Materials with ultralow thermal conductivity and good thermal stability are of great interest in numerous applications such as energy storage and conversion devices,and thermal insulation components.In this work,a fam...Materials with ultralow thermal conductivity and good thermal stability are of great interest in numerous applications such as energy storage and conversion devices,and thermal insulation components.In this work,a family of high-entropy Sm_(2)B_(2)O_(7)(B=Ti,Zr,Sn,Hf,Y,Yb,Nb,and Ta) oxides with highly disordered cations on the B-site has been synthesized by introducing large atomic-size mismatch,mass and charge disorder.Through tuning the composition,the high-entropy Sm_(2)B_(2)O_(7) oxides can be engineered from pyrochlore to fluorite structure,accompanied with an order-disorder transition.The pyrochlore Sm_(2)(Nb_(0.2)Sn_(0.2)Ti_(0.2)Y_(0.2)Zr_(0.2))_(2)O_(7) and fluorite Sm_(2)(Nb_(0.2)Ta_(0.2)Y_(0.2)Yb_(0.2)Zr_(0.2))_(2)O_(7) exhibit low thermal conductivities of 1.35 W·m^(-1)·K^(-1) and 1.23 W·m^(-1)·K^(-1),respectively,indicating their good thermal insulation.In addition,the high-entropy fluorite Sm_(2)(Nb_(0.2)Ta_(0.2)Y_(0.2)Yb_(0.2)Zr_(0.2))_(2)O_(7) also shows average thermal expansion coefficient of 10.2 × 10^(-6)℃^(-1) and high-temperature stability even after thermal exposure at 1600 °C in air for 30 h.These results indicate that the high-entropy Sm_(2)B_(2)O_(7)(B=Ti,Zr,Sn,Hf,Y,Yb,Nb,and Ta) can be promising candidates for thermal barrier coatings and thermally insulators.展开更多
The bulk metallic glass formation in the Cu-Zr-M ternary systems by alloying of a binary basic Cu6Zr5 cluster was inves-tigated,where M stands for Sn,Mo,Ta,Nb,Ag,Al and Ti.The Cu6Zr5 cluster is a capped Archimedean an...The bulk metallic glass formation in the Cu-Zr-M ternary systems by alloying of a binary basic Cu6Zr5 cluster was inves-tigated,where M stands for Sn,Mo,Ta,Nb,Ag,Al and Ti.The Cu6Zr5 cluster is a capped Archimedean antiprism that characterizes the local structure of the Cu10Zr7 crystalline phase.This cluster composition almost superposes with Cu-Zr eutectic Cu0.56Zr0.44.A se-ries of alloys along the cluster line(Cu6Zr5)1-xMx were examined for their glass forming abilities.Alloy rods with a diameter of 3 mm were prepared by copper mould suction casting method and analyzed by XRD and thermal analysis.The Cu-Zr based bulk metallic glasses were discovered with minor Nb,Sn,Mo,Ta additions(≤2at%)and Al,Ti,Ag(8at%≤concentration≤9at%).The alloying mechanism was discussed in the light of atomic size,cluster-linking structure and electron concentration factors.展开更多
A method of size exclusion chromatography coupled with ultraviolet spectrophotometry and off-line graphite furnace atomic absorption spectrometry was developed to assess the complexation properties of iron（Fe） and h...A method of size exclusion chromatography coupled with ultraviolet spectrophotometry and off-line graphite furnace atomic absorption spectrometry was developed to assess the complexation properties of iron（Fe） and humic acid（HA） in a water environment. The factors affecting the complexation of Fe and HA, such as ionic strength, pH, temperature and UV radiation, were investigated. The Fe–HA complex residence time was also studied. Experimental results showed that pH could influence the deprotonation of HA and hydrolysis of Fe, and thus affected the complexation of Fe and HA. The complexation was greatly disrupted by the presence of NaCl. Temperature had some influence on the complexation. The yield of Fe–HA complexes showed a small decrease at high levels of UV radiation, but the effect of UV radiation on Fe–HA complex formation at natural levels could be neglected. It took about 10 hr for the complexation to reach equilibrium, and the Fe–HA complex residence time was about 20 hr.Complexation of Fe and HA reached a maximum level under the conditions of pH 6, very low ionic strength, in the dark and at a water temperature of about 25°C, for 10 hr. It was suggested that the Fe–HA complex could form mainly in freshwater bodies and reach high levels in the warm season with mild sunlight radiation. With changing environmental parameters, such as at lower temperature in winter or higher pH and ionic strength in an estuary, the concentration of the Fe–HA complex would decrease.展开更多
