Monofilament Wire Research Articles

The Structural Examination of Fe/(Cu/Nb)/MgB2 Multifilament Wires During Cold Forming Process

In this study, we have successfully produced a Fe-sheathed 6+1 multifilament wire using Cu/Nb/MgB2 monocore wires. The mono filament wire was prepared using Mg+2B powder mixture by powder-in-tube method without any intermediate heat treatment. The powder mixture of the amorphous nano boron (PVZ Nano Boron, purity of 98.5%, particle sizes < 250 nm) and high purity Mg powder (PVZ Mg, purity of 99%, particle size 74µm) were used. The multifilament wire was produced using groove rolling and cold drawing machines. The geometrical form of the filaments was examined using wire pieces taken from the wire at different steps throughout the production process. Finally, the multifilament wires produced in two different diameters of 1.02 mm and 0.82 mm were investigated in terms of filament uniformity, crack formation, surface roughness, and electrical transport properties. The structural examination was done on Nb filaments after the Fe and Cu sheaths were etched using HCl and HNO3 solution. The I – V measurements of the multifilament wires heat treated at 650 °C for 15, 30, 45, 60, and 240 minutes, and 700 °C for 60 minutes were carried out for the applied current up to 1 A at 25 K under various external magnetic field.

Parametric study on a resilient hybrid steel-shape memory alloy yielding damper

A critical factor obstructing structural resilience is residual deformation after a damaging event. The search for a solution for removing residual deformation has led to the consideration of Shape Memory Alloys (SMAs) that can undergo large deformations and return to their original undeformed shape. This study focuses on an innovative hybrid yielding steel-SMA damper that uses monofilament wire loops. Because of numerous design parameters that affect the performance of this hybrid damper, this research aims to carry out a parametric study to optimize the damper’s performance. The study was conducted at the device level as well as a structural level. At the device level, the key design parameters, including SMA to steel ratio, max imposed strain, and the length of the elements, were evaluated. At the same time, the damper’s effect on the seismic performance of low, mid, and high-rise structures was investigated at the structural-level study. In the end, the results showed that using the damper in strong ground motions successfully reduced the maximum residual drift up to 71%, 97%, and 92% for low, mid, and high-rise structures, respectively. Therefore, it was concluded that the damper could add the self-centering ability to hysteretic dampers while maintaining satisfactory energy dissipation performance. Furthermore, some of the advantages claimed by the developers, including versatility in design and performance, adequate load resistance, and stable behavior, were also confirmed in this study.

Mechanical simulation study of reapproximated sternum rigidity comparing sternal fixation devices.

A reliable sternal fixation is one of the most basic parts of cardiac surgery requiring sternotomy for preventing wound complications and promoting early recovery. Although various products have been released to the markets, the characteristics of each device are still unclear. A simulation study was conducted to compare the properties of two sternal fixation device: a commonly used monofilament stainless-steel wire and a newly designed cable comprised of several titanium alloys strands. Sternum models made of monomer casting nylon were tied with each material and displaced in longitudinal, antero-posterior, and horizontal directions. Resistance against each directional external force was measured and compared. The titanium cable showed a higher resistance to every directional displacement since slight deviations and a twofold higher maximum strength than the stainless wire. An in vitro simulation study revealed the titanium cable system provide stronger sternum fixation than stainless-steel wire.

Preparation of a small-size superconducting joint for C-doped 30-filament MgB2 wires

A preparation method of a small-size MgB2 superconducting joint with 2.0 mm diameter for C-doped 30-filament MgB2 wires is presented in this paper. Herein, an unreacted in situ C-doped monofilament wire was utilized as the connecting structure, since it contains a low quantity of dense precursor which needs less pressure during fabrication, avoiding distortion of the multifilament in the parent wires, as shown in SEM images. After heat treatment, the formed C-doped MgB2 bulk with small volume in the joint has the ability to release heat quickly, resulting in good stability. The morphology of the joint proved the MgB2–MgB2 interface between the monofilament and 30-filament wire had been successfully connected. The joint sintered at 600 °C for 2 h shows an apparent superconducting transition with T c-on = 33.49 K and has negligible resistance below 30.56 K as depicted in the R–T curve. It also has approximately 40% Jc value of the parent 30-filament wire, at 4.2 K in 3 T.

