Capacitively coupled nonthermal plasma synthesis of aluminum nanocrystals for enhanced yield and size control

Abstract

Uniform-size, non-native oxide-passivated metallic aluminum nanoparticles (Al NPs) have desirable properties for fuel applications, battery components, plasmonics, and hydrogen catalysis. Nonthermal plasma-assisted synthesis of Al NPs was previously achieved with an inductively coupled plasma (ICP) reactor, but the low production rate and limited tunability of particle size were key barriers to the applications of this material. This work focuses on the application of capacitively coupled plasma (CCP) to achieve improved control over Al NP size and a ten-fold increase in yield. Different from many other materials, where nanoparticle size is controlled via the gas residence time in the reactor, the Al NP size appeared to depend on the power input to the CCP system. Results indicate that the CCP reactor assembly, with a hydrogen-rich argon/hydrogen plasma, was able to produce Al NPs with diameters tunable between 8 - 21 nm at a rate up ~ 100 mg hr-1. X-ray diffraction indicates that a hydrogen-rich environment results in crystalline metal Al particles. The improved synthesis control of the CCP system compared to the ICP system is interpreted in terms of the CCP’s lower plasma density, as determined by double Langmuir probe measurements, leading to reduced nanoparticle heating in the CCP that is more amenable to nanoparticle nucleation and growth.

Nonthermal Plasma Synthesis of Metallic Ti Nanocrystals

“…Plasmas, as a highly energetic and rapid gas-phase synthesis technique, are paving the way for sustainable, fully electric, and solvent-free synthesis of a variety of functional nanomaterials. Despite extensive research on their applications in elemental and compound semiconductor nanomaterials production [20][21][22][23], few studies have been reported that explore the potential of plasmas for metal nanoparticle syntheses [24][25][26]. Theoretical calculations showed that an atmospheric-pressure thermal plasma with mixture of Ar, H 2 , and TiCl 4 is a feasible route for the production of titanium nanoparticles [27,28].…”