In this work, water-based precursor solutions suitable for dip-coating of thick La2Zr2O7 （LZO） buffer layers for coated conductors on Ni-5%W substrates with an inclusion of polymeric polyvinyl pyrrolidone were devel...In this work, water-based precursor solutions suitable for dip-coating of thick La2Zr2O7 （LZO） buffer layers for coated conductors on Ni-5%W substrates with an inclusion of polymeric polyvinyl pyrrolidone were developed. The effect of varying percentage of the polymer addition on the preparation of the deposited films with maximum crack-free thickness was investigated. This novel water-based chemical solution deposition method involving polymers in two different chelate-chemistry compositions revealed the possibility to grow single, crack-free layers with thicknesses ranging from 140 to 280 nm, with good crystallinity and epitaxial growth. The effect of increasing polymer concentrations on the morphology and the structure of the films was studied. The appropriate buffer layer action of the films in preventing Ni diffusion was studied by X-ray photoelectron spectroscopy.展开更多
YBCO high temperature coated conductors are the most promising candidate for large scale superconducting transmission cables and fault current limiters.A modified TFA-MOD method was applied to prepare YBCO layer on Ro...YBCO high temperature coated conductors are the most promising candidate for large scale superconducting transmission cables and fault current limiters.A modified TFA-MOD method was applied to prepare YBCO layer on Rolling Assisted Biaxially Textured Substrate(RABiTS)with textured Y 2 O 3/YSZ/CeO 2 buffer layers,resulting in reduced time and cost of fabrication.By using Cu naphthenate instead of Cu(TFA)2,the pyrolysis time of the YBCO precursors was reduced significantly.YBCO films with thickness of 2μm were fabricated with multiple-coating and annealed at high temperature for 2 h.X-ray diffraction analysis revealed that the films were c-axis oriented.The preliminary results of YBCO films yielded 0.2 MA/cm 2 at 77 K and self field.It is believed current carrying ability of YBCO films could be further improved by reducing the reaction rate at the interface between the buffer layer and superconducting layer.展开更多
LaMnO_(3)(LMO) cap layers with different surface roughness were prepared on epi-MgO/ion-beam-assisted deposition (IBAD) MgO/solution deposition planarized (SDP) Y<sub>2</sub>O<sub>3</sub>/Haste...LaMnO_(3)(LMO) cap layers with different surface roughness were prepared on epi-MgO/ion-beam-assisted deposition (IBAD) MgO/solution deposition planarized (SDP) Y<sub>2</sub>O<sub>3</sub>/Hastelloy tape. The effects of the surface roughness of LMO on the crystallization, texture and superconducting properties of Yba<sub>2</sub>Cu<sub>3</sub>O<sub>7?δ </sub> (YBCO) films were systematically investigated. The crystallization and epitaxial texture of resulting YBCO film are significantly improved with the surface roughness of LMO decreasing from 7.0 to 1.3nm. High-performance YBCO-coated conductors could be achieved if surface roughness of LMO cap layer is well controlled.展开更多
Two groups of coated conductor samples with different thicknesses of CeO2 cap layers deposited by pulsed laser deposition （PLD） under the same conditions have been studied. Of them, one group is of CeO2 films, which...Two groups of coated conductor samples with different thicknesses of CeO2 cap layers deposited by pulsed laser deposition （PLD） under the same conditions have been studied. Of them, one group is of CeO2 films, which are deposited on stainless steel （SS） tapes coated by IBAD-YSZ （IBAD-YSZ/SS）, and the other group is of CeO2/YSZ/Y2O3 multilayers, which are deposited on NiW substrates by PLD for the fabrication of YBCO-coated conductor through the RABiTS approach. YBCO film is then deposited on the tops of both types of buffer layers by PLD. The effects of the thickness of the CeO2 film on the texture of the CeO2 film and the critical current density （Jc） of the YBCO film are analysed. For the case of CeO2 film on IBAD-YSZ/SS, there appears a self-epitaxy effect with increasing thickness of the CeO2 film. For CeO2/YSZ/Y2O3/NiW, in which the buffer layers are deposited by PLD, there occurs no self-epitaxy effect, and the optimal thickness of CeO2 is about 50 nm. The surface morphologies of the two groups of samples are examined by SEM.展开更多
It is significant for low-cost preparation of YBa2Cu3O7-δ（YBCO） coated conductors to make clear the mechanism of orientation, copper segregation, and nucleation density in BaF2-derived YBCO crystallization. In the ...It is significant for low-cost preparation of YBa2Cu3O7-δ（YBCO） coated conductors to make clear the mechanism of orientation, copper segregation, and nucleation density in BaF2-derived YBCO crystallization. In the present work,a distinct nucleation mechanism was proposed based on a transient liquid phase induced by the size effect as well as near-equilibrium assumption. With this scheme the nucleation of YBCO prepared by metal–organic deposition（MOD） or the physical vapor deposition BaF2 process was semi-quantitatively analyzed, revealing that the direct driving force for nucleation is YBCO supersaturation in the liquid phase. The theoretical analysis on the nucleation orientation portion is evidenced by the experimental result.展开更多
MgO thin films with different textures are fabricated by the ion beam assisted （IBAD） method on the Y2O3/Al2O3 buffered C276 tape. Then a CaO2 layer is directly grown on the IBAD-MgO film by the pulsed laser deposit...MgO thin films with different textures are fabricated by the ion beam assisted （IBAD） method on the Y2O3/Al2O3 buffered C276 tape. Then a CaO2 layer is directly grown on the IBAD-MgO film by the pulsed laser deposition （PLD） method. Effects of lBAD-MgO texture, substrata temperature and thickness on the grain alignment of the CeO2 layer are investigated. Film characterization is performed by x-ray diffraction and atomic force microscopy. It is found that the orientation and texture degree of the CaO2 layer are very sensitive to the IBAD-MgO texture. By optimizing the IBAD-MgO texture, CeO2 has pure （002） orientation and excellent biaxial texture deposited in a broad substrata temperature range. In addition, the PLD-CeO2 layer has a thickness effect. Under the optimized experimental condition, the PLD-CeO2 layer has a high in-plane texture of △φ = 2.9° and a smooth surface with an rms surface roughness of less than 2nm. The critical current density Jc of a 0.4μm-thick YBCO film deposited on the CeO2 layer is 6.25 × 106 A/cm2 at 77K and a self-field.展开更多
