The almost completely dense copper was prepared by ultrafine copper powder prepared with both methods of electrolysis and novel water-gas atomization through cold isostatic pressing(CIP)and sintering under atmospheric...The almost completely dense copper was prepared by ultrafine copper powder prepared with both methods of electrolysis and novel water-gas atomization through cold isostatic pressing(CIP)and sintering under atmospheric hydrogen.Fine copper powder possesses the higher sintering driving force,thereby promoting shrinkage and densification during the sintering process.The grain size of sintered samples by electrolytic copper powder is smaller than that prepared by the atomized copper powder,and the twin crystals are particularly prone to forming in the former sintered microstructure due to the raw powder with low oxygen content and high residual stress originating from the CIP process.The relative density of samples by electrolytic and atomized powder at 1000℃ sintering temperature achieves 99.3%and 97.4%,respectively,significantly higher than that of the powder metallurgy copper parts reported in the literature.Correspondingly,the ultimate tensile strength and yield strength of samples by both kinds of copper powder are approximately similar,while the elongation of the sintered sample by the electrolytic powder(60%)is apparently higher than the atomized powder(44%).The superior performance of samples fabricated by electrolytic powder is inferred from the full density and low oxygen level for there is no cuprous oxide in the grain boundaries.展开更多
In order to enhance the atomization efficiency of atomizer, a new type of wind-spray dust controller combining the rotary-atomization and colliding broken of droplets was designed by the method of opening the water ci...In order to enhance the atomization efficiency of atomizer, a new type of wind-spray dust controller combining the rotary-atomization and colliding broken of droplets was designed by the method of opening the water circulation within the blades. The experiment test for dust controller was conducted by adjusting the following parameters: rotating speed, diversion hole-exit diameter, and colliding tooth angle. Results show that the atomization efficiency increases firstly then decreases with them. And the optimal parameters are obtained with rotating speed 1500-2200 r/min, diversion hole-exit diameter 2-2.5 mm and colliding tooth angle 30°-40°, and under these conditions the corresponding atomization efficiency tops to 95%. Then, the atomization situation under the optimal parameters is held from the aspect of simulation internal flow field and the results of droplet size(30-80 μm) are got, which indicates that the conclusion on the optimized parameters of dust controller is reasonable. The collecting efficiencies of different dust concentrations are determined, ranging from 85% to 98.4%, which shows that the designed dust controller can obtain a good atomizing effect and achieve well dustfall efficiency for the wetting dust control of coal mine.展开更多
Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,...Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,mechanical properties of Al-Si alloys were investigated by XRD, SEM, a hydrostatic balance, an automatic micro hardness tester and a universal tensile testing machine. The results showed that homogenous distribution of ultrafine primary Si and high density of alloys can be obtained at holding time of 30 min. Compared with primary Si(3.7 μm)fabricated by gas atomization, the average size increased from 5.17 to 7.72 μm with the increase of holding time during SPS process. Overall, the relative density, maximum tensile strength and Vickers hardness of 94.9%, 205 MPa and HV;196.86 were achieved at holding time of 30 min, respectively. In addition, all the diffraction peaks were corresponded to α-Al or β-Si and no other phase can be detected. Finally, the densification process of SPS was also discussed.展开更多
In the present study,electrostatic atomization(EA)behavior of several test liquids having much higher viscosities(1 400 mPa·s)than have previously been studied was investigated by spraying at a series of applied ...In the present study,electrostatic atomization(EA)behavior of several test liquids having much higher viscosities(1 400 mPa·s)than have previously been studied was investigated by spraying at a series of applied voltages and flow rates.The results showed that to obtain stable cone-jet mode spraying and hence gain better monodispersity of droplets,electrical conductivity,viscosity and surface tension of the liquid are important controlling factors.The stable cone-jet mode could be easily established for liquids having shear viscosities in the range from 80 to 1 400 mPa·s and surface tensions below 65 mN·m-1.In contrast,methylcellulose aqueous solutions with shear viscosities ranging from 10 to 540 mPa·s and moderate surface tensions(50~56 mN·m-1)generated more complicated spraying modes.However,fine TiO2 powder(a few micrometers in size)could be prepared using the EA method from its precursor solutions.展开更多
