A Novel Porous Tube Reactor for Nanoparticle Synthesis with Simultaneous Gas-Phase Reaction and Dilution

Abstract

A novel porous tube reactor that combines simultaneous reactions and continuous dilution in a single-stage gas-phase process was designed for nanoparticle synthesis. The design is based on the atmospheric pressure chemical vapor synthesis (APCVS) method. In comparison to the conventional hot wall chemical vapor synthesis reactor, the APCVS method offers an effective process for the synthesis of ultrafine metal particles with controlled oxidation. In this study, magnetic iron and maghemite were synthesized using iron pentacarbonyl as a precursor. Morphology, size, and magnetic properties of the synthesized nanoparticles were determined. The X-ray diffraction results show that the porous tube reactor produced nearly pure iron or maghemite nanoparticles with crystallite sizes of 24 and 29 nm, respectively. According to the scanning mobility particle sizer data, the geometric number mean diameter was 110 nm for iron and 150 nm for the maghemite agglomerates. The saturation magnetization value of iron was 150 emu/g and that of maghemite was 12 emu/g, measured with superconducting quantum interference device (SQUID) magnetometry. A computational fluid dynamics (CFD) simulation was used to model the temperature and flow fields and the decomposition of the precursor as well as the mixing of the precursor vapor and the reaction gas in the reactor. An in-house CFD model was used to predict the extent of nucleation, coagulation, sintering, and agglomeration of the iron nanoparticles. CFD simulations predicted a primary particle size of 36 nm and an agglomerate size of 134 nm for the iron nanoparticles, which agreed well with the experimental data.

Microfluidic synthesis of metal oxide nanoparticles via the nonaqueous method

“…Whilst continuous gas phase processes using e.g. flame pyrolysis (Gröhn et al, 2014;Jossen et al, 2006;Mueller et al, 2003) and hot wall reactors (Ruusunen et al, 2015) are widely applied, a continuous wet chemistry approaches are much less performed (Gruar et al, 2013;Nishioka et al, 2011;Slostowski et al, 2012), although they stand out through milder synthesis conditions and a relatively facile control of particle sizes. A major challenge for the production of metal oxide nanocrystals at larger scale is the realization of homogenous synthesis conditions in the reaction vessel, which is indispensable to achieve a uniform product.…”