In order to obtain appropriate spray pressure and enhance the spraying and dust removal efficiency, various factors including the dust characteristics, nozzle spraying angle, effective spraying range, water consumptio...In order to obtain appropriate spray pressure and enhance the spraying and dust removal efficiency, various factors including the dust characteristics, nozzle spraying angle, effective spraying range, water consumption and droplet size are taken into account. The dust characteristics from different mines and atomization parameters of different pressure nozzles were measured. It was found that the internal pressure of coal cutters and roadheaders should be kept at 2 MPa, which could ensure large droplet size, large spraying angle and low water consumption and hence realizing a large-area covering and capture for large particle dusts. However, the external spray pressure should be kept at 4 MPa for smaller droplet size and longer effective spraying range, leading to effective dust removal in the operator zone. The spray pressure of support moving, drawing opening, and stage loader on a fully mechanized caving face and stage loader on a fully mechanized driving face should be kept at 8 MPa, under which the nozzles have long effective spraying range, high water flow and small droplet size for the rapid capture of instantaneous, high-concentration and small size dust groups. From the applications on the caving and driving faces in the coal mines, it is indicated that the optimization of spray pressure in different spraying positions could effectively enhance dust removal efficiency. Selecting appropriate nozzles according to the dust characteristics at different positions is also favorable for dust removal efficiency. With the selected nozzles under optimal pressures, the removal rates of both total dust and respirable dust could reach over70%, showing a significant de-dusting effect.展开更多
The solid solubilities of 15 common alloying elements added to the Ll_2-type intermetallic compound Ni_3Si at 900°C have been estimated,and their substitution modes have been de- duced from the direction of solub...The solid solubilities of 15 common alloying elements added to the Ll_2-type intermetallic compound Ni_3Si at 900°C have been estimated,and their substitution modes have been de- duced from the direction of solubility lobe of the compound.It is shown that the alloying behaviours in Ni_3Si are determined by both size and electronic factors,i.e.,the substitution mode is governed by electronic configuration and solubility by the both.An interaction parameter is presented to describe quantitatively the influence of electronic configuration on substitution mode and the solubility limit can be successfully explained together with atom radius.展开更多
A Ballistic Modeling (BM) / Discrete Droplet Modeling (DDM) method is used to de- termine the characteristics of a solid cone pressure-swirl atomizer (Dyna Coin nozzle) . The charac- teristic of its liquid spray is of...A Ballistic Modeling (BM) / Discrete Droplet Modeling (DDM) method is used to de- termine the characteristics of a solid cone pressure-swirl atomizer (Dyna Coin nozzle) . The charac- teristic of its liquid spray is of considerable importance to the operation and performance of com- bustion systems. A two-dimensional spray model has been developed to simulate a continuous spray under steady-state condition . This model can simulate the resultant drop-sizc of atomization and reveal the effects of the important physical variables such as fuel injection pressure, air pressure(or density), co-axial air flow and fuel properties on the result of atomization process. Dimensional analysis is used to simulate the drop-size immcdiately after jet breakup and further breakup of the droplets is determined by testifying the critical condition of aerodynamics breakup i.e.(Wed)c= 8 / CD.展开更多
The degradation of vanadium-based alloys during hydrogen sorption cycles is closely linked to defect accumulation(e.g.,dislocation and lattice strain),yet the atomic-scale origins of such defects remain poorly underst...The degradation of vanadium-based alloys during hydrogen sorption cycles is closely linked to defect accumulation(e.g.,dislocation and lattice strain),yet the atomic-scale origins of such defects remain poorly understood.In present study,we reveal the crucial role of initial lattice distortion,quantified by the atomic size difference(δ),in the defect formation and accumulation of V-based alloys.Alloys with higherδvalues exhibit accelerated attenuation of reversible hydrogen capacity(13.22%forδ=4.32%vs.5.60%forδ=3.85%over 100 cycles),accompanied by increased plateau