Superconducting YBa2Cu3O7-x films were grown on the CeO2/YSZ/Y2O3 buffered rolling assisted biaxial textured Ni-5at%W substrate by MOCVD method.Self-made Y(DPM)3,Ba(DPM)2,and Cu(DPM)2 were used as the precursors.Diffe...Superconducting YBa2Cu3O7-x films were grown on the CeO2/YSZ/Y2O3 buffered rolling assisted biaxial textured Ni-5at%W substrate by MOCVD method.Self-made Y(DPM)3,Ba(DPM)2,and Cu(DPM)2 were used as the precursors.Different ratios of the precursors were applied to optimize the hetero-epitaxial structure and property of YBCO films.X-ray diffraction revealed that YBCO films had excellent in plane texture with full width at half maximum(FWHM)value of(103)=5.6°-6.5°and out-of-plane texture with FWHM of(005)=3.1°-3.7°.The superconductivity of YBCO films was measured.The relationship between the ratios of the precursors and the property of the films were discussed in detail.展开更多
CeO2 seed layer was deposited on rolling-assisted biaxially textured metal substrates by direct-current(DC)magnetron reactive sputtering.The effect of deposition temperature on epitaxial orientation of CeO2 thin films...CeO2 seed layer was deposited on rolling-assisted biaxially textured metal substrates by direct-current(DC)magnetron reactive sputtering.The effect of deposition temperature on epitaxial orientation of CeO2 thin films was examined.High quality CeO2 layers were achieved at deposition temperature from 750℃to 850℃.Subsequently yttria-stabilized zirconia(YSZ)and CeO2 films were deposited to complete the buffer layer structure via the same process.The best samples exhibited a highly biaxial texture,as indicated by FWHM(full width half maximum)values in the range of 4°-5°,and 2°-4°for in-plane and out-of-plane orientations,respectively.Secondary ion mass spectrometer analysis confirmed the effective prevention of buffer layer against Ni and W metal interdiffusion.Atomic force microscope observations revealed a smooth,dense and crack-free surface morphology,which provided themselves as the good buffer structure to the YBa2Cu3O7-δ(YBCO)coated conductors.展开更多
Single buffer layers of either Gd2Zr2O7(GZO)or La2Zr2O7(LZO)with different thickness on highly textured Ni-W tapes were compared with respective to the application of YBa2Cu3O7-δcoated conductors.The superconducting ...Single buffer layers of either Gd2Zr2O7(GZO)or La2Zr2O7(LZO)with different thickness on highly textured Ni-W tapes were compared with respective to the application of YBa2Cu3O7-δcoated conductors.The superconducting performances are improved as the buffer thickness of GZO or LZO increases up to a critical value,such as 310 and 240 nm,respectively.This suggests that a thin buffer layer is insufficient to prevent the Ni diffusion.If the buffer thickness increases further,the superconducting properties degrade,probably due to changes in the microstructure and degradation of the buffer texture.Comparing with LZO,the texture of GZO is hardly dependent on its thickness,due to smaller mismatch for its lattice with that of Ni-W.For both single buffered coated conductors,the superconducting transition temperatures are around 92 K with a transition width less than 1 K.Inductive measurement reveals that the critical current density(Jc)at 77 K in self-field,reaches 1.2 MA/cm2 and 0.77 MA/cm2 for GZO,and LZO,respectively.This implies that the single buffers of GZO and LZO are comparable to standard buffer architectures such as CeO2/YSZ/Y2O3 or CeO2/LZO,being promising for the process simplification and cost reduction.展开更多
CeO2 and Ce0.8M0.2O2-d films （M = Mn, Y, Gd, Sm, Nd and La） with （00l） preferred orientation have been prepared on biaxially textured Ni-W substrates by metal organic decomposition （MOD） method. The factors infl...CeO2 and Ce0.8M0.2O2-d films （M = Mn, Y, Gd, Sm, Nd and La） with （00l） preferred orientation have been prepared on biaxially textured Ni-W substrates by metal organic decomposition （MOD） method. The factors influencing the formation of cracks on the surface of these CeO2 and doped CeO2 films on Ni-W substrates were explored by X-ray diffraction （XRD）, scanning electron microscopy （SEM） analysis, atomic force microscopy （AFM） and differential scanning calorimetry （DSC）. The results indicate that many factors, such as the change of the ionic radii of doping cations, the transformation of crystal structure and the formation of oxygen vacancies in lattices at high annealing temperature, may be related to the formation of cracks on the surface of these films. However, the crack formation shows no dependence on the crystal lattice mismatch degree of the films with Ni-W substrates. Moreover, the suppression of surface cracks is related to the change of intrinsic elasticity of CeO2 film with doping of cations with a larger radius. SEM and AFM investigations of Ce0.8M0.2O2-d （M = Y, Gd, Sm, Nd and La） films reveal the dense, smooth and crack-free microstructure, and their lattice parameters match well with that of YBCO, illuminating that they are potentially suitable to be as buffer layer, especially as cap layer in multi-layer architecture of buffer layer for coated conductors.展开更多
