It is desirable to fabricate materials with adjustable physical properties that can be used in different industrial applications.Since the property of a material is highly dependent on its inner structure,the understa...It is desirable to fabricate materials with adjustable physical properties that can be used in different industrial applications.Since the property of a material is highly dependent on its inner structure,the understanding of structure–property correlation is critical to the design of engineering materials.3D printing appears as a mature method to effectively produce micro-structured materials.In this work,we created different stainless-steel microstructures by adjusting the speed of 3D printing and studied the relationship between thermal property and printing speed.Our microstructure study demonstrates that highly porous structures appear at higher speeds,and there is a nearly linear relationship between porosity and printing speed.The thermal conductivity of samples fabricated by different printing speeds is characterized.Then,the correlation between porosity,thermal conductivity,and scanning speed is established.Based on this correlation,the thermal conductivity of a sample can be predicted from its printing speed.We fabricated a new sample at a different speed,and the thermal conductivity measurement agrees well with the value predicted from the correlation.To explore thermal transport physics,the effects of pore structure and temperature on the thermal performance of the printed block are also studied.Our work demonstrates that the combination of the 3D printing technique and the printing speed control can regulate the thermophysical properties of materials.展开更多
Electrocatalyst designs based on oxophilic foreign atoms are considered a promising approach for developing efficient pH-universal hydrogen evolution reaction(HER)electrocatalysts by overcoming the sluggish alkaline H...Electrocatalyst designs based on oxophilic foreign atoms are considered a promising approach for developing efficient pH-universal hydrogen evolution reaction(HER)electrocatalysts by overcoming the sluggish alkaline HER kinetics.Here,we design ternary transition metals-based nickel telluride(Mo WNi Te)catalysts consisting of high valence non-3d Mo and W metals and oxophilic Te as a first demonstration of non-precious heterogeneous electrocatalysts following the bifunctional mechanism.The Mo WNi Te showed excellent HER catalytic performance with overpotentials of 72,125,and 182 mV to reach the current densities of 10,100,and 1000 mA cm^(-2),respectively,and the corresponding Tafel slope of 47,52,and 58 mV dec-1in alkaline media,which is much superior to commercial Pt/C.Additionally,the HER performance of Mo WNi Te is well maintained up to 3000 h at the current density of 100 mA cm^(-2).It is further demonstrated that the Mo WNi Te exhibits remarkable HER activities with an overpotential of 45 mV(31 mV)and Tafel slope of 60 mV dec-1(34 mV dec-1)at 10 mA cm^(-2)in neutral(acid)media.The superior HER performance of Mo WNi Te is attributed to the electronic structure modulation,inducing highly active low valence states by the incorporation of high valence non-3d transition metals.It is also attributed to the oxophilic effect of Te,accelerating water dissociation kinetics through a bifunctional catalytic mechanism in alkaline media.Density functional theory calculations further reveal that such synergistic effects lead to reduced free energy for an efficient water dissociation process,resulting in remarkable HER catalytic performances within universal pH environments.展开更多
Laser-assisted manufacturing(LAM)is a technique that performs machining of materials using a laser heating process.During the process,temperatures can rise above over 2000°C.As a result,it is crucial to explore t...Laser-assisted manufacturing(LAM)is a technique that performs machining of materials using a laser heating process.During the process,temperatures can rise above over 2000°C.As a result,it is crucial to explore the thermal behavior of materials under such high temperatures to understand the physics behind LAM and provide feedback for manufacturing optimization.Raman spectroscopy,which is widely used for structure characterization,can provide a novel way to measure temperature during LAM.In this review,we discuss the mechanism of Raman-based temperature probing,its calibration,and sources of uncertainty/error,and how to control them.We critically review the Raman-based temperature measurement considering the spatial resolution under near-field optical heating and surface structure-induced asymmetries.As another critical aspect of Raman-based temperature measurement,temporal resolution is also reviewed to cover various ways of realizing ultrafast thermal probing.We conclude with a detailed outlook on Raman-based temperature probing in LAM and issues that need special attention.展开更多
High-entropy alloys(HEAs)exhibit extraordinary physical properties such as superior strength-to-weight ratios and enhanced corrosion and oxidation resistance,making them potentially useful in energy storage and gener-...High-entropy alloys(HEAs)exhibit extraordinary physical properties such as superior strength-to-weight ratios and enhanced corrosion and oxidation resistance,making them potentially useful in energy storage and gener-ation industries.However,thermal and mechanical properties of HEAs with various compositions vary signifi-cantly.Furthermore,these properties have rarely been investigated simultaneously owing to material or instru-mentation limitations.Herein,we synthesize an HEA(AlCrNbSiTi)coating with a thickness of less than 2μm.We customize a frequency-domain photothermal testing system to characterize the thermal and mechanical proper-ties of the proposed coating with high accuracy.Owing to the large mixing enthalpy of the Al-Ti,Nb-Si,and Ti-Si pairs in the coating,its hardness and elastic modulus are 15.2 and 254.7 GPa,respectively,which are higher than those of previously reported HEAs.The thermal conductivity of the AlCrNbSiTi coating is characterized to be 2.90 W·m^(−1)·K^(−1),within the expected range and well explained by the free-electron consistency diversity and phonon scattering from the amorphous structure.Additionally,the coating exhibits adequate wear performance,with a wear rate of 5.4×10^(−8) mm^(3)·N^(−1)·m^(−1).This relatively low thermal conductivity,combined with extraordi-nary mechanical properties,makes the proposed material an excellent candidate as a protective coating material for nuclear reactor components which require high strength,irradiation resistance,and thermal protection.展开更多
