本文關(guān)鍵詞： 稀土鉭酸鹽陶瓷塊體 稀土鉭酸鹽涂層 熱擴散系數(shù) 熱導率 硬度　出處：《昆明理工大學》2017年碩士論文　論文類型：學位論文

【摘要】：熱障陶瓷涂層材料在航空航天、交通和大型火力發(fā)電等領(lǐng)域有廣泛而重要的應用,對熱障陶瓷涂層在高溫下的使用提出了更高的要求,為了解決熱障陶瓷涂層熱導率低,相穩(wěn)定性差等問題,本實驗采用鉭酸釔,鑭系稀土鉭酸鹽作為新的候選材料,以期在降低熱導率的同時還具有較好的高溫力學性能。采用固相法制備鑭系稀土鉭酸鹽陶瓷塊體,粒徑在2～14μm,氣孔率在4%～9%之間,其中 NdTaO4,EuTaO4,DyTaO4,GdTaO4 和 ErTaO4 屬于 m 相,YbTaO4和LuTaO4屬于m'相。由于熱效應導致的體積膨脹和聲子散射,稀土鉭酸鹽陶瓷塊體的熱容(0.3J/k.mol～0.46J/k.mol)低于7-8YSZ。熱擴散系數(shù)(0.38mm2/s～1.3mm2/s)和熱導率(0.3J/k·mol～0.46W·m-1·k-1)在低溫下呈線性下降,高溫下由于熱輻射的作用光子的熱導不容忽視,熱導率下降平緩并趨于一個較小值,當溫度為800℃時,DyTaO4有最低的熱導率1．38W·m-1·K-1 NdTaO4的熱導率(1.41W·m-1·K-1)和DyTaO4是比較接近的,同時,稀土鉭酸鹽陶瓷塊體的熱擴散系數(shù)和熱導率隨著氣孔率的升高而降低。在低溫時,單斜m相有最低的能量,因而是低溫穩(wěn)定結(jié)構(gòu);當溫度升高到1430℃以上時,四方相t有最低的能量,最為穩(wěn)定。實驗測得稀土鉭酸鹽陶瓷塊體的顯微硬度值在504HV～641HV之間,結(jié)合掃描電鏡(SEM)圖譜發(fā)現(xiàn),在氣孔和晶界處可能隱藏著局部的變形有助于提高材料的硬度值。選擇較好化學穩(wěn)定性和熱穩(wěn)定性的鉭酸釔(YTaO4)粉體造粒后,采用大氣等離子噴涂技術(shù),在45鋼基體上噴涂制備厚度為1.2mm左右的YTaO4熱障涂層。當溫度升高到700℃以后,由于光子的傳熱機制作用增大,氣孔的燒結(jié)和縮聚,使涂層熱擴散系數(shù)和熱導率上升。鉭酸釔熱障陶瓷涂層的平均顯微硬度值為498HV,低于鉭酸釔陶瓷塊體(520HV)的硬度值,與鉭酸釔陶瓷塊體相比,涂層比較粗糙,涂層間顆粒間距較大,孔隙率較高,導致涂層材料低于鉭酸釔陶瓷塊體的顯微硬度值。
[Abstract]:Thermal barrier ceramic coating materials have been widely used in aerospace, transportation and large scale thermal power generation fields. The application of thermal barrier ceramic coatings at high temperature has put forward higher requirements, in order to solve the problem of low thermal conductivity of thermal barrier ceramic coatings. The phase stability is poor. In this experiment, yttrium tantalate and lanthanide rare earth tantalate are used as new candidate materials, in order to reduce thermal conductivity and have better mechanical properties at high temperature, lanthanide rare-earth tantalate ceramic blocks were prepared by solid phase method. The particle size is 2 ~ 14 渭 m and the porosity is between 4% and 9%. Among them, NdTaO4, EuTaO4DyTaO4Dy TaO4DTAO4 and ErTaO4 belong to m phase YbTaO4 and LuTaO4 belong to m phase. Volume expansion and phonon scattering due to thermal effect, The thermal capacity of rare-earth tantalate ceramic blocks is 0.3J / k.mol0.46J / k.mol. the thermal diffusivity is lower than 7-8YSZ. the thermal diffusivity is 0.38mm2s1.3mm2s) and the thermal conductivity is 0.3J / k 路mol~0.46W 路m-1 路k-1). At low temperature, the thermal conductivity of photons due to thermal radiation can not be ignored, and the thermal conductivity decreases slowly and tends to a smaller value. When the temperature is 800 鈩，

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