WC particles reinforced CoCrFeNiMo high-entropy alloy(HEA)composite coatings were prepared on Cr12MoV steel successfully by laser cladding technology to improve the wear resistance of substrates.Effect of WC content o...WC particles reinforced CoCrFeNiMo high-entropy alloy(HEA)composite coatings were prepared on Cr12MoV steel successfully by laser cladding technology to improve the wear resistance of substrates.Effect of WC content on microstructure and wear property of the composite coatings was studied in detail.Large numbers of carbides with four main types:primary carbide crystals,eutectic structures,massive crystals growing along the periphery of the remaining WC particles and incompletely fused WC particles,were found to exist in the WC/CoCrFeNiMo composite coatings.With increasing WC content,the microhardness of coatings is gradually improved while the average friction coefficients follow the opposite trend due to solid solution strengthening and second phase strengthening effect.The maximum microhardness and minimum friction coefficient are HV_(0.2)689.7 and 0.72,respectively,for the composite coating with 30 wt.%WC,the wear resistance of the substrate is improved significantly,the wear mechanisms are spalling wear and abrasive wear due to their high microhardness.展开更多
Polybrominated biphenyl ethers(PBDEs)and polycyclic aromatic hydrocarbons(PAHs)are commonly detected contaminants at e-waste recycling sites.Against the conventional wisdom that PBDEs and PAHs are highly immobile and ...Polybrominated biphenyl ethers(PBDEs)and polycyclic aromatic hydrocarbons(PAHs)are commonly detected contaminants at e-waste recycling sites.Against the conventional wisdom that PBDEs and PAHs are highly immobile and persist primarily in shallowsurface soils,increasing evidence shows that these compounds can leach into the groundwater.Herein,we compare the leachabilities of PBDEs vs.PAHs from contaminated soils collected at an e-waste recycling site in Tianjin,China.Considerable amounts of BDE-209(0.3–2 ng/L)and phenanthrene(42–106 ng/L),the most abundant PBDE and PAH at the site,are detected in the effluents of columns packed with contaminated soils,with the specific concentrations varying with hydrodynamic and solution chemistry conditions.Interestingly,the leaching potential of BDE-209 appears to be closely related to the release of colloidal mineral particles,whereas the leachability of phenanthrene correlates well with the concentration of dissolved organic carbon in the effluent,but showing essentially no correlation with the concentration of mineral particles.The surprisingly different trends of the leachability observed between BDE-209 and phenanthrene is counterintuitive,as PBDEs and PAHs often co-exist at e-waste recycling sites(particularly at the sites wherein incineration is being practiced)and share many similarities in terms of physicochemical properties.One possible explanation is that due to its extremely low solubility,BDE-209 predominantly exists in free-phase(i.e.,as solid(nano)particles),whereas the more soluble phenanthrene is mainly sorbed to soil organic matter.Findings in this study underscore the need to better understand the mobility of highly hydrophobic organic contaminants at contaminated sites for improved risk management.展开更多
Densely distributed coherent nanoparticles(DCN)in steel matrix can enhance the work-hardening ability and ductility of steel simultaneously.All the routes to this end can be generally classified into the liquid-solid ...Densely distributed coherent nanoparticles(DCN)in steel matrix can enhance the work-hardening ability and ductility of steel simultaneously.All the routes to this end can be generally classified into the liquid-solid route and the solid-solid route.However,the formation of DCN structures in steel requires long processes and complex steps.So far,obtaining steel with coherent particle enhancement in a short time remains a bottleneck,and some necessary steps remain unavoidable.Here,we show a high-efficiency liquid-phase refining process reinforced by a dynamic magnetic field.Ti-Y-Mn-O particles had an average size of around(3.53±1.21)nm and can be obtained in just around 180 s.These small nanoparticles were coherent with the matrix,implying no accumulated dislocations between the particles and the steel matrix.Our findings have a potential application for improving material machining capacity,creep resistance,and radiation resistance.展开更多
Biocompatible amphiphilic nanoparticles(NPs)with tunable particle morphology and surface property are important for their applications as functional materials.However,previously developed methods to prepare amphiphili...Biocompatible amphiphilic nanoparticles(NPs)with tunable particle morphology and surface property are important for their applications as functional materials.However,previously developed methods to prepare amphiphilic NPs generally involve several steps,especially an additional step for surface modification,greatly hindering their largescale production and widespread applications.Here,a versatile one-step strategy is developed to prepare biocompatible amphiphilic dimer NPs with tunable particle morphology and surface property.The amphiphilic dimer NPs,which consist of a hydrophobic shellac bulb and a hydrophilic poly(lactic acid)(PLA)bulb with PLA-poly(ethylene glycol)(PEG)on the bulb surface,are prepared in a single step by controlled co-precipitation and self-assembly.Amphiphilic PLA-PEG/shellac dimer NPs demonstrate excellent tunability in particle morphology,thus showing good performances in controlling the interfacial curvature and emulsion type.In addition,temperatureresponsive PLA-poly(N-isopropyl acrylamide)(PNIPAM)/shellac dimer NPs are prepared following the same method and emulsions stabilized by them show temperature-triggered response.The applications of PLA-PEG-folic acid(FA)/shellac dimer NPs for drug delivery have also been demonstrated,which show a very good performance.The strategy of preparing the dimer NPs is green,scalable,facile and versatile,which provides a good platform for the design of dimer NPs with tunable particle morphology and surface property for diverse applications.展开更多
We review a 3d quantum gravity model, which incorporates massive spinning fields into the Euclidean path integral in a Chern-Simons formulation. Fundamental matter as defined in our previous preon model is recapped. B...We review a 3d quantum gravity model, which incorporates massive spinning fields into the Euclidean path integral in a Chern-Simons formulation. Fundamental matter as defined in our previous preon model is recapped. Both quantum gravity and the particle model are shown to be derivable from the supersymmetric 3d Chern-Simons action. Forces-Matter unification is achieved.展开更多
Studying the contribution of regional transport to ultrafine particles(UFPs)and the deposition effect of nanoscale particles in human respiratory system is conducive to exploring the impact of atmospheric particles on...Studying the contribution of regional transport to ultrafine particles(UFPs)and the deposition effect of nanoscale particles in human respiratory system is conducive to exploring the impact of atmospheric particles on the environment and human health.Based on the data set of number concentration spectrum in the particle size range of 5.6–560 nm in the spring of Hefei,the Yangtze River Delta region obtained by a fast mobility particle sizer,the explosive growth characteristics,potential source identification and deposition flux analysis of UFPs were systematically studied.The results showed that the frequency of new particle formation(NPF)events during spring was 31.5%.SO_(2) and O_(3) contribute to NPF events.Daytime,higher temperature,stronger solar radiation and lower humidity were more conducive to the explosive growth of UFPs.In addition,regional transport of pollutants from the cities around Hefei played an important role in the accumulation mode particles,which were mainly affected by the land-source air mass from northwest Jiangsu(23.64%)and the sea-source air mass from the Yellow Sea(23.99%).It was worth noting that approximately 10,406 ng of UFPs enters the human respiratory system every day.Themain deposition area of 5.6–560 nm nanoscale particles was alveolar,5.6–400 nm is more likely to be deposited on alveolar,while nanoscale particles with particle size between 400 and 560 nm is more likely to be deposited on head airways.This study identified the deposition risk of nanoscale particles in the respiratory system under different particle sizes.展开更多
