As a new category of ultra-high-temperature ceramics(UHTCs),multi-anionic high-entropy(HE)carbonitride UHTCs are expected to have better comprehensive performance than conventional UHTCs.However,how to realize the gre...As a new category of ultra-high-temperature ceramics(UHTCs),multi-anionic high-entropy(HE)carbonitride UHTCs are expected to have better comprehensive performance than conventional UHTCs.However,how to realize the green and low-cost synthesis of high-quality multi-anionic HE carbonitride UHTC powders and prepare bulk ceramics with excellent mechanical properties still faces great challenges.In this work,a green,low-cost,and controllable preparation process of(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C,N_(1-x) powders is achieved by sol-gel combined with the carbothermal reduction/nitridation method for the first time.The as-synthesized(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C_(x)N_(1-x) powders possess high compositional uniformity and controllable particle size.In addition,the obtained bulk ceramics prepared at 1800℃exhibit superior fracture toughness(Kic)of 5.39±0.16 MPa·m^(1/2) and high nanohardnesof 35.75±1.23 GPa,lastic modulus(E)of 566.70±8.68 GPa,and flexural strength of 487±41 MPa.This study provides a feasible strategy for preparing the high-performance HE carbonitride ceramics in a more environmentally friendly and economical manner.展开更多
It is a meaningful and challenging work for structural and synthetic chemists to isolate nano-sized high-nuclearity cluster-molecules.In this work,two largest hetero-metallic nano-clusters Gd_(158)Co_(38) were obtaine...It is a meaningful and challenging work for structural and synthetic chemists to isolate nano-sized high-nuclearity cluster-molecules.In this work,two largest hetero-metallic nano-clusters Gd_(158)Co_(38) were obtained via the“multi-anions-template”method.Different from the reported giant hollow-nano-clusters,the Ln_(158) core in Gd_(158)Co_(38)(the protein-sized nano-clusters,ca.4.3 nm×3.6 nm×3.5 nm)has the highest Ln nuclear number,which is integrated by twelve halide ions(with the form of icosahedron)as key templates,while Co ions(as 3d metals)are located in its periphery.This emergence indicates a novel structure form of non-open Ln-containing high-nuclearity clusters,and affords a consummate pattern to analyse and assemble the complex cluster-molecules.In addition,Gd_(158)Co_(38)@Cl_(12)breaks the record magnetic entropy change of 3d-4f clusters with−∆S_(m)^(max)=46.95 J kg^(−1)K^(−1)at 7.0 T,2.0 K.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52272060,51902067,51872066,and 52002001)Key Program of National Natural Science Foundation of China(No.52032003)+6 种基金the China Postdoctoral Science Foundation(Nos.2019M651282 and 2022T150157)the Heilongjiang Provincial Postdoctoral Science Foundation(Nos.LBH-Z19022 and LBH-TZ2207)Heilongjiang Touyan Innovation Team Program,the Shanghai Aerospace Scienceand Technology Innovation Fund(No.SAST2019-012)the Fundamental Research Funds for the Central Universities(No.FRFCU5710051022)the Science Foundation of National Key Laboratory of Science and Technology on Advanced composites in Special Environments(No.JCKYS2022603C011)Domestic Visiting and Studying Project for Outstanding Young Key Talents in Universities of Anhui Province(No.gxgnfx2021131)Young and Middle-aged Top Talent Project of Anhui Polytechnic University.
文摘As a new category of ultra-high-temperature ceramics(UHTCs),multi-anionic high-entropy(HE)carbonitride UHTCs are expected to have better comprehensive performance than conventional UHTCs.However,how to realize the green and low-cost synthesis of high-quality multi-anionic HE carbonitride UHTC powders and prepare bulk ceramics with excellent mechanical properties still faces great challenges.In this work,a green,low-cost,and controllable preparation process of(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C,N_(1-x) powders is achieved by sol-gel combined with the carbothermal reduction/nitridation method for the first time.The as-synthesized(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C_(x)N_(1-x) powders possess high compositional uniformity and controllable particle size.In addition,the obtained bulk ceramics prepared at 1800℃exhibit superior fracture toughness(Kic)of 5.39±0.16 MPa·m^(1/2) and high nanohardnesof 35.75±1.23 GPa,lastic modulus(E)of 566.70±8.68 GPa,and flexural strength of 487±41 MPa.This study provides a feasible strategy for preparing the high-performance HE carbonitride ceramics in a more environmentally friendly and economical manner.
基金supported by the National Key R&D Program of China(2018YFA0306004)the National Natural Science Foundation of China(21571103,21973038)+1 种基金Jiangsu Province(BK20191359)the Joint Fund for Regional Innovation and Development(U20A2073)。
文摘It is a meaningful and challenging work for structural and synthetic chemists to isolate nano-sized high-nuclearity cluster-molecules.In this work,two largest hetero-metallic nano-clusters Gd_(158)Co_(38) were obtained via the“multi-anions-template”method.Different from the reported giant hollow-nano-clusters,the Ln_(158) core in Gd_(158)Co_(38)(the protein-sized nano-clusters,ca.4.3 nm×3.6 nm×3.5 nm)has the highest Ln nuclear number,which is integrated by twelve halide ions(with the form of icosahedron)as key templates,while Co ions(as 3d metals)are located in its periphery.This emergence indicates a novel structure form of non-open Ln-containing high-nuclearity clusters,and affords a consummate pattern to analyse and assemble the complex cluster-molecules.In addition,Gd_(158)Co_(38)@Cl_(12)breaks the record magnetic entropy change of 3d-4f clusters with−∆S_(m)^(max)=46.95 J kg^(−1)K^(−1)at 7.0 T,2.0 K.
