Advanced Conductors Research Articles

Critical Current Measurement of REBCO Cables by Using a Superconducting Transformer

Development of REBCO cables that carry high electrical current in high magnetic field is crucial for future large-scale magnet applications. This experimental work presents the critical current measurements of two different REBCO cables by a test facility at the National High Magnetic Field Laboratory (NHMFL). The simple-stacked cable is made by the NHMFL by stacking 21 REBCO tapes without soldering. The Conductor on Round Core (CORC) cable provided by Advanced Conductor Technologies has 21 layers of REBCO tapes with 2 tapes/layer. The test facility consists of a 12 T split solenoid magnet with 15 cm bore providing transverse field to the samples, a superconducting transformer (SCT) as a current source providing up to 45 kA current. Special attention was paid to fabrication of solder joints between REBCO cables and the SCT output. The voltage-current traces were measured as a function of magnetic field at 4.2 K, from which the critical currents were determined. The details of this measurement are discussed.

3D FEM Modeling of ${\mathrm CORC}$ Commercial Cables With Bean’s Like Magnetization Currents and Its AC-Losses Behavior

The Conductor on Rounded Core (CORC) cables manufactured by Advanced Conductor Technologies with current densities beyond 300 Amm^-2 at 4.2 K, and bending diameter of up to 3.5 cm, are considered as one of the strongest candidates for the next generation of high field power applications and magnets. In this paper, we present a full 3D FEM model for their monolayer and bilayer CORC cables made with up to three and six superconducting tapes respectively, disclosing the full curve of AC losses for the monolayer cable at magnetic fields beyond 60 mT, and the actual distribution of current density along and across the thickness of the superconducting tapes in both designs. The model is based on the so-called H-formulation, allowing to incorporate the true three-dimensionality of the tapes without recurring to 2D thin-film approaches where non-physical surface currents that do not follow the celebrated Bean's model for type-II superconductors appear. Likewise, good agreement with the experimentally measured AC-losses for the monolayer and bilayer cable have been obtained, with all the details of the model disclosed in this paper.

Recent Progress in Conjugated Conducting and Semiconducting Polymers for Energy Devices

Advanced conductors (such as conducting and semiconducting polymers) are vital building blocks for modern technologies and biocompatible devices as faster computing and smaller device sizes are demanded. Conjugated conducting and semiconducting polymers (including poly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI), polythiophene (PTh), and polypyrrole (PPy)) provide the mechanical flexibility required for the next generation of energy and electronic devices. Electrical conductivity, ionic conductivity, and optoelectronic characteristics of advanced conductors are governed by their texture and constituent nanostructures. Thus, precise textural and nanostructural engineering of advanced conjugated conducting and semiconducting polymers provide an outstanding pathway to facilitate their adoption in various technological applications, including but not limited to energy storage and harvesting devices, flexible optoelectronics, bio-functional materials, and wearable electronics. This review article focuses on the basic interconnection among the nanostructure and the characteristics of conjugated conducting and semiconducting polymers. In addition, the application of conjugated conducting and semiconducting polymers in flexible energy devices and the resulting state-of-the-art device performance will be covered.

3D Modelling and Validation of the Optimal Pitch in Commercial CORC Cables

Conductor on a rounded core (CORC®) cables with current densities beyond 300 A/mm-2 at 4.2 K, and a capacity to retain around 90 % of critical current after bending to a diameter of 3.5 cm, make them a strong candidate for high field power applications and magnets. In this paper, we present a full 3D-FEM model based upon the so-called H-formulation for commercial CORC® cables manufactured by Advanced Conductor Technologies LLC. The model presented consists of tapes ranging from 1 up to 3 SuperPower 4mm-width tapes in 1 single layer and at multiple pitch angles. By varying the twist pitch, local electromagnetic characteristics such as the current density distribution along the length and width are visualized. Measurements of macroscopical quantities such as AC-losses are disclosed in comparison with available experimental measurements. We particularly focused on the influence of the twist pitch by comparing the efficiency and performance of multiple cables, critically assessing the optimal twist pitch angle.

