Mark O Rikel

S-Innovations

The strain induced critical current degradation of overpressure processed straight Bi-2212/Ag wires has been studied at 77 K in self-field. For the first time superconducting properties, lattice distortions, composite wire stress and strain have been measured simultaneously in a high energy synchrotron beamline. A permanent I c degradation of 5% oc...

Industrial 2G HTS wires optimized for low-temperature application are studied using XRD. We aim at understanding the origin of noticeable variation of the lift factor LF = J_c (20K, 8T)/ J_c (77 K, sf) with the final goal of narrowing down the statistical scatter of the performance in production wires. Two approaches are us...

A presentation at EUCAS 2023

Using conventional XRD with Cu K_alpha radiation is usually sufficient to probe the whole thin-layer architecture of 2G HTS wire. In our quality control and R&D studies, we extract from XRD patterns information on layer thickness t (line broadening analysis for t < ~300 nm or analysis of absorption effects for t > ~300 nm), texture (out-of-plane an...

The chapter presents summary of theory and practice of ceramic processing and reviews their application to processing bulk and prercursor HTS materials (YBCO and BSCCO).

Progress at D-Nano in all-CSD technology for industrial production of coated conductors is presented, including upscaling production to 40 mm width conserving high (> 310 A/cm) performance, adjusting technology to Ni9W based RABITS, improving charactzerization capability (continuous Ic tester) and wire customization (slitting).

We report a successful fabrication of long-length RABiTS-based coated conductors (CC) via chemical solution deposition starting from colloidal YBa2Cu3O7-δ (YBCO) solutions containing 5 mol-% preformed BaMO3 (M = Hf, Zr) nanocrystals. Partial optimization of the existing continuous reel-to-reel YBCO processing via design of experiments (DoE) approac...

Disclosed is an at least 10 m long superconductor tape comprising a substrate, a buffer layer, and a high-temperature superconductor layer, wherein the buffer layer contains 5 to 30 at% carbon. Processes for producing such a tape comprise two or three heating steps of a carbon-containing buffer layer precursor solution in different reducing and/or...

Chemical solution deposition (CSD) of YBa2Cu3O7−δ (YBCO) nanocomposites from colloidal precursor solutions containing double metal oxide preformed nanocrystals is a promising, cost-effective and reproducible approach to produce superconducting films with high critical current density (Jc) and enhanced pinning. Here, the influence of the preformed n...

We investigate experimentally the anisotropy of the temperature dependence of the thermal conductivity of bulk Bi2Sr2CaCu2O8 (Bi-2212) cylinders fabricated by the melt-cast process. The thermal conductivity κ(T) along the axial and azimuthal directions are found to be equal within experimental uncertainty, while κ along the radial direction is foun...

We report developing an industrial-scale technology for production of Ni-9at.% W RABITS non-ferromagnetic above 60K. Several industrial (~1 ton) batches of 60 µm thick RABITS rolled in up to 800 mm width with ~100 m/min speed were produced from a 10 ton ingot. The average cube texture obtained in long length tapes (300 to 500 m) was 99.0(3) % (<16...

57) Abstract: The present invention is in the field of oriented metal substrates for high temperature superconductor tapes. In particular, the present invention relates to a process for preparing metal tapes with a high degree of cube texture comprising (a) reducing the thickness of the metal tape and (b) heating the metal tape to a temperature abo...

We describe how the contribution of crystallographic texture to the anisotropy of the resistivity of polycrystalline samples can be estimated by averaging over crystallographic orientations through a geometric mean approach. The calculation takes into account the orientation distribution refined from neutron diffraction data and literature values f...

Two-shell scheme consisting of an outer ferromagnetic tube and an inner superconducting cylinder was experimentally verified as promising design concept for making magnetic cloaks of centimeter size. Because some applications may require bigger sizes of the shielded volume, scalability of dimensions is an important parameter in the assessment of va...

Based on simultaneous in situ high energy synchrotron micro-tomography and x-ray diffraction (XRD) measurements we compare the microstructural changes and the formation of second phases and texture during the processing of Bi-2212 round wires with 15 μm filament diameter (multifilament) and 650 μm filament diameter (monofilament) fabricated using i...