slope factors(Sf)and defect concentrations.High-resolution microscopy uncovers a two-stage defect evolution,associated with the generation of two types of nano-scale hierarchical structures.During the first cycle,nanograins with different spatial orientations show up,which geometrically leads to the formation of dislocations between the misoriented interfaces.In subsequent cycles,alternating nano-layered structures(1-2 nm thickness)gradually appear within the nanograins,resulting in the formation of subgrain boundaries accompanied with the local distortion and strains.These hierarchical nanostructures,driven byδ-dependent lattice distortion,are identified as the primary cause of the defects in alloys.This work provides a microstructure-guided strategy for designing durable hydrogen storage alloys by minimizing atomic size mismatch.展开更多
Solid solution strengthening(SSS)is widely used to enhance mechanical properties of metals.Originally developed for dilute alloys,classical SSS theories are presently challenged by the rise of complex concentrated all...Solid solution strengthening(SSS)is widely used to enhance mechanical properties of metals.Originally developed for dilute alloys,classical SSS theories are presently challenged by the rise of complex concentrated alloys(CCA)with nearly equiatomic compositions.Here,we propose and develop a method of“computational alchemy”in which interatomic interactions are modified to systematically vary two key physical parameters defining SSS-atomic size misfit and elastic stiffness misfit-over a maximally wide range of two misfits.The resulting alchemical alloys are subjected to massive(~10^(8) atoms)molecular dynamics(MD)simulations reproducing full complexity of plastic strength response.At variance with prevailing views,stiffness misfit is observed to contribute to SSS on par if not more than size misfit.Furthermore,depending on exactly how two misfits are combined,they result in synergistic(amplification)or antagonistic(compensation)effect on alloy strengthening.Unlike realCCAs in which each component element comes with its own specific size and stiffness,our alchemical model alloys span the space of two misfits continuously revealing trends in alloy strengthening unrecognized so far.Our study demonstrates unique value of intentionally unrealistic models for gaining deep physical insights into material behaviors that are difficult to reveal otherwise.展开更多
Our objective is to analyze the atomization processes of a pneumatic atomizer by measuring the size and velocity distributions of droplets in a liquid paint spray. The droplet size and velocity distributions have been...Our objective is to analyze the atomization processes of a pneumatic atomizer by measuring the size and velocity distributions of droplets in a liquid paint spray. The droplet size and velocity distributions have been determined at different axial positions in the spray; a mathematical description of how these quan- tities vary throughout the spray is then proposed. Additionally, the relative number density of droplets and the relative local mass flux are estimated.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 52072294, 51772237)。
文摘Materials with ultralow thermal conductivity and good thermal stability are of great interest in numerous applications such as energy storage and conversion devices,and thermal insulation components.In this work,a family of high-entropy Sm_(2)B_(2)O_(7)(B=Ti,Zr,Sn,Hf,Y,Yb,Nb,and Ta) oxides with highly disordered cations on the B-site has been synthesized by introducing large atomic-size mismatch,mass and charge disorder.Through tuning the composition,the high-entropy Sm_(2)B_(2)O_(7) oxides can be engineered from pyrochlore to fluorite structure,accompanied with an order-disorder transition.The pyrochlore Sm_(2)(Nb_(0.2)Sn_(0.2)Ti_(0.2)Y_(0.2)Zr_(0.2))_(2)O_(7) and fluorite Sm_(2)(Nb_(0.2)Ta_(0.2)Y_(0.2)Yb_(0.2)Zr_(0.2))_(2)O_(7) exhibit low thermal conductivities of 1.35 W·m^(-1)·K^(-1) and 1.23 W·m^(-1)·K^(-1),respectively,indicating their good thermal insulation.In addition,the high-entropy fluorite Sm_(2)(Nb_(0.2)Ta_(0.2)Y_(0.2)Yb_(0.2)Zr_(0.2))_(2)O_(7) also shows average thermal expansion coefficient of 10.2 × 10^(-6)℃^(-1) and high-temperature stability even after thermal exposure at 1600 °C in air for 30 h.These results indicate that the high-entropy Sm_(2)B_(2)O_(7)(B=Ti,Zr,Sn,Hf,Y,Yb,Nb,and Ta) can be promising candidates for thermal barrier coatings and thermally insulators.
