Electrospray Formation of Gelled Nano-Aluminum Microspheres with Superior Reactivity

Abstract

Nanometallic fuels with high combustion enthalpy, such as aluminum, have been proposed as a potential fuel replacement for conventional metallic fuel to improve propellant performance in a variety of propulsive systems. Nevertheless, nanometallic fuels suffer from the processing challenges in polymer formulations such as increased viscosity and large agglomeration, which hinder their implementation. In this letter, we employ electrospray as a means to create a gel within a droplet, via a rapid, solvent evaporation-induced aggregation of aluminum nanoparticles, containing a small mass fraction of an energetic binder. The gelled aluminum microspheres were characterized and tested for their burning behavior by rapid wire heating ignition experiments. The gelled aluminum microspheres show enhanced combustion behavior compared to nanoaluminum, which possibly benefits from the nitrocellulose coating and the gelled microstructure, and is far superior to the corresponding dense micrometer-sized aluminum.

Assembly and reactive properties of Al/CuO based nanothermite microparticles

“…At higher loading, performance degrades because energy content is degrading, and possibly that we have reached a limit where too much gas generation only serves to dissipate the reactant from each other resulting in reaction quenching. This latter explanation is consistent with our observation and explanation that localization of the heat release explains the superior reactivity of gelled Al microspheres in our previous work [33]. Fig.…”

“…This work builds on some of our prior work in which electrospinning (a close cousin to electrospray) was first used to create thermite based nanofiber mats [14], and more recently an electrospray approach was employed to produce nanoaluminum microspheres [33]. By changing either particle loading or polymer concentration, we were able to tune the size and composition of the aluminum microparticles, consequently the burning performance of the Al/NC composites was easily tuned.…”

Modeling the Pressure Generation in Aluminum‐Based Thermites

“…9mm 3 ). Ap ressure up to 100 MPa can be measured by ah igh-frequency pressure transducer (Kistler 601 H) on the back of the reactor and connected to aK istler charge amplifier (5018 type).…”

“…Alumino-thermite is an oxidation-reduction reaction involving am etal (fuel) and am etallic oxide (or possibly an on-metallic oxide) that forms as table product after reaction.Thermite materials have been actively investigated for aw ide range of potential applications including railroad welding, materials processing to form refractory materials, additives in propellants, explosives and pyrotechnics [1][2][3], and more recently also for micro initiation [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20],e nvironmentally clean primers, and in situ welding [21].Among the numerous possible exothermic metal/oxide pairs listed in the literature [22],t he most investigated ones mix Al with MoO 3 ,C uO, Bi 2 O 3 ,F e 2 O 3 ,M nO 2 ,W O 3 ,a nd I 2 O 5 .F or the last two decades most of the research efforts aimed at reducing metal and oxide components size, improving their intimacy,t oi ncrease the reaction rate and decrease the ignition delay while improving safety.More recently,t hermite materials were also considered to produce gas species or pressure bursts, opening new potential fields of application such as pressure mediated molecular delivery [23,24],b iological agent inactivation [25][26][27],h ydrogen production [28,29],o rp ropulsion systems [7][8][9].Af ew teams demonstrated experimentally that Al/Bi 2 O 3 and, to al esser extent, Al/I 2 O 5 mixtures generate the highest pressure pulses [27,30,31] in comparison with other thermites. Martirosyan [31] considered tha...…”

A new strategy for the fabrication of high performance reactive microspheres via energetic polyelectrolyte assembly

“…To conrm this point, the morphology of the combustion products of the Al/Fe 2 O 3 NEMs was examined by SEM (Fig. S7 †) 13,[36][37][38] Additionally, at low GEPEC content, the performance is improved with increasing the GEPEC content, possibly due to the presence of a ready source of low temperature, energetic, generating gas so as to minimize nanostructure loss. At higher loading, performance degrades mainly because the total energy is degraded by a large margin, which is the basis of the NEMs.…”