Temperature-dependent resistivity,upper critical field H_(c2)and its anisotropy in overdoped superconducting Ba_(1-x)K_x Fe_2As_2(x=0.6-1)single crystals have been measured in steady magnetic fields up to 44 T and low...Temperature-dependent resistivity,upper critical field H_(c2)and its anisotropy in overdoped superconducting Ba_(1-x)K_x Fe_2As_2(x=0.6-1)single crystals have been measured in steady magnetic fields up to 44 T and low temperatures down to 0.4 K.Analysis using both the quadratic term and power-law fitting demonstrates that the in-plane resistivityρ_(ab)(T)progressively approaches the Fermi-liquid T~2behavior with increasing K doping and reaches a saturation plateau at x≈0.8.The temperature dependence of both H_(c2)^(ab)and H^(c)_(c2)follows the Werthamer-Helfand-Hohenberg model,incorporating orbital and spin paramagnetic effects.For x≤0.8,the orbital effect dominates for H ab,while the Pauli paramagnetic effect prevails for H c.For x>0.8,the Pauli paramagnetic effect becomes dominant in both crystallographic directions.The anisotropy of H_(c2)(0)exhibits a discontinuity in its dependence on K doping concentration with a significant enhancement at x=0.8 and a maximum at x=0.9.These experimental results indicate that the electron correlation effect is enhanced in the heavily overdoped Ba_(1-x)K_(x)Fe_(2)As_(2)system where the underlying symmetries are broken due to the Fermi surface reconstruction before x=0.9.展开更多
Light-energy-driven semiconductor catalysis offers attractive ways to address environmental and energy crises.TiO_(2) is the most promising catalyst for photocatalysis,but the lack of charge-carrier separation efficie...Light-energy-driven semiconductor catalysis offers attractive ways to address environmental and energy crises.TiO_(2) is the most promising catalyst for photocatalysis,but the lack of charge-carrier separation efficiency severely limits its catalytic performance.In this study,we carried out crystal phase engineering to prepare in situ Z-scheme hetero-phase homojunction of anatase-rutile and clarified the structure-performance relationship.The efficiency of sulfamerazine removal by hetero-phase homojunction TiO_(2) nanotube arrays in a single-compartment photocatalytic fuel cell system was improved by 1.93 times compared to conventional anatase TiO_(2) nanotube arrays and the degradation pathways were revealed by the Fukui function combined with HP-LCMS.The successful construction of Z-scheme hetero-phase homojunction was confirmed by Raman,X-ray diffraction(XRD),and electron spin resonance(ESR),which combined with density functional theory(DFT)calculations revealed the key role of crystal phase engineering in the construction of hetero-phase homojunction.This work provides a novel strategy for the scientific design of titanium dioxide photocatalysts.展开更多
Large-sized （～2 inch, 50.8 mm） γ-LiAlO2 single crystal has been grown by conventional Czochralski （Cz） method, but the crystal has a milky, dendriform center. The samples taken from transparent and milky parts w...Large-sized （～2 inch, 50.8 mm） γ-LiAlO2 single crystal has been grown by conventional Czochralski （Cz） method, but the crystal has a milky, dendriform center. The samples taken from transparent and milky parts were ground and examined by X-ray diffraction. All diffraction peaks could be indexed in γ-LiAlO2. The crystal quality was characterized by X-ray rocking curve. The full-width at half-maximum （FWHM） values are 116.9 and 132.0 arcsec for transparent and milky parts, respectively. The vapor transport equilibrium （VTE） technique was introduced to modify the crystal quality. After 1000℃/48 h, 1100℃/48 h, 1200℃/48 h VTE processes, the FWHM values dropped to 44.2 and 55.2 arcsec for transparent and milky part, respectively. The optical transmission of transparent part was greatly enhanced from 85% to 90%, and transmission of milky part from 75% to 80% in the range of 190~1900 nm at room temperature. When the VTE temperature was raised to 1300℃, the sample cracked and FWHM values of transparent and milky parts were increased to 55.2 and 80.9 arcsec, respectively. By combining Cz technique with VTE technique, large-sized and high quality γ-LiAlO2 crystal can be obtained.展开更多
The catalytic oxidation of HMF involves a cascading reaction with multiple intermediate products,making it crucial to enhance the oriented adsorption capacity of specific functional groups for accelerating the entire ...The catalytic oxidation of HMF involves a cascading reaction with multiple intermediate products,making it crucial to enhance the oriented adsorption capacity of specific functional groups for accelerating the entire process.To achieve the efficient selective oxidation of HMF to FDCA,a series of NiCo_(2)O_(4)catalysts with different morphologies,such as flaky,echinoids,pompon and corolla,were prepared and characterized by XRD,SEM,TEM,BET,XPS,and FTIR.Among the four catalysts,flaky NiCo_(2)O_(4)exhibited the most excellent catalytic activity and stability,with a FDCA yield of 60.1%within 12 h at 80℃without alkali participation.The excellent performance of flaky NiCo_(2)O_(4)catalyst is attributed to the oxygen vacancies and acid sites generated by the exposed(400)facets.The oxygen vacancies and acid sites on the catalyst surface can precisely adsorb-CHO and-CH_(2)-OH of HMF,respectively,and this synergistic effect promotes the efficient production of FDCA.This work is of great significance for fundamentally study the effect of micro-topography or crystal-plane reaction properties on surfaces.展开更多