基金This paper was financially supported by the National Natural Science Foundation of China(No.50401020,50671018 and 50631010)the Provincial Science and Technology Foundation of Liaoning(No.20061067).
文摘The bulk metallic glass formation in the Cu-Zr-M ternary systems by alloying of a binary basic Cu6Zr5 cluster was inves-tigated,where M stands for Sn,Mo,Ta,Nb,Ag,Al and Ti.The Cu6Zr5 cluster is a capped Archimedean antiprism that characterizes the local structure of the Cu10Zr7 crystalline phase.This cluster composition almost superposes with Cu-Zr eutectic Cu0.56Zr0.44.A se-ries of alloys along the cluster line(Cu6Zr5)1-xMx were examined for their glass forming abilities.Alloy rods with a diameter of 3 mm were prepared by copper mould suction casting method and analyzed by XRD and thermal analysis.The Cu-Zr based bulk metallic glasses were discovered with minor Nb,Sn,Mo,Ta additions(≤2at%)and Al,Ti,Ag(8at%≤concentration≤9at%).The alloying mechanism was discussed in the light of atomic size,cluster-linking structure and electron concentration factors.
基金supported by the National Natural Science Foundation of China (No. 41176075)
文摘A method of size exclusion chromatography coupled with ultraviolet spectrophotometry and off-line graphite furnace atomic absorption spectrometry was developed to assess the complexation properties of iron（Fe） and humic acid（HA） in a water environment. The factors affecting the complexation of Fe and HA, such as ionic strength, pH, temperature and UV radiation, were investigated. The Fe–HA complex residence time was also studied. Experimental results showed that pH could influence the deprotonation of HA and hydrolysis of Fe, and thus affected the complexation of Fe and HA. The complexation was greatly disrupted by the presence of NaCl. Temperature had some influence on the complexation. The yield of Fe–HA complexes showed a small decrease at high levels of UV radiation, but the effect of UV radiation on Fe–HA complex formation at natural levels could be neglected. It took about 10 hr for the complexation to reach equilibrium, and the Fe–HA complex residence time was about 20 hr.Complexation of Fe and HA reached a maximum level under the conditions of pH 6, very low ionic strength, in the dark and at a water temperature of about 25°C, for 10 hr. It was suggested that the Fe–HA complex could form mainly in freshwater bodies and reach high levels in the warm season with mild sunlight radiation. With changing environmental parameters, such as at lower temperature in winter or higher pH and ionic strength in an estuary, the concentration of the Fe–HA complex would decrease.
基金support from the National Natural Science Foundation of China (Nos.U1261205, 51474139 and 51204103)the Science and Technology Development Plan of Shandong Province (No.2013GSF12004)the Excellent Young Scientific Talents Project of Shandong University of Science and Technology (No.2014JQJH106)
文摘In order to obtain appropriate spray pressure and enhance the spraying and dust removal efficiency, various factors including the dust characteristics, nozzle spraying angle, effective spraying range, water consumption and droplet size are taken into account. The dust characteristics from different mines and atomization parameters of different pressure nozzles were measured. It was found that the internal pressure of coal cutters and roadheaders should be kept at 2 MPa, which could ensure large droplet size, large spraying angle and low water consumption and hence realizing a large-area covering and capture for large particle dusts. However, the external spray pressure should be kept at 4 MPa for smaller droplet size and longer effective spraying range, leading to effective dust removal in the operator zone. The spray pressure of support moving, drawing opening, and stage loader on a fully mechanized caving face and stage loader on a fully mechanized driving face should be kept at 8 MPa, under which the nozzles have long effective spraying range, high water flow and small droplet size for the rapid capture of instantaneous, high-concentration and small size dust groups. From the applications on the caving and driving faces in the coal mines, it is indicated that the optimization of spray pressure in different spraying positions could effectively enhance dust removal efficiency. Selecting appropriate nozzles according to the dust characteristics at different positions is also favorable for dust removal efficiency. With the selected nozzles under optimal pressures, the removal rates of both total dust and respirable dust could reach over70%, showing a significant de-dusting effect.
