【作者】 李冰；

【导师】 刘金铃；

【作者基本信息】 西南交通大学 ， 力学， 2024， 硕士

【摘要】 随着航空航天科技的快速发展,超高温陶瓷材料在制造空天飞行器的关键部件中扮演着越来越重要的角色。ZrB₂因其出色的高熔点、高强度、高硬度以及良好的导热性能,受到了广泛关注。然而,ZrB₂的低断裂韧性和可靠性问题一直制约着其应用。因此,ZrB₂陶瓷材料的强韧化问题成为研究的重点。过去的研究大多围绕在陶瓷中弥散分布增韧相来改善ZrB₂陶瓷的脆性。近年来,仿生设计的策略在提升陶瓷韧性方面展现出了良好效果,受到了广泛关注。本文以ZrB₂基超高温陶瓷为研究对象,通过振荡热压烧结制备了ZrB₂、ZrB₂-SiC和ZrB₂-SiC（G）超高温陶瓷,表征了其显微结构特征,测试了其力学性能,并对其增韧机制进行了分析。主要工作如下:（1）研究了烧结温度、保温时间和振荡压力参数对ZrB₂陶瓷的微观结构和力学性能的影响。发现工艺参数对陶瓷的微观结构和力学性能具有显著影响,通过优化烧结工艺参数,可以有效提升ZrB₂陶瓷的致密度和力学性能。采用适中振荡压力,1800℃烧结60 min所制备的ZrB₂陶瓷具有最优的综合性能。该条件下,制备得到的陶瓷材料孔洞较少,致密度较高,晶粒尺寸适中,弯曲强度和维氏硬度分别达到655 MPa和17.7GPa。（2）研究了振荡压力对ZrB₂-SiC超高温陶瓷微观结构和力学性能的影响,同时,通过粉末铺层和流延叠层技术制备了层状ZrB₂-SiC陶瓷,并探讨了不同层厚和层数下层状ZS20/ZS30陶瓷的力学性能及其增韧机制。研究结果显示,SiC对ZrB₂陶瓷起到了增强增韧的效果,适当的振荡压力也可显著提升ZrB₂-SiC陶瓷的烧结密度和界面结合强度,进而增强其硬度和断裂韧性。层状结构可以使裂纹发生偏转,有效阻碍裂纹扩展,而且流延制备的层状陶瓷的断裂韧性随层数比的增加先增后减,在层数比为3:1时达到最优,为5.33 MPa·m^1/2。（3）研究了仿生结构ZrB₂-SiC（G）超高温陶瓷的制备、力学性能和增韧机制。通过流延成型和热压烧结制备了具有不同层数比的ZS20（G）/ZS30（G）陶瓷,其表面致密无孔隙,石墨相分布均匀。在断裂过程中,石墨相出现拔出行为,消耗了能量。单边V型切口梁（SEVNB）测试得到的载荷–位移曲线表明,具有仿生结构的ZrB₂-SiC（G）超高温陶瓷表现出与普通陶瓷材料测试规律完全不同的台阶式下降特征。此外,研究还发现石墨相的加入可以提升材料的抗热冲击性能。更多还原

【Abstract】 With the rapid development of aerospace science and technology,ultra-high temperature ceramic materials are playing an increasingly significant role in the manufacture of key components for aerospace vehicles.ZrB₂ has garnered widespread attention due to its high melting point,strength,hardness,as well as excellent,thermal conductivity.However,the low fracture toughness and reliability issues of ZrB₂ have been limiting its applications.Thus,the strengthening and toughening of ZrB₂ ceramic materials have become a focal point of research.Previous studies mainly focused on improving the brittleness of ZrB₂ ceramics by dispersing toughening phases within the ceramic.In recent years,bioinspired design strategies have demonstrated remarkable effects in enhancing ceramics’toughness,attracting much attention.This thesis takes ZrB₂-based ultra-high temperature ceramics as the research object.ZrB₂,ZrB₂-SiC and ZrB₂-SiC（G）ultra-high temperature ceramic materials were prepared by hot oscillatory pressing sintering.Their microstructural features were characterized,mechanical properties were tested,and their toughening mechanisms were analyzed.The main work is as follows:（1）The effects of sintering temperature,holding time,and oscillatory pressure on the microstructure and mechanical properties of ZrB₂ ceramics were investigated.It was found that the processing parameters have a significant impact on the microstructure and mechanical properties of the ceramics.By optimizing the sintering process parameters,the density and mechanical properties of ZrB₂ ceramics can be effectively improved.ZrB₂ ceramics prepared at a moderate oscillatory pressure,sintered at 1800℃for 60 minutes,exhibited optimal overall performance.Under this conditions,the prepared ceramic material had fewer voids,higher density,moderate grain size,and achieved a flexural strength and Vickers hardness of655 MPa and 17.7 GPa,respectively.（2）The influence of oscillatory pressure on the microstructure and mechanical properties of ZrB₂-SiC ultra-high temperature ceramics was studied.Meanwhile,laminated ceramics were prepared using powder stacking and tape casting techniques.Additionally,the mechanical properties and toughening mechanisms of laminated ZS20/ZS30 ceramics with different layers’thicknesses and numbers of different layers were explored.The results showed that SiC can enhance the strength and toughness of ZrB₂ ceramics.Appropriate oscillatory pressure can significantly improve the sintering density and interfacial bonding strength of ZrB₂-SiC ceramics,thereby increasing their hardness and fracture toughness.It was discovered that the laminated structure can deflect cracks,effectively impeding crack propagation.Furthermore,the fracture toughness of laminated ceramics prepared through tape casting increases first and then decreases with the increase of the layer ratio,reaching an optimum value of 5.33 MPa·m^1/2 at a layer ratio of 3:1.（3）This thesis also investigates the preparation,mechanical properties,and toughening mechanisms of bionic structured ZrB₂-SiC（G）ultra-high temperature ceramics.ZS20（G）/ZS30（G）ceramics with different layer ratios were prepared through tape casting and hot pressing sintering.The surface of the ceramics was dense and pore-free,with a uniform distribution of graphite phases.During fracture process,the graphite phase exhibited pull-out behavior,consuming energy.The load-displacement curves obtained from the Single Edge V-Notched Beam（SEVNB）test indicated that the bio-structured ZrB₂-SiC（G）ultra-high temperature ceramics exhibited a stepped decline characteristic,which was completely different from ordinary ceramic materials.Additionally,the study found that the addition of graphite can improve the material’s thermal shock resistance.更多还原