Detailed characterisation of TiO2 nano-aggregate morphology using TEM image analysis

Abstract

A detailed morphological characterisation is performed on flame synthesised TiO 2 nano-aggregates (number of primaries, N < 10) using transmission electron microscopy (TEM) image analysis and mobility measurements. The sizedependent collection efficiency of the TEM sampling method is accounted for with a simple correction for particle deposition through impaction and diffusion. The TEM-derived sizes show excellent agreement with electrical mobility measurements. Primary particle size, aggregate size, and degree of aggregation distributions were obtained for two different flames and varying precursor loading. The analysis reveals some particle aggregation which is likely to occur only very late in the growth stage, leading to the similarity between the primary particle and spherical particle size distributions. The degree of aggregation is defined as the ratio of gyration to spherical equivalent sizes from the projected area analysis, allowing identification of particles with spherical and non-spherical morphologies. The size distributions are found to be strongly affected by precursor loading but not by flame mixture or maximum temperature. In all cases, approximately 60-70% particles are spherical while the rest form small aggregates. The detailed morphological information reported provides the much-needed experimental data for studying the early stage particle formation of TiO 2 from titanium tetraisopropoxide (TTIP) in a well-defined burner configuration.

Numerical simulation and parametric sensitivity study of titanium dioxide particles synthesised in a stagnation flame

“…A laminar stagnation flame, stabilised by flow stretch, was used to prepare TiO 2 nanoparticles from titanium tetraisopropoxide (TTIP) precursor. Full details of the experimental investigation are presented in (Manuputty et al, 2019b). The premixed gas was heated to 150 • C with exit velocity of 436 cm/s.…”

“…Nanoparticle morphology was characterised by analysing TEM images and mobility measurements. Details on the sampling procedure, dilution test and particle characterisation are reported in (Manuputty et al, 2019b), so are not repeated here. Overall, it was found that the particle morphology was sensitive to the TTIP loading but was relatively insensitive to the equivalence ratio.…”

“…The purpose of this paper is to evaluate a new detailed particle model for titanium dioxide nano-aggregates (Lindberg et al, 2019b) against experimental measurements (Manuputty et al, 2019b), and perform a parametric sensitivity study to understand the influence of key parameters on the particle properties. We simulate the synthesis of titanium dioxide nanoaggregates from TTIP precursor in a stagnation flame using a two-step simulation methodology (Lindberg et al, 2019a).…”

A detailed particle model for polydisperse aggregate particles

“…Aggregate projected areas of 2048 randomly selected particles were obtained from image analysis, using the method described in [80], of projections produced using the algorithm given in Appendix B.6. Our base case simulation underpredicts the peak of the aggregate PSD ( Fig.…”

Study of industrial titania synthesis using a hybrid particle-number and detailed particle model

“…Experimental studies and acquisition of plant data are hindered by elevated temperatures and pressures (>1000 K and several bar), residences times in the order of milliseconds and the chlorine environment. However, useful laboratory studies exist, including the early thin film studies of Ghoshtagore [11] and hot wall reactor of Pratsinis et al [12] as well as many more recent results [13,14,15,16]. In addition to allowing direct study of particulate properties, for example by imaging, such studies provide a means of testing and building numerical models [17,18,19] which allows for rapid investigation of process conditions that are expensive/challenging to realize experimentally.…”