文摘The solid solubilities of 15 common alloying elements added to the Ll_2-type intermetallic compound Ni_3Si at 900°C have been estimated,and their substitution modes have been de- duced from the direction of solubility lobe of the compound.It is shown that the alloying behaviours in Ni_3Si are determined by both size and electronic factors,i.e.,the substitution mode is governed by electronic configuration and solubility by the both.An interaction parameter is presented to describe quantitatively the influence of electronic configuration on substitution mode and the solubility limit can be successfully explained together with atom radius.
文摘A Ballistic Modeling (BM) / Discrete Droplet Modeling (DDM) method is used to de- termine the characteristics of a solid cone pressure-swirl atomizer (Dyna Coin nozzle) . The charac- teristic of its liquid spray is of considerable importance to the operation and performance of com- bustion systems. A two-dimensional spray model has been developed to simulate a continuous spray under steady-state condition . This model can simulate the resultant drop-sizc of atomization and reveal the effects of the important physical variables such as fuel injection pressure, air pressure(or density), co-axial air flow and fuel properties on the result of atomization process. Dimensional analysis is used to simulate the drop-size immcdiately after jet breakup and further breakup of the droplets is determined by testifying the critical condition of aerodynamics breakup i.e.(Wed)c= 8 / CD.
基金granted by the National Key R&D Program of China(No.2022YFB3803700)Sichuan Science and Technology Program(No.PG-PGFG-JFKF23-000009-0).
文摘The degradation of vanadium-based alloys during hydrogen sorption cycles is closely linked to defect accumulation(e.g.,dislocation and lattice strain),yet the atomic-scale origins of such defects remain poorly understood.In present study,we reveal the crucial role of initial lattice distortion,quantified by the atomic size difference(δ),in the defect formation and accumulation of V-based alloys.Alloys with higherδvalues exhibit accelerated attenuation of reversible hydrogen capacity(13.22%forδ=4.32%vs.5.60%forδ=3.85%over 100 cycles),accompanied by increased plateau slope factors(Sf)and defect concentrations.High-resolution microscopy uncovers a two-stage defect evolution,associated with the generation of two types of nano-scale hierarchical structures.During the first cycle,nanograins with different spatial orientations show up,which geometrically leads to the formation of dislocations between the misoriented interfaces.In subsequent cycles,alternating nano-layered structures(1-2 nm thickness)gradually appear within the nanograins,resulting in the formation of subgrain boundaries accompanied with the local distortion and strains.These hierarchical nanostructures,driven byδ-dependent lattice distortion,are identified as the primary cause of the defects in alloys.This work provides a microstructure-guided strategy for designing durable hydrogen storage alloys by minimizing atomic size mismatch.
基金funding support from the ASC PEM program at Lawrence Livermore National Laboratory. Computing support for this work came from LLNL Institutional Computing Grand Challenge program. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
文摘Solid solution strengthening(SSS)is widely used to enhance mechanical properties of metals.Originally developed for dilute alloys,classical SSS theories are presently challenged by the rise of complex concentrated alloys(CCA)with nearly equiatomic compositions.Here,we propose and develop a method of“computational alchemy”in which interatomic interactions are modified to systematically vary two key physical parameters defining SSS-atomic size misfit and elastic stiffness misfit-over a maximally wide range of two misfits.The resulting alchemical alloys are subjected to massive(~10^(8) atoms)molecular dynamics(MD)simulations reproducing full complexity of plastic strength response.At variance with prevailing views,stiffness misfit is observed to contribute to SSS on par if not more than size misfit.Furthermore,depending on exactly how two misfits are combined,they result in synergistic(amplification)or antagonistic(compensation)effect on alloy strengthening.Unlike realCCAs in which each component element comes with its own specific size and stiffness,our alchemical model alloys span the space of two misfits continuously revealing trends in alloy strengthening unrecognized so far.Our study demonstrates unique value of intentionally unrealistic models for gaining deep physical insights into material behaviors that are difficult to reveal otherwise.
文摘Our objective is to analyze the atomization processes of a pneumatic atomizer by measuring the size and velocity distributions of droplets in a liquid paint spray. The droplet size and velocity distributions have been determined at different axial positions in the spray; a mathematical description of how these quan- tities vary throughout the spray is then proposed. Additionally, the relative number density of droplets and the relative local mass flux are estimated.
