Due to their excellent thermal and mechanical properties silicon‐based ceramics and composites are prime candidates for high temperature structural applications. In this communication the authors report for the first time that amorphous silicoaluminum carbonitride (SiAlCN) ceramics possess anomalously high resistance to oxidation and hot‐corrosion. A mechanism underlying the observed phenomena is discussed.

To reduce the cost of nanocomposites and improve the dispersion of nanoparticles, Al2O3np/SiCnp/Al hybrid nanocomposites are fabricated by combining liquid-state blowing and ultrasonic-assisted casting. The average grain size of the matrix decreases to 39 μm in Al2O3np/SiCnp/Al, which shows improvements of approximately 118% and 26% as compared to those of Al2O3np/Al and SiCnp/Al, respectively. X-ray Diffractometer (XRD) results confirm the presence of SiCnp and Al2O3np in hybrid nanocomposites. The dispersed SiCnp and Al2O3np are homogeneously distributed in the matrix and no clusters consisting of SiCnp and Al2O3np exist in the microstructure. Theoretical analyses also verify that there is little possibility for clusters to form in the melt. Good bonding between nanoparticles and Al is demonstrated. Neither cavities nor reaction products exist at the interface. The ductility and the strength of Al2O3np/SiCnp/Al are improved. The improvement in yield strength of Al2O3np/SiCnp/Al, in comparison with that of A356, is about 45%.

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An interfacial nanocomposite layer was proposed to investigate the effect of SiCnps on interfacial thermal resistance between Si and Al.

The high-temperature oxidation resistance of AISI 321 stainless steel for solar thermal power generation heat exchanger highly determines its service life. Therefore, in this work, aluminizing treatment and aluminizing with subsequent laser shock peening (LSP) were employed to improve the high-temperature oxidation resistance of AISI 321 stainless steel at 620°C. The results showed that these two treatments decreased the oxidation rate as compared to the base AISI 321 steel. Concretely, the optimal oxidation resistance was observed in the aluminized steel before an oxidation testing time of 144 h due to the increased the entropy of the LSP-treated specimen. After 144 h, however, the LSP-treated sample showed the best oxidation resistance because of the formation of protective α-Al2O3. For the LSP-treated samples, the large amount of sub-grain boundaries formed on aluminized layer could act as the fast short-circuit path for the outward diffusion of Al element, facilitating the rapid nucleation of α- Al2O3. Meanwhile, the aluminized layer is able to isolate the contact between oxidation environment and matrix, thereby decreasing the oxidation rate. Further, the oxidation parabolic constant D(t) of LSP-treated steel was calculated to be minimum (6.45787×10–14), which is respectively 69.18% and 36.36% of aluminized steel and 321 steel during the whole oxidation process. Consequently, the combination of aluminizing and LSP can better improve the high-temperature oxidation resistance of 321 stainless steel.

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