高温超导永磁体特性的实验研究
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摘要
非理想第Ⅱ类超导体内部存在的异常区，即钉扎中心，会对磁通线的运动产生阻碍作用，使超导体具有一定的剩磁而成为超导永磁体。高温超导永磁体的高场、高磁能积和良好的磁稳定性等特点为实用化铺平了道路。本文采用熔融织构法制备的高温超导YBCO块材在不同外场下进行励磁而成为超导永磁体。文中主要研究了高温超导永磁体在外场下的受力状况以及外场对其内部磁通量的影响、高温超导YBCO块材在不同脉冲场下的俘获磁通特性以及超导体块材自身的厚度、形状、密度等参数对其在外场下受到的悬浮力和俘获磁通的影响。相应得到如下结论：
◆超导永磁体的磁场很容易受到外界磁场的影响，在外场的作用下，超导永磁体的自身场强会增大或减小。
◆超导体在脉冲场下具有特殊的励磁特性，当脉冲场在1.9T左右时，由于在脉冲场下超导体内的磁通线运动受到较大的粘滞力作用，超导体表面中心的俘获场分布扫描图将出现一些凹陷区域，这是跟超导体在恒定场下的励磁和一般永磁体所不同的。
◆对高温超导磁悬浮车系统而言，厚度为25mm的圆柱形超导体在距离永磁导轨一定高度处场冷时，能保证车体运行时具有足够的侧向稳定性和悬浮高度。
◆超导体块材自身的密度跟它的俘获磁通能力之间并没有直接的联系，影响超导体俘获磁通能力的是超导材料内的弱连接和材料的临界电流密度，而超导体在一定外场下受到的悬浮力能够在一定程度上反映出它的俘获磁通性能。
Pinning centers, that are some abnormal regions in type II superconductors, will hinder the flux motion. Certain of remnant magnetism in a superconductor will make it to a superconducting permanent magnet. The high magnetic field, high (BH)max value and well magnetic stability are important characteristics for its practical applications. In this thesis, melt-textured YBCO bulk superconductors are used to make high temperature superconducting (HTS) permanent magnets by magnetizing it in different applied field. At first, the interactions of HTS permanent magnet and applied field are studied, that is the levitation force of YBCO bulks over the NdFeB guideway and the influences of the applied field to the HTS permanent magnet. Secondly, the pulsed field magnetization properties of YBCO bulks are studied. At last, the influence of the sample's thickness, shape as well as the density to the levitation force over the NdFeB guideway and the trapped flux of YBCO bulk are studied.
From all above studies, we can conclude that:
The magnetic field of HTS permanent magnet is easily be influenced by the applied field. When it is placed in a high-applied field, the magnetic field of it will be enhanced or decreased.
In pulsed field magnetization condition, we find some new phenomena characteristic, that is, the trapped fluxes of YBCO bulk increase with increasing intensity of applied field up to about 1.9T, but decease beyond this value and the scanning distribution map of the trapped fluxes on the surface of the superconductor is not slick, which is different with the superconductors magnetized in constant magnetic field and the normal permanent magnets.
For HTS MAGLEV vehicle, cylindrical bulk superconductors with the thickness of 25mm are better to provide enough guidance force and keep enough levitation height when they are field cooled above the NdFeB guideway.
The trapped flux ability of superconductors is influenced by the weak links and critical current density and can be reflected by the levitation force. It has no direct relationship with its density.
