【作者】 周卫兵；

【导师】 梅炳初；

【作者基本信息】 武汉理工大学 ， 材料学， 2006， 博士

【摘要】 新型三元层状碳化物Ti₂AlC和Ti₂AlC₂由于其优异的性能而受到材料科学工作者的广泛重视。由于综合了金属和陶瓷的诸多优良性能，它们同金属一样，在常温下，有很好的导热性能和导电性能，相对较低的Vickers硬度和较高的弹性模量，在常温下有延展性。同时，它具有陶瓷材料的性能，有高的屈服强度、高熔点、高热稳定性和良好的抗氧化性能，在高温下能保持高强度。而更为重要的是，它不同于传统碳化物陶瓷，可以象金属一样，用传统的加工方式进行加工，并具有比二硫化钼和石墨更低的超低磨擦系数和优良的自润滑性能。这些优异性能使其具有广阔的应用前景，并成为新材料研究中重要对象。由于Ti₂Al_C和Ti₃AlC₂的硬度相对较软（3-5GPa）以及低的蠕变强度，极大地限制了作为高温结构材料的使用。TiB₂由于较高的硬度和高的弹性模量，优异的化学稳定性，具有同Ti₂AlC和Ti₃AlC₂接近的导热系数，因此在本论文中，通过引入TiB₂颗粒来改善Ti₂AlC和Ti₃AlC₂材料的硬度和强度。分别研究了放电等离子烧结和热压烧结两种工艺合成Ti₂AlC-TiB₂和Ti₃AlC₂-TiB₂复合材料的制备过程；并研究了合成材料的反应机理、显微结构特征和物理性能。 开展了热压法制备致密Ti₂AlC-TiB₂和Ti₃AlC₂-TiB₂复合材料的研究。在Ti₂AlC-TiB₂的制备过程中，分别探索了两种不同起始原料组成Ti／TiC／Al和TiC／Ti／B₄C／Al，以及引入不同体积TiB₂对反应合成影响规律。在Ti₃AlC₂-TiB₂复合材料的制备过程中，重点研究了硅用作合成助剂时，引入不同体积TiB₂对反应合成影响规律。经X-射线衍射、扫描电镜、能谱仪等表征方法对烧结产物的相组成和显微结构进行了研究。结果表明：在起始原料Ti／TiC／Al中直接掺加TiB₂时，很难合成杂质较少的Ti₂AlC-TiB₂复合材料，而以起始原料TiC／Ti／B₄C／Al，通过原位合成方法，1400℃和30MPa条件下能够合成5-25％TiB₂的致密Ti₂AlC-TiB₂复合材料，铝在合成中容易挥发，需要掺加0.05mol的铝，过高的Al量和过高的温度不利于Ti₂AlC的生成。1350℃和30MPa条件下，热压2TiC／Ti／Al／0.2Si／TiB₂可得到5-20％TiB₂的Ti₃AlC₂-TiB₂复合材料。硅的掺加能明显促进Ti₃AlC₂的反应合成，引入过高的TiB₂，能明显影响Ti₃AlC₂-TiB₂复合材料的合成，通过原位法合成Ti₃AlC₂-TiB₂复合材料时，引人TiB₂的量不能超过10％。 应用放电等离子烧结工艺研究了Ti₂AlC-TiB₂和Ti₃AlC₂-TiB₂复合材料的反应合成。应用X-射线衍射、扫描电镜结合能谱仪研究不同起始组成粉料在不同更多还原

【Abstract】 New layered ternary Ti₂AlC and Ti₃AlC₂ attract increasing interest owing to their unique properties. Ti₂AlC and Ti₃AlC₂ combine unusual properties of both metals and ceramics. Like metals, it is a good thermal and electrical conductor, relatively soft. Like ceramics, it is elastically stiff; exhibit excellent high temperature mechanical properties. It is resistant to thermal shock and unusually damage tolerant, and exhibit excellent corrosion resistance. Above all, unlike conventional carbides, they can be machined by using conventional tools without lubricant, which is of great technological importance for their application. Additionally, Ti₂AlC and Ti₃AlC₂ is an exceptional solid lubricant with an ultra-friction. These excellent properties mentioned above make them another family of technically important materials. Unfortunately, there are relatively soft （3-5GPa） and low creep strength, limit the potential application of as a high-temperature structural material. Incorporation of second phase is an effective way to overcome these weaknesses. Owing to the high hardness, high modulus, excellent chemical stability, and approximate thermal expansion coefficient, TiB₂ herein is chosen to produce Ti-Al-C/TiB₂ composites to increase the hardness and strength of Ti₂AlC and Ti₃AlC₂. Both spark plasma sintering and hot pressing were utilized for the synthesis of Ti₂AlC-TiB₂ and Ti₃AlC₂-TiB₂composites. Also, the microstructures, the physical properties as well as reaction mechanism of the obtained materials were investigated, respectively.In chapter 2, the synthesis of Ti₂AlC-TiB₂ and Ti₃AlC₂-TiB₂ composites were conducted by HP method. For the synthesis of Ti₂AlC-TiB₂ composite, two kinds of powder mixtures Ti/TiC/Al and TiC/Ti/B4C/Al were used. Additionally, different TiB₂ content was incorporated to explore the synthesis rule of Ti₂AlC-TiB₂ composite. Also, for the synthesis of Ti₃AlC₂-TiB₂ composite, when silicon was chosen as the synthesis additive, the effect of different TiB₂ content on the synthesis rule were specially studied Characterized by XRD, SEM and EDS, the results indicated that direct addition of TiB₂ in the starting mixtures Ti/TiC/Al lead to the fabrication Ti₂AlC-TiB₂ composite with impurity. Dense Ti₂AlC-TiB₂ composite （5-25%TiB₂） can be obtained by sintering TiC/Ti/B4C/Al mixture at 1400 ℃ with a pressure of 30 MPa in argon atmosphere, Al may easily vapor, it needs exceeds 0.05mol during the whole reaction. However, too much Al and higher temperature may not be in favor of forming Ti₂AlC. Dense Ti₃AlC₂ has been sintered by hot pressing with the start molar ratio2TiC/Ti/Al/0.2Si/TiB₂ at 1350 ℃ with a pressure of 30MPa in argon atmosphere. The additive Si accelerates the reaction synthesis and favors the crystal growth of Ti₃AlC₂.Incoporation of too much TiB₂ content can influence the reaction of Ti₃AlC₂.Through in-situ synthesis, addition of TiB₂ can not exceed 10vol%.In chapter 3, SPS was used to synthesize Ti₂AlC-TiB₂ and Ti₃AlC₂-TiB₂ composites X-ray diffraction （XRD） and scanning electron microscope （SEM）更多还原