Aerosol analysis of residual and nanoparticle fractions from spray pyrolysis of poorly volatile precursors

Abstract

The quality of aerosol‐produced nanopowders can be impaired by micron‐sized particles formed due to non‐uniform process conditions. Methods to evaluate the quality reliably and fast, preferably on‐line, are important at industrial scales. Here, aerosol analysis methods are used to determine the fractions of nanoparticles and micron‐sized residuals from poorly volatile precursors. This is accomplished using aerosol instruments to measure the number and mass size distributions of Liquid Flame Spray‐generated alumina and silver particles produced from metal nitrates dissolved in ethanol and 2‐ethylhexanoic acid (EHA). The addition of EHA had no effect on silver, whereas, 5% EHA concentration was enough to shift the alumina mass from the residuals to nanoparticles. The size‐resolved aerosol analysis proved to be an effective method for determining the product quality. Moreover, the used on‐line techniques alone can be used to evaluate the process output when producing nanopowders, reducing the need for tedious off‐line analyses. © 2016 American Institute of Chemical Engineers AIChE J, 63: 881–892, 2017

Screening Precursor–Solvent Combinations for Li4Ti5O12Energy Storage Material Using Flame Spray Pyrolysis

“…However, tedious ex situ microscopic evaluation can be avoided by convenient online aerosol characterization to derive almost instant information on the particle size distribution and presence of larger particles from incomplete vaporization. 60 In conclusion, the particle products obtained from single-droplet and spray combustion are very similar with respect to size, crystallinity, and phase purity. This clearly suggests the need for spray solutions with a high combustion enthalpy and metal carboxylic complexes in order to obtain ultrafine single-crystalline particles.…”

“…In contrast, the combustion of LNT–EtOH + TTIP–EtOH resulted in multimodal particle size distributions with larger d mean (172 and 44.7 nm) and σ g (3.32 and 4.81) for both single-droplet and spray combustion, respectively (second and fourth columns of Figure ). However, tedious ex situ microscopic evaluation can be avoided by convenient online aerosol characterization to derive almost instant information on the particle size distribution and presence of larger particles from incomplete vaporization . In conclusion, the particle products obtained from single-droplet and spray combustion are very similar with respect to size, crystallinity, and phase purity.…”

Controlling the phase of iron oxide nanoparticles fabricated from iron(III) nitrate by liquid flame spray

“…The results presented above, however, contradict this assumption. EHA has been used before to eliminate residual particles in flame synthesis . Rosebrock et al found in single droplet experiments that in some cases the addition of EHA to the precursor solution led to strong droplet explosions, which led to smaller particles.…”

Aerosol Spray Controlled Synthesis of Nanocatalyst using Differential Mobility Analysis Coupled to Fourier-Transform Infrared Spectroscopy

“…2,8,10,23−25 Aerosol spray-based processing, which combines the production of spray droplets of liquid precursors and the subsequent pyrolysis of the produced spray, has been shown as a promising synthetic route for obtaining functional nanoparticles from an industrial perspective. 2,[5][6][7]10,11,20,21 In principle, the solvent in the sprayed liquid droplets evaporates via an aerosol-phase drying process. Followed by the procedure of thermal decomposition, the dried precursor particles transform to solid nanoparticles.…”

“…Followed by the procedure of thermal decomposition, the dried precursor particles transform to solid nanoparticles. 2,7,11,[14][15][16]26 The attractive technical features of the aerosol-based processing include that it is a continuous, low-cost process with a short reaction time, showing potential for a large-scale tailored production. 5,7,27−29 A variety of aerosol spray generation routes in combination with spray pyrolysis have been employed to date, for example, nebulization, ultrasonication, and aerosol flame synthesis, 7,27−32 with controlled size and composition are able to be produced via the gas-phase evaporation-induced self-assembly.…”