Metal-organic frameworks(MOFs),which are self-assembled porous coordination materials,have garnered considerable attention in the fields of optoelectronics,photovoltaic,photochemistry,and photocatalysis due to their d...Metal-organic frameworks(MOFs),which are self-assembled porous coordination materials,have garnered considerable attention in the fields of optoelectronics,photovoltaic,photochemistry,and photocatalysis due to their diverse structures and excellent tunability.However,the performance of MOF-based optoelectronic applications currently falls short of the industry benchmark.To enhance the performance of MOF materials,it is imperative to undertake comprehensive investigations aimed at gaining a deeper understanding of photophysics and sequentially optimizing properties related to photocarrier transport,recombination,interaction,and transfer.By utilizing femtosecond laser pulses to excite MOFs,time-resolved optical spectroscopy offers a means to observe and characterize these ultrafast microscopic processes.This approach adds the time coordinate as a novel dimension for comprehending the interaction between light and MOFs.Accordingly,this review provides a comprehensive overview of the recent advancements in the photophysics of MOFs and additionally outlines potential avenues for exploring the time domain in the investigation of MOFs.展开更多
A time-resolved x-ray diffraction technique is employed to monitor the structural transformation of laser-shocked bismuth.Results reveal a retarded transformation from the shock-induced Bi-Ⅴphase to a metastable Bi-...A time-resolved x-ray diffraction technique is employed to monitor the structural transformation of laser-shocked bismuth.Results reveal a retarded transformation from the shock-induced Bi-Ⅴphase to a metastable Bi-Ⅳphase during the shock release,instead of the thermodynamically stable Bi-Ⅲphase.The emergence of the metastable Bi-Ⅳphase is understood by the competitive interplay between two transformation pathways towards the Bi-Ⅳand Bi-Ⅲ,respectively.The former is more rapid than the latter because the Bi-Ⅴto B-Ⅳtransformation is driven by interaction between the closest atoms while the Bi-Ⅴto B-Ⅲtransformation requires interaction between the second-closest atoms.The nucleation time for the Bi-Ⅴto Bi-Ⅳtransformation is determined to be 5.1±0.9 ns according to a classical nucleation model.This observation demonstrates the importance of the formation of the transient metastable phases,which can change the phase transformation pathway in a dynamic process.展开更多
Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2)C-M_(t)C composite ceramic was prepared by hot press sintering,with the Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2)C high-entropy carbide as the main phase.Secondary phase M_(x)C(M...Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2)C-M_(t)C composite ceramic was prepared by hot press sintering,with the Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2)C high-entropy carbide as the main phase.Secondary phase M_(x)C(M=Ti,Zr,Hf,Nb,Ta) was found to be distributed relatively uniform in the composite ceramic.The oxidation behavior of the ceramic was examined after exposure to 923 K and 1173 K.Morphology of the surface and cross sections of all oxidation samples were observed.The characteristics of the oxidation behavior of the high-entropy carbide and the secondary phase M_(x)C were compared and analyzed.The secondary phases(such as Ti-rich carbide or Hf-rich carbide) in the material were seriously oxidized at 923 K and 1173 K,which reflects the superior oxidation performance of the high-entropy carbide.The nano high-entropy oxides with Ti,Zr,Hf,Nb,Ta,and O elements were discovered by oxidation of the composite ceramic.This research will help deepen the understanding of the oxidation mechanism of high-entropy carbide and composite ceramic.展开更多
Here,the influence of grinding media with different shapes on the flotation performance of spodumene and its potential mechanism from microscale insights was investigated using a single mineral flotation experiment,X-...Here,the influence of grinding media with different shapes on the flotation performance of spodumene and its potential mechanism from microscale insights was investigated using a single mineral flotation experiment,X-ray diffraction(XRD)test,scanning electron microscopy combined with energy dispersive spectrometry(SEM-EDS),atomic force microscope(AFM)and X-ray photoelectron spectroscopy(XPS).The flotation data indicated that under anionic/cationic(sodium oleate(NaOL)/DDA)collectors system,the rod milled spodumene has a higher floatability than ball milled ones.XRD results confirmed that rod medium makes spodumene exposed more{110}and{100}planes,while ball medium makes spodumene exposed more{010}planes.The typical anisotropic surface of spodumene makes the surface of rod milled spodumene possess more Al sites,further confirmed by SEM-EDS and XPS results.Additionally,it was found that the rod milled spodumene presents a larger value of elongation and flatness,which are parameters closely related to bubble adhesion.AFM analysis indicated that rod milled products have a rougher surface,while ball milled products have a smoother surface.Consequently,the rod medium enhanced the adsorption of NaOL/DDA on the spodumene surfaces.This work provides theoretical guidance for optimizing the separation of spodumene from the perspective of grinding.展开更多
