Transportation structures such as composite pavements and railway foundations typically consist of multi-layered media designed to withstand high bearing capacity.A theoretical understanding of load transfer mechanism...Transportation structures such as composite pavements and railway foundations typically consist of multi-layered media designed to withstand high bearing capacity.A theoretical understanding of load transfer mechanisms in these multi-layer composites is essential,as it offers intuitive insights into parametric influences and facilitates enhanced structural performance.This paper employs an improved transfer matrix method to address the limitations of existing theoretical approaches for analyzing multi-layer composite structures.By establishing a twodimensional composite pavement model,it investigates load transfer characteristics and validates the accuracy through finite element simulation.The proposed method offers a straightforward analytical approach for examining internal interactions between structural layers.Case studies indicate that the concrete surface layer is the main load-bearing layer for most vertical normal and shear stresses.The soil base layer reduces the overall mechanical response of the substructure,while horizontal actions increase the risk of interfacial slip and cracking.Structural optimization analysis demonstrates that increasing the thickness of the concrete surface layer,enhancing the thickness and stiffness of the soil base layer,or incorporating gradient layers can significantly mitigate these risks of interfacial slip and cracking.The findings of this study can guide the optimization design,parameter analysis,and damage prevention of multi-layer composite structures.展开更多
Rare earth elements(REEs) are associated with phosphorite,which is an important strategic reserve resource.During sorting process of phosphorite,REEs may move with specific host minerals,however,occurrence state and m...Rare earth elements(REEs) are associated with phosphorite,which is an important strategic reserve resource.During sorting process of phosphorite,REEs may move with specific host minerals,however,occurrence state and moving pattern of REEs from rock to products are still unclear,which limits separation and enrichment of REEs from phosphorite.Mappings of scanning electron microscope(SEM) and electron probe X-ray micro-analyzer(EPMA) of REEs are highly consistent with those of calcium and phosphorus,and complementary with that of magnesium,which indicates that fluorapatite(Fap) is the main host mineral of REEs.The results of flotation and leaching experiments further indicate that REEs are enriched along with Fap from phosphorite to products.Occupied sites and occupation number of REEs were obtained by X-ray diffraction(XRD) refinement based on the Rietveld method.La,Ce,Nd,and Y can occupy both Ca1 and Ca2 sites.The ratios of La,Ce,Nd,and Y at Ca2 and Cal sites are 4.20,3.70,3.00,and 1.33,showing a decreasing trend,indicating that La,Ce,and Nd tend to occupy Ca2 sites,while Y tends to occupy Ca1 sites.X-ray absorption fine structure(XAFS) shows that REEs mainly form coordinate structures with oxygen and fluorine,which is a direct evidence that REEs replace calcium(Ⅱ) in phosphorite in an isomorphism form.Coordination structure and polyhedral configuration analysis indicate that substitution degree of La,Ce,Nd,and Y is Y> La> Ce≈Nd from easy to difficult at Cal and Ca2 sites.The research enriches the mineralization theory of REEs-bearing phosphorite and provides certain theoretical guidance for selective enrichment of REEs from phosphorite.展开更多
A two-dimensional electromagnetic particle-in-cell simulation model is proposed to study the density evolution and collective stopping of electron beams in background plasmas.We show here the formation of the multi-la...A two-dimensional electromagnetic particle-in-cell simulation model is proposed to study the density evolution and collective stopping of electron beams in background plasmas.We show here the formation of the multi-layer structure of the relativistic electron beam in the plasma due to the different betatron frequency from the beam front to the beam tail.Meanwhile,the nonuniformity of the longitudinal wakefield is the essential reason for the multi-layer structure formation in beam phase space.The influences of beam parameters(beam radius and transverse density profile)on the formation of the multi-layer structure and collective stopping in background plasmas are also considered.展开更多
With the continuous improvement of China's science and technology, the design method of steel structure is also more and more, how to better apply the module building design method to the related buildings, is the...With the continuous improvement of China's science and technology, the design method of steel structure is also more and more, how to better apply the module building design method to the related buildings, is the current issue to focus on consideration. Therefore, this paper will focus on the design method of multi-layer steel structure module and steel frame composite building structure, and analyze and study its structure, so as to improve the utilization rate of steel structure and promote the development of the construction industry.展开更多
By using real-space recursion method,the energetics of the undoped and Al and/or RE atoms doped 7（1450）〈0001〉 symmetric tilt grain boundaries（GBs）in AZ91 alloys were investigated.Similar calculations were perfor...By using real-space recursion method,the energetics of the undoped and Al and/or RE atoms doped 7（1450）〈0001〉 symmetric tilt grain boundaries（GBs）in AZ91 alloys were investigated.Similar calculations were performed on undoped and doped bulk α Mg for comparison.The results showed that Al atoms segregated at GBs in AZ91 alloys.When RE atoms were added,they also segregated at GBs,and their segregation is stronger than Al atoms＇.Therefore,RE atoms retard the segregation of Al atoms.Calculations of interaction energy indicated that Al atoms repelled each other,and could form ordered phase with host Mg atoms.On the contrary to the case of Al,RE atoms attracted each other,they could not form ordered phase with Mg,but could form clusters.Between RE and Al,there existed attractive interaction,and this attractive interaction was the origin of Al11RE3 precipitation.Precipitation of Al11RE3 particles with high melting point and high thermal stability along GB improves high temperature properties of AZ91 alloys.展开更多
Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A...Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A0.67Ln0.33 Mn0.33Ti0.6703（A = Ca or Sr and Ln = rare earth） were found to have orthorhombic symmetry with the space group Pnrna, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Cao.67Ln0.33Mn0.33Ti0.6703 for several rare earth elements showed a semiconducting property with the activation energy of 0.4 eV. Some of these compounds of the strontium system show the antiferromagnetic properties below 10 K.展开更多
The effect of rare earth metals cerium, lanthanum and yttrium on chemical composition, structure and properties of electroless Co B alloy coating was studied. By plasma transmitting spectrograph, electron energy spec...The effect of rare earth metals cerium, lanthanum and yttrium on chemical composition, structure and properties of electroless Co B alloy coating was studied. By plasma transmitting spectrograph, electron energy spectrometer, X ray diffractometter, micro hardometer and vibratory sample magnetometer the chemical constitution, structure and properties of the alloy coatings were analyzed and inspected. The results show that with a tiny quantity of rare earth metal added into Co B alloy coating, the content of boron is decreased in the alloy coatings, and the kinds of rare earth metal have enormous effect on the structure and properties of electroless Co B alloy coating. At the same time electroless Co B alloy with amorphous structure is transformed to electroless Co B RE alloy with microcrystalline or crystalline structure. In this way microhardness of the coatings is increased remarkably. Cerium and lanthanum would also increase the saturated magnetic intensity and decrease coercitive force of the coating. So soft magnetization of the coatings would be improved.展开更多
Three complexes, [Pr（NO3）3（HL）2] （1）, [Nd（NO3）3（HL）2] （2） and [Er（NO3）3（HL）2] ·0.5H2O （3）, were synthesized from the reaction of a Schiff base ligand 2-[ （4-methylphenylimino）methyl ]-6-methox...Three complexes, [Pr（NO3）3（HL）2] （1）, [Nd（NO3）3（HL）2] （2） and [Er（NO3）3（HL）2] ·0.5H2O （3）, were synthesized from the reaction of a Schiff base ligand 2-[ （4-methylphenylimino）methyl ]-6-methoxyphenol （C15 H15 NO2, HL） with Ln（NO3）3·6H2O （Ln = Pr, Nd, Er）. Characterization by single-crystal X-ray diffraction technique, elemental analysis, molar conductance, FT-IR, UV-Vis, ^1H NMR and thermal analysis shows the title complexes are neutral molecules where the central Ln（ Ⅲ） ion is ten-coordinated in biapical anti-hexahedron prism geometry, with four oxygen atoms of the phenolic hydroxy and methoxy groups in the two bidentate Schiff base ligands and six oxygen atoms provided by the three bidentate NO3 - anions. Additionally, the kinetic mechanism of thermal decomposition of complex 3 was determined with a TG-DTG curves by both integral and differential methods. The functions of thermal decomposition reaction mechanism and the equation of kinetic compensation effect were obtained.展开更多
Effects of rare earth oxides（Y2O3,La2O3,and Er2O3） on the viscosity,thermal expansion,and structure of alkali-free boro-aluminosilicate glasses were investigated by the rotating crucible viscometer,dilatometry and F...Effects of rare earth oxides（Y2O3,La2O3,and Er2O3） on the viscosity,thermal expansion,and structure of alkali-free boro-aluminosilicate glasses were investigated by the rotating crucible viscometer,dilatometry and FT-IR absorption spectra.The results showed that the melting temperature of alkali-free boroaluminosilicate glasses decreased from 1 697.55 to 1 662.59,1 674.37 and 1 640.87 ℃ with the introduction of 1 mol%La2O3,Y2O3 and Er2O3,respectively.However,the glass transition temperature Tg,dilatometric softening temperature T_d and coefficient of thermal expansion of alkali-free boro-aluminosilicate glasses increased when adding the rare-earth oxides.At high temperatures,incorporating rare earth oxides into glass resulted in the peak at about 1 085 cm^-1 towards lower wavenumber and the absorption band in the region of 850-1 260 cm^-1 broader,which indicated that rare earths acted as network modifiers and increased the numbers of non-bridging oxygen in the glass melts.However,the rare earths had an opposite effect and accumulated the glass structure at low temperatures near Tg.展开更多
Earth structures, such as roadways, embankments and slopes, and earth retaining walls, have been commonly used in cold regions for transportation and other applications. In addition to typical design considerations fo...Earth structures, such as roadways, embankments and slopes, and earth retaining walls, have been commonly used in cold regions for transportation and other applications. In addition to typical design considerations for earth structures at normal temperature, a design must also consider the unique problems associated with low temperature, such as frost heave, lateral expansion, thaw settlement and weakening, and degradation of material properties. Geosynthetics have been used in cold regions to stabilize earth structures during construction and mitigate potential problems during their service at low tem- perature. This paper provides a state of practice review of the use of geosynthetics for performance enhancement of earth structures in cold regions. This paper starts with basic information on available geosynthetic products and their functions, evaluates