Molybdenum(Mo)alloys are essential for applications requiring outstanding mechanical properties at high temperatures across various industrial sectors.Understanding and predicting the creep properties of Mo alloys is ...Molybdenum(Mo)alloys are essential for applications requiring outstanding mechanical properties at high temperatures across various industrial sectors.Understanding and predicting the creep properties of Mo alloys is crucial for service safety and the design of new materials.This study introduces a physicsbased crystallographic creep model dedicated to the characteristic hierarchical microstructure of Mo–La_(2)O_(3)alloys.By sourcing most parameters from existing literature and calibrating others within recommended ranges,the model efficiently predicts creep behavior beyond its initial calibration scope.Through the integration of microstructure descriptors,we systematically explored the impact of different microstructural features on the creep behavior and identified the underlying mechanisms.This analysis yielded two pivotal concepts:the minimum acceptable grain size and the necessary nanoparticle number density.These metrics,readily obtainable from the model,quantify the requisite grain size and nanoparticle content to achieve the target steady-state creep rates for operational demands,thus providing essential insights for the creep condition-oriented design of Mo–La_(2)O_(3)alloys.The model is also expected to be adaptable for developing other Mo alloys reinforced by second phase particles,aimed at achieving desired creep properties under specified conditions,assuming that relevant parameters are accessible through literature or lower-scale simulations.展开更多
The memory behavior in liquid crystals(LCs)that is characterized by low cost,large area,high speed,and high-density memory has evolved from a mere scientific curiosity to a technology that is being applied in a variet...The memory behavior in liquid crystals(LCs)that is characterized by low cost,large area,high speed,and high-density memory has evolved from a mere scientific curiosity to a technology that is being applied in a variety of commodities.In this study,we utilized molybdenum disulfide(MoS_(2))nanoflakes as the vip in a homotropic LCs host to modulate the overall memory effect of the hybrid.It was found that the MoS₂nanoflakes within the LCs host formed agglomerates,which in turn resulted in an accelerated response of the hybrids to the external electric field.However,this process also resulted in a slight decrease in the threshold voltage.Additionally,it was observed that MoS₂nanoflakes in a LCs host tend to align homeotropically under an external electric field,thereby accelerating the refreshment of the memory behavior.The incorporation of a mass fraction of 0.1%2μm MoS₂nanoflakes into the LCs host was found to significantly reduce the refreshing memory behavior in the hybrid to 94.0 s under an external voltage of 5 V.These findings illustrate the efficacy of regulating the rate of memory behavior for a variety of potential applications.展开更多
Two Gd_(2)complexes,namely[Gd_(2)(dbm)_(2)(HL_(1))_(2)(CH_(3)OH)_(2)]·4CH_(3)OH(1)and[Gd_(2)(dbm)_(2)(L_(2))_(2)(CH_(3)OH)_(2)]·2CH_(3)OH(2),where H_(3)L_(1)=(Z)-N'-[4-(diethylamino)-2-hydroxybenzylidene...Two Gd_(2)complexes,namely[Gd_(2)(dbm)_(2)(HL_(1))_(2)(CH_(3)OH)_(2)]·4CH_(3)OH(1)and[Gd_(2)(dbm)_(2)(L_(2))_(2)(CH_(3)OH)_(2)]·2CH_(3)OH(2),where H_(3)L_(1)=(Z)-N'-[4-(diethylamino)-2-hydroxybenzylidene]-2-hydroxyacetohydrazide,H_(2)L_(2)=(E)-N'-(5-bromo-2-hydroxy-3-methoxybenzylidene)nicotinohydrazide,Hdbm=dibenzoylmethane,have been constructed by adopting the solvothermal method.Structural characterization unveils that both complexes 1 and 2 are constituted by two Gd^(3+)ions,two dbm-ions,two CH_(3)OH molecules,and two polydentate Schiff-base ligands(HL_(1)^(2-)or L_(2)^(2-)).In addition,complex 1 contains four free methanol molecules,whereas complex 2 harbors two free methanol molecules.By investigating the interactions between complexes 1 and 2 and four types of bacteria(Bacillus subtilis,Escherichia coli,Staphylococcus aureus,Candida albicans),it was found that both complexes 1 and 2 exhibited potent antibacte-rial activities.The interaction mechanisms between the ligands H_(3)L_(1),H_(2)L_(2),complexes 1 and 2,and calf thymus DNA(CT-DNA)were studied using ultraviolet-visible spectroscopy,fluorescence titration,and cyclic voltammetry.The results demonstrated that both complexes 1 and 2 can intercalate into CT-DNA molecules,thereby inhibiting bacterial proliferation to achieve the antibacterial effects.CCDC:2401116,1;2401117,2.展开更多
As an ultrathin wide-bandgap(WBG)material,CaNb_(2)O_(6)exhibits excellent optical and electrical properties.Particularly,its highly asymmetric crystal structure provides new opportunities for designing novel nanodevic...As an ultrathin wide-bandgap(WBG)material,CaNb_(2)O_(6)exhibits excellent optical and electrical properties.Particularly,its highly asymmetric crystal structure provides new opportunities for designing novel nanodevices with directional functionality.However,due to the significant challenges in applying conventional techniques to nanoscale samples,the in-plane anisotropy of CaNb_(2)O_(6)has still remained unexplored.Here,we leverage the resonant nanoelectromechanical systems(NEMS)platform to successfully quantify both the mechanical and thermal anisotropies in such an ultrathin WBG crystal.Specifically,by measuring the dynamic response in both spectral and spatial domains,we determine the anisotropic Young’s modulus of CaNb_(2)O_(6)as E_(Y(a))=70.42 GPa and EY(b)=116.2 GPa.By further expanding this technique to cryogenic temperatures,we unveil the anisotropy in thermal expansion coefficients as α_((a))=13.4 ppm·K^(-1),α(b)=2.9 ppm·K^(-1).Interestingly,through thermal strain engineering,we successfully modulate the mode sequence and achieve a crossing of(1×2)-(2×1)modes with perfect degeneracy.Our study provides guidelines for future CaNb_(2)O_(6)nanodevices with additional degrees of freedom and new device functions.展开更多
