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A novel substrate design is presented for scalable industrial production of filamentary coated conductors (CCs). The new substrate, called 'two level undercut-profile substrate (2LUPS)', has two levels of plateaus connected by walls with an undercut profile. The undercuts are made to produce a shading effect during subsequent deposition of layers, thereby creating gaps in the superconducting layer deposited on the curved walls between the two levels. It is demonstrated that such 2LUPS-based CCs can be produced in a large-scale production system using standard deposition processes, with no additional post-processing. Inspection of the conductor crosssection reveals that the deposited superconducting layer is physically separated at the 2LUPS undercuts. Filament decoupling is also seen in maps of the remanent magnetic field and confirmed by transport measurements.

A new glass-ceramic composition containing Si, Mg, Ca, Na, Al, Zr, and B is presented here as sealant for planar SOFCs/SOECs, with the aim of joining the metallic interconnect (Crofer22APU) to the solid oxide cell (YSZ electrolyte or CGO barrier layer). Characteristic temperature, thermo-mechanical properties, and compositional variations are reviewed and discussed by thermal analyses and in situ XRD, in order to design and optimize the sealing profile and reduce the residual porosity. The glass after heat treatment partially devitrifies into augite and nepheline with residual glass phase of around 64.3%; after crystallization the glass-ceramic sealant has a coefficient of thermal expansion of 12.8 9 10 À6 K À1 and it is compliant with the other materials typically used for stack components.This work shows that the developed glass-ceramic can successfully join the ceramic cell with the Crofer22APU (preoxidized and alumina coating), proven by tests on small and large-scale samples. No signs of unwanted reactions at the glass-metal and the glass-cell interface are observed and sufficient gas tightness is achieved. K E Y W O R D Sglass-ceramics, solid oxide fuel cell, synthesis, thermal analysis

High-temperature superconducting coated conductors (CCs) are considered an enabling ultra-high field (UHF) tape-conductor technology due to their extremely high engineering current densities at very high magnetic fields and low temperatures, and high mechanical strength. A major challenge is however related to induction of problematically large superconducting screening currents (as an effect of the large width-to-thickness ratio) when the wide tape conductors are exposed to strong transverse magnetic fields above 20 T, which is the case in many UHF magnet systems. Subdividing the superconducting layer into narrow parallel decoupled filaments has been shown to effectively reduce superconducting screening currents by a factor comparable to the number of filaments. The filamentization is however not effective until the induced coupling currents flowing across the filaments have decayed. The effectiveness of the multifilamentary structure in suppressing coupling currents and reducing the decay time constants is directly linked to potential current paths between filaments. Very recent experimental and numerical studies have examined both the challenge of magnet precision, caused by screening-current-induced fields, and the fatal consequences of local uneven tape stresses exceeding the irreversible limits for commercial CCs. These studies have conclusively revealed that screening currents must not be ignored in the mechanical design and other studies have introduced multifilamentary CCs as a viable solution. This paper aims to review the efforts made in developing and investigating multifilamentary CCs for ultra-high field applications focusing on the screening-current-related mechanisms, critical system-level effects, effectiveness of filamentization in UHFs, fabrication and large-scale analysis of multifilamentary CCs, in addition to providing cost estimates of previously studied filamentized CC fabrication techniques.

The formation of the FeSe compound from a mixture of Fe and Se powders encased in a composite Cu/Nb sheath was studied in situ by means of high-energy synchrotron x-ray diffraction. Tetragonal β-FeSe does not seem to form directly from the starting elements. Instead, a sequence of FeSe2, Fe3Se4 and Fe7Se8 phases formed prior to the main formation stage of β-FeSe at 350–370 °C, although a small amount of this phase appears at 250 °C already during a heating ramp of 2 °C min − 1. β-FeSe transforms to δ-FeSe around 480 °C and back to β-FeSe at 405 °C during cooling. There is no evidence for any interface reaction between the metal sheath and the superconducting core.

We compare the cost of a high temperature superconducting (SC) tape-based solenoid with a permanent magnet (PM) Halbach cylinder for magnetic refrigeration. Assuming a five liter active magnetic regenerator volume, the price of each type of magnet is determined as a function of aspect ratio of the regenerator and desired internal magnetic field. It is shown that to produce a 1 T internal field in the regenerator a permanent magnet of hundreds of kilograms is needed or an area of superconducting tape of tens of square meters. The cost of cooling the SC solenoid is shown to be a small fraction of the cost of the SC tape. Assuming a cost of the SC tape of 6000 $/m2 and a price of the permanent magnet of 100 $/kg, the superconducting solenoid is shown to be a factor of 0.3-3 times more expensive than the permanent magnet, for a desired field from 0.5-1.75 T and the geometrical aspect ratio of the regenerator. This factor decreases for increasing field strength, indicating that the superconducting solenoid could be suitable for high field, large cooling power applications.

A critical issue in state‐of‐the‐art solid oxide cell stacks is the contacting of the oxygen electrode. The commonly used ceramic contact layers are applied in a green state and cannot be sintered properly, due to compliance limitations arising from other stack components like sealing glasses and steels. The consequence is a low layer and interface strength. A metallic copper manganese foam, which is oxidized under operation conditions into a conductive Cu1+xMn2–xO4 spinel, is presented in this work as a viable contact solution. The foam has been electrochemically tested in a single repeating unit setup for 350 hours of constant operation, followed by dynamic conditions with thermal cycles. After operation, a micro structural analysis using scanning electron microscopy, energy dispersive X‐ray spectroscopy and X‐ray diffraction was carried out. It was confirmed that after oxidation/operation the manganese solely formed a CuMn‐spinel phase, mixed with a CuO phase. A separate Mn‐oxide phase was not found. The conductivity and contacting of the foam was sufficient for > 350 h of SOFC operation. With an initial serial resistance comparable to single cell tests using gold foil as contact material and moderate degradation rates, the CuMn foam presented itself as an interesting cathode contact solution.

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