This paper researched the enhanced flotation separation performance of ilmenite and titanaugite using the mixed collector benzhydroxamic acid/dodecylamine(BHA/DDA).The interface assembly mechanism was mainly investiga...This paper researched the enhanced flotation separation performance of ilmenite and titanaugite using the mixed collector benzhydroxamic acid/dodecylamine(BHA/DDA).The interface assembly mechanism was mainly investigated through in situ attenuated total reflectance Fourier transform infrared(ATRFTIR)spectroscopy combined with the two-dimensional correlation spectroscopy(2D-COS)and X-ray photoelectron spectroscopy(XPS).It has been found that BHA/DDA mixed collectors successfully separate ilmenite from titanaugite at a molar ratio of 8:1.Zeta potential experiments suggested that,in the presence of mixed collector system,the BHA-DDA complex adsorbed on the ilmenite surface via the chemically adsorbed BHA and the electrostatically adsorbed DDA,however,the complex adsorbed on the surface of titanaugite unstably.According to in situ ATR-FTIR combined with 2D-COS and XPS results,the interface assembly mechanism of BHA/DDA is summarized as:the function group of BHA molecules first binds to the metal sites on minerals to form bidentate ligand,then DDA co-adsorbed with BHA on the surface of minerals through hydrogen bonding.DDA may change the adsorption modes of some BHA on the ilmenite surface from four-membered ring to five-membered ring,while the modes on the titanaugite surface is true opposite.Finally,recommended adsorption configurations of the BHA/DDA complex on the two mineral surfaces are proposed.展开更多
A nano-twinned microstructure was found in amorphous SiC after high-temperature annealing.Grazing incidence x-ray diffraction,high-resolution transmission electron microscopy,and electron diffraction were performed to...A nano-twinned microstructure was found in amorphous SiC after high-temperature annealing.Grazing incidence x-ray diffraction,high-resolution transmission electron microscopy,and electron diffraction were performed to characterize the microstructure and phase transition in the recrystallization layer.After 1500℃or 2-h annealing,3C-SiC grains and numerous stacking faults on the{111}planes were visible.Some 3C-SiC grains have nano-twinned structure with{011}planes.Between the nano-twinned 3C-SiC grains,there is a stacking fault,indicating that the formation mechanisms of the nano-twinned structure are related to the disorder of Si atoms.The increase in the twin thickness with increasing annealing temperature demonstrates that the nano-twinned structure can sink for lattice defects,in order to improve the radiation tolerance of SiC.展开更多
The CaCu3Ti4O12(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and ...The CaCu3Ti4O12(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and electrical properties were investigated. The phase composition was determined by X-ray diffraction and the microstructure was examined by SEM. The dielectric constant, dielectric loss, and resistance of the ceramic were also determined by a precision impedance tester. The results show that, as the synthesis temperature increases, the CCTO ceramic grain size decreases and the stoichiometric ratio of Cu/Ca at the grain boundary increases, the dielectric constant increases and the dielectric loss decreases(40 < f < 10 kHz). In addition, when the synthesis time is shorter than 12 h, the Cu/Ca ratio of CCTO decreases and the dielectric constant increases with time increase. However, when the synthesis time exceeds 12 h, this trend is just the opposite. It is further proved that Cu at the grain boundary is not conducive to the dielectric constant of CCTO.展开更多
Chemical disorder on the surface and lattice strain in GaN implanted by Fe^(10+)ions are investigated.In this study,3-MeV Fe^(10+)ions fluence ranges from 1×10^(13)ions/cm^(2)to 5×10^(15)ions/cm^(2)at room t...Chemical disorder on the surface and lattice strain in GaN implanted by Fe^(10+)ions are investigated.In this study,3-MeV Fe^(10+)ions fluence ranges from 1×10^(13)ions/cm^(2)to 5×10^(15)ions/cm^(2)at room temperature.X-ray photoelectron spectroscopy,high-resolution x-ray diffraction,and high-resolution transmission electron microscopy were used to characterize lattice disorder.The transition of Ga-N bonds to oxynitride bonding is caused by ion sputtering.The change of tensile strain out-of-plane with fluence was measured.Lattice disorder due to the formation of stacking faults prefers to occur on the basal plane.展开更多
The formation of cavities in silicon carbide is vitally useful to“smart-cut”and metal gettering in semiconductor industry.In this study,cavities and extended defects formed in helium(He)ions implanted 6H-SiC at room...The formation of cavities in silicon carbide is vitally useful to“smart-cut”and metal gettering in semiconductor industry.In this study,cavities and extended defects formed in helium(He)ions implanted 6H-SiC at room temperature(RT)and 750℃ followed by annealing at 1500℃are investigated by a combination of transmission electron microscopy and high-resolution electron microscopy.The observed cavities and extended defects are related to the implantation temperature.Heterogeneously distributed cavities and extended defects are observed in the helium-implanted 6H-SiC at RT,while homogeneously distributed cavities and extended defects are formed after He-implanted 6H-SiC at 750℃.The possible reasons are discussed.展开更多
SIMP steel is newly developed fully martensitic steel for lead-cooled fast reactors and accelerator-driven systems.It is important to evaluate its radiation resistance via high flux neutron irradiation,where dense He ...SIMP steel is newly developed fully martensitic steel for lead-cooled fast reactors and accelerator-driven systems.It is important to evaluate its radiation resistance via high flux neutron irradiation,where dense He atoms can be formed via(n,α)transmutation reaction.Co-irradiation with Fe and He ions,instead of neutron,was performed.Specimens were irradiated with 6.4-MeV Fe ions to the damage dose of 5 dpa at a depth of 600 nm.Three different helium injection ratios of 60-appm He/dpa(dpa:displacements per atom),200-appm He/dpa and 600-appm He/dpa at a depth of 600 nm,were performed.Two different irradiation temperatures of 300℃and 450℃were carried out.The effect of helium concentration on the microstructure of Fe-irradiated SIMP steel was investigated.Microstructural damage was observed using transmission electron microscopy.The formed dislocation loops and bubbles depended on the helium injection ratio and irradiation temperature.Lots of dislocation loops and helium bubbles were homogeneously distributed at 300℃,but not at 450℃.The causes of observed effects are discussed.展开更多