◆超导永磁体的磁场很容易受到外界磁场的影响，在外场的作用下，超导永磁体的自身场强会增大或减小。
◆超导体在脉冲场下具有特殊的励磁特性，当脉冲场在1.9T左右时，由于在脉冲场下超导体内的磁通线运动受到较大的粘滞力作用，超导体表面中心的俘获场分布扫描图将出现一些凹陷区域，这是跟超导体在恒定场下的励磁和一般永磁体所不同的。
◆对高温超导磁悬浮车系统而言，厚度为25mm的圆柱形超导体在距离永磁导轨一定高度处场冷时，能保证车体运行时具有足够的侧向稳定性和悬浮高度。
◆超导体块材自身的密度跟它的俘获磁通能力之间并没有直接的联系，影响超导体俘获磁通能力的是超导材料内的弱连接和材料的临界电流密度，而超导体在一定外场下受到的悬浮力能够在一定程度上反映出它的俘获磁通性能。
Pinning centers, that are some abnormal regions in type II superconductors, will hinder the flux motion. Certain of remnant magnetism in a superconductor will make it to a superconducting permanent magnet. The high magnetic field, high (BH)max value and well magnetic stability are important characteristics for its practical applications. In this thesis, melt-textured YBCO bulk superconductors are used to make high temperature superconducting (HTS) permanent magnets by magnetizing it in different applied field. At first, the interactions of HTS permanent magnet and applied field are studied, that is the levitation force of YBCO bulks over the NdFeB guideway and the influences of the applied field to the HTS permanent magnet. Secondly, the pulsed field magnetization properties of YBCO bulks are studied. At last, the influence of the sample's thickness, shape as well as the density to the levitation force over the NdFeB guideway and the trapped flux of YBCO bulk are studied.
From all above studies, we can conclude that:
The magnetic field of HTS permanent magnet is easily be influenced by the applied field. When it is placed in a high-applied field, the magnetic field of it will be enhanced or decreased.
In pulsed field magnetization condition, we find some new phenomena characteristic, that is, the trapped fluxes of YBCO bulk increase with increasing intensity of applied field up to about 1.9T, but decease beyond this value and the scanning distribution map of the trapped fluxes on the surface of the superconductor is not slick, which is different with the superconductors magnetized in constant magnetic field and the normal permanent magnets.
For HTS MAGLEV vehicle, cylindrical bulk superconductors with the thickness of 25mm are better to provide enough guidance force and keep enough levitation height when they are field cooled above the NdFeB guideway.
The trapped flux ability of superconductors is influenced by the weak links and critical current density and can be reflected by the levitation force. It has no direct relationship with its density.
引文
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[24]Minzhi Wu. Preparation and melt textured growth mechanism of bulk high temperature superconductors for cryomagnetic applications. P13. (For Doctor Degree)
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[56] 丘明、韩朔、林良真．低温物理学报．vol．17(增刊)，1995，12：118-122
[57] K. Nagashima, T. Higuchi, J. Sok, S. I. Yoo, H. Fujimoto and M. Murakami. Cryogenics. 1997, vol. 37: 577—581
[58] 丘明、韩朔、林良真．低温与超导．1995(2)，vol．23：316-320
[59] K. Yamafuji et al., Cryogenics. 1990, vol. 30: 310
[60] Y. Ren, R. Weinstein et al., J. Appl. Phys. 1995, 74: 718