The electromechanical properties of different cuprate high-temperature superconductors, notably two ReBCO tapes, a reinforced and a nonreinforced Bi-2223 tape, and a Bi-2212 wire, have been studied. The axial tensile stress and strain, as well as the transverse compressive stress limits at which an irreversible critical current degradation occurs,...

We have studied the influence of the oxygen partial pressure pO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> up to 5.5 bar on the phase changes that occur during the melt processing of a state-of-the-art Bi-2212 multifilamentary wire. Phase changes have been monitored in situ by high energy...

Spatial distribution of intensity ratio of modulation (020,+1) and structural (200,020) lines in the XRD patterns of melt-processed multifilamentary Bi-2212 round wire gives clear evidence of biaxial texture of Bi-2212 grains with c axis perpendicular to the wire axis and the modulation direction b parallel to the wire axis. This confirms the earli...

A precursor material for the preparation of superconductors based on Bi2Sr2Ca1Cu2O8+δ wherein the precursor material which is as close to equilibrium state as possible, i.e., has less than 5% in average 2201 intergrowths in the 2212 phase; in particular, the present invention relates to a precursor material, which is converted to the final conducto...

The presentaton summarizes the work done at Nexans SuperConductors within EUCARD2 project concerning three topics: (1) the issue of hard particles obserevd in Bi-2212 precursor powder for OPIT wires prepared at Nexans Supercondcutors using melt-cast processing technology (2) preliminary studies of various cation compostions and interplay between ca...

The objective of this thesis was to investigate in more detail the texture in Bi-2212 tubes and rods. The motivation was twofold : (i) on the one hand, a better understanding of the influence of the synthesis parameters on the microstructure, texture and superconducting properties could lead to a further improvement of the current carrying ability...

- Optimum doping of Bi2212 strongly depends on cation composition. Reducing Sr/Ca ratio in the Bi2212 phase shifts optimum doping to higher O index δ /* to be quantified using equilibrium samples */. - Optimizing Jc needs overdoping Δδ = δmax_Jc-δmax_Tc that increases from 0.024(3) at 77 K to 0.061(6) at 4.2 K /* to be double checked for all compo...

Bi 2 Sr 2 CaCu 2 O 8+δ HTSC superconductor is characterized by a very strong normal-state resistivity anisotropy, with ρ c /ρ ab typically above 10 4 . The aim of this study is to use Quantitative Texture Analysis from x-ray diffraction measurements to estimate the orientation effect on the anisotropic macroscopic resistivity in melt-cast bulk Bi 2...

A multilayer superconducting wire 7 with essentially round cross sectional area where the outer surface of the round wire is provided with a high temperature superconductor layer 3 and where at least the high temperature superconductor layer 3 is fabricated as a spiral running along the length of the superconductor wire 7 in parallel lanes 15.

Data are presented giving more details on structureral and compostional inhomogeneities in the MOD-LZO on NiW RABITS described in the ASC2010 publication. These are related to (1) fluorite-to-pyrochlore transformation in LZO; (2) compostional stratification of the LZO layer. The exact reasons for both phenomena remain unclear.

A coated conductor comprising an improved buffer layer architecture where the buffer layers are obtainable by chemical solution deposition and where the buffer layers essentially adopt the degree of texture of the substrate.

Method of depositing a layer of oxide of at least one metal element on a curved surface of a textured metal substrate, said method comprising the following steps: (1) a layer of a precursor of at least one oxide of a metal is deposited using an organic solution of at least one precursor of said metal, this solution preferably having a viscosity, m...

A coated conductor with a substantially round cross section has a high temperature superconductor layer which is sandwiched between an inner substrate layer and an outer substrate layer to place the high temperature superconductor layer in the region of neutral strain axis.

Method of depositing a buffer layer of epitaxial metal oxide on a functionalised surface of a textured metal substrate, said method comprising the following steps: (1) a layer is deposited of a precursor of an oxide of the type A2−xB2+xO7 where A represents a metal of valency 3 or a mixture of several of these metals, and B a metal of valency 4, a...