properties and behavior of geosynthetics and soil-geosynthetic systems at low temperature, and discusses past studies and their key results on the use of geosynthetics to enhance the performance of roadways, embankments, and earth retaining walls in cold regions. This review reveals that geosynthetics at low temperature have higher tensile strength and stiffness, lower creep rate, and lower elongation at failure. The effect of temperature becomes significant when nonwoven geotextiles are subjected to moistening and soil intrusion at subfreezing temperature. Freeze-thaw cycles may degrade hydraulic and mechanical properties of geosynthetic-soil systems. The inclusion of geosynthetics in soil provides drainage and/or barrier to water flow, retains mechanical properties, and reduces frost heave during and after freeze-thaw cycles. Effectiveness of geosynthetics has been confirmed in the field in bridging over voids, stabilizing roadways over temper- ature-susceptible soils during thaw, and proving drainage and barrier to temperature-susceptible soils before freeze. To avoid frost heave and lateral expansion of backfill in earth retaining walls, granular fill without fines should be used. When backfill with fines is used for earth retaining walls, additional lateral earth pressure induced by soil freeze and thaw set- tlement should be considered in the design.展开更多
Ferroelastic rare earth tantalates(RETaO_(4))are widely researched as the next-generation thermal barrier coatings(TBCs),and RETaO_(4)powders are hugely significant for synthesizing their coatings.The current research...Ferroelastic rare earth tantalates(RETaO_(4))are widely researched as the next-generation thermal barrier coatings(TBCs),and RETaO_(4)powders are hugely significant for synthesizing their coatings.The current research used chemical co-precipitation within an automated experimental device to synthesize RETaO_(4)(RE=Nd,Sm,Gd,Ho,Er)powders.The device automatically monitored and controlled the solutions'pH,improving the chemical co-precipitation efficiency.The crystal structure and microstructure of the RETaO_(4)powders can be controlled by changing the annealing temperature,and the materials undergo an m'-m phase transition.The m'-RETaO_(4)powders exhibit nano-size grains,while m-RETaO_(4)powders evince micron-size grains,altered by the annealing temperatures.A simultaneous thermal analysis es-timates the reversive ferroelastic tetragonal-monoclinic phase transition temperatures.Overall,this research focuses on the synthesis,crystal structures,microstructures,and phase transition of the fabricated RETaO_(4)powders.展开更多
By the method of high-temperature reactions in solid phase, compounds with the general formula MⅡ（AⅢ2/3U1/3）O3（MⅡ=Sr, AⅢ=Sc, In;MⅡ=Ba, AⅢ=Sc, In, Y, Nd-Lu） were synthesized.Their structures（space groups Fm ...By the method of high-temperature reactions in solid phase, compounds with the general formula MⅡ（AⅢ2/3U1/3）O3（MⅡ=Sr, AⅢ=Sc, In;MⅡ=Ba, AⅢ=Sc, In, Y, Nd-Lu） were synthesized.Their structures（space groups Fm 3 m and Pnma） were refined by the Rietveld method and morphotropic transition in Ba（Ln2/3U1/3）O3 on the border of Gd-Tb was discovered.By means of high-temperature X-ray diffraction, phase transitions were studied and thermal expansion coefficients were determined.展开更多
The structural, elastic and electronic properties of YAg-B2（CsCl） were investigated using the first-principles calculations. The energy band structure and the density of states were studied in detail, including part...The structural, elastic and electronic properties of YAg-B2（CsCl） were investigated using the first-principles calculations. The energy band structure and the density of states were studied in detail, including partial density of states （PDOS）, in order to identify the character of each band. The structural parameters （lattice constant, bulk modulus, pressure derivative of bulk modulus） and elastic constants were also obtained. The results were consistent with the experimental data available in the literature, as well as other theoretical results.展开更多
Recent progress in microwave absorption materials stimulates the extensive exploration of rare earth oxide materials.Herein,we report the synthesis of a hollow sphere-based carbon material compounded with rare earth o...Recent progress in microwave absorption materials stimulates the extensive exploration of rare earth oxide materials.Herein,we report the synthesis of a hollow sphere-based carbon material compounded with rare earth oxides.Hollow N-doped carbon nano-spheres loaded ceria composites(H-NC@CeO_(2))were designed and prepared by the template method,combined with in-situ coating,pyrolysis and chemical etching.By controlling the loading content of H-NC@CeO_(2)and adjusting the impedance matching of the material,the H-NC@CeO_(2)/PS(polystyrene)composite exhibited a minimum reflection loss(RL)of-50.8 dB and an effective absorption band-width(EAB)of 4.64 GHz at a filler ratio of 20wt%and a thickness of 2 mm.In accordance with measured electromagnetic parameters,simulations using the high frequency structure simulator(HFSS)software were conducted to investigate the impact of the honeycomb structure on the electromagnetic wave performance of H-NC@CeO_(2)/PS.By calculating the surface electric field and the material’s bulk loss density,the mechanism of electromagnetic loss for the honeycomb structure was elaborated.A method for structural design and man-ufacturing of broadband absorbing devices was proposed and a broadband absorber with an EAB of 11.9 GHz was prepared.This study presents an innovative approach to designing advanced electromagnetic(EM)wave absorbing materials with broad absorption band-widths.展开更多
