# Production and Characterization of Cu/CNT Nanocomposites
## 2 Materials and Methods  
The copper powders were provided by Goodfellow (Goodfellow Cambridge Ltd., Huntingdon, UK), and the multiwalled carbon nanotubes, used as reinforcing material, are from Fibermax Ltd., London, UK). The outer and inner diameters and the structure of the CNTs can be seen in detail in a previous work [19]. The as-received copper powder and ultrasonicated mixtures were characterized by optical microscopy (OM) and scanning electron microscopy (SEM) electron backscattered diffraction (EBSD). Raman spectroscopy (Jobin Yvon T64000; HORIBA Scientific, Kyoto, Japan) experiments were conducted with a laser wavelength of 514 nm.  
Image analysis was performed using the software Image J (version 1.51, [PERSON], National Institutes of Health, Bethesda, MD, EUA) for particle size, length, and wide measurements. These measurements were obtained from OM images using a DM 4000 M optical microscope equipped with a Leica DFC 420 camera (Leica Microsystems, Wetzlar, Germany). An SEM (Thermo Fisher Scientific QUANTA 400 FEG SEM, Thermo Fisher Scientific, Hillsboro, OR, USA) with an EBSD detector TSL-EDAX EBSD Unit (EDAX Inc. (Ametek), Mahwah, NJ, USA) was used. Furthermore, dynamic light scattering (DLS) with a Laser Coulter LS230 (Beckman Coulter, Inc., Brea, CA, EUA) complementarily analyzed the as-received copper powder.  
Several amounts of CNTs (from 1.0 to 2.5% vol.) were added to the Cu matrix to determine the effect of the reinforcement's volume fraction in the nanocomposites' production. The dispersion and mixing were performed in one step by ultrasonication for 15 min in isopropanol. This procedure has already been adopted for other matrices such as Al and Ni to produce nanocomposites reinforced with CNTs [19; 20; 21]. These mixtures were then cold pressed to 900 MPa and sintered under vacuum for 120 min at 950 \({}^{\circ}\)C.  
The cold rolling of the sintered samples was performed at a low speed (10 rpm) until strains from 0.11 to 1.61 were achieved in a maximum of 4 more minor passes. OM, SEM, and EBSD conducted the microstructural characterization of the nanocomposites.  
EBSD has proven to be an extraordinarily advanced technique to characterize nanocomposites and deformed samples, ideal for the present work [20]. The raw EBSD data must be cleaned using TSL OIM Analysis 5.2 (EDAX Inc. (Ametek), Mahwah, NJ, USA) to avoid false results. In this sense, a grain tolerance angle of 15\({}^{\circ}\) and a minimum 2 points grain size were established before performing the different maps. The overall EBSD map inverse pole figures (IPFs), Kernel average misorientation (KAM), and grain boundary maps were elaborated as described, with conditions similar to those of previous work [20]. Furthermore, to analyze the density of the geometrically necessary dislocations (GNDs) of the samples, crucial in the deformation studies, the ATEX software (University of Lorraine, Metz, France) was used [22].  
The mechanical properties of the nanocomposites were evaluated by hardness and tensile tests. Vickers microhardness tests were performed using a load of 98 mN for a normalized time of 15 s on a Duramin-1 durometer (Duramin-1; Struers A/S, Ballerup, Denmark). The average microhardness value and respective standard deviation were calculated from 12-20 indentations performed in each sample. The tensile test was performed with a velocity of 0.2 mm/s, using Shimadzu EZ Test equipment (Shimadzu Corporation, Kyoto, Japan), and three samples of each, nanocomposite and copper matrix, were tested.