Is Nice knot suture comparable to wire for cerclage fixation? A biomechanical performance study

Cerclage fixation is a known orthopedic technique shown to be beneficial for circumferential augmentation when screw fixation cannot be used or is undesirable. However, ongoing advances in suture materials and knot techniques exist, and there is a paucity of evidence existing which evaluates comparisons between the two. The objective of this study was to investigate the strength and durability of cerclage fixation between the Nice knot suture technique and monofilament wire. Static displacement over time and compression load testing were analyzed. Compression testing was conducted with the Jamar Hydraulic Hand Dynamometer. Distraction testing was conducted using the Instron test system with its associated program. The Nice knot was tied using number 2 and number 5 FiberWire (Arthrex) and compared to monofilament wire. Clinical failure (displacement of 10 mm), absolute failure (opening of the knot or material failure), maximum compression achieved, and steady state compression maintained were the outcomes of interest. Double-stranded monofilament wire produces maximum consistent compression of 90 kg, followed by single-stranded monofilament wire (60 kg). Number 5 FiberWire has a higher maximum compression load than number 2 FiberWire (50 kg vs. 22 kg), but it is lower than that of the double-stranded monofilament wire constructs. When compared to the single-stranded monofilament construct, the number 5 FiberWire Nice knot is comparable (P < .05). Average steady state compression achieved after 10 minutes of resting showed double-stranded monofilament wire to be 65 kg compared to single- stranded monofilament wire at 42 kg, which when, compared to suture, number 5 FiberWire measured at 15 kg and number 2 FiberWire at 8 kg. Average tension results from Instron distraction testing showed the double-stranded monofilament wire construct was able to withstand greater forces up to a displacement of 6 mm, after which the number 5 FiberWire Nice knot was stiffer. Number 5 FiberWire shows the most linear tension relationship, revealing it more efficiently withstands elastic forces. Load to failure was higher in the number 5 FiberWire Nice knot construct than that in both the monofilament wire constructs. The modes of failure for the Nice knot were always at the knot suture interface rather than at the knot. We propose this suture technique to be a viable alternative method for cerclaging to fix upper limb long-bone fractures.

Effect of magnetic sheath on filament AC losses and current distribution in MgB2 superconducting wires: numerical analysis

Finite element method (FEM) analysis is employed to study and compare AC losses in a wide frequency range in two MgB2 superconducting wires in self-field and in the presence of external AC field. The modelled wires, of the same external dimensions, are mono- and 36-superconducting filaments embedded in either magnetic Monel or a nonmagnetic metallic wire sheath. We demonstrate that in a multifilamentary wire in self-field the Monel sheath serves as a ‘pole piece’ at the filament outer surface and alters local magnetic fields, current flow and AC losses distribution within the filament. In comparison with the nonmagnetic sheath with the same electrical conductivity, AC current in the wire with the magnetic sheath penetrates significantly deeper into the filaments and AC losses in the filament and in the magnetic sheath increase significantly. In contrast, the symmetry of the monofilament wire makes the current and loss distributions in the filament practically indifferent to the sheath composition. Still, losses in the magnetic sheath are much higher than in the nonmagnetic sheath due to increased flux dynamics. The application of DC current, on which the AC current is superimposed, sharply reduces the AC losses in the magnetic sheath material due to the drop in its permeability. Filament losses are also reduced in the presence of DC current, but to a much lesser extent. Results also show that in the kHz frequency range, the magnetic permeability of the sheath increases the skin effect in both the wire and filaments complex. As a result, at such frequencies, a significant portion of the current is carried by the metallic part of the wire instead of the superconductor, contributing to a further increase in losses. The analysis also shows that in the presence of external AC magnetic field, the Monel can provide magnetic shielding for inner filaments, thus reducing coupling effects between filaments. However, if magnetically saturated by the DC current, the Monel behaves quite similarly to a nonmagnetic sheath.