AID zigzag polyoxometalate [（CH3）4N]1.50H3.50[Gd（GeW11O39）（H2O）2]·2.5H2O （1） was synthesized by reaction of the monova- cant polyanion [α-GeW11O39]^8- with Gd^3＋ ions in aqueous solution and characteriz...AID zigzag polyoxometalate [（CH3）4N]1.50H3.50[Gd（GeW11O39）（H2O）2]·2.5H2O （1） was synthesized by reaction of the monova- cant polyanion [α-GeW11O39]^8- with Gd^3＋ ions in aqueous solution and characterized by IR, UV spectra, ICP, and X-ray crystallography. X-ray single-crystal structural analysis indicated that the title compound crystallized in a monoclinic lattice, C2/c space group with α= 2.8201（5）, b=2.2885（3）, c=2.4033（4） nm, β=123.875 （2）°, V=12.878（4） nm3, Z=8, R1=0.0623, wR2=0.1287. The solid-state structure of the title compound displayed an infinite one-dimensional arrangement built up of [α-GeW11O39]^8- polyanions connected by Gd^Ⅲ cations.展开更多
The effect of rare earth （RE） on bainite trans- formation mechanism is not yet unified in the academia. Therefore, further studying the effect of RE on bainite transformation mechanism will have important guiding si...The effect of rare earth （RE） on bainite trans- formation mechanism is not yet unified in the academia. Therefore, further studying the effect of RE on bainite transformation mechanism will have important guiding significance for the development of bainite steels. In this paper, using differential dilatometer （DIL805A/D）, heat treatment was performed and C-curve was drawn. The effect of phase structure factor on bainite transformation under two different fractions of RE in Si-Mn-Mo bainite steels was investigated by the empirical electron theory （EET） of solids, molecules, dilatometry, and metallogra- phy. Experimental results show that RE makes Fe-C- RE segregation structural unit of Si-Mn-Mo bainite steels increase, i.e., the values of phase structure factor （na, FDC） increase, and delay bainite transformation due to the drag effect resulting from the segregation of RE ferrite island interphase and the retardation of RE to carbon diffusion in Si-Mn-Mo bainite steels. Beside this, C-curve is shifted to right and down, and microstructures of bainite ferrite and substructures are finer.展开更多
New cadmium and rare earth metal tungstates with the formula Cd0.25RE0.50 0.25WO4 （RE=Nd, Sin, Eu, Gd, D-statistical distrib- uted vacancies in cation sublattice） were synthesized by the solid-state reaction between...New cadmium and rare earth metal tungstates with the formula Cd0.25RE0.50 0.25WO4 （RE=Nd, Sin, Eu, Gd, D-statistical distrib- uted vacancies in cation sublattice） were synthesized by the solid-state reaction between CdWO4 and corresponding RE2W209. The obtained phases crystallize in the scheelite type structure. The Cd0.25RE0.5 0.25WO4 compounds were characterized by X-ray diffractometer （XRD）, （DTA-TG）, infrared （IR） and EPR methods.展开更多
Local structure and luminescent properties of lead phosphate glasses containing rare earth ions were studied. Optically active ions such as Eu^3＋, Dy^3＋, Tb^3＋ and Er^3＋ were chosen as dopants. The local structure...Local structure and luminescent properties of lead phosphate glasses containing rare earth ions were studied. Optically active ions such as Eu^3＋, Dy^3＋, Tb^3＋ and Er^3＋ were chosen as dopants. The local structure was verified using X-ray diffraction and Fourier transform inflared （FT-IR） spectroscopy. The visible luminescence bands recorded for the studied samples corresponded to ^5D0→^7Fj （J=0÷4） transitions of Eu^3＋, ^4F9/2→^6Hj/2 （J=11÷15） transitions of Dy^3＋, ^5D3→^7FJ, （J＇=1÷6） and ^5Da→^7FJ （J=3÷6） transitions of Tb^3＋, and ^4S1/2→^4I15/2 transitions of Er^3＋.展开更多
Seven new rare earth transition metal sulfates were synthesized by hydrothermal reactions under conditions slightly above the critical point of water. Their crystal structures were determined from single crystal X-ray...Seven new rare earth transition metal sulfates were synthesized by hydrothermal reactions under conditions slightly above the critical point of water. Their crystal structures were determined from single crystal X-ray data. The compositions of the new compounds can be represented by two general formulae ： REM （OH） 3 （SO4） and RE2M （OH） 3 （SO4） 2F （H2O） with RE = Gd, Tb, Dy ; M = Ni, Cu. Three different crystal structure types were found for the formula REM （OH） 3 （SO4）. The structures of the new compounds all feature infinite chains of REOn coordination polyhedra, which are connected to chains of CuO6 or NiO6 octabedra. The limited size range of the rare earth cations observed in these compounds is most likely because of interactions between the octabedral chains and the chains of REOn polyhedra. The new compounds are closely related to the known yttrium transition metal sulfates.展开更多
Two rare earth complexes of Ts-β-AlaH with the formula of [Ln2（H2O）4（Ts-β-AlaH）6]n·4nH2O （where Ln = Nd（1）, Gd（2）; Ts-β-AlaH = N-p-tolylsulfonyl-β-Alanine） have been synthesized and characterized by...Two rare earth complexes of Ts-β-AlaH with the formula of [Ln2（H2O）4（Ts-β-AlaH）6]n·4nH2O （where Ln = Nd（1）, Gd（2）; Ts-β-AlaH = N-p-tolylsulfonyl-β-Alanine） have been synthesized and characterized by elemental analysis, IR and X-ray diffraction. The results show that the two complexes are isostructural. They crystallize in a monoclinic system with P21/n space group. Crystal data for 1： a = 0.95149（19） nm, b = 1.9012（4） nm, c = 2.2863（5） nm, β= 100.37（3）°, Z= 4, De= 1.509 mg/cm^3, F（000） = 1880, R1= 0.0560, wR2= 0.1564 [I 〉 2σ（/）]; for 2： a = 0.9495（2） nm, b = 1.9037（4） nm, c = 2.2987（5） nm, β= 99.87（3）°, Z = 4, Dc= 1.541 mg/cm^3, F（000） = 1916, R1= 0.0515, wR2= 0.1566 [I〉2σ（I）]. The two complexes are one-dimensional chains and the coordination number of the Nd^3＋ or Gd^3＋ ion is nine.展开更多
基金supported by Fundamental Research Funds for the Central Universities(No.lzujbky-2024-05)Innovation Foundation of Provincial Education Department of Gansu(2024B-005)+2 种基金Scientific Department of Gansu(24CXGA083,24CXGA024,JK2024-28,JK2024-32 and 23CXJA0007)Industrial Support Plan Project of Provincial Education Department of Gansu(2025CYZC-003 and CYZC-2024-10)the Hunan Natural Science Foundation Science and Education Joint Fund Project(2022JJ60109).
