Crystal-field symmetry of lanthanide ions plays a critical role in suppressing quantum tunneling of magnetization(QTM)in single-molecule magnets(SMMs),but high-performance SMM design and modulation remain challenging ...Crystal-field symmetry of lanthanide ions plays a critical role in suppressing quantum tunneling of magnetization(QTM)in single-molecule magnets(SMMs),but high-performance SMM design and modulation remain challenging only in view of the geometric symmetry of the first coordination sphere.Herein,two bis(semicarbazone)/bis(thiosemicarbazone)dysprosium singleion magnets with pentagonal bipyramid geometry were reported,and bis(thiosemicarbazone)lanthanide complexes have never been reported to the best of our knowledge.They served as good archetypes to study the magneto-structural relationships based on the charge distribution.The complex with more ideal geometric symmetry displays fast zero-field QTM with negligible“effective barrier”,owing to the defective charge distribution.By modulating the transverse crystal field via the replacement of the O sites with the less charged and larger radius S atoms,it results in lower geometric but higher charge-distribution symmetry,giving rise to the significant suppression of QTM and the enhancement of reversal barrier up to ca.1,000 K.These results demonstrate that the charge-distribution symmetry can be chemically tailored by modification of the crystal field,which is essential for designing high-performance SMMs.展开更多
Honeycomb composite films were prepared by breath figure method via a straightforward,one-step process by doping complex containing Eu or Sn into polystyrene-b-poly(acrylic acid) solution.Several key influencing facto...Honeycomb composite films were prepared by breath figure method via a straightforward,one-step process by doping complex containing Eu or Sn into polystyrene-b-poly(acrylic acid) solution.Several key influencing factors,such as the concentration of the block polymer solution,the relative humidity of the environment and the amount of complexes,were investigated to control micropore size and tune film surface properties.The characteristics of the composite films were studied by scanning electron microscopy(SEM),atomic force microscopy(AFM),X-ray diffraction(XRD),ultraviolet and emission spectra.Results indicate that composite films containing Eu have excellent optical performance,and micro-patterned bowl-like SnO_(2) microparticles could be fabricated from composite films containing Sn after being calcined at 600℃ for 5 h.This general approach for the fabrication of honeycomb composite films opens a convenient and effective route to the functional modification of honeycomb films and offers new prospects for the application in miniaturized sensors,micro-reactor and catalysis.展开更多
A microstructure composed of martensite matrix,lower bainite,and stable film-like austenite was designed by a quenching and isothermal bainitic holding process in a 0.30C–2.69Mn–1.71Si(wt.%)steel.The yield strength,...A microstructure composed of martensite matrix,lower bainite,and stable film-like austenite was designed by a quenching and isothermal bainitic holding process in a 0.30C–2.69Mn–1.71Si(wt.%)steel.The yield strength,tensile strength,and ductile-to-brittle transition temperature(DBTT)of the high-strength steel thus obtained were 1263 MPa,1521 MPa,and-33℃,respectively,and at-20℃,it showed superior low-temperature toughness,which reached 77.5 J/cm^(2).Meanwhile,it showed excellent hydrogen embrittlement(HE)resistance,and the total elongation loss is only 3.1%after 15 min of hydrogen charging.The excellent comprehensive performance is attributed to the fact that fine stable austenite with film-like morphology hindered the crack nucleation and propagation,and hindered hydrogen diffusion as a hydrogen trap.However,with a decrease in the isothermal temperature,transition carbide precipitation was accompanied by a further decrease in austenite grain size.For this condition,although transition carbides can act as effective hydrogen traps,excessive precipitation decreased the carbon content of retained austenite and increased the deformation heterogeneity between austenite and martensite matrix,leading to weakened austenite stability and HE resistance,a total elongation loss of approximately 39%(15 min hydrogen charging),a sharp decrease in impact toughness,and an increase in DBTT.The competitive role of film-like austenite and transition carbides on the comprehensive mechanical performance of steel is revealed,especially the suppression of crack nucleation and propagation that will provide a guide for the design of high strength steels with excellent impact toughness and HE resistance.展开更多