Aerosol particle pollution has become an increasing serious environmental problem,and urban vegetation plays a long-lasting and positive role in mitigating it.This study compared the particle capture abilities of tree...Aerosol particle pollution has become an increasing serious environmental problem,and urban vegetation plays a long-lasting and positive role in mitigating it.This study compared the particle capture abilities of trees,shrubs,and herbs,and examined the compositions and influence of aerosol particles accumulated on leaf functional traits.Retained particles primarily contained Ca^(2+),K^(+),SO_(4)^(2-),NO_(3)^(-)and NH_(4)^(+),indicating their anthropogenic origins.The leathery-leaved tree Osmanthus fragrans and the papery-leaved herb Alternanthera sessilis demonstrated the higher competence in particle accumulation than other plants,and leaf morphologic structures(e.g.,leaf grooves,trichomes,waxy layers,and stomata characteristics)were closely associated with particle capture by plant species.Particle retention negatively impacted stomata,impeding photosynthesis,and reducing transpiration.In response to particle accumulation,plants tended to decrease specific leaf area and adjust stomatal conductance.Both growth form and leaf texture significantly influenced the particle capture abilities of different plant species.The substantial contribution of plants,particularly herbs in the lower vegetation strata,to particle removal should not be overlooked.Vegetation with a tree-shrub-herb configuration excels at particle capture,offering potential advantages in mitigating particle pollution and enhancing ecological benefits.展开更多
The effect of intermetallic particles on the corrosion of 6061 aluminum alloy and its coating used in semiconductor processing systems was systematically studied via liquid and gas experiments and micromorphology char...The effect of intermetallic particles on the corrosion of 6061 aluminum alloy and its coating used in semiconductor processing systems was systematically studied via liquid and gas experiments and micromorphology characterization.The results revealed that a huge difference of corrosion resistance between imported and domestic 6061 aluminum alloys in HCl solution and gas acid mist experiments mainly was attributed to the different size and amount of Al_(15)(Fe,Mn)_(3)Si_(2).The corrosion resistance of domestic 6061 alloy in dry/wet semiconductor electronic special gas environments was worse than that of imported aluminum alloy,and there are great differences in the corrosion mechanism of 6061 alloy caused by the second phase in the two dry/wet environments.And the corrosion resistance of the hard anodized alumina film was closely related to the microscopic morphology of holes.The vertical and elongatedα-Al_(15)(Mn,Fe)_(3)Si_(2) phase was formed in the rolled aluminum alloy that has been rolled perpendicular to the surface of the substrate.Compared to the horizontal long hole,the longitudinal long holes generated by the verticalα-Al_(15)(Mn,Fe)_(3)Si_(2) phase will enable the corrosive medium to reach the substrate rapidly,which significantly weakens the corrosion resistance of the hard anodized film.展开更多
The Feynman ratchet has the ability to convert random fluctuations into directional particle transport.The transport velocity of particles is highly dependent on their size,leading to directional transport and subsequ...The Feynman ratchet has the ability to convert random fluctuations into directional particle transport.The transport velocity of particles is highly dependent on their size,leading to directional transport and subsequent particle separation under suitable parameter conditions.Here,exploiting the distinct responses of particles with different sizes to the system,the separation of bi-dispersed dust particles is achieved experimentally in air at 35 Pa using a dusty plasma ratchet.To reveal the underlying mechanisms,we construct a plasma model and perform Langevin simulations for the particle separation.Our numerical results reveal that charged dust particles experience an asymmetric ratchet potential,which dictates their directional transport.Crucially,bi-dispersed dust particles are suspended at different heights and are subject to ratchet potentials with opposing asymmetries,resulting in their separation.These findings may offer new perspectives for related fields,including microfluidics,nanotechnology,and micrometer-scale particle manipulation.展开更多
Triboelectric nanogenerators(TENGs)are emerging as new technologies to harvest electrical power from mechanical energy.With the distinctive working mechanism of triboelectric nanogenerators,they attract particular int...Triboelectric nanogenerators(TENGs)are emerging as new technologies to harvest electrical power from mechanical energy.With the distinctive working mechanism of triboelectric nanogenerators,they attract particular interest in healthcare monitoring,wearable electronics,and deformable energy harvesting,which raises the requirement for highly conformable devices with substantial energy outputs.Here,a simple,low-cost strategy for fabricating stretchable triboelectric nanogenerators with ultra-high electrical output is developed.The TENG is prepared using PTFE micron particles(PPTENG),contributing a different electrostatic induction process compared to TENG based on dielectric films,which was associated with the dynamics of particle motions in PP-TENG.The generator achieved an impressive voltage output of 1000 V with a current of 25 lA over a contact area of 40320 mm^(2).Additionally,the TENG exhibits excellent durability with a stretching strain of 500%,and the electrical output performance does not show any significant degradation even after 3000 cycles at a strain of 400%.The unique design of the device provides high conformability and can be used as a self-powered sensor for human motion detection.展开更多
Particle transport is a fundamental aspect of various systems,from artificial to biological.A common assumption is that particle motion follows Markovian(memoryless)processes in the absence of interaction between part...Particle transport is a fundamental aspect of various systems,from artificial to biological.A common assumption is that particle motion follows Markovian(memoryless)processes in the absence of interaction between particles.However,hydrodynamic memory and the interaction between particles are ubiquitous,leaving many fundamental questions unanswered regarding transport of interacting particles involving hydrodynamic drag in corrugated channels,as described by the fractional Langevin equation.This study examines the hydrodynamic transport of interacting non-Brownian particles moving within a corrugated channel.We propose a method that relies on factors such as temperature,the driving force to alternate between no transport and finite net transport.Of importance is to note that the absence of transport results from the clogging,while the transport consists of collective motion and independent motion.The transport systems investigated in this work suggest the potential for sensor functionality within the system.Our findings may prove valuable for exploring the transport with hydrodynamic memory in various fields,including biology,physics,and chemistry.展开更多
