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Blaine W. Asay

Other affiliations: Texas Tech University
Bio: Blaine W. Asay is an academic researcher from Los Alamos National Laboratory. The author has contributed to research in topics: Explosive material & Ignition system. The author has an hindex of 25, co-authored 97 publications receiving 2712 citations. Previous affiliations of Blaine W. Asay include Texas Tech University.


Papers
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Journal ArticleDOI
TL;DR: In this paper, combustion velocities were experimentally determined for nanocomposite thermite powders composed of aluminum (Al) fuel and molybdenum trioxide (MoO3) oxidizer under well-confined conditions.
Abstract: Combustion velocities were experimentally determined for nanocomposite thermite powders composed of aluminum (Al) fuel and molybdenum trioxide (MoO3) oxidizer under well-confined conditions Pressures were also measured to provide detailed information about the reaction mechanism Samples of three different fuel particle sizes (44, 80, and 121nm) were analyzed to determine the influence of particle size on combustion velocity Bulk powder density was varied from approximately 5% to 10% of the theoretical maximum density (TMD) The combustion velocities ranged from approximately 600 to 1000m∕s Results indicate that combustion velocities increase with decreasing particle size Pressure measurements indicate that strong convective mechanisms are integral in flame propagation

270 citations

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TL;DR: In this article, the authors examined the performance of four different nanoaluminum/metal-oxide composites in terms of pressure output and propagaton speed for the open burn experiment and found that there is a correlation between the maximum pressure output of each composite and optimum propagation speed.
Abstract: Nanoscale composite energetics (also known as metastable intermolecular composites) represent an exciting new class of energetic materials. Nanoscale thermites are examples of these materials. The nanoscale thermites studied consist of a metal and metal oxide with particle sizes in the 30-200 nm range. They have potential for use in a wide range of applications. The modes of combustion and reaction behavior of these materials are not yet well understood. This investigation considers four different nanoaluminum/metal-oxide composites. The same nanoscale aluminum was used for each composite. The metal oxides used were molybdenum oxide (MoO 3 ), tungsten oxide (WO 3 ), copper oxide (CuO), and bismuth oxide (Bi 2 O 3 ). The reaction performance was quantified by the pressure output and propagation velocity using unconfined (or open burn) and confined (burn tube) experiments. We examine the optimization of each composite in terms of pressure output and propagaton speed (or burn rate) for the open burn experiment. We find that there is a correlation between the maximum pressure output and optimum propagation speed (or burn rate). Equilibrium calculations are used to interpret these results. We find that the propagation speed depends on the gas production and also on the thermodynamic state of the products. This suggests that condensing gases or solidifying liquids could greatly enhance heat transfer. We also vary the density of these composites and examine the change in performance. Although the propagation wave is likely supersonic with respect to the mixture sound speed, the propagation speed decreases with density. This behavior is opposite of classical detonation in which propagation (detonation) speed increases with density. This result indicates that the propagation mechanism may differ fundamentally from classical detonations.

256 citations

Journal ArticleDOI
TL;DR: In this article, an unexpected mechanism for fast oxidation of Al nanoparticles covered by a thin oxide shell (OS) is proposed, where volume change due to melting of Al induces pressures of 1 − 4 GPa and causes spallation of the OS.
Abstract: An unexpected mechanism for fast oxidation of Al nanoparticles covered by a thin oxide shell (OS) is proposed The volume change due to melting of Al induces pressures of 01–4GPa and causes spallation of the OS A subsequent unloading wave creates high tensile pressures resulting in dispersion of liquid Al clusters, oxidation of which is not limited by diffusion (in contrast to traditional mechanisms) Physical parameters controlling this process are determined Methods to promote this melt dispersion mechanism, and consequently, improve efficiency of energetic nanothermites are discussed

177 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the combustion of mixtures of nanoscale aluminum with molybdenum trioxide in microscale channels and found that the optimum mixture ratio for the maximum propagation rate is aluminum rich.
Abstract: : Microscale combustion is of interest in small-volume energy-demanding systems, such as power supplies, actuation, ignition, and propulsion Energetic materials can have high burning rates that make these materials advantageous, especially for microscale applications in which the rate of energy release is important or in which air is not available as an oxidizer In this study we examine the combustion of mixtures of nanoscale aluminum with molybdenum trioxide in microscale channels Nanoscale composites can have very high burning rates that are much higher than typical materials Quartz and acrylic tubes are used Rectangular steel microchannels are also considered We find that the optimum mixture ratio for the maximum propagation rate is aluminum rich We use equilibrium calculations to argue that the propagation rate is dominated by a convective process where hot liquids and gases are propelled forward heating the reactants This is the first study to report the dependence of the propagation rate with a tube diameter for this class of materialsWefind that the propagation rate decreases linearly with 1=d The propagation rate remains high in tubes or channels with dimensions down to the scale of 100 m, which makes these materials applicable to microcombustion applications

167 citations

Journal ArticleDOI
TL;DR: In this paper, an unexpected mechanism for fast reaction of Alnanoparticles covered by a thin oxide shell during fast heating is proposed and justified theoretically and experimentally, in which the volume change due to melting induces pressures of 1-2 GPa and causes dynamic spallation of the shell.
Abstract: An unexpected mechanism for fast reaction of Alnanoparticles 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 cavitationpressure; (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.

143 citations


Cited by
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Journal ArticleDOI
TL;DR: A comprehensive review of recent synthetic methods along with associated synthesis mechanisms, characterization, fundamental properties, and promising applications of Cupric oxide (CuO) nanostructures is presented in this article.

1,030 citations

Journal ArticleDOI
TL;DR: A review of metal-based reactive nanomaterials can be found in this paper, where some potential directions for the future research are discussed and some potential application areas are explored.

739 citations

Journal ArticleDOI
01 Jan 2009
TL;DR: A brief review of the classifications of metal combustion based on thermodynamic considerations and the different types of combustion regimes of metal particles (diffusion vs. kinetic control) is presented in this article.
Abstract: Metal combustion has received renewed interest largely as a result of the ability to produce and characterize metallic nanoparticles. Much of the highly desirable traits of nanosized metal powders in combustion systems have been attributed to their high specific surface area (high reactivity) and potential ability to store energy in surfaces. In addition, nanosized powders are known to display increased catalytic activity, superparamagnetic behavior, superplasticity, lower melting temperatures, lower sintering temperatures, and higher theoretical densities compared to micron and larger sized materials. The lower melting temperatures can result in lower ignition temperatures of metals. The combustion rates of materials with nanopowders have been observed to increase significantly over similar materials with micron sized particles. A lower limit in size of nanoenergetic metallic powders in some cases may result from the presence of their passivating oxide coating. Consequently, coatings, self-assembled monolayers (SAMs), and the development of composite materials that limit the volume of non-energetic material in the powders have been under development in recent years. After a brief review of the classifications of metal combustion based on thermodynamic considerations and the different types of combustion regimes of metal particles (diffusion vs. kinetic control), an overview of the combustion of aluminum nanoparticles, their applications, and their synthesis and assembly is presented.

707 citations

Journal ArticleDOI
TL;DR: In this paper, a variety of techniques used to obtain the mechanical properties of materials at high rates of strain (⩾10 s−1) are summarised, including dropweight machines, split Hopkinson pressure bars, Taylor impact and shock loading by plate impact.

683 citations

Journal ArticleDOI
TL;DR: In this article, a review of the development of micro-power generators by focusing more on the advance in fundamental understanding of microscale combustion is presented, and the conventional concepts of combustion limits such as flammability limit, quenching diameter, and flame extinction and heat recirculation are revisited.

621 citations