Luminescent polystyrene microspheres were easily fabricated from poly(styrene-co-methacrylic acid)and aqueous RE(III) chloride solution(RE=Eu, Tb) in the presence of 2,20-bipyridine as second ligand. The negative char...Luminescent polystyrene microspheres were easily fabricated from poly(styrene-co-methacrylic acid)and aqueous RE(III) chloride solution(RE=Eu, Tb) in the presence of 2,20-bipyridine as second ligand. The negative charges of carboxyl groups on the surface of microspheres coordinated with rare earth ions at first, such as complexes covalently linked to 2,20-bipyridine, resulting in strong photoluminescence. Various methods, including transmission electron microscope(TEM), scanning electron microscope(SEM), energy dispersive spectroscopy(EDS),Fourier transform infrared spectroscopy(FT-IR), and fluorescence spectrophotometer, were used to characterize the resultant polystyrene composite microspheres. This work highlights the idea that it is facile to synthesis luminescent microspheres by surface-modified method directly.展开更多
La-doped Sr-hexaferrite(Sr(1-x)LaxFe(12)O(19))(x=0.05,0.10,0.15,0.20) nanopowders with particle size ranging from 80 to 110 nm were successfully synthesized by sol-gel auto-combustion. The phase formation te...La-doped Sr-hexaferrite(Sr(1-x)LaxFe(12)O(19))(x=0.05,0.10,0.15,0.20) nanopowders with particle size ranging from 80 to 110 nm were successfully synthesized by sol-gel auto-combustion. The phase formation temperature increases, while the particle size decreases as the Ladoping content goes up. The partial substitution of Sr^(2+) by La^(3+) results in the suppression effects on the growth-up of the crystallites and the enhancement of the electron hopping between Fe^(3+) with different valences, which leads to the improvement in the dielectric loss and magnetic loss.Therefore, both the microwave absorbing abilities and absorbing frequency ranges are tuned by La-doping. The synthesized Sr-hexaferrite nanopowders with doping element content of 0.10 demonstrate the fine broad microwave absorbing properties.展开更多
Single-molecule magnets(SMMs)are regarded as promising candidates for ultrahigh-density storage,quantum information processing and molecular spintronics.It is a crucial challenge for chemists to modulate magnetic dyna...Single-molecule magnets(SMMs)are regarded as promising candidates for ultrahigh-density storage,quantum information processing and molecular spintronics.It is a crucial challenge for chemists to modulate magnetic dynamics of SMMs.Here,we successfully synthesized two 3d-4f polynuclear compounds[Co_2Dy(TTTT^(Cl))_2(MeOH)]NO_3·3MeOH(1)and[Co_2Dy(TTTT^(Cl))_2(MeOH)][Co(HTTTT^(Cl))](NO_3)_2·2.5MeOH·2H_2O(2),where H_3TTTT^(Cl)=2,2′,2′′-(((nitrilotris(ethane-2,1-diyl))tris(azanediyl))tris(methylene))tris-(4-chlorophenol).On applying the approach by co-crystallization of bulky diamagnetic moiety,the effective energy barrier enhances from 401 K(1)to 536 K(2),which are both among the highest d-f heterometallic SMMs.展开更多
Hydrated ferric oxide(HFO)has high adsorption efficiency for As(Ⅲ).However,its high self-aggregation usually reduces the efficiency and limits the scaledup application.Herein,biochar(BC),with large surface area and a...Hydrated ferric oxide(HFO)has high adsorption efficiency for As(Ⅲ).However,its high self-aggregation usually reduces the efficiency and limits the scaledup application.Herein,biochar(BC),with large surface area and amounts of surface functional groups was used to tune the loading and distribution of HFO to prepare an efficient adsorbent(HFO/BC)via in-situ synthesis method.The influence of the mass ratio of iron salt to BC on HFO/BC morphology was investigated,and the mechanism was discussed.The results showed that novel HFO was formed and distributed uniformly on the surface of BC when the mass ratio of iron salt to BC was 5:1.The adsorption kinetics and isotherms studies show that the novel HFO/BC(5:1)composite can fast treat As(Ⅲ)with a high adsorption capacity of 104.55 mg·g^(-1),indicating that it is a potential material for removing arsenic from polluted water.展开更多
To prepare tungsten/rubber composites with good gamma-ray shielding performances and fine mechanical properties,a composite surface modifier is employed to make surface modification of the tungsten powders.
