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SiOC/HfO2‐based ceramic nanocomposites with in situ formed HfO2 nanoparticles were prepared via a single‐source precursor (SSP) approach starting from a polymethylsilsesquioxane (PMS) modified by Hf‐ and Ti‐alkoxides. By varying the alkyl‐group of the employed Hf‐alkoxides, SiOC/HfO2‐based ceramic nanocomposites with different HfO2 polymorphs formed via thermal decomposition of the SSP under the same heat‐treatment conditions. Using PMS chemically modified by Hf(OnBu)4, tetragonal HfO2 phase was formed after the synthesis at 1100°C in Ar, whereas both, tetragonal and monoclinic HfO2 nanocrystals, were analyzed when replacing Hf(OnBu)4 by Hf(OiPr)4. After oxidation of the synthesized nanocomposites in air at 1500°C, a facile formation of oxidation‐resistant HfSiO4 (hafnon) phase occurred by the reaction of HfO2 nanocrystals with silica present in the SiOC nanocomposite matrix derived from Hf(OiPr)4‐modified SSPs. Moreover the amount of hafnon is dramatically increased by the additional modification of the polysiloxane with Ti‐alkoxides. In contrast, ceramic nanocomposites derived from Hf(OnBu)4‐modified SSPs, almost no HfSiO4 is detected after oxidation at 1500°C even though in the case of Ti‐alkoxide‐modified single‐source precursor.

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One‐dimensional (1D) hafnium carbide nanowires (HfCnws) were grown in situ on carbon fibers (CFs) via a Ni‐assisted pyrolysis method of organometallic polymer precursor. Scanning electron microscopy (SEM), transmission electron microscope (TEM), polarized‐light optical microscopy (PLM), and Raman were used to analyze the effect of HfCnws on the microstructure of pyrolytic carbon (PyC). The specific heat capacity (HC), thermal diffusivity (TD), thermal conductivity (TC), and coefficient of thermal expansion (CTE) of HfCnws‐C/C composites were also investigated. Results show that HfCnws wrapped by carbon nanosheet were successfully synthesized. The diameter of HfCnws is about 30 nm and the thickness of carbon nanosheet is about 10 nm, which could induce the formation of isotropic (ISO) PyC. After introducing HfCnws, the TD and CTE of HfCnws‐C/C composites were increased. Ni2HfCnws‐C/C composites show a higher TC and TD, and the CTE increased with the increasing content of HfCnws.

Ni-based coatings with nano-sized feedstock rare earth element (RE, La2O3) addition were produced by laser cladding. Bed of high energy ball milling mixed Ni60A and La2O3 powders were pre-placed onto the substrate 30CrMnSiNi2A before laser cladding. Results show that La segregates in inter dendrite and thus secondary dendrites growth and ripening are limited. The microstructure is refined. Top surface of the cladded coatings displays better refined microstructure which is caused by high La concentration, and this phenomenon is verified in EPMA results. The cracks and pores cannot be found in cladded coatings in which microstructure refinement and purifying effect caused by RE is clearly reflected in SEM microstructure, hardness and especially the wear resistance test results. The COF (coefficient of friction) of the coatings is apparently lower than that of substrate steel; the wear volume loss rate and the microhardness of coatings are less than 1/10 and about 4 times higher than that of substrate metal, respectively. This research forms the basement of metal surface anti-wear layer on the work surface of high speed heavy duty gear set in helicopter transform system.

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