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A review on the understanding and fabrication advancement of MgB2 thin and thick films by HPCVD
Mahipal Ranot,P. V. Duong,A. Bhardwaj,강원남 한국초전도.저온공학회 2015 한국초전도저온공학회논문지 Vol.17 No.2
MgB2 thin films with superior superconducting properties are very promising for superconducting magnets, electronic devicesand coated conductor electric power applications. A clear understanding of flux pinning mechanism in MgB2 films could be a bigaid in improving the performance of MgB2 by the enhancement of Jc. The fabrication advancement and the understanding of fluxpinning mechanism of MgB2 thin and thick films fabricated by using hybrid physical-chemical vapor deposition (HPCVD) arereviewed. The distinct kind of MgB2 films, such as single-crystal like MgB2 thin films, MgB2 epitaxial columnar thick films, anda-axis-oriented MgB2 films are included for flux pinning mechanism investigation. Various attempts made by researchers toimprove further the flux pinning property and Jc performance by means of doping in MgB2 thin films by using HPCVD are alsosummarized.
Ranot, Mahipal,Duong, P.V.,Bhardwaj, A.,Kang, W.N. The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.2
$MgB_2$ thin films with superior superconducting properties are very promising for superconducting magnets, electronic devices and coated conductor electric power applications. A clear understanding of flux pinning mechanism in $MgB_2$ films could be a big aid in improving the performance of $MgB_2$ by the enhancement of $J_c$. The fabrication advancement and the understanding of flux pinning mechanism of $MgB_2$ thin and thick films fabricated by using hybrid physical-chemical vapor deposition (HPCVD) are reviewed. The distinct kind of $MgB_2$ films, such as single-crystal like $MgB_2$ thin films, $MgB_2$ epitaxial columnar thick films, and a-axis-oriented $MgB_2$ films are included for flux pinning mechanism investigation. Various attempts made by researchers to improve further the flux pinning property and $J_c$ performance by means of doping in $MgB_2$ thin films by using HPCVD are also summarized.
A safe and cost-effective PMMA carbon source for MgB<sub>2</sub>
Ranot, Mahipal,Jang, S.H.,Shinde, K.P.,Sinha, B.B.,Bhardwaj, A.,Oh, Y.S.,Kang, S.H.,Chung, K.C. The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.1
Carbon is proven to be very effective in pinning the magnetic vortices and improving the superconducting performance of $MgB_2$ at high fields. In this work, we have used polymethyl methacrylate (PMMA) polymer as a safe and cost effective carbon source. The effects of molecular weight of PMMA on crystal structure, microstructure as well as on superconducting properties of $MgB_2$ were studied. X-ray diffraction analysis revealed that there is a noticeable shift in (100) and (110) Bragg reflections towards higher angles, while no shift was observed in (002) reflections for $MgB_2$ doped with different molecular weights of PMMA. This indicates that carbon could be substituted in the boron honeycomb layers without affecting the interlayer interactions. As compared to undoped $MgB_2$, substantial enhancement in $J_c(H)$ properties was obtained for PMMA-doped $MgB_2$ samples both at 5 K and 20 K. The enhancement could be attributed to the effective carbon substitution for boron and the refinement of crystallite size by PMMA doping.
Ranot, Mahipal,Jang, S.H.,Oh, Y.S.,Shinde, K.P.,Kang, S.H.,Chung, K.C. The Korea Institute of Applied Superconductivity a 2016 한국초전도저온공학회논문지 Vol.18 No.1
We have investigated the addition effect of NiO magnetic nanoparticles on crystal structure, microstructure as well as superconducting properties of $MgB_2$. NiO-added $MgB_2$ samples were prepared by the solid-state reaction method. The superconducting transition temperature ($T_c$) of 37.91 K was obtained for pure $MgB_2$, and $T_c$ was found to decrease systematically on increasing the addition level of NiO. X-ray diffraction (XRD) analysis revealed that no substitution of Ni for Mg in the lattice of $MgB_2$ was occurred. The microstructural analysis shows that the pure $MgB_2$ sample consists of plate shape $MgB_2$ grains, and the grains get refined to smaller size with the addition of NiO nanoparticles. At 5 K, high values of critical current density ($J_c$) were obtained for small amount NiO-added $MgB_2$ samples as compared to pure sample. The enhancement in $J_c$ could be attributed to the refinement of $MgB_2$ grains which leads to high density of grain boundaries in NiO-added $MgB_2$ samples.