The design of cost-effective and efficient metal-free carbon-based catalysts for the hydrogen evolution reaction(HER)is of great significance for increasing the production of clean hydrogen by the electrolysis of alka...The design of cost-effective and efficient metal-free carbon-based catalysts for the hydrogen evolution reaction(HER)is of great significance for increasing the production of clean hydrogen by the electrolysis of alkaline water.Precise control of the electronic structure by heteroatom doping has proven to be efficient for increasing catalytic activity.Nevertheless,both the structural characteristics and the underlying mechanism are not well understood,especially for doping with two different atoms,thus limiting the use of these catalysts.We report the production of phosphorus and nitrogen co-doped hollow carbon nanospheres(HCNs)by the copolymerization of pyrrole and aniline at a Triton X-100 micelle-interface,followed by doping with phytic acid and carbonization.The unique pore structure and defect-rich framework of the HCNs expose numerous active sites.Crucially,the combined effect of graphitic nitrogen and phosphorus-carbon bonds modulate the local electronic structure of adjacent C atoms and facilitates electron transfer.As a res-ult,the HCN carbonized at 1100°C exhibited superior HER activity and an outstanding stability(70 h at a current density of 10 mA cm^(−2))in alkaline water,because of the large number of graphitic nitrogen and phosphorus-carbon bonds.展开更多
Broadband transparent films play a pivotal role in various applications such as lenses and solar cells,particularly porous structured transparent films exhibit significant potential.This study investigates a porous Si...Broadband transparent films play a pivotal role in various applications such as lenses and solar cells,particularly porous structured transparent films exhibit significant potential.This study investigates a porous SiO_(2) refractive index gradient anti-reflective film prepared by atomic layer deposition(ALD).A porous SiO_(2) film with gradual porosity was obtained by phosphoric acid etching of Al_(2)O_(3)/SiO_(2) multilayers with gradient Al2O3 ratios,achieving a gradual decrease in refractive index from the substrate to the surface.The film exhibited an average transmittance as high as 97.8%within the wavelength range from 320 nm to 1200 nm.The environmental adaptability was further enhanced by surface modification using rare earth oxide(REO)La_(2)O_(3),resulting in formation of a lotus leaf-like structure and achieving a water contact angle of 100.0°.These data proved that the modification significantly improved hydrophobic self-cleaning capability while maintaining exceptional transparency of the film.The surface structure of the modified film remained undamaged even after undergoing wipe testing,demonstrating its excellent surface durability.展开更多
Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Her...Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Herein,with crystal and atomic structures of the self-assembled PDI revealed from the X-ray diffraction pattern,the electronic structure is theoretically illustrated by the first-principles density functional theory calculations,suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution over PDI.It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis.The calculations of reaction free energy changes indicate that the oxygen evolution reaction should follow the reaction pathway of H_(2)O→^(*)OH→^(*)O→^(*)OOH→^(*)O_(2)with an overpotential of 0.81 V.Through an in-depth theoretical computational analysis in the atomic and electronic structures,the origin of photocatalytic oxygen evolution activity for PDI is well illustrated,which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.展开更多
This work presents a method for the three-dimensional localization of individual shallow NV center in diamond,leveraging the near-field quenching effect of a gold tip.Our experimental setup involves the use of an atom...This work presents a method for the three-dimensional localization of individual shallow NV center in diamond,leveraging the near-field quenching effect of a gold tip.Our experimental setup involves the use of an atomic force microscope to precisely move the gold tip close to the NV center,while simultaneously employing a home-made confocal microscope to monitor the fluorescence of the NV center.This approach allows for lateral super-resolution,achieving a full width at half maximum(FWHM)of 38.0 nm and a location uncertainty of 0.7 nm.Additionally,we show the potential of this method for determining the depth of the NV centers.We also attempt to determine the depth of the NV centers in combination with finite-difference time-domain(FDTD)simulations.Compared to other depth determination methods,this approach allows for simultaneous lateral and longitudinal localization of individual NV centers,and holds promise for facilitating manipulation of the local environment surrounding the NV center.展开更多
Electrocatalytic reduction of carbon dioxide(CO_(2))to carbon monoxide(CO)is an effective strategy to achieve carbon neutrality.High selective and low-cost catalysts for the electrocatalytic reduction of CO_(2)have re...Electrocatalytic reduction of carbon dioxide(CO_(2))to carbon monoxide(CO)is an effective strategy to achieve carbon neutrality.High selective and low-cost catalysts for the electrocatalytic reduction of CO_(2)have received increasing attention.In contrast to the conventional tube furnace method,the high-temperature shock(HTS)method enables ultra-fast thermal processing,superior atomic efficiency,and a streamlined synthesis protocol,offering a simplified method for the preparation of high-performance single-atom catalysts(SACs).The reports have shown that nickel-based SACs can be synthesized quickly and conveniently using the HTS method,making their application in CO_(2)reduction reactions(CO_(2)RR)a viable and promising avenue for further exploration.In this study,the effect of heating temperature,metal loading and different nitrogen(N)sources on the catalyst morphology,coordination environment and electrocatalytic performance were investigated.Under optimal conditions,0.05Ni-DCD-C-1050 showed excellent performance in reducing CO_(2)to CO,with CO selectivity close to 100%(−0.7 to−1.0 V vs RHE)and current density as high as 130 mA/cm^(2)(−1.1 V vs RHE)in a flow cell under alkaline environment.展开更多
