Materials Science Consultant

Milano, Italy

Materials Science Consultant

Milano, Italy
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Li Z.,Northeastern University China | Wang J.,Shenyang Institute of Engineering | Zhang Y.,French National Center for Scientific Research | He K.,Northeastern University China | And 4 more authors.
Advanced Engineering Materials | Year: 2010

Ni45Co5Mn36.6In13.4 ribbons were prepared by the melt spinning technique. They are in the austenitic state at the room temperature with a Cubic L21 structure and are composed of columnar grains growing perpendicular to the ribbon plane. A nearly single {001} 〈1 0 0〉 cube component is formed at low wheel-rotating speed due to the preferential growth of nuclei in the ribbon plane normal and length directions. Appropriate control of the melt spinning condition offers a promising solution to the texturation of polycrystalline ferromagnetic shape memory alloys. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mochizuki H.,Iwate University | Fujishiro H.,Iwate University | Naito T.,Iwate University | Albisetti A.F.,EDISON S.p.A. | Giunchi G.,Materials Science Consultant
Superconductor Science and Technology | Year: 2015

We investigated the trapped field properties of the concentric-circled MgB2 bulk composite disk by pulsed field magnetization (PFM), which consists of 36 MgB2 thin rings for both surfaces of the disk and a small MgB2 central cylinder in the stainless steel disk. MgB2 parts were fabricated by a reactive Mg-liquid infiltration (Mg-RLI) method. The trapped field profile just above the composite surface was very concentric circled, which suggested that the superconducting current flows along the azimuthal direction in the MgB2 rings and the cylinder independently, even though the magnetic flux dynamically moves in the composite during PFM. The trapped field properties by PFM were reproduced qualitatively by the numerical simulation using the critical current density J c(B) of the MgB2 parts estimated by the trapped field B z by the field-cooled magnetization (FCM). The composite disk is a promising candidate to realize the MgB2 bulk magnet with concentric-circled trapped field distribution magnetized by PFM. © 2015 IOP Publishing Ltd.

Giunchi G.,Materials Science Consultant
20th IMEKO TC4 Symposium on Measurements of Electrical Quantities: Research on Electrical and Electronic Measurement for the Economic Upturn, Together with 18th TC4 International Workshop on ADC and DCA Modeling and Testing, IWADC 2014 | Year: 2014

The need of a superconducting magnetic shield erases in several physical apparatus, going from the small SQUID sensors to the large superconducting magnets for physical experimentation and clinical MRI. It is presented the possibility to realize cylindrical magnetic shields by HTS bulk MgB2 (Tc=39 K), obtained by the innovative process of Reactive Liquid Infiltration of the Mg melt in Boron powders. A complete shielding up to at least 2 T can be obtained also at the lower temperatures, 4.2 K, where thermal instabilities of the other LTS shields prevent their use.

Fujishiro H.,Iwate University | Ujiie T.,Iwate University | Naito T.,Iwate University | Albisetti A.F.,EDISON S.p.A. | Giunchi G.,Materials Science Consultant
Journal of Physics: Conference Series | Year: 2014

Pulsed field magnetization (PFM) was performed at Ts=14 K for the double stacked MgB2 bulks (bulk pair) 55 mm diameter fabricated by a reactive liquid Mg infiltration (Mg-RLI) method, compared with that for the single bulk. The trapped field of Bz=0.80 T was achieved between two bulks and Bz at the bulk surface was enhanced from 0.42 T to 0.50 T by stacking of the bulks. The trapped field characteristics of the bulk pair can be qualitatively explained by the model analyses. © Published under licence by IOP Publishing Ltd.

Patel A.,University of Cambridge | Kalitka V.,SuperOx | Hopkins S.C.,University of Cambridge | Baskys A.,University of Cambridge | And 6 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2016

Stacks of commercial higherature superconducting tape can be cut and soldered together to form slabs of a large range of shapes and sizes. They are most interesting for magnetic levitation applications due to the flexibility of geometry, allowing them to be created in large thin slabs suitable for planar rotary magnetic bearings and linear maglev bearings. In this paper, the axial levitation force was measured between a field cooled slab of 30 × 30 mm and a 25-mm-diameter rare-earth permanent magnet (PM), which produced a cylindrically symmetric field necessary in the context of rotary bearings. The force results were compared with that achieved between the same PM and a larger 43-mm-diameter bulk MgB2 disk, as well as to FEM modeling using the Perfectly Trapped Flux approximation. © 2016 IEEE.

Arpaia P.,University of Sannio | Arpaia P.,CERN | Ballarino A.,CERN | Giunchi G.,Materials Science Consultant | Montenero G.,CERN
Journal of Instrumentation | Year: 2014

A method for designing cylindrical hollow superconducting shields for cryogenic measurement devices operating in background fields of 1 T is proposed. The shield design is based on MgB2 composite, manufactured by the reactive Mg liquid infiltration process [1]. The MgB2composite allows low-cost shields with good mechanical resistance to be realized easily. The geometrical design is benchmarked by the experimental characterization at 4.2 K. A design case study for the shield of a cryogenic DC current transformer is reported. Design results show a shielding efficiency of 70% for both the axial and radial components, with prospective measurement accuracy up to 10 ppm on 100 kA. © CERN 2014.

Fujishiro H.,Iwate University | Mochizuki H.,Iwate University | Naito T.,Iwate University | Ainslie M.D.,University of Cambridge | Giunchi G.,Materials Science Consultant
Superconductor Science and Technology | Year: 2016

Pulsed field magnetization (PFM) of a high-J c MgB2 bulk disk has been investigated at 20 K, in which flux jumps frequently occur for high pulsed fields. Using a numerical simulation of the PFM procedure, we estimated the time dependence of the local magnetic field and temperature during PFM. We analyzed the electromagnetic and thermal instability of the high-J c MgB2 bulk to avoid flux jumps using the time dependence of the critical thickness, d c(t), which shows the upper safety thickness to stabilize the superconductor magnetically, and the minimum propagation zone length, l m(t), to obtain dynamical stability. The values of d c(t) and l m(t) change along the thermally-stabilized direction with increasing temperature below the critical temperature, T c. However, the flux jump can be qualitatively understood by the local temperature, T(t), which exceeds T c in the bulk. Finally, possible solutions to avoid flux jumps in high-J c MgB2 bulks are discussed. © 2016 IOP Publishing Ltd.

Fabbri M.,University of Bologna | Morandi A.,University of Bologna | Perini E.,EDISON SpA R and D Division | Giunchi G.,Materials Science Consultant
IEEE Transactions on Applied Superconductivity | Year: 2015

An innovative linear levitating system based on MgB2 bulks produced by the reactive liquid infiltration method is designed and built. Details of the system are presented. The levitation performance is also evaluated by means of previous experimental data. The linear levitating system consists of four MgB2 arc-shaped tiles lodged inside a double-shell Dewar sliding on a guide made of Nd-Fe-B permanent magnets. The magnets on the guide are properly arranged in a flux shaper configuration in order to produce maximum stiffness. Each MgB2 bulk has a curvature radius of 165 mm (arc length of 200 mm), thickness of 10 mm, and width of 70 mm. The system is cooled by means of a solid nitrogen heat sink. Helium gas supply to a heat exchanger is used in order to cool down the MgB2 slabs and the nitrogen at a temperature in the range of 20-30 K. When the flow of helium gas is interrupted, the temperature of the solid nitrogen remains below 39 K for half an hour. During this time interval, levitation measurements can be performed. Experimental verification of the cooling concept has been carried out successfully. © 2002-2011 IEEE.

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