In this study,a batch of φ12 mm Cs_(2)LiYCl_(6):Ce crystals codoped with different contents of Cu^(+)and Sc^(3+)was successfully grown using the Multi-ampule Bridgeman method.A new emission peaking at 418 nm is found...In this study,a batch of φ12 mm Cs_(2)LiYCl_(6):Ce crystals codoped with different contents of Cu^(+)and Sc^(3+)was successfully grown using the Multi-ampule Bridgeman method.A new emission peaking at 418 nm is found in the photoluminescence spectra of CLYC:Ce codoped with Cu^(+)ion.Codoping Cu^(+)or Sc^(3+)both increases the proportion of intrinsic self-trapped exciton(STE)luminescence,and extends the excitation band of Ce^(3+),especially in Cu^(+)codoped samples,where a new absorption peak at 248 nm can be identified.The light yield of Cu^(+)codoped samples remains largely unchanged,but the energy resolution shows a slight deterioration.Both light yield and energy resolution degrade after Sc^(3+)codoping,and the effect is much severe than that of Cu^(+)codoped samples.X-ray induced afterglow can be suppressed after Cu^(+)codoping and low content of Sc^(3+)codoping.The scintillation decay variation also depends on the codoping ions and their contents.展开更多
The preparation of high-strengthα-hemihydrate gypsum(α-HH)from dihydrate gypsum(DH)is a potential way to improve the utilization rate of industrial gypsum.α-HH with a low aspect ratio was prepared by atmospheric sa...The preparation of high-strengthα-hemihydrate gypsum(α-HH)from dihydrate gypsum(DH)is a potential way to improve the utilization rate of industrial gypsum.α-HH with a low aspect ratio was prepared by atmospheric salt solution method,using Mg(NO_(3))_(2)solution as the salt medium.The effects of reaction temperature,reaction time,Mg(NO_(3))_(2)concentration,pH value,and the solid-to-liquid ratio on the purity,yield and aspect ratio of the product were investigated systematically.Under the optimal reaction conditions of 95℃,4 h,40%(mass)Mg(NO_(3))_(2),pH 5,and a solid—liquid ratio of 1:5,the yield and purity of the product could reach 89.67%and 99.85%,respectively.Additionally,the average aspect ratio of this product was 2.02,and the compressive strength reached 58.2 MPa.The regulation mechanism was studied by calculating the adsorption energies of Mg(NO_(3))_(2)on different crystal planes ofα-HH,which indicated that Mg(NO_(3))_(2)exhibited the strongest adsorption on the(111)plane,and this preferential adsorption retarded the axial growth ofα-HH,resulting in a reduced aspect ratio of the crystals.These findings suggest that the Mg(NO_(3))_(2)solution is an effective approach for preparing highstrengthα-HH with controlled morphology.展开更多
We report the magnetic and transport properties of EuBi_(2) single crystal. EuBi_(2) exhibits complex magnetic behavior at low temperatures. In both the in-plane and out-of-plane directions, three antiferromagnetic(AF...We report the magnetic and transport properties of EuBi_(2) single crystal. EuBi_(2) exhibits complex magnetic behavior at low temperatures. In both the in-plane and out-of-plane directions, three antiferromagnetic(AFM) transitions have been observed at T_(N1)~18.9 K, T_(N2)~7.0 K, and T_(N3)~3.1 K. Among them, the transitions at T_(N2) and T_(N3) represent the canted AFM orders with ferromagnetic components. As the magnetic field increases, the transition at T_(N3) is rapidly suppressed to disappearance. However, the transitions at T_(N1) and T_(N2) persist until high fields and their signatures can also be reflected in the resistivity and specific heat. Above the magnetic transition temperature T_(N1), the resistivity of EuBi_(2) increases linearly with temperature, exhibiting the strange-metal behavior. In the magnetically ordered region below T_(N1), EuBi_(2) exhibits the weak antilocalization(WAL) effect and large magnetoresistance(475% at 1.8 K and 14 T). It is suggested that the magnetic ordering significantly enhances the spin–orbital coupling interaction and induces the WAL effect.展开更多
Catalytic oxidation is an effective strategy for eliminating CO pollutant.Pt/TiO_(2) catalyst are one of the most active catalysts as used,but facing the issue of sulfur and water deactivation.In this study,TiO_(2) wa...Catalytic oxidation is an effective strategy for eliminating CO pollutant.Pt/TiO_(2) catalyst are one of the most active catalysts as used,but facing the issue of sulfur and water deactivation.In this study,TiO_(2) was synthesized using a sol-gel method,while Pt/TiO_(2) was prepared by impregnation method.By varying the calcination temperature of the TiO_(2) support,Pt/TiO_(2) catalysts with different proportions of anatase and rutile phases were synthesized.At the calcination temperature of 500℃,the catalysts exhibited approximately equal proportions of anatase and rutile,resulting in exceptional catalytic activity for CO oxidation,as well as improved resistance to sulfur and water in the flue gas.Consequently,the Pt/TiO_(2)-500 catalyst achieved a CO conversion of 93%at 160℃.Even under conditions of 8%(vol)H_(2)O and 0.016%(vol)SO_(2)(GHSV=300000 ml·h^(-1)·g^(-1)),the CO conversion remained above 95%at 220℃for 46 h.The catalysts were characterized and analyzed using various techniques.The results indicated that anatasephase TiO_(2) exhibited weak CO adsorption capacity but strong SO_(2) adsorption capacity,whereas rutilephase TiO_(2) demonstrated strong CO adsorption capacity and weak SO_(2) adsorption capacity.The presence of the anatase phase mitigated the CO self-poisoning phenomenon of the catalyst,while the biphase interface reduced the adsorption and oxidation of SO_(2) on the catalyst's surface,significantly inhibiting the deposition of TiOSO_4.Consequently,the Pt/TiO_(2)-500 catalyst displayed the highest CO catalytic activity along with superior resistance to sulfur and water.展开更多
