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Porous ceramics with porosity up to 92.5 % have been successfully fabricated by freeze casting of polycarbosilane (PCS) solution. The effect of PCS concentration and thermal oxidation curing on the pore structure and compressive properties was investigated. Curing mechanism and thermodynamics were illuminated through analyzing the molecular structure, curing activation energy, and curing degree. Porous ceramics, mainly composed of SiC and a small amount of SiO2, have dendritic pore structure which well replicates the solidification morphology of camphene solvent. Results of FT-IR and Gaussian computation of PCS electron density show that Si–H and Si–CH3 bonds play a dominant role in thermal oxidation curing reaction. Both curing degree and ceramic yield increase with the increase in curing temperature and time. The curing degree of Si–H bond is close to 52 % and the corresponding ceramic yield is about 83 % when the porous PCS was cured at 200 °C for 90 min. Both polymer concentration and curing time have influences on the compressive strength of porous ceramics.

Being in the strategic direction of next-generation absorbers, multifunctional microwave absorbing materials possess great application value in military and commercial fields. However, the stringent requirements for performance necessitate the combination of multiple functions in such type of composites, which is still a challenge. This work aims to develop a foam-type absorber composed of multi-dimensional organic and inorganic materials, in which reduced graphene oxide sheets and polyvinyl alcohol membranes serve as the framework and crosslinker to form a three-dimensional skeleton. Meanwhile, SiC nanofibers as a reinforcing component can effectively suppress the over-stacking of reduced graphene oxide and enhance the conductivity and mechanical strength of cell walls. Among the remarkable microwave absorbing properties of the obtained foam, there are the ultra-light (9.85 mg cm-3), broadband (7.04 GHz), and strong absorption (reflection loss of -61.02 dB), all combined in the ultra-thin (2.5 mm). In addition, the foam possesses superelastic and excellent heat-insulating characteristics that ensure shock resistance, heat preservation, and infrared stealth. The remarkable versatility benefits from the porous structure, as well as from the synergistic effect of multi-dimensional organic and inorganic constituents of the foam. Therefore this study lays the foundation for the design of new-generation microwave absorbers with broad application potential.

As the representative MAX phase, Ti3SiC2 exhibits excellent mechanical strength and good temperature oxidation resistance, thus can be used to replace conventional ceramic matrix for the preparation of CMC composite. In this work, a new starting mixture containing different proportions of TiC and Si is proposed for in-situ synthesis of Ti3SiC2, in order to increase the yield while reducing costs and energy consumption. The results reveal that, as the sintering temperature increases, Si atoms gradually diffuse into the TiC crystal and replacing C atoms to form a Ti–Si eutectic (i.e. the Ti5Si3 phase), which then converts TiSi2 from sufficient Si source. Subsequently, either of these intermediates react with TiC and Si to form a Ti3SiC2 compound with SiC as a by-product. Mechanical analysis shows that, both flexural strength (312 ± 25 MPa) and fracture toughness (11.6 ± 1.1 MPa m1/2) have been significantly improved, by comparing with the Cf/SiC composite prepared by the same method. The toughening mechanism mainly derives from inherent merit of carbon fibers, and is assisted by the Ti3SiC2 grain, indicating the presence of this second phase, which is highly dispersed in the SiC matrix, effectively improves the toughness of the composite.

In this work, ZrB2–ZrC–SiC composite nanofibers were prepared by electrospinning combined with the carbothermal reduction method. The morphology, phase composition, and oxidation resistance of the composite nanofibers were investigated. The results showed that ZrB2–ZrC–SiC composite nanofibers with good crystallinity were obtained after calcination at 1550 °C. The obtained fibers distributed uniformly, and the average diameter was about 375 nm. ZrB2–ZrC–SiC nanofibers were oxidized at 587 °C, which was higher than that of the ZrB2–ZrC nanofibers. It revealed that the addition of SiC could improve the oxidation resistance of ZrB2–ZrC composite nanofibers.

Addition of oxygen in the interface between Cu and Al2O3 can significantly improve the wettability. In the present work, Cu/Al2O3 laminated composites were fabricated by bonding Cu foils with CuO-coated Al2O3 plates. Before bonding, the coated Al2O3 plates were pretreated at different temperature in the air. The effect of pretreated temperature on the interfacial microstructure, wettability and bending property were investigated. Phase composition in the interface after wetting test was characterized according to the thermodynamics of Cu–O system. The wetting mechanism and bending failure mode of Cu/Al2O3 laminated composites were also analyzed. Pretreated temperature significantly influences the wettability and bending strength of the composites. The contact angle decreased to about 22° when the pretreated temperature equal to 1100 °C. Continuous CuAlO2 in the interlayer is beneficial to the wettability between Cu melt and Al2O3, while other phases such as Cu2O and CuAl2O4 would increase the contact angle. Crack formation and propagation are the main failure mode of Cu/Al2O3 laminated composites during bending test. Different from the wettability, Cu/Al2O3 laminated composites fabricated with pretreated temperature at 1050 °C show the highest bending strength, although the contact angle is not the lowest on this condition. The reason is illustrated through analyzing the bending failure mode.

In this paper, ZrB2–ZrC composite nanofibers were prepared by electrospinning method followed by carbothermal reduction process. Nanofibers with ZrC content of 15, 35 and 50 wt%, respectively, were obtained by varying the n(B)/n(Zr) molar ratio. The oxidation resistance of fabricated nanofibers was investigated by the non-isothermal thermogravimetric method. The effect of ZrC content on the oxidation resistance of ZrB2–ZrC composite nanofibers was analyzed systematically. The Kissinger method was used to calculate the oxidative activation energy (E) of the fibers with different ZrC content. The results show that the E values of fiber with n(B)/n(Zr) equal to 2.5, 3.5 and 4 are 219, 362 and 275 kJ/mol. Among the prepared fibers, the fiber with n(B)/n(Zr) of 3.5 has the highest oxidative activation energy and the best oxidation resistance.

Solid solution ceramics of transition-metal carbides possess higher hardness and better oxidation resistance in comparison with monolithic transition-metal carbides. In this communication, (Ti, Zr)C solid solution nanofibers were successfully fabricated through electrospinning using polymeric precursors. The effect of n (Ti)/n (Zr) on the microstructure of nanofibers was investigated. Complete solid solutions of (Ti0·8Zr0.2)C and (Ti0·75Zr0.25)C were formed at 1600 °C when the value of n (Ti)/n (Zr) equal to 4 and 3, respectively. With a decrease in n (Ti)/n (Zr) to 2, Ti-rich and Zr-rich phases appear. The oxidation resistance of the fabricated nanofibers was tested by a non-isothermal method. The oxidation temperature of (Ti, Zr)C solid solution nanofibers is improved compared to TiC nanofibers.