Ananta Raj Adhikari

Thermal property of regioregular poly(3-hexylthiophene)/nanotube composites using modified single-walled carbon nanotubes via ion irradiation

The effects of radiation-induced modifications on the thermal stability and phase transition behaviour of composites made of 1% pristine or ion irradiated single-walled carbon nanotubes (SWNTs) and poly(3-hexylthiophene) (P3HT) are reported. Thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), Raman spectroscopy and electron spin resonance (ESR) were used to investigate the radiation-induced functionalization of carbon nanotubes and to assess the effect of ionizing radiation on the adhesion between macromolecular polymer and carbon nanotubes. Irradiation was used to introduce defects in a controlled way solely within pristine nanotubes before composite synthesis. The addition of irradiated SWNTs to a polymer matrix was found to enhance thermo-oxidative stability and phase transition behaviour. Further, ESR studies demonstrate the electronic interaction through charge transfer between filler and matrix. These results could have immense applications in nanotube composite processing. Based on the experimental data, a model for the interaction between polymeric chains and carbon nanotubes is proposed.

Ion-implantation-prepared catalyst nanoparticles for growth of carbon nanotubes

This letter demonstrates the use of catalyst nanoparticles prepared by ion implantation for growth of carbon nanotubes (CNTs) via chemical vapor deposition. Nickel ions of energy in 100keV were first implanted at room temperature into silicon dioxide to doses of 1015–1017cm−2. Postimplantation annealing was conducted to induce precipitation of implanted Ni atoms into nanoparticles. The samples were chemically etched to expose Ni nanoparticles on the surface. Finally, CNT growth on such prepared SiO2 substrates was achieved via chemical vapor deposition through decomposition of hydrocarbon. Our data show strong correlation in the size of resultant tube structures and preformed catalyst nanoparticles, with larger Ni nanoparticles resulting in larger tube diameters. This work may provide an effective way for seeding catalyst nanoparticles in high-aspect-ratio via/trench structures for growing CNTs for interconnect applications.

Stability of ion implanted single-walled carbon nanotubes: Thermogravimetric and Raman analysis

In this work, the effect of different ions (hydrogen, helium, and neon) implanted on single-walled carbon nanotube (SWNT) is being analyzed using thermogravimetric analysis (TGA), Raman scattering, and x-ray photoelectron spectroscopy (XPS). The TGA result shows that the temperature for maximum decomposition rate (Tmax) increases at relatively low doses, i.e., by about 30°C after hydrogen ion implantation (at the ion dose of 1015cm−2), 17°C after helium ion implantation (at the ion dose of 1013cm−2), and contributes no significant enhancement after neon implantation for all doses. The increase of Tmax indicates that small mass ion can be utilized to improve the thermal-oxidative stability of SWNTs. Raman scattering and XPS were used to monitor the lattice damage from ion implantation and chemical bonding states of the materials. The results indicated the material rigidity for low doses of hydrogen and helium, while the application of higher doses of neon caused the material to transform towards amorphous ...

Effects of MeV Ions on Thermal Stability of Single Walled Carbon Nanotubes

The properties of carbon nanotubes (CNTs) are closely dependent on their structures, and therefore may be tailored by controllably introducing defects in the nanotube systems. In this work, we have investigated the effects of energetic ions (H + and He + ) on the thermal stability of single wall nanotubes (SWNTs) against oxidation in air. SWNTs were irradiated with MeV ions to various doses in the range 10 13 -10 16 cm −2 . Thermogravimetric analysis (TGA) was used to determine the loss of CNT masses as a result of oxidation processes. As opposed to the case of pristine SWNTs for which the temperature (Tmax) corresponding to maximum oxidation rate was found to be ∼ 495 °C, ion beam processing significantly enhanced the thermal stability of nanotubes, e.g., T max increased by about 30 °C after H + implantation (dosage: 10 15 cm −2 ) and 17 °C after He + implantation (dosage: 10 13 cm −2 ). The activation energies for thermal oxidation under various conditions were also extracted from TGA data, with values ranging from 1.13 eV (for pristine SWNTs) to 1.37 eV, depending on ion doses and species. Raman spectroscopy was used to determine the characteristics of the G band (C-C stretching mode) and D band (disorder induced mode) in CNTs. The work suggests that the SWNTs modifies to more stable structure (may be cross-linked SWNTs) at small doses. Once the number of defects exceeds some critical value (depending on the type and dosage of bombarding ion) the bonding energy in CNTs weakens, leading to the reduced thermal stability of CNTs against oxidation.