Enhanced-Textured-Powder Bi-2212/Ag Wire Development

A new method for preparing Bi-2212/Ag multifilament wire is being developed. Bi-2212 fine powder is homogenously mixed with nanoparticle Ag and uniaxially compressed into square-cross-section rods. The rods are assembled into a silver matrix and drawn into monofilament wire, restacked, and drawn into multifilament wire. Heat treatment studies have been conducted to optimize parameters for a non-melt heat treatment. Transport current at 77 K and microstructure measurements have been made to guide the process development.

A Tabletop Persistent-Mode, Liquid Helium-Free 1.5-T MgB2 "Finger" MRI Magnet: Construction and Operation of a Prototype Magnet.

This paper presents results of construction and operation of a persistent-mode, liquid-helium-free, small-scale prototype magnet for the development of a tabletop 1.5-T "finger" MRI system for osteoporosis screening. The prototype magnet, composed of 2 MgB2 coils, one superconducting joint, and a persistent-current switch (PCS) built from a portion of one coil, was wound with a one continuous ~80-m long unreacted and monofilament MgB2 wire and then reacted. The test magnet was charged successfully and generated the estimated target field of 1.75 T at 5 K with the proposed PCS operation. During initial persistent-mode, the field was slightly decayed due to the index dissipation of the joint; thereafter it sustained the persistent field of 1.7 T for 35 h. The test results validated the joint resistance of < 1.2 × 10-11 as well as the proposed approach involving the PCS coil circuit model.

Study on Cold-Drawing in Powder-in-Tube Process in Fabricating Silver-Sheathed (Bi,Pb)-Sr-Ca-Cu-O Tapes

Since Cu oxide superconductors have been discovered, the application for this type of superconductor especially in the form of superconducting tape to be used as electric cable to transport the electricity. The aim to this study is to analyse the manufacture of superconducting wire with superconducting pellets as its precursor. A pellet disc of High Temperature Superconducting (HTS) Bi,Pb-Sr-Ca-Cu-O has been made by using solid state method. This pellet has been prepared by mixing each of oxide powders together, and then sintered at 865°C for 90 hours. We have analysed the samples using X-Ray Diffractometer (XRD), Energy Dispersive x-ray Spectroscopy (EDS), Scanning Electron Microscopy (SEM) and also resistivity measurement to confirm its superconductivity. After confirmed the superconducting properties of the pellet, it was grinded into powder and inserted into silver tube with outer diameter of 10 mm and thickness of 1 mm. And then, drawn to make monofilament wire. It were then cut and inserted into another silver tube, and then re-drawing and rolled into multifilament tapes using Powder-in-Tube (PIT) method. The multifilament tapes was heated at 850°C for 12 hours. We confirmed its phase crystalline and superconductivity at pellet disc. However, when the pellet disc was made into wire and sintered at 850°C, it became amorphous and conductivity behaviour was decline. According to SEM analysis and resistivity measurement result, silver also penetrated inside the sample region of multifilament wire.

Accuracy of a Single Tunnel Technique for Reconstruction of the Interosseous Talocalcaneal Ligament

Category: Ankle Introduction/Purpose: Numerous reconstructive techniques to address subtalar joint instability have been described. Interest has focused on direct anatomic repair of the interosseous talocalcaneal ligament (ITCL) with tendon autograft, which is passed through osseous tunnels of the talus and calcaneus within the native anatomic boundaries of the compromised ITCL. To our knowledge, the technique employed to accurately place a guidewire and create a percutaneously developed tunnel through the anatomical footprint of the ITCL to restore it has not been described. The purpose of this study was to confirm that an osseous tunnel could be positioned within the ligamentous footprints accurately and safely, to define anatomic landmarks that can be used as reference points to reproduce an accurate tunnel, and assess the structures at risk during percutaneous reconstruction. Methods: Ten fresh cadaveric below-knee specimens were utilized. Under fluoroscopy, an anterior cruciate ligament guide was utilized to place a drill tunnel from the plantar lateral aspect of the calcaneus, across the sinus tarsi, and through the dorsal medial talus. The monofilament wire was passed through this tunnel to serve as a simulated model for cortical button fixation within the footprint of the ITCL. The first five specimens (group 1) were dissected; structures at risk and wire distance to the center of the ITCL were recorded. The procedure was then performed on the second set of five specimens (group 2) to assess for improvement in our technique. Results: The mean distances from the wire to the ITCL on the calcaneus and talus were 2.92 mm and 4.04 mm, respectively. Mean distances from the wire to ITCL on the calcaneus in groups 1 and 2 were 4.04 mm and 1.80 mm, respectively (p = .04). Mean distances from the wire to ITCL on the talus in groups 1 and 2 were 6.23 mm and 1.84 mm, respectively (p = .08). Violated structures included the tibialis anterior tendon in one specimen, and the most dorsal aspect of the talar head cartilage in 2 specimens. Conclusion: Under fluoroscopic guidance, and with minimal technique experience, a tunnel can be directed across the ITCL footprints accurately and safely. In our last five specimens, we were within 2 mm of the ITCL center, and well within the typical 8.5 mm average ITCL width. In our practice, we have reconstructed the ITCL with a cortical button fixation device using this technique and found it to be efficient and effective.

