Electric-magnetic-force characteristics of rare earth barium copper oxide superconductor high-field coils based on screening effect and strain sensitivity

Rare earth barium copper oxide(REBCO)is the most researched and commercialized second-generation high-temperature superconducting material.Due to the anisotropic structure,strong deformation sensitivity,and central field errors caused by screening current effects,it is still a challenge for commercialization applications.In this study,the transversely isotropic constitutive relationship is selected as the mechanical model based on the structural characteristics of REBCO tapes,and suitable microelements are selected to equate the elastic constants using their average stress-strain relationships.Then,a two-dimensional axisymmetric model for coils wound by single-layer tapes is constructed to analyze the dependence of the electric-magnetic-force distribution in the tape on the strain.Finally,the anisotropic approximation of the homogenized bulk method is used to equate large-turn high-field coils,and the electric-magnetic-force distribution characteristics of the coils with/without screening effects and mechanical strain conditions are investigated,respectively.The results reveal that the mechanical strain has a weakening effect on the electromagnetic field distribution of superconducting tapes,but causes a significant enhancement in the force field distribution.In the presence of 0.5% mechanical strain,the maximum weakening of the peak value of the current density and the critical current density inside the high-field coil can reach about 8% and 13%,respectively,with a nearly 5 times increase in the peak stress.The screening current makes the current field distribution inside the coil improve by about 10 times.The screening current induced magnetic field can reach up to 0.8 T,making the relative error of the high-field coil center up to 7.8%.

Glass-forming Ability and Chemical Stability of Magneto-optical Glass Heavily Doped with Rare Earth Oxide

The glass-forming region of B2O3-Al2O3-SiO2 （BAS） glass heavily doped with rare earth oxides was investigated by an effective method, and the chemical stability was investigated by powder method. Influences of rare earth oxides on the glass-forming ability and the chemical stability of the BAS glass were also discussed. The experimental results show that the BAS glass-forming region expands firstly with the increase of the Tb2O3 content up to 30mol% and then shrinks. The acid-resistant capacity of the BAS glass doped with rare earth oxides is the lowest, the water-resistant capacity is secondary, and the alkali-resistant capacity is the best. Besides, the glass chemical stability can be improved by doping appropriate amount of rare earth oxides. Moreover, the stronger the ionic polarization ability of the rare earth ions is, the better the chemical stability of the BAS glass will be.

Magnetic Behavior of Some Rare-Earth Transition-Metal Perovskite Oxide Systems

Magnetic properties were investigated for the rare-earth 3d-transition metal oxides with the perovskite structure. Intriguing magnetic phenomena were reviewed for a few systems:magnetization peak effect in the titanates, magnetization reversal in the chromites and metallic ferromagnetism in the cobaltites. The results suggest an important role of the rare-earth ions for the magnetic properties of such complex oxides.

Quench characteristics and mechanical responses during quench propagation in rare earth barium copper oxide pancake coils

Quench and mechanical behaviors are critical issues in high temperature superconducting(HTS)coils.In this paper,the quench characteristics in the rare earth barium copper oxide(REBCO)pancake coil at 4.2K are analyzed,and a two-dimensional(2D)axisymmetric electro-magneto-thermal model is presented.The effects of the constituent materials,background field,and coil size are analyzed.An elastoplastic mechanical model is used to study the corresponding mechanical responses during the quench propagation.The variations of the temperature and strain in superconducting layers are compared.The results indicate that the radial strain evolutions can reflect the transverse quench propagation and the tensile hoop and radial stresses in superconducting layers increase with the quench propagation.The possible damages are discussed with the consideration of the effects of the background field and coil size.It is concluded that the high background field significantly increases the maximum tensile hoop and radial stresses in quenching coils and local damage may be caused.

