating (EBC) 12–16 .…”

Effect of La2O3 content on the oxygen barrier ability of the HfB2‐SiC coating at 1973 K

“…The produced gaseous SiO not only causes catastrophic evolution and structural splitting of the oxygen barrier structure but also weakens the capacity of the Hf‐B‐Si‐O multiphase glass to inhibit oxygen penetration, which in turn aggravates the oxidation degree of the HfB 2 ‐SiC coating. The spread of oxygen through the defects generated by the dynamic evolution of the coating structure is the main reason for the damage to the dynamic stability of the oxygen barrier of the coating 23–25 . Therefore, it is considered necessary to enhance the dynamic oxygen resistance capacity of the Hf‐B‐Si‐O multiphase glass to inhibit the destructive evolution of the coating structure during the service process.…”

“…The spread of oxygen through the defects generated by the dynamic evolution of the coating structure is the main reason for the damage to the dynamic stability of the oxygen barrier of the coating. [23][24][25] Therefore, it is considered necessary to enhance the dynamic oxygen resistance capacity of the Hf-B-Si-O multiphase glass to inhibit the destructive evolution of the coating structure during the service process.…”