This study focused on investigating the effects of various factors on the mechanical properties of superconducting matrix composites reinforced with ferromagnetic particles and interface phases when exposed to externa...This study focused on investigating the effects of various factors on the mechanical properties of superconducting matrix composites reinforced with ferromagnetic particles and interface phases when exposed to external magnetic fields.A micromechanical model was created by simplifying the basic properties and composition of the interface,utilizing principles such as Eshelby’s equivalent inclusion theory and Hooke’s law,as well as applying uniform stress boundary conditions.Through the development of equations,the study predicted changes in effective mechanical properties,highlighting the significant influence of parameters like the interface phase,inclusions,and magnetic field on the effective elastic modulus and magnetostriction of the composite material.By shedding light on these relationships,the research offers valuable insights for the manufacture and application of ferromagnetic particle-reinforced superconducting matrix composites with interface phases,providing a foundation for future research in this area.展开更多
The blocky LPSO particles were modulated by single-directional and multi-directional forging,and the effect of blocky LPSO particles on the anisotropy of mechanical properties of Mg-8.5Gd-2.5Y-1.5Zn-0.5Zr alloy forged...The blocky LPSO particles were modulated by single-directional and multi-directional forging,and the effect of blocky LPSO particles on the anisotropy of mechanical properties of Mg-8.5Gd-2.5Y-1.5Zn-0.5Zr alloy forged parts was investigated.In the present work,3D processing maps are established,and the forming domain that is both stable and power efficient is in the temperature range from 430 to 500℃ and strain rate range from 0.001 to 0.06 s^(-1),which is used to guide the single-directional forging(SDF)and multi-directional forging(MDF)experiments.The tensile mechanical properties reveal that the blocky LPSO particles have an influence on the mechanical anisotropy,especially in terms of the elongation anisotropy.The blocky LPSO particles after the MDF process have a more regular shape and smaller size and are homogeneously distributed,which is responsible for the low anisotropy of the elongation.In addition,the age-hardening capability of the MDF part is higher than that of the SDF part.展开更多
A partly clumped-particles combined with joint planes model was developed to simulate the microstructure of quartz mica schist.It considers grain-scale heterogeneity including microgeometry heterogeneity and grain-sca...A partly clumped-particles combined with joint planes model was developed to simulate the microstructure of quartz mica schist.It considers grain-scale heterogeneity including microgeometry heterogeneity and grain-scale elastic heterogeneity.Clumped-particles with larger volume and larger stiffness were used to represent stiff minerals such as quartz,the rest of unclumped particles with smaller stiffness were used to represent soft minerals such as mica.The joint planes,which have smaller stiffness and strength than mica,were used to describe schist.The extensive sensitivity studies have shown that the clump’s radius,clump’s content and joint plane’s strength affect the microscopic and macroscopic behaviors of sample.For DanBa quartz mica schist,the model calibrated uniaxial tests and well matched with the stress-strain curves,crack initiation stress and crack damage stress of laboratory test.展开更多
Herein,we fabricate an embedding structure at the interface between Pt nanoparticles(NPs)and CeO_(2)-{100}nanocubes with surface defect sites(CeO_(2)-SDS)through quenching and gas bubbling-assisted membrane reduction ...Herein,we fabricate an embedding structure at the interface between Pt nanoparticles(NPs)and CeO_(2)-{100}nanocubes with surface defect sites(CeO_(2)-SDS)through quenching and gas bubbling-assisted membrane reduction methods.The in-situ substitution of Pt NPs for atomic-layer Ce lattice significantly increases the amount of reactive oxygen species from 133.68μmol/g to 199.44μmol/g.As a result,the distinctive geometric structure of Pt/CeO_(2)-SDS catalyst substantially improves the catalytic activity and stability for soot oxidation compared with the catalyst with no quenching process,i.e.,its T_(50)and TOF values are 332°C and 2.915 h^(-1),respectively.Combined with the results of experimental investigations and density functional theory calculations,it is unveiled that the unique embedding structure of Pt/CeO_(2)-SDS catalyst can facilitate significantly electron transfer from Pt to the CeO_(2)-{100}support,and induce the formation of interfacial[Ce-O_(x)-Pt_(2)]bond chains,which plays a crucial role in enhancing the key step of soot oxidation through the dual activation of surface lattice oxygen and molecular O_(2).Such a fundamental revelation of the interfacial electronic transmission and corresponding modification strategy contributes a novel opportunity to develop high-efficient and stable noble metal catalysts at the atomic level.展开更多
The particle size distribution plays a crucial role in the transportation and deposition of eroded sediments.Gaining insights into the related sorting mechanism can significantly enhance our understanding of such proc...The particle size distribution plays a crucial role in the transportation and deposition of eroded sediments.Gaining insights into the related sorting mechanism can significantly enhance our understanding of such processes.In this study,sand-covered slopes were examined.A controlled indoor rainfall simulation was conducted on loess slopes with a 12°incline and a rainfall intensity of 1.5 mm/min.These slopes were then covered with sand layers of varying thicknesses—0.5,1.0,and 1.5 cm—to observe their effects.The findings have revealed that as the thickness of the sand cover increases,the content of sediment particles smaller than 0.054 mm decreases.In contrast,the content of particles larger than 0.054 mm increases after the sixth minute of runoff.The eroded sediment was predominantly composed of silt.During the inter-rill erosion stage,runoff primarily transported particles larger than 0.054 mm.However,in the subsequent rill erosion and combined rill and inter-rill erosion stages,the runoff predominantly carried finer particles,smaller than 0.054 mm.Moreover,the presence of the sand layer significantly influenced the size and form of the eroded sediment particles.Initially,during the first 10 min of runoff,the eroded particles were predominantly larger than 0.054 mm.After this period,however,the particle size shifted,with the majority of particles being smaller than 0.054 mm.This study highlights the intricate relationship between sediment sorting,the thickness of sand covers,and the dynamics of sediment transport under rainfall-induced erosion.展开更多
