A high-entropy(Ti Zr Nb Ta Mo)C ceramic has been successfully fabricated by hot pressing the newlysynthesized quinary carbide powder to investigate its microstructure and mechanical properties.The carbothermal reducti...A high-entropy(Ti Zr Nb Ta Mo)C ceramic has been successfully fabricated by hot pressing the newlysynthesized quinary carbide powder to investigate its microstructure and mechanical properties.The carbothermal reduction process of equimolar quinary metallic oxides at 1500℃for 1 h generates a carbide powder mixture,which consists mainly of Ta C-and Zr C-based solid solutions.The as-synthesized powder was then sintered to form a single-phase high-entropy ceramic by a two-step hot pressing at 1850℃for1 h and 2100℃for 0.5 h,respectively.The high-entropy ceramic exhibits a fine grain size of about 8.8μm,a high compositional uniformity and a high relative density of 98.6%by adding Mo as the strategic main component.The measured nanohardness values of(TiZrNbTaMo)C ceramic are 25.3 GPa at 9.8 N and 31.3 GPa at 100 m N,respectively,which are clearly higher than those of other available high-entropy carbide ceramics.展开更多
High-entropy intermetallic compounds(HEICs)were fabricated by mechanical alloying and spark plasma sintering to fill a knowledge gap between the traditional high-entropy alloys(HEAs)and emerging highentropy ceramics(H...High-entropy intermetallic compounds(HEICs)were fabricated by mechanical alloying and spark plasma sintering to fill a knowledge gap between the traditional high-entropy alloys(HEAs)and emerging highentropy ceramics(HECs).Notably,several four-or five-component equimolar aluminides,such as the B2-phase(Fe1/5 Co1/5 Ni1/5 Mn1/5 Cu1/5)Al,have been made into single-phase HEICs for the first time.Thermodynamic modeling and a reversible,temperature-dependent,phase-stability experiment suggest that such B2-phase HEICs are entropy-stabilized phases.The structure of these HEICs resembles that of HECs with high-entropy mixing of fo ur or five elements of nearly equal fractions in one and only one sublattice,but with significant(10%)anti-site defects(differing from typical HECs).A new phase stability rule for forming single B2-phase HEICs is proposed.Five additional HEICs of predominantly D022 phases have also been made.This study broadens the families of equimola r,single-phase,high-entropy materials that have been successfully fabricated.展开更多
针对某台超超临界1000MW机组燃用准东煤锅炉水冷壁出现的沾污结渣、高温腐蚀问题,基于锅炉的燃烧煤种特性、结焦状况以及腐蚀类型,开展了纳米高熵陶瓷涂层在锅炉后墙水冷壁燃尽风区域的工程验证试验。采用宏观检查、扫描电子显微镜(scan...针对某台超超临界1000MW机组燃用准东煤锅炉水冷壁出现的沾污结渣、高温腐蚀问题,基于锅炉的燃烧煤种特性、结焦状况以及腐蚀类型,开展了纳米高熵陶瓷涂层在锅炉后墙水冷壁燃尽风区域的工程验证试验。采用宏观检查、扫描电子显微镜(scanning electron microscope,SEM)、X射线衍射(X-ray diffraction,XRD)、拉曼光谱、摩擦系数及表面能测试等方法,分析了纳米高熵陶瓷涂层的使用效果,揭示了纳米高熵陶瓷涂层的防沾污结渣、耐腐蚀机制。试验结果表明,涂层在锅炉运行11个月后完好,表面无明显结焦物、无明显腐蚀凹坑,管壁未发生明显减薄。纳米高熵陶瓷涂层能够较好地解决锅炉水冷壁沾污结渣以及高温腐蚀的问题,为燃用准东煤锅炉的安全运行提供保障。展开更多
High-entropy pyrochlore-type structures based on rare-earth zirconates are successfully produced by conventional solid-state reaction method. Six rare-earth oxides(La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, and Y2O3) and ZrO2...High-entropy pyrochlore-type structures based on rare-earth zirconates are successfully produced by conventional solid-state reaction method. Six rare-earth oxides(La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, and Y2O3) and ZrO2 are used as the raw powders. Five out of the six rare-earth oxides with equimolar ratio and ZrO2 are mixed and sintered at different temperatures for investigating the reaction process. The results demonstrate that the high-entropy pyrochlores(5RE1/5)2 Zr2O7 have been formed after heated at 1000 ℃. The(5RE1/5)2Zr2O7 are highly sintering resistant and possess excellent thermal stability. The thermal conductivities of the(5RE1/5)2Zr2O7 high-entropy ceramics are below 1 W·m–1·K–1 in the temperature range of 300–1200 ℃. The(5RE1/5)2Zr2O7 can be potential thermal barrier coating materials.展开更多
A high-entropy silicide(HES),(Ti_(0.2) Zr_(0.2) Nb_(0.2) Mo_(0.2) W_(0.2))Si_2 with close-packed hexagonal structure is successfully manufactured through reactive spark plasma sintering at 1300 ℃ for 15 min.The eleme...A high-entropy silicide(HES),(Ti_(0.2) Zr_(0.2) Nb_(0.2) Mo_(0.2) W_(0.2))Si_2 with close-packed hexagonal structure is successfully manufactured through reactive spark plasma sintering at 1300 ℃ for 15 min.The elements in this HES are uniformly distributed in the specimen based on the energy dispersive spectrometer analysis except a small amount of zirconium that is combined with oxygen as impurity particles. The Young's modulus, Poisson's ratio,and Vickers hardness of the obtained(Ti_(0.2) Zr_(0.2) Nb_(0.2) Mo_(0.2) W_(0.2))Si_2 are also measured.展开更多
基金supported financially by the National Natural Science Foundation of China(Nos.51602074,51872061,51532006 and 51621091)the Natural Science Foundation of Heilongjiang Province(No.E2016026)+1 种基金the China Postdoctoral Science Foundation(No.2016 M600246)the Heilongjiang Postdoctoral Foundation(No.LBH-Z16084).
