Ceramic coatings play a keyrole in extending the service life of materials in aerospaceandenergy fields byprotectingmaterials from high temperature,oxidation,corrosion and thermal stress.Non-oxide and high entropy cer...Ceramic coatings play a keyrole in extending the service life of materials in aerospaceandenergy fields byprotectingmaterials from high temperature,oxidation,corrosion and thermal stress.Non-oxide and high entropy ceramics are new emerging coating materials which have been researched and developed in recent years.Compared with traditional oxide ceramics,non-oxide ceramics have better high temperature stability,oxidation resistance and erosion resistance.These characteristics make non-oxide ceramics perform well in extreme environments.It is particularly noteworthy that the non-oxide high entropy ceramic is a uniform solid solution composed of at least four or fiveatoms.Their unique structure and outstanding propertiesshow great potential application in the field of coating.In this paper,the researches aboutregulating microstructure,preparation technology and properties of nitride and its high entropy system,carbide and its high entropy system and boride and its high entropy system in coating field are summarized,and their future development and prospects are prospected.展开更多
High-entropy materials(HEMs)have better mechanical,thermal,and electrical properties than traditional materials due to their special"high entropy effect".They can also adjust the performance of high entropy ...High-entropy materials(HEMs)have better mechanical,thermal,and electrical properties than traditional materials due to their special"high entropy effect".They can also adjust the performance of high entropy ceramics by adjusting the proportion of raw materials,and have broad application prospects in many fields.This article provides a review of the high entropy effect,preparation methods,and main applications of high entropy ceramic materials,especially exploring relevant research on high entropy perovskite ceramics.It is expected to provide reference for the promotion of scientific research and the development of further large-scale applications of high-entropy ceramic materials.展开更多
High entropy carbide ceramics(HECC)are solid solution of inorganic compounds with five or more prin-cipal metal cations.Research interests in HECC are dramatically sparked by the enormous possibilities in composition-...High entropy carbide ceramics(HECC)are solid solution of inorganic compounds with five or more prin-cipal metal cations.Research interests in HECC are dramatically sparked by the enormous possibilities in composition-microstructure-property tailoring.As widely acknowledged,HECCs enjoy higher hardness and oxidation/corrosion/wear resistance,as well as lower thermal conductivity than conventional engi-neering carbide ceramics,making them the most potential candidates for state-of-the-art structural and functional applications in extreme service conditions.Despite the advantages,however,the poor den-sification coupled with low fracture toughness significantly limited the practical applications of HECC.Adding to the difficulty,the literature available for toughening HECC is woefully limited.In considera-tion of this insufficiency,we apply towards offer a comprehensive,critical review of the mechanical be-havior of HECC,highlighting the densification enhancing strategies(carbon content,sintering techniques,grain size,sintering aids,etc.)as well as toughening methods including particle toughening,whisker/fiber toughening,synergistic toughening,graphene-carbon nanotube toughening,to further the service reliabil-ity of HECC in practical industrial applications.Furthermore,despite some significant successes,important directions for further development of HECC are given as multi-dimensional gradient HECC,additive man-ufacturing of HECC,processing-composition-microstructure-property relationship prediction and genomes of HECC based on machine learning,and high-throughput computing,etc.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
Transition metal diborides based ultrahigh temperature ceramics(UHTCs) are characterized by high melting point, high strength and hardness, and high electrical and thermal conductivity. The high thermal conductivity a...Transition metal diborides based ultrahigh temperature ceramics(UHTCs) are characterized by high melting point, high strength and hardness, and high electrical and thermal conductivity. The high thermal conductivity arises from both electronic and phonon contributions. Thus electronic and phonon contributions must be controlled simultaneously in reducing the thermal conductivity of transition metal diborides. In high entropy(HE) materials, both electrons and phonons are scattered such that the thermal conductivity can significantly be reduced, which opens a new window to design novel insulating materials. Inspired by the high entropy effect, porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 is designed in this work as a new thermal insulting ultrahigh temperature material and is synthesized by an in-situ thermal borocarbon reduction/partial sintering process. The porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 possesses high porosity of 75.67%, pore size of 0.3–1.2 μm, homogeneous microstructure with small grain size of 400–800 nm, which results in low room temperature thermal diffusivity and thermal conductivity of 0.74 mm2 s^-1 and 0.51 W m^-1K^-1, respectively. In addition, it exhibits high compressive strength of3.93 MPa. The combination of these properties indicates that exploring porous high entropy ceramics such as porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 is a novel strategy in making UHTCs thermal insulating.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
文摘Ceramic coatings play a keyrole in extending the service life of materials in aerospaceandenergy fields byprotectingmaterials from high temperature,oxidation,corrosion and thermal stress.Non-oxide and high entropy ceramics are new emerging coating materials which have been researched and developed in recent years.Compared with traditional oxide ceramics,non-oxide ceramics have better high temperature stability,oxidation resistance and erosion resistance.These characteristics make non-oxide ceramics perform well in extreme environments.It is particularly noteworthy that the non-oxide high entropy ceramic is a uniform solid solution composed of at least four or fiveatoms.Their unique structure and outstanding propertiesshow great potential application in the field of coating.In this paper,the researches aboutregulating microstructure,preparation technology and properties of nitride and its high entropy system,carbide and its high entropy system and boride and its high entropy system in coating field are summarized,and their future development and prospects are prospected.