Birefringent crystals play an irreplaceable role in optical systems by adjusting the polarization state of light in optical devices.This work successfully synthesized a new thiophosphate phase ofβ-Pb_(3)P_(2)S_(8)thr...Birefringent crystals play an irreplaceable role in optical systems by adjusting the polarization state of light in optical devices.This work successfully synthesized a new thiophosphate phase ofβ-Pb_(3)P_(2)S_(8)through the high-temperature solid-state spontaneous crystallization method.Different from the cubicα-Pb_(3)P_(2)S_(8),theβ-Pb_(3)P_(2)S_(8)crystallizes in the orthorhombic Pbcn space group.Notably,β-Pb_(3)P_(2)S_(8)shows a large band gap of 2.37 e V in lead-based chalcogenides,wide infrared transparent window(2.5-15μm),and excellent thermal stability.Importantly,the experimental birefringence shows the largest value of0.26@550 nm in chalcogenides,even larger than the commercialized oxide materials.The Barder charge analysis result indicates that the exceptional birefringence effect is mainly from the Pb^(2+)and S^(2-)in the[Pb S_n]polyhedrons.Meanwhile,the parallelly arranged polyhedral layers could improve the structural anisotropic.Therefore,this work supports a new method for designing chalcogenides with exceptional birefringence effect in the infrared region.展开更多
SnSe_(2) single crystals,as novel n-type plastic thermoelectric materials,present advantages such as envi-ronmental sustainability and cost-effectiveness.Single crystals of SnSe_(2)+x%PbBr_(2)(x=0,0.5,1,2,and 3)with l...SnSe_(2) single crystals,as novel n-type plastic thermoelectric materials,present advantages such as envi-ronmental sustainability and cost-effectiveness.Single crystals of SnSe_(2)+x%PbBr_(2)(x=0,0.5,1,2,and 3)with large size and high quality were successfully synthesized via the Bridgman method.The significant enhancement in power factor and effective suppression of lattice thermal conductivity can be achieved through PbBr_(2) doping,verifying a synergistic optimization of electrical and thermal transport properties.Specifically,Br atoms are effectively incorporated into the Se sites to manipulate the carrier concentra-tion and optimize the power factor,while simultaneously inducing a strong phonon softening effect by introducing Pb atoms at the Sn sites,which leads to a reduced phonon group velocity and a suppres-sion of lattice thermal conductivity.Consequently,SnSe_(2)+2%PbBr_(2) single-crystal sample achieves a peak figure of merit zT of~0.76 and an average zT of~0.51,giving rise to corresponding improvements of~533% and~538%,respectively,compared to the pristine SnSe_(2) sample,thereby outperforming most of the previously reported SnSe_(2)-based materials.This work provides a viable approach for promoting the thermoelectric performance of SnSe^(2)-based single crystals across a broad temperature range and supports the advancement of plastic thermoelectric materials.展开更多
The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wav...The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wavelength of 1.5μm.In this study,Co^(2+)ions were introduced into the wide bandgap semiconductor material ZnGa_(2)O_(4),and large-sized and high-quality Co^(2+)-doped ZnGa_(2)O_(4)crystals with a volume of about 20 cm^(3)were grown using the vertical gradient freeze(VGF)method.Crystal structure and optical properties were analyzed using X-ray powder diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and absorption spectroscopy.XRD results show that the Co^(2+)-doped ZnGa_(2)O_(4)crystal has a pure spinel phase without impurity phases and the rocking curve full width at half maximum(FWHM)is only 58 arcsec.The concentration of Co^(2+)in Co^(2+)-doped ZnGa_(2)O_(4)crystals was determined to be 0.2 at.%by the energy dispersive X-ray spectroscopy.The optical band gap of Co^(2+)-doped ZnGa_(2)O_(4)crystals is 4.44 eV.The optical absorption spectrum for Co^(2+)-doped ZnGa_(2)O_(4)reveals a prominent visible absorption band within 550−670 nm and a wide absorption band spanning from 1100 to 1700 nm.This suggests that the Co^(2+)ions have substituted the Zn^(2+)ions,which are typically tetrahedrally coordinated,within the lattice structure of ZnGa_(2)O_(4).The visible region's absorption peak and the near-infrared broad absorption band are ascribed to the^(4)A_(2)(4F)→^(4)T_(1)(4P)and 4A2(4F)→^(4)T_(1)(4F)transitions,respectively.The optimal ground state absorption cross section was determined to be 3.07×10^(−19)cm^(2)in ZnGa_(2)O_(4),a value that is comparatively large within the context of similar materials.This finding suggests that ZnGa_(2)O_(4)is a promising candidate for use in near-infrared passive Q-switched solid-state lasers.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2024YFA1611100,2023YFA1406100,and 2018YFA0704201)the Systematic Fundamental Research Program Leveraging Major Scientific and Technological Infrastructure,Chinese Academy of Sciences(Grant No.JZHKYPT-2021-08)+1 种基金the National Natural Science Foundation of China(Grant Nos.11704385,11874359,and 12274444)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)。
文摘Temperature-dependent resistivity,upper critical field H_(c2)and its anisotropy in overdoped superconducting Ba_(1-x)K_x Fe_2As_2(x=0.6-1)single crystals have been measured in steady magnetic fields up to 44 T and low temperatures down to 0.4 K.Analysis using both the quadratic term and power-law fitting demonstrates that the in-plane resistivityρ_(ab)(T)progressively approaches the Fermi-liquid T~2behavior with increasing K doping and reaches a saturation plateau at x≈0.8.The temperature dependence of both H_(c2)^(ab)and H^(c)_(c2)follows the Werthamer-Helfand-Hohenberg model,incorporating orbital and spin paramagnetic effects.For x≤0.8,the orbital effect dominates for H ab,while the Pauli paramagnetic effect prevails for H c.For x>0.8,the Pauli paramagnetic effect becomes dominant in both crystallographic directions.The anisotropy of H_(c2)(0)exhibits a discontinuity in its dependence on K doping concentration with a significant enhancement at x=0.8 and a maximum at x=0.9.These experimental results indicate that the electron correlation effect is enhanced in the heavily overdoped Ba_(1-x)K_(x)Fe_(2)As_(2)system where the underlying symmetries are broken due to the Fermi surface reconstruction before x=0.9.
