Nano-thermite

Nano-thermite or super-thermite is a metastable intermolecular composite (MIC) characterized by a particle size of its main constituents, a metal and a metal

oxidizer and a reducing agent, which are intimately mixed on the nanometer scale. MICs, including nano-thermitic materials, are a type of reactive materials investigated for military use, as well as for general applications involving propellants, explosives, and pyrotechnics

.

What distinguishes MICs from traditional thermites is that the oxidizer and a reducing agent, normally iron oxide and aluminium, are in the form of extremely fine powders (nanoparticles). This dramatically increases the reactivity relative to micrometre-sized powder thermite. As the mass transport mechanisms that slow down the burning rates of traditional thermites are not so important at these scales,^{[citation needed]} the reaction proceeds much more quickly.

Potential uses

Historically, pyrotechnic or explosive applications for traditional thermites have been limited due to their relatively slow energy release rates. Because nanothermites are created from reactant particles with proximities approaching the atomic scale, energy release rates are far greater.^[1]

MICs or super-thermites are generally developed for military use,

Thermobaric weapons are one potential application of nanoenergetic materials.^[4]

Types

There are many possible thermodynamically stable fuel-oxidizer combinations. Some of them are:

molybdenum(VI) oxide

Aluminium-copper(II) oxide
Aluminium-iron(II,III) oxide
Antimony-potassium permanganate
Aluminium-potassium permanganate
Aluminium-bismuth(III) oxide
Aluminium-
tungsten(VI) oxide
hydrate
Aluminium-
Viton
)
Titanium-boron (burns to titanium diboride, which belongs to a class of compounds called intermetallic composites).

In military research, aluminium-

magnesium/teflon/viton thermite, adds energy to the reaction.^[5] Of the listed compositions, that with potassium permanganate has the highest pressurization rate.^[6]

The most common method of preparing nanoenergetic materials is by ultrasonification in quantities of less than 2g. Some research has been developed to increase production scales. Due to the very high electrostatic discharge (ESD) sensitivity of these materials, sub 1 gram scales are currently typical.

Production

Nanoaluminum, or ultra fine grain (UFG) aluminum, powders are a key component of most nano-thermitic materials. A method for producing this material is the dynamic gas-phase condensation method, pioneered by Wayne Danen and Steve Son at Los Alamos National Laboratory. A variant of the method is being used at the Indian Head Division of the Naval Surface Warfare Center. Another method for production is electrothermal synthesis, developed by NovaCentrix, which uses a pulsed plasma arc to vaporize the aluminum. The powders made by the dynamic gas-phase condensation and the electrothermal synthesis processes are indistinguishable.^[7] A critical aspect of the production is the ability to produce particles of sizes in the tens of nano-meter range, as well as with a limited distribution of particle sizes. In 2002, the production of nano-sized aluminum particles required considerable effort, and commercial sources for the material were limited.^[2]

An application of the

sol-gel method, developed by Randall Simpson, Alexander Gash and others at the Lawrence Livermore National Laboratory, can be used to make the actual mixtures of nano-structured composite energetic materials. Depending on the process, MICs of different density can be produced. Highly porous and uniform products can be achieved by super-critical extraction.^[2]

Ignition

As with all explosives, research into control yet simplicity has been a goal of research into nanoscale explosives.[2] Some can be ignited with laser pulses.^[2]

MICs have been investigated as a possible replacement for lead (e.g.

PETN may be optionally added.^[8]

explosives. Aluminium has a relatively low combustion rate and a high enthalpy of combustion.^[9]

The products of a thermite reaction, resulting from ignition of the nano-thermitic mixture, are usually metal oxides and elemental metals. At the temperatures prevailing during the reaction, the products can be solid, liquid or gaseous, depending on the components of the mixture.[10]

Hazards

Like conventional thermite, super thermite reacts at very high temperature and is difficult to extinguish. The reaction produces dangerous ultra-violet (UV) light, requiring that the reaction not be viewed directly or that special eye protection (for example, a welder's mask) be worn.

