IDEA #8Z4LXI Melt-Textured Superconductive Ceramics For Cryogenics

MELT-TEXTURED SUPERCONDUCTIVE CERAMICS FOR CRYOGENICS Description walled MT-YBCO materials have been developed in coopera­ tion of the Institute for Superhard Materials of the National Academy of Sciences of Ukraine (Kiev, Ukraine) with the Institut fbr Physikalische Hochtechnologie e.V. (IPHT, Jena, Germany, Prof. Gawalek) and the CRETA/CNRS (Grenoble, France, Dr. X. Chaud). Their superconductive characteristics are shown in Fig.l. Fig. 2 MT-YBCO-based superconducting reluctance motor of 200 kW, 3000 rpm produced by "Oswald" (Miltenberg, Germany). For bulk MT-YBCO the batch process has been developed, by which high-quality blocks of size up to 45x45x18 mm3 and 90x45x18 mm3 can be produced. Innovative Aspect and Main Advantages The main advantages of cryogenic devices based on the exhib­ ited materials are the possibility to achieve high rotational speeds practically without friction; smooth movement in com­ bination with high linear speed; low inertia moment and flesh- like performances. Moreover the devices and machines have much lower weight and smaller sizes as compared with the traditional equipment. Areas of Application Presented superconductive materials can be used for magnet­ ic bearings (e.g., in separators, wind and fly-wheel energy stor­ age systems), in electromotors (linear and reluctance motors, motors where the low inertia moment for high-frequency reverse is necessary, for ship propulsion), in pumps for liquid gases pumping, in MAGLEV transport, in fault current limiters, etc. Stage of Development From the bulk MT-YBCO manufactured in the batch process the 200 kW (3000 rpm) experimental motor in cooperation with the "Oswald" factory has been produced and successful­ ly tested (Fig.2). Several platforms (in IPHT, Jena) and vehicle (in Moscow State Aviation Institute) for levitating people have been constructed. Contact Details Contact person: Prikhna Tatiana Institute for Superhard Materials of the NAS of Ukraine 2, Avtozavodskaya Str., 04074 Kiev, Ukraine Tel/Fax: (380-44) 430-11-26 Mob.: 8(097) 467-18-27 E-mail: prikhna@mail.ru, prikhna@iptelecom.net.ua Fig. 1 (a, b) - General view of thin-walled and bulk MT-YBCO ceramics, respectively; maximum inductions of 0.54 Τ for thin-walled blocks 16 mm in diameter, 10 mm in height (c) and of 1.44 Τ for bulk blocks 38x38x17 mm3 (d) have been obtained; the results of field-mapping of one batch of bulk MT-YBCO blocks witness to high homogeneity of their char­ acteristics (e). c c c Oxygenating of the thing-walled MT-YBCO ceramics under high oxygen pressure allows us to get material with a high critical current density j and mechanical characteristics. For thing- walled MT-YBCO at 77 K, j in the ab-plane is 85 kA/cm2 in 0 Τ field and is above 10 kA/cm2 in the fields up to 5 T, the field of irreversibility -9.8 T, and in the c- direction j is 34 kA/cm2 in 0 Τ field and above 2.5 kA/cm2 in 10 Τ field. Under 4.9 N load the microhardness of thin-walled MT-YBCO is 8.7±0.3 GPa in the ab-plane and 7.6±0.4 GPa in the c-direction, the fracture toughness being 2.5±0.1 and 2.29±0.1 MPa-m05, respectively; for the bulk MT-YBCO microhardness is 7.2±0.7 GPa in the ab-plane and 6.8±0.2 GPa in the c-direction and the fracture toughness is 1.6±0.3 MPa-m05 in the ab-plane, in the c-direction it is even higher.