A Decade of Porous Silicon as Nano‐Explosive Material

We present a comprehensive investigation into the tunable combustion of on‐chip porous silicon energetic materials. The exothermic reaction occurs between high surface area nanoscale porous silicon and a solution‐deposited sodium perchlorate oxidizer that penetrates each pore. The resulting burn rates spanned three orders of magnitude, from 5.2 to 1950 m s−1. Material properties of the porous silicon films were characterized using gas adsorption porosimetry, SEM, and profilometry, over specific surface areas between 191 and 901 m2 g−1, and porosities between 49 and 80 %. Combustion events were characterized using high speed imaging and bomb calorimetry. Results revealed that combustion depended on several material properties including surface area and porosity of the porous silicon substrate, with the peak flame speed occurring at 895 m2 g−1 specific surface area, 3.32 nm pore size, and 72 % porosity. Measured heat of combustion increased with porosity over the range of 65–75 %, up to 22.5 kJ g−1 of porous silicon at 75 % porosity. These measurements along with gravimetric determinations of oxidizer pore loading suggest that the system was typically fuel rich, with macroscopic morphology and porous silicon film mechanical integrity generally limiting the realistic range of porosity values to less than stoichiometric conditions.

Section: Resultsmentioning

confidence: 92%

“…A sample of images for flame speed analysis from Set 4 is given in Figure 2. In the past, potential errors have been noted for flame speed analysis due to inconsistencies or “jumps“ in the reaction front 16. In this study care was taken to analyze only steady propagation fronts, similar to that in Figure 2.…”

Section: Resultsmentioning

confidence: 99%

Combustion and Material Characterization of Highly Tunable On‐Chip Energetic Porous Silicon

Piekiel

Morris

Churaman

et al. 2014

“…The explosive behavior of pSi films, impregnated by an oxidizing agent, has been recognized and steadily investigated since 1992 [2].T he behavior originates from the very high internal surface area of pSi (in the order of 800 m 2 per gram) which permits av ery intimate mixture between the oxidizinga gent and the fuel (silicon), leading to materials that are stable at room temperature and are able to react explosively upon applicationo fa ne nergy stimulus. Indeed, pSi energetic materials prepared in this way are sensitive to aw ide variety of stimuli.…”

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confidence: 99%

“…Indeed, pSi energetic materials prepared in this way are sensitive to aw ide variety of stimuli. Methodso fi nitiation thath ave been reported include heating using for example ah otplate [3] or ah ot bridge-wire [4,5],m echanical stimulus (such as scratching the surface or light friction) [6],o rb y an electrical spark [6].A dditionally,l aser ignition of pSi energetic materials has been reported using av ariety of wavelengths and laser fluences [6][7][8][9].I th as also been observed in several reports that pSi energetic materials are highly sensitive to initiation by weak mechanical stimuli such as scratching or mechanical fracture [2].…”

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confidence: 99%

“…Av arietyo fo xidizing agents (typicallyn itrate or perchlorate salts) have beens hown to react energetically with pSi, however SP has emerged as the oxidizer of choice since it delivers the most powerful and consistent energetic reaction [2].C onveniently,c ontrolling the material properties of the pSi substrate (by tuningt he etching conditions) permitsc ontrolo ver the stoichiometry of the system by limiting the volume of the pores available to be filled.The burning rate of pSi energetic films has been reported from as higha s% 3600 ms À1 [15] to less than 1ms À1 [16].T he choice of oxidizing agent, porosity,p ore depth, and pore diametera re all interdependent factors, which governt he burning rate of the system under investigation.…”

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confidence: 99%

See 1 more Smart Citation

Sensitiveness of Porous Silicon‐Based Nano‐Energetic Films

Plummer

Кузнецов

Gascooke

et al. 2016

Nanoporous silicon (pSi) films on a silicon wafer were loaded with sodium perchlorate and perfluoropolyether (PFPE) oxidizing agents. Sensitiveness to impact, friction and electrostatic discharge (ESD) of the resulting energetic thin films were investigated. It was observed that pSi loaded with perchlorate was sensitive at the lowest limit of detection for the available equipment (<4.9 J impact energy, <5 N friction force, and <45 mJ ESD spark energy). When loaded with PFPE the material was very sensitive to impact (<4.9 J), moderately sensitive to ESD (between 45 and 100 mJ) and insensitive to friction (>360 N). pSi loaded with either perchlorate or PFPE displayed behavior during sensitiveness testing similar to other primary explosive materials.

Combustion of Energetic Porous Silicon Composites Containing Different Oxidizers

Abraham

Piekiel

Morris

et al. 2015

We present a quantitative investigation of combustion of on‐chip porous silicon (PS) energetic materials using oxidizers with improved moisture stability and/or minimized environmental impact compared to sodium perchlorate (NaClO4). Material properties of the PS films were characterized using gas adsorption porosimetry and profilometry to determine specific surface area, porosity, and etch depth. PS energetic composites were formed using melt‐penetrated or solution‐deposited oxidizers into the pores. Combustion was characterized by high speed imaging and bomb calorimetry. The flame speeds quantified for PS/sulfur and PS/nitrate systems varied in the ranges of 2.9–3.7 m s−1and 3.1–21 m s−1, respectively. The experimental combustion enthalpies are reported for different oxidizer systems in both inert and oxidizing environments. For the PS/sulfur and the PS/nitrate systems, the experimental heats of combustion were comparable to those calculated for the thermodynamic equilibrium and taking into account an increased reactivity of PS due to the hydrogen terminated silicon surface.