Real time in-situ pulsed magnetic field coil deformation measurements with fiber Bragg sensors

Not ye

High strength – High conductivity double-walled carbon nanotube – Copper composite wires

Double-walled carbon nanotube – copper composite macroscopic wires are prepared using a combination of spark plasma sintering and room-temperature wire drawing. The carbon content in the samples is low (0.5 vol.%). Compared to the corresponding pure copper wires, the electrical resistivity at 77 K of the composite wires is increased by only about 12% whereas their ultimate tensile strength at 293 K (560 MPa) and 77 K (710 MPa) is increased by about 10

High strength-high conductivity carbon nanotube-copper wires with bimodal grain size distribution by spark plasma sintering and wire-drawing

Copper and 1 vol% carbon nanotube-copper cylinderswith a micrometric copper grain size and either a unimodal or a bimodal grain size distribution were prepared using spark plasma sintering. The cylinders served as starting materials for room temperature wire-drawing, enabling the preparation of conducting wires with ultrafine grains. The tensile strength for the carbon nanotube-copperwires is higher than for the corresponding pure copper wires. We show that the bimodal grain size distribution favors strengthening while limiting the increase in electrical resistivity of the wires, both for pure copper and for the composites

High Strength-High Conductivity Silver Nanowire-Copper Composite Wires by Spark Plasma Sintering and Wire-Drawing for Non-Destructive Pulsed Fields

New Ag-Cu composite wires are developed for the winding of non-destructive pulsed magnets. Silver nanowires were mixed with a micrometric copper powder. Copper and 1, 5 and 10 vol. % silver-copper cylinders were prepared by spark plasma sintering. They served as starting materials for room temperature wire-drawing, enabling the preparation of conducting wires containing copper ultrafine elongated grains and silver nanowires located at the grain boundaries. The tensile strength at 293 K and 77 K for the composite wires is more than twice those for the corresponding pure copper wires. The electrical resistivity is however increased and we show that the composites containing only 1 vol. % silver offer the best compromis

High strength–high conductivity nanostructured copper wires prepared by spark plasma sintering and room-temperature severe plastic deformation

A pure copper cylinder with micrometric grains was prepared by spark plasma sintering and was wire-drawn at room temperature. The ultimate tensile strength of the conducting wires is 600 MPa at room temperature. This originates from the propagation of dislocations by an Orowan mechanism in grains smaller than 250 nm

Nanostructured 1% silver-copper composite wires with a high tensile strength and a high electrical conductivity

High-strength, high-conductivity silver-copper composite wires were prepared by powder metallurgy, spark plasma sintering and room-temperature wire-drawing. Silver nanowires were mixed with a commercial micrometric copper powder (1, 5 and 10 vol% silver). The powders were consolidated by spark plasma sintering in cylinders, which served as precursors for room temperature wire-drawing, producing samples of wires with progressively decreasing diameters. The Vickers microhardness for the wires is higher than that for the cylinders, reflecting both densification and grain refinement. Investigation of the microstructure reveals that the silver nanowires are located at the grain boundaries of ultrafine copper grains, elongated over several micrometers. The electrical resistivity and tensile strength were measured at 293 K and 77 K. The tensile strength is more than twice for the composite wires compared to the corresponding pure copper wires. Although higher tensile strengths are obtained using 5 vol% Ag, the wires containing only 1 vol% Ag offer the best combination of high strength (1100 ± 100 MPa at 77 K) and low electrical resistivity (0.50 μΩ cm). The 1 vol% Ag–Cu composite wires compare favorably with Ag–Cu alloy wires containing about 20 times more silver

Influence of alloying on the tensile strength and electrical resistivity of silver nanowire: copper composites macroscopic wires

Composite powders made up of 1 vol. %Ag nanowires (NW) dispersed in Cu were prepared and consolidated into cylinders by spark plasma sintering. One cylinder was sintered at only 400 °C resulting in a nanocomposite sample with no dissolution of the Ag NW into the Cu matrix. The second cylinder was sintered at 600 °C and the Ag NW are dissolved forming Ag/Cu alloy NW. The cylinders served as starting materials for room temperature wire-drawing, enabling the preparation of wires of decreasing diameters. The microstructure of the cylinders and the wires was investigated by electron microscopy and associated techniques. The tensile strength and electrical resistivity were measured at 293 K and 77 K. The nanocomposite and alloy wires show similar UTS values (1100 MPa at 77 K), but alloying, although spatially limited, provoked a significant increase in electrical resistivity (0.56 µΩ cm at 77 K) compared to the nanocomposite wires (0.49 µΩ cm at 77 K)

Dog-bone copper specimens prepared by one-step spark plasma sintering

Copper dog-bone specimens are prepared by one-step spark plasma sintering (SPS). For the same SPS cycle, the influence of the nature of the die (graphite or WC–Co) on the microstructure, microhardness, and tensile strength is investigated. All samples exhibit a high Vickers microhardness and high ultimate tensile strength. A numerical electro-thermal model is developed, based on experimental data inputs such as simultaneous temperature and electrical measurements at several key locations in the SPS stack, to evaluate the temperature and current distributions for both dies. Microstructural characterizations show that samples prepared using the WC–Co die exhibit a larger grain size, pointing out that it reached a higher temperature during the SPS cycle. This is confirmed by numerical simulations demonstrating that with the WC–Co die, the experimental sample temperature at the beginning of the dwell is higher than the experimental control temperature measured at the outer surface of the die. This difference is mostly ascribed to a high vertical thermal contact resistance and a higher current density flowing through the WC–Co punch/die interface. Indeed, simulations show that current density is maximal just outside the copper sample when using the WC–Co die, whereas by contrast, with the graphite die, current density tends to flow through the copper sample. These results are guidelines for the direct, one-step, preparation of complex-shaped samples by SPS which avoids waste and minimizes machinin