[61] 王家素，王素玉，林国彬，黄海于，张翠芳，曾佑文等．高温超导磁悬浮测试系统．高技术通讯．．2000；10(8)：56
[62] 王素玉，王家素．一种薄底液氮低温容器．低温与超导，1999，27(3)：1
[63] Y. B. Kim, C. F. Hemostead and A. R. Strnad. Phys. Rev. 1965, 139: A1163
[64] J. Bardeen and M. J. Stephen. Phys. Rev. 1965, 140: A1197
[65] T. Matsushita. Physica C. 1993, 205: 289
[66] 王素玉，唐启雪，任仲友，朱敏，江河，王家素．低温与超导，2001，29(1)：14
[67] 任仲友，王素玉，王家素等．低温与超导，2000，28(2)：17
[2]赵忠贤，陈立泉，崔长庚，黄玉珍，刘锦湘，陈赓华，李山林，郭树权，何业冶．科学通报．1987，32：412
[3]C. W. Chu et al. Phys. Rev. Lett. 1987, 58: 405
[4]M. K. Wu, J. R. Ashburn, C. J. Torng, P. H. Hor, R. L. Meng, L. Gao, Z. J. Huang, Y. Q. Wang and C. W. Chu, Phys. Rev. Lett. 1987, 58: 908
[5]H. Maeda, Y. Tanaka, M. Fukutomi and T. Asano. Jan. J. App. Phys. 1987, 26: L209
[6]C. Michel, M. Hervien, M. M. Bord, A. Grandin, F. Deslands, J. Provost and B. Vaveau. Z. Phys., 1987, B68: 412
[7]Z. Z. Sheng, A. M. Hermann, A. Elali, C. Almason, J. Estrada, T. Datta and R. J. Matson. Phys. Rev. Lett., 1988, 60: 937
[8]A. Schilling, et al. Science. 1993, 262: 1859
[9]S. N. Putilin, E. V. Antipov, O. Chmaissem and M. Marezio. Nature. 1993, 362: 226
[10]S. Jin, T. H. Tiefel, S. Nakahara, et al., Appl. Phys. Lett., 1990, 56: 1287
[11]Nippon Steeel news. 1991, 226: 1
[12]R. Weistein, I. G. Chen et al., Proceedings of the 3rd International Congress on Superconductivity, Munich. edited by K. Krishen and G. G. Burbuham(Pergamon, New York). 1992, 1148
[13]Y. X. Fu, H. C. Yang et al, Chinese Science Bulletin. 1994, 39: 455
[14]R. B. van Dover, E. M. Gyorgy et al., Nature. I989, 342: 355
[15]L. Civale, A. D. Marwick et al., Phys. Rev. Lett. 1991, 67: 648
[16]张其瑞．高温超导电性．浙江大学出版社．1992
[17]林德华编．超导物理基础与应用．重庆大学出版社．1992
[18]M. Murakami. Supercond. Sci. Tecnol. 5(1992): 185
[19]肖玲，任洪涛，焦玉磊等．低温物理学报．1995，17(增刊)：82
[20]任洪涛，肖玲，焦玉磊，郑明辉．低温与超导．2000，3：28
[21]Jin S, Tiefel T H, Sherwood R C et al., Appl. Phys. Lett., 1988, 52: 2027
[22]王家素，王素玉编著．超导技术应用．成都科技大学出版社．1995
[23]林德华编．超导物理基础与应用．重庆大学出版社．1992
[24]Minzhi Wu. Preparation and melt textured growth mechanism of bulk high temperature superconductors for cryomagnetic applications. P13. (For Doctor Degree)
[25]L. Ya. Viniko, G. A. Emelchenko et al., Physica C. 1989, 1359: 153-155
[26]R. N. Kleiman, D. L. Gammel et al., Phys. Rev. Lett. 1989, 62: 2331
[27]M. Murakami, S. Gotoh et al., Physica C. 1991, 321: 185-189
[28]G. W. Crabtree, W. K. Kwok et al., Physica C. 1991, 282: 185-189
[29]J. Manhart, D. Anselmeltt et al., Supercond. Sci. Technol. 1992, 5: 5125
[30]肖立业、韩朔、林良真．电工电能新技术．1994，3：16-18
[31]Murakami M. Ceramics International. 1997, 23: 203—207
[32]Yoshitaka. Itoh, Uichiro. Mizutani. Jpn. J. Appl. Phys. 1996, 35: 2114-2125
[33]M. Morita, M. Tanaka, T. Sasaki, M. Hashimoto and K. Sawano,. Advances in Superconductivity Ⅳ(Springer-Verlag, Tokyo), 1992, P. 447
[34]Weistein R, Liu J, Ren Y, Sawh R-P, Parks D, Foster C. an obot Ⅴ 1996 Proc 10th Anniversary HTS Workshop on Physics, Materials and Applications ed B Batlogg, C W Chu, W K Chu, D U Gubser and K A Muller(Singapore: World Scientific)