文摘Transportation structures such as composite pavements and railway foundations typically consist of multi-layered media designed to withstand high bearing capacity.A theoretical understanding of load transfer mechanisms in these multi-layer composites is essential,as it offers intuitive insights into parametric influences and facilitates enhanced structural performance.This paper employs an improved transfer matrix method to address the limitations of existing theoretical approaches for analyzing multi-layer composite structures.By establishing a twodimensional composite pavement model,it investigates load transfer characteristics and validates the accuracy through finite element simulation.The proposed method offers a straightforward analytical approach for examining internal interactions between structural layers.Case studies indicate that the concrete surface layer is the main load-bearing layer for most vertical normal and shear stresses.The soil base layer reduces the overall mechanical response of the substructure,while horizontal actions increase the risk of interfacial slip and cracking.Structural optimization analysis demonstrates that increasing the thickness of the concrete surface layer,enhancing the thickness and stiffness of the soil base layer,or incorporating gradient layers can significantly mitigate these risks of interfacial slip and cracking.The findings of this study can guide the optimization design,parameter analysis,and damage prevention of multi-layer composite structures.
基金Project supported by Guizhou Provincial Basic Research Program (Natural Science)(Qian Ke He Basic-ZK 2024 General 626)National Natural Science Foundation of China (52164018)Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology (13210025)。
文摘Rare earth elements(REEs) are associated with phosphorite,which is an important strategic reserve resource.During sorting process of phosphorite,REEs may move with specific host minerals,however,occurrence state and moving pattern of REEs from rock to products are still unclear,which limits separation and enrichment of REEs from phosphorite.Mappings of scanning electron microscope(SEM) and electron probe X-ray micro-analyzer(EPMA) of REEs are highly consistent with those of calcium and phosphorus,and complementary with that of magnesium,which indicates that fluorapatite(Fap) is the main host mineral of REEs.The results of flotation and leaching experiments further indicate that REEs are enriched along with Fap from phosphorite to products.Occupied sites and occupation number of REEs were obtained by X-ray diffraction(XRD) refinement based on the Rietveld method.La,Ce,Nd,and Y can occupy both Ca1 and Ca2 sites.The ratios of La,Ce,Nd,and Y at Ca2 and Cal sites are 4.20,3.70,3.00,and 1.33,showing a decreasing trend,indicating that La,Ce,and Nd tend to occupy Ca2 sites,while Y tends to occupy Ca1 sites.X-ray absorption fine structure(XAFS) shows that REEs mainly form coordinate structures with oxygen and fluorine,which is a direct evidence that REEs replace calcium(Ⅱ) in phosphorite in an isomorphism form.Coordination structure and polyhedral configuration analysis indicate that substitution degree of La,Ce,Nd,and Y is Y> La> Ce≈Nd from easy to difficult at Cal and Ca2 sites.The research enriches the mineralization theory of REEs-bearing phosphorite and provides certain theoretical guidance for selective enrichment of REEs from phosphorite.
基金supported by National Natural Science Foundation of China(Nos.12075046 and 11775042)。
文摘A two-dimensional electromagnetic particle-in-cell simulation model is proposed to study the density evolution and collective stopping of electron beams in background plasmas.We show here the formation of the multi-layer structure of the relativistic electron beam in the plasma due to the different betatron frequency from the beam front to the beam tail.Meanwhile,the nonuniformity of the longitudinal wakefield is the essential reason for the multi-layer structure formation in beam phase space.The influences of beam parameters(beam radius and transverse density profile)on the formation of the multi-layer structure and collective stopping in background plasmas are also considered.
文摘With the continuous improvement of China's science and technology, the design method of steel structure is also more and more, how to better apply the module building design method to the related buildings, is the current issue to focus on consideration. Therefore, this paper will focus on the design method of multi-layer steel structure module and steel frame composite building structure, and analyze and study its structure, so as to improve the utilization rate of steel structure and promote the development of the construction industry.