High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field applications.However,owing to the weak interface strength of th...High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field applications.However,owing to the weak interface strength of the laminated composite REBCO CCs,the damage induced by the thermal mismatch stress under a combination of epoxy impregnation,cooling,and quenching can cause premature degradation of the critical current.In this study,a three-dimensional(3D)electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model(CZM)is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a quench.The temperature variation,critical current degradation of the REBCO CC,and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the literature.The delamination of the REBCO CC predicted by the numerical model is consistent with the experimental result.The numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO CC.The premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO CC.Finally,the effects of the coefficient of thermal expansion(CTE)of the epoxy resin,thickness of the substrate,and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also discussed.These results help us understand the relationship between the current-carrying degradation and damage in the HTS applications.展开更多
Several types of REBa2Cu3O7-x （REBCO, RE=Y, Ho etc.） films are prepared on single crystal substrate LaAIO3 by TFA-MOD method. The phase transformation and optimized growth conditions in the crystallization are studi...Several types of REBa2Cu3O7-x （REBCO, RE=Y, Ho etc.） films are prepared on single crystal substrate LaAIO3 by TFA-MOD method. The phase transformation and optimized growth conditions in the crystallization are studied. Compared with SmBCO and GdBCO, high quality YBCO and HoBCO films are relatively easy to produce. It is revealed that the YBCO grains can form at low temperatures such as 730 ℃ during the initial heating ramp. With a high heating rate of 20 K/min and a low oxygen pressure of 100 ppm, the optimum growth temperature is around 780℃, at which the films show a Jc value of 2.88 MMcm2. Further decrease of the heating rate may produce the highquality YBCO Film with a higher Jc of 3.65 MA/cm2. The temperature dependence of resistances in various magnetic fields up to 9 T shows that the present TFAMOD YBCO and HoBCO films have similar superonducting transition temperature and magnetotransport properties.展开更多
Although Ni-W substrate with high W content (>5at.%) substrates have been developed successfully, the quality of cube texture and grain boundary, as well as extensive applications in coated conductors should be fur...Although Ni-W substrate with high W content (>5at.%) substrates have been developed successfully, the quality of cube texture and grain boundary, as well as extensive applications in coated conductors should be further improved. In the present work, once intermediate annealing treatment (IAT) at 500°C for 2 h has been employed to optimize the deformation and recrystallization textures in Ni-7at.%W (Ni7W) substrates. As a result, competitive high cube texture content (<10°) and low angle grain boundary fraction (<10°) were realized (98.5% and 91.2%, respectively). A Gd<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> (GZO) buffer layer with strong cube texture and high-quality surface deposited successfully on the Ni7W substrate using the chemical solution deposition method, demonstrating the advanced GZO/Ni7W template is promising for coated conductors.展开更多
CeO_(2)/YSZ/CeO_(2)buffer layers were prepared on biaxial textured Ni-5at.%W substrate by direct-current magnetron reactive sputtering with the optimum process.YBCO thin films were deposited on CeO_(2)/YSZ/CeO_(2)buff...CeO_(2)/YSZ/CeO_(2)buffer layers were prepared on biaxial textured Ni-5at.%W substrate by direct-current magnetron reactive sputtering with the optimum process.YBCO thin films were deposited on CeO_(2)/YSZ/CeO_(2)buffered Ni-5at.%W substrate at temperature ranging from 500℃to 700℃by diode de sputtering.By optimizing substrate temperature,pure c-axis oriented YBCO films were obtained.The mierostruetures of CeO_(2)/YSZ/CeO_(2)buffer layers were characterized by X-ray diffraction.A smooth,dense and crack-free surface morphology was observed with scanning electron microscopy.The critical current density Jc about 0.75 MA/cm2 at 77 K was obtained.展开更多
This perspective proposes approaches for improving high temper-ature superconducting coated conductors.It considers new ways to further the enormous advances made over the past nearly 40 years.The focus is on improvin...This perspective proposes approaches for improving high temper-ature superconducting coated conductors.It considers new ways to further the enormous advances made over the past nearly 40 years.The focus is on improving the critical parameters of uniformity,perfor-mance and speed-of-production(‘ups’)through materials and process innovation.展开更多
RE‐Ba‐Cu‐O(REBCO,where RE=Y,Gd,Sm,and other rare earth elements)coated conductor(CC)tapes are promising for applications in high‐energy physics and high‐field science owing to their significant advantages such as...RE‐Ba‐Cu‐O(REBCO,where RE=Y,Gd,Sm,and other rare earth elements)coated conductor(CC)tapes are promising for applications in high‐energy physics and high‐field science owing to their significant advantages such as high critical magnetic field,high current density,and the ability to achieve superconductivity at liquid nitrogen temperatures.Nevertheless,the mechanical and superconducting performances of these CC tapes are significantly affected by interface failures,such as interfacial delamination and coating fractures,which arise from the complex interplay of mechanical stress induced by magnet processing,thermal mismatch stress during cooling,electromagnetic stress under high magnetic fields,and thermal stress during quenching.This study comprehensively reviews the interface properties and failure behavior of REBCO CC tapes.First,the research progress in characterizing the intricate interface properties of REBCO CC is systematically reviewed.Furthermore,the interface failure behavior in extreme multifield environments was analyzed and summarized.Subsequently,this study outlines optimization strategies to mitigate interface failure risks in REBCO superconducting magnet structures.Finally,we address the current challenges and future perspectives on interface issues in REBCO CC tapes.By addressing these challenges,this study offers valuable insights for advancing the development and practical implementation of superconducting technologies in diverse applications.展开更多
