Tailoring crystal structure and morphology of MnOx nanoparticles via electrospray-assisted flame spray pyrolysis

Abstract

In this work, MnOx nanoparticles were produced by a continuous electrospray-assisted flame spray pyrolysis (EAFSP) method. In this regard, the precursor solutions containing manganese (II) nitrate hydrate (MnN) dissolved in 1-propanol precursor solutions are initially atomized into charged droplets by an electrospray in the microdripping mode. Then, the electrically charged precursor droplets enter the flame in a controlled manner without requiring a dispersion gas. The synthesis was carried out with a variation in horizontal injection locations from different heights above the burner (HAB) to control the high-temperature residence times of the charged droplets without changing the flame conditions for producing MnOx nanoparticles with tunable particle properties. Various diagnostics such as TEM, SMPS, BET, and XRD were applied for analyzing the formation of primary and agglomerated MnOx nanoparticles as well as their crystal phases with varying temperature histories. Furthermore, phase-Doppler anemometry (PDA) experiments have been conducted to track the evolution of droplet size and droplet axial velocity in the electrospray flame, allowing for the study of combustion of electrosprayed MnN droplets and the presence of µ-explosions in the flame.