基金supported by the National Natural Science Foundation of China(Nos.52370025,52372212)BUCEA Postgraduate Education and Teaching Quality Improvement Project(No.J2023016)the BUCEA Post Graduate Innovation Project(Nos.DG2023012 and PG2024073).
文摘Light-energy-driven semiconductor catalysis offers attractive ways to address environmental and energy crises.TiO_(2) is the most promising catalyst for photocatalysis,but the lack of charge-carrier separation efficiency severely limits its catalytic performance.In this study,we carried out crystal phase engineering to prepare in situ Z-scheme hetero-phase homojunction of anatase-rutile and clarified the structure-performance relationship.The efficiency of sulfamerazine removal by hetero-phase homojunction TiO_(2) nanotube arrays in a single-compartment photocatalytic fuel cell system was improved by 1.93 times compared to conventional anatase TiO_(2) nanotube arrays and the degradation pathways were revealed by the Fukui function combined with HP-LCMS.The successful construction of Z-scheme hetero-phase homojunction was confirmed by Raman,X-ray diffraction(XRD),and electron spin resonance(ESR),which combined with density functional theory(DFT)calculations revealed the key role of crystal phase engineering in the construction of hetero-phase homojunction.This work provides a novel strategy for the scientific design of titanium dioxide photocatalysts.
文摘Large-sized （～2 inch, 50.8 mm） γ-LiAlO2 single crystal has been grown by conventional Czochralski （Cz） method, but the crystal has a milky, dendriform center. The samples taken from transparent and milky parts were ground and examined by X-ray diffraction. All diffraction peaks could be indexed in γ-LiAlO2. The crystal quality was characterized by X-ray rocking curve. The full-width at half-maximum （FWHM） values are 116.9 and 132.0 arcsec for transparent and milky parts, respectively. The vapor transport equilibrium （VTE） technique was introduced to modify the crystal quality. After 1000℃/48 h, 1100℃/48 h, 1200℃/48 h VTE processes, the FWHM values dropped to 44.2 and 55.2 arcsec for transparent and milky part, respectively. The optical transmission of transparent part was greatly enhanced from 85% to 90%, and transmission of milky part from 75% to 80% in the range of 190~1900 nm at room temperature. When the VTE temperature was raised to 1300℃, the sample cracked and FWHM values of transparent and milky parts were increased to 55.2 and 80.9 arcsec, respectively. By combining Cz technique with VTE technique, large-sized and high quality γ-LiAlO2 crystal can be obtained.
基金supported by the Swedish Energy Agency(P47500-1)the National Key R&D Program of China(2020YFA0710200)+2 种基金the National Natural Science Foundation of China(22378401 and U22A20416)the financial support from STINT(CH2019-8287)financial support from the European Union and Swedish Energy Agency(P2020-90066).
文摘The catalytic oxidation of HMF involves a cascading reaction with multiple intermediate products,making it crucial to enhance the oriented adsorption capacity of specific functional groups for accelerating the entire process.To achieve the efficient selective oxidation of HMF to FDCA,a series of NiCo_(2)O_(4)catalysts with different morphologies,such as flaky,echinoids,pompon and corolla,were prepared and characterized by XRD,SEM,TEM,BET,XPS,and FTIR.Among the four catalysts,flaky NiCo_(2)O_(4)exhibited the most excellent catalytic activity and stability,with a FDCA yield of 60.1%within 12 h at 80℃without alkali participation.The excellent performance of flaky NiCo_(2)O_(4)catalyst is attributed to the oxygen vacancies and acid sites generated by the exposed(400)facets.The oxygen vacancies and acid sites on the catalyst surface can precisely adsorb-CHO and-CH_(2)-OH of HMF,respectively,and this synergistic effect promotes the efficient production of FDCA.This work is of great significance for fundamentally study the effect of micro-topography or crystal-plane reaction properties on surfaces.
基金financially supported by the National Natural Science Foundation of China(Nos.52371119,51901173,U23A6013,92360301,U2330203,and 51801147)National Key Research and Development Program of China(No.2017YFB0702301)+1 种基金Shaanxi Province Youth Innovation Team(No.22JP042)Shaanxi Province Innovation Team Project(No.2024RS-CXTD-58).
