Nano-thermite

Last updated

Nano-thermite or super-thermite is a metastable intermolecular composite (MIC) characterized by a particle size of its main constituents, a metal fuel and oxidizer, under 100 nanometers. This allows for high and customizable reaction rates. Nano-thermites contain an 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.

Contents

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, propellants, explosives, incendiary devices, and pyrotechnics. Research into military applications of nano-sized materials began in the early 1990s. [2] Because of their highly increased reaction rate, nano-thermitic materials are being studied by the U.S. military with the aim of developing new types of bombs several times more powerful than conventional explosives. [3] Nanoenergetic materials can store more energy than conventional energetic materials and can be used in innovative ways to tailor the release of this energy. Thermobaric weapons are one potential application of nanoenergetic materials. [4]

Types

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

In military research, aluminium-molybdenum oxide, aluminium-Teflon and aluminium-copper(II) oxide have received considerable attention. [2] Other compositions tested were based on nanosized RDX and with thermoplastic elastomers. PTFE or other fluoropolymer can be used as a binder for the composition. Its reaction with the aluminium, similar to 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]

The most common types of production are in liquids or via resonant acoustic mixing. However, more complicated methods like the ones previously mentioned are used. [8]

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. lead styphnate, lead azide) in percussion caps and electric matches. Compositions based on Al-Bi2O3 tend to be used. PETN may be optionally added. [9]

Aluminium powder can be added to nano explosives. Aluminium has a relatively low combustion rate and a high enthalpy of combustion. [10]

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. [11]

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. [12]

See also

Related Research Articles

<span class="mw-page-title-main">Thermite</span> Pyrotechnic composition of metal powder and metal oxide

Thermite is a pyrotechnic composition of metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic reduction-oxidation (redox) reaction. Most varieties are not explosive, but can create brief bursts of heat and high temperature in a small area. Its form of action is similar to that of other fuel-oxidizer mixtures, such as black powder.

<span class="mw-page-title-main">Iron(III) oxide</span> Chemical compound

Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It occurs in nature as the mineral hematite, which serves as the primary source of iron for the steel industry. It is also known as red iron oxide, especially when used in pigments.

<span class="mw-page-title-main">Titanium diboride</span> Chemical compound

Titanium diboride (TiB2) is an extremely hard ceramic which has excellent heat conductivity, oxidation stability and wear resistance. TiB2 is also a reasonable electrical conductor, so it can be used as a cathode material in aluminium smelting and can be shaped by electrical discharge machining.

<span class="mw-page-title-main">Lithium aluminate</span> Chemical compound

Lithium aluminate, also called lithium aluminium oxide, is an inorganic chemical compound, an aluminate of lithium. In microelectronics, lithium aluminate is considered as a lattice matching substrate for gallium nitride. In nuclear technology, lithium aluminate is of interest as a solid tritium breeder material, for preparing tritium fuel for nuclear fusion. Lithium aluminate is a layered double hydroxide (LDH) with a crystal structure resembling that of hydrotalcite. Lithium aluminate solubility at high pH is much lower than that of aluminium oxides. In the conditioning of low- and intermediate level radioactive waste (LILW), lithium nitrate is sometimes used as additive to cement to minimise aluminium corrosion at high pH and subsequent hydrogen production. Indeed, upon addition of lithium nitrate to cement, a passive layer of LiH(AlO
2)
2 · 5 H
2O is formed onto the surface of metallic aluminium waste immobilised in mortar. The lithium aluminate layer is insoluble in cement pore water and protects the underlying aluminium oxide covering the metallic aluminium from dissolution at high pH. It is also a pore filler. This hinders the aluminium oxidation by the protons of water and reduces the hydrogen evolution rate by a factor of 10.

<span class="mw-page-title-main">Nanocomposite</span> Solid material with nano-scale structure

Nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material.

A pyrotechnic composition is a substance or mixture of substances designed to produce an effect by heat, light, sound, gas/smoke or a combination of these, as a result of non-detonative self-sustaining exothermic chemical reactions. Pyrotechnic substances do not rely on oxygen from external sources to sustain the reaction.

Ammonium perchlorate composite propellant (APCP) is a solid rocket propellant. It differs from many traditional solid rocket propellants such as black powder or zinc-sulfur, not only in chemical composition and overall performance but also by being cast into shape, as opposed to powder pressing as with black powder. This provides manufacturing regularity and repeatability, which are necessary requirements for use in the aerospace industry.

<span class="mw-page-title-main">Exothermic welding</span> Using pyrotechnic metal to join two metal pieces together

Exothermic welding, also known as exothermic bonding, thermite welding (TW), and thermit welding, is a welding process that employs molten metal to permanently join the conductors. The process employs an exothermic reaction of a thermite composition to heat the metal, and requires no external source of heat or current. The chemical reaction that produces the heat is an aluminothermic reaction between aluminium powder and a metal oxide.

In pyrotechnics, a pyrotechnic initiator is a device containing a pyrotechnic composition used primarily to ignite other, more difficult-to-ignite materials, such as thermites, gas generators, and solid-fuel rockets. The name is often used also for the compositions themselves.