Laser cladding in-situ carbide particle reinforced Fe-based composite coatings with rare earth oxide addition

Particulate reinforced metal matrix composite(PR-MMC) has excellent properties such as good wear resistance,corrosion resistance and high temperature properties.Laser cladding is usually used to form PR-MMC on metal surface with various volume fractions of ceramic particles.Recent literatures showed that laser melting of powder mixture containing carbon and carbide-forming elements,was favorable for the formation of in-situ synthesized carbide particles.In this paper,rare earth oxide(RE2O3) was added into t...

Rare Earth Effects on Adhesion of Cr_2O_3 Oxide Scale Formed on Surface of Co-40Cr Alloy

Isothermal and cyclic oxidation behaviors of Co 40Cr alloy at 1000 ℃ in air were studied. Scanning electron microscopy (SEM) was used to examine the oxide scale formed on the surface of the alloy. By comparing the oxidation behaviors of Co 40Cr alloy and its 3×10 16 and 3×10 17 Y +/cm 2 implanted specimens, it was found that the resistant to oxidation property of Co 40Cr was greatly improved due to the implantation of yttrium. Acoustic emission was used to study the distribution of defects at the interface between the scale and alloy. Raman spectrum was also used to study the stress status in chromic scale formed on the surface of Co 40Cr with and without yttrium. The main reason for the improvement of resistant to oxidation property of Y doped Co 40Cr probably is that yttrium can segregate to Cr 2O 3 grain boundaries and change the scale′s growing mechanism and mechanical property. Most importantly, Y implantation decreases the size and number of interfacial defects and the residual stress in the scale, and remarkably enhances the adhesion of chromia scale with Co 40Cr substrate.

Effects of rare earths on the microarc oxidation of a magnesium alloy

The effects of rare earths on the properties of the microarc oxidation（MAO） coating on a magnesium alloy were investigated by means of scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,and electrochemistry methods.The results show that a nice and compact MAO coating was successfully obtained when the magnesium alloy was treated in nitrate solutions as the pre-treatment of MAO.However,the MAO was not successfully completed for the silicate electrolytes with the addition of rare earths.After the magnesium alloy being treated by rare earth nitrate,the obtained MAO coating has advantages such as uniform distribution of thickness,improved corrosion resistance,and nice-uniform surface,as compared with the untreated magnesium alloy.In addition,the time of non-ESP,the voltage and current density of the MAO process obviously decrease.Cerium oxide doped on the surface of the magnesium alloy can significantly improve the corrosion resistance of the MAO coating and decrease the current density of the MAO process,as compared with lanthanum oxide,whereas the doped rare earths have no significant effect on the components of the MAO coating.

Preparation of Rare Earth Hydroxide and Oxide Nanoparticles by Precipitation Method

A series of rare earth hydroxide and oxide nanoparticles have been prepared by precipitation method with alcohol as the dispersive and protective reagent. Transmission electron microscope （TEM） images indicate that the particles are spherical in shape and smaller than 100 nm in size. The crystallite sizes of cubic Ln2O3 have lanthanide shrinking effect, while average crystal lattice distortion rates possess lanthanide swelling effect. The diffraction peak intensity of heavy rare earth oxide nanometer powders is remarkably stronger than that of light rare earth oxide nanometer powders. The variation of diffraction intensity with atomic number presents an inverted W type, forming a double peak structure. Fourier transform infrared （FTIR） spectrums reveal that Ln2O3 nanopowders have higher surface activity than that of ordinary Ln2O3 powders. The UV-vis spectra show that Ln-O bond of these particles is slightly blue-shifted, and its absorption intensity decreases.

Effect of mixed rare earth oxides and CaCO_3 modification on the microstructure of an in-situ Mg_2Si/Al-Si composite

The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope,scanning electron microscope,and energy dispersive spectrum analysis. The results showed that the morphol-ogy of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape,their sizes decreased from 75 μm to about 25 μm,and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth o...

