Ni Nanobuffer Layer Provides Light-Weight CNT/Cu Fibers with Superior

Transcription

1 Supporting Information Ni Nanobuffer Layer Provides Light-Weight CNT/Cu Fibers with Superior Robustness, Conductivity and Ampacity Jingyun Zou,, Dandan Liu, Jingna Zhao, Ligan Hou, Tong Liu, Xiaohua Zhang, * Yonghao Zhao, Yuntian T. Zhu,, * and Qingwen Li * Nano Structural Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing , China Division of Advanced Nano-Materials and Vacuum Interconnected Nanotech Workstation, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou , China Department of Materials Science & Engineering, North Carolina State University, Raleigh, NC 27695, USA xhzhang2009@sinano.ac.cn, ytzhu@ncsu.edu, qwli2007@sinano.ac.cn 1. Continuous Online Electrodeposition Figure S1. Schematic of the continuous online deposition process. The smooth graphite electrode acted as the cathodes, and a nickel plate and a copper plate was used as the anodes in the Ni plating and Cu plating process, respectively. S-1

2 2. Optimizing of the Ni Plating and Anodizing Treatment Figure S2. SEM images of the morphologies of the deposited Ni buffer layers. (a) No Ni particles were found on the 2.5-V deposited fiber, and the mass of the fiber kept almost unchanged. (b) When increasing the voltage to 5 V, a mass of Ni nanoparticles were formed on the CNT fiber. Its mass fraction was only 2.9 wt %, but it significantly improved the composite fiber s performance as discussed below. (c) After increasing the voltage to 10 V, the Ni mass fraction increased to 8.2 wt %. The effective strength of the corresponding CNT-Ni-Cu fiber also reached 800 MPa after the annealing, but its electrical conductivity was only S/m (2-μm-thick Cu layer). (d) A thick and unhomogeneous Ni layer (45.6 wt %) formed with many cracks using a 15-V voltage, and the Ni mass fraction dramatically increased to 45.6 wt %. So, 5 V is the optimized Ni plating voltage. Figure S3. Effect of the anodizing voltage on the CNT fiber s electrical performance. After being anodized by a 3-V treatment, the linear resistance of the fiber reached the minimum. So, the optimal anodization voltage is 3 V. S-2

3 3. Detailed XRD Information Table S1. Detailed XRD information Sample 2θ ( o ) (hkl) Grain Size (nm) unannealed annealed 43.3 (111) CNT-Cu 50.4 (200) (220) (311) (111) CNT-O-Cu 50.4 (200) (220) (311) (111) CNT-Ni-Cu 50.5 (200) (220) (311) Schematics of the Copper Deposition Process Figure S4. Schematics of the copper deposition process. (a) Homogeneous nucleation process for the CNT-Cu and (b) selective nucleation process for the CNT-O-Cu and CNT-Ni-Cu fibers. Cu atoms deposited randomly at the surface of the pristine fiber, but Cu atoms deposited around the oxygen-containing functional groups and Ni particles for the anodized and Ni treated fibers. S-3

4 5. Analysis of the CNT-Ni-Cu Interface Figure S5. Distribution of the C, Ni and Cu elements before (a) and after (b) the annealing. A very thin Cu layer (<500 nm) was coated in order to detect the underlying Ni atoms. Ni atoms flocked together before the annealing while they were evenly distributed after the annealing, coinciding with the conclusion that Ni atoms diffused into the Cu layer or CNT fiber. 6. Fracture Morphologies. Figure S6. Fracture morphologies of the CNT-Cu (a), CNT-O-Cu (b) and CNT-Ni-Cu (c) composite fibers. The top and bottom panels are the samples before and after the annealing. For the CNT-Cu and CNT-O-Cu fibers, long CNT fibers, with many CNT bundles being torn down were pulled out from the Cu shell before. The annealing reduced the load transfer between the core fiber and the Cu layer, making the core fiber intact after fracturing the outer layer as no CNT bundles were torn down. On the contrary, for the third sample, both the outer layer and core fiber break simultaneously due to the S-4