Ferritic-martensitic steels and ODS steels are attractive candidates for structural materials in advanced nuclear-power systems due to their good swelling resistance. Four kinds of steels, F82 H, 15 Cr-ODS, SIMP and T...Ferritic-martensitic steels and ODS steels are attractive candidates for structural materials in advanced nuclear-power systems due to their good swelling resistance. Four kinds of steels, F82 H, 15 Cr-ODS, SIMP and T91, are investigated in this study. We take 6.4 Me V Fe3+ ions and energy-degraded 1.0 Me V He+ ions in the irradiation of these materials to 5 dpa and 60 appm He/dpa, 200 appm He/dpa and 600 appm He/dpa at 300℃ and 450℃, respectively. The bubble formation and distribution are investigated by transmission electron microscopy(TEM). Formation and distribution of the bubbles in the four investigated steels are compared. The influence of irradiation temperature and helium injection ratio on bubble formation is discussed. It is found that there appears to be homogenously distributed bubbles at 300℃ irradiation while heterogeneously distributed bubbles at 450℃ irradiation.展开更多
Lattice defects induced by ion implantation into SiC have been widely investigated in the decades by various techniques.One of the non-destructive techniques suitable to study the lattice defects in SiC is the optical...Lattice defects induced by ion implantation into SiC have been widely investigated in the decades by various techniques.One of the non-destructive techniques suitable to study the lattice defects in SiC is the optical characterization.In this work,confocal Raman scattering spectroscopy and photoluminescence spectrum have been used to study the effects of 134-keV H_(2)^(+)implantation and thermal treatment in the microstructure of 6H-SiC single crystal.The radiation-induced changes in the microstructure were assessed by integrating Raman-scattering peaks intensity and considering the asymmetry of Raman-scattering peaks.The integrated intensities of Raman scattering spectroscopy and photoluminescence spectrum decrease with increasing the fluence.The recovery of the optical intensities depends on the combination of the implantation temperature and the annealing temperature with the thermal treatment from 700℃to 1100℃.The different characterizations of Raman scattering spectroscopy and photoluminescence spectrum are compared and discussed in this study.展开更多
Helium effects on dislocation and cavity formation of Fe-11 wt.% Cr model alloy are investigated. Single-beam(electron) and dual-beam(He^+/e^-) irradiations are performed at 350℃ and 400℃ using an ultra-high voltage...Helium effects on dislocation and cavity formation of Fe-11 wt.% Cr model alloy are investigated. Single-beam(electron) and dual-beam(He^+/e^-) irradiations are performed at 350℃ and 400℃ using an ultra-high voltage electron microscope combined with ion accelerators. In-situ observation shows that the growth rate of dislocation loops is reduced in the helium pre-injected specimen. The mean size of cavities decreased in the helium preinjected specimen. The possible mechanisms are discussed.展开更多
Bulk Cu/V multilayers simultaneously possess high strength and excellent radiation resistance thanks to their high density of interfaces.Irradiation-induced atomic mixing of Cu/V multilayers has been less investigated...Bulk Cu/V multilayers simultaneously possess high strength and excellent radiation resistance thanks to their high density of interfaces.Irradiation-induced atomic mixing of Cu/V multilayers has been less investigated.Here,we investigate the ion irradiation of bulk Cu/V multilayers exposed to H2^+ or He^+ ions at 350℃.The microstructure and elemental distribution are investigated by transmission electron microscopy and energy dispersive x-ray spectroscopy.Facetted bubbles and atomic mixing are observed after ion irradiation.The possible mechanisms of irradiation-induced atomic mixing are discussed.展开更多
Cavities and extended defects formed in single crystalline and polycrystalline α-SiC implanted with H+ions are compared.The samples are investigated by cross-sectional transmission electron microscopy.H2 bubbles are ...Cavities and extended defects formed in single crystalline and polycrystalline α-SiC implanted with H+ions are compared.The samples are investigated by cross-sectional transmission electron microscopy.H2 bubbles are formed during H implantation and H2 molecules escape the sample to form cavities during thermal annealing at 1100℃.Microcracks and the extended defects prefer to nucleate in single crystalline α-SiC,but not polycrystalline α-Si C.Grain boundaries can account for the experimental results.The formation of cavities on grain boundaries is investigated.展开更多
Optical logic gates call for materials with giant optical nonlinearity to break the current performance bottleneck.Metal–organic frameworks(MOFs)provide an intriguing route to achieve superior optical nonlinearity be...Optical logic gates call for materials with giant optical nonlinearity to break the current performance bottleneck.Metal–organic frameworks(MOFs)provide an intriguing route to achieve superior optical nonlinearity benefitting from structural diversity and design flexibility.However,the potential of MOFs for optoelectronics has been largely overlooked and their applications in optical logic have not been exploited.Here,through temporally manipulating the nonlinear optical absorption process in porphyrin-based MOFs,we have successfully developed AND and XOR logic gates with an ultrafast speed approaching 1 THz and an on–off ratio above 90%.On this basis,all-optical information encryption is further demonstrated using transmittance as primary codes,which shows vast prospects in avoiding the disclosure of security information.To the best of our knowledge,this is the first exploration of MOFs for applications in ultrafast optical logic devices and information encryption.展开更多