文摘Molybdenum(Mo)alloys are essential for applications requiring outstanding mechanical properties at high temperatures across various industrial sectors.Understanding and predicting the creep properties of Mo alloys is crucial for service safety and the design of new materials.This study introduces a physicsbased crystallographic creep model dedicated to the characteristic hierarchical microstructure of Mo–La_(2)O_(3)alloys.By sourcing most parameters from existing literature and calibrating others within recommended ranges,the model efficiently predicts creep behavior beyond its initial calibration scope.Through the integration of microstructure descriptors,we systematically explored the impact of different microstructural features on the creep behavior and identified the underlying mechanisms.This analysis yielded two pivotal concepts:the minimum acceptable grain size and the necessary nanoparticle number density.These metrics,readily obtainable from the model,quantify the requisite grain size and nanoparticle content to achieve the target steady-state creep rates for operational demands,thus providing essential insights for the creep condition-oriented design of Mo–La_(2)O_(3)alloys.The model is also expected to be adaptable for developing other Mo alloys reinforced by second phase particles,aimed at achieving desired creep properties under specified conditions,assuming that relevant parameters are accessible through literature or lower-scale simulations.
文摘The memory behavior in liquid crystals(LCs)that is characterized by low cost,large area,high speed,and high-density memory has evolved from a mere scientific curiosity to a technology that is being applied in a variety of commodities.In this study,we utilized molybdenum disulfide(MoS_(2))nanoflakes as the vip in a homotropic LCs host to modulate the overall memory effect of the hybrid.It was found that the MoS₂nanoflakes within the LCs host formed agglomerates,which in turn resulted in an accelerated response of the hybrids to the external electric field.However,this process also resulted in a slight decrease in the threshold voltage.Additionally,it was observed that MoS₂nanoflakes in a LCs host tend to align homeotropically under an external electric field,thereby accelerating the refreshment of the memory behavior.The incorporation of a mass fraction of 0.1%2μm MoS₂nanoflakes into the LCs host was found to significantly reduce the refreshing memory behavior in the hybrid to 94.0 s under an external voltage of 5 V.These findings illustrate the efficacy of regulating the rate of memory behavior for a variety of potential applications.
文摘Two Gd_(2)complexes,namely[Gd_(2)(dbm)_(2)(HL_(1))_(2)(CH_(3)OH)_(2)]·4CH_(3)OH(1)and[Gd_(2)(dbm)_(2)(L_(2))_(2)(CH_(3)OH)_(2)]·2CH_(3)OH(2),where H_(3)L_(1)=(Z)-N'-[4-(diethylamino)-2-hydroxybenzylidene]-2-hydroxyacetohydrazide,H_(2)L_(2)=(E)-N'-(5-bromo-2-hydroxy-3-methoxybenzylidene)nicotinohydrazide,Hdbm=dibenzoylmethane,have been constructed by adopting the solvothermal method.Structural characterization unveils that both complexes 1 and 2 are constituted by two Gd^(3+)ions,two dbm-ions,two CH_(3)OH molecules,and two polydentate Schiff-base ligands(HL_(1)^(2-)or L_(2)^(2-)).In addition,complex 1 contains four free methanol molecules,whereas complex 2 harbors two free methanol molecules.By investigating the interactions between complexes 1 and 2 and four types of bacteria(Bacillus subtilis,Escherichia coli,Staphylococcus aureus,Candida albicans),it was found that both complexes 1 and 2 exhibited potent antibacte-rial activities.The interaction mechanisms between the ligands H_(3)L_(1),H_(2)L_(2),complexes 1 and 2,and calf thymus DNA(CT-DNA)were studied using ultraviolet-visible spectroscopy,fluorescence titration,and cyclic voltammetry.The results demonstrated that both complexes 1 and 2 can intercalate into CT-DNA molecules,thereby inhibiting bacterial proliferation to achieve the antibacterial effects.CCDC:2401116,1;2401117,2.
基金supported by the National Key R&D Program of China(2022YFB3203600)the National Natural Science Foundation of China(Grant Nos.T2325007,62450003,62401104,62404029,U21A20459,62250073,61774029,and U23A20570)+1 种基金the China Postdoctoral Science Foundation(Grant Nos.GZB20230107 and GZB20240109)the Natural Science Foundation of Sichuan Province(Grant Nos.2024NSFSC1430 and 2024NSFSC1408).
文摘As an ultrathin wide-bandgap(WBG)material,CaNb_(2)O_(6)exhibits excellent optical and electrical properties.Particularly,its highly asymmetric crystal structure provides new opportunities for designing novel nanodevices with directional functionality.However,due to the significant challenges in applying conventional techniques to nanoscale samples,the in-plane anisotropy of CaNb_(2)O_(6)has still remained unexplored.Here,we leverage the resonant nanoelectromechanical systems(NEMS)platform to successfully quantify both the mechanical and thermal anisotropies in such an ultrathin WBG crystal.Specifically,by measuring the dynamic response in both spectral and spatial domains,we determine the anisotropic Young’s modulus of CaNb_(2)O_(6)as E_(Y(a))=70.42 GPa and EY(b)=116.2 GPa.By further expanding this technique to cryogenic temperatures,we unveil the anisotropy in thermal expansion coefficients as α_((a))=13.4 ppm·K^(-1),α(b)=2.9 ppm·K^(-1).Interestingly,through thermal strain engineering,we successfully modulate the mode sequence and achieve a crossing of(1×2)-(2×1)modes with perfect degeneracy.Our study provides guidelines for future CaNb_(2)O_(6)nanodevices with additional degrees of freedom and new device functions.