Single-phase SrM ultrafine powders with single-domain particle ranging from 200 to 400 nm in size were successfully synthesized by a cetyltrimethylammonium bromide(CTAB)-as sis ted co-precipitation method,and excell...Single-phase SrM ultrafine powders with single-domain particle ranging from 200 to 400 nm in size were successfully synthesized by a cetyltrimethylammonium bromide(CTAB)-as sis ted co-precipitation method,and excellent magnetic properties with saturation magnetization of 68.6 A·m^2·kg^(-1) and coercive field of 0.5250 T are obtained.As CTAB content exceeds 5.0 wt%,the impurities emerge due to the deterioration of simultaneous precipitations of the starting materials and the deviation of Sr/Fe molar ratio from stoichiometry ratio in the local microdomains by employing CTAB in co-precipitation process.Also,the use of CTAB can effectively improve the homogeneities of Fe-precursor particles with Sr-precursor particles,exert surface barriers to inhibit interdiffusion,and constrain the crystal growth in the local microdomains during sintering,resulting in smaller particle sizes and more uniform particle size distribution.展开更多
The high phase content of inorganic dielectric fillings will give a strong electric driving force and hard matrix. That is a contradiction in enhancing the electrodeformation of dielectric elastomers(DEs). Therefore, ...The high phase content of inorganic dielectric fillings will give a strong electric driving force and hard matrix. That is a contradiction in enhancing the electrodeformation of dielectric elastomers(DEs). Therefore, in this paper, by focusing on how to approach a balance between these and finding an effective way to tune the electric response of the DEs, the theoretical calculation and experimental investigation based on calcium copper titanate(CCTO)/poly(dimethyl siloxane)(PDMS) were carried out. It is found that CCTO with a smaller particle size shows a larger dielectric parameter. With smaller CCTO particle as the fillings, the fabricated elastomer composite would approach to a low modulus by a proper CCTO phase morphology in the matrix.展开更多
Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating,especially for single-molecule magnets(SMMs).Herein a family of dysprosium single-ion magnets(SIMs)sitting in pentagonal...Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating,especially for single-molecule magnets(SMMs).Herein a family of dysprosium single-ion magnets(SIMs)sitting in pentagonal bipyramid geometry have been synthesized with the variable-size terminal ligands and counter anions,through which the subtle coordination geometry of Dy(Ⅲ)can be finely tuned based on the size effect.The effective energy barrier(Ueff)successfully increases from 439 to 632 K and the magnetic hysteresis temperature(under a 200 Oe/s sweep rate)raises from 11 to 24 K.Based on the crystal-field theory,a semi-quantitative magneto-structural correlation deduced experimentally for the first time is revealed that the Ueff is linearly proportional to the structural-related value S20 corresponding to the axial coordination bond lengths and the bond angles.Through the evaluation of the remanent magnetization from hysteresis,quantum tunneling of magnetization(QTM)is found to exhibit negative correlation with the structural-related value Stun corresponding to the axial coordination bond angles.展开更多
基金supported by the National Key Research and Development Program of China(2018YFA0306001)the National Natural Science Foundation of China(22073115,22105230,22131011,21821003)the Pearl River Talent Plan of Guangdong(2017BT01C161)
文摘Crystal-field symmetry of lanthanide ions plays a critical role in suppressing quantum tunneling of magnetization(QTM)in single-molecule magnets(SMMs),but high-performance SMM design and modulation remain challenging only in view of the geometric symmetry of the first coordination sphere.Herein,two bis(semicarbazone)/bis(thiosemicarbazone)dysprosium singleion magnets with pentagonal bipyramid geometry were reported,and bis(thiosemicarbazone)lanthanide complexes have never been reported to the best of our knowledge.They served as good archetypes to study the magneto-structural relationships based on the charge distribution.The complex with more ideal geometric symmetry displays fast zero-field QTM with negligible“effective barrier”,owing to the defective charge distribution.By modulating the transverse crystal field via the replacement of the O sites with the less charged and larger radius S atoms,it results in lower geometric but higher charge-distribution symmetry,giving rise to the significant suppression of QTM and the enhancement of reversal barrier up to ca.1,000 K.These results demonstrate that the charge-distribution symmetry can be chemically tailored by modification of the crystal field,which is essential for designing high-performance SMMs.
基金financially supported by the National Natural Science Foundation of China (Nos.51403181, 51273172 and 21375116)。
文摘Honeycomb composite films were prepared by breath figure method via a straightforward,one-step process by doping complex containing Eu or Sn into polystyrene-b-poly(acrylic acid) solution.Several key influencing factors,such as the concentration of the block polymer solution,the relative humidity of the environment and the amount of complexes,were investigated to control micropore size and tune film surface properties.The characteristics of the composite films were studied by scanning electron microscopy(SEM),atomic force microscopy(AFM),X-ray diffraction(XRD),ultraviolet and emission spectra.Results indicate that composite films containing Eu have excellent optical performance,and micro-patterned bowl-like SnO_(2) microparticles could be fabricated from composite films containing Sn after being calcined at 600℃ for 5 h.This general approach for the fabrication of honeycomb composite films opens a convenient and effective route to the functional modification of honeycomb films and offers new prospects for the application in miniaturized sensors,micro-reactor and catalysis.
