Physical properties of porous titania films composed of nanoparticle aggregates
- PDF / 182,790 Bytes
- 9 Pages / 585 x 783 pts Page_size
- 34 Downloads / 196 Views
Jinwon Park and Gil Leea) School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907-2100
Sheryl Ehrmanb) Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742 (Received 23 November 2005; accepted 16 March 2006)
Highly porous films of titania composed of nanoparticle aggregates were synthesized via gas-to-particle conversion and particle-precipitated chemical vapor deposition. The films were annealed in air for 12 h at temperatures ranging from 400 to 1000 °C. Atomic force microscopy was used to determine the Young’s modulus and hardness of both the as-synthesized and annealed films. The Young’s modulus and hardness of the as-synthesized films were 4.0 ± 0.4 MPa and 0.026 ± 0.003 MPa, respectively. There was no significant change in either modulus or hardness upon annealing until the films were annealed at a temperature of 1000 °C. The Young’s modulus and hardness of these films were 56 ± 6 MPa and 0.10 ± 0.01 MPa, respectively. Results from dynamic light scattering measurements of aggregate size and surface area measurements suggest that annealing at 1000 °C leads to increased networking between distinct nanometer-scale titania aggregates, which strengthens the film.
I. INTRODUCTION
Titania nanoparticulate films are of interest in high surface area applications such as gas sensors,1,2 photocatalysts in treatment of wastewater3 and air pollutants,4,5 and photovoltaic electrodes for lithium batteries6 and low cost solar cells.7 In particular, there has been a number of studies of titania films for use as photocatalysts and in photovoltaic applications. For example, Barbe et al.7 showed that the nanostructure of the titania films influenced the photovoltaic response of the solar cell. Studies of structural changes of titania films with heat treatment revealed that crystallinity, specific surface area, and photocatalytic properties of the titania films changed with increasing calcining temperature.8,9 In simulations of the nanostructure of nanoparticle films, with emphasis on titania films for solar cells, Lagemaat et al.10 showed that increasing the porosity of the film decreases the coordination number of each particle. In a related study, the particle connectivity was also shown to
Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2006.0204 1738
J. Mater. Res., Vol. 21, No. 7, Jul 2006
influence electron transport in solar cells.11 Kulkarni and Biswas12 used a Brownian dynamics simulation approach to predict morphology of nanoparticle deposits in the presence of interparticle interactions, with the motivation that deposit morphology and structure affect the efficiency of the solar cell. The simulations revealed that van der Waals and columbic interactions influence the morphologies of the nanoparticle deposits. In the above-mentioned studies of titania films, the focus is mainly on how the nanostructure affects their photocatalytic and photosynthetic properties. Wi
Data Loading...
