Modeling of spray pyrolysis—why are the synthesized Y₂O₃ microparticles hollow?

Abstract

in Wiley InterScience (www.interscience.wiley.com).There are some major advantages to be gained in processing micronic europium doped yttrium oxide Y 2 O 3 particles for phosphor applications using spray pyrolysis. To better understand the influence of the operating conditions and also why hollow particles are formed, a complete one-dimensional modeling of the pure evaporation then evaporation/precipitation steps of micronic water/Y(NO 3 ) 3 droplets has been performed. Among the main results, it appears that no concentration gradient exists inside droplets during the pure evaporation stage and that the evaporation/precipitation stage, occurring in less than 10 23 s, leads to compact particles theoretically formed of a coherent porous medium of Y(NO 3 ) 3 Á5H 2 O. But the analysis of phenomena occurring during the thermolysis step between 95 and 3008C has revealed that a partial liquefaction of the hydrated yttrium nitrate occurs with concomitant release of gas. As a consequence, a crust of lightly hydrated yttrium nitrate probably appears, followed by particle inflation and leading to the formation of broken hollow particles.

Effect of TiO2 and ZnO on PLA degradation in various media

“…ZnO powder, with particles size of 100-500 nm, was supplied by Pylote SAS in Dremil-Lafage, France [22,23].…”

Nanocomposites materials generated from a spray

“…Nitrate species are evolved when the synthesis is conducted at higher temperature (820 K). These observations prove the complexity of the SP synthesis during which occur in a limited range of time the solute precipitation, the solvent evaporation and chemical reactions between the constituents in each droplet [25]. After water washing, XRD patterns of soluble phases NaCl and NaNO 3 are not observed, the diffraction diagrams exhibit the peaks of α-Fe 2 O 3 and broad features assigned to hydrated species (ferrihydrites) as discussed below.…”

Spectroscopic study of the 4fn-15d transitions of LaPO4 doped with Pr3+ or co-doped with Pr3+ and Gd3+ in the Vacuum Ultra Violet region

“…Each droplet of aerosol acts as an individual reaction environment, and the final morphology results from the condensation and polymerization processes within the droplet. As described by Gurav et al [35] and Dexpert et al [36], in the drying zone, as the evaporation process occurs on the aerosol droplet, the air/solution interface moves progressively from the surface to the center, and the consequent precipitation promotes particle densification. Preferential precipitation on the surface may also occur, creating a supersaturated surface in the droplet.…”