Effects of ultrasonic bonding parameters on atomic diffusion, microstructure at the Al-Au interface, and shear strength of Al-Au ultrasonic bonding were investigated by the combining experiments and finite element (FE...Effects of ultrasonic bonding parameters on atomic diffusion, microstructure at the Al-Au interface, and shear strength of Al-Au ultrasonic bonding were investigated by the combining experiments and finite element (FE) simulation. The quantitative model of atomic diffusion, which is related to the ultrasonic bonding parameters, time and distance, is established to calculate the atomic diffusion of the Al-Au interface. The maximum relative error between the calculated and experimental fraction of Al atom is 7.35%, indicating high prediction accuracy of this model. During the process of ultrasonic bonding, Au8Al3 is the main intermetallic compound (IMC) at the Al-Au interface. With larger bonding forces, higher ultrasonic powers and longer bonding time, it is more difficult to remove the oxide particles from the Al-Au interface, which hinders the atomic diffusion. Therefore, the complicated stress state and the existence of oxide particles both promotes the formation of holes. The shear strength of Al-Au ultrasonic bonding increases with increasing bonding force, ultrasonic power and bonding time. However, combined with the presence of holes at especial parameters, the optimal ultrasonic bonding parameter is confirmed to be a bonding force of 23 gf, ultrasonic power of 75 mW and bonding time of 21 ms.展开更多
Materials with low thermal conductivity are applied extensively in energy management,and breaking the amorphous limits of thermal conductivity to solids has attracted widespread attention from scientists.Doping is a c...Materials with low thermal conductivity are applied extensively in energy management,and breaking the amorphous limits of thermal conductivity to solids has attracted widespread attention from scientists.Doping is a common strategy for achieving low thermal conductivity that can offer abundant scattering centers in which heavier dopants always result in lower phonon group velocities and lower thermal conductivities.However,the amount of equivalent heavyatom single dopant available is limited.Unfortunately,nonequivalent heavy dopants have finite solubility because of charge imbalance.Here,we propose a charge balance strategy for SnS by substituting Sn2+with Ag^(+)and heavy Bi^(3+),improving the doping limit of Ag from 2%to 3%.Ag and Bi codoping increases the point defect concentration and introduces abundant boundaries simultaneously,scattering the phonons at both the atomic scale and nanoscale.The thermal conductivity of Ag0.03Bi0.03Sn0.94S decreased to 0.535 W·m^(−1)·K^(−1)at room temperature and 0.388 W·m^(−1)·K^(−1)at 275°C,which is below the amorphous limit of 0.450 W·m^(−1)·K^(−1)for SnS.This strategy offers a simple way to enhance the doping limit and achieve ultralow thermal conductivity in solids below the amorphous limit without precise structural modification.展开更多
In this paper,we study the accuracy of delay-Doppler parameter estimation of targets in a passive radar using orthogonal frequency division multiplexing(OFDM)signal.A coarse-fine joint estimation method is proposed to...In this paper,we study the accuracy of delay-Doppler parameter estimation of targets in a passive radar using orthogonal frequency division multiplexing(OFDM)signal.A coarse-fine joint estimation method is proposed to achieve better estimation accuracy of target parameters without excessive computational burden.Firstly,the modulation symbol domain(MSD)method is used to roughly estimate the delay and Doppler of targets.Then,to obtain high-precision Doppler estimation,the atomic norm(AN)based on the multiple measurement vectors(MMV)model(MMV-AN)is used to manifest the signal sparsity in the continuous Doppler domain.At the same time,a reference signal compensation(RSC)method is presented to obtain highprecision delay estimation.Simulation results based on the OFDM signal show that the coarse-fine joint estimation method based on AN-RSC can obtain a more accurate estimation of target parameters compared with other algorithms.In addition,the proposed method also possesses computational advantages compared with the joint parameter estimation.展开更多
Formic acid oxidation reaction(FAOR),as the anodic reaction in direct formic acid fuel cells,has attracted much attention but increasing the mass activity and stability of catalysts still face a bottleneck to meet the...Formic acid oxidation reaction(FAOR),as the anodic reaction in direct formic acid fuel cells,has attracted much attention but increasing the mass activity and stability of catalysts still face a bottleneck to meet the requirements of practical applications.In the past decades,researchers developed many strategies to fix these issues by improving the structure of catalysts and the newly raised single atom catalysts(SACs)show the high mass activity and stability in FAOR.This review first summarized the reaction mechanism involved in FAOR.The mass activity as well as stability of catalysts reported in the past five years have been outlined.Moreover,the synthetic strategies to improve the catalytic performance of catalysts are also reviewed in this work.Finally,we proposed the research directions to guide the rational design of new FAOR catalysts in the future.展开更多
