Improved trapped field performance of single grain Y‐Ba‐Cu‐O bulk superconductors containing artificial holes

Abstract: The intrinsic mechanical properties of single‐grain RE‐Ba‐Cu‐O bulk high‐temperature superconductors can be improved by employing a thin‐wall geometry. This is where the samples are melt‐processed with a predefined network of artificial holes to decrease the effective wall thickness. In this study, the tensile strengths of thin‐wall YBCO disks were determined using the Brazilian test at room temperature. Compared with conventional single grain YBCO disks, the thin‐wall YBCO disks displayed an average tensile strength that is 93% higher when the holes were filled with Stycast epoxy resin. This implies a thin‐wall sample should, in theory, be able to sustain a trapped field that is 39% higher without exceeding the mechanical limit of the sample. High‐field magnetization experiments were performed by applying magnetization fields of up to 11.5 T, specifically to break the samples in order to verify the effect of increased mechanical strength (and improved cooling) on the ability of bulk (RE)BCO to trap field successfully. The standard YBCO sample failed when it was magnetized with a field of 10 T at 35 K, suffering permanent damage. As a result, the standard sample could only trap a maximum surface field of 7.6 T without failure. On the other hand, the thin‐wall YBCO sample survived all magnetization cycles, including a maximum magnetization field of 11.5 T at 35 K, demonstrating a greater intrinsic ability to withstand significantly higher electromagnetic stresses. By subsequently field‐cooling the thin‐wall sample with 11 T at 30 K, a surface field of 8.8 T was trapped successfully without requiring any external ring reinforcement

Thermomechanical analysis as a useful tool to study photoinduced changes of the viscous flow of glassy materials

A modified thermomechanical analyzer is described as an useful tool to study the photoinduced changes in the viscous flow and thermal properties of glassy materials. The device proposed was tested on model chalcogenide glass As2S3 using the penetration method. Further, the article discusses and summarizes the effect of the light illumination (at wavelength of 650 nm) on the viscous flow at different temperatures below the glass transition temperature (Tg), and on the thermal behaviour interpreted from dilatometric curves via glass transition temperature and softening temperature

Phosphinate MOF formed from tetratopic ligands as proton conductive materials

Metal organic frameworks (MOFs) are attracting attention as potential proton conductors. There are two main advantages of MOFs in this application: the possibility of rational design and tuning of the properties, and clear conduction pathways given by their crystalline structure. We hereby present two new MOF structures, ICR-10 and ICR-11, based on tetratopic phosphinate ligands. The structures of both MOFs were determined by 3D electron diffraction. They both crystallize in the P-3 space group and contain arrays of parallel linear pores lined with hydrophilic non-coordinated phosphinate groups. This, together with the adsorbed water molecules, facilitates proton transfer via the Grotthuss mechanism, leading to the proton conductivity up to 4.26∙10-4 S cm-1 for ICR-11

Critical current density function of the position in a commercial REBaCuO bulk

International audienceAdvances in the melt-growth synthesis technique for preparing superconducting REBaCuO bulks allow the production and commercialisation of single crystals with a diameter of about 10 cm. This is in close agreement with the development of new applications such as electric motors where superconducting bulks are used as trapped field magnets or magnetic screens [1], [2]. It is then crucial to determine the superconducting properties such as critical temperature, critical current density and irreversible magnetic field, which is usually done using MPMS-SQUID on a millimetre size sample. In this study, the characterisation of a 10 cm wide commercial bulk machined for use as a magnetic shield is presented, see Fig. 1. 24 orthorhombic samples were extracted at different positions from the centre of the bulk, prepared and measured on a 14 T MPMS with a VSM head. A comparison of the superconducting properties of each sample will be presented together with the trapped field measurements performed on 10 other wide REBaCuO bulks. This will provide an opportunity to discuss the state of the art of this technology and its possible future development and will highlight the need to measure superconducting properties in different positions. Fig. 1: Magnetic flux density map measured on the surface of a REBaCuO bulk after magnetisation under 300 mT using a permanent magnet. References [1] Dorget, R. et al. Design of a 500 kW partially superconducting flux modulation machine for aircraft propulsion

