高熵陶瓷材料成分与结构的多样性使其在材料设计与性能优化方面极具潜力。本研究以Mg元素为基础,与4种过渡金属元素(Cu、Co、Zn、Ni)进行组合,采用水热-煅烧两步法制备了具有岩盐结构的氧化物(Mg 1-4 x Co x Ni x Zn x Cu x)O,利用X射...高熵陶瓷材料成分与结构的多样性使其在材料设计与性能优化方面极具潜力。本研究以Mg元素为基础,与4种过渡金属元素(Cu、Co、Zn、Ni)进行组合,采用水热-煅烧两步法制备了具有岩盐结构的氧化物(Mg 1-4 x Co x Ni x Zn x Cu x)O,利用X射线衍射(XRD)、扫描电镜(SEM)、差热分析/热重分析(DTA/TG)和紫外可见漫反射光谱(Uv-Vis DRS)等方法研究了反应时间、沉淀剂用量及金属元素配比对前驱体和最终氧化物样品结构及性能的影响。研究发现:当金属元素(Mg、Cu、Co、Zn、Ni)总摩尔数与沉淀剂(碳酸钠)的摩尔比为1∶1,水热反应时间为8 h,且金属元素采用等摩尔比配比时,可以制备出单一物相的镁基高熵碳酸盐前驱体(Mg 0.2 Co 0.2 Ni 0.2 Zn 0.2 Cu 0.2)CO 3;无论金属元素采用等摩尔比或非等摩尔比配比,前驱体在煅烧后均能形成单一物相的氧化物(Mg 1-4 x Co x Ni x Zn x Cu x)O;金属元素配比影响氧化物晶体的生长习性,进而影响其光学性能。展开更多
The composition−property relationship of 18 quaternary high entropy diborides(HEBs)consisting of boron and IVB,VB and VIB transition metals(TM)was investigated using first-principles calculations.A valence electron co...The composition−property relationship of 18 quaternary high entropy diborides(HEBs)consisting of boron and IVB,VB and VIB transition metals(TM)was investigated using first-principles calculations.A valence electron concentration−relative electronegativity(VEC−REN)composite descriptor was developed to effectively predict the mechanical properties of HEBs.The results demonstrate that with a fixed VEC,the rise of the REN makes HEBs harder but more brittle when the electronegativity of doped TM atoms is lower than that of boron atoms.However,HEBs become softer and more ductile as REN increases if the doped TM atoms have higher electronegativity than boron atoms.The VEC−REN composite descriptor can accurately classify and predict the mechanical properties of HEBs with different components,which provides important theoretical guidance for the rapid design and development of novel high-entropy ceramic materials.展开更多
Ceramic thin plates were prepared using kaolin,potassium sodium feldspar and quartz powder as the main raw materials and kaolin,α-Al_(2)O_(3),MoO_(3) and AlF_(3)·3H_(2)O as additives.The experiment examined the ...Ceramic thin plates were prepared using kaolin,potassium sodium feldspar and quartz powder as the main raw materials and kaolin,α-Al_(2)O_(3),MoO_(3) and AlF_(3)·3H_(2)O as additives.The experiment examined the effects of different additives on mullite formation,as well as the microstructure and properties of the ceramic thin plates.Additionally,the study explored the toughening and strengthening mechanisms induced by the additives,providing a theoretical foundation for further optimizing the toughness of ceramic thin plates.The results showed that the D4 sample fired at 1220℃(with an addition of 20 wt% α-Al_(2)O_(3))exhibited the best performance,with a water absorption rate of 0.07%,apparent porosity of 0.18%,bulk density of 2.75 g·cm^(-3),firing shrinkage of 12.76%,bending strength reaching 101.93 MPa,and fracture toughness of 2.51 MPa·m^(1/2).As the amount ofα-Al_(2)O_(3) additive increased,the ceramic thin plates exhibited a greater abundance of short rod-like mullite and corundum grains,which were tightly packed together,forming a framework for the ceramic thin plates.This microstructure enhanced pathways for crack propagation,dispersed internal stresses,and increased fracture surface energy,resulting in significant improvements in both strength and fracture toughness of the ceramic thin plates.展开更多