new coordination polymer {[Zn(CF3COO)2(C5H5ON)]·H2O}n was synthesized based on the reaction of zinc(Ⅱ) trifluoroacetate and 3-hydroxypyridine(C5H5ON) in methanol medium for the first time. The structure of the c...new coordination polymer {[Zn(CF3COO)2(C5H5ON)]·H2O}n was synthesized based on the reaction of zinc(Ⅱ) trifluoroacetate and 3-hydroxypyridine(C5H5ON) in methanol medium for the first time. The structure of the coordination polymer was confirmed by IR, 1H NMR, elemental analysis and thermal analysis. The crystal structure of the coordination polymer was also determined by X-ray single crystal diffraction. The crystal belongs to monoclinic system with space group P21/m, and crystallographic data of the coordination polymer are: a= 0.863 1(4) nm, b=0.717 7(3) nm, c=1.116 4(5) nm, α=γ=90°, β=107.542(6)°, V=0.659 4(5) nm3; Dc=2.037 g·cm-3; Z=2; F(000)=400; μ=1.969 mm-1. Zinc(Ⅱ) atom lies at the center of an octahedron formed by the coordination of zinc atom and six O atoms which come from four different trifluoroacetate ions and two different 3-hydroxypyridine molecules where each trifluoroacetate ion and 3-hydroxypyridine are coordinated to two different zinc ions to form coordination polymer. CCDC: 253909.展开更多
A new binuclear copper(Ⅱ) complex, [Cu2(phen)2(H2O)2( μ2-C2O4)](NO3)2, has been synthesized and characterized by elemental analysis, IR and UV-Vis spectrum. Its crystal structure was determined by single crystal X-r...A new binuclear copper(Ⅱ) complex, [Cu2(phen)2(H2O)2( μ2-C2O4)](NO3)2, has been synthesized and characterized by elemental analysis, IR and UV-Vis spectrum. Its crystal structure was determined by single crystal X-ray diffraction techniques. Crystal data: monoclinic, space group P21/c, a=0.712 21(8) nm, b=1.170 93(14) nm, c=1.783 7(2) nm, β=111.828(2)°, and V=1.380 8(3) nm3, Dc=1.769 Mg·m-3, Z=2, F(000)=744, R1=0.025 4, wR2=0.069 5, Gof=1.077, Δρ=328^-455 e·nm-3. The complex is packed by one centrosymmetry binuclear copper(Ⅱ) unit, oxalate dianion and NO3- anion. In the molecule structure of the title complex, two Cu(Ⅱ) ions are bridged by oxalate dianion and each Cu(Ⅱ) ions coordinates with two nitrogen atoms from 1,10-phenanthroline ligand and one oxygen atom from water to form a five-coordinate distorted square-pyramidal configuration. The hydrogen bonds are observed between coordinated water molecules and NO3- anions. The analysis of the crystal structure indicates that the complex has a two-dimensional stacking network structure, which is formed by intramolecular hydrogen bonds, intermolecular hydrogen bonds and stacking effect of aromatic ring. CCDC: 255345.展开更多
The μ-oxygen-bis[tri(p-fluorobenzyl)tin] was synthesized. The structure were characterized by elementary analysis, IR and 1H NMR and the crystal structure were determined by X-ray single crystal diffraction. The crys...The μ-oxygen-bis[tri(p-fluorobenzyl)tin] was synthesized. The structure were characterized by elementary analysis, IR and 1H NMR and the crystal structure were determined by X-ray single crystal diffraction. The crystal of the title compound belongs to rhombohedral with space group R, a=1.346 4(4), b=1.346 4(4), c=1.772 9(7) nm, α=90°, β=90°, γ=120°, Z=3, V=2.783 2(15) nm3, Dc=1.625 g·cm-3, μ(Mo Kα)=1.408 mm-1, S=1.088, F(000)=1 350, R1=0.027 5, wR2=0.065 9. In compound, the tin atom has a distorted tetrahedral coordination configuration. CCDC: 257079.展开更多
Diorganotin(Ⅳ) compound [(p-CNC6H4CH2)2Sn(C9H7N3O3)(H2O)]2 was synthesized by the reaction of tri-p-cyanobenzyltin chloride with Schiff base ligand pyruvic acid isonicotinyl hydrazone. The compound was characterized ...Diorganotin(Ⅳ) compound [(p-CNC6H4CH2)2Sn(C9H7N3O3)(H2O)]2 was synthesized by the reaction of tri-p-cyanobenzyltin chloride with Schiff base ligand pyruvic acid isonicotinyl hydrazone. The compound was characterized by elemental analysis, IR, 1H NMR. The crystal structure was determined by X-ray single crystal diffraction. The crystal belongs to monoclinic space group C2/c, with a=3.143 1(3) nm, b=0.989 99(10) nm, c=1.785 68(18) nm, β=114.908 0(13)°, V=5.039 6(9) nm3, Z=4, μ=1.054 mm-1, Dc=1.513 Mg·m-3, F(000)=2 304, R=0.042 8, wR=0.090 3, GOF=0.997. In this compound, the Sn atom exists in a distorted octahedral coordination environment in which one water molecule, one tridentate pyruvic acid isonicotinyl hydrazone ligand, and two trans p-cyanobenzyl groups coordinate to each Sn center, the angle of the axial C10-Sn1-C18 is 166.1(2)°. Two molecules form a weak-bridged dimmer with weak interactions of Sn...O bonding and hydrogen bonds. CCDC: 270796.展开更多
基金Project(92066205)supported by the National Natural Science Foundation of ChinaProject(2019-Z10)supported by the State Key Lab for Advanced Metals and Materials of ChinaProject(FRF-MP-20-52)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The almost completely dense copper was prepared by ultrafine copper powder prepared with both methods of electrolysis and novel water-gas atomization through cold isostatic pressing(CIP)and sintering under atmospheric hydrogen.Fine copper powder possesses the higher sintering driving force,thereby promoting shrinkage and densification during the sintering process.The grain size of sintered samples by electrolytic copper powder is smaller than that prepared by the atomized copper powder,and the twin crystals are particularly prone to forming in the former sintered microstructure due to the raw powder with low oxygen content and high residual stress originating from the CIP process.The relative density of samples by electrolytic and atomized powder at 1000℃ sintering temperature achieves 99.3%and 97.4%,respectively,significantly higher than that of the powder metallurgy copper parts reported in the literature.Correspondingly,the ultimate tensile strength and yield strength of samples by both kinds of copper powder are approximately similar,while the elongation of the sintered sample by the electrolytic powder(60%)is apparently higher than the atomized powder(44%).The superior performance of samples fabricated by electrolytic powder is inferred from the full density and low oxygen level for there is no cuprous oxide in the grain boundaries.
