硼化锆基超高温陶瓷高温氧化实验表征及建模

发布时间：2018-05-09 18:42

本文选题：超高温陶瓷 + 高温测试　；参考：《重庆大学》2015年硕士论文

【摘要】：超高温陶瓷是一类熔点超高过3000?C材料的统称,主要由一些过渡金属的硼化物、碳化物和氮化物组成。其中,由于硼化锆所具备的超高的熔点、较低的密度、高热导率和电导率、高强度和弹性模量以及良好的物化稳定性等优异的综合性能,目前被认为是用作航空航天领域中新一代热防护材料的理想选择。但相对较弱的抗氧化性能一直是制约这种材料应用的关键问题之一。本文从测试设备研发、高温氧化实验和氧化理论建模三方面针对该材料的氧化特性开展研究。利用Zr B2基超高温陶瓷理想的电导率,基于电阻加热方法,建立了一套主要针对其氧化性能测试,计及电-热-力-磁等多物理场载荷作用的超高温测试系统。该测试系统具备最高加热温度不受限、温升率高、能源消耗少、实验效率高等优点,能够实时动态地测量被测试件的温度分布并观测记录材料高温氧化过程中的表面形貌。此外,该系统可施加拉伸、弯曲或拉弯组合等外载以研究外部应力对材料氧化性能的影响。基于自主开发的测试系统,针对添加Si C的Zr B2基超高温陶瓷材料进行高温氧化实验。在温升率测试中,实测最高温升率接近3900oC/s。电加热温升率影响因素分析表明,温升率会受到加载电流大小、温度、材料属性和试件尺寸等因素的影响。高温氧化测试表明,从升温开始直至被加热失效,氧化行为可分成三个特征较明显的阶段。利用实时动态温度场测量系统表征了不同阶段内被测试件沿长度方向的温度分布,同时分析了测量温度场与测试过程中被测试件表面形貌之间的联系。结合断口形貌与材料特性分析,对失效机理进行了解释。最后,针对单相Zr B2超高温陶瓷的氧化行为,通过细观力学、热力学等方法,建立了一个计及热-力-化学的多物理场耦合氧化模型。该模型考虑了氧化层与基体间结构的相互作用,可定量描述氧化层内应力状态与氧气扩散之间的关系。模型对于氧化参数的预测结果与实验结果取得了较好的吻合。对于模型的影响参数进行了深入地分析并给出了氧化层横向生长系数的合理取值。
[Abstract]:Ultra-high temperature ceramics (UHTCs) are a kind of material whose melting point is over 3000 C, which is mainly composed of boride, carbides and nitrides of some transition metals. Among them, zirconium boride has excellent comprehensive properties, such as high melting point, low density, high thermal conductivity and conductivity, high strength and elastic modulus, good physical and chemical stability, etc. At present, it is considered to be an ideal choice for the new generation of thermal protection materials in the field of aeronautics and astronautics. However, relatively weak oxidation resistance has been one of the key problems restricting the application of this material. In this paper, the oxidation characteristics of the material are studied from three aspects: research and development of test equipment, high temperature oxidation experiment and oxidation theory modeling. Using the ideal conductivity of ZrB2 based ultra-high temperature ceramics and based on the method of resistance heating, a set of ultra-high temperature measuring system was established, which mainly aimed at the oxidation performance of ZrB2 ceramics and considered the multi-physical field loads such as electric-thermal-force-magnetic. The system has the advantages of unlimited maximum heating temperature, high temperature rise rate, low energy consumption and high experimental efficiency. It can dynamically measure the temperature distribution and observe the surface morphology of the material during high temperature oxidation. In addition, the system can be used to study the effect of external stress on the oxidation properties of the material by external loads such as tensile, bending or tensile bending. Based on the test system developed by ourselves, the high temperature oxidation experiments were carried out for ZrB2 based ultra-high temperature ceramic materials added sic. In the temperature rise rate test, the measured maximum temperature rise rate is close to 3900oC / s. The analysis of the factors influencing the temperature rise rate of electric heating shows that the temperature rise rate is affected by the loading current, temperature, material properties and the size of the specimen. The high temperature oxidation test shows that the oxidation behavior can be divided into three stages with obvious characteristics from the beginning of heating up to the failure of heating. The temperature distribution along the length direction in different stages was characterized by a real-time dynamic temperature field measurement system, and the relationship between the measured temperature field and the surface morphology of the tested part was analyzed. The failure mechanism was explained by the analysis of fracture morphology and material properties. Finally, according to the oxidation behavior of single phase ZrB2 ultra-high temperature ceramics, a multi-physical field coupled oxidation model considering thermo-mechanical and chemical properties was established by means of micromechanics and thermodynamics. The model takes into account the interaction between the oxide layer and the matrix structure and can quantitatively describe the relationship between the stress state in the oxide layer and the oxygen diffusion. The prediction results of oxidation parameters obtained by the model are in good agreement with the experimental results. The influence parameters of the model are deeply analyzed and the reasonable values of the transverse growth coefficient of the oxide layer are given.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ174.12

【相似文献】