In situ temperature monitoring has become extremely imperative in high-temperature harsh environments and polymer-derived ceramics (PDCs) as sensing materials have attracted great attention. However, the stability and oxidation/corrosion resistance of PDCs cannot be simultaneously achieved at the moment, limiting their practical application. Herein, polymer-derived SiAlBCN ceramics were synthesized via polymer conversion method under different pyrolysis temperatures. Their microstructure evolution, high temperature sensing properties, and stability were investigated in detail. The results show that the amorphous SiAlBCN phase grows more orderly and the size of the free carbon phase enlarges with the increasing temperature. The defect concentration displays a decreasing tendency. Concurrently, the SiAlBCN ceramics as sensing materials exhibit a good temperature–resistance property from roo temperature to 1100 ℃. The fabricated SiAlBCN temperature sensor possesses excellent stability, repeatability, and accuracy. Moreover, SiAlBCN ceramics exhibit distinguished oxidation/corrosion resistance after 100 h treatment at 1200 ℃ in a water/oxygen environment, which is attributed to their low corrosive rate constant (0.57 mg/(cm²·h)) and oxidative rate constant (3.43 mg²/(cm⁴·h)). Therefore, polymer-derived SiAlBCN ceramics as sensing materials, which possess outstanding stability and oxidation/corrosion resistance, have great potential for in-situ monitoring of extreme environmental temperatures in the future.

In this work, a novel process, oscillatory pressure-assisted sinter forging (OPSF), for the preparation of high-performance ceramic composites was reported. Compared with the samples made by conventional sinter forging (SF) and hot oscillatory pressing (HOP), the SiC whisker reinforced Al₂O₃ composites (SiC_w–Al₂O₃) prepared by OPSF at the same temperature exhibited a higher density and significantly improved the mechanical properties. The improvements in densification and performance are attributed to simultaneous enhanced shear deformation at both macro- and micro-scales, resulting from the combination of die-free configuration and oscillatory pressure of OPSF. And the strength of grain boundary is greatly increased when the temperature reaches 1600 ℃ of OPSF, due to that the grain-boundary sliding became pronounced at higher temperatures. The current results shed light on a powerful technique for preparing ceramic composites, which is likely applicable to other systems.

Alumina whisker reinforced zirconia ceramic composite was prepared by both hot oscillatory pressing (HOP) and conventional hot pressing (HP). The results show that compared with HP, HOP can significantly increase the final density and densification rate of the material. Analysis of densification kinetics reveals that the predominant densification mechanism transits from grain boundary sliding in the beginning to the diffusion in the later stage. The main effect of the oscillating pressure is to increase the densification rate in the process of grain boundary sliding. The current study suggests that HOP is a promising technique for densifying whisker reinforced ceramics.

Electromagnetic absorption (EMA) materials with light weight and harsh environmental robustness are highly desired and crucially important in the stealth of high-speed vehicles. However, meeting these two requirements is always a great challenge, which excluded the most attractive lightweight candidates, such as carbon-based materials. In this study, SiC_nw-reinforced SiCNO (SiC_nw/ SiCNO) composite aerogels were fabricated through the in-situ growth of SiC_nw in polymer-derived SiCNO ceramic aerogels by using catalyst-assisted microwave heating at ultra-low temperature and in short time. The phase composition, microstructure, and EMA property of the SiC_nw/SiCNO composite aerogels were systematically investigated. The results indicated that the morphology and phase composition of SiC_nw/SiCNO composite aerogels can be regulated easily by varying the microwave treatment temperature. The composite aerogels show excellent EMA property with minimum reflection loss of -23.9 dB@13.8 GHz, -26.5 dB@10.9 GHz, and -20.4 dB@14.5 GHz and the corresponding effective bandwidth of 5.2 GHz, 3.2 GHz, and 4.8 GHz at 2.0 mm thickness for microwave treatment at 600 ℃, 800 ℃, and 1000 ℃, respectively, which is much better than that of SiCN ceramic aerogels. The superior EMA performance is mainly attributed to the improved impedance matching, multi- reflection, multi-interfacial polarization, and micro current caused by migration of hopping electrons.

Pressure measurement with excellent stability and long time durability is highly desired, especially at high temperature and harsh environments. A polymer-derived silicoboron carbonitride (SiBCN) ceramic pressure sensor with excellent stability, accuracy, and repeatability is designed based on the giant piezoresistivity of SiBCN ceramics. The SiBCN ceramic sensor was packaged in a stainless steel case and tested using half Wheatstone bridge with the uniaxial pressure up to 10 MPa. The SiBCN ceramic showed a remarkable piezoresistive effect with the gauge factor (K) as high as 5500. The output voltage of packed SiBCN ceramic sensor changes monotonically and smoothly versus external pressure. The as received SiBCN pressure sensor possesses features of short response time, excellent repeatability, stability, sensitivity, and accuracy. Taking the excellent high temperature thermo-mechanical properties of polymer-derived SiBCN ceramics (e.g., high temperature stability, oxidation/corrosion resistance) into account, SiBCN ceramic sensor has significant potential for pressure measurement at high temperature and harsh environments.