放电等离子烧结石墨烯增韧氧化锆陶瓷基复合材料力学性能研究

发布时间：2018-05-13 11:08

本文选题：石墨烯 + 氧化锆　；参考：《苏州大学》2015年硕士论文

【摘要】：氧化锆陶瓷材料具有十分优异测化学、物理性能。其在室温下具有较好的力学性能,而且其抗高温、耐化学腐蚀性较好,是一种非常有应用前景的高温陶瓷。然而,由于陶瓷自身的本征脆性及其本征脆性导致的较差的摩擦磨损性能,很大程度制约了其更广泛的应用。针对上述问题,发展氧化锆陶瓷复合材料被公认为是一种行之有效的方法。本论文基于多层石墨烯纳米片(GNS)优异的力学性能,提出了石墨烯纳米片增韧5mol.%氧化钇稳定氧化锆(TZP)复合材料的研究思路。为确保复合材料中GNS的均匀分布,采用了超声混合结合表面活性剂分散的方法制得了GNS/TZP复合材料粉末(其中,GNS的含量分别为0wt.%,0.5wt.%,0.75wt.%和1.0wt.%),利用放电等离子烧结(spark plasma sintering,SPS)技术制备GNS/TZP复合材料,并对所制备的样品进行了物相表征,显微组织结构分析及相关力学性能如弹性模量、显微硬度、断裂韧性及摩擦磨损性能评价。采用X射线衍射和拉曼光谱进一步研究了放电等离子(SPS)烧结复合材料的物相组成,结果表明TZP在高温烧结中没有相变,依然保持其四方晶体结构,并且GNS在高温高压烧结条件下可保持其固有结构。通过冷场发射扫描电镜(SEM),对材料显微组织/形貌观察发现,GNS在复合材料中分布较为均匀,且复合材料中晶粒得到了显著细化,这主要得益于石墨烯纳米片优异的传热性能。使用仪器化微纳压入设备和显微硬度计测试研究了氧化锆及GNS/TZP复合材料的力学性能(如显微硬度、弹性模量和断裂韧性),并使用仪器化划入技术研究了复合材料的摩擦莫寻在材料表面进行划入实验,得出划入残余深度和TZP在不同GNS添加量下的摩擦系数。使用SEM观察材料断面,压痕、划痕形貌和压入、划入产生的裂纹形貌。再由以上结果分析复合材料的增韧机制和摩擦磨损性能。研究结果表明,与未添加GNSs的TZP相比,0.5wt%GNS/TZP弹性模量较TZP提升了~20%,显微硬度增加了~12%,断裂韧性提高了~36%(从4.1MPa m0.5提升到5.6MPa m0.5).。研究发现GNS/TZP复合材料主要增韧机制是石墨烯的拔出,桥接,裂纹的偏转和裂纹的分叉。采用已有模型计算了复合材料界面在应力,并得出了GNS的临界增韧长度。计算了GNS的拔出应力释放率和复合材料的残余热应力,结果表明残余热应力对于复合材料的力学性能影响可以忽略。仪器化划入测试结果表明,尽管GNS/TZP复合材料的摩擦系数高于TZP,但纯TZP材料在仪器化划入过程中的损伤机制主要表现为脆性断裂,而GNS/TZP复合材料则转变为粘着磨损为主、脆性断裂为辅的损伤机制,这主要源于GNS/TZP复合材料断裂韧性的显著改善。
[Abstract]:Zirconia ceramic materials have excellent chemical and physical properties. It has good mechanical properties at room temperature, and its resistance to high temperature and chemical corrosion is better. It is a kind of high temperature ceramics with great application prospect. However, due to the intrinsic brittleness of ceramics and the poor friction and wear properties due to the intrinsic brittleness, its wider application is restricted to a great extent. To solve the above problems, the development of zirconia ceramic composites is recognized as an effective method. Based on the excellent mechanical properties of multilayer graphene nanocrystalline (GNS), a new method for the study of 5 mol.% yttrium oxide stabilized zirconia (TZP) composite toughened by graphene nanocrystalline was proposed in this paper. To ensure the uniform distribution of GNS in composites, GNS/TZP composite powder was prepared by ultrasonic mixing combined with surfactant dispersion method. The content of GNS/TZP composite powder was 0 wt. 0. 5 wt.g. 0. 75 wt.% and 1. 0 wt. respectively. Spark plasma sintering (Spark plasma interingling) was used to prepare GNS/TZP composite. The microstructure and mechanical properties such as modulus of elasticity, microhardness, fracture toughness and friction and wear properties of the samples were analyzed. The phase composition of SPS sintered composites was further studied by X-ray diffraction and Raman spectroscopy. The results showed that TZP had no phase transition during high temperature sintering and maintained its tetragonal crystal structure. And GNS can keep its inherent structure under high temperature and high pressure sintering condition. By means of cold field emission scanning electron microscopy (SEM), the microstructure / morphology of the composites was observed. It was found that the GNS distributed uniformly in the composites, and the grains in the composites were significantly refined, which was mainly due to the excellent heat transfer properties of graphene nanoparticles. The mechanical properties (such as microhardness) of zirconia and GNS/TZP composites were studied by instrumentation and microhardness tester. The elastic modulus and fracture toughness of the composites were studied by means of instrumented scratch technique. The friction coefficient of TZP and the residual depth of scratching on the surface of the composite were obtained. SEM was used to observe the fracture profile, indentation, scratch morphology and crack morphology caused by indentation and indentation. Then, the toughening mechanism and friction and wear properties of the composites were analyzed based on the above results. The results show that compared with TZP without GNSs, the elastic modulus of 0.5 w / t GNS / TZP is 20% higher than that of TZP, the microhardness is increased by 12%, and the fracture toughness is increased by 36% (from 4.1MPa m 0.5 to 5.6MPa m 0.5 路). It is found that the main toughening mechanisms of GNS/TZP composites are the drawing of graphene, bridging, crack deflection and crack bifurcation. The stress at the interface of the composite is calculated by using the existing model, and the critical toughening length of GNS is obtained. The pull-out stress release rate of GNS and the residual thermal stress of the composite are calculated. The results show that the influence of residual thermal stress on the mechanical properties of the composite can be neglected. The results of instrumentation scratch test show that although the friction coefficient of GNS/TZP composite is higher than that of TZP, the damage mechanism of pure TZP material during instrumentation is mainly brittle fracture, while that of GNS/TZP composite is mainly adhesive wear. The damage mechanism of brittle fracture is mainly due to the remarkable improvement of fracture toughness of GNS/TZP composites.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332

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