In addition, super thermites are very sensitive to electrostatic discharge (ESD). Surrounding the metal oxide particles with carbon nanofibers may make nanothermites safer to handle.^[11]

References

^ "Effect of Al particle size on the thermal degradation of Al/teflon mixtures" (PDF). Informaworld.com. 2007-08-08. Retrieved 2010-03-03.
^ ^a ^b ^c ^d ^e ^f Miziolek, Andrzej (2002). "Nanoenergetics: An Emerging Technology Area of National Importance" (PDF). AMPTIAC Quarterly. 6 (1). Archived from the original (PDF) on May 12, 2016. Retrieved July 8, 2009.
^ Gartner, John (Jan 21, 2005). "Military Reloads with Nanotech". MIT Technology Review. Archived from the original on May 7, 2009. Retrieved May 3, 2009.
^ "Novel Energetic Materials". GlobalSecurity.org. Archived from the original on 2011-10-03.
^ "2002 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program, Naval Studies Board (NSB)". Books.nap.edu. 2003-06-01. Archived from the original on 2011-12-05. Retrieved 2010-03-03.
^ "Reaction Kinetics and Thermodynamics of Nanothermite Propellants". Ci.confex.com. Archived from the original on 2011-08-13. Retrieved 2010-03-03.
^ "Safety and Handling of Nano-aluminum" (PDF). Archived from the original (PDF) on 2011-02-04. Retrieved 2010-10-12.
^ "Metastable Intermolecular Composites (MIC) for Small Caliber Cartridges and Cartridge Actuated Devices (PDF)" (PDF). Archived (PDF) from the original on 2011-02-04. Retrieved 2010-03-03.
^ "Aluminum Burn Rate Modifiers Based on Reactive Nanocomposite Powders (PDF)" (PDF). Archived (PDF) from the original on 2011-02-04. Retrieved 2010-03-03.
^ Fischer, S.H.; Grubelich, M.C. (July 1–3, 1996). "A Survey of Combustible Metals, Thermites, and Intermetallics for Pyrotechnic Applications" (PDF). Archived from the original on February 21, 2023. Retrieved July 17, 2009.
^ Brown, Mike (November 5, 2010). "Nanofibres defuse explosives". Chemistry World. Royal Society of Chemistry. Archived from the original on 2011-02-04. Retrieved 2010-12-20.

External links

Synthesis and Reactivity of a Super-Reactive Metastable Intermolecular Composite Formulation of Al/KMnO4
Metastable Intermolecular Composites for Small Caliber Cartridges and Cartridge Actuated Devices
Performance of Nanocomposite Energetic Materials Al-MoO3
John J. Granier (May 2005). Combustion Characteristics of Al Nanoparticles and Nanocomposite Al+MoO₃ Thermites (PDF). Texas Tech University. Archived from the original (PDF) on September 8, 2008. Retrieved May 3, 2009(PhD thesis).{{cite book}}: CS1 maint: postscript (link)

[1] "Effect of Al particle size on the thermal degradation of Al/teflon mixtures" (PDF). Informaworld.com. 2007-08-08. Retrieved 2010-03-03.

[Miziolek-2] ^ ^a ^b ^c ^d ^e ^f Miziolek, Andrzej (2002). "Nanoenergetics: An Emerging Technology Area of National Importance" (PDF). AMPTIAC Quarterly. 6 (1). Archived from the original (PDF) on May 12, 2016. Retrieved July 8, 2009.

[3] Gartner, John (Jan 21, 2005). "Military Reloads with Nanotech". MIT Technology Review. Archived from the original on May 7, 2009. Retrieved May 3, 2009.

[4] "Novel Energetic Materials". GlobalSecurity.org. Archived from the original on 2011-10-03.

[5] "2002 Assessment of the Office of Naval Research's Air and Surface Weapons Technology Program, Naval Studies Board (NSB)". Books.nap.edu. 2003-06-01. Archived from the original on 2011-12-05. Retrieved 2010-03-03.

[6] "Reaction Kinetics and Thermodynamics of Nanothermite Propellants". Ci.confex.com. Archived from the original on 2011-08-13. Retrieved 2010-03-03.

[7] "Safety and Handling of Nano-aluminum" (PDF). Archived from the original (PDF) on 2011-02-04. Retrieved 2010-10-12.

[8] "Metastable Intermolecular Composites (MIC) for Small Caliber Cartridges and Cartridge Actuated Devices (PDF)" (PDF). Archived (PDF) from the original on 2011-02-04. Retrieved 2010-03-03.

[9] "Aluminum Burn Rate Modifiers Based on Reactive Nanocomposite Powders (PDF)" (PDF). Archived (PDF) from the original on 2011-02-04. Retrieved 2010-03-03.

[10] Fischer, S.H.; Grubelich, M.C. (July 1–3, 1996). "A Survey of Combustible Metals, Thermites, and Intermetallics for Pyrotechnic Applications" (PDF). Archived from the original on February 21, 2023. Retrieved July 17, 2009.

[11] Brown, Mike (November 5, 2010). "Nanofibres defuse explosives". Chemistry World. Royal Society of Chemistry. Archived from the original on 2011-02-04. Retrieved 2010-12-20.

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