基金Project supported by the National Natural Science Foundation of China(50671069,50571071)Science Research Plan of Liaoning Province Education Bureau(05L297)+1 种基金Postdoctor Science Foundation of China(2004036113)the Doctor Starting Project and the Experiment Center of Shenyang Normal University
文摘By using real-space recursion method,the energetics of the undoped and Al and/or RE atoms doped 7（1450）〈0001〉 symmetric tilt grain boundaries（GBs）in AZ91 alloys were investigated.Similar calculations were performed on undoped and doped bulk α Mg for comparison.The results showed that Al atoms segregated at GBs in AZ91 alloys.When RE atoms were added,they also segregated at GBs,and their segregation is stronger than Al atoms＇.Therefore,RE atoms retard the segregation of Al atoms.Calculations of interaction energy indicated that Al atoms repelled each other,and could form ordered phase with host Mg atoms.On the contrary to the case of Al,RE atoms attracted each other,they could not form ordered phase with Mg,but could form clusters.Between RE and Al,there existed attractive interaction,and this attractive interaction was the origin of Al11RE3 precipitation.Precipitation of Al11RE3 particles with high melting point and high thermal stability along GB improves high temperature properties of AZ91 alloys.
基金Foundation ite ms:Project supported bythe Grant-in-Aidfor Scientific Research (C) (18560662) bythe Japan Societyfor the Promotion of Science
文摘Several compounds of rare earth complex oxides containing manganese and titanium were synthesized in Ar, and their crystal structures were analyzed by powder X-ray diffraction data and Rietveld method. Structures of A0.67Ln0.33 Mn0.33Ti0.6703（A = Ca or Sr and Ln = rare earth） were found to have orthorhombic symmetry with the space group Pnrna, and their interatomic distances and bond angles were obtained. This space group was also derived from electron microscopic study. Electrical conductivity of Cao.67Ln0.33Mn0.33Ti0.6703 for several rare earth elements showed a semiconducting property with the activation energy of 0.4 eV. Some of these compounds of the strontium system show the antiferromagnetic properties below 10 K.
文摘The effect of rare earth metals cerium, lanthanum and yttrium on chemical composition, structure and properties of electroless Co B alloy coating was studied. By plasma transmitting spectrograph, electron energy spectrometer, X ray diffractometter, micro hardometer and vibratory sample magnetometer the chemical constitution, structure and properties of the alloy coatings were analyzed and inspected. The results show that with a tiny quantity of rare earth metal added into Co B alloy coating, the content of boron is decreased in the alloy coatings, and the kinds of rare earth metal have enormous effect on the structure and properties of electroless Co B alloy coating. At the same time electroless Co B alloy with amorphous structure is transformed to electroless Co B RE alloy with microcrystalline or crystalline structure. In this way microhardness of the coatings is increased remarkably. Cerium and lanthanum would also increase the saturated magnetic intensity and decrease coercitive force of the coating. So soft magnetization of the coatings would be improved.
文摘Three complexes, [Pr（NO3）3（HL）2] （1）, [Nd（NO3）3（HL）2] （2） and [Er（NO3）3（HL）2] ·0.5H2O （3）, were synthesized from the reaction of a Schiff base ligand 2-[ （4-methylphenylimino）methyl ]-6-methoxyphenol （C15 H15 NO2, HL） with Ln（NO3）3·6H2O （Ln = Pr, Nd, Er）. Characterization by single-crystal X-ray diffraction technique, elemental analysis, molar conductance, FT-IR, UV-Vis, ^1H NMR and thermal analysis shows the title complexes are neutral molecules where the central Ln（ Ⅲ） ion is ten-coordinated in biapical anti-hexahedron prism geometry, with four oxygen atoms of the phenolic hydroxy and methoxy groups in the two bidentate Schiff base ligands and six oxygen atoms provided by the three bidentate NO3 - anions. Additionally, the kinetic mechanism of thermal decomposition of complex 3 was determined with a TG-DTG curves by both integral and differential methods. The functions of thermal decomposition reaction mechanism and the equation of kinetic compensation effect were obtained.
基金Funded by the National Key Research and Development Program of China(No.2016YFB0303702)
文摘Effects of rare earth oxides（Y2O3,La2O3,and Er2O3） on the viscosity,thermal expansion,and structure of alkali-free boro-aluminosilicate glasses were investigated by the rotating crucible viscometer,dilatometry and FT-IR absorption spectra.The results showed that the melting temperature of alkali-free boroaluminosilicate glasses decreased from 1 697.55 to 1 662.59,1 674.37 and 1 640.87 ℃ with the introduction of 1 mol%La2O3,Y2O3 and Er2O3,respectively.However,the glass transition temperature Tg,dilatometric softening temperature T_d and coefficient of thermal expansion of alkali-free boro-aluminosilicate glasses increased when adding the rare-earth oxides.At high temperatures,incorporating rare earth oxides into glass resulted in the peak at about 1 085 cm^-1 towards lower wavenumber and the absorption band in the region of 850-1 260 cm^-1 broader,which indicated that rare earths acted as network modifiers and increased the numbers of non-bridging oxygen in the glass melts.However,the rare earths had an opposite effect and accumulated the glass structure at low temperatures near Tg.
