Hexagonal boron nitride(h-BN)composite ceramics were prepared by hot pressing with the addition of Y2O3 and AlN.The effects of different Y2O3–AlN contents on microstructural evolution,mechanical properties and therma...Hexagonal boron nitride(h-BN)composite ceramics were prepared by hot pressing with the addition of Y2O3 and AlN.The effects of different Y2O3–AlN contents on microstructural evolution,mechanical properties and thermal diffusion coefficients of h-BN composite ceramics were investigated.The results indicate that Y2O3–AlN forms a liquid phase during the sintering process achieving a good wettability with h-BN grains.In pure h-BN ceramic and h-BN composite ceramic with 40 wt%Y2O3–AlN,the h-BN grains grow well when controlled through solid-phase and liquid-phase diffusion,respectively.With the increase in Y2O3–AlN content,mechanical properties and thermal diffusion coefficients of h-BN composite ceramics first decrease and then increase,and the properties of h-BN composite ceramic with 10 wt%Y2O3–AlN are the inflection points.Such properties are highly related to the phase compositions,porosity and microstructure.展开更多
Cold sintering is a newly developed low-temperature sintering technique that has attracted extensive attention in the fabrication of functional materials and devices.Low sintering temperatures allow for a substantial ...Cold sintering is a newly developed low-temperature sintering technique that has attracted extensive attention in the fabrication of functional materials and devices.Low sintering temperatures allow for a substantial reduction in energy consumption,and simple experimental equipment offers the possibility of large-scale fabrication.The cold sintering process(CSP)has been demonstrated to be a green and cost-effective route to fabricate thermoelectric(TE)materials where significant grain growth,secondary phase formation,and element volatilization,which are prone to occur during high-temperature sintering,can be well controlled.In this review,the historical development,understanding,and application of thermoelectric materials produced via cold sintering are highlighted.The latest attempts related to the cold sintering process for thermoelectric materials and devices are discussed and evaluated.Despite some current technical challenges,cold sintering provides a promising and sustainable route for the design of advanced high-performance thermoelectrics.展开更多
Understanding the process of chemical reactions has always been a relentless pursuit for chemists.The development of femtosecond pump-probe techniques since the 1980s has revolutionized the field of chemical dynamics,...Understanding the process of chemical reactions has always been a relentless pursuit for chemists.The development of femtosecond pump-probe techniques since the 1980s has revolutionized the field of chemical dynamics,enabling the capture of timeresolved snapshots of reactions on the femtosecond timescale.Starting from the 2010s,breakthroughs in femtosecond electron and X-ray sources has enabled ultrafast electron and X-ray diffraction techniques,which is able to directly reveal the temporal evolution of atomic geometries of molecules,allowing for the creation of molecular movies.Gas-phase molecular movies reveal intrinsic intramolecular processes,while liquid-phase molecular movies provide insights for complicated solvent-solute interplay.This minireview focuses on the advances in studying gasphase and liquid-phase molecular dynamics(MD)using ultrafast electron and X-ray diffraction techniques on femtosecond and picosecond timescales.The fast-developing experimental capability of the direct observation of molecular structural evolution during chemical reactions,on its natural femtosecond timescale and subangstrom length scale,offers tremendous potential for the field of chemical kinetics and MD.展开更多
A new method,named the complete liquid-phase technology,has been applied to prepare catalysts for methanol synthesis.Its main innovative thought lies in preparing slurry catalysts directly from raw solution.Activity t...A new method,named the complete liquid-phase technology,has been applied to prepare catalysts for methanol synthesis.Its main innovative thought lies in preparing slurry catalysts directly from raw solution.Activity tests indicate that the CuZnAl slurry catalyst prepared by the new method can efficiently catalyze conversion of syngas to ethanol in a slurry reactor,while CO conversion reaches 35.9%and ethanol selectivity is more than 20%,with a total alcohol selectivity of more than 87%.No deactivation was found during the 192 h reaction.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2017YFB0703200)the National Natural Science Foundation of China(Nos.51672060,51621091 and 51372050)。
文摘Hexagonal boron nitride(h-BN)composite ceramics were prepared by hot pressing with the addition of Y2O3 and AlN.The effects of different Y2O3–AlN contents on microstructural evolution,mechanical properties and thermal diffusion coefficients of h-BN composite ceramics were investigated.The results indicate that Y2O3–AlN forms a liquid phase during the sintering process achieving a good wettability with h-BN grains.In pure h-BN ceramic and h-BN composite ceramic with 40 wt%Y2O3–AlN,the h-BN grains grow well when controlled through solid-phase and liquid-phase diffusion,respectively.With the increase in Y2O3–AlN content,mechanical properties and thermal diffusion coefficients of h-BN composite ceramics first decrease and then increase,and the properties of h-BN composite ceramic with 10 wt%Y2O3–AlN are the inflection points.Such properties are highly related to the phase compositions,porosity and microstructure.
