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Home Material Sciences Superconducting nanostructural magnesium-diborade-based material for cryogenic electrical machines

Superconducting nanostructural magnesium-diborade-based material for cryogenic electrical machines

Description

At the Institute for Superhard Materials (ISM) of the National Academy of Sciences of Ukraine (Kiev, Ukraine) in cooperation with the Institut fur Physikalische Hochtech-nologie e.V. (IPHT, Jena, Germany), the superconducting MgB2-based nanostructural (15-37 nm average grain size) materials with highest for nowadays superconductive (Fig.1) and mechanical characteristics have been developed by high pressure (2 GPa)-high temperature (HP-HT) synthesis. The materials have the following characteristics: at 20 K critical current jc≥1000-100 кА/сm2 up to 3Т field and the field of the irreversibility Hirr=8 Т, trapped magnetic field В=2Т, hardness НV=12.1 ± 0.08 GPa at P=4.9N, fracture toughness k1C=7.6± 2.0 МPаxm1/2, Young modulus Е=220 GPа and near-theoretical density. The MgB2 produced without additions has a critical current density in zero magnetic field of 918 kA/cm2 at 20 K and of 149 kA/cm2 at 35 K; MgB2 with Zr added at 20K in zero field has jc=1800 kA/cm2.

The MgB2 ingots can be HP-HT synthesized in the shape of cylinders up to 63 mm in diameter and 20 mm in height, square plates of sizes up to 25x25x10 mm3 and rectangular plates of sizes up to 25x21x10 mm3 (Fig.2a). HP-HT synthesized MgB2-based materials are about tree times cheaper than MT-YBCO ceramics.

Rather big rings or tubes can be produced using precompaction by broaching with a subsequent sintering (Fig. 2b), jc = 8 kA/cm2 at 20K.

The world-first MgB2-based electromotor has been constructed from high pressure high temperature synthesized MgB2 in cooperation with MAI and IPHT (Figs. 3, 4).

Innovative Aspect and Main Advantages

Interest for the electric machines that are working at the liquid hydrogen temperature is caused by the modern technological progress aimed at the substitution of fuel for aircrafts, combustion engines of autotransport and watertransport (submarines) for hydrogen as well as due to the development of the electrical power networks by which the electrical power should be transmitted at a great distances through the superconductive cables at the liquid hydrogen temperature and using liquid hydrogen as cooling agent. Because of this the superconductive electromotors and pumps for liquid hydrogen, which are more efficient than the traditional ones due to the essentially lower weight, much higher speed of operation in the reversion regime and higher specific output power on the rotor surface, will be of a high demand when changing to technologies utilizing liquid hydrogen. MgB2-based materials are rather cheap and easily produced. With increased dimensions of the high-pressure chamber, it would be possible to produce blocks of higher dimentions.

Areas of Application

Nanostructural MgB2 - based materials nowadays are most promising for cryogenic machines and devices (magnetic bearings, MAGLEV transport, electromotors, pumps for liquid gases, flywheels energy storage systems, fault current limiters, etc.) working at hydrogen temperatures (20 K).

Generalized dependences of jc on magnetic field
Fig. 1 Generalized dependences of jc on magnetic
field, μ0H, for HP-HT-synthesized MgB2 without
and with additions of Ta, Ti, Zr (2 and 10 wt %)

View of MgB2
Fig. 2 View of MgB2 –based blocks HP-HT synthesized measuring 17x17x5 mm3,
25.5x17x5 mm3 (a) and of a ring of size D58xd53xh22 mm synthesized at 1 Ar atm (b).

MgB2-based rotor
Fig. 3 MgB2-based rotor (40 mm in diameter and 75 mm long) of SC motor manufactured
in cooperation with the Moscow State Aviation Institute, Russia (MAI) and IPHT (Jena, Germany)
and its characteristics at 20 K.

General view (a) and principal scheme (b) of the world-first MgB2-based motor
Fig. 4 General view (a) and principal scheme (b) of the world-first MgB2-based
motor developed and constructed in the MAI, from high pressure-high temperature
synthesized MgB2 at the ISM.

Stage of Development

The developed nanostructural MgB2 –based material (UA patent 68888 А) has at present the highest level of superconductive characteristics known for MgB2-based materials from literature. The comparative tests of MgB2-based and MT-YBCO- based motors at the same temperature conditions have shown that MgB2-based motor competitive in such applications.

Contact Details

Institute for Superhard Materials of the National Academy of Sciences of Ukraine
Tatiana Alexeevna Prikhna
2, Avtozavodskaya Str., Kiev 04074, Ukraine
Tel.: +38044 430-1126
Fax: +38044 430-1126
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it , This e-mail address is being protected from spambots. You need JavaScript enabled to view it ,www. ism.kiev.ua

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