Fuel-rich aluminum–nickel fluoride reactive composites (original) (raw)
Related papers
Investigation of the Effect of Aluminum Powder on the Combustion Rate of the Composite
Crystals
This article discusses the combustion of high-energy systems based on the oxidizers ammonium nitrate, potassium nitrate, and a mixture of highly active aluminum grade PAP-1 under conditions of a deficiency or excess oxidant α, under a pressure reduction in the range of 0.1–3 MPa. The objective of this study is to develop materials for the production of high-energy compositions based on oxidizers of ammonium and potassium nitrate, fuel binder, and metallic fuel in the form of aluminum powders ASD-6 and PAP-1. The influence of the amount of excess oxidizer, the amount of metallic fuel, and the grade of aluminum on the rate and completeness of combustion of a high-energy composition have been studied. Experiments were carried out on the studied high-energy systems, depending on the grade of aluminum used and the excess of the oxidizing agent α, and the influence of pressure on the burning rate. The compositions of high-energy compositions based on highly active aluminum with the highes...
Reactive Ni–Al-Based Materials: Strength and Combustion Behavior
Metals, 2021
The effect of PTFE, continuous boron, and tungsten fibers on the combustion behavior and strength of reactive Ni–Al compacts was examined in this study. The introduction of continuous fibers into Ni–Al compacts according to the developed scheme was found to increase the flexural strength from 12 to 120 MPa. Heat treatment (HT), leading to chemical interaction of the starting components, increases the strength of compacts at temperatures not exceeding 550 °C. The combination of reinforcement and HT significantly increases the strength without reducing reactivity. Experimental results showed that strength and combustion rate increase with the reduction in PTFE to 1 wt % in Ni–Al compacts. A favorable effect of the addition of PTFE from 5 to 10 wt % on the reduction of the threshold for the shock-wave initiation of reactions in Ni–Al was established. The obtained results can be used to produce reactive materials with high mechanical and energy characteristics.
Nano Aluminum Energetics: The Effect of Synthesis Method on Morphology and Combustion Performance
Propellants, Explosives, Pyrotechnics, 2011
Nanoscale aluminum based energetic composites were prepared using polytetrafluoroethylene (PTFE) as an oxidizer, and optimized according to the maximum experimentally observed flame propagation rate in an instrumented burn tube. Optimization of the aluminum-based composites was performed using nanometric aluminum from two manufacturers, Argonide Corporation and Novacentrix, and the combustion results represent the first direct comparison of these two materials in a burn tube configuration. Argonide aluminum was found to consist of many fused spheres of nano aluminum mixed with some larger micron sized particles. Novacentrix aluminum consisted of spherical particles with a closer particle size distribution. The propagation rate optimized wt.-% aluminum powder values were 50 and 44.5 for Novacentrix and Argonide, respectively. At the optimized conditions, the time to steady propagation for both Argonide and Novacentrix were similar, however the startup time for the Novacentrix based mixtures was more sensitive to changes in the mixture ratio. The presence of micron sized aluminum and lower surface area, but higher active content in the Argonide mixtures resulted in lower propagation rates, pressurization rates and peak pressures but higher total impulse values. It was found that peak pressure is not the sole determining factor in propagation rate, but the highest pressurization rates correlate with propagation rate.
Journal of Applied Physics, 2013
Metal-based reactive composites have great potential as energetic materials due to their high energy densities and potential uses as structural energetic materials and enhanced blast materials however these materials can be difficult to ignite with typical particle size ranges. Recent work has shown that mechanical activation of reactive powders increases their ignition sensitivity, yet it is not fully understood how the role of microstructure refinement due to the duration of mechanical activation will influence the impact ignition and combustion behavior of these materials. In this work, impact ignition and combustion behavior of compacted mechanically activated Ni/Al reactive powder were studied using a modified Asay shear impact experiment where properties such as the impact ignition threshold, ignition delay time, and combustion velocity were identified as a function of milling time. It was found that the mechanical impact ignition threshold decreases from an impact energy of greater than 500 J to an impact energy of $50 J as the dry milling time increases. The largest jump in sensitivity was between the dry milling times of 25% of critical reaction milling time (t cr ) (4.25 min) and 50% t cr (8.5 min) corresponding to the time at which nanolaminate structures begin to form during the mechanical activation process. Differential scanning calorimetry analysis indicates that this jump in the sensitivity to thermal and mechanical impact is dictated by the formation of nanolaminate structures, which reduce the temperature needed to begin the dissolution of nickel into aluminum. It was shown that a milling time of 50%-75% t cr may be near optimal when taking into account both the increased ignition sensitivity of mechanical activated Ni/Al and potential loss in reaction energy for longer milling times. Ignition delays due to the formation of hotspots ranged from 1.2 to 6.5 ms and were observed to be in the same range for all milling times considered less than t cr . Combustion velocities ranged from 20-23 cm/s for thermally ignited samples and from 25-31 cm/s for impacted samples at an impact energy of 200-250 J. V C 2013 AIP Publishing LLC. [http://dx.
