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https://ptsldigital.ukm.my/jspui/handle/123456789/499706| Title: | Ketumpatan arus genting antara butiran superkonduktor Bi1.6Pb0.4Sr2Ca2Cu3O10 dalam bentuk pukal dan pita bersarung perak dengan penambahan nanozarah magnet NiF2, CoFe2O4 dan Co0.5Ni0.5Fe2O4 sebagai pusat pengepinan fluks |
| Authors: | Muhammad Hafiz Mazwir. (P62275) |
| Supervisor: | Roslan Abd-Shukor, Prof. Dato Dr. |
| Keywords: | Nanozarah Superkonduktor Pengepinan fluks Flux pinning. |
| Issue Date: | 31-Jul-2015 |
| Description: | Kesan penambahan zarah bersaiz nanometer NiF2, CoFe2O4 dan Co0.5Ni0.5Fe2O4 terhadap sifat superkonduktor (Bi1.6Pb0.4)Sr2Ca2Cu3O10 (Bi-2223) dalam bentuk pukal dan pita telah dikaji. Serbuk superkonduktor Bi1.6Pb0.4Sr2Ca2Cu3O10 telah disediakan menggunakan teknik sepemendakan. Nanozarah NiF2, CoFe2O4 dan Co0.5Ni0.5Fe2O4 dengan saiz masing-masing 10 nm, 60 nm dan 20 nm telah ditambah ke dalam superkonduktor Bi1.6Pb0.4Sr2Ca2Cu3O10 dengan komposisi nominal 0.00, 0.01, 0.02, 0.03, 0.04 dan 0.05% berat. Kesan penambahan nanozarah ke atas pembentukan fasa, mikrostruktur, suhu genting dan ketumpatan arus genting, Jc dalam medan sifar dan dalam medan magnet telah dikaji. Keputusan pembelauan sinar-X (XRD) menunjukkan sampel dengan penambahan nanozarah Co0.5Ni0.5Fe2O4 mempunyai pecahan isipadu fasa Bi-2223 tertinggi berbanding sampel lain. Sampel dengan penambahan nanozarah NiF2 menunjukkan fasa Bi-2223 yang lebih rendah berbanding dengan sampel tanpa tambahan. Suhu genting sifar, Tc-sifar bagi sampel tanpa tambahan adalah 97 K. Sampel dengan penambahan nanozarah Co0.5Ni0.5Fe2O4 0.01% berat menunjukkan Tc-sifar tertinggi iaitu 102 K yang melebihi suhu genting sifar sampel tanpa tambahan. Tc-sifar tertinggi bagi sampel dengan penambahan NiF2 dan CoFe2O4 adalah 96 K (0.04% berat) dan 99 K (0.01% berat) masing-masing. Sampel dengan penambahan nanozarah dalam kuantiti yang lain menurunkan nilai Tc-sifar . Ketumpatan arus genting dalam medan sifar bagi semua sampel dengan penambahan nanozarah adalah lebih tinggi daripada sampel tanpa tambahan. Sampel dengan nilai Jc maksimum telah dipilih untuk dibuat ke dalam bentuk pita bersarung perak iaitu sampel dengan penambahan 0.04% berat NiF2, 0.01% berat CoFe2O4 dan 0.01% berat Co0.5Ni0.5Fe2O4. Pita disediakan menggunakan kaedah serbuk dalam tiub (PIT) dan dibahagikan kepada dua kumpulan yang disinter pada suhu 845°C selama 50 dan 100 jam. Analisis XRD menunjukkan kesemua sampel pita mempunyai fasa Bi-2223 sebagai fasa dominan dan fasa sekunder Bi-2212. Kesemua sampel pita menunjukkan nilai Jc dalam medan sifar sebanyak dua hingga tiga kali lebih tinggi berbanding sampel tanpa penambahan nanozarah. Ini menunjukkan penambahan nanozarah meningkatkan ketumpatan arus genting superkonduktor (Bi1.6Pb0.4)Sr2Ca2Cu3O10. Sampel yang disinter selama 100 jam juga menunjukkan nilai Jc yang lebih tinggi daripada sampel yang disinter selama 50 jam. Pada suhu 30 K, Jc pita dengan penambahan nanozarah NiF2, CoFe2O4 dan Co0.5Ni0.5Fe2O4 yang disinter selama 100 jam adalah 17270 A/cm 2 , 22420 A/cm 2 dan 19830 A/cm 2 masing-masing. Jc pita tanpa tambahan pada suhu 30 K adalah 8280 A/cm 2 . Jc berkurang dengan peningkatan suhu akibat daripada rayapan fluks diaktifkan secara terma. Jc dalam medan magnet bagi pita dengan penambahan nanozarah juga adalah lebih tinggi berbanding pita tanpa tambahan. Jc menurun apabila kekuatan medan magnet ditambah. Tenaga pengepinan fluks bagi sampel dalam bentuk pukal turut dikira