In the U.S. military, reactive materials (RM) are a new class of materials currently being investigated by the Office of Naval Research and others as a means to increase the lethality of direct-hit or fragmentation warheads. Reactive materials are similar to insensitive high explosives, but are usually thermite-like pyrotechnic compositions of two or more nonexplosive solid materials, which stay inert and do not react with each other until subjected to a sufficiently strong mechanical, electrical or laser stimulus, after which they undergo fast burning or explosion with release of high amount of chemical energy in addition to their kinetic energy. Fragments or projectiles made of such materials have therefore greater damaging effect than inert ones, with expected lethality increase up to 500%.

<span class="mw-page-title-main">Zirconium diboride</span> Chemical compound

Zirconium diboride (ZrB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure. ZrB2 is an ultra-high temperature ceramic (UHTC) with a melting point of 3246 °C. This along with its relatively low density of ~6.09 g/cm3 (measured density may be higher due to hafnium impurities) and good high temperature strength makes it a candidate for high temperature aerospace applications such as hypersonic flight or rocket propulsion systems. It is an unusual ceramic, having relatively high thermal and electrical conductivities, properties it shares with isostructural titanium diboride and hafnium diboride.

<span class="mw-page-title-main">Calcium permanganate</span> Chemical compound

Calcium permanganate is an oxidizing agent and chemical compound with the chemical formula Ca(MnO4)2. This salt consists of the metal calcium and two permanganate ions.

Self-propagating high-temperature synthesis (SHS) is a method for producing both inorganic and organic compounds by exothermic combustion reactions in solids of different nature. Reactions can occur between a solid reactant coupled with either a gas, liquid, or other solid. If the reactants, intermediates, and products are all solids, it is known as a solid flame. If the reaction occurs between a solid reactant and a gas phase reactant, it is called infiltration combustion. Since the process occurs at high temperatures, the method is ideally suited for the production of refractory materials including powders, metallic alloys, or ceramics.

Aluminum-Ice Rocket Propellant, or ALICE, is a rocket propellant that consists of nano-aluminum powder and water. After mixing, the material is frozen to keep it stable.

Reactive multi-layer foils are a class of reactive materials, sometimes referred to as a pyrotechnic initiator of two mutually reactive metals, sputtered to form thin layers that create a laminated foil. On initiation by a heat pulse, delivered by a bridge wire, a laser pulse, an electric spark, a flame, or by other means, the metals undergo self-sustaining exothermic reaction, producing an intermetallic compound. The reaction occurs in solid and liquid phase only, without releasing any gas.

<span class="mw-page-title-main">Carbon nanotube metal matrix composite</span>

Carbon nanotube metal matrix composites (CNT-MMC) are an emerging class of new materials that mix carbon nanotubes into metals and metal alloys to take advantage of the high tensile strength and electrical conductivity of carbon nanotube materials.

Ultra-high-temperature ceramics (UHTCs) are a type of refractory ceramics that can withstand extremely high temperatures without degrading, often above 2,000 °C. They also often have high thermal conductivities and are highly resistant to thermal shock, meaning they can withstand sudden and extreme changes in temperature without cracking or breaking. Chemically, they are usually borides, carbides, nitrides, and oxides of early transition metals.

Pulsation reactor technology is a thermal procedure for manufacturing fine powders with precisely defined properties.

<span class="mw-page-title-main">Aluminium oxide nanoparticle</span>

Nanosized aluminium oxide occurs in the form of spherical or nearly spherical nanoparticles, and in the form of oriented or undirected fibers.

<span class="mw-page-title-main">Aluminium-based nanogalvanic alloys</span>

Aluminium-based nanogalvanic alloys refer to a class of nanostructured metal powders that spontaneously and rapidly produce hydrogen gas upon contact with water or any liquid containing water as a result of their galvanic metal microstructure. It serves as a method of hydrogen production that can take place at a rapid pace at room temperature without the assistance of chemicals, catalysts, or externally supplied power.

References

  1. ↑ "Effect of Al particle size on the thermal degradation of Al/teflon mixtures" (PDF). Informaworld.com. 2007-08-08. Retrieved 2010-03-03.
  2. 1 2 3 4 5 6 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. doi:10.17226/10594. ISBN   978-0-309-08601-1. 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. ↑ Polis, Mateusz; Stolarczyk, Agnieszka; Glosz, Karolina; Jarosz, Tomasz (January 2022). "Quo Vadis, Nanothermite? A Review of Recent Progress". Materials. 15 (9): 3215. doi: 10.3390/ma15093215 . ISSN   1996-1944. PMC   9105280 . PMID   35591548.
  9. ↑ "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.
  10. ↑ "Aluminum Burn Rate Modifiers Based on Reactive Nanocomposite Powders (PDF)" (PDF). Archived (PDF) from the original on 2011-02-04. Retrieved 2010-03-03.
  11. ↑ 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.
  12. ↑ 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.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.