La2(Zr0.7Ce0.3)2O7固相合成行为及热物理性能

采用固相合成制备了热障涂层陶瓷材料La2(Zr0.7Ce0.3)2O7(LZ7C3)。通过差热分析、X射线衍射等分析方法对固相合成行为影响因素进行研究,并用激光脉冲法和高温膨胀仪测试了LZ7C3粉末的热扩散系数和热膨胀系数。结果表明:完全合成LZ7C3的温度至少1400℃,煅烧时间至少5 h,反应粉末的粒度为0.82μm时,合成的LZ7C3粉末X射线衍射图谱没有La2 O3残留峰,其La∶Zr∶Ce为50.09∶35.12∶14.79,非常接近理论原子比例10∶7∶3;LZ7C3的热导率在1200℃时为0.79 W.m-1.K-1,热膨胀系数在1200℃时为11.6×10-6K-1,从室温到1200℃的加热过程中没有失重和相变发生,具有较高的相稳定性。     

SUS301L不锈钢激光焊接头疲劳损伤行为研究

研究SUSS301L不锈钢激光焊搭接接头的疲劳性能,并获得相应的S-N曲线及条件疲劳极限,通过宏观断裂形貌和疲劳断口分析,探讨SUSS301L不锈钢激光焊搭接接头的疲劳断裂模式与损伤行为。结果表明:SUSS301L不锈钢激光焊搭接接头失效概率为1.0%和0.1%的疲劳极限最大力分别为2.22、2.08 kN;通过有限元模拟分析得出,板材加载端的焊缝连接处是应力集中强烈部位,疲劳裂纹从该区域萌生并扩展;根据加载疲劳应力的大小,焊接接头在最终的断裂模式出现低应力疲劳断裂与高应力疲劳断裂两种模式,低应力疲劳断裂典型特征为"穿板断裂",而高应力疲劳断裂表现为"穿板+穿缝"特征。     

稀土锆酸盐热障涂层材料研究进展

稀土锆酸盐是最有希望应用于未来高性能航空发动机的热障涂层材料之一。归纳了国内外研究者在稀土锆酸盐类陶瓷材料上取得的结果,系统分析了不同位置全取代或部分取代得到的掺杂陶瓷材料的热物理性能和力学性能,并讨论了热障涂层材料研究的发展趋势,最后指出了稀土高酸盐热障涂层材料需要进一步研究的关键问题。     

Synthesis kinetics and thermophysical properties of La_2（Zr_（0.7）Ce_（0.3））_2O_7 ceramic for thermal barrier coatings

La2(Zr0.7Ce0.3)2O7 (LZ7C3) ceramic was synthesized by solid state reaction with La2O3, ZrO2 and CeO2 as starting materials. The synthesis kinetics, phase structure, mass loss and microstructure were studied by thermo gravimetric-different thermal analyzer (TG-DTA), X-ray difference (XRD) and scanning electron microscopy (SEM). The thermal conductivity and thermal expansion coefficient were measured by laser-flash method and pushing-rod method, respectively. XRD results showed that LZ7C3 was a mixture of La2Zr2O7 (LZ, pyro- chlore) and La2Ce2O7 (LC, fluorite). The lowest synthesis temperature and time of LZ7C3 were 1400 oC and 5 h. There were no peaks of La2O3 when the powder granularity was about 0.82 μm in the synthesis process. The atom ratio La:Zr:Ce of prepared LZ7C3 powder was very close to 10:7:3 which was the theory value of LZ7C3. The thermal conductivity of LZ7C3 decreased gradually with the temperature increased up to 1200 oC, and was located within 0.79 to 1.02 W/(m·K), which was almost 50% lower than that of LZ, whereas its thermal expansion coefficient was larger and the value was 11.6×10-6 K-1.