Critical current density function of the position in a commercial REBaCuO bulk

International audienceAdvances in the melt-growth synthesis technique for preparing superconducting REBaCuO bulks allow the production and commercialisation of single crystals with a diameter of about 10 cm. This is in close agreement with the development of new applications such as electric motors where superconducting bulks are used as trapped field magnets or magnetic screens [1], [2]. It is then crucial to determine the superconducting properties such as critical temperature, critical current density and irreversible magnetic field, which is usually done using MPMS-SQUID on a millimetre size sample. In this study, the characterisation of a 10 cm wide commercial bulk machined for use as a magnetic shield is presented, see Fig. 1. 24 orthorhombic samples were extracted at different positions from the centre of the bulk, prepared and measured on a 14 T MPMS with a VSM head. A comparison of the superconducting properties of each sample will be presented together with the trapped field measurements performed on 10 other wide REBaCuO bulks. This will provide an opportunity to discuss the state of the art of this technology and its possible future development and will highlight the need to measure superconducting properties in different positions. Fig. 1: Magnetic flux density map measured on the surface of a REBaCuO bulk after magnetisation under 300 mT using a permanent magnet. References [1] Dorget, R. et al. Design of a 500 kW partially superconducting flux modulation machine for aircraft propulsion

Critical current density function of the position in a commercial REBaCuO bulk

International audienceThe progress of the melt growth synthesis technique for preparing superconducting REBaCuO bulks allows the production and commercialization of a single crystal with a diameter of 10 cm. This is in good agreement with the development of new applications such as electrical motors where superconducting bulks are used as trapped field magnets or magnetic shields [1], [2]. It is then crucial to determine the superconducting properties such as the critical temperature, critical current density and irreversible magnetic field which is commonly done with the help of an MPMS-SQUID on a millimeter-size sample. However, the inhomogeneity of performances has been reported on a bulk [3], which highlights the necessity to measure the critical properties in multiple positions along the sample radius either in a grain sector or along a grain sector boundary.We propose a similar work with a characterization carried out on a 10 cm wide commercial bulk after machining for use as magnetic shields [1]. 24 rectangular samples have been extracted in a different position from the bulk’s center, prepared and measured on a 14 T MPMS with a VSM head. Then a comparison of the superconducting properties of each sample will be presented along with trapped field measurement done on 10 others wide GdBaCuO bulks. Finally, this will allow a discussion on the readiness of this technology and its possible future development and it will point out the necessity to measure the superconducting properties in different positions.[1]R. Dorget et al., « Design of a 500 kW partially superconducting flux modulation machine for aircraft propulsion », J. Phys. Conf. Ser., july 2021.[2]R. Dorget et al., « Review on the Use of Superconducting Bulks for Magnetic Screening in Electrical Machines for Aircraft Applications », Materials, jan. 2021.[3]V. Antal et al., « Relationship between local microstructure and superconducting properties of commercial YBa2Cu3O7- δ bulk », Supercond. Sci. Technol., févr. 2020

Critical current density function of the position in a commercial REBaCuO bulk

International audienceThe progress of the melt growth synthesis technique for preparing superconducting REBaCuO bulks allows the production and commercialization of a single crystal with a diameter of 10 cm. This is in good agreement with the development of new applications such as electrical motors where superconducting bulks are used as trapped field magnets or magnetic shields [1], [2]. It is then crucial to determine the superconducting properties such as the critical temperature, critical current density and irreversible magnetic field which is commonly done with the help of an MPMS-SQUID on a millimeter-size sample. However, the inhomogeneity of performances has been reported on a bulk [3], which highlights the necessity to measure the critical properties in multiple positions along the sample radius either in a grain sector or along a grain sector boundary.We propose a similar work with a characterization carried out on a 10 cm wide commercial bulk after machining for use as magnetic shields [1]. 24 rectangular samples have been extracted in a different position from the bulk’s center, prepared and measured on a 14 T MPMS with a VSM head. Then a comparison of the superconducting properties of each sample will be presented along with trapped field measurement done on 10 others wide GdBaCuO bulks. Finally, this will allow a discussion on the readiness of this technology and its possible future development and it will point out the necessity to measure the superconducting properties in different positions.[1]R. Dorget et al., « Design of a 500 kW partially superconducting flux modulation machine for aircraft propulsion », J. Phys. Conf. Ser., july 2021.[2]R. Dorget et al., « Review on the Use of Superconducting Bulks for Magnetic Screening in Electrical Machines for Aircraft Applications », Materials, jan. 2021.[3]V. Antal et al., « Relationship between local microstructure and superconducting properties of commercial YBa2Cu3O7- δ bulk », Supercond. Sci. Technol., févr. 2020