Importance of Phase Change of Aluminum in Oxidation of Aluminum Nanoparticles

Rai, A.; Lee, Donggeun; Park, Kihong; Zachariah, Michael R.

doi:10.1021/jp0373402

Cited by 143 publications

(126 citation statements)

References 10 publications

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“…These results are in qualitative agreement with experiments in Ref. 26 on oxide fracture of Al nanoparticles due to the melting of Al during relatively slow heating. As it will be shown in Sec.…”

Section: Large Particles and Slow Heatingsupporting

confidence: 82%

“…͑2͒ If melting of an Al nanoparticle covered by an amorphous film occurs during slow heating, 26 low stress ͑strain͒ growth rate takes place. This will reduce the ultimate strength of the thick defect-containing oxide film ͑due to strong strain rate dependence͒ and the pressure in the particle.…”

Section: Large Particles and Slow Heatingmentioning

confidence: 99%

“…Pressure in molten aluminum will also slowly reduce and the liquid will slowly flow through the cracks without spallation and thus dispersion of the entire film and Al as observed experimentally. 26 Melt will be quickly covered by a new oxide film. There is some acceleration of oxidation during this process followed by traditional diffusion-controlled mechanisms for further oxidation.…”

Section: Large Particles and Slow Heatingmentioning

confidence: 99%

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Mechanochemical mechanism for fast reaction of metastable intermolecular composites based on dispersion of liquid metal

Levitas

Asay

Son

et al. 2007

Journal of Applied Physics

143

223

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An unexpected mechanism for fast reaction of Al nanoparticles covered by a thin oxide shell during fast heating is proposed and justified theoretically and experimentally. For nanoparticles, the melting of Al occurs before the oxide fracture. The volume change due to melting induces pressures of 1–2 GPa and causes dynamic spallation of the shell. The unbalanced pressure between the Al core and the exposed surface creates an unloading wave with high tensile pressures resulting in dispersion of atomic scale liquid Al clusters. These clusters fly at high velocity and their reaction is not limited by diffusion (this is the opposite of traditional mechanisms for micron particles and for nanoparticles at slow heating). Physical parameters controlling the melt dispersion mechanism are found by our analysis. In addition to an explanation of the extremely short reaction time, the following correspondence between our theory and experiments are obtained: (a) For the particle radius below some critical value, the flame propagation rate and the ignition time delay are independent of the radius; (b) damage of the oxide shell suppresses the melt dispersion mechanism and promotes the traditional diffusive oxidation mechanism; (c) nanoflakes react more like micron size (rather than nanosize) spherical particles. The reasons why the melt dispersion mechanism cannot operate for the micron particles or slow heating of nanoparticles are determined. Methods to promote the melt dispersion mechanism, to expand it to micron particles, and to improve efficiency of energetic metastable intermolecular composites are formulated. In particular, the following could promote the melt dispersion mechanism in micron particles: (a) Increasing the temperature at which the initial oxide shell is formed; (b) creating initial porosity in the Al; (c) mixing of the Al with a material with a low (even negative) thermal expansion coefficient or with a phase transformation accompanied by a volume reduction; (d) alloying the Al to decrease the cavitation pressure; (e) mixing nano- and micron particles; and (f) introducing gasifying or explosive inclusions in any fuel and oxidizer. A similar mechanism is expected for nitridation and fluorination of Al and may also be tailored for Ti and Mg fuel.

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Section: Large Particles and Slow Heatingsupporting

confidence: 82%

Section: Large Particles and Slow Heatingmentioning

confidence: 99%

Section: Large Particles and Slow Heatingmentioning

confidence: 99%

See 1 more Smart Citation

Mechanochemical mechanism for fast reaction of metastable intermolecular composites based on dispersion of liquid metal

Levitas

Asay

Son

et al. 2007

Journal of Applied Physics

143

223

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show abstract

“…The computed reaction times are given in figure 9 and illustrate that the time required for separate nanoparticles to react has a power law relationship between nanoparticle volume (3) and surface area (2). This implies that not only will the reaction temperature be higher, but it will occur more rapidly with decreases in particle size, to a power of about 2.5.…”

Section: Time (Ps)mentioning

confidence: 99%

“…Some of these properties, including increased reactivity (1), are due to the high surface area to volume ratio of nanoparticles. With that in mind, nanoparticles may provide enhanced energy release rates for explosive and propellant reactions (2).…”

Section: Introductionmentioning

confidence: 99%

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

Henz¹,

Hawa²,

Zachariah³

2010

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Approved for public release; distribution unlimited. ii REPORT DOCUMENTATION PAGEForm Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) March 20102. REPORT TYPE ARL-TR-5134 SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution unlimited. SUPPLEMENTARY NOTES ABSTRACTMolecular dynamics simulations are used to simulate the kinetic reaction of nickel (Ni) and aluminum (Al) particles at the nanometer scale. The effect of particle size on reaction time and temperature for separate nanoparticles is considered as a model system for a powder metallurgy system. Coated nanoparticles in the form of Ni-coated Al nanoparticles and Al-coated Ni nanoparticles are also analyzed as a model for nanoparticles embedded within a matrix. The differences in melting temperature and phase change behavior, e.g., the volumetric expansion of Al between Al and Ni is expected to produce differing results for the coated nanoparticle systems. For instance, the volumetric expansion of Al upon melting is expected to produce large tensile stresses and possibly rupture in the Ni shell for Ni-coated Al. Simulation results showed that the sintering time for separate and coated nanoparticles was nearly linearly dependent upon the number of atoms or volume of the sintering nanoparticles. We also found that nanoparticle size and surface energy was an important factor in determining the adiabatic reaction temperature for both systems at nanoparticle sizes of less than 10 nm in diameter. iii SUBJECT TERMS

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Key Attributes of Nanoscale Materials and Special Functionalities Emerging from them

Mukhopadhyay

2011

Nanoscale Multifunctional Materials

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Importance of Phase Change of Aluminum in Oxidation of Aluminum Nanoparticles

Cited by 143 publications

References 10 publications

Mechanochemical mechanism for fast reaction of metastable intermolecular composites based on dispersion of liquid metal

Mechanochemical mechanism for fast reaction of metastable intermolecular composites based on dispersion of liquid metal

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

Key Attributes of Nanoscale Materials and Special Functionalities Emerging from them

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