Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5430254 | Journal of Quantitative Spectroscopy and Radiative Transfer | 2008 | 10 Pages |
The morphology of WO3 aggregates formed by irregular nanoparticles (Dâ¼40 nm) and nanowires of different aspect ratios (2, 4, 6, and 10 μm nominal lengths) dispersed in commonly used polar solvents without dispersant agents is investigated using a small-angle light scattering technique and by means of fractal theory. Nanoparticles form compact spherical aggregates (Dfâ¼2.6), whereas 2 μm nanowires with low aspect ratio (L/Dâ¼10) follow a slow cluster-cluster aggregation mechanism with no discernable change in fractal dimension (Df=2.1) monitored in an extended period of 6 months, despite a notable growth in size (Rg=2.3-3.1 μm). For higher aspect ratio nanowires, scattered intensity profiles, which migrate towards the Porod regime, qualitatively obey the Lorenz-Mie theory predictions. The 10 μm nanowires with very high aspect ratio (L/Dâ¼250) are observed to form stable dispersions in a time span of 6 days. Analytical methods based on spherical primary particle formulations predict Df=1.9, 1.7, and 1.4 for 4, 6, and 10 μm nanowires, respectively.