An introduction to basic properties of BSCCO 2212 and 2223 compounds and processing principles of 1G wires.

A coated conductor is provided with improved electrical connection between the conductive layers such as the high temperature superconductor layer and a metal protection layer applied onto the high temperature superconductor layer and the substrate. A method includes obtaining such electrical connection, in particular, creating a coated conductor w...

A process for preparing a shaped substrate suitable in the production of coated conductors which process allows the deformation of a textured substrate onto which a textured buffer layer has been already grown.

Melt-cast processed (MCP) Bi-2212 bulk samples (rods and tubes) from Nexans and melt processed Ag sheathed multifimanetary round wires from Oxford Superconductiong Technologies were studied to assess the effect of texture on the O doping state that optimizes self-field critical current densities Jc(77 K). It is shown that significant overdoping is...

After briefly reviewing the present understanding of the nucleation process of YBCO films, a new approach is presented to enhance the stability of c-axis nucleation in epitaxial chemical solution deposited YBCO thin films derived from TFA precursors. We show that with silver addition to the TFA precursor c-axis nucleation can be reached in a wide r...

The Jc(77K, sf) dependence on O contents in Bi2212 Melt Cast Processed bulk rods and tubes with only slight preferred orientation and Ag sheathed round wires (19x85; 1.2 mm ; OST) textured via partial melt processing was studied and shown to be of the same dome-like type as the Tc vs O contents. Different overdoping levels optimizing Jc found in MC...

Nexans experience in developing all CSD processes for coated conductors with the YBCO/CGO/LZO/Ni-5% W RABITS architecture is summarized. The chosen CC architecture has a principal disadvantage that the next layer only clones, but more often deteriorates the out-of-plane texture of the previous layer (in average by ~ 20% for LZO). Depending on the q...

Nexans SuperConductors GmbH (NSC) has successfully designed, built and tested the first two HTS Fault Current Limiter (FCL) systems on a commercial basis for two different application cases in Europe. Both systems are live in the customer grids since last quarter of 2009: The first one is installed in UK where it acts as a bus bar coupler in a MV g...

The present changes in electricity networks like the rampup of distributed generation and the stronger need for interconnection result in an increasing demand for protection against high short-circuit currents. Superconducting fault current limiters (SFCL) provide a completely new and efficient approach to the reliable handling of such faults. The...

The invention relates to a method for depositing an epitaxial metal oxide buffer layer onto the functionalised surface of a textured metal substrate, said method including the following steps: (1) depositing a layer of an A2-XB2+XO7 oxide precursor, where A is a metal having a valence of 3 or a mixture of a plurality of such metals, and B is a meta...

A procedure is developed for assessing the epitaxy of La_2- x Zr₂₊ x O₇ (LZO) layers on NiW RABITS. Comparing XRD patterns ( thetas -2thetas scans and 2D rocking curves) of LZO films of known thickness (ellipsometry or reflectometry measurements) with those of standard samples (100% epitaxial LZO film and an isotropi...

Different layer architectures produced by only MOD, only MOCVD and combinations of MOD buffers and MOCVD YBCO are presented. RTR MOCVD-YBCO layers obtained on MOD-CeO₂/MOD-LZO/Ni5 at%W tapes demonstrate critical current densities up to 2 MA/cm² at 77 K. On single LZO (50-100 nm) buffered Ni5 at%W tapes from Nexans Superconduct...

The work addresses the question of strong dependence of critical current densities Jc(4.2K) in Bi-2212 conductors on overall cation composition and is focused on studies of partially melt processed dip-coated tapes. The major conclusions: The significant effect of overall cation composition on Jc in melt processed Bi2212 conductors cannot be explai...

Using DTA measurements and SEM/EDX and XRD of isothermally annealed and rapidly cooled/quenched 2212/Ag conductors, we study the effect of precursor composition on the melting temperatures, composition and abundance of phases in the partially molten state.

Efforts to increase critical current density (Jc) and engineering current density (JE) in round multifilament Bi‐2212/Ag wires have included studies of the effect of precursor composition. Variations in the cation ratios in the precursor have a number of effects on conductor processing and properties, including the melt temperature, the relative sh...

