Continuous-Flow Synthesis of Ni(0) Nanoparticles Using a Cone Channel Nozzle or a Micro Coaxial-Injection Mixer

Abstract

To synthesize nickel(0) nanoparticles by wet chemical reduction using hydrazine with an average size distribution below 100 nm, two different reactor concepts were developed. With a cone channel nozzle, the reactant solutions were sprayed into a batch for further processing and reduction at elevated temperatures. Another concept uses a microcoaxial injection mixer connected to a heated tube to establish a fully continuously operating reactor. To shorten the time for reduction of the nickel, salt temperatures up to 180°C are applied. To avoid uncontrolled residence time, the whole system was pressurized up to 80 bar. Approximately 80 L reactant solution, i.e., 1 kg nickel(0) nanoparticles, could be processed within 30 h.

Synthesis of silver nanoparticles in a microfluidic coaxial flow reactor

“…The process for synthesising nickel NPs quickly blocked commercially available microstructured mixers and the coaxial-injection mixer was used in a pilot plant scale process mainly because it could avoid fouling and blockage issues. 28 Synthesis of silver NPs using silver nitrate, sodium borohydride (with sodium hydroxide) and trisodium citrate in a coaxial ow reactor in this study has not been reported in the literature. Shirtcliffe et al reported the synthesis of silver nanoparticles using sodium borohydride and sodium hydroxide as a reducing agent for silver nitrate using a PTFE ow chamber and also using Eppendorf pipettes to mix reagents directly into plastic cuvettes.…”

“…[21][22][23] One type of design that alleviates the occurrence of fouling is the coaxial ow reactor (CFR) which allows an inner stream of reagent to be surrounded by an outer stream, creating a reaction interface between the streams. 15,16,[24][25][26][27][28] The CFR is less susceptible to fouling because the reduction of precursor ions and nucleation of metal NPs occur at the interface between the inner and outer streams, rather than near the channel walls. This reduction in fouling relies on the ow prole of the channel remaining in a stable laminar regime.…”

Micro Droplet Formation towards Continuous Nanoparticles Synthesis

“…There is a large number of reports showing potential application of micro flow systems for continuous nanoparticles synthesis [ 6 , 21 , 22 , 23 , 24 ], composite materials [ 25 , 26 , 27 , 28 , 29 , 30 ], as well as for metal ion extraction and separation [ 31 ].…”

Ultrasound-Assisted Hydrazine Reduction Method for the Preparation of Nickel Nanoparticles, Physicochemical Characterization and Catalytic Application in Suzuki-Miyaura Cross-Coupling Reaction

“…Moreover, the rapid (100-200 m/s) liquid microjets penetrate into the voids and their impact To understand the effect of the ultrasound treatment on the nucleation and growth steps of the nickel crystals and to find out the reason for the generation of the crystallites in close to constant sizes and for the delayed synthesis of the metallic nickel at 5 • C, detailed knowledge about the formation mechanism of the Ni nanoparticles is indispensable. Nevertheless, the formation mechanism is still not clear in every detail, in spite of the intense research [23,[50][51][52]. In the most accepted mechanistic model, the nickel-hydrazine complexes with different hydrazine contents are formed first, then the thermodynamically more stable nickel(II) hydroxide is evolved from the reaction of the hydrazine complex and the alkali additive.…”