Argyrodite-type advanced lithium conductors and transport mechanisms beyond paddle-wheel effect

Development of next-generation solid-state Li-ion batteries requires not only electrolytes with high room-temperature (RT) ionic conductivities but also a fundamental understanding of the ionic transport in solids. In spite of considerable work, only a few lithium conductors are known with the highest RT ionic conductivities ~ 0.01 S/cm and the lowest activation energies ~0.2 eV. New design strategy and novel ionic conduction mechanism are needed to expand the pool of high-performance lithium conductors as well as achieve even higher RT ionic conductivities. Here, we theoretically show that lithium conductors with RT ionic conductivity over 0.1 S/cm and low activation energies ~ 0.1 eV can be achieved by incorporating cluster-dynamics into an argyrodite structure. The extraordinary superionic metrics are supported by conduction mechanism characterized as a relay between local and long-range ionic diffusions, as well as correlational dynamics beyond the paddle-wheel effect.

Linking profiles of pathway activation with clinical motor improvements – A retrospective computational study

Background: Deep brain stimulation (DBS) is an established therapy for patients with Parkinson’s disease. In silico computer models for DBS hold the potential to inform a selection of stimulation parameters. In recent years, the focus has shifted towards DBS-induced firing in myelinated axons, deemed particularly relevant for the external modulation of neural activity.Objective: The aim of this project was to investigate correlations between patient-specific pathway activation profiles and clinical motor improvement.Methods: We used the concept of pathway activation modeling, which incorporates advanced volume conductor models and anatomically authentic fiber trajectories to estimate DBS-induced action potential initiation in anatomically plausible pathways that traverse in close proximity to targeted nuclei. We applied the method on two retrospective datasets of DBS patients, whose clinical improvement had been evaluated according to the motor part of the Unified Parkinson’s Disease Rating Scale. Based on differences in outcome and activation levels for intrapatient DBS protocols in a training cohort, we derived a pathway activation profile that theoretically induces a complete alleviation of symptoms described by UPDRS-III. The profile was further enhanced by analyzing the importance of matching activation levels for individual pathways.Results: The obtained profile emphasized the importance of activation in pathways descending from the motor-relevant cortical regions as well as the pallidothalamic pathways. The degree of similarity of patient-specific profiles to the optimal profile significantly correlated with clinical motor improvement in a test cohort.Conclusion: Pathway activation modeling has a translational utility in the context of motor symptom alleviation in Parkinson’s patients treated with DBS.

High-density low-loss millimeter-wave package interconnects with the impact of dielectric-material surface roughness

Heterogeneous package integration and chiplet approaches are the key technology to enable next-generation high performance small form-factor packages for emerging applications. Millimeter-wave packaging for fifth-generation and upcoming sixth-generation platforms also need to meet the high-density low signal-loss interconnect specifications utilizing advanced conductor and dielectric materials. This article presents the comparison of the liquid-based photoimageable dielectric (PID) and dry-film dielectric materials in terms of interconnect path losses that are critical in mm-wave frequency bands. The conductor loss being more dominant in the frequency bands and in thinner dielectric structures, we assess daisy chains and microstrip lines on 15-μm dielectric by measuring the S-parameters to quantify the impact of the surface roughness at around 28 GHz. Measured results from the daisy chain and microstrip line structures exhibit that the smooth surface of the liquid-based PID (3 nm) leads to 8%–32% lower signal loss in the dB scale than the 325-nm rough dry-film dielectric. The study provides comprehensive experimental results that the different material forms with various surface roughness largely impact the package-level interconnect loss.

Rheological conductor from liquid metal-polymer composites

<h2>Summary</h2> Advanced conductors are indispensable circuit elements in modern electronics with unique responses to environmental variations. This work successfully introduces the intriguing polymer relaxation into conductive materials and creates a special rheological conductor (RhC) from liquid metal (LM)-polymer composites. The electrical transition temperatures of RhC are found to be highly consistent with polymer rheological transition temperatures (T_g and T_f). Similar to the time-temperature superposition of polymers, a master curve can be constructed to effectively predict the conductivity of RhC. Further polymer rheological experiments and theoretical analysis successfully demonstrate the relationship between conductance and polymer chain relaxation. The RhC could realize several orders of magnitude change in resistance via temperature/time regulation. The polymer chain dynamics provide multiple resistive responses of RhC to temperature, time, and voltage that are remarkably different from traditional conductors. This work pioneers a new route to re-consider flexible conductors and provides diverse applications in high-tech devices.