基金the National Key R&D Program of China(No.2021YFB3702401)Major Program of the National Natural Science Foundation of China(No.52293394)the National Natural Science Foundation of China(Nos.U1564203,51571141 and 51201105).
文摘A microstructure composed of martensite matrix,lower bainite,and stable film-like austenite was designed by a quenching and isothermal bainitic holding process in a 0.30C–2.69Mn–1.71Si(wt.%)steel.The yield strength,tensile strength,and ductile-to-brittle transition temperature(DBTT)of the high-strength steel thus obtained were 1263 MPa,1521 MPa,and-33℃,respectively,and at-20℃,it showed superior low-temperature toughness,which reached 77.5 J/cm^(2).Meanwhile,it showed excellent hydrogen embrittlement(HE)resistance,and the total elongation loss is only 3.1%after 15 min of hydrogen charging.The excellent comprehensive performance is attributed to the fact that fine stable austenite with film-like morphology hindered the crack nucleation and propagation,and hindered hydrogen diffusion as a hydrogen trap.However,with a decrease in the isothermal temperature,transition carbide precipitation was accompanied by a further decrease in austenite grain size.For this condition,although transition carbides can act as effective hydrogen traps,excessive precipitation decreased the carbon content of retained austenite and increased the deformation heterogeneity between austenite and martensite matrix,leading to weakened austenite stability and HE resistance,a total elongation loss of approximately 39%(15 min hydrogen charging),a sharp decrease in impact toughness,and an increase in DBTT.The competitive role of film-like austenite and transition carbides on the comprehensive mechanical performance of steel is revealed,especially the suppression of crack nucleation and propagation that will provide a guide for the design of high strength steels with excellent impact toughness and HE resistance.
基金financially supported by the National Natural Science Fundation of China (No.50873085)
文摘Luminescent polystyrene microspheres were easily fabricated from poly(styrene-co-methacrylic acid)and aqueous RE(III) chloride solution(RE=Eu, Tb) in the presence of 2,20-bipyridine as second ligand. The negative charges of carboxyl groups on the surface of microspheres coordinated with rare earth ions at first, such as complexes covalently linked to 2,20-bipyridine, resulting in strong photoluminescence. Various methods, including transmission electron microscope(TEM), scanning electron microscope(SEM), energy dispersive spectroscopy(EDS),Fourier transform infrared spectroscopy(FT-IR), and fluorescence spectrophotometer, were used to characterize the resultant polystyrene composite microspheres. This work highlights the idea that it is facile to synthesis luminescent microspheres by surface-modified method directly.
基金financially supported by the National Natural Science Foundation of China(No.51103125)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(Chemistry)+2 种基金the Natural Science Foundation of Yangzhou(No.YZ2014043)the Science Innovative Foundation of Yangzhou University(No.2014CXJ017)the Graduate Student Innovation foundation of Yangzhou University(No.CXLX 1413)
文摘La-doped Sr-hexaferrite(Sr(1-x)LaxFe(12)O(19))(x=0.05,0.10,0.15,0.20) nanopowders with particle size ranging from 80 to 110 nm were successfully synthesized by sol-gel auto-combustion. The phase formation temperature increases, while the particle size decreases as the Ladoping content goes up. The partial substitution of Sr^(2+) by La^(3+) results in the suppression effects on the growth-up of the crystallites and the enhancement of the electron hopping between Fe^(3+) with different valences, which leads to the improvement in the dielectric loss and magnetic loss.Therefore, both the microwave absorbing abilities and absorbing frequency ranges are tuned by La-doping. The synthesized Sr-hexaferrite nanopowders with doping element content of 0.10 demonstrate the fine broad microwave absorbing properties.
基金supported by the National Natural Science Foundation of China (21620102002, 91422302, 21701198)the Fundamental Research Funds for the Central Universities (17lgjc13, 17lgpy81)
文摘Single-molecule magnets(SMMs)are regarded as promising candidates for ultrahigh-density storage,quantum information processing and molecular spintronics.It is a crucial challenge for chemists to modulate magnetic dynamics of SMMs.Here,we successfully synthesized two 3d-4f polynuclear compounds[Co_2Dy(TTTT^(Cl))_2(MeOH)]NO_3·3MeOH(1)and[Co_2Dy(TTTT^(Cl))_2(MeOH)][Co(HTTTT^(Cl))](NO_3)_2·2.5MeOH·2H_2O(2),where H_3TTTT^(Cl)=2,2′,2′′-(((nitrilotris(ethane-2,1-diyl))tris(azanediyl))tris(methylene))tris-(4-chlorophenol).On applying the approach by co-crystallization of bulky diamagnetic moiety,the effective energy barrier enhances from 401 K(1)to 536 K(2),which are both among the highest d-f heterometallic SMMs.