Combustion of activated aluminum
Combustion and Flame, 2006
Combustion of activated aluminum was studied by four different methods: microscopic imaging of the preignition process, digital imaging of the combustion process at pressures up to 64 bar in air, nitrogen, and carbon dioxide, TGA, and DSC. Activation by three fundamentally different methods was found effective in enhancing both the ignitability and the burn rate. The complex fluoride coating prevented agglomeration completely in all stages of combustion, while the nickel and cobalt coatings promoted agglomeration of aluminum oxide at combustion, but prevented the agglomeration of the aluminum metal before combustion. Nickel coating catalyzed aluminum nitride formation, accelerating burn rate more than other coatings in air and in nitrogen, while complex fluoride coating was most effective in carbon dioxide. Carbon coagulation in carbon dioxide quenched burning in many cases at higher pressures than 8 bar. The complex fluoride activation accelerated combustion in CO 2 extremely effectively, but did not prevent carbon shell formation and subsequent quenching at high pressures. Ni coating negated the effects of carbon coagulation in CO 2 , but enhanced the burn rate only slightly. Co coating reduced the carbon shell formation, but did not accelerate combustion in CO 2 . Only the Ni coating applied in large amounts promoted combustion in nitrogen.
Aluminum Burn Rate Modifiers Based on Reactive Nanocomposite Powders
Propellants, Explosives, Pyrotechnics, 2010
Aluminum powders have long been used in reactive materials for such applications as propellants, pyrotechnics and explosives. Aluminum has a high enthalpy of combustion but relatively low combustion rate. Addition of reactive nanocomposites can increase the burn rate of aluminum and thus the overall reaction rate. Replacing a small fraction of the fuel by a nanocomposite material can enhance the reaction rate with little change to the thermodynamic performance of the energetic formulation. This research showed the feasibility of the above concept using nanocomposite powders prepared by Arrested Reactive Milling (ARM), a scalable "top-down" technique for manufacturing reactive nanocomposite materials. The nanocomposite materials used in this study were 2B+Ti, and Al-rich 8Al+3CuO, and 8Al+MoO 3 . The reactive nanocomposites were added to micron sized aluminum powder and the mixture was burned in a constant volume chamber. The combustion atmosphere was varied using oxygen, nitrogen, and methane. The resulting pressure traces were recorded and processed to compare different types and amounts of modifiers.
COMPARISON OF MECHANICAL AND THERMAL IGNITION CHARACTERISTICS FOR REACTIVITY ENHANCED Ni∕Al POWDERS
AIP Conference Proceedings, 2009
have recently been made to understand the ignition mechanism of gasless reactive systems. It has been known that processes such as high-energy ball milling can enhance reactivity through extensive plastic deformation and introduction of crystal defects in the material. Reducing the particle size of the constituent materials to nano-scales also enhances reactivity. However, the effect of such reactivity enhancing processes on ignition mechanisms is not well known. Mixtures of micron size Ni/Al powders, nano-scale Ni/Al powders, and ball milled Ni/Al powders are studied. Differential thermal analysis (DTA) was used to study thermal ignition properties. Ignition by mechanical stimulus was studied by impacting samples with a projectile from a gas gun. DTA showed the ball-milled materials reacted at a temperature below the melting point of Al However these materials could not be ignited through mechanical means. The nano-mixtures reacted at higher temperature than the ball-milled in the DTA, but were readily ignited through mechanical stimulation. This indicates reactivity enhancement affects the thermal and mechanical ignition mechanisms in different ways.
Effect of surface coatings on aluminum fuel particles toward nanocomposite combustion
Surface and Coatings Technology, 2013
Flame front velocity (FFV) of three energetic material composites was measured in order to understand the effects of surface functionalization on aluminum reactivity. Composites were prepared using molybdenum trioxide (MoO 3 ) and aluminum (Al) fuel particles with and without surface functionalization. The surface functionalization consisted of a 5-nm-thick layer (35% by weight) of perfluorotetradecanoic acid (PFTD) bonded to the Al 2 O 3 surface of the Al particles. The first composite consisted of Al functionalized with PFTD and MoO 3 , the second consisted of Al with MoO 3 and added PFTD particles to the same weight percentage as in the Al functionalized PFTD, and the third composite consisted of Al with MoO 3 . The results showed a dramatic increase in FFV from 100 to 500 m/s resulting from the surface functionalization. The results of the experiments show that the surface functionalized Al composite (Al-PFTD/MoO 3 ) has a reaction rate 2× than that of the simple Al/MoO 3 and 3.5× than that of the Al/MoO 3 /PFTD composite.
Combustion and Flame, 2018
Metallized propellants typically produce large agglomerates that result in two-phase flow losses. Tailoring composite metal fuel particles can improve ignition and combustion characteristics while reducing product droplet sizes. In this work, mechanically activated (MA) aluminum (Al) and magnesium (Mg) powders are synthesized, characterized and compared to magnalium (Mag) alloy, neat Al, neat Mg and their physical mixtures (PM) at the same 1:1 mass ratio as MA and Mag powders. CO 2 laser ignition tests showed that the MA powders are more reactive than those of Mag and exhibit particle fragmentation upon ignition. Mag powders only show fragmentation and microexplosions at high heating rates. The burning rates of the ammonium perchlorate/hydroxyl-terminated polybutadiene composite propellants containing MA powders were the highest, compared to Mag, neat Al, PM and neat Mg in decreasing order. High-speed imaging of the propellants and product collection showed that MA, Mg and Mag powders produce much smaller agglomerates than neat Al or PM at lower pressures due to fragmentation and Mg vaporization. However, the microexplosion tendency of the MA and Mag particles in the propellants was reduced at higher pressures due to reduced vapor bubble growth. Out of all the materials investigated, MA particles provide the best combination of burning rate and product sizes.