Advanced Electrical Conductors: An Overview and Prospects of Metal Nanocomposite and Nanocarbon Based Conductors

Advanced electrical conductors that outperform copper and aluminum can revolutionize our lives by enabling billions of dollars in energy savings and facilitating a transition to an electric mobility future. Nanocarbons (carbon nanotubes and graphene) present a unique opportunity for developing advanced conductors for electrical power, communications, electronics, and electric machines for the defense, energy, and automotive industries. Herein, the major research progress in the field of advanced nanocarbon‐based and metal–nanocarbon conductors is compiled. The benefits and drawbacks of advanced conductors are also elucidated with respect to conventional ones and their materials science, mechanical and physical properties, and characterization are discussed. Finally, several areas of future research for advanced electrical conductors are proposed.

Antifreezing Zwitterionic Hydrogel Electrolyte with High Conductivity of 12.6 mS cm−1 at −40 °C through Hydrated Lithium Ion Hopping Migration

AbstractHydrogel electrolytes have high room‐temperature conductivity and can be widely used in energy storage device. However, hydrogels suffer from the inevitable freezing of water at subzero temperatures, resulting in the diminishment of their conductivity and mechanical properties. How to achieve high conductivity without sacrificing hydrogels’ flexibility at subzero temperature is an important challenge. To address this challenge, a new type of zwitterionic polymer hydrogel (polySH) electrolytes is fabricated. The anionic and cationic counterions on the polymer chains facilitate the dissociation of LiCl. The antifreezing electrolyte can be stretched to a strain of 325% and compressed to 75% at −40 °C and possesses an outstanding conductivity of 12.6 mS cm−1 at −40 °C. A direct hopping migration mechanism of hydrated lithium‐ion through the channel of zwitterion groups is proposed. The polySH electrolyte‐based‐supercapacitor (SC) exhibits a high specific capacitance of 178 mF cm−2 at 60 °C and 134 mF cm−2 at −30 °C with a retention of 81% and 71% of the initial capacitance after 10 000 cycles, respectively. The overall merits of the electrolyte will open up a new avenue for advanced ionic conductors and energy storage device in practical applications.

Synergistically integrated phosphonated poly(pentafluorostyrene) for fuel cells.

Modern electrochemical energy conversion devices require more advanced proton conductors for their broad applications. Phosphonated polymers have been proposed as anhydrous proton conductors for fuel cells. However, the anhydride formation of phosphonic acid functional groups lowers proton conductivity and this prevents the use of phosphonated polymers in fuel cell applications. Here, we report a poly(2,3,5,6-tetrafluorostyrene-4-phosphonic acid) that does not undergo anhydride formation and thus maintains protonic conductivity above 200 °C. We use the phosphonated polymer in fuel cell electrodes with an ion-pair coordinated membrane in a membrane electrode assembly. This synergistically integrated fuel cell reached peak power densities of 1,130 mW cm-2 at 160 °C and 1,740 mW cm-2 at 240 °C under H2/O2 conditions, substantially outperforming polybenzimidazole- and metal phosphate-based fuel cells. Our result indicates a pathway towards using phosphonated polymers in high-performance fuel cells under hot and dry operating conditions.

Calculation the current carrying capacity of the new generation overhead lines conductors

Currently, there is an increase in power flows along power lines. An important task for the development of the power grid complex is to increase the current-carrying capacity of existing power lines. The use of advanced conductors has become a successful technical solution for this purpose. "New generation conductors" are modern conductors that have advanced mechanical and electrical properties and characteristics. Thus, it has become important to have information about the maximum operation temperature and current limits of the overhead line with new conductors. The approximate current-carrying capacity in Amperes is the value of current at which the conductor temperature reaches its maximum permissible value. It determines the maximum current load of overhead power lines. For traditional steelaluminum conductors, there are several methodological approaches to determining the maximum current load. This fact complicates the definition of an approach to calculating the current carrying capacity for advanced conductors. Nevertheless, the general basis of all methodological approaches is the thermal balance of the conductor. The purpose of this article is to assess the possibility of adapting the method of calculating the approximate currentcarrying capacity of traditional conductors to the calculation of advanced conductors. The article deals with advanced conductors of various brands of comparable cross-section with the classic ACSR 240/39. This work provides information about the selected conductors, their characteristics and design features. The paper shows a mathematical model for calculating the approximate current-carrying capacity of a conductor and shows calculating results for selected conductors. According to the results of analysis and calculations, the adaptation of the presented mathematical model is possible if we refine its parameters and coefficients.

