石墨烯等纳米碳材料由于具有优异的力学性能被广泛用作金属基复合材料的理想增强体之一。然而，石墨烯与金属钛基体密度差异大且石墨烯片层之间较强的范德华力使其极易在基体中发生团聚，严重制约石墨烯/金属基复合材料的应用与发展。基于此，本文利用陶瓷颗粒(Al₂O₃)、有机溶剂(D400)对氧化石墨烯(GONs)改性，提升石墨烯在TC4基体中的分散能力，同时达到改性剂和石墨烯共同对复合材料的力学性能起到强化的目的。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)、热重分析仪(TGA)、X射线光电子能谱仪(XPS)表征两种改性方法所制备复合材料的粉末形貌、物相组成、微观组织、断口形貌等。此外，测试了复合材料的拉伸性能、硬度。论文主要获得以下结论：

  研究了不同沉淀温度对rGONs@Al₂O₃纳米粉末形貌、元素化学态的影响。结果表明：rGONs@Al₂O₃纳米粉末由21.6wt%的rGONs和78.4wt%Al₂O₃组成；在制备过程中，氧化石墨烯被还原成还原氧化石墨烯，氧化铝颗粒的数量随着沉淀温度的升高而减少，纳米粉末的最佳制备温度为60℃。

  研究了rGONs@Al₂O₃纳米粉末含量对钛基复合材料组织和性能的影响规律。结果表明：GONs@Al₂O₃/TC4复合材料中有氧化铝颗粒析出，晶粒得到了明显的细化；复合材料的强度随着rGONs@Al₂O₃纳米粉末含量的增加而提升，0.5rGONs@Al₂O₃/TC4复合材料的屈服强度为950.5MPa、抗拉强度为1022.5MPa，与纯TC4基体相比，分别提升了20.3%和17%。

  对比分析了GONs/TC4、D400/TC4、GOMs/TC4复合材料的组织演变及力学性能。结果表明：氧化石墨烯和聚醚胺形成的TiC形态存在差异，前者的TiC呈片状，后者的TiC呈微米级颗粒。0.3GOMs/TC4复合材料的屈服强度和抗拉强度分别为963.45MPa和1062.37MPa，延伸率为7.8%，实现了氧化石墨烯和聚醚胺共同强化TC4基体。GOMs/TC4复合材断口形貌中可以观察到大量的TiC颗粒，随着GOMs含量的增加，解理台阶变得更加明显。

  通过对比两种改性方法在钛基复合材料中的应用优劣性，可以看出改性是提高石墨烯在钛基体中的分散能力有效手段之一，同时可以实现改性剂和石墨烯共同强化钛合金基体。但是，相比陶瓷颗粒改性，有机溶剂改性石墨烯在高性能钛基复合材料制备和加工过程中具有更优的潜力。

  Carbon nanomaterials such as graphene are widely used as one of the ideal reinforcements for metal matrix composites due to their excellent mechanical properties. However, the large density difference between graphene and metal titanium matrix and the strong van der Waals force between graphene sheets make it easy to agglomerate in the matrix, which seriously restricts the application and development of graphene/metal matrix composites. Based on the above questions, this study uses ceramic particles (Al₂O₃) and organic solvent (D400) to modify graphene oxide (GONs) to improve the dispersion ability of graphene in TC4 matrix, and at the same time achieve the joint effect of modifier and graphene on graphene oxide. The powder morphology, phase composition, microstructure, fracture morphology, etc. of composites prepared by the two modified methods were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), thermogravimetric analyzer (TGA) and X-ray photoelectron spectroscopy (XPS). In addition, the tensile properties and hardness of the composites were tested. The main conclusions of the paper are as follows:

  The effects of different precipitation temperatures on the morphology and chemical state of the nanopowders were investigated. The results show that the rGONs@Al₂O₃ nanopowders are composed of 21.6wt% rGONs and 78.4wt% Al₂O₃; during the preparation process, the graphene oxides were reduced to reduced graphene oxides, the number of alumina particles decreased with the increase of the precipitation temperature, and the optimum preparation temperature of the nanopowder is 60 ℃.

  The effect of rGONs@Al₂O₃ nanopowders content on the microstructure and properties of titanium matrix composites were studied. Alumina particles were precipitated in the rGONs@Al₂O₃/TC4 composite, and the grains were obviously refined. The mechanical properties test results show that the yield strength and tensile strength of the 0.5rGONs@Al₂O₃/TC4 composite are 950.5 MPa and 1022.5 MPa , which are 20.3% and 17% higher than those of the pure TC4 matrix, respectively. The fracture mechanism of composites changed from original ductile fracture to mixed fracture.

  The microstructure evolution and mechanical properties of GONs/TC4, D400/TC4 and GOMs/TC4 composites were compared and analyzed. The study found that there are some differences in the morphology of TiC formed by graphene oxide and polyetheramine, the former TiC is in the form of flakes, and the latter is in the form of micron-sized particles. The yield strength and tensile strength of the 0.3GOMs/TC4 composite are 963.45 MPa and 1062.37 MPa, respectively, and the elongation is 7.8%, realizing the co-strengthening of the TC4 matrix by graphene oxide and polyetheramine. A large number of TiC particles can be observed in the fracture morphology of GOMs/TC4 composites, and with the increase of GOMs content, the cleavage steps become more obvious.

  The advantages and disadvantages of the two modification methods in the application of titanium matrix composites were compared, it can be seen that modification is one of the effective ways to improve the dispersion ability of graphene in the titanium matrix, and at the same time, the modifier and graphene can jointly strengthen the titanium alloy matrix. However, compared with ceramic particle modification, organic solvent modified graphene has better potential in the preparation and processing of high-performance titanium-based composites.

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