Ignition dynamics and activation energies of metallic thermites: From nano- to micron-scale particulate composites

Hunt, Emily M.; Pantoya, Michelle L.

doi:10.1063/1.1990265

Cited by 87 publications

(46 citation statements)

References 20 publications

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“…If the heat generated within an ignition zone is enough to initiate rapid mixing in the surrounding layers, then the reaction will self-propagate throughout the entire system. This idea has been applied to systems with different microstructures and chemistries [1][2][3], including core-shell particles [4][5][6][7][8], powder compacts [9][10][11][12][13][14], mechanically activated foils and powders [15][16][17][18][19], and vapor-deposited laminate foils [2,[20][21][22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Using magnesium to maximize heat generated by reactive Al/Zr nanolaminates

Overdeep

Livi

Allen

et al. 2015

Combustion and Flame

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a b s t r a c tIn this study, we explore the effect of magnesium content on the ability of reactive nanocomposite foils to generate heat, by comparing three chemistries: Al:Zr, Al-8Mg:Zr, and Al-38Mg:Zr. These correspond to foils with alternating aluminum and zirconium layers where the Al is either pure, an 8 at.%Mg alloy, or a 38 at.%Mg alloy, respectively. Measurements performed in a specially designed bomb calorimeter show that Al-8Mg:Zr foils perform the best, generating the greatest gravimetric heat in air, oxygen, and nitrogen environments. Both Mg-containing foils release a visible plume of particles and vapor upon reacting, which was recorded with a high speed camera. This ejected mass includes Mg vapor and particles of all three metals. Both the vapor and particles oxidize rapidly in air, resulting in single metal-oxide particles. The reacted foils, particularly the Al-8Mg:Zr samples, contain voids and higher levels of oxygen and nitrogen throughout their thicknesses than reacted Al:Zr foils. To explain the higher heats of reaction for the Al-8Mg:Zr foils, we suggest that the out-diffusion and evaporation of Mg generates a high concentration of vacancies that enhance oxygen and nitrogen diffusion throughout the foil, thereby increasing the degree of oxidation and nitridation.

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Section: Introductionmentioning

confidence: 99%

Using magnesium to maximize heat generated by reactive Al/Zr nanolaminates

Overdeep

Livi

Allen

et al. 2015

Combustion and Flame

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“…Aluminum is a favorite choice because of its high reaction enthalpy, abundance, low cost and technological maturity for manufacturing. However for many of these applications, the high theoretical combustion enthalpy of aluminum could not be practically achieved within the required time periods due to long metal ignition delays, particles agglomeration before ignition, slow burning rates and incomplete combustion [5][6]. Powders of metastable aluminum-based alloys have been proposed to address these problems in order to increase burning rates [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Thermal-Chemical Characteristics of Al–Cu Alloy Nanoparticles

et al. 2015

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This work investigated the oxidation, ignition and thermal reactivity of alloy nanoparticles of aluminum and copper (nAlCu) using simultaneous thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) method. The microstructure of the particles was characterized with scanning electron microscope (SEM) and transmission electron microscope (TEM), and the elemental composition of the particles before and after the oxidation was investigated with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD).The particles were heated from room temperature to 1200 o C under different heating rates from 2 to 30 K/min in the presence of air. The complete oxidation process of the nAlCu was characterized by two exothermic and two endothermic reactions, and the reaction paths up to 1200 o C were proposed. An early ignition of nAlCu, in the temperature around 565 o C, was found at heating rates ≥ 8 K/min. The eutectic melting temperature of nAlCu was identified at ~ 546 o C, which played a critical role in the early ignition. The comparison of the reactivity with that of pure Al nanoparticles showed that the nAlCu was more reactive through alloying.

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“…The use of nano-aluminium as fuel enhances ignition sensitivity, i.e. it reduces ignition delay and lowers the ignition temperature [13,16,17].…”

Section: Introductionmentioning

confidence: 99%

The effect of Si–Bi2O3 on the ignition of the Al–CuO thermite

et al. 2011

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The ignition temperature of the Al-CuO thermite was measured using DTA at a scan rate of 50 C.min -1 in a nitrogen atmosphere. Thermite reactions are difficult to start as they require very high temperatures for ignition, e.g. for Al-CuO thermite comprising micron particles it is ca. 940 C. It was found that the ignition temperature is significantly reduced when the binary Si-Bi 2 O 3 system is added as sensitizer. Further improvement is achieved when the reagents are nano-sized powders. For the composition Al + CuO + Si + Bi 2 O 3 (65.3:14.7:16:4 wt %), with all components nano-sized, the observed ignition temperature is ca. 613 C and a thermal runaway reaction is observed in the DTA.

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Ignition dynamics and activation energies of metallic thermites: From nano- to micron-scale particulate composites

Cited by 87 publications

References 20 publications

Using magnesium to maximize heat generated by reactive Al/Zr nanolaminates

Using magnesium to maximize heat generated by reactive Al/Zr nanolaminates

Thermal-Chemical Characteristics of Al–Cu Alloy Nanoparticles

The effect of Si–Bi2O3 on the ignition of the Al–CuO thermite

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