Post-Plasma SiOx Coatings of Metal and Metal Oxide Nanoparticles for Enhanced Thermal Stability and Tunable Photoactivity Applications

Abstract

The plasma-based aerosol process developed for the direct coating of particles in gases with silicon oxide in a continuous chemical vapor deposition (CVD) process is presented. It is shown that non-thermal plasma filaments induced in a dielectric barrier discharge (DBD) at atmospheric pressure trigger post-DBD gas phase reactions. DBD operating conditions are first scanned to produce ozone and dinitrogen pentoxide. In the selected conditions, these plasma species react with gaseous tetraethyl orthosilicate (TEOS) precursor downstream of the DBD. The gaseous intermediates then condense on the surface of nanoparticles and self-reactions lead to homogeneous solid SiOx coatings, with thickness from nanometer to micrometer. This confirms the interest of post-DBD injection of the organo-silicon precursor to achieve stable production of actives species with subsequent controlled thickness of SiOx coatings. SiOx coatings of spherical and agglomerated metal and metal oxide nanoparticles (Pt, CuO, TiO2) are achieved. In the selected DBD operating conditions, the thickness of homogeneous nanometer sized coatings of spherical nanoparticles depends on the reaction duration and on the precursor concentration. For agglomerates, operating conditions can be tuned to cover preferentially the interparticle contact zones between primary particles, shifting the sintering of platinum agglomerates to much higher temperatures than the usual sintering temperature. Potential applications for enhanced thermal stability and tunable photoactivity of coated agglomerates are presented.

Review on water electro-sprays and applications of charged drops with focus on the corona-assisted cone-jet mode for High Efficiency Air Filtration by wet electro-scrubbing of aerosols

“…3 and 3.3.3). Plasma-based aerosol processes with droplet injection in plasma are developed for SiO X or polymer particle production and deposition, as coating processes (Fanelli et al, 2014;Brunet et al, 2017), to trigger either the polymerization of organic monomer precursor (Ward et al, 2003a;Tatoulian et al, 2006) or sol-gel reactions for oxide formation from organo-metal precursor, as reported by droplet injection in (Ward et al, 2003b;Jacopo et al, 2017) and downstream atmospheric pressure plasmas (Borra et al, 2012;Post et al, 2016). For more details, the reader can refer to a special session on the topic held in EAC 2016.…”

Coating of Gas‐Borne Nanoparticles with SiO2 in a Plasma‐Assisted CVD Process at Ambient Conditions

“…Dabei scheinen sich zunächst Zwischenprodukte zu bilden, die im Gegensatz zu TEOS bei diesen Bedingungen auch auf den Partikeln kondensieren können [5]. Tatsächlich wurde zuvor beobachtet, dass es eine Diskrepanz zwischen der mit einem SMPS gemessenen und der auf TEM-Aufnahmen erkennbaren Schichtdicke gibt [5]. Ebenso resultiert die Kondensation von Spezies auf den Partikeln nicht in der sofortigen Bildung einer festen Schicht.…”

Thin insulating film deposition on copper by atmospheric‐pressure plasmas

“…They found that the corrosion and adhesion properties are promising to satisfy the aircraft industry requirements. Alfred et al achieved homogeneous SiO x coatings on metal and metal oxide nanoparticles to enhance their thermal stability. Besides, siloxane layer with excellent hardness, optical, and dielectric properties, provides a variety of applications for optics and microelectronics .…”