Nitrogen-containing organic compounds(NOCs)may potentially contribute to aqueous secondary organic aerosols,yet the different formation of NOCs in aerosol particles and cloud droplets remains unclear.With the in-situ ...Nitrogen-containing organic compounds(NOCs)may potentially contribute to aqueous secondary organic aerosols,yet the different formation of NOCs in aerosol particles and cloud droplets remains unclear.With the in-situ measurements performed at a mountain site(1690 m a.s.l.)in southern China,we investigated the formation of NOCs in the cloud droplets and the cloud-free particles,based on their mixing state information of NOCscontaining particles by single particle mass spectrometry.The relative abundance of NOCs in the cloud-free particles was significantly higher than those in cloud residual(cloud RES)particles.NOCs were highly correlated with carbonyl compounds(including glyoxalate and methylglyoxal)in the cloud-free particles,however,limited correlation was observed for cloud RES particles.Analysis of their mixing state and temporal variations highlights that NOCs was mainly formed from the carbonyl compounds and ammonium in the cloud-free particles,rather than in the cloud RES particles.The results support that the formation of NOCs from carbonyl compounds is facilitated in concentrated solutions in wet aerosols,rather than cloud droplets.In addition,we have identified the transport of biomass burning particles that facilitate the formation of NOCs,and that the observed NOCs is most likely contributed to the light absorption.These findings have implications for the evaluation of NOCs formation and their contribution to light absorption.展开更多
In order to avoid poor machinability caused by excessive hardness under high-silicon conditions in the traditional free-cutting graphited steel,it is important to develop a suitable silicon-saving,aluminum-containing ...In order to avoid poor machinability caused by excessive hardness under high-silicon conditions in the traditional free-cutting graphited steel,it is important to develop a suitable silicon-saving,aluminum-containing free-cutting steel.This study investigated the microstructure and graphite precipitation behavior of Fe–0.58C–1.0Al(wt%)steels with varying silicon contents(0.55wt%–2.67wt%)after tempering at different temperatures(680℃,715℃).The tempering structure and the precipitation behavior of graphite and Fe_(3)C in Fe–0.58C–1.0Al steels were systematically studied by optical microscopy(OM),field emission scanning electron microscopy(FESEM),and electron microprobe analyzer(EPMA).The results showed that,at both tempering temperatures,the microstructure of 0.55wt%Si steel is ferrite+granular Fe_(3)C,and the microstructures of 1.38wt%–2.67wt%Si steels are ferrite+petaloid graphite+granular Fe_(3)C.With increasing Si content from 1.38wt%to 2.67wt%at constant tempering temperature,the number density of graphite particles increases,though their average size decreases.Meanwhile,the number density and average size of Fe_(3)C in experimental steels continuously decrease with the increase of Si content.For 0.55wt%Si steel without graphite precipitation,increasing tempering temperature promotes the accumulation and growth of Fe_(3)C.For 1.38wt%–2.67wt%Si steels with graphite precipitation,higher tempering temperature promotes graphite particles growth while accelerating the decomposition and refinement of Fe_(3)C.Furthermore,compared with the experimental steels containing 0.55wt%Si,1.38wt%Si,and 2.67wt%Si,the 1.89wt%Si steel exhibits significantly lower hardness.Especially,when tempered at 715℃,Fe–0.58C–1.0Al steel with 1.89wt%Si exhibits enhanced graphitization behavior and reduced hardness,which is nearly HV 20 lower than previously reported Fe–0.55C–2.33Si steel.展开更多
Gravity-driven membrane filtration(GDM)has increasingly captured researchers'attention due to its low energy consumption and operation&maintenance.However,severe membrane fouling and permeate DOC increase rest...Gravity-driven membrane filtration(GDM)has increasingly captured researchers'attention due to its low energy consumption and operation&maintenance.However,severe membrane fouling and permeate DOC increase restricted GDM's widespread application.This study combined granular active carbon(GAC)and magnetic particles to address this issue and results suggested that GDM3 achieved highly effective pollutant removals(85%COD_(Mn),95% UV_(254),and 65% DOC)and significant flux improvement(96%)than GDM itself.GAC pretreatment before the membrane mainly helped to reduce pollutant load and improve permeated quality while magnetic particles in situ on the membrane surface contributed to engineering more open and connected structures with less extracellular polymeric substance(EPS)and soluble microbial products(SMP)than other GDM groups due to their bioeffect.GDM3 was cost-effective and had the lowest total cost with a decrease of 7.5%and 5.7%to GDM1 and GDM2.The findings provided a deep insight into the combined GAC and magnetic particles in GDM performance improvement and played a fundamental role in developing sustainable and environmentally friendly GDM processes.展开更多
Researching the dispersion as well as the stability of metals on the oxide surfaces is essentially important for understanding the interaction mecha-nisms at the metal/oxide interfaces and thus optimizing the activiti...Researching the dispersion as well as the stability of metals on the oxide surfaces is essentially important for understanding the interaction mecha-nisms at the metal/oxide interfaces and thus optimizing the activities of the heterogeneous catalysts.Here in this work,we have investigated the growth behavior of Pd particles on the polar surfaces of ZnO with scanning tunneling microscopy(STM).By systematically varying the coverages as well as the annealing temperatures,we found that at room temperature Pd tends to form three-dimensional(3D)round particles on the ZnO(000)surface but grow into monolayer two-dimensional(2D)hexagonal islands on the ZnO(0001)surface.During annealing processes,the Pd particles on ZnO(000)aggregate gently while maintaining the 3D morphology in the mild temperature range but then quickly transform in-to tall hexagonal islands at elevated temperatures.In contrast,the segregation of Pd islands on ZnO(0001)occurs gradually along with the temperature rising without changing the 2D morphology.These results directly reflect the different interaction strengths of Pd on the dis-tinct ZnO polar surfaces.They also provide important input for understanding the facet-de-pendent catalytic mechanisms of the Pd/ZnO catalytic systems.展开更多
基金Project(2021YFC2801904)supported by the National Key R&D Program of ChinaProject(KY10100230067)supported by the Basic Product Innovation Research Project,China+3 种基金Projects(52271130,52305344)supported by the National Natural Science Foundation of ChinaProjects(ZR2020ME017,ZR2020QE186)supported by the Natural Science Foundation of Shandong Province,ChinaProjects(AMGM2024F11,AMGM2021F10,AMGM2023F06)supported by the Science Fund of Shandong Laboratory of Advanced Materials and Green Manufacturing at Yantai,ChinaProject(KY90200210015)supported by Leading Scientific Research Project of China National Nuclear Corporation(CNNC),China。
文摘WC particles reinforced CoCrFeNiMo high-entropy alloy(HEA)composite coatings were prepared on Cr12MoV steel successfully by laser cladding technology to improve the wear resistance of substrates.Effect of WC content on microstructure and wear property of the composite coatings was studied in detail.Large numbers of carbides with four main types:primary carbide crystals,eutectic structures,massive crystals growing along the periphery of the remaining WC particles and incompletely fused WC particles,were found to exist in the WC/CoCrFeNiMo composite coatings.With increasing WC content,the microhardness of coatings is gradually improved while the average friction coefficients follow the opposite trend due to solid solution strengthening and second phase strengthening effect.The maximum microhardness and minimum friction coefficient are HV_(0.2)689.7 and 0.72,respectively,for the composite coating with 30 wt.%WC,the wear resistance of the substrate is improved significantly,the wear mechanisms are spalling wear and abrasive wear due to their high microhardness.