Metastable phase states of BPSCCO 2223 precursor were studied as a function of annealing temperature, time, and oxygen partial pressure. Reproducible, but path-dependent changes in precursor phase composition during annealing are mostly governed by changes in Pb solubility in the (Bi,Pb)2212 phase. Studying phase formation upon heat treatment of ta...

We studied reactions between Ag-sheathed Bi2Sr2CaCu2Ox (2212) conductors and a variety of oxides. We identified two intrinsic reactions: solid-state diffusion of a metallic species from the 2212 melt through the Ag sheath to react with an oxide, and direct reaction between Ag and an oxide. The dominant species that diffused through the Ag sheath wa...

Nexans activities on HTS materials are briefly reviewed with the emphasis on materials for magnet technology–Bi2212 bulk conductors for current leads, the first commercial application of HTS materials in electrical engineering; and long-length Ag-sheathed Bi2212 tape conductors for high magnetic field applications at low temperatures, the material...

Current advances at NEXANS on Bi2212 tapes are reported. Using “powder in tube” process and improved precursor rods, high-quality multifilamentary tapes, reinforced with AgMg outer sheath, have been produced in kilometric lengths. Meltprocessing parameters and tape thickness were optimised using short samples to attain engineering critical current...

Melt-processed Bi2Sr2Ca1Cu2O8+X/Ag tapes are now com. available in, long lengths. The melting step, which is mostly important for tape performance is difficult to control on the industrial scale. A dynamic approach is proposed. The melting step and subsequent annealing (2212-formation) step are sepd. For the melting step, the reel-to-reel transfer...

The effect of cooling conditions on microstructure and electromagnetic properties of Bi2212/Ag monocore tapes and multifilamentary round wires was studied. We found that using isothermal solidification at temperatures 5–8 °C below the peritectic decomposition temperature of the 2212 phase it is possible to consume almost all second-phase particles...

Heat treatments of monocore and multifilament Ag-sheathed 2223 tape were carried out using overpressure (OP) processing in a static and a flow OP system between 125 and 180 bar. Mass density measurements and microstructural observations of the oxide core show that OP processing densified the core, achieving up to 95±1% of the theoretical density. O...

We have measured the thermal and electrical conductivity of silver and silver alloy sheaths for Bi-2223 tapes. The thermal conductivity at 10 K varied from 1 to 104 Wm−1K−1 (the upper values are for Ag sheaths and the lower, 1–102 Wm−1K−1, for the alloy sheaths). The large spread of data for the alloy sheaths is due to the difference in composition...

Development of 2201 intergrowths in melt-processed Bi2212/Ag tapes was studied using X-ray diffraction (XRD). The density of intergrowths evaluated from the shifts of 0 0 l peaks in the XRD patterns was found to increase with increasing maximum processing temperature Tmax, as well as the annealing time tmax at Tmax varying from ∼3% (Tmax=887°C, tma...

The discovery of superconductivity at 39 K in magnesium diboride offers the possibility of a new class of low-cost, high-performance superconducting materials for magnets and electronic applications. This compound has twice the transition temperature of Nb3Sn and four times that of Nb-Ti alloy, and the vital prerequisite of strongly linked current...

The porosity remaining in Bi2212/Ag monocore tapes after melt processing is shown to be a function of the conductor geometry. The effect of other processing variables on the final microstructure was studied. It was found that increasing the length of the soak time, tm, at the maximum processing temperature increases the size of second-phase particl...

The discovery of superconductivity at 39 K in magnesium diboride, MgB2, raises many issues, a critical one being whether this material resembles a high-temperature copper oxide superconductor or a low-temperature metallic superconductor in terms of its behaviour in strong magnetic fields. Although the copper oxides exhibit very high transition temp...

The porosity and its effect on critical current density J_c of Ag-clad (Bi,Pb)₂Sr₂Ca₂Cu₃O_x (Bi-2223) tapes throughout important steps in their thermomechanical treatment was investigated by using mass density measurement, microstructural observation, and superconducting property cha...