The field‐angle dependence of the critical current in a REBa_(2)Cu_(3)O_(7) coated conductor has been measured over a fine range of temperatures from 15 K to 80 K.The particular sample is demonstrated to have a very ...The field‐angle dependence of the critical current in a REBa_(2)Cu_(3)O_(7) coated conductor has been measured over a fine range of temperatures from 15 K to 80 K.The particular sample is demonstrated to have a very low fraction of extrinsic planar defects by its near‐isotropic critical current at 77 K.At a representative magnetic field of 3 T we are able to track the emergence of the ab‐plane peak usually associated with intrinsic pinning and quantify its evolution with temperature by fitting to a maximum‐entropy function.We are also able to observe the evolution of dip and peak features in the angle dependence of the power‐law index n with decreasing temperature and show that a dip appearing at 65 K is supplanted by a sharper positive peak from 50 K.The combination of critical current and power‐law index temperature dependences shows the onset of intrinsic pinning at 50 K.展开更多
High‐temperature superconducting(HTS)AC electrical devices generally carry AC transport currents and are exposed to AC external magnetic fields with arbitrary orientations.Realistic HTS coated conductors(CCs)show div...High‐temperature superconducting(HTS)AC electrical devices generally carry AC transport currents and are exposed to AC external magnetic fields with arbitrary orientations.Realistic HTS coated conductors(CCs)show diverse critical current anisotropy and field dependence(I_(c)(B,θ),which directly affect the superconducting behavior.However,under complex electromagnetic(EM)conditions,the discrepancies in AC loss characteristics caused by different(I_(c)(B,θ),features are still unclear.Moreover,the selection of CCs with desirable(I_(c)(B,θ),features to further reduce AC loss under various EM conditions remains overlooked.In this work,the transport AC loss(Q_(t))(without field),magnetization loss(Q_(m)),and total AC loss(Q_(tot))of the nearly isotropic Shanghai Creative(SCST)CC and the strongly anisotropic Fujikura(FYSC)CC,along with their stacks,are investigated in the range of 90°and 90°(parallel to the CC wide surface)field angles based on the H‐formulation.The results show that,due to the opposite angular dependence of I_(c),the effective penetration fields of these two CCs or stacks exhibit distinct trends with the field angle,and the Q_(m)in the nearly isotropic CC is less dominated by the perpendicular field component compared to that in the strongly anisotropic CC.Furthermore,due to the different field dependence of Ic at various field angles,the two CCs or stacks exhibit opposite flux flow loss behaviors with the field angle.Overall,the SCST CC and its stack show lower Q_(tot)within the angle range around 0°,and this range expands as the external field increases,while the FYSC CC and its stack show lower Q_(tot)at the remaining angles.This is further explained by analyzing the field distribution and Q_(tot)of each tape in the stacks.This paper clarifies the discrepancies in AC loss caused by different(I_(c)(B,θ),and identifies the applicable EM conditions for different REBCO materials to reduce AC loss,providing valuable references for material selection to minimize loss in HTS AC devices across different scenarios.展开更多
Manipulating the directional movement of liquid droplets is of significance for design and fabrication of some microfluidic devices, An energy-based method is adopted to analyse the directional movement of a droplet d...Manipulating the directional movement of liquid droplets is of significance for design and fabrication of some microfluidic devices, An energy-based method is adopted to analyse the directional movement of a droplet deposited in a conical tube or on a conical fibre. We perform an experiment to investigate the directional motion of a droplet in an open conical tube. Our theoretical analysis and experimental observations both demonstrate that surface tension can drive the droplet to move in the conical tube. The critical condition of the liquid moving in the conical tube is presented. We also analyse a droplet on a conical hydrophilic fibre, which can move from the thinner to the thicker end.展开更多
A 2 1/2-dimensional electromagnetic particle-in-cell （PIC） simulation code is used to investigate electron behaviour in collisionless magnetic reconnectfon. The results show that the ion/electron mass ratio （mi/me...A 2 1/2-dimensional electromagnetic particle-in-cell （PIC） simulation code is used to investigate electron behaviour in collisionless magnetic reconnectfon. The results show that the ion/electron mass ratio （mi/me） almost has no impact on the reconnection rate, however it can significantly affect electron behaviour in the diffusion region. For the case with larger mass ratio, the width of electron current sheet becomes smaller and the outflow region along the separatrix is smaller, hence the peak of the electron outflow speed is essentially larger. Density cavities and the parallel electric field E// along the separatrix can be found in the case with larger mass ratio, which may have significant influences on the acceleration and heating of the electrons near the X point.展开更多
基金funding under the project grants P2/00/03 (CHEMAT)IAP/VI-17(INANOMAT) and FP7-NMP-2007- SMALL-1 Grant No.205854(EFECTS)
文摘In this work, water-based precursor solutions suitable for dip-coating of thick La2Zr2O7 （LZO） buffer layers for coated conductors on Ni-5%W substrates with an inclusion of polymeric polyvinyl pyrrolidone were developed. The effect of varying percentage of the polymer addition on the preparation of the deposited films with maximum crack-free thickness was investigated. This novel water-based chemical solution deposition method involving polymers in two different chelate-chemistry compositions revealed the possibility to grow single, crack-free layers with thicknesses ranging from 140 to 280 nm, with good crystallinity and epitaxial growth. The effect of increasing polymer concentrations on the morphology and the structure of the films was studied. The appropriate buffer layer action of the films in preventing Ni diffusion was studied by X-ray photoelectron spectroscopy.
