Molecular Dynamics Simulation of the Kinetic Reaction of Nickel and Aluminum Nanoparticles

Henz, Brian J.; Hawa, Takumi; Zachariah, Michael R.

doi:10.21236/ada518421

Cited by 3 publications

(3 citation statements)

References 37 publications

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“…Calculations indicate that the core is under compression (positive pressure on the order of 1000 MPa) and the shell is under tension. A similar trend was also obtained for homogeneously heated oxide-coated aluminum particles . Levitas proposed a melt-dispersion mechanism, which is valid at very high heating rates (>10 6 K/s).…”

Section: Nickel-coated Aluminum Particlessupporting

confidence: 77%

Thermochemical Behavior of Nickel-Coated Nanoaluminum Particles

2013

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Thermochemical behavior of nickel-coated aluminum particles in the size range of 4−18 nm is studied using molecular dynamics simulations. The analysis is carried out in isothermal− isobaric and isochoric-isoenergetic ensembles using an embedded atom method. Emphasis is placed on analyzing the melting points of the core and shell, diffusion of atoms, and intermetallic reactions. The aluminum core melts at a temperature greater than the melting point of a nascent aluminum particle due to the cage-like mechanical constraint imposed by the nickel shell. The melting point of the aluminum core increases from 775 to 1000 K when the core diameter increases from 3 to 12 nm. The melting point of the core is not significantly affected by variations in the shell thickness in the range of 1−3 nm, although the melting point of the shell increases with increasing thickness from a value as low as 1100 K at 1 nm to 1580 K at 3 nm. Melting is followed by diffusion of atoms and energy release due to intermetallic reactions, which result in ignition of the particle in vacuum. For a core diameter of 3 nm, the ignition temperature increases from 800 to 1600 K when the shell thickness increases from 0.5 to 3.0 nm. The diffusion coefficient of aluminum atoms in the nickel shell exhibits an exponential dependence on temperature, with activation energy of 34.7 kJ/mol. The adiabatic reaction temperature of the particle increases from 1650 to 2338 K when the core diameter increases from 3 to 8 nm. The calculated values agree reasonably well with those obtained via thermodynamic energy balance analysis.

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Section: Nickel-coated Aluminum Particlessupporting

confidence: 77%

Thermochemical Behavior of Nickel-Coated Nanoaluminum Particles

2013

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“…[44] Another is the diffusion of Al atoms through physical cracks in the shell. [45,46] Apart from these still-controversial viewpoints, we also believe that the heterogeneous nature of our nanostructure is to be considered, since the DNA can provide a particular thermal signature. After the ignition threshold, the DSC curves are characterized by a gentle reaction profile, which indicates slow reaction kinetics.…”

Section: Methodsmentioning

confidence: 99%

High‐Energy Al/CuO Nanocomposites Obtained by DNA‐Directed Assembly

Séverac

Alphonse

Estève

et al. 2011

Adv Funct Materials

146

108

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Over the next few years, it is expected that new, energetic, multifunctional materials will be engineered. There is a need for new methods to assemble such materials from manufactured nanopowders. In this article, we demonstrate a DNA-directed assembly procedure to produce highly energetic nanocomposites by assembling Al and CuO nanoparticles into micrometersized particles of an Al/CuO nanocomposite, which has exquisite energetic performance in comparison with its physically mixed Al/CuO counterparts. Using 80 nm Al nanoparticles, the heat of reaction and the onset temperature are 1.8 kJ g −1 and 410 °C, respectively. This experimental achievement relies on the development of simple and reliable protocols to disperse and sort metallic and metal oxide nanopowders in aqueous solution and the establishment of specific DNA surface-modification processes for Al and CuO nanoparticles. Overall, our work, which shows that DNA can be used as a structural material to assemble Al/Al, CuO/CuO and Al/CuO composite materials, opens a route for molecular engineering of the material on the nanoscale.

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“…In the DOM mechanism, the Al core of NPs is nearly isothermal due to the NP's small physical dimensions and high thermal conductivity, and Al diffusion through the encapsulating shell restricts the reaction rate between the fuel and surrounding oxide. The outward diffusion of Al is more rapid than the inward diffusion of oxygen, causing the coarsening of the amorphous oxide layer, as shown by MD simulation and experimental observations [119,120]. At a temperature of 770 K, a polymorphic phase transformation of the oxide shell may initiate the nucleation of high-density crystallites [121].…”

Section: Introductionmentioning

confidence: 95%

Investigation of nanoenergetic combustion study of aluminum nanoparticles systems on plasmonic grating platform

Zakiyyan¹

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With renewed interest in energetic materials like aluminum, many fundamental issues concerning the ignition and combustion characteristics at nanoscales remain to be clarified. Aluminum nanoparticles (Al NP) are widely used solid-state fuels in energetic material applications due to the abundance of aluminum and high heat of reaction. The metallic Al core of Al NP must escape an alumina shell to react with oxidizers. The diffusion oxidation mechanism (DOM) of aluminum has been suggested as governing the reaction mechanism, whereby both oxygen and aluminum diffuse through the oxide shell at low heating rates of 10^4-10^6 K/s. However, Al diffusion through the encapsulating shell restricts the reaction rate between the fuel and surrounding oxide. An alternative model is proposed and known as the melt dispersion mechanism (MDM), a rapid thermomechanical mechanism for rapid heating [greater than] 10^6 K/s. This mechanism is driven by the volumetric expansion of rapidly melting Al core which ruptures the oxide shell. MDM has been widely proposed, and we present the first Al NP spallation observed at a particle scale. Plasmonic photothermal heating was needed to facilitate the rapid heating required to initiate the MDM reaction mechanism. A plasmonic grating coupled with an external laser significantly enhances the intensity of photothermal heating experienced by an Al NP. Aluminum, itself, has strong plasmon resonances throughout the visible and ultraviolet spectrum and may be tuned based on Al NP diameter. Our experimental setup encompasses a wide range of available imaging methods to increase the imaging resolution in a table-top optical microscope. A high-resolution camera with a polarization-based scattering method readily identifies whether a particle is metallic or nonmetallic based on the obtained light intensity. Spatiotemporal temperature dependence of Al NP is also observed using fluorescent dyes embedded in a polymer matrix. Finally, the photothermal heating of Al NP in different systems is modeled in COMSOL Multiphysics software using Electromagnetic Waves and Heat Transfer Modules. Based on the simulation, the estimated heating rate can determine the potential mechanism of the observed mechanism. The findings underline the crucial role of heating rates in observing particle spallation through plasmonic enhanced photothermal heating. Combustion of Al NPs is also studied with fluoropolymer and metal-oxide acting as the oxidizer. The current study aims to establish a unified theory accommodating the reaction mechanisms of aluminum particles at micro and nanoscales. The presented works investigate the material constituents starting from individual particle-scale to macro bulk-scale to understand their reaction mechanism better.

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Molecular Dynamics Simulation of the Kinetic Reaction of Nickel and Aluminum Nanoparticles

Cited by 3 publications

References 37 publications

Thermochemical Behavior of Nickel-Coated Nanoaluminum Particles

Thermochemical Behavior of Nickel-Coated Nanoaluminum Particles

High‐Energy Al/CuO Nanocomposites Obtained by DNA‐Directed Assembly

Investigation of nanoenergetic combustion study of aluminum nanoparticles systems on plasmonic grating platform

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