基金the National Natural Science Foundation of China(No.52173208)the Priority Academic Program Development of Jiangsu Higher Education Institutions and Qing Lan Project of Yangzhou University(Dr.LJL)。
文摘Hydrated ferric oxide(HFO)has high adsorption efficiency for As(Ⅲ).However,its high self-aggregation usually reduces the efficiency and limits the scaledup application.Herein,biochar(BC),with large surface area and amounts of surface functional groups was used to tune the loading and distribution of HFO to prepare an efficient adsorbent(HFO/BC)via in-situ synthesis method.The influence of the mass ratio of iron salt to BC on HFO/BC morphology was investigated,and the mechanism was discussed.The results showed that novel HFO was formed and distributed uniformly on the surface of BC when the mass ratio of iron salt to BC was 5:1.The adsorption kinetics and isotherms studies show that the novel HFO/BC(5:1)composite can fast treat As(Ⅲ)with a high adsorption capacity of 104.55 mg·g^(-1),indicating that it is a potential material for removing arsenic from polluted water.
基金financially supported by the National Natural Science Foundation of China (No. 52078247)Qing Lan Project of Yangzhou University (Dr. LJL)
文摘To prepare tungsten/rubber composites with good gamma-ray shielding performances and fine mechanical properties,a composite surface modifier is employed to make surface modification of the tungsten powders.
基金financially supported by the National Natural Science Foundation of China(No.51103125)the China Postdoctoral Science Foundation(No.2015M570483)+1 种基金the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions,the Natural Science Foundation of Yangzhou(No.YZ2014043)the Science Innovative Foundation of Yangzhou University(No.2014CXJ017)
文摘Single-phase SrM ultrafine powders with single-domain particle ranging from 200 to 400 nm in size were successfully synthesized by a cetyltrimethylammonium bromide(CTAB)-as sis ted co-precipitation method,and excellent magnetic properties with saturation magnetization of 68.6 A·m^2·kg^(-1) and coercive field of 0.5250 T are obtained.As CTAB content exceeds 5.0 wt%,the impurities emerge due to the deterioration of simultaneous precipitations of the starting materials and the deviation of Sr/Fe molar ratio from stoichiometry ratio in the local microdomains by employing CTAB in co-precipitation process.Also,the use of CTAB can effectively improve the homogeneities of Fe-precursor particles with Sr-precursor particles,exert surface barriers to inhibit interdiffusion,and constrain the crystal growth in the local microdomains during sintering,resulting in smaller particle sizes and more uniform particle size distribution.
基金financially supported by the National Natural Science Foundation of China(Nos.51403181 and 51678292)the China Postdoctoral Science Foundation(Nos.2016T90512 and 2015M570483)the Scholarship of Jiangsu Government for Oversea Study and the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(Chemistry)。
文摘The high phase content of inorganic dielectric fillings will give a strong electric driving force and hard matrix. That is a contradiction in enhancing the electrodeformation of dielectric elastomers(DEs). Therefore, in this paper, by focusing on how to approach a balance between these and finding an effective way to tune the electric response of the DEs, the theoretical calculation and experimental investigation based on calcium copper titanate(CCTO)/poly(dimethyl siloxane)(PDMS) were carried out. It is found that CCTO with a smaller particle size shows a larger dielectric parameter. With smaller CCTO particle as the fillings, the fabricated elastomer composite would approach to a low modulus by a proper CCTO phase morphology in the matrix.
基金supported by the National Key Research and Development Program of China(2018YFA0306001)the National Natural Sciences foundation of China(21620102002,21822508,21821003)the Pearl River Talent Plan of Guangdong(2017BT01C161)。
文摘Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating,especially for single-molecule magnets(SMMs).Herein a family of dysprosium single-ion magnets(SIMs)sitting in pentagonal bipyramid geometry have been synthesized with the variable-size terminal ligands and counter anions,through which the subtle coordination geometry of Dy(Ⅲ)can be finely tuned based on the size effect.The effective energy barrier(Ueff)successfully increases from 439 to 632 K and the magnetic hysteresis temperature(under a 200 Oe/s sweep rate)raises from 11 to 24 K.Based on the crystal-field theory,a semi-quantitative magneto-structural correlation deduced experimentally for the first time is revealed that the Ueff is linearly proportional to the structural-related value S20 corresponding to the axial coordination bond lengths and the bond angles.Through the evaluation of the remanent magnetization from hysteresis,quantum tunneling of magnetization(QTM)is found to exhibit negative correlation with the structural-related value Stun corresponding to the axial coordination bond angles.