Pure Multi-walled Nanotubes Research Articles

Electrophysical and Electromagnetic Properties of Pure MWNTs and MWNT/PMMA Composite Materials Depending on Their Structure

Three types of carbon multi-walled nanotubes (MWNT) with different morphology and mean diameter (7.5, 10.5, 22 nm) were used to produce polymethylmetacrylate-based composites (MWNT/PMMA) with variable MWNT loading (0.5–5wt%). The electrophysical properties of produced composites and electromagnetic response in frequency range of 2–12 GHz were investigated. Electrical conductivity of composites depends on the MWNT type increasing with lowering of the nanotube diameter and loading in composite. Reflectance and transmittance coefficients were calculated from dielectric permittivity data and found to correlate with electrical conductivity. The highest level of EM reflection was obtained for 7.5 nm MWNT-based composites and makes the value of 0.65–0.7, whereas 22 nm MWNT/PMMA composites are more transparent for EM radiation with reflection coefficient 0.3–0.4 for the highest MWNT loading. Thus MWNT/PMMA composites demonstrate high EM shielding properties.

Effective Condition for Purification of Multi-walled Carbon Nanotubes by Nitric Acid

The multi-walled carbon nanotubes were synthesized on Fe-Ni bimetallic catalysts supported by MgO using thermal chemical vapor deposition. A comparative study on the effect of nitric acid molarity and time duration of acid treatment on purification of multi-walled nanotubes was done. The studies revealed that for finding a suitable condition for purification of multi-walled carbon nanotubes, it is necessary to determine suitable molarity of acid and immersion time of the carbon nanotubes. It was found that 5 M of boiling nitric acid at 3 h leads to the highest removal of the impurities with the least destructive effect. Various analytical techniques such as: scanning electron microscopy (SEM), high resolution transition electron microscopy (HRTEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and Raman spectroscopy techniques were employed to investigate the morphology, graphitization and quality of the carbon nanotubes.

Effective Condition for Purification of Multi-Walled Carbon Nanotubes by Nitric Acid

The multi-walled carbon nanotubes were synthesized on Fe-Ni bimetallic catalysts supported by MgO using thermal chemical vapor deposition. A comparative study on the effect of nitric acid molarity and time duration of acid treatment on purification of multi-walled nanotubes was done. The studies revealed that for finding a suitable condition for purification of multi-walled carbon nanotubes, it is necessary to determine suitable molarity of acid and immersion time of the carbon nanotubes. It was found that 5 M of boiling nitric acid at 3 h leads to the highest removal of the impurities with the least destructive effect. Various analytical techniques such as: scanning electron microscopy (SEM), high resolution transition electron microscopy (HRTEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and Raman spectroscopy techniques were employed to investigate the morphology, graphitization and quality of the carbon nanotubes.