Metallization of multi-walled carbon nanotubes with copper by an electroless deposition process

doi:10.1016/j.elecom.2004.08.007

Electrochemistry Communications

Volume 6, Issue 10, October 2004, Pages 1042-1044

https://doi.org/10.1016/j.elecom.2004.08.007 Get rights and content

Abstract

An advantageous procedure has been developed, allowing metallization of multi-walled carbon nanotubes (MWCNTs, mean diameter: 50–80 nm) with Cu layer by an electroless deposition process. Such a procedure for achieving electroless Cu deposition on MWCNTs involves acid pre-clean, sensitization and activation. Results show that metallizated MWCNTs keep the fiber-like appearances with uniform distribution. This resulting nanotube-derived material is comprised of a nanocrocrystalline Cu layer and inner nanotube covered with Cu layer. The results of this work have demonstrated the effectiveness of electroless deposition on the metallization of MWCNTs.

Introduction

Multi-walled carbon nanotube (MWCNT) is an ideal raw material for various applications due to its outstanding mechanical characteristics such as high tensile strength and high elastic modulus, high thermal conductivity and electric conductivity [1], [2]. Recently, there has been great interest in the metallization of MWCNTs [3], [4] for creating new metal-matrix-based carbon tube composites. This metallization process firstly belongs to a kind of surface modification of MWCNTs, not only can increase the surface active sites to improve bonding between nanotube and resin or ceramic [5], but also can maintain the superior performance and excellent intrinsic properties of MWCNTs in the composites. Furthermore, this metallization of MWCNTs has been shown to have significant potential for the fabrication of new powder MWCNT-metal composites [6], [7], thus extending the application fields of MWCNTs.

Such metallization of MWCNTs can be achieved via an electroless deposition process at normal temperature state. To obtain the MWCNTs covered with a continual Cu layer, a pre-treatment procedure comprised of acid pre-clean, sensitization and activation is essential to purify MWCNTs and increase the catalytic sites on MWCNTs. In this study, nitric acid was used to pre-clean the MWCNTs, and so-called ‘two-step’ process was performed to impart the catalyzation effect to the surface of MWCNTs for the subsequent electroless Cu deposition [8]. Moreover, MWCNTs tend to aggregate into packed ropes or entangled networks due to strong inter-tube van der Waals attraction, which may hinder the formation of Cu-deposited MWCNTs with homogenous distribution. Here, one cationic polymer was used to disperse MWCNTs in the aqueous solution on each pre-treatment step and subsequent electroless deposition process.

The aim of this work was to develop an advantageous procedure allowing the metallization of the MWCNTs with copper layers. An effective deposition bath containing glyoxalic acid as reductant was designed, and then was used to electrolessly deposited Cu layer on MWCNTs. The microstructures of resulting Cu-MWCNT composites were characterized with the help of field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM).

Section snippets

Experimental

The MWCNTs used were synthesized via catalyst assisted CVD (Showa Denko Co. Ltd) [9]. They were then heat-treated at 2800 °C under an argon flow for 30 min to form graphitic layer structure. MWCNTs were typically 50–80 nm in diameter and 10–20 μm in average length.

The electroless deposition bath was composed of 0.03 M CuSO₄ · 5H₂O as the metal ions source, 0.25 M EDTA · 2Na as the complexing agent and 0.1 M CHOCOOH · H₂O as the reductant. All solutions were prepared using deionized water and reagent

Results and discussion

FE-SEM has been used to observe the morphological features of Cu-deposited MWCNTs. The Cu-deposited MWCNTs in the diameter of 130–180 nm are present clearly in Fig. 1, showing the fiber-like appearance of composites with a homogenous distribution. This indicates that the above pre-treatment procedure used to achieve the metallization of MWCNTs with Cu layer by an electroless deposition process is effective. The resulting nanotube-derived composite is comprised of polycrystalline Cu layer and

Conclusions

Metallization of MWCNTs with Cu layer has been achieved through a pre-treatment process and subsequent electroless deposition process. Results show Cu layers with the average thickness of 40 nm have been deposited on the surfaces of MWCNTs. The resulting composites with a homogenous distribution are comprised of nanocrystalline Cu layers and inner MWCNTs covered with Cu layers. This study provides an effective means to fabricate powder metal-deposited MWCNT composites with the considerable

Acknowledgement

This research was supported by the CLUSTER of the Ministry of Education, Culture, Sports, Science and Technology, Japan. We thank Mr. Yoshinari Misaki of Tokyo Metropolitan University for assisting in TEM observation.

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Metallization of multi-walled carbon nanotubes with copper by an electroless deposition process

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusions

Acknowledgement

J. Cryst. Growth

Electrochem. Commun.

Carbon

Carbon

Appl. Phys. Lett.