基金Project supported by the National Key Research and Development Program,China(2022YFB3503600)Manned Space Station Engineering Space Science and Applications Program(MSAP)(ZDBS-ZRKJZTLC011)+3 种基金National Natural Science Foundation of China,China(11975303,12211530561,12305211)Shanghai Municipal Natural Science Foundation,China(21TS1400100)CAS Cooperative Research Project(121631KYSB20210017)CAS Project for Young Scientist in Basic Research(YSBR-024)。
文摘In this study,a batch of φ12 mm Cs_(2)LiYCl_(6):Ce crystals codoped with different contents of Cu^(+)and Sc^(3+)was successfully grown using the Multi-ampule Bridgeman method.A new emission peaking at 418 nm is found in the photoluminescence spectra of CLYC:Ce codoped with Cu^(+)ion.Codoping Cu^(+)or Sc^(3+)both increases the proportion of intrinsic self-trapped exciton(STE)luminescence,and extends the excitation band of Ce^(3+),especially in Cu^(+)codoped samples,where a new absorption peak at 248 nm can be identified.The light yield of Cu^(+)codoped samples remains largely unchanged,but the energy resolution shows a slight deterioration.Both light yield and energy resolution degrade after Sc^(3+)codoping,and the effect is much severe than that of Cu^(+)codoped samples.X-ray induced afterglow can be suppressed after Cu^(+)codoping and low content of Sc^(3+)codoping.The scintillation decay variation also depends on the codoping ions and their contents.
基金financial supported by the Opening Project of Hubei Yihua-Sichuan University Joint Innovation Research Center for new chemical materials(24H1402)Fundamental Research Funds for the Central Universities(SCU2024D009)the National Key Research and Development Program of China(2019YFC1905800)。
文摘The preparation of high-strengthα-hemihydrate gypsum(α-HH)from dihydrate gypsum(DH)is a potential way to improve the utilization rate of industrial gypsum.α-HH with a low aspect ratio was prepared by atmospheric salt solution method,using Mg(NO_(3))_(2)solution as the salt medium.The effects of reaction temperature,reaction time,Mg(NO_(3))_(2)concentration,pH value,and the solid-to-liquid ratio on the purity,yield and aspect ratio of the product were investigated systematically.Under the optimal reaction conditions of 95℃,4 h,40%(mass)Mg(NO_(3))_(2),pH 5,and a solid—liquid ratio of 1:5,the yield and purity of the product could reach 89.67%and 99.85%,respectively.Additionally,the average aspect ratio of this product was 2.02,and the compressive strength reached 58.2 MPa.The regulation mechanism was studied by calculating the adsorption energies of Mg(NO_(3))_(2)on different crystal planes ofα-HH,which indicated that Mg(NO_(3))_(2)exhibited the strongest adsorption on the(111)plane,and this preferential adsorption retarded the axial growth ofα-HH,resulting in a reduced aspect ratio of the crystals.These findings suggest that the Mg(NO_(3))_(2)solution is an effective approach for preparing highstrengthα-HH with controlled morphology.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2023YFA1406500)the National Natural Science Foundation of China (Grant Nos. 12474098, 12274388, 12174361, 12404191, 52102333, 12404043, and 12204004)the Natural Science Foundation of Anhui Province (Grant No. 2408085QA024)。
文摘We report the magnetic and transport properties of EuBi_(2) single crystal. EuBi_(2) exhibits complex magnetic behavior at low temperatures. In both the in-plane and out-of-plane directions, three antiferromagnetic(AFM) transitions have been observed at T_(N1)~18.9 K, T_(N2)~7.0 K, and T_(N3)~3.1 K. Among them, the transitions at T_(N2) and T_(N3) represent the canted AFM orders with ferromagnetic components. As the magnetic field increases, the transition at T_(N3) is rapidly suppressed to disappearance. However, the transitions at T_(N1) and T_(N2) persist until high fields and their signatures can also be reflected in the resistivity and specific heat. Above the magnetic transition temperature T_(N1), the resistivity of EuBi_(2) increases linearly with temperature, exhibiting the strange-metal behavior. In the magnetically ordered region below T_(N1), EuBi_(2) exhibits the weak antilocalization(WAL) effect and large magnetoresistance(475% at 1.8 K and 14 T). It is suggested that the magnetic ordering significantly enhances the spin–orbital coupling interaction and induces the WAL effect.
基金financially supported by the National Key Research&Development Program of China(2024YFC3908400)the National Natural Science Foundation of China(U21B2099)Fundamental Research Funds for the Central Universities,Ocean University of China(202364004)。
文摘Catalytic oxidation is an effective strategy for eliminating CO pollutant.Pt/TiO_(2) catalyst are one of the most active catalysts as used,but facing the issue of sulfur and water deactivation.In this study,TiO_(2) was synthesized using a sol-gel method,while Pt/TiO_(2) was prepared by impregnation method.By varying the calcination temperature of the TiO_(2) support,Pt/TiO_(2) catalysts with different proportions of anatase and rutile phases were synthesized.At the calcination temperature of 500℃,the catalysts exhibited approximately equal proportions of anatase and rutile,resulting in exceptional catalytic activity for CO oxidation,as well as improved resistance to sulfur and water in the flue gas.Consequently,the Pt/TiO_(2)-500 catalyst achieved a CO conversion of 93%at 160℃.Even under conditions of 8%(vol)H_(2)O and 0.016%(vol)SO_(2)(GHSV=300000 ml·h^(-1)·g^(-1)),the CO conversion remained above 95%at 220℃for 46 h.The catalysts were characterized and analyzed using various techniques.The results indicated that anatasephase TiO_(2) exhibited weak CO adsorption capacity but strong SO_(2) adsorption capacity,whereas rutilephase TiO_(2) demonstrated strong CO adsorption capacity and weak SO_(2) adsorption capacity.The presence of the anatase phase mitigated the CO self-poisoning phenomenon of the catalyst,while the biphase interface reduced the adsorption and oxidation of SO_(2) on the catalyst's surface,significantly inhibiting the deposition of TiOSO_4.Consequently,the Pt/TiO_(2)-500 catalyst displayed the highest CO catalytic activity along with superior resistance to sulfur and water.
