Evaluating compositional effects on the laser-induced combustion and shock velocities of Al/Zr-based composite fuels

Wainwright, Elliot R.; Dean, Steven W.; Lakshman, Shashank Vummidi; Weihs, Timothy P.; Gottfried, Jennifer L.

doi:10.1016/j.combustflame.2019.12.009

Cited by 30 publications

(4 citation statements)

References 47 publications

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“…Through discussing in detail our understanding of this form of wet synthesis, we hope to spur further development of this field and foster exploration from perspectives different than our own. For example, much of our work has focused on the optical properties of Al NCs and NPs, but there is a growing interest in their potential for energy storage, due to the inherently high energy density of Al. − Colloidal Al chemistry still retains a tremendous capacity for exploration. Understanding what causes kinetic versus thermodynamic control is incomplete, while control over twinning, stabilization of high-energy facets, and proper seed-mediated synthesis for monodisperse particles remain elusive.…”

Section: Discussionmentioning

confidence: 99%

Shining Light on Aluminum Nanoparticle Synthesis

et al. 2020

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Conspectus Aluminum in its nanostructured form is generating increasing interest because of its light-harvesting properties, achieved by excitation of its localized surface plasmon resonance. Compared to traditional plasmonic materials, the coinage metals Au and Ag, Al is far more earth-abundant and, therefore, more suitable for large-area applications or where cost may be an important factor. Its optical properties are far more flexible than either Au or Ag, supporting plasmon resonances that range from UV wavelengths, through the visible regime, and into the infrared region of the spectrum. However, the chemical synthesis of Al nanocrystals (NCs) of controlled size and shape has historically lagged far behind that of Au and Ag. This is partially due to the high reactivity of Al precursors, which react readily with O2, H2O, and many reagents used in traditional NC syntheses. The first chemical synthesis of Al NCs was demonstrated by Haber and Buhro in 1998, decomposing AlH3 using titanium isopropoxide (TIP), with a number of subsequent reports refining this protocol. The role of a catalyst in Al NC synthesis is, we believe, unique to this synthetic approach. In 2015, the first synthesis of size controlled Al NCs was published by our group. Since then, we have significantly advanced Al NC synthesis, postsynthetic modifications, and applications of Al nanoparticles (NPs)NCs with additional surface modificationsin chemical sensing and photocatalysis. Colloidal Al synthesis has its unique challenges, differing markedly from the far more familiar Au and Ag syntheses, which currently appears to present a de facto barrier to broader research activity in this field. The goal of this Account is to highlight developments in controlled synthesis of Al NCs and applications of Al NPs over the last five years. We outline techniques for successful Al NC synthesis and address some of the problems that may be encountered in this synthesis. A mechanistic understanding of AlH3 decomposition using TIP has been developed, while new directions have been discovered for synthetic control. Facet-binding ligands, alternate Al precursors, new titanium-based reduction catalysts, even solvent composition have all been shown to control reaction products while also opening doors to future developments. A variety of postsynthetic modifications to the Al NC native oxide surface, including polymer, MOF, and transition metal island coatings have been demonstrated for applications in molecular sensing and photocatalysis. In this Account, we hope to convey that Al synthesis is more accessible than generally perceived and to encourage new synthetic development based on underlying mechanisms controlling size and shape. High selectivity in particle faceting and twinning, implementation of seeded growth principles for monodisperse samples, and the demonstration of new, practical applications of Al nanoparticles remain primary challenges in the field. As Al nanoparticle synthesis is refined and new applications emerge, colloidal Al will become an acce...