Inefficient flotation of bastnaesite remains a challenge in the production of rare earth elements.This study aimed to investigate the dissolution and adsorption behaviour of species that are commonly released into bas...Inefficient flotation of bastnaesite remains a challenge in the production of rare earth elements.This study aimed to investigate the dissolution and adsorption behaviour of species that are commonly released into bastnaesite flotation pulp from Ca/Ba-bearing gangue minerals.The influence and corresponding mechanisms on the bastnaesite mineral surface and collectors,namely sodium oleate(NaOL),were evaluated experimentally based on micro-flotation,zeta potentials,in situ attenuated total reflection Fourier transform infrared spectroscopy(ATRFTIR),and X-Ray photoelectron spectroscopy(XPS)analyses.The flotation recovery of bastnaesite significantly decreased from ~95% to ~25%,~15%,~80%,~25% when exposed to calcite,fluorite,barite,and mixed dissolved species,respectively.The zeta potential of bastnaesite was pH sensitive,indicating that H^(+) and OH^(−)determine the surface potential of bastnaesite.Solution chemistry analyses revealed that the presence of the dissolved species differed at various pH values.In situ ATR-FTIR demonstrated the different effects of the dissolved species from calcite,fluorite,and barite on collector adsorption.The former two dissolved species mainly depressed the chemisorption of the NaOL monomers(RCOO^(-)),whereas calcite also affected the physical adsorption of the oleic acid molecular dimer(RCOOH·RCOO^(-)).Moreover,the barite dissolved species only affected the physical adsorption of the NaOL species.The results of XPS analysis revealed that dissolved species from these three gangues could pre-adsorbed onto bastnaesite and affected the interaction with the collector.Density functional theory calculations were employed to provide further theoretical insights into the interactions between the dissolved species from calcite,fluorite,and barite and NaOL.展开更多
The development of structural materials resistant to harsh radiation environments requires an in-depth understanding of the early stage of the aging processes.In radiation environments with high transmutation helium p...The development of structural materials resistant to harsh radiation environments requires an in-depth understanding of the early stage of the aging processes.In radiation environments with high transmutation helium production rates such as in fusion and spallation applications,even materials with otherwise acceptable radiation stability may suffer from radiation embrittlement related to helium bubble formation.While theoretical modeling of helium-assisted cavity nucleation in pure metals and simple alloys provides some useful guidelines at the atomic scale level,these,however,do not overlap with the size resolution of available experimental techniques.In this study,we employed slow positron beam spectroscopy to characterize the nucleation and growth of nano-scale helium bubbles in martensitic steels strengthened by thermodynamically stable nano-oxide dispersoids.In combination with transmission electron microscopy,we experimentally characterized the evolution of helium bubbles from small clusters of radiation-induced vacancies to large cavities well resolvable by TEM.Superior radiation resistance of oxide-dispersion strengthened steels dominates only in the early stages of bubble evolution,where positron lifetime measurements provide a missing piece of the microstructural puzzle conventionally constructed by TEM.展开更多
Color centers in silicon carbide(SiC)are promising candidates for quantum technologies.However,the richness of the polytype and defect configuration of SiC makes the accurate control of the types and position of defec...Color centers in silicon carbide(SiC)are promising candidates for quantum technologies.However,the richness of the polytype and defect configuration of SiC makes the accurate control of the types and position of defects in SiC still challenging.In this study,helium ion-implanted 4H-SiC was characterized by atomic force microscopy(AFM),confocal photoluminescence(PL),and confocal Raman spectroscopy at room temperature.PL signals of silicon vacancy were found and analyzed using 638-nm and 785-nm laser excitation by means of depth profiling and SWIFT mapping.Lattice defects(C-C bond)were detected by continuous laser excitation at 532 nm and 638 nm,respectively.PL/Raman depth profiling was helpful in revealing the three-dimensional distribution of produced defects.Differences in the depth profiling results and SRIM simulation results were explained by considering the depth resolution of the confocal measurement setup,helium bubbles,as well as swelling.展开更多
基金Project supported by the Science Challenge Project(Grant No.TZ2018001)the National Natural Science Foundation of China(Grant Nos.11872058 and 21802036)the Project of State Key Laboratory of Environment-friendly Energy Materials,and Southwest University of Science and Technology(Grant No.21fksy07)。
文摘Metal-organic frameworks(MOFs),which are self-assembled porous coordination materials,have garnered considerable attention in the fields of optoelectronics,photovoltaic,photochemistry,and photocatalysis due to their diverse structures and excellent tunability.However,the performance of MOF-based optoelectronic applications currently falls short of the industry benchmark.To enhance the performance of MOF materials,it is imperative to undertake comprehensive investigations aimed at gaining a deeper understanding of photophysics and sequentially optimizing properties related to photocarrier transport,recombination,interaction,and transfer.By utilizing femtosecond laser pulses to excite MOFs,time-resolved optical spectroscopy offers a means to observe and characterize these ultrafast microscopic processes.This approach adds the time coordinate as a novel dimension for comprehending the interaction between light and MOFs.Accordingly,this review provides a comprehensive overview of the recent advancements in the photophysics of MOFs and additionally outlines potential avenues for exploring the time domain in the investigation of MOFs.