基金Jinxue Ding acknowledges financial support from the China Scholarship Council(No.202106290061)Jing Guo is thankful for the financial support provided by the Natural Science Foundation of Shaanxi Province,China(No.2024JC-YBMS-349)+1 种基金Wei Li and Yanqin Fu appreciate the financial support provided by the TU Darmstadt Career Bridging Grant.Wenjie Xie and Anke Weidenkaff are grateful for the financial support from the Seed-funding of TUDa(Project-ID:40101580)the DAAD Förderprogramme(Project-ID:57610929).
文摘Cold sintering is a newly developed low-temperature sintering technique that has attracted extensive attention in the fabrication of functional materials and devices.Low sintering temperatures allow for a substantial reduction in energy consumption,and simple experimental equipment offers the possibility of large-scale fabrication.The cold sintering process(CSP)has been demonstrated to be a green and cost-effective route to fabricate thermoelectric(TE)materials where significant grain growth,secondary phase formation,and element volatilization,which are prone to occur during high-temperature sintering,can be well controlled.In this review,the historical development,understanding,and application of thermoelectric materials produced via cold sintering are highlighted.The latest attempts related to the cold sintering process for thermoelectric materials and devices are discussed and evaluated.Despite some current technical challenges,cold sintering provides a promising and sustainable route for the design of advanced high-performance thermoelectrics.
基金the National Key Research and Development Program of China(grant no.2021YFA1601200)the National Natural Science Foundation of China(grant no.22273044).
文摘Understanding the process of chemical reactions has always been a relentless pursuit for chemists.The development of femtosecond pump-probe techniques since the 1980s has revolutionized the field of chemical dynamics,enabling the capture of timeresolved snapshots of reactions on the femtosecond timescale.Starting from the 2010s,breakthroughs in femtosecond electron and X-ray sources has enabled ultrafast electron and X-ray diffraction techniques,which is able to directly reveal the temporal evolution of atomic geometries of molecules,allowing for the creation of molecular movies.Gas-phase molecular movies reveal intrinsic intramolecular processes,while liquid-phase molecular movies provide insights for complicated solvent-solute interplay.This minireview focuses on the advances in studying gasphase and liquid-phase molecular dynamics(MD)using ultrafast electron and X-ray diffraction techniques on femtosecond and picosecond timescales.The fast-developing experimental capability of the direct observation of molecular structural evolution during chemical reactions,on its natural femtosecond timescale and subangstrom length scale,offers tremendous potential for the field of chemical kinetics and MD.
文摘A new method,named the complete liquid-phase technology,has been applied to prepare catalysts for methanol synthesis.Its main innovative thought lies in preparing slurry catalysts directly from raw solution.Activity tests indicate that the CuZnAl slurry catalyst prepared by the new method can efficiently catalyze conversion of syngas to ethanol in a slurry reactor,while CO conversion reaches 35.9%and ethanol selectivity is more than 20%,with a total alcohol selectivity of more than 87%.No deactivation was found during the 192 h reaction.