基金Project(U1261107)supported by the Joint Funds of the National Natural Science Foundation of China
文摘In order to enhance the atomization efficiency of atomizer, a new type of wind-spray dust controller combining the rotary-atomization and colliding broken of droplets was designed by the method of opening the water circulation within the blades. The experiment test for dust controller was conducted by adjusting the following parameters: rotating speed, diversion hole-exit diameter, and colliding tooth angle. Results show that the atomization efficiency increases firstly then decreases with them. And the optimal parameters are obtained with rotating speed 1500-2200 r/min, diversion hole-exit diameter 2-2.5 mm and colliding tooth angle 30°-40°, and under these conditions the corresponding atomization efficiency tops to 95%. Then, the atomization situation under the optimal parameters is held from the aspect of simulation internal flow field and the results of droplet size(30-80 μm) are got, which indicates that the conclusion on the optimized parameters of dust controller is reasonable. The collecting efficiencies of different dust concentrations are determined, ranging from 85% to 98.4%, which shows that the designed dust controller can obtain a good atomizing effect and achieve well dustfall efficiency for the wetting dust control of coal mine.
基金Project(18JS060) supported by the Shaanxi Key Laboratory of Nano-materials and Technology,ChinaProject(2018JQ5087) supported by Natural Science Basic Research Plan of Shaanxi Province,China。
文摘Hypereutectic Al-40 wt.%Si alloys were fabricated by the combination of gas atomization and spark plasma sintering(SPS) technology. The effects of holding time(15-60 min) on phase composition, microstructure, density,mechanical properties of Al-Si alloys were investigated by XRD, SEM, a hydrostatic balance, an automatic micro hardness tester and a universal tensile testing machine. The results showed that homogenous distribution of ultrafine primary Si and high density of alloys can be obtained at holding time of 30 min. Compared with primary Si(3.7 μm)fabricated by gas atomization, the average size increased from 5.17 to 7.72 μm with the increase of holding time during SPS process. Overall, the relative density, maximum tensile strength and Vickers hardness of 94.9%, 205 MPa and HV;196.86 were achieved at holding time of 30 min, respectively. In addition, all the diffraction peaks were corresponded to α-Al or β-Si and no other phase can be detected. Finally, the densification process of SPS was also discussed.
文摘In the present study,electrostatic atomization(EA)behavior of several test liquids having much higher viscosities(1 400 mPa·s)than have previously been studied was investigated by spraying at a series of applied voltages and flow rates.The results showed that to obtain stable cone-jet mode spraying and hence gain better monodispersity of droplets,electrical conductivity,viscosity and surface tension of the liquid are important controlling factors.The stable cone-jet mode could be easily established for liquids having shear viscosities in the range from 80 to 1 400 mPa·s and surface tensions below 65 mN·m-1.In contrast,methylcellulose aqueous solutions with shear viscosities ranging from 10 to 540 mPa·s and moderate surface tensions(50~56 mN·m-1)generated more complicated spraying modes.However,fine TiO2 powder(a few micrometers in size)could be prepared using the EA method from its precursor solutions.