基金National Science Foundation of China(51002024)"863"High-Tech Project(2007AA03Z201)
文摘YBCO high temperature coated conductors are the most promising candidate for large scale superconducting transmission cables and fault current limiters.A modified TFA-MOD method was applied to prepare YBCO layer on Rolling Assisted Biaxially Textured Substrate(RABiTS)with textured Y 2 O 3/YSZ/CeO 2 buffer layers,resulting in reduced time and cost of fabrication.By using Cu naphthenate instead of Cu(TFA)2,the pyrolysis time of the YBCO precursors was reduced significantly.YBCO films with thickness of 2μm were fabricated with multiple-coating and annealed at high temperature for 2 h.X-ray diffraction analysis revealed that the films were c-axis oriented.The preliminary results of YBCO films yielded 0.2 MA/cm 2 at 77 K and self field.It is believed current carrying ability of YBCO films could be further improved by reducing the reaction rate at the interface between the buffer layer and superconducting layer.
基金financially supported by the National Science Foundation of China(No.91421110)the National High Technology Research and Development Program of China(No.2014AA032702)+2 种基金the National Basic Research Program of China(No.2015CB358600)Sichuan Youth Science and Technology Innovation Research Team Fund(No.2011JTD0006)Sichuan Provincial Fund for Distinguished Young Academic and Technology Leaders(No.2014JQ0011)
文摘LaMnO_(3)(LMO) cap layers with different surface roughness were prepared on epi-MgO/ion-beam-assisted deposition (IBAD) MgO/solution deposition planarized (SDP) Y<sub>2</sub>O<sub>3</sub>/Hastelloy tape. The effects of the surface roughness of LMO on the crystallization, texture and superconducting properties of Yba<sub>2</sub>Cu<sub>3</sub>O<sub>7?δ </sub> (YBCO) films were systematically investigated. The crystallization and epitaxial texture of resulting YBCO film are significantly improved with the surface roughness of LMO decreasing from 7.0 to 1.3nm. High-performance YBCO-coated conductors could be achieved if surface roughness of LMO cap layer is well controlled.
文摘Two groups of coated conductor samples with different thicknesses of CeO2 cap layers deposited by pulsed laser deposition （PLD） under the same conditions have been studied. Of them, one group is of CeO2 films, which are deposited on stainless steel （SS） tapes coated by IBAD-YSZ （IBAD-YSZ/SS）, and the other group is of CeO2/YSZ/Y2O3 multilayers, which are deposited on NiW substrates by PLD for the fabrication of YBCO-coated conductor through the RABiTS approach. YBCO film is then deposited on the tops of both types of buffer layers by PLD. The effects of the thickness of the CeO2 film on the texture of the CeO2 film and the critical current density （Jc） of the YBCO film are analysed. For the case of CeO2 film on IBAD-YSZ/SS, there appears a self-epitaxy effect with increasing thickness of the CeO2 film. For CeO2/YSZ/Y2O3/NiW, in which the buffer layers are deposited by PLD, there occurs no self-epitaxy effect, and the optimal thickness of CeO2 is about 50 nm. The surface morphologies of the two groups of samples are examined by SEM.
基金Project supported by the Science and Technology Commission of Shanghai Municipality,China(Grant Nos.13111102300 and 11dz1100302)the National Natural Science Foundation of China(Grant Nos.11174193 and 51202141)+1 种基金the National Basic Research Program of China(Grant Nos.2011CBA00105)the Science and Technology Commission of Shanghai Municipality,China(Grant No.14DZ2260700)
文摘It is significant for low-cost preparation of YBa2Cu3O7-δ（YBCO） coated conductors to make clear the mechanism of orientation, copper segregation, and nucleation density in BaF2-derived YBCO crystallization. In the present work,a distinct nucleation mechanism was proposed based on a transient liquid phase induced by the size effect as well as near-equilibrium assumption. With this scheme the nucleation of YBCO prepared by metal–organic deposition（MOD） or the physical vapor deposition BaF2 process was semi-quantitatively analyzed, revealing that the direct driving force for nucleation is YBCO supersaturation in the liquid phase. The theoretical analysis on the nucleation orientation portion is evidenced by the experimental result.
