Carbon/carbon composites with higher mechanical strength and better reliability at elevated temperatures are urgently needed to satisfy the practical applications requirements. SiC nanowires (SiCNWs) modified C/C (SC-CC) composites have attracted an abundance of attention for their excellent mechanical performance. To further boost the mechanical strengths of composites and maximize the reinforcing efficiency of SiCNWs, we introduce orthogonally structured graphene nanosheets (OGNs) into SC-CC composites, in which OGNs are grafted on the SiCNWs via chemical vapor deposition (CVD) method, forming SC-G-CC composites. Benefiting from the nano-interface effects, uniform stress distribution, strong SiCNWs/PyC interfacial bonding and elevated stress propagation efficiency in the PyC matrix are achieved, thus SC-G-CC composites accomplish brilliant mechanical properties before and after 1,600 °C heat treatment. As temperature rises to 2,100 °C, SiCNWs lose efficacy, whereas OGNs with excellent thermal stability continue to play the nano-interface role in the PyC matrix. Therefore, SC-G-CC composites show better mechanical performance after 2,100 °C heat treatment, and the mechanical strength retention rate (MSR) of interlaminar shear strength, out-of-plane and in-plane compressive strength of SC-G-CC composites reach 61.0%, 55.7% and 55.3%, respectively. This work proposes an alternative thought for maximizing the potentiality of nanomaterials and edifies the mechanical modification of composites.

For the inadequate interlaminar strength of 2D carbon/carbon (C/C) composite, in-situ grown carbon nanotubes (CNTs) reinforcing strategy was put forward to strengthen the interlaminar matrix at the nanoscale and inhibit the interlaminar cracking. CNT morphology is an essential factor in influencing the enhancement effect. Herein, the influence of in-situ grown CNT morphology on the microstructure and mechanical properties of C/C composite was deeply studied. The radially-aligned straight CNTs could induce the formation of highly-ordered pyrolytic carbon (PyC), while PyC in randomly-distributed curved CNTs concentrated area exhibits an isotropic structure. Further, radially-aligned straight CNTs show better improvement on the flexural and shear strength of C/C composites. According to the fine structural characterization and finite element simulation, the influence mechanism of CNT morphology was revealed. CNT morphology can influence the stress distribution in the PyC protective layer, and compared with radially-aligned straight CNTs, randomly-distributed curved CNTs induce higher tensile stress in the PyC protective layer, which has a detrimental impact on the flexural and shear properties of C/C composite. This work provides novel insights into the effect of CNT morphology on the microstructure and mechanical properties of C/C composites, which gives a basis for the structural design and preparation of CNTs reinforced C/C composites.

Stealth materials with high dependability at elevated temperatures and outstanding mechanical properties are urgently needed for practical applications. As one-dimensional ultrahigh temperature ceramic (UHTC) materials, zirconium carbide whiskers (ZrCw) have attracted a great deal of attention due to their desirable mechanical and ablation resistance performance in high-temperature environments. We have successfully synthesized ZrCw using a carbothermal reduction technique without the introduction of metal catalytic in this paper. ZrCw shows a typically prismatic structure with the diameter of 1–2 μm and the aspect ratio of up to 250. The growth of ZrCw is controlled by a solid-liquid-solid (SLS) and vapor-solid (VS) compound mechanism in conjunction with the auxiliary action of mesophase Na₃ZrF₇. The ZrCw/paraffin hybrids achieve the minimum reflection loss (R_L(min)) of −25.77 dB at 13.28 GHz under the thickness of 1.25 mm, and reach an effective absorption bandwidth (EAB) of 3.04 GHz (14.96–18.00 GHz) with a thickness of only 1.0 mm. This work presents a promising approach for large-scale producing high-purity whiskers, and verifies that ZrCw has extensive application prospects in the field of stealth materials.