Surface-Functionalized Boron Nanoparticles with Reduced Oxide Content by Nonthermal Plasma Processing for Nanoenergetic Applications

Abstract

The development of an in situ nonthermal plasma technology improved the oxidation and energy release of boron nanoparticles. We reduced the native oxide layer on the surface of boron nanoparticles (70 nm) by treatment in a nonthermal hydrogen plasma, followed by the formation of a passivation barrier by argon plasma-enhanced chemical vapor deposition (PECVD) using perfluorodecalin (C 10 F 18 ). Both processes occur near room temperature, thus avoiding aggregation and sintering of the nanoparticles. High-resolution transmission electron microscopy (HRTEM), high-angular annular dark-field imaging (HAADF)-scanning TEM (STEM)-energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) demonstrated a significant reduction in surface oxide concentration due to hydrogen plasma treatment and the formation of a 2.5 nm thick passivation coating on the surface due to PECVD treatment. These results correlated with the thermal analysis results, which demonstrated a 19% increase in energy release and an increase in metallic boron content after 120 min of hydrogen plasma treatment and 15 min of PECVD of perfluorodecalin. The PECVD coating provided excellent passivation against air and humidity for 60 days. We conclude in situ nonthermal plasma reduction and passivation lead to the amelioration of energy release characteristics and the storage life of boron nanoparticles, benefits conducive for nanoenergetic applications.

Experimental synthesis, functionalized modifications and potential applications of monoelemental zero-dimensional boron nanomaterials

“…Typically, an effective modication strategy is to produce core/shell nano-structural derivatives. 79,84,[133][134][135][136][137][138] The derivatives usually consist of 0D boron nanomaterials as the core and other inorganic nanomaterials as the shell. Walton et al prepared boron core silica shell (B@SiO 2 ) nanoparticles, having spherical, monodisperse and water-dispersible features suitable for the aforementioned biomedical applications.…”

“…Agarwal et al reported that the native oxide layer (B 2 O 3 ) on the surface of BNPs (70 nm) was reduced through treatments in a nonthermal hydrogen plasma, followed by forming a passivation barrier (C x F y ) by Ar plasma-enhanced chemical vapor deposition using peruorodecalin C 10 F 18 . 135 Both steps occur near RT, which avoids aggregation and sintering of the core-shell surface-functionalized BNPs (Fig. 11b).…”

“…175 Boron has potential applications in energetic materials as an additive fuel. 98,135 Laser ignition and combustion experimental systems were used to study the potential combustion mechanism of nano-sized B (Fig. 21).…”

Nanoenergetic Materials: Enhanced Energy Release from Boron by Aluminum Nanoparticle Addition

“… 5 − 8 The melting of the oxide shell before the solid core clogs the pores leads to particle agglomeration and acts as a diffusion barrier to the incoming oxidizer, thus delaying the boron (B) oxidation. 1 , 5 Attempts to overcome these limitations include surface functionalization of B by organic compounds, 9 − 14 reduction of the oxide, followed by surface passivation using nonthermal plasma processing, 15 and coating with metals to form composites and metal borides by ball milling and high-temperature sintering methods. 16 − 23 Functionalization with organic compounds results in the reduction of the amount of energy released per unit mass due to the presence of less energetic materials on the B surface.…”

Enhancing Mechanical and Combustion Performance of Boron/Polymer Composites via Boron Particle Functionalization

“…For example, Pickering et al reported the room-temperature synthesis of organo-capped B nanoparticles from liquid B precursors. B particles were coated with metal fluoride and fluorocarbon by a solution-based precipitation method and nonthermal plasma processing, and they show better combustion performance. , For covalent functionalization of B, it has been reported that surface-functionalized B particles with alkyl chains are more stable in air and have better dispersion in nonpolar solvents, − but these alkyl-functionalized B particles have not been incorporated in HTPB or other polymer composites. As for B/HTPB composites, modifications on B particles with fluorides and glycidyl azide polymer were shown to tailor the combustion behavior of the B/AP/HTPB propellant, , but the interactions between the B particles and HTPB were not discussed, and the effects on mechanical properties were not investigated.…”