Iron Nanoparticle Additives as Burning Rate Enhancers in AP/HTPB Composite Propellants

Abstract

a] 1I ntroductionAmmonium perchlorate (AP) composite propellants are widely used in solid rocket propulsion. Common formulations for AP composite propellants include hydroxyl-terminated polybutadiene (HTPB) as ab inder and fuel, ac urative/plasticizer to solidify the HTPB binder,s ometimes aluminum particles as fuel to increase energy density,a nd sometimes am etal oxide additive to catalyze AP thermal decomposition [1].T he burning rate of AP composite propellants has been shown to be controlled by the concentration of AP,t he size of AP particles, binder type, the type and concentration of any catalyst additives, and the concentration and particle size of any added aluminum fuel (e.g.,R efs. [1-7]);h ence, AP composite propellants can be manipulated for burning rate tailoring by simply altering the proportions of the components and using small percentages of additives which can act as catalysts for condensed and/or gas-phase reactions, ignition sources, and/or provide thermal feedback or sinks.The majority of work focused on catalyst additives for adjusting AP composite propellant burning rate has focused on metal oxides [5-20] (e.g.,F e 2 O 3 ,C uO, TiO 2 )w here metal oxides catalyze the thermal decomposition of AP and therefore increase the burning rate of AP composite propellants. Ferric oxide (Fe 2 O 3 )h as found the most use in commercial AP composite propellants due to its low cost, ease of manufacture, stability/inertness, and ability to generate high and reproducible burning rates [15].T he influence of the size of the catalyst particles has also been considered, where it is thought that smaller particles (e.g., nanoparticles) with higher surface-to-volume ratios have greater catalytic activity.H owever,n anoparticles can be dif-ficult to uniformly introduce into as olid propellant as they tend to agglomerate due to van der Walls and electrostatic forces.An abundance of literature also exists on the use of aluminum as fuel in AP composite propellants (e.g.,R efs. [21][22][23][24]), either as in nanoparticles or micro-sized particles, where aluminum increases energy density and can increase burning rate. Jayaraman et al. [24] have shown that aluminum nanoparticles can increase the burning rate of AP/ HTPB/Al propellants by up to 100 %compared to micro-aluminum. However,J ayaraman et al. also found the effect of Fe 2 O 3 additives as catalysts is mitigated for AP/HTPB/nano-Al propellants relative to AP/HTPB/micro-Al formulation (i.e.,n oa dditional burning rate increase is observed when adding Fe 2 O 3 to propellants containing Al nanoparticles).Interestingly,w ea re not aware of any literature in which iron (Fe) nanoparticles have been investigated as additives for AP compositep ropellants. Fe nanoparticles have several properties that could be advantageous as additives to AP composite propellants. Fe nanoparticles that have been exposed to air have an oxidized Fe 2 O 3 shell which can provide catalysis to AP decomposition at the propellant burning surface in the same manner as purely Fe 2 O 3 particle...

Impact of lattice inclusion of Cu and Fe ions on thermal decomposition characteristics of ammonium perchlorate

“…The doping of AP with transition metals and their oxides has shown to decrease the activation energy and decomposition temperature of AP, thereby acting as good catalysts (Schumacher, 1960;Boldyrev, 2006;Jacobs & Whitehead, 1969;Kishore & Sunitha, 1979). The mechanical mixing of AP with compounds of copper and iron is highly effective in reducing the thermal decomposition of Ammonium perchlorate (Wang et al, 2013;Patil, Krishnamurthy & Joshi, 2008;Chen, Li & Li, 2008b, 2008aAlizadeh-Gheshlaghi et al, 2012;Yang et al, 2014;Liu et al, 2004;Chaturvedi & Dave, 2013;Styborski et al, 2015;Song et al, 2010;Costa et al, 2009).…”

Environmentally safe (chlorine-free): new green propellant formulation based on 2,2,2-trinitroethyl-formate and HTPB

“…13 To achieve this target, numerous researches have been studied based on adding some additives such as metals or nitramines (RDX, HMX, etc.). [14][15][16][17][18] Several groups worldwide have intensively investigated other compounds to substitute AP to overcome its toxicity problems and to enhance the energetic characteristics, sensitivities and thermal properties. [19][20][21] These compounds are based on orthocarbonates, tetrazoles, carbamates, nitrocarbamates, formates, pyrazoles and triazoles.…”

Application of the Energetic Complex [Cu(TNBI)(NH3)2(H2O)] in Heterogeneous Solid Rocket Propellants

“…There are several ways of improving the parameters of such propellants. It is possible to use burning rate modifiers (catocene, butacene, nano-Fe 2 O 3 ) [6][7][8][9], or to apply highly energetic binder compounds like NHTPB, BAMO, GAP etc. [10][11][12].…”