Yttrium aluminum perovskite(YAl O3)is a promising candidate material for environmental barrier coatings(EBCs)to protect Al2 O3 f/Al2 O3 ceramic matrix composites(CMCs)from the corrosion of high-temperature water vapor...Yttrium aluminum perovskite(YAl O3)is a promising candidate material for environmental barrier coatings(EBCs)to protect Al2 O3 f/Al2 O3 ceramic matrix composites(CMCs)from the corrosion of high-temperature water vapor in combustion environments.Nevertheless,the relatively high thermal conductivity is a notable drawback of YAl O3 for environmental barrier coating application.Herein,in order to make REAl O3 more thermal insulating,a novel high-entropy rare-earth aluminate ceramic(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 was designed and synthesized.The as-prepared(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 ceramic possesses close thermal expansion coefficient(9.02×10-6/oC measured from room temperature to 1200℃)to that of Al2 O3.The thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 at room temperature is 4.1 W·m-1K-1,which is almost one third of the value of YAl O3.Furthermore,to effectively prevent the penetration of water vapor from possible pores/cracks of coating layer,which are often observed in T/EBCs,a tri-layer EBC system REAl O3/RE3 Al5 O12/(Al2 O3 f/Al2 O3 CMCs)is designed.Close thermal expansion coefficient to Al2 O3 and low thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3,as well as the formation of dense garnet layer at(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3/Al2 O3 interface,indicate that this new type of high-entropy ceramic is suitable as a candidate environmental barrier coating material for Al2 O3 f/Al2 O3 CMCs.展开更多
为了降低Ca Ti O3-（La,Nd）Al O3（简称CT-LNA）陶瓷的烧结温度和提高其介电性能,研究纳米Al2O3对Ca Ti O3-（La,Nd）Al O3陶瓷的烧结温度和介电性能的影响。固相法制备粉料,采用XRD和SEM分析其晶相和显微结构,用网络分析测试样品的介...为了降低Ca Ti O3-（La,Nd）Al O3（简称CT-LNA）陶瓷的烧结温度和提高其介电性能,研究纳米Al2O3对Ca Ti O3-（La,Nd）Al O3陶瓷的烧结温度和介电性能的影响。固相法制备粉料,采用XRD和SEM分析其晶相和显微结构,用网络分析测试样品的介电参数,结果表明,纳米Al2O3可促进陶瓷烧结,在1320~1400℃范围内可烧结成瓷,并具有较好的微波介电性能。当纳米Al2O3含量为50 wt%时,陶瓷在1340℃烧结可获得优良的微波介电性能：介电常数为42.6,Q×f值高达34,000GHz,频率温度系数为＋4.8 ppm/℃。展开更多
A l2O3陶瓷具有耐高温、抗氧化、耐磨损等优良特性,但韧性低一直是阻碍其进一步应用的重要原因。本文分别通过颗粒弥散相增韧、纤维/晶须增韧、相变增韧、复合增韧以及自增韧等方法对A l2O3陶瓷的增韧研究进行了分类叙述,总结了高韧性...A l2O3陶瓷具有耐高温、抗氧化、耐磨损等优良特性,但韧性低一直是阻碍其进一步应用的重要原因。本文分别通过颗粒弥散相增韧、纤维/晶须增韧、相变增韧、复合增韧以及自增韧等方法对A l2O3陶瓷的增韧研究进行了分类叙述,总结了高韧性氧化铝陶瓷的制备、增韧机理、影响因素的研究进展。展开更多
基金financial supported by the National Natural Science Foundation of China(Nos.51672064 and 51972089)。
文摘Yttrium aluminum perovskite(YAl O3)is a promising candidate material for environmental barrier coatings(EBCs)to protect Al2 O3 f/Al2 O3 ceramic matrix composites(CMCs)from the corrosion of high-temperature water vapor in combustion environments.Nevertheless,the relatively high thermal conductivity is a notable drawback of YAl O3 for environmental barrier coating application.Herein,in order to make REAl O3 more thermal insulating,a novel high-entropy rare-earth aluminate ceramic(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 was designed and synthesized.The as-prepared(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 ceramic possesses close thermal expansion coefficient(9.02×10-6/oC measured from room temperature to 1200℃)to that of Al2 O3.The thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 at room temperature is 4.1 W·m-1K-1,which is almost one third of the value of YAl O3.Furthermore,to effectively prevent the penetration of water vapor from possible pores/cracks of coating layer,which are often observed in T/EBCs,a tri-layer EBC system REAl O3/RE3 Al5 O12/(Al2 O3 f/Al2 O3 CMCs)is designed.Close thermal expansion coefficient to Al2 O3 and low thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3,as well as the formation of dense garnet layer at(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3/Al2 O3 interface,indicate that this new type of high-entropy ceramic is suitable as a candidate environmental barrier coating material for Al2 O3 f/Al2 O3 CMCs.
文摘为了降低Ca Ti O3-（La,Nd）Al O3（简称CT-LNA）陶瓷的烧结温度和提高其介电性能,研究纳米Al2O3对Ca Ti O3-（La,Nd）Al O3陶瓷的烧结温度和介电性能的影响。固相法制备粉料,采用XRD和SEM分析其晶相和显微结构,用网络分析测试样品的介电参数,结果表明,纳米Al2O3可促进陶瓷烧结,在1320~1400℃范围内可烧结成瓷,并具有较好的微波介电性能。当纳米Al2O3含量为50 wt%时,陶瓷在1340℃烧结可获得优良的微波介电性能：介电常数为42.6,Q×f值高达34,000GHz,频率温度系数为＋4.8 ppm/℃。