(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperatu...(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperature properties.This study systematically investigates the mechanical properties of(NbZrHfTi)C high-entropy ceramics by employing first-principles density functional theory,combined with the Debye-Grüneisen model,to explore the variations in their thermophysical properties with temperature(0–2000 K)and pressure(0–30 GPa).Thermodynamically,the calculated mixing enthalpy and Gibbs free energy confirm the feasibility of forming a stable single-phase solid solution in(NbZrHfTi)C.The calculated results of the elastic stiffness constant indicate that the material meets the mechanical stability criteria of the cubic crystal system,further confirming the structural stability.Through evaluation of key mechanical parameters—bulk modulus,shear modulus,Young’s modulus,and Poisson’s ratio—we provide comprehensive insight into the macro-mechanical behaviour of the material and its correlation with the underlying microstructure.Notably,compared to traditional binary carbides and their average properties,(NbZrHfTi)C exhibits higher Vickers hardness(Approximately 28.5 GPa)and fracture toughness(Approximately 3.4 MPa⋅m^(1/2)),which can be primarily attributed to the lattice distortion and solid-solution strengthening mechanism.The study also utilizes the quasi-harmonic approximation method to predict the material’s thermophysical properties,including Debye temperature(initial value around 563 K),thermal expansion coefficient(approximately 8.9×10^(−6) K−1 at 2000 K),and other key parameters such as heat capacity at constant volume.The results show that within the studied pressure and temperature ranges,(NbZrHfTi)C consistently maintains a stable phase structure and good thermomechanical properties.The thermal expansion coefficient increasing with temperature,while heat capacity approaches the Dulong-Petit limit at elevated temperatures.These findings underscore the potential of(NbZrHfTi)C applications in ultra-high temperature thermal protection systems,cutting tool coatings,and nuclear structural materials.展开更多
文摘高熵陶瓷材料成分与结构的多样性使其在材料设计与性能优化方面极具潜力。本研究以Mg元素为基础,与4种过渡金属元素(Cu、Co、Zn、Ni)进行组合,采用水热-煅烧两步法制备了具有岩盐结构的氧化物(Mg 1-4 x Co x Ni x Zn x Cu x)O,利用X射线衍射(XRD)、扫描电镜(SEM)、差热分析/热重分析(DTA/TG)和紫外可见漫反射光谱(Uv-Vis DRS)等方法研究了反应时间、沉淀剂用量及金属元素配比对前驱体和最终氧化物样品结构及性能的影响。研究发现:当金属元素(Mg、Cu、Co、Zn、Ni)总摩尔数与沉淀剂(碳酸钠)的摩尔比为1∶1,水热反应时间为8 h,且金属元素采用等摩尔比配比时,可以制备出单一物相的镁基高熵碳酸盐前驱体(Mg 0.2 Co 0.2 Ni 0.2 Zn 0.2 Cu 0.2)CO 3;无论金属元素采用等摩尔比或非等摩尔比配比,前驱体在煅烧后均能形成单一物相的氧化物(Mg 1-4 x Co x Ni x Zn x Cu x)O;金属元素配比影响氧化物晶体的生长习性,进而影响其光学性能。
基金the National Natural Science Foundation of China (Nos. 52071179, 52271033)the Key Program of National Natural Science Foundation of China (No. 51931003)+2 种基金the Natural Science Foundation of Jiangsu Province, China (No. BK20221493)the Jiangsu Province Leading Edge Technology Basic Research Major Project, China (No. BK20222014)the Foundation of “Qinglan Project” for Colleges and Universities in Jiangsu Province, China。
文摘The composition−property relationship of 18 quaternary high entropy diborides(HEBs)consisting of boron and IVB,VB and VIB transition metals(TM)was investigated using first-principles calculations.A valence electron concentration−relative electronegativity(VEC−REN)composite descriptor was developed to effectively predict the mechanical properties of HEBs.The results demonstrate that with a fixed VEC,the rise of the REN makes HEBs harder but more brittle when the electronegativity of doped TM atoms is lower than that of boron atoms.However,HEBs become softer and more ductile as REN increases if the doped TM atoms have higher electronegativity than boron atoms.The VEC−REN composite descriptor can accurately classify and predict the mechanical properties of HEBs with different components,which provides important theoretical guidance for the rapid design and development of novel high-entropy ceramic materials.