基金financially supported by the project of the National Natural Science Foundation of China(52322203)the Key Research and Development Program of Shaanxi Province(2024GHZDXM-21)。
文摘The design of cost-effective and efficient metal-free carbon-based catalysts for the hydrogen evolution reaction(HER)is of great significance for increasing the production of clean hydrogen by the electrolysis of alkaline water.Precise control of the electronic structure by heteroatom doping has proven to be efficient for increasing catalytic activity.Nevertheless,both the structural characteristics and the underlying mechanism are not well understood,especially for doping with two different atoms,thus limiting the use of these catalysts.We report the production of phosphorus and nitrogen co-doped hollow carbon nanospheres(HCNs)by the copolymerization of pyrrole and aniline at a Triton X-100 micelle-interface,followed by doping with phytic acid and carbonization.The unique pore structure and defect-rich framework of the HCNs expose numerous active sites.Crucially,the combined effect of graphitic nitrogen and phosphorus-carbon bonds modulate the local electronic structure of adjacent C atoms and facilitates electron transfer.As a res-ult,the HCN carbonized at 1100°C exhibited superior HER activity and an outstanding stability(70 h at a current density of 10 mA cm^(−2))in alkaline water,because of the large number of graphitic nitrogen and phosphorus-carbon bonds.
文摘Broadband transparent films play a pivotal role in various applications such as lenses and solar cells,particularly porous structured transparent films exhibit significant potential.This study investigates a porous SiO_(2) refractive index gradient anti-reflective film prepared by atomic layer deposition(ALD).A porous SiO_(2) film with gradual porosity was obtained by phosphoric acid etching of Al_(2)O_(3)/SiO_(2) multilayers with gradient Al2O3 ratios,achieving a gradual decrease in refractive index from the substrate to the surface.The film exhibited an average transmittance as high as 97.8%within the wavelength range from 320 nm to 1200 nm.The environmental adaptability was further enhanced by surface modification using rare earth oxide(REO)La_(2)O_(3),resulting in formation of a lotus leaf-like structure and achieving a water contact angle of 100.0°.These data proved that the modification significantly improved hydrophobic self-cleaning capability while maintaining exceptional transparency of the film.The surface structure of the modified film remained undamaged even after undergoing wipe testing,demonstrating its excellent surface durability.
基金supported by National Natural Science Foundation of China(No.523B2070,No.52225606).
文摘Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Herein,with crystal and atomic structures of the self-assembled PDI revealed from the X-ray diffraction pattern,the electronic structure is theoretically illustrated by the first-principles density functional theory calculations,suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution over PDI.It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis.The calculations of reaction free energy changes indicate that the oxygen evolution reaction should follow the reaction pathway of H_(2)O→^(*)OH→^(*)O→^(*)OOH→^(*)O_(2)with an overpotential of 0.81 V.Through an in-depth theoretical computational analysis in the atomic and electronic structures,the origin of photocatalytic oxygen evolution activity for PDI is well illustrated,which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.
基金supported by the National Natural Science Foundation of China(T2325023,92265204,12104447)the National Key R&D Program of China(2023YFF0718400)+1 种基金the Innovation Program for Quantum Science and Technology(2021ZD0302200)the Fundamental Research Funds for the Central Universities。
文摘This work presents a method for the three-dimensional localization of individual shallow NV center in diamond,leveraging the near-field quenching effect of a gold tip.Our experimental setup involves the use of an atomic force microscope to precisely move the gold tip close to the NV center,while simultaneously employing a home-made confocal microscope to monitor the fluorescence of the NV center.This approach allows for lateral super-resolution,achieving a full width at half maximum(FWHM)of 38.0 nm and a location uncertainty of 0.7 nm.Additionally,we show the potential of this method for determining the depth of the NV centers.We also attempt to determine the depth of the NV centers in combination with finite-difference time-domain(FDTD)simulations.Compared to other depth determination methods,this approach allows for simultaneous lateral and longitudinal localization of individual NV centers,and holds promise for facilitating manipulation of the local environment surrounding the NV center.
基金supported by the National Key R&D Program of China(2024YFB4106400)National Natural Science Foundation of China(22209200,52302331)。
文摘Electrocatalytic reduction of carbon dioxide(CO_(2))to carbon monoxide(CO)is an effective strategy to achieve carbon neutrality.High selective and low-cost catalysts for the electrocatalytic reduction of CO_(2)have received increasing attention.In contrast to the conventional tube furnace method,the high-temperature shock(HTS)method enables ultra-fast thermal processing,superior atomic efficiency,and a streamlined synthesis protocol,offering a simplified method for the preparation of high-performance single-atom catalysts(SACs).The reports have shown that nickel-based SACs can be synthesized quickly and conveniently using the HTS method,making their application in CO_(2)reduction reactions(CO_(2)RR)a viable and promising avenue for further exploration.In this study,the effect of heating temperature,metal loading and different nitrogen(N)sources on the catalyst morphology,coordination environment and electrocatalytic performance were investigated.Under optimal conditions,0.05Ni-DCD-C-1050 showed excellent performance in reducing CO_(2)to CO,with CO selectivity close to 100%(−0.7 to−1.0 V vs RHE)and current density as high as 130 mA/cm^(2)(−1.1 V vs RHE)in a flow cell under alkaline environment.