We report on the effect of overpressure processing on the electromagnetic properties and microstructure of monocore and multifilamentary Bi2223/Ag tapes. Samples at various stages of the usual thermo-mechanical processing for Bi2223/Ag tapes (from as-rolled to fully processed) were subjected to annealing at 815-820°C for 18-108 h in a static Ar+O<s...

The Tc(x) and lattice parameters of (Pb1-xSnx)nMo6S8 (n = 1, 2) samples were measured. From these data, the positions of the tie lines between the Chevrel phase (CP) and liquid (Pb, Sn) at 1050°C were estimated. Based on this result, we reexamined all existing Tc(x) data on this system and showed that they can be presented as a universal ΔTc/Tc(x)...

The effect of conductor geometry, maximum melt-processing temperature, Bi2Sr2CaCu2Ox (2212) composition, and preannealing and intermediate rolling on grain alignment at the 2212/Ag interface was studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD).

In this study, we have applied the Pre-Anneal and Intermediate Rolling (PAIR) process to Ag-sheathed monocore Bi-2212 tapes. Initial results show that increasing the percent reduction decreased the amount of 14:24 AEC and Cu-free particles while increasing the amount of the Bi-2201 phase. However, grain alignment was adversely affected by sausaging...

Critical current densities and pinning mechanisms in lead (PMS) and tin (SMS) molybdenum sulfides are reviewed with the emphasis on materials science problems. In both compounds, pinning at grain boundaries is dominant only in fine-grained materials and in the low-field regime. In coarser grained materials, additional pinning behaviors (the maximum...

Bi-2212 multifilamentary tapes of different thicknesses (160 – 1420 µm) were melt processed with P total = 5atm and pO 2 = 1 atm. The critical current was measured at 4.2 K in self field. A thickness dependence of engineering critical current density (j e) was found with a maximum at about 300 µm. Flux penetration, microstructure and phase content...

Gravimetry and x-ray diffraction were used to study the kinetics and mechanism of internal oxidation in air at 300–600 °C of Ag–2 and 4 at.% Mg alloys. All the features typical of the non-Wagnerian behavior in more dilute alloys (the slower initial and faster intermediate kinetics, oxygen release from the samples at the late stages, and stabilizati...

It is known that internal oxidation of Ag--Mg alloys results in an increase of lattice parameter, the behavior attributed to formation of subnanometer-scale oxide clusters. On the other hand, gravimetry of oxidized alloy samples shows that the oxide species formed are extremely hyperstoichiometric. Studying the mechanism of oxidation in air at 300...

BSCCO tapes with dispersion hardened AgMg sheaths possess excellent mechanical properties but reach commonly only about 70-80% of the critical currents of Ag sheathed reference tapes. Investigating the temperature dependence of I_c and the (2223) phase content for two annealing steps on 19 filamentary Ag and AgMg sheathed tapes, character...

For the technical application of Bi(2223) tapes the use of a dispersion hardened AgMg sheath, with improved mechanical properties is of most importance. For the characterization of the strain sensitivity of the superconducting properties, the transport currents of the tapes were investigated with applied axial tensile strain, transverse compressive...

Bi2Sr2Ca2Cu3O10 (Bi-2223) tapes are prepared by the powder in tube (PIT) method. The mechanical properties of the tapes are significantly enhanced by Mg alloying the Ag sheath, i.e. by MgO dispersion hardening. The tolerable axial strain of the tapes is increased by a factor of 2 as compared with pure Ag sheathed tapes. The formation of the Bi-2223...

The structure of a PbMo6S8 superconducting polycrystalline film of Chevrel phase type was studied. HREM lattice images in projections (111), (110) and (100) were obtained and compared with computer-simulated ones. In (100) projection Pb atomic columns and Mo6S8 clusters were revealed. Lattice defects were defected. Grain boundaries were described a...

In order to examine the influence of tin alloying on the critical current Ic in bulk sintered samples of PbMo6S8, the possible formation of Pb(1-x)SnxMo6S8 solid solutions at 500-1150°C was studied, and their superconducting transition temperatures Tc were measured together with the temperature dependences of the upper critical field Hc2, the elec...