基金supported by the National Natural Science Foundation of China (Grant No.12072331)the Science Challenge Project (Grant No.TZ2018001)+2 种基金the Japan Society for the Promotion of Science (Grant Nos.17H04820 and 21H01677)the Foundation of the United Laboratory of High-Pressure Physics and Earthquake Scienceperformed under the approval of the Photon Factory Program Advisory Committee (Proposal Nos.2016S2-006 and 2020G680)。
文摘A time-resolved x-ray diffraction technique is employed to monitor the structural transformation of laser-shocked bismuth.Results reveal a retarded transformation from the shock-induced Bi-Ⅴphase to a metastable Bi-Ⅳphase during the shock release,instead of the thermodynamically stable Bi-Ⅲphase.The emergence of the metastable Bi-Ⅳphase is understood by the competitive interplay between two transformation pathways towards the Bi-Ⅳand Bi-Ⅲ,respectively.The former is more rapid than the latter because the Bi-Ⅴto B-Ⅳtransformation is driven by interaction between the closest atoms while the Bi-Ⅴto B-Ⅲtransformation requires interaction between the second-closest atoms.The nucleation time for the Bi-Ⅴto Bi-Ⅳtransformation is determined to be 5.1±0.9 ns according to a classical nucleation model.This observation demonstrates the importance of the formation of the transient metastable phases,which can change the phase transformation pathway in a dynamic process.
基金Project supported by the Doctoral Research Fund of Southwest University of Science and Technology(Grant No.20zx7104)the Sichuan Science and Technology Program(Grant No.2020ZYD055)the National Natural Science Foundation of China(Grant Nos.11905206 and 12075194)。
文摘Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2)C-M_(t)C composite ceramic was prepared by hot press sintering,with the Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2)C high-entropy carbide as the main phase.Secondary phase M_(x)C(M=Ti,Zr,Hf,Nb,Ta) was found to be distributed relatively uniform in the composite ceramic.The oxidation behavior of the ceramic was examined after exposure to 923 K and 1173 K.Morphology of the surface and cross sections of all oxidation samples were observed.The characteristics of the oxidation behavior of the high-entropy carbide and the secondary phase M_(x)C were compared and analyzed.The secondary phases(such as Ti-rich carbide or Hf-rich carbide) in the material were seriously oxidized at 923 K and 1173 K,which reflects the superior oxidation performance of the high-entropy carbide.The nano high-entropy oxides with Ti,Zr,Hf,Nb,Ta,and O elements were discovered by oxidation of the composite ceramic.This research will help deepen the understanding of the oxidation mechanism of high-entropy carbide and composite ceramic.
基金supported by the National Natural Science Foundation of China(Nos.51922091,51674207,and 52004337)the Sichuan Science and Technology Program(Nos.2019YFS0453,2018JY0148 and SYZ202074).
文摘Here,the influence of grinding media with different shapes on the flotation performance of spodumene and its potential mechanism from microscale insights was investigated using a single mineral flotation experiment,X-ray diffraction(XRD)test,scanning electron microscopy combined with energy dispersive spectrometry(SEM-EDS),atomic force microscope(AFM)and X-ray photoelectron spectroscopy(XPS).The flotation data indicated that under anionic/cationic(sodium oleate(NaOL)/DDA)collectors system,the rod milled spodumene has a higher floatability than ball milled ones.XRD results confirmed that rod medium makes spodumene exposed more{110}and{100}planes,while ball medium makes spodumene exposed more{010}planes.The typical anisotropic surface of spodumene makes the surface of rod milled spodumene possess more Al sites,further confirmed by SEM-EDS and XPS results.Additionally,it was found that the rod milled spodumene presents a larger value of elongation and flatness,which are parameters closely related to bubble adhesion.AFM analysis indicated that rod milled products have a rougher surface,while ball milled products have a smoother surface.Consequently,the rod medium enhanced the adsorption of NaOL/DDA on the spodumene surfaces.This work provides theoretical guidance for optimizing the separation of spodumene from the perspective of grinding.
基金This work was supported by the National Natural Science Foundation of China(Nos.51904249 and 51922091)the Sichuan Science and Technology Program(No.SYZ202074)the Open Research Fund of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization(No.CNMRCUKF2001).