Nanoionics - the Developing Informative System. Part. 1. Stages of Formation and Modern State of Nanoionics in Russia

The critical review of stages of formation, development, and modern state of nanoionics in Russia and in the world is presented. The nanoionics is considered as the developing information system; its history is analyzed for the first time in terms of the dynamic theory of information and strategic innovative management. The history stages of beginnings and development of an applied and theoretical nanoionics in Russia are considered in this part of the review. In the main, the results of IMT RAS where researches were carried out for expansion of the nanoionics borders in new directions are analyzed. Results of development of new directions, such as dynamic theory of fast ionic transport (FIT) at a nanoscale (structure-dynamic approach of nanoionics, SDA), and nanoionics of advanced superionic conductors (AdSICs) are presented in more detail. Potential of these directions in breakthrough technologies is discussed.

Copper–Carbon Nanotube Composites Enabled by Electrospinning for Advanced Conductors

The power losses associated with the electrical resistance of copper (Cu) have generated considerable interest in the development of advanced conductors that incorporate carbon nanotubes (CNTs) int...

Recent Progress in the Development of CORC Cable-In-Conduit Conductors

In recent years, three unique Re BCO-CORC CICC samples with six-around-one cable layout were developed as technology demonstrators at CERN in collaboration with Advanced Conductor Technologies. The tests of these conductors at low temperature in external magnetic field yielded very promising results, but also showed several issues requiring improvement. A new 2.8 m long CORC CICC has been prepared to replace a degraded sample. The voids between CORC strands in the new sample are filled with solder alloy to provide increased mechanical support to the strands, however, this yielded an additional set of new challenges. The conductor has a design critical current of 100 kA at 10 T and 4.5 K and is designed specifically for high-current bus-bars and large detector-type magnets. It therefore features a copper jacket and practical conduction cooling via a cooling line embedded in the jacket.

Universal dynamic response in polycrystals of advanced superionic conductors

The work develops the material science of advanced superionic conductors (AdSICs). The AdSICs have been distinguished by the authors as a new class of solid-state ionic conductors due to the best ion-transport properties and their special crystal structure that is close to optimum for fast ion transport (FIT). Structure descriptors, a new geometry of 3D close packing of FIT tunnels inside the unit cell, and the distinctive properties of grain boundaries (GBs) in AdSICs have been revealed. On this structural basis and a recently developed theory of ion transport on a nanoscale (“structure-dynamic approach of nanoionics,” SDA), the absence of Jonsher’s universal dynamic response (UDR) in polycrystalline AdSICs has been explained. In solid-state ionic conductors, UDR holds in a frequency (ω) range depending on heights (η) and heights difference (Δη) of potential barriers which mobile ions overcome in a non-uniform crystal potential landscape. In polycrystalline AdSICs, η is not above 0.2 eV and Δη ≤ ~ 0.1 eV; therefore, the SDA indicates the response to external electric excitations has an ohmic character, i.e., does not depend on ω. The important role of processes of structural self-organization and the formation of low-energy coherent GBs in AdSICs is emphasized. It is concluded that a deeper understanding of the structure and properties of AdSICs can serve as a guide for searching and designing new materials/devices with FIT.

Introduction of the next generation of CORC® wires with engineering current density exceeding 650 A mm−2 at 12 T based on SuperPower’s ReBCO tapes containing substrates of 25 μm thickness

Next generation particle accelerators and fusion machines will greatly benefit from the development of low-inductance magnets capable of generating magnetic fields in excess of 16 T. Such magnets require high-temperature superconductors capable of carrying very high currents exceeding 5 kA at current densities of 400–600 A mm−2, such as Conductor on Round Core (CORC®) cables and wires wound from RE-Ba2Ca3O7-δ (ReBCO, Re = rare earth) coated conductor tapes. CORC® wires containing ReBCO tapes with 30 μm thick Hastelloy® substrates have previously been demonstrated as a viable high-field magnet conductor that can be produced at long lengths. Further improvement of the performance and flexibility of CORC® wires would benefit from the development of ReBCO tapes with even thinner substrates. SuperPower Inc. recently demonstrated ReBCO tapes based on 25 μm thick Hastelloy® substrates that allow the development of thinner and more flexible CORC® wires that meet the stringent performance requirements of high-field magnets. Several tapes containing 25 μm thick substrates were produced and analyzed, exhibiting critical current and cabling performance in-line with the current production level tapes with 30–50 μm thick substrates. Tape critical current was measured at 4.2 K and applied magnetic fields up to 31.2 T. Several CORC® wires incorporating these tapes were manufactured by Advanced Conductor Technologies using similar winding procedures that previously resulted in high-quality magnet-grade CORC® wires based on tapes with 30 μm thick substrates. The CORC® wires were tested in an applied magnetic field up to 12 T after bending to a 63 mm diameter. A critical current as high as 6231 A (12 T, 4.2 K) was measured with an engineering current density (Je) of 678 A mm−2, which extrapolates to over 450 A mm−2 at 20 T and is the highest current density reported in a CORC® conductor to date. The combination of ReBCO tapes produced using 25 μm thick substrates and the ability to wind them into long-length, high-quality CORC® magnet wires brings the development of low-inductance accelerator and fusion magnets that operate at magnetic fields exceeding 20 T closer to fruition.