基金supported by the National Key Research and Development Program of China(No.2019YFC1804202)the National Natural Science Foundation of China(Nos.22020102004 and 22125603)+1 种基金Tianjin Municipal Science and Technology Bureau(No.21JCZDJC00280)the Fundamental Research Funds for the Central Universities,and the Ministry of Education of China(No.T2017002).
文摘Polybrominated biphenyl ethers(PBDEs)and polycyclic aromatic hydrocarbons(PAHs)are commonly detected contaminants at e-waste recycling sites.Against the conventional wisdom that PBDEs and PAHs are highly immobile and persist primarily in shallowsurface soils,increasing evidence shows that these compounds can leach into the groundwater.Herein,we compare the leachabilities of PBDEs vs.PAHs from contaminated soils collected at an e-waste recycling site in Tianjin,China.Considerable amounts of BDE-209(0.3–2 ng/L)and phenanthrene(42–106 ng/L),the most abundant PBDE and PAH at the site,are detected in the effluents of columns packed with contaminated soils,with the specific concentrations varying with hydrodynamic and solution chemistry conditions.Interestingly,the leaching potential of BDE-209 appears to be closely related to the release of colloidal mineral particles,whereas the leachability of phenanthrene correlates well with the concentration of dissolved organic carbon in the effluent,but showing essentially no correlation with the concentration of mineral particles.The surprisingly different trends of the leachability observed between BDE-209 and phenanthrene is counterintuitive,as PBDEs and PAHs often co-exist at e-waste recycling sites(particularly at the sites wherein incineration is being practiced)and share many similarities in terms of physicochemical properties.One possible explanation is that due to its extremely low solubility,BDE-209 predominantly exists in free-phase(i.e.,as solid(nano)particles),whereas the more soluble phenanthrene is mainly sorbed to soil organic matter.Findings in this study underscore the need to better understand the mobility of highly hydrophobic organic contaminants at contaminated sites for improved risk management.
基金financially supported by the National Natural Science Foundation of China(No.51771125)the Sichuan Province Science and Technology Support Program(No.2020YFG0102)。
文摘Densely distributed coherent nanoparticles(DCN)in steel matrix can enhance the work-hardening ability and ductility of steel simultaneously.All the routes to this end can be generally classified into the liquid-solid route and the solid-solid route.However,the formation of DCN structures in steel requires long processes and complex steps.So far,obtaining steel with coherent particle enhancement in a short time remains a bottleneck,and some necessary steps remain unavoidable.Here,we show a high-efficiency liquid-phase refining process reinforced by a dynamic magnetic field.Ti-Y-Mn-O particles had an average size of around(3.53±1.21)nm and can be obtained in just around 180 s.These small nanoparticles were coherent with the matrix,implying no accumulated dislocations between the particles and the steel matrix.Our findings have a potential application for improving material machining capacity,creep resistance,and radiation resistance.
基金supported by National Natural Science Foundation of China(No.22278352)National Key Research and Development Program of China(No.2021YFC3001100)+3 种基金Longyan City Science and Technology Plan Project(No.2020LYF17043)Longyan City Science and Technology Plan Project(No.2020LYF17042)ARC Discovery Project(No.DP200101238)and NHMRC Investigator Grant(No.APP2008698)supported by the Harvard Materials Research Science and Engineering Center(No.DMR2011754)。
文摘Biocompatible amphiphilic nanoparticles(NPs)with tunable particle morphology and surface property are important for their applications as functional materials.However,previously developed methods to prepare amphiphilic NPs generally involve several steps,especially an additional step for surface modification,greatly hindering their largescale production and widespread applications.Here,a versatile one-step strategy is developed to prepare biocompatible amphiphilic dimer NPs with tunable particle morphology and surface property.The amphiphilic dimer NPs,which consist of a hydrophobic shellac bulb and a hydrophilic poly(lactic acid)(PLA)bulb with PLA-poly(ethylene glycol)(PEG)on the bulb surface,are prepared in a single step by controlled co-precipitation and self-assembly.Amphiphilic PLA-PEG/shellac dimer NPs demonstrate excellent tunability in particle morphology,thus showing good performances in controlling the interfacial curvature and emulsion type.In addition,temperatureresponsive PLA-poly(N-isopropyl acrylamide)(PNIPAM)/shellac dimer NPs are prepared following the same method and emulsions stabilized by them show temperature-triggered response.The applications of PLA-PEG-folic acid(FA)/shellac dimer NPs for drug delivery have also been demonstrated,which show a very good performance.The strategy of preparing the dimer NPs is green,scalable,facile and versatile,which provides a good platform for the design of dimer NPs with tunable particle morphology and surface property for diverse applications.
文摘We review a 3d quantum gravity model, which incorporates massive spinning fields into the Euclidean path integral in a Chern-Simons formulation. Fundamental matter as defined in our previous preon model is recapped. Both quantum gravity and the particle model are shown to be derivable from the supersymmetric 3d Chern-Simons action. Forces-Matter unification is achieved.
