Carbon-based composites are widely utilized in aerospace engines, thermal protection systems of hypersonic vehicles, and ultrahigh-temperature structural components, due to their lightweight nature, high strength, excellent mechanical properties, and thermal stability. However, the inherent susceptibility of carbon-based composites to high-temperature oxidation significantly limits their service life, highlighting the urgent need for the development of efficient oxidation-resistant barriers to enhance the long-term operational stability. In recent years, ultra-high temperature ceramic (UHTC) coatings have attracted considerable attention owing to their outstanding oxidation resistance. Nevertheless, such protective coatings still face critical challenges to hinder practical applications, including crack propagation, dynamic consumption instability of oxidation glass films, generation of oxidation holes and interfacial damage, which remain prevalent. In this work, a comprehensive overview of the research progress in UHTC coatings for carbon-based composites is provided, with particular emphasis on examining the influence of hierarchical structural design on oxidation resistance. Specifically, the role of advanced manufacturing techniques in optimizing microstructural stability and interfacial bonding strength is thoroughly discussed. Furthermore, the high-temperature oxidation protection mechanisms of UHTC coatings are examined, including strategies to optimize the composition of the oxidation glass film, stabilize the self-generated glass phase, and enhance densification of coating. In addition, various characterization methods are discussed for evaluating the oxidation resistance of the coatings, along with a systematic evaluation of stability under different service conditions. Finally, analysis of current technical challenges and unresolved issues, especially challenges and technical prospects regarding the field of oxidation-resistant coatings for carbon-based composites are discussed, while offering perspectives on future developments.

Cr₂AlC, as a ternary layered MAX phase ceramic with excellent oxidation resistance and ablation resistance, has great potential in thermal protection materials. To further tap its potential as a recyclable thermal protection material in extreme environment, the cyclic ablation performance of Cr₂AlC under nitrogen plasma flame at 1600^° C was systematically studied in this paper. During the cycles (each lasting three minutes) of ablation, Cr₂AlC maintained structural integrity and exhibited low linear and mass ablation rates. After three cycles of ablation, the linear ablation rate and mass ablation rate were 0.050μ" " m/s and 0.048mg/s, respectively. The analysis of surface and near-surface components shows that Al_8 Cr_5 produced by the decomposition of Cr₂AlC is the origin of the excellent ablation performance of Cr₂AlC ceramics. However, as the cycle time and total ablation time increase, Cr₂AlC and Al_8 Cr_5 near the surface will be depleted under high-temperature oxidation, leading to material failure. This study presents the excellent cycling and long-term ablation properties of Cr₂AlC ceramics, revealing their enormous application prospects in reproducible thermal protection materials.

This study explored the prevention of mild steel (MS) corrosion in sulfuric acid through deployment of N, N-dibutylaniline (NNDBA) as an organic inhibitor. The inhibition efficacy was meticulously scrutinized using a blend of qualitative and quantitative methodologies. The gravimetric method was executed across a spectrum of NNDBA concentrations (10^-1 M -10^-7 M ) and temperatures, 298 K-328 K (with 10 K increments), facilitating an intricate kinetic and thermodynamic exploration of the inhibition mechanism. Adsorption isotherm analyses affirmed NNDBA's adherence to Langmuir's model, signifying a monolayer adsorption paradigm. The adsorption process was found to be spontaneous and thermodynamically favorable, predominantly governed by physisorption. Empirical data delineated an inverse relationship between temperature and inhibition efficiency, whereas an augmentation in NNDBA concentration bolstered corrosion resistance. Potentiodynamic Polarisation (PDP) confirmed that NNDBA is a mixed-type inhibitor with a maximum efficiency of 92.4%. Electrochemical Impedance Spectroscopy (EIS) measurements revealed a marked decrement in the double-layer capacitance at the Fe/H₂SO₄ interface, corroborating inhibitor adsorption. Notably, the lower value of the phase shift exponent n for NNDBA suggests increased surface heterogeneity due to inhibitor film formation. Scanning Electron Microscopy (SEM-2D) and Atomic Force Microscopy (AFM-3D) unveiled distinct morphological alterations indicative of surface passivation. Density functional theory (DFT) calculations provided insights into the electronic structure of NNDBA, revealing a highly negative E_HOMO, low E_LUMO, and a small ΔE(5.24eV), all suggesting strong reactivity and the formation of a stable metal-inhibitor complex. The mechanistic pathway and spatial orientation of the interaction between the NNDBA molecule and MS surface were explored through molecular dynamics simulation to gain insights into its inhibitory behavior. Thus, the theoretical insights harmonize with experimental findings, substantiating its efficacy as a potent corrosion mitigant.