[35]Weinstein R, Sawh R, Ren Y and Liu J, 1997 Advances in superconductivity Ⅸ, ed s Nakajima and M Murakami(Tokyo: Springer): 539
[36]Ren Y., Weinstein R., Liu J. and Sawh R P. Very high trapped
fields:cracking, creep, and pinning centers. Presented at 10th anniversary HTS Workshop on Physics, Materials and Applications, Houston, TX, 1996, in press
[37] Weinstein R, Sawh R et al, Preprint of ASC'94
[38] Ikuta.Hi, Mase. A, Mizutani. U, Yanagi. Y, Yoshikawa. M, Itoh,.Y, Oka. T., IEEE Trans Appl Supercond., 1999, 9(2 □): 2219-2222
[39] Wen, HM, Lin, LZ, Xiao, L, Jiao, YL, Zheng, MH, Ren, HT. Phys C Supercond Appl, 2000, vol. 337, no. 1: 335-338
[40] 任洪涛、肖玲、焦玉磊、郑明辉．低温与超导．2000，28(3) ：28-33
[41] S.Nariki, N.Sakai, and M.Murakami. 14th International Symposium on Superconductivity, BS-11, Sept. 25-27, 2001
[42] S.Nariki, H.Hinai, N.Sakai, M.Murakami and M.Otsuka. 14th International Symposium on Superconductivity, BSP-20, Sept. 25-27, 2001
[43] G.Krabbes, G.Fuches, G.Stoever, P. Verges, S. Gruss. 14th International Symposium on Superconductivity, BS-12, Sept. 25-27, 2001
[44] 和德国高技术物理所吴民智博士个人通信结果
[45] S.L.Wipf, H.L.Laquer. IEEE Trans. Magn. 1989, Vol. 25: 1877
[46] S.Gotoh, M.Murakami, et al., J.Appl. Phys. 1992, Vol. 72: 2404
[47] K. Nakao, N. Miura, K. Tatsuhara, H. Takeya and H. Takei, Phys. Rev. Lett, 1989, vol. 63: 97
[48] K. Nakao, N. Miura, K. Tatsuhara, S. Uchida, H. Takagi, T. Wada, S. Tanaka, H. Takeya and F. Takei. Physica B, 1989, vol. 155: 156
[49] T. Takizawa, M. Kosaka, K. Kanbara, M. Morita and K. Sawano, Japn. J. Appl. Phys. 1991, vol. 30: L1790
[50] T. Takizawa, K. Kanbara, M. Morita and M. Hashimoto. J. Appl. Phys, 1993, vol. 32: L774
[51] T. Takizawa, T. Itoh, Y. Tanimura, K. Kanbara, M. Morita and M. Hashimoto. J. Appl. Phys. 1994, vol. 33: L631
[52] T. Itoh, Y. Tanimura, T. Takizawa, K. Kanbara, M. Morita and M. Hashimoto. Physica C, 1994, 3019: 235-240
[53] Y. Itoh and U. Mizutan. Pulsed field magnetization of melt-processed Y-Ba-Cu-O superconducting bulk magnet. Jpn. J. Appl. Phys., 1996, vol. 35: 2114-2125
54 Gruss S, Fuchs G, Krabbes G, Schaetzle P, Fink J, Mueller KH, Schultz L. IEEE Trans Appl Supercond, 1999, vol. 9, no. 2 (?): 2070-2073
[55] Fuchs G, Krabbes G, Schaetzle P, Gruss S, Verges P, Mueller Karl-Hartmut, Fink J, Schultz L. IEEE Trans Appl Supercond, 2000, vol. 10, no. 1: 890-893
[56] 丘明、韩朔、林良真．低温物理学报．vol．17(增刊)，1995，12：118-122
[57] K. Nagashima, T. Higuchi, J. Sok, S. I. Yoo, H. Fujimoto and M. Murakami. Cryogenics. 1997, vol. 37: 577—581
[58] 丘明、韩朔、林良真．低温与超导．1995(2)，vol．23：316-320
[59] K. Yamafuji et al., Cryogenics. 1990, vol. 30: 310
[60] Y. Ren, R. Weinstein et al., J. Appl. Phys. 1995, 74: 718
[61] 王家素，王素玉，林国彬，黄海于，张翠芳，曾佑文等．高温超导磁悬浮测试系统．高技术通讯．．2000；10(8)：56
[62] 王素玉，王家素．一种薄底液氮低温容器．低温与超导，1999，27(3)：1
[63] Y. B. Kim, C. F. Hemostead and A. R. Strnad. Phys. Rev. 1965, 139: A1163
[64] J. Bardeen and M. J. Stephen. Phys. Rev. 1965, 140: A1197
[65] T. Matsushita. Physica C. 1993, 205: 289
[66] 王素玉，唐启雪，任仲友，朱敏，江河，王家素．低温与超导，2001，29(1)：14
[67] 任仲友，王素玉，王家素等．低温与超导，2000，28(2)：17