基金Funded by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No.2023YFB4204302)。
文摘Ceramic thin plates were prepared using kaolin,potassium sodium feldspar and quartz powder as the main raw materials and kaolin,α-Al_(2)O_(3),MoO_(3) and AlF_(3)·3H_(2)O as additives.The experiment examined the effects of different additives on mullite formation,as well as the microstructure and properties of the ceramic thin plates.Additionally,the study explored the toughening and strengthening mechanisms induced by the additives,providing a theoretical foundation for further optimizing the toughness of ceramic thin plates.The results showed that the D4 sample fired at 1220℃(with an addition of 20 wt% α-Al_(2)O_(3))exhibited the best performance,with a water absorption rate of 0.07%,apparent porosity of 0.18%,bulk density of 2.75 g·cm^(-3),firing shrinkage of 12.76%,bending strength reaching 101.93 MPa,and fracture toughness of 2.51 MPa·m^(1/2).As the amount ofα-Al_(2)O_(3) additive increased,the ceramic thin plates exhibited a greater abundance of short rod-like mullite and corundum grains,which were tightly packed together,forming a framework for the ceramic thin plates.This microstructure enhanced pathways for crack propagation,dispersed internal stresses,and increased fracture surface energy,resulting in significant improvements in both strength and fracture toughness of the ceramic thin plates.
基金supported by the National Natural Science Foundation of China(Nos.92166105 and 52005053)High-Tech Industry Science and Technology Innovation Leading Program of Hunan Province(No.2020GK2085)the Science and Technology Innovation Program of Hunan Province(No.2021RC3096).
文摘(NbZrHfTi)C high-entropy ceramics,as an emerging class of ultra-high-temperature materials,have garnered significant interest due to their unique multi-principal-element crystal structure and exceptional hightemperature properties.This study systematically investigates the mechanical properties of(NbZrHfTi)C high-entropy ceramics by employing first-principles density functional theory,combined with the Debye-Grüneisen model,to explore the variations in their thermophysical properties with temperature(0–2000 K)and pressure(0–30 GPa).Thermodynamically,the calculated mixing enthalpy and Gibbs free energy confirm the feasibility of forming a stable single-phase solid solution in(NbZrHfTi)C.The calculated results of the elastic stiffness constant indicate that the material meets the mechanical stability criteria of the cubic crystal system,further confirming the structural stability.Through evaluation of key mechanical parameters—bulk modulus,shear modulus,Young’s modulus,and Poisson’s ratio—we provide comprehensive insight into the macro-mechanical behaviour of the material and its correlation with the underlying microstructure.Notably,compared to traditional binary carbides and their average properties,(NbZrHfTi)C exhibits higher Vickers hardness(Approximately 28.5 GPa)and fracture toughness(Approximately 3.4 MPa⋅m^(1/2)),which can be primarily attributed to the lattice distortion and solid-solution strengthening mechanism.The study also utilizes the quasi-harmonic approximation method to predict the material’s thermophysical properties,including Debye temperature(initial value around 563 K),thermal expansion coefficient(approximately 8.9×10^(−6) K−1 at 2000 K),and other key parameters such as heat capacity at constant volume.The results show that within the studied pressure and temperature ranges,(NbZrHfTi)C consistently maintains a stable phase structure and good thermomechanical properties.The thermal expansion coefficient increasing with temperature,while heat capacity approaches the Dulong-Petit limit at elevated temperatures.These findings underscore the potential of(NbZrHfTi)C applications in ultra-high temperature thermal protection systems,cutting tool coatings,and nuclear structural materials.
