本文選題：超高溫陶瓷 + 高溫測試��； 參考：《重慶大學》2015年碩士論文

【摘要】：超高溫陶瓷是一類熔點超高過3000?C材料的統(tǒng)稱,主要由一些過渡金屬的硼化物、碳化物和氮化物組成。其中,由于硼化鋯所具備的超高的熔點、較低的密度、高熱導率和電導率、高強度和彈性模量以及良好的物化穩(wěn)定性等優(yōu)異的綜合性能,目前被認為是用作航空航天領(lǐng)域中新一代熱防護材料的理想選擇。但相對較弱的抗氧化性能一直是制約這種材料應用的關(guān)鍵問題之一。本文從測試設(shè)備研發(fā)、高溫氧化實驗和氧化理論建模三方面針對該材料的氧化特性開展研究。利用Zr B2基超高溫陶瓷理想的電導率,基于電阻加熱方法,建立了一套主要針對其氧化性能測試,計及電-熱-力-磁等多物理場載荷作用的超高溫測試系統(tǒng)。該測試系統(tǒng)具備最高加熱溫度不受限、溫升率高、能源消耗少、實驗效率高等優(yōu)點,能夠?qū)崟r動態(tài)地測量被測試件的溫度分布并觀測記錄材料高溫氧化過程中的表面形貌。此外,該系統(tǒng)可施加拉伸、彎曲或拉彎組合等外載以研究外部應力對材料氧化性能的影響�；谧灾鏖_發(fā)的測試系統(tǒng),針對添加Si C的Zr B2基超高溫陶瓷材料進行高溫氧化實驗。在溫升率測試中,實測最高溫升率接近3900oC/s。電加熱溫升率影響因素分析表明,溫升率會受到加載電流大小、溫度、材料屬性和試件尺寸等因素的影響。高溫氧化測試表明,從升溫開始直至被加熱失效,氧化行為可分成三個特征較明顯的階段。利用實時動態(tài)溫度場測量系統(tǒng)表征了不同階段內(nèi)被測試件沿長度方向的溫度分布,同時分析了測量溫度場與測試過程中被測試件表面形貌之間的聯(lián)系。結(jié)合斷口形貌與材料特性分析,對失效機理進行了解釋。最后,針對單相Zr B2超高溫陶瓷的氧化行為,通過細觀力學、熱力學等方法,建立了一個計及熱-力-化學的多物理場耦合氧化模型。該模型考慮了氧化層與基體間結(jié)構(gòu)的相互作用,可定量描述氧化層內(nèi)應力狀態(tài)與氧氣擴散之間的關(guān)系。模型對于氧化參數(shù)的預測結(jié)果與實驗結(jié)果取得了較好的吻合。對于模型的影響參數(shù)進行了深入地分析并給出了氧化層橫向生長系數(shù)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.
【學位授予單位】：重慶大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ174.12

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