Characterization of Energetic Porous Silicon for a Microelectromechanical System (MEMS)-Based Solid Propellant Microthruster

Supercritically-Dried Porous Silicon Powders with Surface Areas Exceeding 1000 m2/g

“…The super-critical drying technique -a scalable process in itself -can also be applied at the wafer-scale level, for porous silicon thin films attached to wafer substrates, which might also be of benefit for applications such as microthrusters, 6 energetics, 4 energy storage, 8 and RF devices. 30…”

“…2 Many of these utilize the mesoporous powder form of the material (generally after suitable passivation of the reactive silicon hydride internal surface), rather than layers attached to the parent substrate. For applications such as energetics [3][4][5][6] and hydrogen storage, 7 for which the hydride passivation is essential, together with energy storage, in the form of composite Li-ion batteries 8,9 and super-capacitors, 10,11 and the loading and delivery of small molecules and proteins, extremely high surface area can be beneficial; this tends to be more associated with the more microporous forms of the material (having some pore widths <2 nm) or at least mesoporous silicon that contains a high density of small pores (<5 nm).…”

The effect of porosity on energetic porous silicon solid propellant micro-propulsion

“…While the combustion performance of energetic porous silicon is directly affected by the pore size and surface area of the porous silicon, porosity is a much simpler quantity to measure for small area devices. Previous work showed that it is difficult to obtain reliable pore size and pore volume using volumetric analysis based on the Brunauser, Emmett, Teller (BET) method for porous silicon mass below 3 mg [30]. A coupon of four porous silicon devices etched out of a single silicon chip for this study results in 250 μg of porous silicon material, so a minimum of 12 coupons would be required for one BET measurement.…”