文摘This paper researched the enhanced flotation separation performance of ilmenite and titanaugite using the mixed collector benzhydroxamic acid/dodecylamine(BHA/DDA).The interface assembly mechanism was mainly investigated through in situ attenuated total reflectance Fourier transform infrared(ATRFTIR)spectroscopy combined with the two-dimensional correlation spectroscopy(2D-COS)and X-ray photoelectron spectroscopy(XPS).It has been found that BHA/DDA mixed collectors successfully separate ilmenite from titanaugite at a molar ratio of 8:1.Zeta potential experiments suggested that,in the presence of mixed collector system,the BHA-DDA complex adsorbed on the ilmenite surface via the chemically adsorbed BHA and the electrostatically adsorbed DDA,however,the complex adsorbed on the surface of titanaugite unstably.According to in situ ATR-FTIR combined with 2D-COS and XPS results,the interface assembly mechanism of BHA/DDA is summarized as:the function group of BHA molecules first binds to the metal sites on minerals to form bidentate ligand,then DDA co-adsorbed with BHA on the surface of minerals through hydrogen bonding.DDA may change the adsorption modes of some BHA on the ilmenite surface from four-membered ring to five-membered ring,while the modes on the titanaugite surface is true opposite.Finally,recommended adsorption configurations of the BHA/DDA complex on the two mineral surfaces are proposed.
基金Projects(51674207,51922091)supported by the National Natural Science Foundation of ChinaProject(2018QNRC001)supported by the Young Elite Scientists Sponsorship Program by CAST,ChinaProjects(2019YFS0453,2018JY0148)supported by the Sichuan Science and Technology Program,China。
基金Project supported by the National Natural Science Foundation of China(Grant No.12075194)Sichuan Science and Technology Program(Grant No.2020ZYD055)。
文摘A nano-twinned microstructure was found in amorphous SiC after high-temperature annealing.Grazing incidence x-ray diffraction,high-resolution transmission electron microscopy,and electron diffraction were performed to characterize the microstructure and phase transition in the recrystallization layer.After 1500℃or 2-h annealing,3C-SiC grains and numerous stacking faults on the{111}planes were visible.Some 3C-SiC grains have nano-twinned structure with{011}planes.Between the nano-twinned 3C-SiC grains,there is a stacking fault,indicating that the formation mechanisms of the nano-twinned structure are related to the disorder of Si atoms.The increase in the twin thickness with increasing annealing temperature demonstrates that the nano-twinned structure can sink for lattice defects,in order to improve the radiation tolerance of SiC.
文摘The CaCu3Ti4O12(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and electrical properties were investigated. The phase composition was determined by X-ray diffraction and the microstructure was examined by SEM. The dielectric constant, dielectric loss, and resistance of the ceramic were also determined by a precision impedance tester. The results show that, as the synthesis temperature increases, the CCTO ceramic grain size decreases and the stoichiometric ratio of Cu/Ca at the grain boundary increases, the dielectric constant increases and the dielectric loss decreases(40 < f < 10 kHz). In addition, when the synthesis time is shorter than 12 h, the Cu/Ca ratio of CCTO decreases and the dielectric constant increases with time increase. However, when the synthesis time exceeds 12 h, this trend is just the opposite. It is further proved that Cu at the grain boundary is not conducive to the dielectric constant of CCTO.
基金Project supported by the National Natural Science Foundation of China(Grant No.12075194)the Fund of Collage Student Innovation and Entrepreneurship Training Program(Grant No.S202010619053)。
文摘Chemical disorder on the surface and lattice strain in GaN implanted by Fe^(10+)ions are investigated.In this study,3-MeV Fe^(10+)ions fluence ranges from 1×10^(13)ions/cm^(2)to 5×10^(15)ions/cm^(2)at room temperature.X-ray photoelectron spectroscopy,high-resolution x-ray diffraction,and high-resolution transmission electron microscopy were used to characterize lattice disorder.The transition of Ga-N bonds to oxynitride bonding is caused by ion sputtering.The change of tensile strain out-of-plane with fluence was measured.Lattice disorder due to the formation of stacking faults prefers to occur on the basal plane.
基金Project supported by the National Natural Science Foundation of China(Grant No.U1832133)the Doctor Research Foundation of Southwest University of Science and Technology,China(Grant No.18zx7141).
文摘The formation of cavities in silicon carbide is vitally useful to“smart-cut”and metal gettering in semiconductor industry.In this study,cavities and extended defects formed in helium(He)ions implanted 6H-SiC at room temperature(RT)and 750℃ followed by annealing at 1500℃are investigated by a combination of transmission electron microscopy and high-resolution electron microscopy.The observed cavities and extended defects are related to the implantation temperature.Heterogeneously distributed cavities and extended defects are observed in the helium-implanted 6H-SiC at RT,while homogeneously distributed cavities and extended defects are formed after He-implanted 6H-SiC at 750℃.The possible reasons are discussed.
基金the National Natural Science Foundation of China(Grant Nos.U1832133 and 12075194)Sichuan Provial Science and Technology Program,China(Grant No.2020ZYD055)the Doctor Research Foundation of Southwest University of Science and Technology(Grant No.18zx714101).