Carbon Nanotube Coated Conductors

A novel approach based on conventional solution-coating and wire-drawing processes has been employed for the production of carbon nanotube (CNT) coated conductors. The solution process employs a mesoscopic building block, a CNT fibril dispersion formed in acid from forest-grown, long-length multiwall CNTs, to help bridge the transition from nanomaterials to thick, highly aligned technical coatings. The coatings are formed onto a roughened copper wire former through dip-coating. The roughened surface provides for mechanical attachment between the CNT coating and copper wire core that allows for the composite to be wire-drawn while wet to further shape, densify, and align the CNT coating. The wet chemistry approach offered a facile integration of different CNT and dopant types in the CNT coatings. For the specific process described here, it was observed that the CNT coatings were simultaneously doped with acid and copper nanoparticles. Coated wires were produced with conductivities on par with copper but in an engineered material that is lighter than the pure metal analogue. Dense coatings up to 90 μm in thickness were made that comprised up to 60% of the wire cross-sectional area and enabled composite densities to dip below half that of copper. The CNT coated wires had overall resistivities in the range 2.1–5 μΩ·cm, with specific conductivities relative to copper as high as 108%. The ubiquitous nature of the solution coating and conventional wire drawing processes may enable a novel approach to the light-weighting of advanced conductors for a broad range of applications.

Evaluation Study of Potential Use of Advanced Conductors in Transmission Line Projects

Transmission networks recently faced new technical and economic challenges. The direct use of advanced technologies and modern methods could solve these issues. This paper discusses the potential application of straightforward technology such as high-temperature low-sag conductors (HTLScs) as an additional measure for the protection and effective operation of overhead power lines. An evaluation was conducted to determine an approach for selecting the cross-sectional area and type of conductor with respect to a fault current limitation. It showed the potential benefits of using HTLScs based on an assessment of the throughput capacity and up-front capital costs. A case study considered two scenarios: the construction of a new power line and reconductoring of the existing one. The data for a real project with two overhead power lines were used. The obtained results are analyzed and discussed in detail in this paper.

Bending of CORC® cables and wires: finite element parametric study and experimental validation

A conductor on round core (CORC®) cable is composed of several layers of helically wound high-temperature superconducting (HTS) tapes on a round core with the winding direction reversed in each successive layer. The cable is flexible but the flexibility is limited by the critical strain value causing breakage of the HTS layer when this strain level is exceeded. The cables for magnets in fusion reactors experience large mechanical and electromagnetic loads. These loads arise from the cabling, coil manufacturing, cooling, and magnet operation. In order to optimize the manufacture and operating conditions, the mechanical behavior of CORC® cables must be understood for the different relevant loading conditions. The cable configuration with many contact interactions between tapes and the non-linear behavior of the materials during the production and operating conditions makes the modeling challenging. Detailed finite element (FE) modeling is required to account for these complexities. The FE modeling allows an accurate calculation of the stress–strain state (SSS) of the cable components under various loads and avoids time-consuming large-scale experimental optimization studies. This work presents a detailed FE modeling of the 3D SSS in a CORC® wire under bending load. The elastic–plastic properties of the individual tape composite materials and its temperature dependence are taken into account. The FE model is experimentally validated by a multilayer CORC® bending test performed by Advanced Conductor Technologies LLC. A critical intrinsic tensile strain value of 0.45% is taken as the threshold where the individual tape performance becomes irreversibly degraded. The proposed FE model describes the bending test of the CORC® wire adequately and thus can be used to study other types of loads. A parametric study is ongoing with dependent variables to pursue a further optimization of CORC® cables and wires for various applications.