Thermodynamics of Modifying Effect of Rare Earth Oxide on Inclusions in Hardfacing Metal of Medium-High Carbon Steel

The modifying effect of rare earth (RE) oxide on inclusions in hardfacing metals of medium-high carbon steel was investigated by means of thermodynamics. The thermodynamic analysis for inclusion formation shows that RE oxide can be reduced to RE element by carbon, then the RE element can react with oxygen and sulfur to form the RE oxide, RE sulfide and RE oxide-sulfide in hardfacing molten pool. The deoxidization and the desulphurization can be carried out and the liquid metal can be purified. In addition, RE oxide can also react with sulfur to form RE oxide-sulfide directly. Therefore, the harmful effect of sulfur can be decreased.

Phase Behavior and Crystal Structure of Perovskite-Type Rare Earth Complex Oxides

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.

Preparation and Characterization of Microporous Nano-Tungsten Trioxide and Its Photocatalytic Activity after Doping Rare Earth

Aqueous sols and gels of tungstic acid were prepared from Na2WO4 with protonated cation-exchange resin. Nano-tungsten oxide of a microporous lamella was synthesized by means of washing of WO3· 2H2O with distilled water under ultrasonic wave agitation and centrifuging repeatedly, and the specific surface area tended to increase gradually with washing and centrifuging. The sample of centrifuged 7 h has more than 2 times highs specific surface area and more high photocatalytic activity . The mechanisms are also discussed.

Mechanism of Cracking Resistance of Hardfacing Specimens of Steel 5CrNiMo Improved by Rare Earth Oxide

The cracking morphology of the hardfacing specimens taken from steel 5CrNiMo was observed. Meanwhile, the residual stress fields were measured and simulated. Based on experiment mentioned above, the improved structure and modified inclusion in hardfacing metal with rare earth （RE） oxide were analyzed. The results show that, the hardfacing crack is initiated from the coarse dendritic crystal grain boundary, inclusions and coarse austenite grain boundary in the HAZ and propagated by the residual stress existing in the center of the hardfacing metal and HAZ. The primary columnar grain structure can be refined by adding RE oxide in the coating of the electrode. The inclusion in the hardfacing metal can be modified as well. Meanwhile, if the martensite transformation temperature is decreased, the largest value of the residual tensile stress in the dangerous region can be reduced.

Hydrogen production from coke oven gas over LiNi/γ-Al_2O_3 catalyst modified by rare earth metal oxide in a membrane reactor

The performance of LiNi/γ-Al2O3 catalysts modified by rare earth metal oxide （La2O3 or CeO2） packed on BCFNO membrane reactor was discussed for the partial oxidation of methane （POM） in coke oven gas （COG） at 875 ℃. The NiO/γ-Al2O3 catalysts with different amounts of La2O3 and CeO2 were prepared with the same preparation method and under the same condition in order to compare the reaction performance （oxygen permeation, CH4 conversion, H2 and CO selectivity） on the membrane reactor. The results show that the oxygen permeation flux increased significantly with LiNiREOx/γ-Al2O3 （RE = La or Ce） catalysts by adding the element of rare earth especially the Ce during the POM in COG. Such as, the Li15wt%CeO29wt%NiO/γ-Al2O3 catalyst with an oxygen permeation flux of 24.71 ml·cm^-2·min^-1 and a high CH4 conversion was obtained in 875 ℃. The resulted high oxygen permeation flux may be due to the added Ce that inhibited the strong interaction between Ni and Al2O3 to form the NiAl2O4 phase. In addition, the introduction of Ce leads up to an important property of storing and releasing oxygen.

TUNGSTEN ELECTRODES CONTAINING THREE TYPES OF RARE EARTH OXIDES

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Effects of flaky rare earth oxide additives on the high temperature performance of nickel electrodes

Effects of flaky rare earth oxide additives including Er2O3,Tm2O3,and Yb2O3,Lu2O3 on high temperature and high rate discharge performance of nickel electrodes were investigated.The discharge efficiency at 0.2C reached 96% at 60 oC for electrodes with 1 at.% flaky rare earth oxides.The high rate discharge performance for electrodes with flaky rare earth oxides were improved significantly,for example,discharge efficiency at 5C improved from 50% to 70%.The results showed that the end charging potential of the ...

