Micropatterning of nanoenergetic films of Bi2O3/Al for pyrotechnics

Abstract

Initiatives have been led by researchers all around the world to deposit and pattern nanoenergetic films (nEFs) using various techniques so that printed energetic circuits can be developed for initiation of detonation. In the first stage of a similar initiative, Bi₂O₃ nano-square tablets (NSTs) with an edge length of ca. 200–300 nm and thickness of ca. 50–100 nm were synthesized on gold-sputtered silicon substrates by a chemical bath deposition process. Gold nanofilms on Si-substrates were found to act as catalytic agents for stable colloidal growth of Bi₂O₃ NSTs. In the absence of a gold catalyst, micro-leaf-shaped structures of Bi₂O₃ were observed to form using the same process. The developed Bi₂O₃ NSTs were sputter-coated with aluminum to produce nEFs on the Si-substrate. The exothermic reactivity of Bi₂O₃/Al nEFs was evaluated at three different aluminum-sputtering thicknesses of 60, 100 and 140 nm, respectively, by TG-DSC measurements taken from 50 to 800 °C at a heating rate of 10 °C min⁻¹ under nitrogen. The nEF formed with 140 nm aluminum sputtering developed the highest heat of reaction, 710 J g⁻¹, at an initiation temperature of 535 °C; when burnt in a constant-volume pressure-cell, this nEF developed a peak pressure of 40.8 MPa and a pressurization rate of 4.08 MPa μs⁻¹. Furthermore, it was possible to pattern the Bi₂O₃/Al nEFs on Si-substrates up to a resolution of ∼5 microns. The high heat of reaction, low initiation temperature and excellent pressure–time characteristics of the nEFs, and their high-resolution micropatterning on Si-substrates make them useful for pyrotechnics.