文摘A high-entropy(Ti Zr Nb Ta Mo)C ceramic has been successfully fabricated by hot pressing the newlysynthesized quinary carbide powder to investigate its microstructure and mechanical properties.The carbothermal reduction process of equimolar quinary metallic oxides at 1500℃for 1 h generates a carbide powder mixture,which consists mainly of Ta C-and Zr C-based solid solutions.The as-synthesized powder was then sintered to form a single-phase high-entropy ceramic by a two-step hot pressing at 1850℃for1 h and 2100℃for 0.5 h,respectively.The high-entropy ceramic exhibits a fine grain size of about 8.8μm,a high compositional uniformity and a high relative density of 98.6%by adding Mo as the strategic main component.The measured nanohardness values of(TiZrNbTaMo)C ceramic are 25.3 GPa at 9.8 N and 31.3 GPa at 100 m N,respectively,which are clearly higher than those of other available high-entropy carbide ceramics.
基金supported by a Vannevar Bush Faculty Fellowship sponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and Engineeringfunded by the Office of Naval Research(N00014-16-1-2569)funding support from State Key Laboratory of High Performance and Complex Manufacturing at Central South University(ZZYJKT2018-04)
文摘High-entropy intermetallic compounds(HEICs)were fabricated by mechanical alloying and spark plasma sintering to fill a knowledge gap between the traditional high-entropy alloys(HEAs)and emerging highentropy ceramics(HECs).Notably,several four-or five-component equimolar aluminides,such as the B2-phase(Fe1/5 Co1/5 Ni1/5 Mn1/5 Cu1/5)Al,have been made into single-phase HEICs for the first time.Thermodynamic modeling and a reversible,temperature-dependent,phase-stability experiment suggest that such B2-phase HEICs are entropy-stabilized phases.The structure of these HEICs resembles that of HECs with high-entropy mixing of fo ur or five elements of nearly equal fractions in one and only one sublattice,but with significant(10%)anti-site defects(differing from typical HECs).A new phase stability rule for forming single B2-phase HEICs is proposed.Five additional HEICs of predominantly D022 phases have also been made.This study broadens the families of equimola r,single-phase,high-entropy materials that have been successfully fabricated.
文摘针对某台超超临界1000MW机组燃用准东煤锅炉水冷壁出现的沾污结渣、高温腐蚀问题,基于锅炉的燃烧煤种特性、结焦状况以及腐蚀类型,开展了纳米高熵陶瓷涂层在锅炉后墙水冷壁燃尽风区域的工程验证试验。采用宏观检查、扫描电子显微镜(scanning electron microscope,SEM)、X射线衍射(X-ray diffraction,XRD)、拉曼光谱、摩擦系数及表面能测试等方法,分析了纳米高熵陶瓷涂层的使用效果,揭示了纳米高熵陶瓷涂层的防沾污结渣、耐腐蚀机制。试验结果表明,涂层在锅炉运行11个月后完好,表面无明显结焦物、无明显腐蚀凹坑,管壁未发生明显减薄。纳米高熵陶瓷涂层能够较好地解决锅炉水冷壁沾污结渣以及高温腐蚀的问题,为燃用准东煤锅炉的安全运行提供保障。
基金Financial support from the National Natural Science Foundation of China (Nos. 51532009, 51602324, and 51872405) are gratefully acknowledged.
文摘High-entropy pyrochlore-type structures based on rare-earth zirconates are successfully produced by conventional solid-state reaction method. Six rare-earth oxides(La2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, and Y2O3) and ZrO2 are used as the raw powders. Five out of the six rare-earth oxides with equimolar ratio and ZrO2 are mixed and sintered at different temperatures for investigating the reaction process. The results demonstrate that the high-entropy pyrochlores(5RE1/5)2 Zr2O7 have been formed after heated at 1000 ℃. The(5RE1/5)2Zr2O7 are highly sintering resistant and possess excellent thermal stability. The thermal conductivities of the(5RE1/5)2Zr2O7 high-entropy ceramics are below 1 W·m–1·K–1 in the temperature range of 300–1200 ℃. The(5RE1/5)2Zr2O7 can be potential thermal barrier coating materials.
基金Financial support from the National Natural Science Foundation of China (Nos. 51532009 and 51872045)the Science and Technology Commission of Shanghai Municipality (No. 18ZR1401400) are gratefully acknowledged
文摘A high-entropy silicide(HES),(Ti_(0.2) Zr_(0.2) Nb_(0.2) Mo_(0.2) W_(0.2))Si_2 with close-packed hexagonal structure is successfully manufactured through reactive spark plasma sintering at 1300 ℃ for 15 min.The elements in this HES are uniformly distributed in the specimen based on the energy dispersive spectrometer analysis except a small amount of zirconium that is combined with oxygen as impurity particles. The Young's modulus, Poisson's ratio,and Vickers hardness of the obtained(Ti_(0.2) Zr_(0.2) Nb_(0.2) Mo_(0.2) W_(0.2))Si_2 are also measured.
