Ultra-high temperature ceramic nanowires have offered increasing potential for thermal structural components. Herein, a novel single-crystal Hf_0.5Ta_0.5C solid solution nanowires were synthesized and incorporated with HfC coating, constructing a robust structure with Hf_0.5Ta_0.5C solid solution nanowires uniformly distributed and interconnected within the coating. The novel Hf_0.5Ta_0.5C solid solution nanowires could effectively hinder crack propagation through crack tip pinning and crack deflection. This mechanism substantially enhanced the elastic modulus and fracture toughness of HfC coating by 53.29 % and 59.67 %, respectively. The toughened HfC coating displayed superior fracture toughness and good interfacial binding strength with substrate to resist sever oxidation and scouring. Additionally, the high thermal conductivity of toughened HfC coating could promote the heat transmission that the coating sustained. Thus, in comparison to pure HfC coating, the toughened HfC coating displayed smaller mass and linear ablation rates of -0.35 mg·s^-1 and -0.46 μm·s^-1, which decreased by 39.66% and 36.98%, respectively. Our work not only simultaneously enhances the mechanical property and ablation resistance of HfC coated carbon/carbon composites, but also provides a novel prospect for advanced ultra-high temperature ceramic nanowires under extreme condition.

In recent years, high-entropy metal carbides (HECs) have attracted significant attention due to their exceptional physical and chemical properties. The combination of excellent performance exhibited by bulk HEC ceramics and distinctive geometric characteristics has paved the way for the emergence of one-dimensional (1D) HECs as novel materials with unique development potential. Herein, we successfully fabricated novel (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C nanowires derived via Fe-assisted single-sourced precursor pyrolysis. Prior to the synthesis of the nanowires, the composition and microstructure of (Ti,Zr,Hf,Nb,Ta)-containing precursor (PHECs) were analyzed, and divinylbenzene (DVB) was used to accelerate the conversion process of the precursor and contribute to the formation of HECs, which also provided a partial carbon source for the nanowire growth. Additionally, multi-branched, single-branched, and single-branched bending nanowires were synthesized by adjusting the ratio of PHECs to DVB. The obtained single-branched (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C nanowires possessed smooth surfaces with an average diameter of 130–150 nm and a length of several tens of micrometers, which were a single-crystal structure and typically grew along the [1 $\overline{1}$1] direction. Also, the growth of the (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C nanowires was in agreement with top-type vapor–liquid–solid mechanism. This work not only successfully achieved the fabrication of HEC nanowires by a catalyst-assisted polymer pyrolysis, but also provided a comprehensive analysis of the factors affecting their yield and morphology, highlighting the potential application of these attractive nano-materials.

Polymer-derived ultra-high-temperature ceramic (UHTC) nanocomposites have attracted growing attention due to the increasing demands for advanced thermal structure components in aerospace. Herein, hafnium carbide (HfC) whiskers are successfully fabricated in carbon fiber preforms via the polymer-derived ceramic (PDC) method. A novel carbon nanotube (CNT) template growth mechanism combined with the PDC method is proposed in this work, which is different from the conventional vapor–liquid–solid (VLS) mechanism that is commonly used for polymer-derived nanostructured ceramics. The CNTs are synthesized and proved to be the templates for fabricating the HfC whiskers, which are generated by the released low-molecular-weight gas such as CO, CO₂, and CH₄ during the pyrolysis of a Hf-containing precursor. The formed products are composed of inner single crystal HfC whiskers that are measured to be several tens of micrometers in length and 100–200 nm in diameter and outer HfC/HfO₂ particles. Our work not only proposes a new strategy to prepare the HfC whiskers, but also puts forward a new thinking of the efficient utilization of a UHTC polymer precursor.