Title: EFFECTS OF REFLUX TIME AND TEMPERATURE ON CHEMICAL FUNCTIONALIZATION OF HELICAL CARBON NANOTUBES
Abstract: Due to their unique structural configurations, flexibility, and exceptional materials properties (i.e., mechanical, thermal, electrical, and magnetic), the helical structures of Carbon Nanotubes (CNTs) have a great potential for use in a wide range of applications, e.g., biomedical devices and sensors, nano-electro-magnets, micro- and nano-electronics, high-performance materials, shock absorbing nano-devices, and nanocomposites. Here, the coil-spring shape of these CNTs allow the structure to absorb impact loads more efficiently and endure large deformations with possibilities of nearly 100% shape recovery. Once they are properly incorporated in a host material, e.g., polymeric resins, they can provide higher flexibilities and resilience, in addition to the improvement of mechanical, thermal, and electrical properties of the host resin. In addition, they can mechanically interlock with the host resin molecules (in nanoscale) and considerably improve their stiffness, strength, and hardness. However, the overall performance of the resulting nanocomposite will directly depend on the CNTs-resin interactions/interfaces that will decide the load transfer and transport efficiencies. It has been concluded that most nanocomposites suffer from the lack of nanomaterials homogeneous dispersion and weak interface interactions/bonds. To address these issues, helical CNTs can be functionalized using various chemical routes. This study is aimed to investigate the effects of various processing parameters in chemical functionalization of helical CNTs. The helical shape of CNTs increases the entanglement level among these CNTs and polymer chains, as compared to the straight CNTs. A reflux process with a strong acidic solution used for chemical functionalization of helical CNTs. In this work, effects of reflux time and reflux temperature on extend of the functionalization of helical CNTs are investigated. To characterize the functionalized CNTs, Fourier transform infrared spectroscopy (FTIR), visual dispersion inspection, Scanning Electron Microscopy (SEM), X-ray diffraction spectroscopy (XRD), and Raman spectroscopy methods were used. Our results showed that functionalization of helical CNTs were successful for most process parameters and all methods demonstrated a higher dispersion rate. All functionalized samples demonstrated higher solubility compared to pristine helical CNTs. The extension of reflux time was not that effective in increasing the dispersion rate for treated helical CNTs at high temperatures. However, prolonging the process increased the solubility for helical CNTs, which were refluxed in low temperatures. By increasing the reflux temperatures, the solubility increased for all CNTs samples, except for the ones which were refluxed for the longest extent of time periods.
Authors: Sean Reza Taklimi, Ali Ghazinezami, Kim Cluff, Davood Askari
Conference: CAMX 2017 –Orlando