dan tenaga pengepinan tersebut menunjukkan korelasi dengan nilai Jc. Kajian ini menunjukkan kehadiran nanozarah NiF2, CoFe2O4 dan Co0.5Ni0.5Fe2O4 dalam kuantiti yang kecil mampu meningkatkan ketumpatan arus genting superkonduktor (Bi1.6Pb0.4)Sr2Ca2Cu3O10.,The effects of nanometer sized particles NiF2, CoFe2O4 and Co0.5Ni0.5Fe2O4 addition on the superconducting properties of (Bi1.6Pb0.4)Sr2Ca2Cu3O10 in bulk and tape form were investigated. (Bi1.6Pb0.4)Sr2Ca2Cu3O10 superconductor powder was prepared using co-precipitation technique. NiF2, CoFe2O4 dan Co0.5Ni0.5Fe2O4 nanoparticles with average sizes of 10 nm, 60 nm and 20 nm respectively were added to the (Bi1.6Pb0.4)Sr2Ca2Cu3O10 superconductor with nominal composition 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 wt.%. Effect of the nanoparticles addition on the phase formation, microstructure, critical temperature and critical current density, Jc in zero and applied magnetic field was investigated. X-ray diffraction (XRD) results showed that samples with Co0.5Ni0.5Fe2O4 nanoparticle addition have the highest Bi-2223 phase volume fraction compared to other samples. Samples with NiF2 nanoparticle addition showed a lower Bi-2223 phase volume fraction compared to the non-added samples. The zerocritical temperature, Tc-zero for non-added sample was 97 K. The sample with 0.01 wt.% Co0.5Ni0.5Fe2O4 addition showed the highest Tc-zero of 102 K, which is higher than the critical temperature for non-added sample. The highest Tc-zero for samples with NiF2 and CoFe2O4 additions were 96 K (0.04 wt.%) and 99 K (0.01 wt.%), respectively. Samples with nanoparticles addition in other quantities showed a lower Tc-zero value. Critical current density in self-field for all samples with nanoparticle addition was higher than non-added samples. Samples with the maximum Jc were chosen to be fabricated into Ag-sheathed tapes which were 0.04 wt.% NiF2, 0.01 wt.% CoFe2O4 and 0.01 wt.% Co0.5Ni0.5Fe2O4 added samples. The tapes were prepared using the powder-in-tube (PIT) method and divided into two groups sintered at 845 °C for 50 and 100 h. XRD analysis showed Bi-2223 as the dominant phase in all tape samples, with Bi-2212 as the secondary phase. All tapes showed two to three times higher value of Jc in zero-field compared with non-added tapes. This shows that the addition of nanoparticles increased the critical current density of (Bi1.6Pb0.4)Sr2Ca2Cu3O10 superconductor. Tapes that were sintered for 100 h also showed a higher value of Jc compared to tapes that were sintered for only 50 h. At 30 K, Jc for tapes with NiF2, CoFe2O4 and Co0.5Ni0.5Fe2O4 addition sintered for 100 h were 17270 A/cm 2 , 22420 A/cm 2 and 19830 A/cm 2 , respectively. Jc of non-added tape at temperature of 30 K was 8280 A/cm 2 . Jc decreased with increasing temperature due to thermal flux creep. Jc in applied magnetic field of tapes with nanoparticle is also higher compared with non-added tapes. Jc decreased when the applied magnetic field was increased. Flux activation energy in bulk samples was calculated and it showed correlation with value of Jc. This work showed that the presence of small amount of NiF2, CoFe2O4 and Co0.5Ni0.5Fe2O4 nanoparticles can increase the critical current density of (Bi1.6Pb0.4)Sr2Ca2Cu3O10 superconductor.,Ph.D |
| Pages: | 160 |
| Call Number: | QC611.96 .M846 2015 |
| Publisher: | UKM, Bangi |
| Appears in Collections: | Faculty of Science and Technology / Fakulti Sains dan Teknologi |
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