基金supported by the National Natural Science Foundation of China(Nos.U21A2027,42207113,and 42407141)。
文摘Studying the contribution of regional transport to ultrafine particles(UFPs)and the deposition effect of nanoscale particles in human respiratory system is conducive to exploring the impact of atmospheric particles on the environment and human health.Based on the data set of number concentration spectrum in the particle size range of 5.6–560 nm in the spring of Hefei,the Yangtze River Delta region obtained by a fast mobility particle sizer,the explosive growth characteristics,potential source identification and deposition flux analysis of UFPs were systematically studied.The results showed that the frequency of new particle formation(NPF)events during spring was 31.5%.SO_(2) and O_(3) contribute to NPF events.Daytime,higher temperature,stronger solar radiation and lower humidity were more conducive to the explosive growth of UFPs.In addition,regional transport of pollutants from the cities around Hefei played an important role in the accumulation mode particles,which were mainly affected by the land-source air mass from northwest Jiangsu(23.64%)and the sea-source air mass from the Yellow Sea(23.99%).It was worth noting that approximately 10,406 ng of UFPs enters the human respiratory system every day.Themain deposition area of 5.6–560 nm nanoscale particles was alveolar,5.6–400 nm is more likely to be deposited on alveolar,while nanoscale particles with particle size between 400 and 560 nm is more likely to be deposited on head airways.This study identified the deposition risk of nanoscale particles in the respiratory system under different particle sizes.
基金supported by the National Natural Science Foundation of China(No.31700475).
文摘Aerosol particle pollution has become an increasing serious environmental problem,and urban vegetation plays a long-lasting and positive role in mitigating it.This study compared the particle capture abilities of trees,shrubs,and herbs,and examined the compositions and influence of aerosol particles accumulated on leaf functional traits.Retained particles primarily contained Ca^(2+),K^(+),SO_(4)^(2-),NO_(3)^(-)and NH_(4)^(+),indicating their anthropogenic origins.The leathery-leaved tree Osmanthus fragrans and the papery-leaved herb Alternanthera sessilis demonstrated the higher competence in particle accumulation than other plants,and leaf morphologic structures(e.g.,leaf grooves,trichomes,waxy layers,and stomata characteristics)were closely associated with particle capture by plant species.Particle retention negatively impacted stomata,impeding photosynthesis,and reducing transpiration.In response to particle accumulation,plants tended to decrease specific leaf area and adjust stomatal conductance.Both growth form and leaf texture significantly influenced the particle capture abilities of different plant species.The substantial contribution of plants,particularly herbs in the lower vegetation strata,to particle removal should not be overlooked.Vegetation with a tree-shrub-herb configuration excels at particle capture,offering potential advantages in mitigating particle pollution and enhancing ecological benefits.
基金financially supported by the Program of the National Natural Science Foundation of China(Grant No.52371055)the Young Elite Scientist Sponsorship Program Cast(Grant No.YESS20200139)the Basic Scientific Research Project of Liaoning Provincial Department of Education(Grant No.JYTMS20230618)。
文摘The effect of intermetallic particles on the corrosion of 6061 aluminum alloy and its coating used in semiconductor processing systems was systematically studied via liquid and gas experiments and micromorphology characterization.The results revealed that a huge difference of corrosion resistance between imported and domestic 6061 aluminum alloys in HCl solution and gas acid mist experiments mainly was attributed to the different size and amount of Al_(15)(Fe,Mn)_(3)Si_(2).The corrosion resistance of domestic 6061 alloy in dry/wet semiconductor electronic special gas environments was worse than that of imported aluminum alloy,and there are great differences in the corrosion mechanism of 6061 alloy caused by the second phase in the two dry/wet environments.And the corrosion resistance of the hard anodized alumina film was closely related to the microscopic morphology of holes.The vertical and elongatedα-Al_(15)(Mn,Fe)_(3)Si_(2) phase was formed in the rolled aluminum alloy that has been rolled perpendicular to the surface of the substrate.Compared to the horizontal long hole,the longitudinal long holes generated by the verticalα-Al_(15)(Mn,Fe)_(3)Si_(2) phase will enable the corrosive medium to reach the substrate rapidly,which significantly weakens the corrosion resistance of the hard anodized film.
基金supported by National Natural Science Foundation of China(Nos.12275064 and 12475203)the Hebei Natural Science Fund(No.A2024201020)+1 种基金Hebei University Natural Science Research Innovation Team Project(No.IT2023B03)the Post-graduate’s Innovation Fund Project of Hebei University(No.HBU2024BS007)。
文摘The Feynman ratchet has the ability to convert random fluctuations into directional particle transport.The transport velocity of particles is highly dependent on their size,leading to directional transport and subsequent particle separation under suitable parameter conditions.Here,exploiting the distinct responses of particles with different sizes to the system,the separation of bi-dispersed dust particles is achieved experimentally in air at 35 Pa using a dusty plasma ratchet.To reveal the underlying mechanisms,we construct a plasma model and perform Langevin simulations for the particle separation.Our numerical results reveal that charged dust particles experience an asymmetric ratchet potential,which dictates their directional transport.Crucially,bi-dispersed dust particles are suspended at different heights and are subject to ratchet potentials with opposing asymmetries,resulting in their separation.These findings may offer new perspectives for related fields,including microfluidics,nanotechnology,and micrometer-scale particle manipulation.
基金financially supported by the Sichuan Provincial Science and Technology Fund for Distinguished Young Scholars,China(Grant No.2022JDJQ0028)Research Startup Fund by Sichuan University,China(Grant No.YJ202218).
文摘Triboelectric nanogenerators(TENGs)are emerging as new technologies to harvest electrical power from mechanical energy.With the distinctive working mechanism of triboelectric nanogenerators,they attract particular interest in healthcare monitoring,wearable electronics,and deformable energy harvesting,which raises the requirement for highly conformable devices with substantial energy outputs.Here,a simple,low-cost strategy for fabricating stretchable triboelectric nanogenerators with ultra-high electrical output is developed.The TENG is prepared using PTFE micron particles(PPTENG),contributing a different electrostatic induction process compared to TENG based on dielectric films,which was associated with the dynamics of particle motions in PP-TENG.The generator achieved an impressive voltage output of 1000 V with a current of 25 lA over a contact area of 40320 mm^(2).Additionally,the TENG exhibits excellent durability with a stretching strain of 500%,and the electrical output performance does not show any significant degradation even after 3000 cycles at a strain of 400%.The unique design of the device provides high conformability and can be used as a self-powered sensor for human motion detection.
