Thermal investigations of nanoaluminum/perfluoropolyether core–shell impregnated composites for structural energetics

Kettwich, Sharon C.; Kappagantula, Keerti; Kusel, Bradley S.; Avjian, Eryn K.; Danielson, Seth T.; Miller, Hannah A.; Pantoya, Michelle L.; Iacono, Scott T.

doi:10.1016/j.tca.2014.07.016

Cited by 26 publications

(19 citation statements)

References 16 publications

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“…As such, we have been investigating the utility of preparing metastable matrix composites utilizing a core/shell formulation approach comprising of nanometer-sized aluminum (nAl) as the fuel (the core) and a physio-adsorbed fluoropolymer coating, specifically a class of fluoropolymers called perfluoropolyethers (PFPEs) [4] as the oxidizer (the shell). These energetic composites have included postmachinable epoxy-based thermoset molds [5,6], electrospun polystyrene microfibers [7], and melt-processed fluoropolymer thermoplastics [8]. Overall, these systems are limited to the amount of nAl loading due to the poor metal interface with an organic-based matrix.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Thermal Analysis of Blended Nanoaluminum/Fluorinated Polyether-Segmented Urethane Composites

2019

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The thermally induced reaction of aluminum fuel and a fluoropolymer oxidizer such as polytetrafluoroethylene (via C-F activation) has been a well-studied thermite event for slow-burning pyrolants among a multitude of energetic applications. Generally, most metallized thermoplastic fluoropolymers suffer from manufacturing limitations using common melt or solvent processing techniques due to the inherent low surface energy and high crystallinity of fluoropolymers. In this report, we prepared an energetic composite utilizing the versatility of urethane-based polymers and provide a comparative thermal characterization study. Specifically, a thermite formulation comprising of nanometer-sized aluminum (nAl) fuel coated with perfluoropolyether (PFPE) oxidizer was solvent-blended with either a polyethylene glycol (PEG) or PFPE-segmented urethane copolymer. Thermal data were collected with calorimetric and thermogravimetric techniques to determine glass transition temperature and decomposition temperature, which showed modest effects upon various loadings of PFPE-coated nAl in the urethane matrix. While our application focus was for energetics, this study also demonstrates the potential to expand the ability to broadly manufacture structural metallized composites to their consideration as coatings, foams, or fibers.

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Section: Introductionmentioning

confidence: 99%

Preparation and Thermal Analysis of Blended Nanoaluminum/Fluorinated Polyether-Segmented Urethane Composites

2019

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“…Meanwhile, fluoropolymer with good compatibility and stability was promising to protect active metal and improve energy output, which was commonly used as a binder to mix energetic composite. At present, polytetrafluoroethylene (PTFE) 20 , polyvinylidene fluoride (PVDF) 21 , perfluoropolyether (PFPE) 22 – 24 , perfluorotetradecanoic acid (PFTD) 25 and perfluorohexadecanoic acid (PFHD) 26 have been studied to coat nano Al particles. However, there were controversies and even opposite conclusions about the influence of fluoropolymers on the energy release of nano Al.…”

Section: Introductionmentioning

confidence: 99%

A latent highly activity energetic fuel: thermal stability and interfacial reaction kinetics of selected fluoropolymer encapsulated sub-micron sized Al particles

Wang

Ren

Yan

et al. 2021

Sci Rep

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Aluminum can enhance heat release of energetic composite in theory. However, the commonly used micron aluminum powder has several short comings like incomplete reaction and low reaction rate. Meanwhile, outer oxide shell of nano Al particle is thicker than micro Al, which leads to low active aluminum content and insufficient heat release. On the basis of previous research, reported fluoropolymers modified Al particles were compared and suitable F2311was chosen. Sub-micron scale Al (median particle size around 200 nm) was regarded as optimum coated object in consideration of activity content of aluminum powder changing with particle size. The super fine Al powder was prepared by electrical explosion method, and encapsulated in situ by selected fluorine rubber F2311. The experiments on thermal stability demonstrated F2311 coating thickness should be no less than 3.6 nm. These results were further confirmed by EXPLO5 thermo dynamic calculation. Calculated results showed that reaction characters of F2311 encapsulated Al exceeded conventional nano Al regardless of combustion and explosion. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser particle size analyzer and X-ray photoelectron spectroscopy (XPS) were used to characterize coated products’ morphology, particle size distribution and interfacial bonding information. The results showed that the coated samples were generally spherical shape, with median particle size of 217.7 nm and coating thickness of 3.6 nm. The coating shell contained a small amount of alumina and aluminum fluoride besides fluoropolymer. The non-isothermal dynamic equations of Al/F2311 and Al/Al2O3 were deduced by TG/DSC simultaneous thermal analysis. Compared with conventional nano-Al, the apparent activation energy of Al/F2311 decreased by 45 kJ/mol and the first exothermic peak temperature was about 10 °C earlier. Moreover, heat release was nearly twice as conventional nano-Al. TG-DSC-MS coupled measurements certified that active Al was enveloped by ‘fluorine atmosphere’ while F2311 decomposed in range of 200–400 °C. Alumina was replaced with aluminum fluoride inside coating layer during 400–550 °C, which broadened the diffusion path and then accelerated the permeation of oxidizing gas. In addition, the exothermic of Al-F was obviously larger than Al-O. Consequently, the oxidation reaction was activated rapidly, especially in initial exothermic period. Fluoropolymer encapsulated sub-micron sized Al was a latent highly activity energetic fuel and a potential candidate for aluminum powder.

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“…At the same time, almost all fluoropolymers have excellent mechanical performance, which can improve the mechanical properties of thermite. [ 17 ] In addition, the PTFE is readily available, as it is widely used in plastics as a fluoropolymer with the largest consumption. To improve its exothermic performance, the particles of oxidant and reducing agent in traditional thermite were refined to reach the nanometer level.…”

Section: Introductionmentioning

confidence: 99%

3D Printing of n‐Al/Polytetrafluoroethylene‐Based Energy Composites with Excellent Combustion Stability

Zheng

Huang

et al. 2021

Adv Eng Mater

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The development of 3D printing technology provides a new idea for the application of energy‐containing materials as functional reactive materials, which helps Al–F high‐energy materials to achieve customized performance and structure, so that energy transmit can be targeted. A high fuel‐load ink (up to 90 wt%) based on Al‐polytetrafluoroethylene (PTFE) is designed and fabricated using fluororubber (FR) as a binder. The content of FR is directly related to the mechanical properties of ink, and the customized structure from the uniform and stable deposition can be obtained by adjusting the content of FR (10–20 wt%). Under the display of high‐speed photography, the ink shows a strong stability in combustion performance, which is conducive to realize the performance customization of the ink in the application. To better understand the combustion mechanism, the thermal properties and combustion process are analyzed in brief through thermal analysis and the combustion snapshots.

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Thermal investigations of nanoaluminum/perfluoropolyether core–shell impregnated composites for structural energetics

Cited by 26 publications

References 16 publications

Preparation and Thermal Analysis of Blended Nanoaluminum/Fluorinated Polyether-Segmented Urethane Composites

Preparation and Thermal Analysis of Blended Nanoaluminum/Fluorinated Polyether-Segmented Urethane Composites

A latent highly activity energetic fuel: thermal stability and interfacial reaction kinetics of selected fluoropolymer encapsulated sub-micron sized Al particles

3D Printing of n‐Al/Polytetrafluoroethylene‐Based Energy Composites with Excellent Combustion Stability

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