基金Supported by the ITER Project of the Ministry of Science and Technology of China under Grant No 2011GB113004the Shanghai Commission of Science and Technology under Grant Nos 09DZ1206000 and 11DZ1100402the Youth Fund of Natural Science Foundation of China under Grant No 11204174
文摘MgO thin films with different textures are fabricated by the ion beam assisted （IBAD） method on the Y2O3/Al2O3 buffered C276 tape. Then a CaO2 layer is directly grown on the IBAD-MgO film by the pulsed laser deposition （PLD） method. Effects of lBAD-MgO texture, substrata temperature and thickness on the grain alignment of the CeO2 layer are investigated. Film characterization is performed by x-ray diffraction and atomic force microscopy. It is found that the orientation and texture degree of the CaO2 layer are very sensitive to the IBAD-MgO texture. By optimizing the IBAD-MgO texture, CeO2 has pure （002） orientation and excellent biaxial texture deposited in a broad substrata temperature range. In addition, the PLD-CeO2 layer has a thickness effect. Under the optimized experimental condition, the PLD-CeO2 layer has a high in-plane texture of △φ = 2.9° and a smooth surface with an rms surface roughness of less than 2nm. The critical current density Jc of a 0.4μm-thick YBCO film deposited on the CeO2 layer is 6.25 × 106 A/cm2 at 77K and a self-field.
文摘Superconducting YBa2Cu3O7-x films were grown on the CeO2/YSZ/Y2O3 buffered rolling assisted biaxial textured Ni-5at%W substrate by MOCVD method.Self-made Y(DPM)3,Ba(DPM)2,and Cu(DPM)2 were used as the precursors.Different ratios of the precursors were applied to optimize the hetero-epitaxial structure and property of YBCO films.X-ray diffraction revealed that YBCO films had excellent in plane texture with full width at half maximum(FWHM)value of(103)=5.6°-6.5°and out-of-plane texture with FWHM of(005)=3.1°-3.7°.The superconductivity of YBCO films was measured.The relationship between the ratios of the precursors and the property of the films were discussed in detail.
文摘CeO2 seed layer was deposited on rolling-assisted biaxially textured metal substrates by direct-current(DC)magnetron reactive sputtering.The effect of deposition temperature on epitaxial orientation of CeO2 thin films was examined.High quality CeO2 layers were achieved at deposition temperature from 750℃to 850℃.Subsequently yttria-stabilized zirconia(YSZ)and CeO2 films were deposited to complete the buffer layer structure via the same process.The best samples exhibited a highly biaxial texture,as indicated by FWHM(full width half maximum)values in the range of 4°-5°,and 2°-4°for in-plane and out-of-plane orientations,respectively.Secondary ion mass spectrometer analysis confirmed the effective prevention of buffer layer against Ni and W metal interdiffusion.Atomic force microscope observations revealed a smooth,dense and crack-free surface morphology,which provided themselves as the good buffer structure to the YBa2Cu3O7-δ(YBCO)coated conductors.
基金National Natural Science Foundation of China(50702033 and 10774098)Ministry of Science and Technology of China("863"Projects,.2009AA03Z204)+3 种基金Science and Technology Commission of Shanghai Municipality(08521101502)Innovation Funds for Ph.D.Graduates of Shanghai University(SHUCX101022)Shanghai Leading Academic Discipline Project(S30105)Project Based Personnel Exchange Programme with China and Germany(PPP)([2006]3139)
文摘Single buffer layers of either Gd2Zr2O7(GZO)or La2Zr2O7(LZO)with different thickness on highly textured Ni-W tapes were compared with respective to the application of YBa2Cu3O7-δcoated conductors.The superconducting performances are improved as the buffer thickness of GZO or LZO increases up to a critical value,such as 310 and 240 nm,respectively.This suggests that a thin buffer layer is insufficient to prevent the Ni diffusion.If the buffer thickness increases further,the superconducting properties degrade,probably due to changes in the microstructure and degradation of the buffer texture.Comparing with LZO,the texture of GZO is hardly dependent on its thickness,due to smaller mismatch for its lattice with that of Ni-W.For both single buffered coated conductors,the superconducting transition temperatures are around 92 K with a transition width less than 1 K.Inductive measurement reveals that the critical current density(Jc)at 77 K in self-field,reaches 1.2 MA/cm2 and 0.77 MA/cm2 for GZO,and LZO,respectively.This implies that the single buffers of GZO and LZO are comparable to standard buffer architectures such as CeO2/YSZ/Y2O3 or CeO2/LZO,being promising for the process simplification and cost reduction.
