Copper/single-walled carbon nanotube (SWCNT) composites were fabricated by electrodeposition using a freestanding SWCNT film as a template. The SWCNT films were directly electrodeposited to form copper/SWCNT composites. An acidic copper sulfate bath was employed as a basic plating bath, and the effects of additives to the basic bath on the morphologies of copper deposits were examined. Poly(ethylene glycol), chloride ions (Cl -), bis(3-sulfopropyl)disulfide (SPS), and Janus green B (JGB) were added individually or in combination as additives. Electrodeposition of copper occurred only on the surface of the SWCNT film when using the basic plating bath without additives. In contrast, copper was deposited not only on the surface but also in the interior of the SWCNT film when using the plating baths containing at least PEG and Cl -, resulting in copper/SWCNT composites. Electrodeposition of copper inside the SWCNT film was accelerated dramatically when all four additives (PEG, Cl -, SPS, and JGB) were added to the basic bath. This novel fabrication method of copper/CNT composites using CNT films as templates can be applied to the fabrication of various types of metal/CNT composites. Carbon nanotubes (CNTs) exhibit high thermal conductivity 1-6 and high current-carrying capacity (ampacity) 7 as well as excellent mechanical characteristics.8-10 Therefore, the development of practical applications of CNTs is an active area of research. Copper/CNT composites are promising materials, especially in the electronics field, and many fabrication methods, such as spark plasma sintering, [19][20][21][22][23] have been reported. The CNT composite plating has advantages, such as the uniform distribution of CNTs in metal matrices derived from a homogeneous dispersion of CNTs in plating baths, which results in little damage to CNTs due to dispersant addition at room temperature instead of direct grafting of hydrophilic groups that makes CNTs hydrophilic. Copper/CNT composite films possess excellent tribological 24,25 and field emission 26,27 properties. However, in general, the CNT content in electrodeposited composites is low (ca. 0.5 mass% 22 ), which could lead to insufficient thermal conductivity. 22 Therefore, other methods to obtain copper/CNT composites with a greater CNT content are needed.Recently, a freestanding, thin CNT film, 28,29 made from an aggregate of CNTs and so-called "bucky paper," has attracted considerable attention for its application as high efficiency filters, 30,31 displays, 32 lithium-ion battery anodes, 33 and supercapacitors. 34,35 Furthermore, composites using freestanding CNT films as flexible scaffolds for active materials have been investigated particularly intensively for their application to rechargeable batteries. [36][37][38][39][40][41][42][43][44][45][46][47][48] Electrodeposition of copper inside the freestanding CNT film was expected to be an effective method for forming copper/CNT composites with greater CNT content. However, few studies on direct electrodeposition not limited to copper o...

Introduction Copper has many useful properties, such as high electrical conductivity, good thermal conductivity and ductility, resulting in the widespread use of copper plating in an electronics industry. Single-walled carbon nanotubes (SWCNTs) also exhibit attractive characteristics, including stable electrical resistance in the presence of high currents, superior thermal conductivity and good field emission properties, and so have a wide range of applications. Cu/SWCNT composites are also expected to exhibit excellent electrical and thermal conductivities. In the present research, we attempted to fabricate a novel Cu/SWCNT composite by copper deposition into Bakky-paper consisted of SWCNTs. Experimental Bakky-paper (SWCNT sheet) with a thickness in the range of 30 to 40 mm (Zeon Co.) was used as the cathode, and copper electrodeposition was performed on both sides under galvanostatic conditions with an immersed surface area of 2 cm2(= 1 cm × 1 cm × 2). Copper containing phosphorous as anodes were placed at both sides of the cathode, and then copper deposition was carried out with or without additives. The additives were polyethylene glycol (PEG), chloride ions, bis(3-sulfopropyl) disulfide (SPS) and Janus green B (JGB). The surfaces and cross-sectional morphologies of the composites obtained by the electrodeposition were observed by a field emission scanning electron microscopy (FE-SEM). The effects of plasma pretreatment of the Bakky-paper (SWCNT sheet) on microstructure and copper deposition were also examined.   Results and Discussion Figure 1 compares cross-sectional SEM images of Cu/SWCNT composites prepared by two kinds of electrodeposition bath. Figure 1(a) displays the composite prepared in a bath without additives. It is clear that copper plating proceeded only on Bakky-paper surface. This is the reason why the plating liquid could not penetrate the sheet. In contrast, the use of various additives in the plating bath (100 ppm PEG + 50 ppm Cl- + 2 ppm SPS + 2 ppm JGB) resulted in copious copper deposition within the sheet structure (Figure 1(b)). Electrodeposition under these conditions also generated numerous voids in the Cu/SWCNT composite and greatly increased the thickness of the SWCNT sheet. The application of the Cu/SWCNT composite-film would be effective for the development of electronics devices. Figure 1