Korea Advanced Institute of Science and Technology ((KAIST) Daejeon, KR) chemists disclose in U.S. Patent 20100029823 a method for fabricating carbon nanotube-metal-polymer nanocomposites that avoid the problem of agglomeration in polymer composites. According to inventors Soon Hyung Hong, Seong Woo Ryu and Chan Bin Mo the carbon nanotube-metal-polymer nanocomposite is made up of carbon nanotubes decorated with metal portion in a necklace form which are homogeneously dispersed in a polymer base.
The method for fabricating a carbon nanotube-metal-polymer nanocomposite comprises: preparing carbon nanotube-metal nanocomposite powder by introducing a polyol reducing agent as well as metal precursor in a carbon nanotube colloidal solution and heating the same; dispersing the carbon nanotube-metal nanocomposite powder in a polymer base; and curing the polymer base to form the carbon nanotube-metal-polymer nanocomposite.
If the dispersion of carbon nanotubes is poorly homogeneous, the microwave shielding and absorbing properties are decreased. The KAIST method results in improved microwave absorbing and shielding properties in the final product as a result of the homogenous dispersion of carbon nanotube-metal necklaces.
In order to achieve a homogeneous dispersion, the method for fabricating a carbon nanotube-metal-polymer nanocomposite comprises: preparing carbon nanotube-metal nanocomposite powder by introducing a polyol reducing agent as well as metal precursor in a carbon nanotube colloidal solution and heating the same; dispersing the carbon nanotube-metal nanocomposite powder in a polymer base; and curing the polymer base to form the carbon nanotube-metal-polymer nanocomposite.
The colloidal solution may contain a solvent selected from a non-polar solvent and a polyol solvent.
A particular procedure for fabrication of the carbon nanotube-metal-polymer nanocomposite is described as follows.
At first, Ni metal as well as a polyol reducing agent were added to a carbon nanotube colloidal solution. Then, the Ni metal is reacted with the polyol reducing agent at 190 to 300.degree. C. for 30 minutes to 2 hours to produce carbon nanotube-Ni nanocomposite powder decorated with Ni metal particles in a necklace form. In this regard, the carbon nanotube-Ni nanocomposite powder had 50% by volume of carbon nanotubes by regulating amounts of the Ni metal and the carbon nanotubes to be added.
Such produced carbon nanotube-Ni nanocomposite powder was dispersed in epoxy resin at 30 to 80.degree. C. by ultrasonic treatment. Following this, the epoxy resin was formed into a shaped product using a curing agent at 80 to 120.degree. C. so as to produce a carbon nanotube-Ni-epoxy nanocomposite.
Conventional processes in the related art did not solve a problem concerning agglomeration of carbon nanotubes in a polymer base. Therefore, the present proposed a novel process for improving microwave absorbing and shielding properties solves the agglomeration problem.
Briefly, the process does not cause agglomeration of carbon nanotubes in the polymer base. In addition, metal particles and carbon nanotubes may form an integrated microfine structure so that the nanocomposite exhibits improved electrical conductivity and enhanced microwave shielding and absorbing properties in a wavelength range of GHz.
Furthermore, the nanocomposite may be applied as a microwave absorptive substance in a case of using a ferromagnetic metal in fabricating the nanocomposite. Alternatively, using any conductive metal may be used to fabricate the inventive nanocomposite which is used as a microwave shielding substance. The above both substances can be employed in the wavelength range of GHz.
At first, Ni metal as well as a polyol reducing agent were added to a carbon nanotube colloidal solution. Then, the Ni metal is reacted with the polyol reducing agent at 190 to 300.degree. C. for 30 minutes to 2 hours to produce carbon nanotube-Ni nanocomposite powder decorated with Ni metal particles in a necklace form. In this regard, the carbon nanotube-Ni nanocomposite powder had 50% by volume of carbon nanotubes by regulating amounts of the Ni metal and the carbon nanotubes to be added.
Such produced carbon nanotube-Ni nanocomposite powder was dispersed in epoxy resin at 30 to 80.degree. C. by ultrasonic treatment. Following this, the epoxy resin was formed into a shaped product using a curing agent at 80 to 120.degree. C. so as to produce a carbon nanotube-Ni-epoxy nanocomposite.
Conventional processes in the related art did not solve a problem concerning agglomeration of carbon nanotubes in a polymer base. Therefore, the present proposed a novel process for improving microwave absorbing and shielding properties solves the agglomeration problem.
Briefly, the process does not cause agglomeration of carbon nanotubes in the polymer base. In addition, metal particles and carbon nanotubes may form an integrated microfine structure so that the nanocomposite exhibits improved electrical conductivity and enhanced microwave shielding and absorbing properties in a wavelength range of GHz.
Furthermore, the nanocomposite may be applied as a microwave absorptive substance in a case of using a ferromagnetic metal in fabricating the nanocomposite. Alternatively, using any conductive metal may be used to fabricate the inventive nanocomposite which is used as a microwave shielding substance. The above both substances can be employed in the wavelength range of GHz.
FIG. 1 is a flowchart illustrating the KAIST method for fabricating a carbon nanotube-metal-polymer nanocomposite to avoid agglomeration and improve microwave shielding and absorbing
FIG. 2 is an electron microphotograph showing a carbon nanotube-Ni nanocomposite powder.
FIG. 3 is an electron microphotograph showing a carbon nanotube-Ni-epoxy nanocomposite
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