Monofilament Wire Silver Sheathed Bi,Pb-Sr-Ca-Cu-O Prepared by Four-Pass Rolling and Repeated Heating Process

A four-step process was proposed to manufacture monofilament wire Bi,Pb-Sr-Ca-Cu-O using silver (Ag) sheath fabricated by Powder-In-Tube (PIT) method in which the thickness of wire were subjected to rolling from 10 mm Ø to2 mm Ø and heated at temperature of 860 °C in 24 h. The effect of the rolling and heating process on the properties of four samples Ag-sheathed Bi,Pb-Sr-Ca-Cu-O wires in each step were studied. In x-ray diffraction (XRD) patterns of monofilament wire fabricated by PIT method in which the repeated heating process involved in rolling can alter the precursor phase. At a first and second deformation process, samples sintered at 860 °C in 24 h still contained the constituent elements of precursor powders. Third deformation step were shown to have superconducting phase Bi,Pb-Sr-Ca-Cu-O 2212. According to resistivity measurement analysis, rolling and repeated heating process were shown to have a critical effect on superconductivity. First, second and fourth rolling were found to have no superconductivity, while third rolling were found to exhibit superconductivity of which its value of critical temperature monofilament wire (Tc,onset) was 90 K. Furthermore, according to Scanning Electron Microscopy (SEM) analysis, the rolling and repeated heating process were observed to have important effect on morphology of samples. Wire superconductors on first and second rolling were shown to have crack and high porosity, but after third rolling the crack and porosity were diminished. Overall the deformation process have yielded promising results particularly when the superconducting phase Bi,Pb-Sr-Ca-Cu-O 2212 were found optimum in third deformation process.

The Ecological Balance of the Fish Community in an Aging Reservoir

Reservoir fishes contribute significantly to freshwater fish resources in Nigeria. The composition, size variation and relative abundance of fishes in Opa reservoir, Southwest Nigeria, were investigated to establish the ecological balance of the various trophic groups of fishes in the reservoir. The study was carried out in view of recent reports on the decline in the quality and quantity of water in the aging reservoir. Fishes were collected from the reservoir monthly for twelve months using monofilament gill nets and wire cages. The fishes were identified to species level and the ecological balance of the fish community was calculated as a ratio of the forage to the carnivore groups by number and by weight. Data were subjected to statistical analysis using the Stata 13 software. 1915 fishes belonging to 17 species and 10 families were collected from the reservoir. The fish composition was dominated by the family cichlidae, with its 7 species accounting for 89.8% of the total catch. There were 2 species of clariidae, which made 6.2% of the total catch. The ecological balance of the fish community was 3.4 (by number) and 6.2 (by weight). The result obtained revealed that the fish community in the reservoir is ecologically balanced.Comparative analysis of the fish composition of the Opa reservoir with reports from other reservoirs in Southwest Nigeria showed that the reservoir has more fish species than most of the other reservoirs around. The study concludes that the reservoir still supports a rich, diverse and ecologically balanced fish community. It is recommended that the management of these fish resources should be key in the holistic management of the aging Opa reservoir.