Study on rare earth/alkaline earth oxide-doped CeO_2 solid electrolyte

Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sintering at different temperatures. The results of X-ray diffraction and transmission electron microscopy showed that the grain size of the powders was approximately 20-30 nm, and rare earth/alkaline earth oxides were completely dissolved into ceria-based solid solution with fluorite structure. The electrical conductivities of the SmzO3-CeO2 system were measured by the ac impedance technique in air at temperatures ranging from 513-900℃. The results indicated that the ionic conductivities of Srno.2oCe0.8Ol.875 solid electrolyte increase with increasing sintering temperature, and the relationship between the conductivities and measuring temperature obeys the An＇henius equation. Then the SmzO3-CeO2 material was further doped with other rare earth/alkaline earth oxide, and the conductivities improve with the effective index.

Effect of Roasting Conditions of Rich Cerium Rare Earth Carbonate on Crystallite Morphology and Polishing Ability of Ceria-Based Rare Earth Oxide

The granule shape and crystal structure of the the ceria-based rare earth oxide which were roasted at 600～1050 ℃ for 2～6 h and then cooled in furnace, cooled out of furnace or cooled in water were studied by means of XRD and SEM. The results revealed that the rich cerium rare earth carbonate could be changed into the rare earth oxide which was a kind of sandwich made of globose granule whose diameter was between 0.5～3.0 μm after being roasted in 900 ℃ for 2 h. This kind of crystal lattice in rare earth oxide belonged to face-centered cubic lattice and its space between crystal surface {111} and {200} (viz. L111 and L200) would enlarge as the roasting temperature increasing. With increasing roasting temperature, L111 would rise straightly upward, and L200 would rise straightly upward when roasting time was 2～4 h but changed little when roasting time was 4～6 h. The glass-polishing experiments found that the polishing ability of the ceria-based rare earth oxide was the best as L111 was 43～53 nm and the L200 was 43～56 nm.

Gasoline Sensor Based on Rare Earth-Doped Indium Oxide with Low Power Consumption

Nanocrystalline indium oxide powders were prepared by microemulsion and then Y2O3 and Nd2O3 doped In2O3 were synthesized separately by impregnation and chemical co-deposition. The structure and morphology were characterized by XRD and TEM, respectively. Gas sensing properties were tested at static state. The results show that homogeneous indium oxide nanopowder with main grain size of 20 nm can be obtained from microemulsion after sintered at 600 ℃ for 1 h. Pure indium oxide gas sensor has higher sensitivity to gasoline than that to ethanol, HCHO, C6H6, NH3, C4H10, but the selectivity is not as well as sensitivity.

Simultaneous Determination of Trace Rare Earth Elements and Other Elements in High Purity Terbium Oxide (Tb_4O_7) by ICP-AES After HPLC Separation Using P507 Resin

This article describes a new method for the simultaneous determination of trace rare earth elements (REEs) and non rare earth elements (NREEs) in high purity terbium oxide by ICP-AES after HPLC separation using P507 resin. The chromatographic separation of the analytes from the matrix using dilute nitric acid as mobile phase was studied. The experimental results showed that a favorable separation of trace metals (Cu and Gd) from the matrix (Tb) can easily be achieved by elution with dilute nitric acid within 25 min. The proposed method was applied to the determination of trace metals (Ca, Cu, Mg, Mn, Ni, Si, La, Ce, Pr, Nd, Sm, Eu and Gd) in high purity terbium oxide. The detection limits (DLs) for the analytes ranged from 0.4-4.0 μg\5g -1, and the recoveries are from 78%-105%.