基金supported by the National Natural Science Foundation of China(Grant Nos.12365007 and 12265017)Yunnan Fundamental Research Projects(Grant Nos.202101AS070018 and 202101AV070015)+1 种基金the Scientific Research Foundation of the Yunnan Provincial Department of Education(Grant No.2023J1208)Xingdian Talents Support Program,and Yunnan Province Ten Thousand Talents Plan Young&Elite Talents Project,and Yunnan Province Computational Physics and Applied Science and Technology Innovation Team.The numerical simulation and significance estimation were performed on the Key Laboratory of High-Density Computing,Zhaotong University。
文摘Particle transport is a fundamental aspect of various systems,from artificial to biological.A common assumption is that particle motion follows Markovian(memoryless)processes in the absence of interaction between particles.However,hydrodynamic memory and the interaction between particles are ubiquitous,leaving many fundamental questions unanswered regarding transport of interacting particles involving hydrodynamic drag in corrugated channels,as described by the fractional Langevin equation.This study examines the hydrodynamic transport of interacting non-Brownian particles moving within a corrugated channel.We propose a method that relies on factors such as temperature,the driving force to alternate between no transport and finite net transport.Of importance is to note that the absence of transport results from the clogging,while the transport consists of collective motion and independent motion.The transport systems investigated in this work suggest the potential for sensor functionality within the system.Our findings may prove valuable for exploring the transport with hydrodynamic memory in various fields,including biology,physics,and chemistry.
基金supported by the National Natural Science Foundation of China(No.12262020).
文摘This study focused on investigating the effects of various factors on the mechanical properties of superconducting matrix composites reinforced with ferromagnetic particles and interface phases when exposed to external magnetic fields.A micromechanical model was created by simplifying the basic properties and composition of the interface,utilizing principles such as Eshelby’s equivalent inclusion theory and Hooke’s law,as well as applying uniform stress boundary conditions.Through the development of equations,the study predicted changes in effective mechanical properties,highlighting the significant influence of parameters like the interface phase,inclusions,and magnetic field on the effective elastic modulus and magnetostriction of the composite material.By shedding light on these relationships,the research offers valuable insights for the manufacture and application of ferromagnetic particle-reinforced superconducting matrix composites with interface phases,providing a foundation for future research in this area.
基金supports of the National Key Research and Development Program of China(Grant No.2021YFB3501005)the National Natural Science Foundation of China(Grant No.52071208)the Key R&D program of Shanxi Province(International Cooperation)(Grant No.201903D421036).
文摘The blocky LPSO particles were modulated by single-directional and multi-directional forging,and the effect of blocky LPSO particles on the anisotropy of mechanical properties of Mg-8.5Gd-2.5Y-1.5Zn-0.5Zr alloy forged parts was investigated.In the present work,3D processing maps are established,and the forming domain that is both stable and power efficient is in the temperature range from 430 to 500℃ and strain rate range from 0.001 to 0.06 s^(-1),which is used to guide the single-directional forging(SDF)and multi-directional forging(MDF)experiments.The tensile mechanical properties reveal that the blocky LPSO particles have an influence on the mechanical anisotropy,especially in terms of the elongation anisotropy.The blocky LPSO particles after the MDF process have a more regular shape and smaller size and are homogeneously distributed,which is responsible for the low anisotropy of the elongation.In addition,the age-hardening capability of the MDF part is higher than that of the SDF part.
基金supported by the Natural Science Foundation of Hubei Province(2021CFA081)the Fundamental Research Funds for the Central Universities(2042023kf0210)the National Natural Science Foundation of China(42277160).
文摘A partly clumped-particles combined with joint planes model was developed to simulate the microstructure of quartz mica schist.It considers grain-scale heterogeneity including microgeometry heterogeneity and grain-scale elastic heterogeneity.Clumped-particles with larger volume and larger stiffness were used to represent stiff minerals such as quartz,the rest of unclumped particles with smaller stiffness were used to represent soft minerals such as mica.The joint planes,which have smaller stiffness and strength than mica,were used to describe schist.The extensive sensitivity studies have shown that the clump’s radius,clump’s content and joint plane’s strength affect the microscopic and macroscopic behaviors of sample.For DanBa quartz mica schist,the model calibrated uniaxial tests and well matched with the stress-strain curves,crack initiation stress and crack damage stress of laboratory test.
基金supported by the Beijing Nova Program(No.20220484215)National Key Research and Development Program of China(Nos.2022YFB3504100,2022YFB3506200,2021YFA1500300 and 2022YFA1500146)National Natural Science Foundation of China(Nos.22376217,22208373,22272090 and 22272106)。
文摘Herein,we fabricate an embedding structure at the interface between Pt nanoparticles(NPs)and CeO_(2)-{100}nanocubes with surface defect sites(CeO_(2)-SDS)through quenching and gas bubbling-assisted membrane reduction methods.The in-situ substitution of Pt NPs for atomic-layer Ce lattice significantly increases the amount of reactive oxygen species from 133.68μmol/g to 199.44μmol/g.As a result,the distinctive geometric structure of Pt/CeO_(2)-SDS catalyst substantially improves the catalytic activity and stability for soot oxidation compared with the catalyst with no quenching process,i.e.,its T_(50)and TOF values are 332°C and 2.915 h^(-1),respectively.Combined with the results of experimental investigations and density functional theory calculations,it is unveiled that the unique embedding structure of Pt/CeO_(2)-SDS catalyst can facilitate significantly electron transfer from Pt to the CeO_(2)-{100}support,and induce the formation of interfacial[Ce-O_(x)-Pt_(2)]bond chains,which plays a crucial role in enhancing the key step of soot oxidation through the dual activation of surface lattice oxygen and molecular O_(2).Such a fundamental revelation of the interfacial electronic transmission and corresponding modification strategy contributes a novel opportunity to develop high-efficient and stable noble metal catalysts at the atomic level.
基金research was funded bymultiple sources,including the Guangxi Natural Science Foundation of Youth Fund(2020GXNSFBA159004)the National Natural Science Foundation Project of China(51779204)the Guilin University of Technology High-Level Talent Research Startup Project(GUTQDJJ2018069).
文摘The particle size distribution plays a crucial role in the transportation and deposition of eroded sediments.Gaining insights into the related sorting mechanism can significantly enhance our understanding of such processes.In this study,sand-covered slopes were examined.A controlled indoor rainfall simulation was conducted on loess slopes with a 12°incline and a rainfall intensity of 1.5 mm/min.These slopes were then covered with sand layers of varying thicknesses—0.5,1.0,and 1.5 cm—to observe their effects.The findings have revealed that as the thickness of the sand cover increases,the content of sediment particles smaller than 0.054 mm decreases.In contrast,the content of particles larger than 0.054 mm increases after the sixth minute of runoff.The eroded sediment was predominantly composed of silt.During the inter-rill erosion stage,runoff primarily transported particles larger than 0.054 mm.However,in the subsequent rill erosion and combined rill and inter-rill erosion stages,the runoff predominantly carried finer particles,smaller than 0.054 mm.Moreover,the presence of the sand layer significantly influenced the size and form of the eroded sediment particles.Initially,during the first 10 min of runoff,the eroded particles were predominantly larger than 0.054 mm.After this period,however,the particle size shifted,with the majority of particles being smaller than 0.054 mm.This study highlights the intricate relationship between sediment sorting,the thickness of sand covers,and the dynamics of sediment transport under rainfall-induced erosion.