基金provided by Prof. JianKun Liu at Beijing Jiatong University through the National Basic Research Program of China (973 Program, No. 2012CB026104) for technical exchange at Beijing Jiatong University in May 2013 and research result presentation at the 1st International Symposium on Transportation Soil Engineering in Cold Regions held in Xining, China from Oct. 10 to 11, 2013
文摘Earth structures, such as roadways, embankments and slopes, and earth retaining walls, have been commonly used in cold regions for transportation and other applications. In addition to typical design considerations for earth structures at normal temperature, a design must also consider the unique problems associated with low temperature, such as frost heave, lateral expansion, thaw settlement and weakening, and degradation of material properties. Geosynthetics have been used in cold regions to stabilize earth structures during construction and mitigate potential problems during their service at low tem- perature. This paper provides a state of practice review of the use of geosynthetics for performance enhancement of earth structures in cold regions. This paper starts with basic information on available geosynthetic products and their functions, evaluates properties and behavior of geosynthetics and soil-geosynthetic systems at low temperature, and discusses past studies and their key results on the use of geosynthetics to enhance the performance of roadways, embankments, and earth retaining walls in cold regions. This review reveals that geosynthetics at low temperature have higher tensile strength and stiffness, lower creep rate, and lower elongation at failure. The effect of temperature becomes significant when nonwoven geotextiles are subjected to moistening and soil intrusion at subfreezing temperature. Freeze-thaw cycles may degrade hydraulic and mechanical properties of geosynthetic-soil systems. The inclusion of geosynthetics in soil provides drainage and/or barrier to water flow, retains mechanical properties, and reduces frost heave during and after freeze-thaw cycles. Effectiveness of geosynthetics has been confirmed in the field in bridging over voids, stabilizing roadways over temper- ature-susceptible soils during thaw, and proving drainage and barrier to temperature-susceptible soils before freeze. To avoid frost heave and lateral expansion of backfill in earth retaining walls, granular fill without fines should be used. When backfill with fines is used for earth retaining walls, additional lateral earth pressure induced by soil freeze and thaw set- tlement should be considered in the design.
基金the Rare and Precious Metals Material Genetic Engineering Project of Yunnan Province(202102AB080019-1)National Key Research and Development Program of China(2022YFB3708600)the National Natural Science Foundation of China(91960103).
文摘Ferroelastic rare earth tantalates(RETaO_(4))are widely researched as the next-generation thermal barrier coatings(TBCs),and RETaO_(4)powders are hugely significant for synthesizing their coatings.The current research used chemical co-precipitation within an automated experimental device to synthesize RETaO_(4)(RE=Nd,Sm,Gd,Ho,Er)powders.The device automatically monitored and controlled the solutions'pH,improving the chemical co-precipitation efficiency.The crystal structure and microstructure of the RETaO_(4)powders can be controlled by changing the annealing temperature,and the materials undergo an m'-m phase transition.The m'-RETaO_(4)powders exhibit nano-size grains,while m-RETaO_(4)powders evince micron-size grains,altered by the annealing temperatures.A simultaneous thermal analysis es-timates the reversive ferroelastic tetragonal-monoclinic phase transition temperatures.Overall,this research focuses on the synthesis,crystal structures,microstructures,and phase transition of the fabricated RETaO_(4)powders.
文摘By the method of high-temperature reactions in solid phase, compounds with the general formula MⅡ（AⅢ2/3U1/3）O3（MⅡ=Sr, AⅢ=Sc, In;MⅡ=Ba, AⅢ=Sc, In, Y, Nd-Lu） were synthesized.Their structures（space groups Fm 3 m and Pnma） were refined by the Rietveld method and morphotropic transition in Ba（Ln2/3U1/3）O3 on the border of Gd-Tb was discovered.By means of high-temperature X-ray diffraction, phase transitions were studied and thermal expansion coefficients were determined.
基金supported by Gazi University Research Project Unit (05/2007/18)Hacettepe University (0701602005)
文摘The structural, elastic and electronic properties of YAg-B2（CsCl） were investigated using the first-principles calculations. The energy band structure and the density of states were studied in detail, including partial density of states （PDOS）, in order to identify the character of each band. The structural parameters （lattice constant, bulk modulus, pressure derivative of bulk modulus） and elastic constants were also obtained. The results were consistent with the experimental data available in the literature, as well as other theoretical results.
基金supported by the Research Funding of Hangzhou International Innovation Institute of Beihang Uni-versity,China(No.2024KQ130)the National Natural Science Foundation of China(Nos.52073010 and 52373259).
文摘Recent progress in microwave absorption materials stimulates the extensive exploration of rare earth oxide materials.Herein,we report the synthesis of a hollow sphere-based carbon material compounded with rare earth oxides.Hollow N-doped carbon nano-spheres loaded ceria composites(H-NC@CeO_(2))were designed and prepared by the template method,combined with in-situ coating,pyrolysis and chemical etching.By controlling the loading content of H-NC@CeO_(2)and adjusting the impedance matching of the material,the H-NC@CeO_(2)/PS(polystyrene)composite exhibited a minimum reflection loss(RL)of-50.8 dB and an effective absorption band-width(EAB)of 4.64 GHz at a filler ratio of 20wt%and a thickness of 2 mm.In accordance with measured electromagnetic parameters,simulations using the high frequency structure simulator(HFSS)software were conducted to investigate the impact of the honeycomb structure on the electromagnetic wave performance of H-NC@CeO_(2)/PS.By calculating the surface electric field and the material’s bulk loss density,the mechanism of electromagnetic loss for the honeycomb structure was elaborated.A method for structural design and man-ufacturing of broadband absorbing devices was proposed and a broadband absorber with an EAB of 11.9 GHz was prepared.This study presents an innovative approach to designing advanced electromagnetic(EM)wave absorbing materials with broad absorption band-widths.
