HPPMS/MPP
Pulsed dc sputtering
Reactive sputtering
Plasma diagnostic
Nanocomposite coatings
Multilayer coatings
'Smart' coatings
Carbon nanotube
SHS synthesis
 
 
Carbon nanotube and nanofiber
 

  

Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) are molecular-scale 1D wires with excellent mechanical and electronic properties. Recent experimental studies have shown that CNTs are one of the stiffest materials and buckle elastically under large bending or compressive strains compared to other nanoscale materials. Some results also indicated ballistic transport through metallic single walled CNTs (SWCNT). Because of these unique characteristics of CNTs and CNFs, a variety of potential applications such as hard composite tribological coating, gas storage media, gas sensors, electrode materials, flat panel displays, adsorbents, and quantum devices, have been studied. One of the major advantages of these materials is expected in the area of light-weight and high performance materials such as in the automobile sector by replacing steel, ceramic or aluminum components with CNFs or CNTs composites, thereby resulting in a weight reduction of up to 70% and use of less fuel.

CNFs and CNTs have been synthesized mainly by laser vaporization, arc discharge, and thermal chemical vapor deposition (T-CVD) by the decomposition of a carbon source on selective catalysts (Fe, Co, Ni, or their alloys). The laser and arc methods involve local temperature well over 1000 oC. The high synthesis temperature (above 550 oC) of T-CVD also limits its application. Generally, glass, polymer and different metal substrates have been used for field emission display and electrode device application. Therefore, a low temperature process is required for the growth of CNTs or CNFs to maintain thermal stability of the glass, polymer or metal materials. Plasma enhanced chemical vapor deposition (PECVD) is an efficient low temperature method. In PECVD, the plasma can decompose a carbon source, and ionize hydrocarbon and hydrogen to produce reactive radicals (such as H+, C+, CH, CH2, and CH3) at relatively low temperature. Meanwhile hydrogen ions can reduce the metal catalysts and increase their activity and wetting ability.

We have successfully synthesized vertically aligned multi-walled carbon nanotubes (MWNT), turbostratic carbon nanofibers (CNFs), and platelet graphite nanofibers (PGNFs) on Fe, Ni and FeNi catalyst layers on different substrates using radio frequency (RF) and direct current (DC)-PECVD at low temperature (under 200oC). SEM and TEM images of the CNTs and CNFs are shown in Figures 1 to 3.

Figure 1. SEM and TEM images of CNTs grown from 8nm FeNi catalytic layer on glass by RF-PECVD (a) SEM top view, (b) SEM cross section, (c) TEM of CNTs, (d) high resolution TEM of a CNT.

Figure 2. SEM cross-section images of CNTs on 4nm FeNi/glass (a) DC 50W without O2, (b) DC 50W and 0.1%O2, (c) DC 50W and 0.22%O2, (d) DC 80W and 0.1% O2

Figure 3. SEM top view images of (a) Turbostratic Carbon Nanofibers (T-CNFs) grown on 8nm Ni Layer on Si, (b) Platelet Graphite Nanofibers (PGNFs)) grown on 8nm Ni layer on TiN/Si

   
 
 
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