Wednesday, December 23, 2009

Korean Researchers Set Precedent with Manufacturing Method for Metal/Carbon Nanotube Nano-Composites Using Electroplating



 Image Source: KAIST Patent Application 20070199826, Figure 4.
Korea Advanced Institute of Science and Technology (KAIST) (Daejeon, KR) inventors Yoon-Chul Son, Jung-Joon Yoo and Jin Yu disclose a precedent setting method for manufacturing metal/carbon nanotube nano-composites using electroplating in U.S. Patent Application 20070199826The metal/carbon nanotube nano-composite can replace all metal thin film materials capable of being electroplated including semiconductor interconnection material like aluminum, copper, and others.

The KAIST method for manufacturing metal/carbon nanotube nano-composite includes: adding carbon nanotubes and cationic surfactants in metal plating solution including metal or metal salt and performing electroplating in the cathode.  The method for manufacturing metal/carbon nanotube nano-composite using electroplating further comprises: immersing carbon nanotubes in acid solution and filtering the solution and carrying out heat treatment; adding the heat treated carbon nanotubes and cationic surfactants in metal plating solution including metal or metal salt and dispersing the carbon nanotubes.  Then a cathode and an anode are provided in the metal plating solution including the carbon nanotubes and the cationic surfactant, to which current is applied and electroplating is carried out in order to obtain metal/carbon nanotube nano-composite (complex material).

The carbon nanotube has excellent electrical conductivity, thermal conductivity and strength, thus is expected to show more excellent physical properties when combined with specific qualities of specific metals. Therefore, there have been a lot of developments of composites including carbon nanotubes.

Especially, when it comes to forming nano-composite of metal and carbon nanotubes, researches are directed to improving mechanical properties and the nano-composite is mainly made in the form of bulk. The nano-composite in the above form is mainly manufactured via a powder method or a sintering process.

Pure carbon nanotubes are formed at high temperature of 600.about.1000.degree. C. via chemical vapor deposition method deposition method and surface treatment prior to the deposition are important to control the growing direction and speed of the pure carbon nanotube. The carbon nanotube does not constitute densely packed structure to leave empty spaces between carbon nanotubes when it grows, leading to a big problem in replacing the existing metal thin film material. There have been attempts to fill the empty spaces between the carbon nanotubes with SiO2 etc. to use as semiconductor interconnections. When these interconnections are connected to form some layers, there is no alternative as to a process for the next layer.

There are no precedents of forming metal/carbon nanotube nano-composite in the type of thin film using electroplating until now due to the characteristics of the bar shape structure and no charges of the carbon nanotube. If metal and carbon nanotubes are simultaneously deposited at the same time by electroplating, densely packed structure unlike the growth of pure carbon nanotubes can be obtained and depositions at desired portions in a type of thin film are possible, also. Thus, all the metal thin films including the existing semiconductor metal interconnection can be replaced, improving their electrical, mechanical and thermal physical properties. Moreover, the KIST manufacturing method can be applied without changing the existing semiconductor interconnection process or the surface finishing process of electronic products, thus the present invention has good marketability and practicality.

The manufacturing method for metal/carbon nanotube nano-composite distributes carbon nanotubes at a molecule level, by a system that includes: adding carbon nanotubes and cationic surfactants which is adsorbed on the surface of the carbon nanotube in metal plating solution including metal or metal salt to constitute the plating solution; and completely separating and dispersing individual carbon nanotubes each other and carrying out electroplating.

The cationic surfactant is at least one selected from the group consisting of poly(diallyldimethylammonium chloride, PDMA), cetyltrimethylammonium chloride (CTAC), cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), dodecyltrimethylammonium chloride (DTAC), Decylamine, Dodecylamine, Hexadecylamine, Triethylamine, Octylsulfate, sodium salt, Hexylamine and Octadecylamine.

The KAIST method overcomes many prior limitations in manufacturing a metal/carbon nanotube complex material. . The metal/carbon nanotube nano-composite manufactured according KIST’s method can produce metal/carbon nanotube nano-composite in a type of thin film using electroplating, and can replace all metal thin film materials capable of being electroplated including semiconductor interconnection material like aluminum and copper, etc.

The KAIST metal/carbon nanotube nano-composite contrary to the growth of pure carbon nanotubes, grows to thin film with a densely packed structure and can be used without changing the existing process method.  As the metal/carbon nanotube nano-composite has carbon nanotubes uniformly dispersed into a metal matrix, the existing metal thin film is expected to improve the electric, mechanic and thermal physical characteristics.

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