基金Project(2022YFB3707201) supported by the National Key R&D Program of ChinaProject(U2341254) supported by the Ye Qisun Science Foundation of National Natural Science Foundation of China+1 种基金Projects(0604022GH0202143,0604022SH0201143) supported by the NPU Aoxiang Distinguished Young Scholars,ChinaProject supported by the Funding of Young Top-notch Talent of the National Ten Thousand Talent Program,China。
文摘Effects of ultrasonic bonding parameters on atomic diffusion, microstructure at the Al-Au interface, and shear strength of Al-Au ultrasonic bonding were investigated by the combining experiments and finite element (FE) simulation. The quantitative model of atomic diffusion, which is related to the ultrasonic bonding parameters, time and distance, is established to calculate the atomic diffusion of the Al-Au interface. The maximum relative error between the calculated and experimental fraction of Al atom is 7.35%, indicating high prediction accuracy of this model. During the process of ultrasonic bonding, Au8Al3 is the main intermetallic compound (IMC) at the Al-Au interface. With larger bonding forces, higher ultrasonic powers and longer bonding time, it is more difficult to remove the oxide particles from the Al-Au interface, which hinders the atomic diffusion. Therefore, the complicated stress state and the existence of oxide particles both promotes the formation of holes. The shear strength of Al-Au ultrasonic bonding increases with increasing bonding force, ultrasonic power and bonding time. However, combined with the presence of holes at especial parameters, the optimal ultrasonic bonding parameter is confirmed to be a bonding force of 23 gf, ultrasonic power of 75 mW and bonding time of 21 ms.
基金supported by the CAS Project for Young Scientists in Basic Research(YSBR-070)the National Natural Science Foundation of China(21925110,21890750,U2032161,12147105)+8 种基金the USTC Research Funds of the Double First-Class Initiative(YD2060002004)the National Key Research and Development Program of China(2022YFA1203600,2022YFA1203601,2022YFA1203602)the Natural Science Foundation of China-Anhui Joint Fund(U23A20121)the Outstanding Youth Foundation of Anhui Province(2208085J14)the Anhui Provincial Key Research and Development Project(202004a050200760)the Key R&D Program of Shandong Province(2021CXGC010302)the Users with Excellence Project of Hefei Science Center CAS(2021HSC-UE004)the Fellowship of the China Postdoctoral Science Foundation(2022M710141)the open foundation of the Key Laboratory of the Engineering Research Center of Building Energy Efficiency Control and Evaluation,Ministry of Education(AHJZNX-2023-04).
文摘Materials with low thermal conductivity are applied extensively in energy management,and breaking the amorphous limits of thermal conductivity to solids has attracted widespread attention from scientists.Doping is a common strategy for achieving low thermal conductivity that can offer abundant scattering centers in which heavier dopants always result in lower phonon group velocities and lower thermal conductivities.However,the amount of equivalent heavyatom single dopant available is limited.Unfortunately,nonequivalent heavy dopants have finite solubility because of charge imbalance.Here,we propose a charge balance strategy for SnS by substituting Sn2+with Ag^(+)and heavy Bi^(3+),improving the doping limit of Ag from 2%to 3%.Ag and Bi codoping increases the point defect concentration and introduces abundant boundaries simultaneously,scattering the phonons at both the atomic scale and nanoscale.The thermal conductivity of Ag0.03Bi0.03Sn0.94S decreased to 0.535 W·m^(−1)·K^(−1)at room temperature and 0.388 W·m^(−1)·K^(−1)at 275°C,which is below the amorphous limit of 0.450 W·m^(−1)·K^(−1)for SnS.This strategy offers a simple way to enhance the doping limit and achieve ultralow thermal conductivity in solids below the amorphous limit without precise structural modification.
基金supported by the National Natural Science Foundation of China(6193101562071335)+1 种基金the Technological Innovation Project of Hubei Province of China(2019AAA061)the Natural Science F oundation of Hubei Province of China(2021CFA002)。
文摘In this paper,we study the accuracy of delay-Doppler parameter estimation of targets in a passive radar using orthogonal frequency division multiplexing(OFDM)signal.A coarse-fine joint estimation method is proposed to achieve better estimation accuracy of target parameters without excessive computational burden.Firstly,the modulation symbol domain(MSD)method is used to roughly estimate the delay and Doppler of targets.Then,to obtain high-precision Doppler estimation,the atomic norm(AN)based on the multiple measurement vectors(MMV)model(MMV-AN)is used to manifest the signal sparsity in the continuous Doppler domain.At the same time,a reference signal compensation(RSC)method is presented to obtain highprecision delay estimation.Simulation results based on the OFDM signal show that the coarse-fine joint estimation method based on AN-RSC can obtain a more accurate estimation of target parameters compared with other algorithms.In addition,the proposed method also possesses computational advantages compared with the joint parameter estimation.