文摘SIMP steel is newly developed fully martensitic steel for lead-cooled fast reactors and accelerator-driven systems.It is important to evaluate its radiation resistance via high flux neutron irradiation,where dense He atoms can be formed via(n,α)transmutation reaction.Co-irradiation with Fe and He ions,instead of neutron,was performed.Specimens were irradiated with 6.4-MeV Fe ions to the damage dose of 5 dpa at a depth of 600 nm.Three different helium injection ratios of 60-appm He/dpa(dpa:displacements per atom),200-appm He/dpa and 600-appm He/dpa at a depth of 600 nm,were performed.Two different irradiation temperatures of 300℃and 450℃were carried out.The effect of helium concentration on the microstructure of Fe-irradiated SIMP steel was investigated.Microstructural damage was observed using transmission electron microscopy.The formed dislocation loops and bubbles depended on the helium injection ratio and irradiation temperature.Lots of dislocation loops and helium bubbles were homogeneously distributed at 300℃,but not at 450℃.The causes of observed effects are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1832133 and 12075194)the Sichuan Science and Technology Program,China(Grant No.2020ZYD055)the Doctor Research Foundation of Southwest University of Science and Technology(Grant No.18zx714101).
文摘Ferritic-martensitic steels and ODS steels are attractive candidates for structural materials in advanced nuclear-power systems due to their good swelling resistance. Four kinds of steels, F82 H, 15 Cr-ODS, SIMP and T91, are investigated in this study. We take 6.4 Me V Fe3+ ions and energy-degraded 1.0 Me V He+ ions in the irradiation of these materials to 5 dpa and 60 appm He/dpa, 200 appm He/dpa and 600 appm He/dpa at 300℃ and 450℃, respectively. The bubble formation and distribution are investigated by transmission electron microscopy(TEM). Formation and distribution of the bubbles in the four investigated steels are compared. The influence of irradiation temperature and helium injection ratio on bubble formation is discussed. It is found that there appears to be homogenously distributed bubbles at 300℃ irradiation while heterogeneously distributed bubbles at 450℃ irradiation.
基金the National Natural Science Foundation of China(Grant No.12075194)the Sichuan Provincial Science and Technology Program,China(Grant No.2020ZYD055)the National Key Research and Development Program of China(Grant No.2017YFE0301306).
文摘Lattice defects induced by ion implantation into SiC have been widely investigated in the decades by various techniques.One of the non-destructive techniques suitable to study the lattice defects in SiC is the optical characterization.In this work,confocal Raman scattering spectroscopy and photoluminescence spectrum have been used to study the effects of 134-keV H_(2)^(+)implantation and thermal treatment in the microstructure of 6H-SiC single crystal.The radiation-induced changes in the microstructure were assessed by integrating Raman-scattering peaks intensity and considering the asymmetry of Raman-scattering peaks.The integrated intensities of Raman scattering spectroscopy and photoluminescence spectrum decrease with increasing the fluence.The recovery of the optical intensities depends on the combination of the implantation temperature and the annealing temperature with the thermal treatment from 700℃to 1100℃.The different characterizations of Raman scattering spectroscopy and photoluminescence spectrum are compared and discussed in this study.
基金the National Natural Science Foundation of China under Grant Nos U1832133,11475229 and 91426301
文摘Helium effects on dislocation and cavity formation of Fe-11 wt.% Cr model alloy are investigated. Single-beam(electron) and dual-beam(He^+/e^-) irradiations are performed at 350℃ and 400℃ using an ultra-high voltage electron microscope combined with ion accelerators. In-situ observation shows that the growth rate of dislocation loops is reduced in the helium pre-injected specimen. The mean size of cavities decreased in the helium preinjected specimen. The possible mechanisms are discussed.
基金Supported by the National Natural Science Foundation of China(Grant No.U1832133)。
文摘Bulk Cu/V multilayers simultaneously possess high strength and excellent radiation resistance thanks to their high density of interfaces.Irradiation-induced atomic mixing of Cu/V multilayers has been less investigated.Here,we investigate the ion irradiation of bulk Cu/V multilayers exposed to H2^+ or He^+ ions at 350℃.The microstructure and elemental distribution are investigated by transmission electron microscopy and energy dispersive x-ray spectroscopy.Facetted bubbles and atomic mixing are observed after ion irradiation.The possible mechanisms of irradiation-induced atomic mixing are discussed.
基金Supported by the National Natural Science Foundation of China(Grant Nos.U1832133 and 11905206)。
文摘Cavities and extended defects formed in single crystalline and polycrystalline α-SiC implanted with H+ions are compared.The samples are investigated by cross-sectional transmission electron microscopy.H2 bubbles are formed during H implantation and H2 molecules escape the sample to form cavities during thermal annealing at 1100℃.Microcracks and the extended defects prefer to nucleate in single crystalline α-SiC,but not polycrystalline α-Si C.Grain boundaries can account for the experimental results.The formation of cavities on grain boundaries is investigated.
基金supported by Science Challenge Project(no.TZ2018001)National Natural Science Foundation of China(nos.11872058 and 21802036)Project of State Key Laboratory of Environment-friendly Energy Materials,and Southwest University of Science and Technology(21fksy07).
