CeO2 film plays an essential role in nucleation and growth of YBa2 Cu3 O（7-x）（YBCO） films. In this work,the dependence of superconducting properties of YBCO on CeO2 films with different thicknesses was investigate...CeO2 film plays an essential role in nucleation and growth of YBa2 Cu3 O（7-x）（YBCO） films. In this work,the dependence of superconducting properties of YBCO on CeO2 films with different thicknesses was investigated,in order to achieve fabrication of high-performance YBCO coated conductors in industrial scale. The crystalline structure and morphology of CeO2 films with thickness ranging from 21 to 563 nm were systematically characterized by means of X-ray diffraction（XRD）, atomic force microscope（AFM） and reflection high-energy electron diffraction（RHEED）. Additional focus was addressed on evolution of the surface quality of CeO2 films with thickness increasing. The results show that at the optimal thickness of 221 nm, CeO2 film exhibits sharp in-plane and out-of-plane texture with full width of half maximum（FWHM） values of 5.9° and 1.8°, respectively, and smooth surface with a mean root-mean-square（RMS） roughness value as low as 0.6 nm. Combing RHEED and transmission electron microscope（TEM） cross-sectional analysis, it is found that nucleation and growth of CeO2 films at early stage remain in island growth mode with rougher surface,while further increasing the thickness beyond the optimal thickness leads to weak surface quality, consequently resulting in degradation of superconductor layers deposited subsequently. Eventually, a critical current density（Jc） as high as 4.6×10-6 A·cm-（-2）（77 K, self-field） is achieved on a YBCO film on a thickness-modulated CeO2/MgO/Y2 O3/Al2 O3/C276 architecture, demonstrating the advantages of CeO2 films as buffer layer in high-throughput manufacture of coated conductors.展开更多
Broadband absorbers based on resonant acoustic metamaterials often require intricate designs,yet this complexity inherently restricts their bandwidth,robustness,and manufacturability.To overcome these constraints,we p...Broadband absorbers based on resonant acoustic metamaterials often require intricate designs,yet this complexity inherently restricts their bandwidth,robustness,and manufacturability.To overcome these constraints,we present a composite sound-absorbing metamaterial that combines multiple resonance coupling with quality factor modulation,leveraging micro-perforated plates and porous materials.This metamaterial exhibits near-perfect broadband sound absorption across a frequency range spanning from 340 to 3200Hz.In addition,composite metamaterials exhibit greater robustness compared to resonant metamaterials,demonstrating better noise control capabilities in diffuse sound fields.This work uses a new mechanism to revitalize traditional sound-absorbing materials and bring them back to prominence in noise control.We anticipate that this innovative solution will address noise control challenges in demanding environments and provide a reference for further development of soundabsorbing metamaterials.展开更多
基金financially supported by the International Thermonuclear Experimental Reactor (ITER) Project from Ministry of Science and Technology of China (No.2011GB113004)the National High Technology Research and Development Program of China(No.2014AA032402)+1 种基金the Shanghai Commission of Science and Technology (Nos.11DZ1100402 and 13DZ0500100)the Natural Science Foundation of China(Nos.11204174 and 51372150)
文摘CeO2 film plays an essential role in nucleation and growth of YBa2 Cu3 O（7-x）（YBCO） films. In this work,the dependence of superconducting properties of YBCO on CeO2 films with different thicknesses was investigated,in order to achieve fabrication of high-performance YBCO coated conductors in industrial scale. The crystalline structure and morphology of CeO2 films with thickness ranging from 21 to 563 nm were systematically characterized by means of X-ray diffraction（XRD）, atomic force microscope（AFM） and reflection high-energy electron diffraction（RHEED）. Additional focus was addressed on evolution of the surface quality of CeO2 films with thickness increasing. The results show that at the optimal thickness of 221 nm, CeO2 film exhibits sharp in-plane and out-of-plane texture with full width of half maximum（FWHM） values of 5.9° and 1.8°, respectively, and smooth surface with a mean root-mean-square（RMS） roughness value as low as 0.6 nm. Combing RHEED and transmission electron microscope（TEM） cross-sectional analysis, it is found that nucleation and growth of CeO2 films at early stage remain in island growth mode with rougher surface,while further increasing the thickness beyond the optimal thickness leads to weak surface quality, consequently resulting in degradation of superconductor layers deposited subsequently. Eventually, a critical current density（Jc） as high as 4.6×10-6 A·cm-（-2）（77 K, self-field） is achieved on a YBCO film on a thickness-modulated CeO2/MgO/Y2 O3/Al2 O3/C276 architecture, demonstrating the advantages of CeO2 films as buffer layer in high-throughput manufacture of coated conductors.
基金supported by the Local Science and Technology Development Fund Project(Grant No.YDZX20233100004002)the Shanghai 3-year Action Plan(No.GWVI11.1-37)+1 种基金the Shanghai Pilot Program for Basic Research,the National Natural Science Foundation of China(NSFC)(Grant Nos.12404508,12404509,and 124B2087)the Xiaomi Young Talents Program.
文摘Broadband absorbers based on resonant acoustic metamaterials often require intricate designs,yet this complexity inherently restricts their bandwidth,robustness,and manufacturability.To overcome these constraints,we present a composite sound-absorbing metamaterial that combines multiple resonance coupling with quality factor modulation,leveraging micro-perforated plates and porous materials.This metamaterial exhibits near-perfect broadband sound absorption across a frequency range spanning from 340 to 3200Hz.In addition,composite metamaterials exhibit greater robustness compared to resonant metamaterials,demonstrating better noise control capabilities in diffuse sound fields.This work uses a new mechanism to revitalize traditional sound-absorbing materials and bring them back to prominence in noise control.We anticipate that this innovative solution will address noise control challenges in demanding environments and provide a reference for further development of soundabsorbing metamaterials.