Semiconductors are promising in photoelectric and thermoelectric devices, for which the thermal transport properties are of particular interest. However, they have not been fully understood, especially when crystallin...Semiconductors are promising in photoelectric and thermoelectric devices, for which the thermal transport properties are of particular interest. However, they have not been fully understood, especially when crystalline imperfections are present. Here, using cadmium telluride (CdTe) as an example, we illustrate how grain boundaries (GBs) affect the thermal transport properties of semiconductors. We develop a machine-learning force field from density functional theory calculations for predicting the lattice thermal conductivity (LTC) via equilibrium molecular dynamics simulations. The LTC of crystalline CdTe decreases with the relationship of κL~1/T in the simulation temperature range of 300 – 900 K, in which the isotropic LTC decreases from 3.34 to 0.23 W/ (m⋅K) due to the enhanced anharmonicity. More important, after introducing GBs, the LTC is suppressed in all directions, especially in the direction normal to the GB planes. More severe LTC suppression occurs in CdTe with Σ9 GB than that with Σ3 GB at 300 K, decreasing by 92.8% and 61.4% along the direction normal to the GB planes compared to the isotropic LTC of the crystalline CdTe, respectively. The decreased LTC is consistent with the weaker bonding near GB planes and lower shear modulus of the defective material. The analyses of the phonon dispersion curves, vibrational density of states, and phonon participation ratio indicate that the decreased LTC mainly arises from phonon scattering at GBs. Overall, our work highlights that GBs can greatly influence the LTC of semiconductors, thus providing a promising approach for thermal property design.展开更多
基金supported by the National Key R&D Program of China(Nos.2018YFB1106100,2019YFE0119900)the National Natural Science Foundation of China(No.52076156)the Fundamental Research Funds for the Central Universities(No.2042020kf0194)。
文摘It is desirable to fabricate materials with adjustable physical properties that can be used in different industrial applications.Since the property of a material is highly dependent on its inner structure,the understanding of structure–property correlation is critical to the design of engineering materials.3D printing appears as a mature method to effectively produce micro-structured materials.In this work,we created different stainless-steel microstructures by adjusting the speed of 3D printing and studied the relationship between thermal property and printing speed.Our microstructure study demonstrates that highly porous structures appear at higher speeds,and there is a nearly linear relationship between porosity and printing speed.The thermal conductivity of samples fabricated by different printing speeds is characterized.Then,the correlation between porosity,thermal conductivity,and scanning speed is established.Based on this correlation,the thermal conductivity of a sample can be predicted from its printing speed.We fabricated a new sample at a different speed,and the thermal conductivity measurement agrees well with the value predicted from the correlation.To explore thermal transport physics,the effects of pore structure and temperature on the thermal performance of the printed block are also studied.Our work demonstrates that the combination of the 3D printing technique and the printing speed control can regulate the thermophysical properties of materials.
基金supported through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(2022M3H4A1A04096478)the support from the Supercomputing Center of Wuhan University。
文摘Electrocatalyst designs based on oxophilic foreign atoms are considered a promising approach for developing efficient pH-universal hydrogen evolution reaction(HER)electrocatalysts by overcoming the sluggish alkaline HER kinetics.Here,we design ternary transition metals-based nickel telluride(Mo WNi Te)catalysts consisting of high valence non-3d Mo and W metals and oxophilic Te as a first demonstration of non-precious heterogeneous electrocatalysts following the bifunctional mechanism.The Mo WNi Te showed excellent HER catalytic performance with overpotentials of 72,125,and 182 mV to reach the current densities of 10,100,and 1000 mA cm^(-2),respectively,and the corresponding Tafel slope of 47,52,and 58 mV dec-1in alkaline media,which is much superior to commercial Pt/C.Additionally,the HER performance of Mo WNi Te is well maintained up to 3000 h at the current density of 100 mA cm^(-2).It is further demonstrated that the Mo WNi Te exhibits remarkable HER activities with an overpotential of 45 mV(31 mV)and Tafel slope of 60 mV dec-1(34 mV dec-1)at 10 mA cm^(-2)in neutral(acid)media.The superior HER performance of Mo WNi Te is attributed to the electronic structure modulation,inducing highly active low valence states by the incorporation of high valence non-3d transition metals.It is also attributed to the oxophilic effect of Te,accelerating water dissociation kinetics through a bifunctional catalytic mechanism in alkaline media.Density functional theory calculations further reveal that such synergistic effects lead to reduced free energy for an efficient water dissociation process,resulting in remarkable HER catalytic performances within universal pH environments.
