Surface engineered nanoparticles dispersed in kerosene: The effect of oleophobicity on droplet combustion

Bello, Michael N.; Hill, Kevin J.; Pantoya, Michelle L.; Jouet, R. Jason; Horn, Jillian M.

doi:10.1016/j.combustflame.2017.09.041

Cited by 16 publications

(10 citation statements)

References 13 publications

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“…Interestingly, fluorine atoms could decompose the inert Al 2 O 3 shell surrounding the Al NPs into AlF 3 products, producing an exothermic surface reaction that promotes the decomposition of the fluorine-containing oxidizers [ 21 , 22 ]. It has been reported that fluorine-containing oxidizers such as polytetrafluoroethylene (PTFE) [ 23 , 24 ], polyvinylidene fluoride (PVDF) [ 25 , 26 , 27 ], perfluorotetradecanoic acid (PFTD) [ 28 , 29 ], perfluoroalkyl acids (PFAA) [ 30 ], and perfluorohexadecanoic acid (PFHD) [ 31 ] are capable of enhancing the ignition and combustion behavior of Al NPs because of pre-ignition reaction (PIR) which occurs prior to the oxidation reaction of the Al core. However, although the effect of PIR on activating reactivity of Al NPs was demonstrated several years ago [ 32 , 33 ], little attention has been paid to the oxidation mechanism of surface-modification Al NPs regulated by the reaction interface Fuel-Oxidizer ratio.…”

Section: Introductionmentioning

confidence: 99%

Tuning the Reactivity of Perfluoropolyether-Functionalized Aluminum Nanoparticles by the Reaction Interface Fuel-Oxidizer Ratio

Nie

et al. 2022

Nanomaterials

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To deepen the oxidation depth and promote the exothermic reaction of aluminum nanoparticles (Al NPs), this work constructed perfluoropolyether-functionalized Al NPs by using a facile fabrication method. It was determined that perfluoropolyether (PFPE) was uniformly distributed on the surface of the Al NPs with no obvious agglomeration by micro-structure analysis. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), microcomputer automatic calorimeter (MAC), and combustion and ignition experiments were performed for varying percentages of PFPE blended with Al NPs to examine the reaction kinetics and combustion performance. It was revealed that the oxidation mechanism of PFPE-functionalized Al NPs at a slow heating rate was regulated by the reaction interface fuel–oxidizer ratio. Due to the enlarged fuel–oxidizer contact surface area, fluorine atoms could adequately decompose the inert alumina shell surrounding the Al NPs, optimizing the combustion process of Al NPs. The analytical X-ray diffraction (XRD) pattern results confirmed the existence of aluminum trifluoride in combustion products, providing insights into the oxidation mechanism of Al NPs. The obtained results indicated that PFPE participated in the oxidation of Al NPs and improved the overall reactivity of Al NPs.

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Section: Introductionmentioning

confidence: 99%

Tuning the Reactivity of Perfluoropolyether-Functionalized Aluminum Nanoparticles by the Reaction Interface Fuel-Oxidizer Ratio

Nie

et al. 2022

Nanomaterials

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“…Recently, a series of perfluoro-compounds attracted much attention due to their potential to fabricate oxygen-free metallized EMs. Long-chain perfluoroalkyl acids (PFAAs) were found to remarkably enhance the reactivity of Al-based nanothermite through surface functionalization. − The interaction mechanism between Al and fluorides was described by adopting the “preignition reaction” theory . It demonstrates that Al 2 O 3 passivation layers on the surface of nAl can directly associate with fragmented fluorides generated from the initial decomposition of long-chain fluorocarbon compounds instead of fluorine after the complete cleavage of the C–F bond.…”

Section: Introductionmentioning

confidence: 99%

Perfluoroalkyl Acid-Functionalized Aluminum Nanoparticles for Fluorine Fixation and Energy Generation

Zhao

Jiao

et al. 2021

ACS Appl. Nano Mater.

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Aluminum nanoparticle (nAl) has a promising application prospect in energetic materials (EMs) due to its high reactivity. However, some issues like agglomeration and oxide layers seriously affect its performances. To actualize the potential of nAl, perfluoroalkyl acids (PFAAs) with different molecular structures were introduced into nAl-based EMs for surface functionalization in the current work. The energy performances of nAl/PFAAs including flame propagation features and heat release were investigated in different atmospheres, and the related fluorine fixation ratio ( FF R) was also obtained. Results show that both the energy performances and the FF R were improved with the increase of the skeleton chain length and the fluorine content of PFAAs. Although the heat release is higher in air, FF R in air is apparently lower than that in N 2 . Possible reaction mechanisms were probed by the in-situ monitoring of the gaseous and condensed products from thermal decomposition. This reveals that the oxide layer was first corroded by carboxyl, and fluorocarbons were generated succeeded by the fluorination of exposed Al. The most reactive intermediates are CF x free radicals, which dominates the initial interaction.

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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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Surface engineered nanoparticles dispersed in kerosene: The effect of oleophobicity on droplet combustion

Cited by 16 publications

References 13 publications

Tuning the Reactivity of Perfluoropolyether-Functionalized Aluminum Nanoparticles by the Reaction Interface Fuel-Oxidizer Ratio

Tuning the Reactivity of Perfluoropolyether-Functionalized Aluminum Nanoparticles by the Reaction Interface Fuel-Oxidizer Ratio

Perfluoroalkyl Acid-Functionalized Aluminum Nanoparticles for Fluorine Fixation and Energy Generation

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

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