Fixation of Trochanteric Fragments in Cementless Bipolar Hemiarthroplasty of Unstable Intertrochanteric Fracture: Cerclage Wiring.

PurposeBipolar hemiarthroplasty (HA) is an option for the treatment of unstable intertrochanteric fracture in elderly patients. There is a raising concern regarding cable-grip related complications for the fixation of trochanteric fragments. Therefore, the aim of this study was to evaluate outcome of cementless HA with fixation for the trochanteric fragments using monofilament wires in unstable intertrochanteric fracture.Materials and MethodsWe reviewed 92 cementless bipolar HAs using a grit-blasted long stem design for unstable intertrochanteric fractures in 91 elderly patients with a mean age of 81.7 years. During the arthroplasty, trochanteric fracture fragments were fixed using 1 or 2 vertical wires and transverse wires. We evaluated the clinical outcomes such as abductor power, ambulatory ability and wire-related complications, and radiologic outcomes including the union of the trochanteric fragment and subsidence of stem.ResultsSixty-two patients were followed for a minimum of 2 years (mean, 59 months) postoperatively. The mean abductor power and Koval category was 4.1 (range, 3 to 5) and 4.6 (range, 1 to 6). The wire was broken in 3 hips (4.8%) and the nonunion of the greater trochanter occurred in 1 hips (1.6%). Two stems subsided by 3 mm and 8 mm, respectively, during postoperative 6 weeks, after which the subsidence was not progressive.ConclusionCerclage wiring of the trochanter using monofilament wire leads to acceptable outcome in cementless HA for senile patients with unstable intertrochanteric fracture. Cerclage wiring using a monofilament wire is recommended for the fixation of trochanteric fragments.

Is suture comparable to wire for cerclage fixation? A biomechanical analysis.

Cerclage wire is the current standard for circumferential bone fixation. Advances in technology have improved modern sutures, allowing for expanded utility and broader application. The present study compared the strength and durability of cerclage fixation between modern suture materials and monofilament wire. The Surgeon's Knot, the Nice Knot and the Modified Nice Knot, were each tied using three separate suture materials: no. 2 FiberWire (Arthrex, Naples, FL, USA), no. 2 Ultrabraid (Smith & Nephew, Andover, MA, USA) and no. 5 Ethibond (Johnson & Johnson, Somerville, NJ, USA). These sutures were compared with monofilament wire. Sutures were secured around a fixed diameter using three additional half hitches, whereas a 1.2-mm (18 gauge) stainless steel monofilament wire was used for comparison. One fellow and one orthopaedic surgery resident each tied five trials with every knot/material combination. Samples were subjected to cyclic loading and quasi-static load testing. Respectively, cyclic displacement over time and load to failure were analyzed. Clinical failure (3 mm of cyclic displacement) and absolute failure (opening of the knot or material failure) were the outcomes of interest. During cyclic loading, Ethibond displaced significantly less over time compared to monofilament wire (p < 0.003), whereas FiberWire showed no significant difference. Ultrabraid also behaved similar to wire, except displacing significantly more than wire only with the Surgeon's Knot (p = 0.02). During load to failure, Ethibond and FiberWire failed at significantly greater loads than monofilament wire (p < 0.001), whereas Ultrabraid performed similar to wire. Knot types did not appear to impact the results. High-performance sutures achieve superior results in biomechanical testing under cyclic and quasi-static load compared to monofilament wire, suggesting that they provide an alternative to wire for cerclage fixation with select clinical application. Biomechanical security of suture cerclage is dependent on suture material, although it is not altered significantly by choice of knot. An ex-vivo study with clinical application would further reinforce whether suture cerclage offers a valid alternative to wire cerclage.

Comparison of microstructure, second phases and texture formation during melt processing of Bi-2212 mono- and multifilament wires

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 identical Bi-2212 precursor. The monofilament tomograms show in unprecedented detail how the distributed porosity agglomerates well before Bi-2212 melting decomposition to form lenticular voids that completely interrupt the filament connectivity along the wire axis. When the Bi-2212 phase completely melts connectivity in the axial wire direction is established via the changes in the void morphology from the lenticular voids to bubbles that remain when Bi-2212 crystallises out of the melt. By measuring the attenuation of the monochromatic x-ray beam, the associated Bi-2212 mass density changes have been monitored during the entire heat cycle. The XRD results reveal that the wire architecture can have a strong influence on the phase evolution during the melt processing heat treatment affecting the reversibility of Bi-2212 melting decomposition reaction. A strong Bi-2212 texturing is only achieved in the multifilament wire, while in the monofilament wire Bi-2212 crystallites grow with nearly random orientation.