基金Funded by the National Natural Science Foundation of ChinaNational 863 Program of China(Nos.50872115and2009AA03Z203)
文摘CeO2 and Ce0.8M0.2O2-d films （M = Mn, Y, Gd, Sm, Nd and La） with （00l） preferred orientation have been prepared on biaxially textured Ni-W substrates by metal organic decomposition （MOD） method. The factors influencing the formation of cracks on the surface of these CeO2 and doped CeO2 films on Ni-W substrates were explored by X-ray diffraction （XRD）, scanning electron microscopy （SEM） analysis, atomic force microscopy （AFM） and differential scanning calorimetry （DSC）. The results indicate that many factors, such as the change of the ionic radii of doping cations, the transformation of crystal structure and the formation of oxygen vacancies in lattices at high annealing temperature, may be related to the formation of cracks on the surface of these films. However, the crack formation shows no dependence on the crystal lattice mismatch degree of the films with Ni-W substrates. Moreover, the suppression of surface cracks is related to the change of intrinsic elasticity of CeO2 film with doping of cations with a larger radius. SEM and AFM investigations of Ce0.8M0.2O2-d （M = Y, Gd, Sm, Nd and La） films reveal the dense, smooth and crack-free microstructure, and their lattice parameters match well with that of YBCO, illuminating that they are potentially suitable to be as buffer layer, especially as cap layer in multi-layer architecture of buffer layer for coated conductors.
基金Project supported by the National Natural Science Foundation of China(Nos.12302278,U2241267,12172155,and 11932008)the Fundamental Research Funds for the Central Universities of China(No.lzujbky-2022-48)the Natural Science Foundation of Gansu Province of China(No.24JRRA473)。
文摘High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field applications.However,owing to the weak interface strength of the laminated composite REBCO CCs,the damage induced by the thermal mismatch stress under a combination of epoxy impregnation,cooling,and quenching can cause premature degradation of the critical current.In this study,a three-dimensional(3D)electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model(CZM)is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a quench.The temperature variation,critical current degradation of the REBCO CC,and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the literature.The delamination of the REBCO CC predicted by the numerical model is consistent with the experimental result.The numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO CC.The premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO CC.Finally,the effects of the coefficient of thermal expansion(CTE)of the epoxy resin,thickness of the substrate,and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also discussed.These results help us understand the relationship between the current-carrying degradation and damage in the HTS applications.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 50672057, 50702033 and 10774098the National Science Foundation of China (973 Projects) under Grant No. 2006CB601005+1 种基金the Science and Technology Commission of Shanghai Municipality under Grant No. 0752nm017the Project Based Personnel Exchange Program between China and Germany under Grant No. [2006] 3139.
文摘Several types of REBa2Cu3O7-x （REBCO, RE=Y, Ho etc.） films are prepared on single crystal substrate LaAIO3 by TFA-MOD method. The phase transformation and optimized growth conditions in the crystallization are studied. Compared with SmBCO and GdBCO, high quality YBCO and HoBCO films are relatively easy to produce. It is revealed that the YBCO grains can form at low temperatures such as 730 ℃ during the initial heating ramp. With a high heating rate of 20 K/min and a low oxygen pressure of 100 ppm, the optimum growth temperature is around 780℃, at which the films show a Jc value of 2.88 MMcm2. Further decrease of the heating rate may produce the highquality YBCO Film with a higher Jc of 3.65 MA/cm2. The temperature dependence of resistances in various magnetic fields up to 9 T shows that the present TFAMOD YBCO and HoBCO films have similar superonducting transition temperature and magnetotransport properties.
文摘Although Ni-W substrate with high W content (>5at.%) substrates have been developed successfully, the quality of cube texture and grain boundary, as well as extensive applications in coated conductors should be further improved. In the present work, once intermediate annealing treatment (IAT) at 500°C for 2 h has been employed to optimize the deformation and recrystallization textures in Ni-7at.%W (Ni7W) substrates. As a result, competitive high cube texture content (<10°) and low angle grain boundary fraction (<10°) were realized (98.5% and 91.2%, respectively). A Gd<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> (GZO) buffer layer with strong cube texture and high-quality surface deposited successfully on the Ni7W substrate using the chemical solution deposition method, demonstrating the advanced GZO/Ni7W template is promising for coated conductors.
文摘CeO_(2)/YSZ/CeO_(2)buffer layers were prepared on biaxial textured Ni-5at.%W substrate by direct-current magnetron reactive sputtering with the optimum process.YBCO thin films were deposited on CeO_(2)/YSZ/CeO_(2)buffered Ni-5at.%W substrate at temperature ranging from 500℃to 700℃by diode de sputtering.By optimizing substrate temperature,pure c-axis oriented YBCO films were obtained.The mierostruetures of CeO_(2)/YSZ/CeO_(2)buffer layers were characterized by X-ray diffraction.A smooth,dense and crack-free surface morphology was observed with scanning electron microscopy.The critical current density Jc about 0.75 MA/cm2 at 77 K was obtained.
基金the Royal Academy of Engineering,United Kingdom,CIET1819_24the Ministry of Trade,Industry,and Energy(MOTIE)Korea,under the Global Industrial Technology Coop-eration Center(GITCC)program supervised by the Korea Institute for Advancement of Technology(KIAT),project number P0028377).
文摘This perspective proposes approaches for improving high temper-ature superconducting coated conductors.It considers new ways to further the enormous advances made over the past nearly 40 years.The focus is on improving the critical parameters of uniformity,perfor-mance and speed-of-production(‘ups’)through materials and process innovation.
基金supported by the National Natural Science Foundation of China(12272156 and 11932008)Shanghai Superconductor Technology Co.,Ltd–Lanzhou University Superconducting Materials and Mechanics Open Foundation for Industry-University-Research.
