In this study, ZrB₂–25 vol% SiC composite containing 0, 2.5, 5, 7.5 and 10 wt% graphite nano-flakes were prepared by spark plasma sintering (SPS) process at 1900 °C for 7 min under 40 MPa. The fabricated composite samples were compared to examine the influences of nano-graphite content on the densification, microstructure and mechanical properties of ZrB₂–SiC-based ultrahigh temperature ceramics. Fully dense composites were obtained by adding 0–5 wt% nano-graphite, but higher amounts of additive led to a small drop in the sintered density. The growth of ZrB₂ grains was moderately hindered by adding nano-graphite but independent of its content. The hardness linearly decreased from 19.5 for the graphite-free ceramic to 12.1 GPa for the sample doped with 10 wt% nano-graphite. Addition of graphite nano-flakes increased the fracture toughness of composites as a value of 8.2 MPa m^½ was achieved by adding 7.5 wt% nano-graphite, twice higher than that measured for the graphite-free sample (4.3 MPa m^½). The in-situ formation of ZrC and B₄C nano-particles as well as the presence of unreacted graphite nano-flakes led to a remarkable enhancement in fracture toughness through activating several toughening mechanisms such as crack deflection, crack bridging, crack branching and graphite pullout.

在本研究中，通过火花等离子体烧结（SPS）在1900°C下于40 MPa下进行7分钟，制备了含量为0、2.5、5、7.5和10 wt％的石墨纳米片的ZrB ₂ –25 vol％SiC复合材料。比较制成的复合材料样品，以检查纳米石墨含量对ZrB ₂ -SiC基超高温陶瓷的致密化，微观结构和力学性能的影响。通过添加0-5 wt％的纳米石墨可以获得完全致密的复合材料，但添加剂的添加量较大，导致烧结密度有小幅下降。ZrB ₂的生长纳米石墨的加入可适度地阻碍晶粒的生长，但其含量不受其影响。硬度从无石墨陶瓷的19.5线性降低到掺有10 wt％纳米石墨的样品的12.1 GPa。石墨纳米薄片的添加增加了复合材料的断裂韧性，因为通过添加7.5 wt％的纳米石墨获得了8.2 MPa ^m½的值，是无石墨样品（4.3 MPa ^m½）的两倍。ZrC和B ₄ C纳米粒子的原位形成以及未反应的石墨纳米薄片的存在通过激活多种增韧机制（例如裂纹偏转，裂纹桥接，裂纹分支和石墨）导致断裂韧性显着提高。拔出。