基金We are grateful for the financial support of National Key R&D Program of China(Nos.2O18YFEO2O5OOO and 2O19YFAO9O58OO for R W)Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning and China Scholarship Council(S X),National Natural Science Foundation of China(No.5157614 for Y Y)and US National Science Foundation(CBET193O866 for X W).
文摘Laser-assisted manufacturing(LAM)is a technique that performs machining of materials using a laser heating process.During the process,temperatures can rise above over 2000°C.As a result,it is crucial to explore the thermal behavior of materials under such high temperatures to understand the physics behind LAM and provide feedback for manufacturing optimization.Raman spectroscopy,which is widely used for structure characterization,can provide a novel way to measure temperature during LAM.In this review,we discuss the mechanism of Raman-based temperature probing,its calibration,and sources of uncertainty/error,and how to control them.We critically review the Raman-based temperature measurement considering the spatial resolution under near-field optical heating and surface structure-induced asymmetries.As another critical aspect of Raman-based temperature measurement,temporal resolution is also reviewed to cover various ways of realizing ultrafast thermal probing.We conclude with a detailed outlook on Raman-based temperature probing in LAM and issues that need special attention.
基金supported by the National Natural Science Foundation of China(Grant No.:52076156)Natural Sci-ence Foundation of Hubei Province(Grant No.:2021CFB120)+1 种基金Wuhan University Sino-Foreign Joint Scientific Research Project(Grant No.:WHUZZJJ202223)Fundamental Research Funds for Central Uni-versities(Grant No.:2042022kf1020).
文摘High-entropy alloys(HEAs)exhibit extraordinary physical properties such as superior strength-to-weight ratios and enhanced corrosion and oxidation resistance,making them potentially useful in energy storage and gener-ation industries.However,thermal and mechanical properties of HEAs with various compositions vary signifi-cantly.Furthermore,these properties have rarely been investigated simultaneously owing to material or instru-mentation limitations.Herein,we synthesize an HEA(AlCrNbSiTi)coating with a thickness of less than 2μm.We customize a frequency-domain photothermal testing system to characterize the thermal and mechanical proper-ties of the proposed coating with high accuracy.Owing to the large mixing enthalpy of the Al-Ti,Nb-Si,and Ti-Si pairs in the coating,its hardness and elastic modulus are 15.2 and 254.7 GPa,respectively,which are higher than those of previously reported HEAs.The thermal conductivity of the AlCrNbSiTi coating is characterized to be 2.90 W·m^(−1)·K^(−1),within the expected range and well explained by the free-electron consistency diversity and phonon scattering from the amorphous structure.Additionally,the coating exhibits adequate wear performance,with a wear rate of 5.4×10^(−8) mm^(3)·N^(−1)·m^(−1).This relatively low thermal conductivity,combined with extraordi-nary mechanical properties,makes the proposed material an excellent candidate as a protective coating material for nuclear reactor components which require high strength,irradiation resistance,and thermal protection.
文摘Semiconductors are promising in photoelectric and thermoelectric devices, for which the thermal transport properties are of particular interest. However, they have not been fully understood, especially when crystalline imperfections are present. Here, using cadmium telluride (CdTe) as an example, we illustrate how grain boundaries (GBs) affect the thermal transport properties of semiconductors. We develop a machine-learning force field from density functional theory calculations for predicting the lattice thermal conductivity (LTC) via equilibrium molecular dynamics simulations. The LTC of crystalline CdTe decreases with the relationship of κL~1/T in the simulation temperature range of 300 – 900 K, in which the isotropic LTC decreases from 3.34 to 0.23 W/ (m⋅K) due to the enhanced anharmonicity. More important, after introducing GBs, the LTC is suppressed in all directions, especially in the direction normal to the GB planes. More severe LTC suppression occurs in CdTe with Σ9 GB than that with Σ3 GB at 300 K, decreasing by 92.8% and 61.4% along the direction normal to the GB planes compared to the isotropic LTC of the crystalline CdTe, respectively. The decreased LTC is consistent with the weaker bonding near GB planes and lower shear modulus of the defective material. The analyses of the phonon dispersion curves, vibrational density of states, and phonon participation ratio indicate that the decreased LTC mainly arises from phonon scattering at GBs. Overall, our work highlights that GBs can greatly influence the LTC of semiconductors, thus providing a promising approach for thermal property design.