文摘Optical logic gates call for materials with giant optical nonlinearity to break the current performance bottleneck.Metal–organic frameworks(MOFs)provide an intriguing route to achieve superior optical nonlinearity benefitting from structural diversity and design flexibility.However,the potential of MOFs for optoelectronics has been largely overlooked and their applications in optical logic have not been exploited.Here,through temporally manipulating the nonlinear optical absorption process in porphyrin-based MOFs,we have successfully developed AND and XOR logic gates with an ultrafast speed approaching 1 THz and an on–off ratio above 90%.On this basis,all-optical information encryption is further demonstrated using transmittance as primary codes,which shows vast prospects in avoiding the disclosure of security information.To the best of our knowledge,this is the first exploration of MOFs for applications in ultrafast optical logic devices and information encryption.
基金supported by the National Natural Science Foundation of China(Grants No.51922091 and 51874247).
文摘Inefficient flotation of bastnaesite remains a challenge in the production of rare earth elements.This study aimed to investigate the dissolution and adsorption behaviour of species that are commonly released into bastnaesite flotation pulp from Ca/Ba-bearing gangue minerals.The influence and corresponding mechanisms on the bastnaesite mineral surface and collectors,namely sodium oleate(NaOL),were evaluated experimentally based on micro-flotation,zeta potentials,in situ attenuated total reflection Fourier transform infrared spectroscopy(ATRFTIR),and X-Ray photoelectron spectroscopy(XPS)analyses.The flotation recovery of bastnaesite significantly decreased from ~95% to ~25%,~15%,~80%,~25% when exposed to calcite,fluorite,barite,and mixed dissolved species,respectively.The zeta potential of bastnaesite was pH sensitive,indicating that H^(+) and OH^(−)determine the surface potential of bastnaesite.Solution chemistry analyses revealed that the presence of the dissolved species differed at various pH values.In situ ATR-FTIR demonstrated the different effects of the dissolved species from calcite,fluorite,and barite on collector adsorption.The former two dissolved species mainly depressed the chemisorption of the NaOL monomers(RCOO^(-)),whereas calcite also affected the physical adsorption of the oleic acid molecular dimer(RCOOH·RCOO^(-)).Moreover,the barite dissolved species only affected the physical adsorption of the NaOL species.The results of XPS analysis revealed that dissolved species from these three gangues could pre-adsorbed onto bastnaesite and affected the interaction with the collector.Density functional theory calculations were employed to provide further theoretical insights into the interactions between the dissolved species from calcite,fluorite,and barite and NaOL.
基金the contribution of the Slovak Research and Development Agency under the project APVV-20-0010financial contributions from the Scientifc Grant Agency of the Ministry of Education,Science,Research and Sport of the Slovak Republic and the Slovak Academy of Sciences,grant numbers VEGA 1/0382/20 and VEGA 1/0395/20the European Regional Development Fund project No.ITMS2014+:313011W085。
文摘The development of structural materials resistant to harsh radiation environments requires an in-depth understanding of the early stage of the aging processes.In radiation environments with high transmutation helium production rates such as in fusion and spallation applications,even materials with otherwise acceptable radiation stability may suffer from radiation embrittlement related to helium bubble formation.While theoretical modeling of helium-assisted cavity nucleation in pure metals and simple alloys provides some useful guidelines at the atomic scale level,these,however,do not overlap with the size resolution of available experimental techniques.In this study,we employed slow positron beam spectroscopy to characterize the nucleation and growth of nano-scale helium bubbles in martensitic steels strengthened by thermodynamically stable nano-oxide dispersoids.In combination with transmission electron microscopy,we experimentally characterized the evolution of helium bubbles from small clusters of radiation-induced vacancies to large cavities well resolvable by TEM.Superior radiation resistance of oxide-dispersion strengthened steels dominates only in the early stages of bubble evolution,where positron lifetime measurements provide a missing piece of the microstructural puzzle conventionally constructed by TEM.
基金the National Natural Science Foundation of China(Nos.51575389,51761135106)National Key Research and Development Program of China(2016YFB1102203)+1 种基金State key laboratory of precision measuring technology and instruments(Piltl705)the‘111’Project by the State Administration of Foreign Experts Affairs and the Ministry of Education of China(Grant No.B07014)。
文摘Color centers in silicon carbide(SiC)are promising candidates for quantum technologies.However,the richness of the polytype and defect configuration of SiC makes the accurate control of the types and position of defects in SiC still challenging.In this study,helium ion-implanted 4H-SiC was characterized by atomic force microscopy(AFM),confocal photoluminescence(PL),and confocal Raman spectroscopy at room temperature.PL signals of silicon vacancy were found and analyzed using 638-nm and 785-nm laser excitation by means of depth profiling and SWIFT mapping.Lattice defects(C-C bond)were detected by continuous laser excitation at 532 nm and 638 nm,respectively.PL/Raman depth profiling was helpful in revealing the three-dimensional distribution of produced defects.Differences in the depth profiling results and SRIM simulation results were explained by considering the depth resolution of the confocal measurement setup,helium bubbles,as well as swelling.