scholarly journals Investigation of Low-Pressure Bimetallic Cobalt-Iron Catalyst-Grown Multiwalled Carbon Nanotubes and Their Electrical Properties

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Muhammad Aniq Shazni Mohammad Haniff ◽  
Hing Wah Lee ◽  
Wai Yee Lee ◽  
Daniel C. S. Bien ◽  
Khairul Anuar Wahid ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Growth Rate ◽  
Electrical Properties ◽  
Multiwalled Carbon Nanotubes ◽  
Iron Catalyst ◽  
Chemical Vapor ◽  
Average Diameter ◽  
Gas Pressure ◽  
Multiwalled Carbon ◽  
Cobalt Iron

A bimetallic cobalt-iron catalyst was utilized to demonstrate the growth of multiwalled carbon nanotubes (CNTs) at low gas pressure through thermal chemical vapor deposition. The characteristics of multiwalled CNTs were investigated based on the effects of catalyst thickness and gas pressure variation. The results revealed that the average diameter of nanotubes increased with increasing catalyst thickness, which can be correlated to the increase in particle size. The growth rate of the nanotubes also increased significantly by ~2.5 times with further increment of gas pressure from 0.5 Torr to 1.0 Torr. Rapid growth rate of nanotubes was observed at a catalyst thickness of 6 nm, but it decreased with the increase in catalyst thickness. The higher composition of 50% cobalt in the cobalt-iron catalyst showed improvement in the growth rate of nanotubes and the quality of nanotube structures compared with that of 20% cobalt. For the electrical properties, the measured sheet resistance decreased with the increase in the height of nanotubes because of higher growth rate. This behavior is likely due to the larger contact area of nanotubes, which improved electron hopping from one localized tube to another.

scholarly journals Effect of Different Catalyst Deposition Technique on Aligned Multiwalled Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Mohamed Shuaib Mohamed Saheed ◽  
Norani Muti Mohamed ◽  
Zainal Arif Burhanudin
Keyword(s):  
Carbon Nanotubes ◽  
Chemical Vapor Deposition ◽  
Multiwalled Carbon Nanotubes ◽  
Vapor Deposition ◽  
Iron Catalyst ◽  
Chemical Vapor ◽  
Preparation Technique ◽  
Deposition Technique ◽  
Multiwalled Carbon ◽  
Thermal Chemical Vapor Deposition

The paper reported the investigation of the substrate preparation technique involving deposition of iron catalyst by electron beam evaporation and ferrocene vaporization in order to produce vertically aligned multiwalled carbon nanotubes array needed for fabrication of tailored devices. Prior to the growth at 700°C in ethylene, silicon dioxide coated silicon substrate was prepared by depositing alumina followed by iron using two different methods as described earlier. Characterization analysis revealed that aligned multiwalled carbon nanotubes array of 107.9 µm thickness grown by thermal chemical vapor deposition technique can only be achieved for the sample with iron deposited using ferrocene vaporization. The thick layer of partially oxidized iron film can prevent the deactivation of catalyst and thus is able to sustain the growth. It also increases the rate of permeation of the hydrocarbon gas into the catalyst particles and prevents agglomeration at the growth temperature. Combination of alumina-iron layer provides an efficient growth of high density multiwalled carbon nanotubes array with the steady growth rate of 3.6 µm per minute for the first 12 minutes and dropped by half after 40 minutes. Thicker and uniform iron catalyst film obtained from ferrocene vaporization is attributed to the multidirectional deposition of particles in the gaseous form.

Multiwalled Carbon Nanotubes by Chemical Vapor Deposition Using Multilayered Metal Catalysts

2002 ◽  
Vol 106 (22) ◽  
pp. 5629-5635 ◽  
Author(s):  
Lance Delzeit ◽  
Cattien V. Nguyen ◽  
Bin Chen ◽  
Ramsey Stevens ◽  
Alan Cassell ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Chemical Vapor Deposition ◽  
Multiwalled Carbon Nanotubes ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Metal Catalysts ◽  
Multiwalled Carbon

3D Nanocomposites of Covalently Interconnected Multiwalled Carbon Nanotubes with SiC with Enhanced Thermal and Electrical Properties

2015 ◽  
Vol 25 (31) ◽  
pp. 4985-4993 ◽  
Author(s):  
Lakshmy Pulickal Rajukumar ◽  
Manuel Belmonte ◽  
John Edward Slimak ◽  
Ana Laura Elías ◽  
Eduardo Cruz-Silva ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Properties ◽  
Multiwalled Carbon Nanotubes ◽  
Multiwalled Carbon ◽  
Thermal And Electrical Properties

The Catalytic Effect on Vertically Aligned Carbon Nanotubes

2003 ◽  
Vol 800 ◽  
Author(s):  
Nam Seo Kim ◽  
Seung Yong Bae ◽  
Jeunghee Park
Keyword(s):  
Carbon Nanotubes ◽  
Growth Rate ◽  
Nitrogen Content ◽  
Catalytic Effect ◽  
Bulk Diffusion ◽  
Chemical Vapor ◽  
Decisive Role ◽  
Crystalline Perfection ◽  
Multiwalled Carbon ◽  
Vertically Aligned

ABSTRACTWe report the catalytic effect on the synthesis of multiwalled carbon nanotubes (CNTs). The CNTs were grown vertically aligned on the iron (Fe), cobalt (Co), and nickel (Ni) catalytic nanoparticles deposited on alumina substrates by thermal chemical vapor deposition (CVD) of acetylene in the temperature range 900–1000 °C. We also synthesized them on the silicon oxide substrates by pyrolyzing iron phthalocyanine (FePc), cobalt phthalocyanine (CoPc), and nickel phthalocyanine (NiPc) at 700–1000 °C. In both syntheses, the CNTs grown using Fe exhibit about 2 times higher growth rate than those using Co and Ni. As the temperature rises from 700 to 1000 °C, the growth rate of CNTs increases by a factor of 45. The Arrhenius plot of growth rates provides the activation energy 30 ± 3 kcal/mol for all three catalysts, which is similar with the diffusion energy of carbon in bulk metal. It suggests that the bulk diffusion of carbon would play a decisive role in the growth of CNTs. The diameter of CNTs is in the range of 20–100 nm, showing an increase with the temperature. As the diameter is below 30 nm, the CNTs usually exhibit a cylindrical structure. The CNTs were intrinsically doped with the nitrogen content 2–6 atomic%. The degree of crystalline perfection of the graphitic sheets increases with the temperature, but depends on the catalyst and the nitrogen content. The graphitic sheets of CNTs grown using Fe are better crystalline than those grown using Co and Ni. As the nitrogen content increases, the degree of crystalline perfection decreases and the structure becomes the bamboolike structure probably due to a release of strains.

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