文摘RE‐Ba‐Cu‐O(REBCO,where RE=Y,Gd,Sm,and other rare earth elements)coated conductor(CC)tapes are promising for applications in high‐energy physics and high‐field science owing to their significant advantages such as high critical magnetic field,high current density,and the ability to achieve superconductivity at liquid nitrogen temperatures.Nevertheless,the mechanical and superconducting performances of these CC tapes are significantly affected by interface failures,such as interfacial delamination and coating fractures,which arise from the complex interplay of mechanical stress induced by magnet processing,thermal mismatch stress during cooling,electromagnetic stress under high magnetic fields,and thermal stress during quenching.This study comprehensively reviews the interface properties and failure behavior of REBCO CC tapes.First,the research progress in characterizing the intricate interface properties of REBCO CC is systematically reviewed.Furthermore,the interface failure behavior in extreme multifield environments was analyzed and summarized.Subsequently,this study outlines optimization strategies to mitigate interface failure risks in REBCO superconducting magnet structures.Finally,we address the current challenges and future perspectives on interface issues in REBCO CC tapes.By addressing these challenges,this study offers valuable insights for advancing the development and practical implementation of superconducting technologies in diverse applications.
基金supported by the Royal Society of New Zealand under Marsden Fund Grant VUW1805.
文摘The field‐angle dependence of the critical current in a REBa_(2)Cu_(3)O_(7) coated conductor has been measured over a fine range of temperatures from 15 K to 80 K.The particular sample is demonstrated to have a very low fraction of extrinsic planar defects by its near‐isotropic critical current at 77 K.At a representative magnetic field of 3 T we are able to track the emergence of the ab‐plane peak usually associated with intrinsic pinning and quantify its evolution with temperature by fitting to a maximum‐entropy function.We are also able to observe the evolution of dip and peak features in the angle dependence of the power‐law index n with decreasing temperature and show that a dip appearing at 65 K is supplanted by a sharper positive peak from 50 K.The combination of critical current and power‐law index temperature dependences shows the onset of intrinsic pinning at 50 K.
基金supported by National Natural Science Foundation of China(Grant Nos.52172271,12374378,52307026)the National Key R&D Program of China(Grant No.2022YFE03150200)Shanghai Science and Technology Innovation Program(Grant Nos.22511100200,23511101600).
文摘High‐temperature superconducting(HTS)AC electrical devices generally carry AC transport currents and are exposed to AC external magnetic fields with arbitrary orientations.Realistic HTS coated conductors(CCs)show diverse critical current anisotropy and field dependence(I_(c)(B,θ),which directly affect the superconducting behavior.However,under complex electromagnetic(EM)conditions,the discrepancies in AC loss characteristics caused by different(I_(c)(B,θ),features are still unclear.Moreover,the selection of CCs with desirable(I_(c)(B,θ),features to further reduce AC loss under various EM conditions remains overlooked.In this work,the transport AC loss(Q_(t))(without field),magnetization loss(Q_(m)),and total AC loss(Q_(tot))of the nearly isotropic Shanghai Creative(SCST)CC and the strongly anisotropic Fujikura(FYSC)CC,along with their stacks,are investigated in the range of 90°and 90°(parallel to the CC wide surface)field angles based on the H‐formulation.The results show that,due to the opposite angular dependence of I_(c),the effective penetration fields of these two CCs or stacks exhibit distinct trends with the field angle,and the Q_(m)in the nearly isotropic CC is less dominated by the perpendicular field component compared to that in the strongly anisotropic CC.Furthermore,due to the different field dependence of Ic at various field angles,the two CCs or stacks exhibit opposite flux flow loss behaviors with the field angle.Overall,the SCST CC and its stack show lower Q_(tot)within the angle range around 0°,and this range expands as the external field increases,while the FYSC CC and its stack show lower Q_(tot)at the remaining angles.This is further explained by analyzing the field distribution and Q_(tot)of each tape in the stacks.This paper clarifies the discrepancies in AC loss caused by different(I_(c)(B,θ),and identifies the applicable EM conditions for different REBCO materials to reduce AC loss,providing valuable references for material selection to minimize loss in HTS AC devices across different scenarios.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10732050, 10525210 and 10121202
文摘Manipulating the directional movement of liquid droplets is of significance for design and fabrication of some microfluidic devices, An energy-based method is adopted to analyse the directional movement of a droplet deposited in a conical tube or on a conical fibre. We perform an experiment to investigate the directional motion of a droplet in an open conical tube. Our theoretical analysis and experimental observations both demonstrate that surface tension can drive the droplet to move in the conical tube. The critical condition of the liquid moving in the conical tube is presented. We also analyse a droplet on a conical hydrophilic fibre, which can move from the thinner to the thicker end.
基金Supported by the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KZCX3-SW-144, the National Science Foundation of China under Grant Nos 60608015, and the Doctoral Fund of Qingdao University of Science and Technology.
文摘A 2 1/2-dimensional electromagnetic particle-in-cell （PIC） simulation code is used to investigate electron behaviour in collisionless magnetic reconnectfon. The results show that the ion/electron mass ratio （mi/me） almost has no impact on the reconnection rate, however it can significantly affect electron behaviour in the diffusion region. For the case with larger mass ratio, the width of electron current sheet becomes smaller and the outflow region along the separatrix is smaller, hence the peak of the electron outflow speed is essentially larger. Density cavities and the parallel electric field E// along the separatrix can be found in the case with larger mass ratio, which may have significant influences on the acceleration and heating of the electrons near the X point.