5 enhanced interfacial shear strength. 7. Current Density-Voltage Curves Figure S7. Typical current carrying performance of the CNT-Ni-Cu and CF-Cu fibers, both with a 2-μm thick Cu layer. The maximum current that the fibers can carry can be easily acquired. The C e and C s of the CF-Cu fiber were only A/cm 2 and A/cm 2, far below the corresponding values of the CNT-Ni-Cu fiber (1.01 and A/cm 2 ). 8. Morphologies of Fused Fibers Figure S8. Fracture morphologies of the CNT/Cu fibers burned down by giant current. For the CNT-Cu (a) and CNT-O-Cu (b) fiber, only the copper layer fused and moved long the CNT fiber, leaving an intact core CNT fiber. (c) For the CNT-Ni-Cu fiber, the CNT fiber and CNT layer burned down nearly simultaneously and one can find lots of large Cu/Ni particles that are attached on the CNT fiber surface, indicating a strong and thermally stable CNT-Ni-Cu interface. S-5

6 9. Details of the CNT Fiber Figure S9. Information of the CNT fiber. (a) The TEM image shows that the CNT fiber is composed of 2 4-walled CNTs with a diameter of 4 7 nm. (b) SEM image shows that the fiber has a diameter of 10 μm and a twisting angle of 23 o. (c) Tensile stress of the CNT fiber reaches up to 1.2 GPa. 10. Control of Cu Thickness and Fiber Density Figure S10. Control of Cu thickness and composite fiber density. (a) Deposited Cu layer thickness versus rotate speed. (b) The composite fiber density as a function of Cu thickness. 11. Effect of The Annealing Treatment S-6

7 Figure S11. Effect of the annealing treatment. The CNT-Ni-Cu fiber s conductivity varied with the annealing temperature and the optimum temperature was 300 o C. 12. Recent Progress in CNT-Cu Composite Fibers Mass density Conductivity Ampacity TCR (g/cm 3 Fraction of CNT ) ( 10 5 S/cm) ( 10 6 A/cm 2 ) ( 10-3 K -1 ) Strength (MPa) vol % \ [1; 2] 4 * 50 vol % \ \ [3] 1.87 \ 83 vol % * 69 vol % * \ \ [4] vol % * 1.84 \ \ 0.25 wt % S cm 2 /g * \ \ \ [5] vol % [6] vol % This work * The values were calculated from the relevant data mentioned in these works. Reference [1] Subramaniam, C.; Yasuda, Y.; Takeya, S.; Ata, S.; Nishizawa, A.; Futaba, D.; Yamada, T.; Hata, K., Carbon nanotube-copper exhibiting metal-like thermal conductivity and silicon-like thermal expansion for efficient cooling of electronics. Nanoscale 2014, 6 (5), [2] Subramaniam, C.; Yamada, T.; Kobashi, K.; Sekiguchi, A.; Futaba, D. N.; Yumura, M.; Hata, K., One hundred fold increase in current carrying capacity in a carbon nanotube-copper composite. Nature Communications 2013, 4, [3] Subramaniam, C.; Sekiguchi, A.; Yamada, T.; Futaba, D. N.; Hata, K., Nano-scale, planar and multi-tiered current pathways from a carbon nanotube copper composite with high conductivity, ampacity and stability. Nanoscale 2016, 8 (7), [4] Xu, G.; Zhao, J.; Li, S.; Zhang, X.; Yong, Z.; Li, Q., Continuous electrodeposition for lightweight, highly conducting and strong carbon nanotube-copper composite fibers. Nanoscale 2011, 3 (10), [5] Hannula, P.-M.; Peltonen, A.; Aromaa, J.; Janas, D.; Lundström, M.; Wilson, B. P.; Koziol, K.; Forsén, O., Carbon nanotube-copper composites by electrodeposition on carbon nanotube fibers. Carbon 2016, 107 (Supplement C), [6] Han, B.; Guo, E.; Xue, X.; Zhao, Z.; Luo, L.; Qu, H.; Niu, T.; Xu, Y.; Hou, H., Fabrication and densification of high performance carbon nanotube/copper composite fibers. Carbon 2017, 123, S-7

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