Halloysite-TiO₂ nanocomposites: Synthesis and characterization

In this paper we describe the synthesis and characterization of nano-sized TiO₂ particles supported on Halloysite with halloysite to TiO₂ weight ratios of 30:70. Two halloysite- TiO₂ nanocomposites were prepared using two different halloysites (from Limnos island Greece and from Utah, USA). Both halloysite - TiO₂ nanocomposites were prepared by deposition of anatase form of TiO₂ on the halloysite surfaces using a sol-gel method with titanium isopropoxide as a precursor under hydrothermal treatment at 180 °C. Phase composition, particle morphology and physical properties of these samples were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Attenuated Total Reflection using Fourier Transform Infrared spectroscopy (ATR-FTIR) and N₂ specific surface area (SSA) analysis by BET. Preparation of halloysite-TiO₂ nanocomposites led to good dispersion of 3-10nm TiO₂ particles on halloysite surfaces. ATR-FTIR results indicated the formation of hydrogen bonding between the outer surfaces of halloysite tubes and TiO₂. After compositing with TiO₂ both halloysite samples largely showed interparticle mesopores of about 5.7nm, while halloysite from Utah, USA retained a higher SSA compared to the one from Limnos island Greece.