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Section: Discussionmentioning

confidence: 99%

Shining Light on Aluminum Nanoparticle Synthesis

et al. 2020

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“…Recent studies on MICs have shown that reducing component size, , enhancing the contact between fuels and oxidizers, − and/or increasing the ignitibility of the fuels − enhance their reactivity. Loose powders must ultimately be manufactured into free-standing architectures by incorporating different types of binders or architectures for any realistic application. − Unfortunately, the incorporation of these energetic materials into dense structures can also inhibit their performance since their combustion becomes limited by binder decomposition and phase transitions, − ultimately leading to order-of-magnitude changes in the burn rate. , This leads to even more parameters to balancebinder materials must be employed to make the materials safe and avoid accidents but must be used in as little quantity as possible to retain their potential energy release. ,− …”

Section: Introductionmentioning

confidence: 99%

Carbon Fibers Enhance the Propagation of High Loading Nanothermites: In Situ Observation of Microscopic Combustion

Wang

Kline

Rehwoldt

et al. 2021

ACS Appl. Mater. Interfaces

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A major challenge in formulating and manufacturing energetic materials lies in the balance between total energy density, energy release rate, and mechanical integrity. In this work, carbon fibers are embedded into ∼90 wt % loading Al/CuO nanothermite sticks through a simple extrusion direct writing technique. With only ∼2.5 wt % carbon fiber addition, the burn rate and heat flux were promoted >2×. In situ microscopic observation of combustion shows that the carbon fiber intercept ejected hot agglomerates near the burning surface and enhanced heat feedback to the unreacted material. This study outlines how these approaches may enhance the propagation and reduce the two-phase flow losses.

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“…Similar to aluminothermites, all boron-based couples show a clear steady state propagation, reaching their disruption temperature (see Figure 4), once the steady state regime is established. Zirconium-Based Thermites-In a similar capacity to boron metal, nanosized zirconium has been proposed as an additive to improve the properties of conventional Al micron-sized fuel, with these three-material composite thermites showing higher reactivity in terms of initiation time, increased energy delivery and longer combustion duration [66]. Importantly, the poor oxygen diffusivity across ZrO2, the lowest of all considered fuels in the initiation temperature range (1000-2000 K, see Supplementary Information File S1) is a strong limit to the reactivity of thermites using only Zr as the fuel, even more limiting than the case of boron, which also exhibits difficulties for initiation for the same reason.…”

Section: Benchmark Studymentioning

confidence: 99%

A Benchmark Study of Burning Rate of Selected Thermites through an Original Gasless Theoretical Model

Brotman¹,

Rouhani²,

Charlot³

et al. 2021

Applied Sciences

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This paper describes a kinetic model dedicated to thermite nanopowder combustion, in which core equations are based on condensed phase mechanisms only. We explore all combinations of fuels/oxidizers, namely Al, Zr, B/CuO, Fe2O3, WO3, and Pb3O4, with 60 % of the theoretical maximum density packing, at which condensed phase mechanisms govern the reaction. Aluminothermites offer the best performances, with initiation delays in the range of a few tens of microseconds, and faster burn rates (60 cm s−1 for CuO). B and Zr based thermites are primarily limited by diffusion characteristics in their oxides that are more stringent than the common Al2O3 barrier layer. Combination of a poor thermal conductivity and efficient oxygen diffusion towards the fuel allows rapid initiation, while thermal conductivity is essential to increase the burn rate, as evidenced from iron oxide giving the fastest burn rates of all B- and Zr-based thermites (16 and 32 cm·s−1, respectively) despite poor mass transport properties in the condensed phase; almost at the level of Al/CuO (41 versus 61 cm·s−1). Finally, formulations of the effective thermal conduction coefficient are provided, from pure bulk, to nanoparticular structured material, giving light to the effects of the microstructure and its size distribution on thermite performances.

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Evaluating compositional effects on the laser-induced combustion and shock velocities of Al/Zr-based composite fuels

Cited by 30 publications

References 47 publications

Shining Light on Aluminum Nanoparticle Synthesis

Shining Light on Aluminum Nanoparticle Synthesis

Carbon Fibers Enhance the Propagation of High Loading Nanothermites: In Situ Observation of Microscopic Combustion

A Benchmark Study of Burning Rate of Selected Thermites through an Original Gasless Theoretical Model

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