基金supported by the National Natural Science Foundation of China (20771034,20773035)the Specialized Research Fund for the Doctoral Program of Higher Education (20040475001)+1 种基金Program for New Century Excellent Talents in University of Henan Province (2005KYCX011)the Natural Science Foundation of Henan Province (0611011900)
文摘AID zigzag polyoxometalate [（CH3）4N]1.50H3.50[Gd（GeW11O39）（H2O）2]·2.5H2O （1） was synthesized by reaction of the monova- cant polyanion [α-GeW11O39]^8- with Gd^3＋ ions in aqueous solution and characterized by IR, UV spectra, ICP, and X-ray crystallography. X-ray single-crystal structural analysis indicated that the title compound crystallized in a monoclinic lattice, C2/c space group with α= 2.8201（5）, b=2.2885（3）, c=2.4033（4） nm, β=123.875 （2）°, V=12.878（4） nm3, Z=8, R1=0.0623, wR2=0.1287. The solid-state structure of the title compound displayed an infinite one-dimensional arrangement built up of [α-GeW11O39]^8- polyanions connected by Gd^Ⅲ cations.
基金financially supported by the Technology Innovation Fund of the Ministry of Science and Technology of China(No.04C26215200858)
文摘The effect of rare earth （RE） on bainite trans- formation mechanism is not yet unified in the academia. Therefore, further studying the effect of RE on bainite transformation mechanism will have important guiding significance for the development of bainite steels. In this paper, using differential dilatometer （DIL805A/D）, heat treatment was performed and C-curve was drawn. The effect of phase structure factor on bainite transformation under two different fractions of RE in Si-Mn-Mo bainite steels was investigated by the empirical electron theory （EET） of solids, molecules, dilatometry, and metallogra- phy. Experimental results show that RE makes Fe-C- RE segregation structural unit of Si-Mn-Mo bainite steels increase, i.e., the values of phase structure factor （na, FDC） increase, and delay bainite transformation due to the drag effect resulting from the segregation of RE ferrite island interphase and the retardation of RE to carbon diffusion in Si-Mn-Mo bainite steels. Beside this, C-curve is shifted to right and down, and microstructures of bainite ferrite and substructures are finer.
文摘New cadmium and rare earth metal tungstates with the formula Cd0.25RE0.50 0.25WO4 （RE=Nd, Sin, Eu, Gd, D-statistical distrib- uted vacancies in cation sublattice） were synthesized by the solid-state reaction between CdWO4 and corresponding RE2W209. The obtained phases crystallize in the scheelite type structure. The Cd0.25RE0.5 0.25WO4 compounds were characterized by X-ray diffractometer （XRD）, （DTA-TG）, infrared （IR） and EPR methods.
基金Project supported by the Science and Higher Education (N N204 313937)
文摘Local structure and luminescent properties of lead phosphate glasses containing rare earth ions were studied. Optically active ions such as Eu^3＋, Dy^3＋, Tb^3＋ and Er^3＋ were chosen as dopants. The local structure was verified using X-ray diffraction and Fourier transform inflared （FT-IR） spectroscopy. The visible luminescence bands recorded for the studied samples corresponded to ^5D0→^7Fj （J=0÷4） transitions of Eu^3＋, ^4F9/2→^6Hj/2 （J=11÷15） transitions of Dy^3＋, ^5D3→^7FJ, （J＇=1÷6） and ^5Da→^7FJ （J=3÷6） transitions of Tb^3＋, and ^4S1/2→^4I15/2 transitions of Er^3＋.
基金Foundation ite m:Project supported by R.A.Welch Foundation
文摘Seven new rare earth transition metal sulfates were synthesized by hydrothermal reactions under conditions slightly above the critical point of water. Their crystal structures were determined from single crystal X-ray data. The compositions of the new compounds can be represented by two general formulae ： REM （OH） 3 （SO4） and RE2M （OH） 3 （SO4） 2F （H2O） with RE = Gd, Tb, Dy ; M = Ni, Cu. Three different crystal structure types were found for the formula REM （OH） 3 （SO4）. The structures of the new compounds all feature infinite chains of REOn coordination polyhedra, which are connected to chains of CuO6 or NiO6 octabedra. The limited size range of the rare earth cations observed in these compounds is most likely because of interactions between the octabedral chains and the chains of REOn polyhedra. The new compounds are closely related to the known yttrium transition metal sulfates.
基金[This work was supported by the National Natural Science Foundation of China (No. 20471026) and the Natural Science Foundation of Henan province of China (No. 0311021200).]
文摘Two rare earth complexes of Ts-β-AlaH with the formula of [Ln2（H2O）4（Ts-β-AlaH）6]n·4nH2O （where Ln = Nd（1）, Gd（2）; Ts-β-AlaH = N-p-tolylsulfonyl-β-Alanine） have been synthesized and characterized by elemental analysis, IR and X-ray diffraction. The results show that the two complexes are isostructural. They crystallize in a monoclinic system with P21/n space group. Crystal data for 1： a = 0.95149（19） nm, b = 1.9012（4） nm, c = 2.2863（5） nm, β= 100.37（3）°, Z= 4, De= 1.509 mg/cm^3, F（000） = 1880, R1= 0.0560, wR2= 0.1564 [I 〉 2σ（/）]; for 2： a = 0.9495（2） nm, b = 1.9037（4） nm, c = 2.2987（5） nm, β= 99.87（3）°, Z = 4, Dc= 1.541 mg/cm^3, F（000） = 1916, R1= 0.0515, wR2= 0.1566 [I〉2σ（I）]. The two complexes are one-dimensional chains and the coordination number of the Nd^3＋ or Gd^3＋ ion is nine.