Ilium-Femoral Suture Technique Using Wire of Polydioxanone for Hip Joint Stabilization in a Dog with Traumatic Hip Dislocation

Background: The hip dislocation is the most common traumatic dislocation in dogs. Surgical treatment has better results,but there is still no consensus on the best technique. This study aims to report a case of traumatic hip dislocation in a dog, inwhich case it was decided by extra-articular stabilization, using absorbable monofilament wire of Polydioxanone, throughimplementing the Ilium-Femoral Suture Technique. This surgical thread is composed of a poly dioxanone polymer anddiffers from polyglycolic acid and polyglactin 910 by being a monofilament. The surgical technique consists of making atunnel in the ileum body, in dorsolateral-ventromedial direction and another in the greater trochanter, in the caudally skull.The stabilization is achieved using one or more sutures standard “8”, passing through the two tunnels. The vast majorityof published works on the subject, reports the use of non-absorbable wires, such as surgical nylon or polyamide in themaking of this type of suture, justifying the relevance of this report.Case: A Belgian Malinois breed dog of 2.5-year-old, female, was treated at a private clinic in the city of Porto Alegre,RS, Brazil, with trauma history by trampling. The patient had lack of member support and maintenance of the same inexternal rotation. General anesthesia of the patient, with 5 mg.kg-1 of Propofol (Propovan®), preceded by the application ofpreanesthetic medication with 0.05 mg.kg-1 of acepromazine 0.2% (Acepran®), 0.2 mg.kg-1 of Methadone Hydrochloride5% (Mytedom®) and 3 mg.kg-1 of Ketamine hydrochloride 10% (Quetamina®), allowed the detailed clinical examinationand proper positioning of the patient to perform the radiographic examination. The same show total loss of contact betweenthe articular surface of the acetabulum and the femoral head rights, this being displaced skull-dorsally in relation to theacetabulum. Radiographs were compatible with dislocated hip-skull right dorsal. As an alternative to immediate treatment,we opted for the closed reduction of dislocation and making a Ehmer sling for emergency stabilization and, about 24 hafter, extra-articular surgical stabilization by implementing the Ilium-Femoral suture technique. According to the patient’sauthor reports, the support of the member took place on the 3rd day after surgery. An X-ray control, performed 12 weeksafter the procedure, showed moderate atrophy of the muscles of the right hind limb and mild periosteal reaction in theipsilateral ileum body region.Discussion: The diagnosis of hip traumatic cranio-dorsal dislocation is based on patient history, clinical signs, full orthopedicexamination and radiographic findings. The present patient case was an automobile trampling victim, however, the clinicalsigns presented as lack of support from the member and lack of external rotation may be associated with other disorders ordiseases affecting the musculoskeletal system. The ease of palpation and the elevation of the greater trochanter, in relationto the ischial tuberosity and coxal and radiographs in the medial-lateral and ventral-dorsal projections made it possible toconfirm the diagnosis. To prevent further tissue damage, it was held closed reduction with the patient under general anesthesiaand using an Ehmer sling. Due to the size and the dog’s degree of activity, we opted for the surgical stabilization.Conventional cranio-lateral approach was sufficient to expose the structures without the need for magnification to displaythe ileum body. The surgical technique was simple and easy to perform and the patient remained without a sling or othertype of bandage for immobilization in the postoperative, an advantage of using this technique.Keywords: dog, extra-articular absorbable suture, traumatic hip luxation.