基金Project(22102218)supported by the National Natural Science Foundation of ChinaProject(2022RC1110)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(2022QNRC001)supported by the Young Elite Scientists Sponsorship Program by CAST,China。
文摘Formic acid oxidation reaction(FAOR),as the anodic reaction in direct formic acid fuel cells,has attracted much attention but increasing the mass activity and stability of catalysts still face a bottleneck to meet the requirements of practical applications.In the past decades,researchers developed many strategies to fix these issues by improving the structure of catalysts and the newly raised single atom catalysts(SACs)show the high mass activity and stability in FAOR.This review first summarized the reaction mechanism involved in FAOR.The mass activity as well as stability of catalysts reported in the past five years have been outlined.Moreover,the synthetic strategies to improve the catalytic performance of catalysts are also reviewed in this work.Finally,we proposed the research directions to guide the rational design of new FAOR catalysts in the future.
文摘new coordination polymer {[Zn(CF3COO)2(C5H5ON)]·H2O}n was synthesized based on the reaction of zinc(Ⅱ) trifluoroacetate and 3-hydroxypyridine(C5H5ON) in methanol medium for the first time. The structure of the coordination polymer was confirmed by IR, 1H NMR, elemental analysis and thermal analysis. The crystal structure of the coordination polymer was also determined by X-ray single crystal diffraction. The crystal belongs to monoclinic system with space group P21/m, and crystallographic data of the coordination polymer are: a= 0.863 1(4) nm, b=0.717 7(3) nm, c=1.116 4(5) nm, α=γ=90°, β=107.542(6)°, V=0.659 4(5) nm3; Dc=2.037 g·cm-3; Z=2; F(000)=400; μ=1.969 mm-1. Zinc(Ⅱ) atom lies at the center of an octahedron formed by the coordination of zinc atom and six O atoms which come from four different trifluoroacetate ions and two different 3-hydroxypyridine molecules where each trifluoroacetate ion and 3-hydroxypyridine are coordinated to two different zinc ions to form coordination polymer. CCDC: 253909.
文摘A new binuclear copper(Ⅱ) complex, [Cu2(phen)2(H2O)2( μ2-C2O4)](NO3)2, has been synthesized and characterized by elemental analysis, IR and UV-Vis spectrum. Its crystal structure was determined by single crystal X-ray diffraction techniques. Crystal data: monoclinic, space group P21/c, a=0.712 21(8) nm, b=1.170 93(14) nm, c=1.783 7(2) nm, β=111.828(2)°, and V=1.380 8(3) nm3, Dc=1.769 Mg·m-3, Z=2, F(000)=744, R1=0.025 4, wR2=0.069 5, Gof=1.077, Δρ=328^-455 e·nm-3. The complex is packed by one centrosymmetry binuclear copper(Ⅱ) unit, oxalate dianion and NO3- anion. In the molecule structure of the title complex, two Cu(Ⅱ) ions are bridged by oxalate dianion and each Cu(Ⅱ) ions coordinates with two nitrogen atoms from 1,10-phenanthroline ligand and one oxygen atom from water to form a five-coordinate distorted square-pyramidal configuration. The hydrogen bonds are observed between coordinated water molecules and NO3- anions. The analysis of the crystal structure indicates that the complex has a two-dimensional stacking network structure, which is formed by intramolecular hydrogen bonds, intermolecular hydrogen bonds and stacking effect of aromatic ring. CCDC: 255345.
文摘The μ-oxygen-bis[tri(p-fluorobenzyl)tin] was synthesized. The structure were characterized by elementary analysis, IR and 1H NMR and the crystal structure were determined by X-ray single crystal diffraction. The crystal of the title compound belongs to rhombohedral with space group R, a=1.346 4(4), b=1.346 4(4), c=1.772 9(7) nm, α=90°, β=90°, γ=120°, Z=3, V=2.783 2(15) nm3, Dc=1.625 g·cm-3, μ(Mo Kα)=1.408 mm-1, S=1.088, F(000)=1 350, R1=0.027 5, wR2=0.065 9. In compound, the tin atom has a distorted tetrahedral coordination configuration. CCDC: 257079.
文摘Diorganotin(Ⅳ) compound [(p-CNC6H4CH2)2Sn(C9H7N3O3)(H2O)]2 was synthesized by the reaction of tri-p-cyanobenzyltin chloride with Schiff base ligand pyruvic acid isonicotinyl hydrazone. The compound was characterized by elemental analysis, IR, 1H NMR. The crystal structure was determined by X-ray single crystal diffraction. The crystal belongs to monoclinic space group C2/c, with a=3.143 1(3) nm, b=0.989 99(10) nm, c=1.785 68(18) nm, β=114.908 0(13)°, V=5.039 6(9) nm3, Z=4, μ=1.054 mm-1, Dc=1.513 Mg·m-3, F(000)=2 304, R=0.042 8, wR=0.090 3, GOF=0.997. In this compound, the Sn atom exists in a distorted octahedral coordination environment in which one water molecule, one tridentate pyruvic acid isonicotinyl hydrazone ligand, and two trans p-cyanobenzyl groups coordinate to each Sn center, the angle of the axial C10-Sn1-C18 is 166.1(2)°. Two molecules form a weak-bridged dimmer with weak interactions of Sn...O bonding and hydrogen bonds. CCDC: 270796.