基金supported in part by the National Natural Science Foundation of China(No.52102218)the National Key Research and Development Program of China(No.2020YFA0710303)+2 种基金the Fujian Science&Technology Innovation Laboratory for Op-toelectronic Information of China(No.2021ZZ127)the Minjiang Scholar Professorship(No.GXRC-21004)the Natural Science Foundation of Fujian Province of China(No.2021J01594)。
文摘Birefringent crystals play an irreplaceable role in optical systems by adjusting the polarization state of light in optical devices.This work successfully synthesized a new thiophosphate phase ofβ-Pb_(3)P_(2)S_(8)through the high-temperature solid-state spontaneous crystallization method.Different from the cubicα-Pb_(3)P_(2)S_(8),theβ-Pb_(3)P_(2)S_(8)crystallizes in the orthorhombic Pbcn space group.Notably,β-Pb_(3)P_(2)S_(8)shows a large band gap of 2.37 e V in lead-based chalcogenides,wide infrared transparent window(2.5-15μm),and excellent thermal stability.Importantly,the experimental birefringence shows the largest value of0.26@550 nm in chalcogenides,even larger than the commercialized oxide materials.The Barder charge analysis result indicates that the exceptional birefringence effect is mainly from the Pb^(2+)and S^(2-)in the[Pb S_n]polyhedrons.Meanwhile,the parallelly arranged polyhedral layers could improve the structural anisotropic.Therefore,this work supports a new method for designing chalcogenides with exceptional birefringence effect in the infrared region.
基金financially supported by the National Natural Science Foundation of China(Nos.52125103,52371212,52071041,12204080,12374002)the Scientific and Technological Research Program of Chongqing Municipal Education Commission(Nos.KJQN202400604,KJQN202200623,KJZD-K202100602)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.2024IAIS-ZX002,2023CDJKYJH006)the Natural Science Foundation of Chongqing(No.CSTB2022NSCQ-MSX0382).
文摘SnSe_(2) single crystals,as novel n-type plastic thermoelectric materials,present advantages such as envi-ronmental sustainability and cost-effectiveness.Single crystals of SnSe_(2)+x%PbBr_(2)(x=0,0.5,1,2,and 3)with large size and high quality were successfully synthesized via the Bridgman method.The significant enhancement in power factor and effective suppression of lattice thermal conductivity can be achieved through PbBr_(2) doping,verifying a synergistic optimization of electrical and thermal transport properties.Specifically,Br atoms are effectively incorporated into the Se sites to manipulate the carrier concentra-tion and optimize the power factor,while simultaneously inducing a strong phonon softening effect by introducing Pb atoms at the Sn sites,which leads to a reduced phonon group velocity and a suppres-sion of lattice thermal conductivity.Consequently,SnSe_(2)+2%PbBr_(2) single-crystal sample achieves a peak figure of merit zT of~0.76 and an average zT of~0.51,giving rise to corresponding improvements of~533% and~538%,respectively,compared to the pristine SnSe_(2) sample,thereby outperforming most of the previously reported SnSe_(2)-based materials.This work provides a viable approach for promoting the thermoelectric performance of SnSe^(2)-based single crystals across a broad temperature range and supports the advancement of plastic thermoelectric materials.
基金the support by the fund of the National Key Research and Development Program of China (Grant No. 2024YFA1208800)National Natural Science Foundation of China (NSFC) (Grant No. U23A20358)+2 种基金Natural Science Foundation of Shandong Province (Grant Nos. ZR2023ZD05 and 2022TSGC2120)the Shenzhen Fundamental Research Program (Grant No. GJHZ20220913142605011)Xiaomi Foundation/Xiaomi Young Talents Program
文摘The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wavelength of 1.5μm.In this study,Co^(2+)ions were introduced into the wide bandgap semiconductor material ZnGa_(2)O_(4),and large-sized and high-quality Co^(2+)-doped ZnGa_(2)O_(4)crystals with a volume of about 20 cm^(3)were grown using the vertical gradient freeze(VGF)method.Crystal structure and optical properties were analyzed using X-ray powder diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and absorption spectroscopy.XRD results show that the Co^(2+)-doped ZnGa_(2)O_(4)crystal has a pure spinel phase without impurity phases and the rocking curve full width at half maximum(FWHM)is only 58 arcsec.The concentration of Co^(2+)in Co^(2+)-doped ZnGa_(2)O_(4)crystals was determined to be 0.2 at.%by the energy dispersive X-ray spectroscopy.The optical band gap of Co^(2+)-doped ZnGa_(2)O_(4)crystals is 4.44 eV.The optical absorption spectrum for Co^(2+)-doped ZnGa_(2)O_(4)reveals a prominent visible absorption band within 550−670 nm and a wide absorption band spanning from 1100 to 1700 nm.This suggests that the Co^(2+)ions have substituted the Zn^(2+)ions,which are typically tetrahedrally coordinated,within the lattice structure of ZnGa_(2)O_(4).The visible region's absorption peak and the near-infrared broad absorption band are ascribed to the^(4)A_(2)(4F)→^(4)T_(1)(4P)and 4A2(4F)→^(4)T_(1)(4F)transitions,respectively.The optimal ground state absorption cross section was determined to be 3.07×10^(−19)cm^(2)in ZnGa_(2)O_(4),a value that is comparatively large within the context of similar materials.This finding suggests that ZnGa_(2)O_(4)is a promising candidate for use in near-infrared passive Q-switched solid-state lasers.