Conduction Cooled MgB&lt;sub&gt;2&lt;/sub&gt; Coil in Maximum Self Magnetic Flux Desity 2.3 Tesla Made with 300-Meter-long Multifilamentary MgB&lt;sub&gt;2 &lt;/sub&gt;Wire

We fabricated a 300-m-long multifilamentary MgB 2 wire as a powder in tube wire by using an in situ method. The J e values were approximately 250 A/mm 2 from 2 to 3 T at 20 K and 3 to 4 T at 15 K. These J e values were interpolated by J c values on monofilament wire because I c measurements over 100 A were difficult due to joule heat on solders. By using this 300 m wire, a coil was designed to be driven in the maximum magnetic flux density in MgB 2 filaments (B max ) over 2 T. The coil was made by using a wind-and-react method and cooled by using conduction cooling. The coil was successfully driven at 24 K and 27 K as temperatures of coil winding, and calculated B max was 2.3 T in 24 K operation. The coil I c values measured at 24 K and 27 K agreed well with the estimated values based on I c values on short-length wire. This means that the 300-m-long multifilamentary wire has sufficient longitudinal homogeneity for designing MgB 2 coils and can be used at a maximum magnetic flux density over 2 T.

Uniformity of Coronene-Added MgB &lt;sub&gt;2&lt;/sub&gt; Superconducting Wires Fabricated Using an Internal Mg Diffusion Process

We fabricated 100-m-long class-MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> superconducting wires using an internal Mg diffusion (IMD) process. Coronene was added as a carbon source to enhance the in-field critical current properties. We prepared a coil with a 4.8-cm diameter with 12 turns from a 2.6-m wire cut from the long wire. We obtained uniform critical currents (the critical current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ), the critical current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ), and engineering J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> )) at different magnetic fields and temperatures, wire structures, compositions, and microstructures of the MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer in ten short wires cut from the middle ten turns of the coil. We also took seven pieces of a monofilament wire from the IMD long wire to fabricate a seven-filament IMD MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> wire, and we found no obvious decrease in J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> when the diameter of the wires decreased from 1.06 to 0.88 mm. These results suggest that the IMD process could be used to fabricate MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> wires with a uniform structure. Coronene addition is useful for obtaining uniform composition and microstructure in the MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer because the B powder is uniformly coated with coronene for the whole wire during the annealing steps in the drawing process and the final heat treatment process. Therefore, the IMD process, together with coronene addition, is expected to fabricate MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> superconducting wires with uniform in-field critical current properties for practical large-scale applications.

Construction and Persistent-Mode Operation of MgB2 Coils in the Range 10-15 K for a 0.5-T/240-mm Cold Bore MRI Magnet.

This paper presents construction and persistent-mode operation results of MgB2 coils for a 0.5-T/240-mm cold bore MRI magnet, wind-and-react with monofilament MgB2 wire at the MIT Francis Bitter Magnet Laboratory. The magnet, of respective inner and outer diameters of 276 and 290 mm and a total height of 460 mm, has center field of 0.5 T and current density of 11 kA/cm2. To limit the continuous length of Hyper Tech supplied MgB2 monofilament wire to ≤300 m, the magnet was divided into eight series-connected coils, each equipped with a persistent current switch and a superconducting joint. We have manufactured three coil modules. Before being tested as an assembly, each coil was tested individually to ensure its capacity to carry 100-A superconducting current in the range of 10-15 K. The three coils were then assembled, connected in series, and operated as a 3-coil assembly in persistent mode at nearly 100 A in the range of 10-15 K. We present results that include: 1) construction details; 2) component performances; and 3) a 3-coil assembly performance.

Electromagnetically Assisted Densification of Copper-Sheeted in Situ MgB 2 /Cu Wires

This paper summarizes recent methods of improving critical current density of in situ Cu-sheathed MgB2 wires. These methods include using optimum heat treatment schedule, adding copper powder to the wire core and electromagnetic densification of wire core. The large part of work reported here focuses on the latter method applied to the relatively low-density MgB2/Cu wire core. The packing density of unreacted, monofilament wire core was increased by 8 % with oscillating magnetic pressure, reaching a peak value above 700 MPa as calculated by finite element modelling of the forming process. The higher density of the MgB2 core combined with copper powder addition resulted in a critical current density increase of more than fivefold in comparison to purely stoichiometric and cold-drawn-only wire.