文摘High-entropy materials(HEMs)have better mechanical,thermal,and electrical properties than traditional materials due to their special"high entropy effect".They can also adjust the performance of high entropy ceramics by adjusting the proportion of raw materials,and have broad application prospects in many fields.This article provides a review of the high entropy effect,preparation methods,and main applications of high entropy ceramic materials,especially exploring relevant research on high entropy perovskite ceramics.It is expected to provide reference for the promotion of scientific research and the development of further large-scale applications of high-entropy ceramic materials.
基金This work is financially supported by the National Natural Sci-ence Foundation of China(No.52005396)the Guangdong Basic and Applied Basic Research Foundation(No.2023A1515010044)+2 种基金the Open project of State Key Laboratory of Solid Lubrication(LSL-22-11)the Young Talent fund of University Association for Science and Technology in Shaanxi(No.20210414)the Qilu Youth Scholar Project Funding of Shandong University(No.1050522300003).
文摘High entropy carbide ceramics(HECC)are solid solution of inorganic compounds with five or more prin-cipal metal cations.Research interests in HECC are dramatically sparked by the enormous possibilities in composition-microstructure-property tailoring.As widely acknowledged,HECCs enjoy higher hardness and oxidation/corrosion/wear resistance,as well as lower thermal conductivity than conventional engi-neering carbide ceramics,making them the most potential candidates for state-of-the-art structural and functional applications in extreme service conditions.Despite the advantages,however,the poor den-sification coupled with low fracture toughness significantly limited the practical applications of HECC.Adding to the difficulty,the literature available for toughening HECC is woefully limited.In considera-tion of this insufficiency,we apply towards offer a comprehensive,critical review of the mechanical be-havior of HECC,highlighting the densification enhancing strategies(carbon content,sintering techniques,grain size,sintering aids,etc.)as well as toughening methods including particle toughening,whisker/fiber toughening,synergistic toughening,graphene-carbon nanotube toughening,to further the service reliabil-ity of HECC in practical industrial applications.Furthermore,despite some significant successes,important directions for further development of HECC are given as multi-dimensional gradient HECC,additive man-ufacturing of HECC,processing-composition-microstructure-property relationship prediction and genomes of HECC based on machine learning,and high-throughput computing,etc.
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supported by the National Natural Science Foundation of China (Nos. 51672064 and U1435206)
文摘Transition metal diborides based ultrahigh temperature ceramics(UHTCs) are characterized by high melting point, high strength and hardness, and high electrical and thermal conductivity. The high thermal conductivity arises from both electronic and phonon contributions. Thus electronic and phonon contributions must be controlled simultaneously in reducing the thermal conductivity of transition metal diborides. In high entropy(HE) materials, both electrons and phonons are scattered such that the thermal conductivity can significantly be reduced, which opens a new window to design novel insulating materials. Inspired by the high entropy effect, porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 is designed in this work as a new thermal insulting ultrahigh temperature material and is synthesized by an in-situ thermal borocarbon reduction/partial sintering process. The porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 possesses high porosity of 75.67%, pore size of 0.3–1.2 μm, homogeneous microstructure with small grain size of 400–800 nm, which results in low room temperature thermal diffusivity and thermal conductivity of 0.74 mm2 s^-1 and 0.51 W m^-1K^-1, respectively. In addition, it exhibits high compressive strength of3.93 MPa. The combination of these properties indicates that exploring porous high entropy ceramics such as porous HE(Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2 is a novel strategy in making UHTCs thermal insulating.
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.