基金supported by the National Key Research and Development Program of China(No.2022YFC3701103)the National Natural Science Foundation of China(No.42222705)+1 种基金the Youth Innovation Promotion Association CAS(No.2021354)Guangdong Foundation for Program of Science and Technology Research(No.2023B1212060049).
文摘Nitrogen-containing organic compounds(NOCs)may potentially contribute to aqueous secondary organic aerosols,yet the different formation of NOCs in aerosol particles and cloud droplets remains unclear.With the in-situ measurements performed at a mountain site(1690 m a.s.l.)in southern China,we investigated the formation of NOCs in the cloud droplets and the cloud-free particles,based on their mixing state information of NOCscontaining particles by single particle mass spectrometry.The relative abundance of NOCs in the cloud-free particles was significantly higher than those in cloud residual(cloud RES)particles.NOCs were highly correlated with carbonyl compounds(including glyoxalate and methylglyoxal)in the cloud-free particles,however,limited correlation was observed for cloud RES particles.Analysis of their mixing state and temporal variations highlights that NOCs was mainly formed from the carbonyl compounds and ammonium in the cloud-free particles,rather than in the cloud RES particles.The results support that the formation of NOCs from carbonyl compounds is facilitated in concentrated solutions in wet aerosols,rather than cloud droplets.In addition,we have identified the transport of biomass burning particles that facilitate the formation of NOCs,and that the observed NOCs is most likely contributed to the light absorption.These findings have implications for the evaluation of NOCs formation and their contribution to light absorption.
基金supports by the National Natural Science Foundation of China(No.52274311)the Natural Science Research Project of Anhui Educational Committee,China(No.2023AH051081).
文摘In order to avoid poor machinability caused by excessive hardness under high-silicon conditions in the traditional free-cutting graphited steel,it is important to develop a suitable silicon-saving,aluminum-containing free-cutting steel.This study investigated the microstructure and graphite precipitation behavior of Fe–0.58C–1.0Al(wt%)steels with varying silicon contents(0.55wt%–2.67wt%)after tempering at different temperatures(680℃,715℃).The tempering structure and the precipitation behavior of graphite and Fe_(3)C in Fe–0.58C–1.0Al steels were systematically studied by optical microscopy(OM),field emission scanning electron microscopy(FESEM),and electron microprobe analyzer(EPMA).The results showed that,at both tempering temperatures,the microstructure of 0.55wt%Si steel is ferrite+granular Fe_(3)C,and the microstructures of 1.38wt%–2.67wt%Si steels are ferrite+petaloid graphite+granular Fe_(3)C.With increasing Si content from 1.38wt%to 2.67wt%at constant tempering temperature,the number density of graphite particles increases,though their average size decreases.Meanwhile,the number density and average size of Fe_(3)C in experimental steels continuously decrease with the increase of Si content.For 0.55wt%Si steel without graphite precipitation,increasing tempering temperature promotes the accumulation and growth of Fe_(3)C.For 1.38wt%–2.67wt%Si steels with graphite precipitation,higher tempering temperature promotes graphite particles growth while accelerating the decomposition and refinement of Fe_(3)C.Furthermore,compared with the experimental steels containing 0.55wt%Si,1.38wt%Si,and 2.67wt%Si,the 1.89wt%Si steel exhibits significantly lower hardness.Especially,when tempered at 715℃,Fe–0.58C–1.0Al steel with 1.89wt%Si exhibits enhanced graphitization behavior and reduced hardness,which is nearly HV 20 lower than previously reported Fe–0.55C–2.33Si steel.
基金supported by the National Key Research and Development Program of China(No.2023YFC3208002)National Natural Science Foundation of China(No.52370007)+1 种基金Excellent Youth Foundation of Hei Long Jiang Province of China(No.YQ2022E034)Anhui Provincial Key Laboratory of Environmental Pollution Control and Resource Reuse(No.2021EPC02)。
文摘Gravity-driven membrane filtration(GDM)has increasingly captured researchers'attention due to its low energy consumption and operation&maintenance.However,severe membrane fouling and permeate DOC increase restricted GDM's widespread application.This study combined granular active carbon(GAC)and magnetic particles to address this issue and results suggested that GDM3 achieved highly effective pollutant removals(85%COD_(Mn),95% UV_(254),and 65% DOC)and significant flux improvement(96%)than GDM itself.GAC pretreatment before the membrane mainly helped to reduce pollutant load and improve permeated quality while magnetic particles in situ on the membrane surface contributed to engineering more open and connected structures with less extracellular polymeric substance(EPS)and soluble microbial products(SMP)than other GDM groups due to their bioeffect.GDM3 was cost-effective and had the lowest total cost with a decrease of 7.5%and 5.7%to GDM1 and GDM2.The findings provided a deep insight into the combined GAC and magnetic particles in GDM performance improvement and played a fundamental role in developing sustainable and environmentally friendly GDM processes.
基金supported by the National Natural Science Foundation of China(No.22172152,No.21872130)the National Key R&D Program of China(No.2021YFA1502801).
文摘Researching the dispersion as well as the stability of metals on the oxide surfaces is essentially important for understanding the interaction mecha-nisms at the metal/oxide interfaces and thus optimizing the activities of the heterogeneous catalysts.Here in this work,we have investigated the growth behavior of Pd particles on the polar surfaces of ZnO with scanning tunneling microscopy(STM).By systematically varying the coverages as well as the annealing temperatures,we found that at room temperature Pd tends to form three-dimensional(3D)round particles on the ZnO(000)surface but grow into monolayer two-dimensional(2D)hexagonal islands on the ZnO(0001)surface.During annealing processes,the Pd particles on ZnO(000)aggregate gently while maintaining the 3D morphology in the mild temperature range but then quickly transform in-to tall hexagonal islands at elevated temperatures.In contrast,the segregation of Pd islands on ZnO(0001)occurs gradually along with the temperature rising without changing the 2D morphology.These results directly reflect the different interaction strengths of Pd on the dis-tinct ZnO polar surfaces.They also provide important input for understanding the facet-de-pendent catalytic mechanisms of the Pd/ZnO catalytic systems.
