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 An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...

, under 100

nanometers 330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American and British English spelling differences#-r ...

. This allows for high and customizable reaction rates. Nano-thermites contain an

and a

reducing agent In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are common reducing agents include hydrogen, carbon ...

, which are intimately mixed on the nanometer scale. MICs, including nano-thermitic materials, are a type of

reactive material 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 s ...

s investigated for military use, as well as for general applications involving propellants, explosives, and

pyrotechnics Pyrotechnics is the science and craft of creating fireworks, but also includes safety matches, oxygen candles, Pyrotechnic fastener, explosive bolts (and other fasteners), parts of automotive airbags, as well as gas-pressure blasting in mining, q ...

. What distinguishes MICs from traditional

thermite Thermite () is a pyrotechnic composition of powder metallurgy, metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic redox, reduction-oxidation (redox) reaction. Most varieties are not explos ...

s is that the oxidizer and a reducing agent, normally

iron oxide An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust. Iron ...

and

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

, are in the form of extremely fine powders (

nanoparticle A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At ...

s). This dramatically increases the reactivity relative to

micrometre The micrometre (English in the Commonwealth of Nations, Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a uni ...

-sized powder thermite. As the mass transport mechanisms that slow down the burning rates of traditional thermites are not so important at these scales, 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. MICs or super-thermites are generally developed for military use,

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicle ...

s, explosives,

incendiary device Incendiary weapons, incendiary devices, incendiary munitions, or incendiary bombs are weapons designed to start fires. They may destroy structures or sensitive equipment using fire, and sometimes operate as anti-personnel weapon, anti-personnel ...

s, and

. Research into military applications of nano-sized materials began in the early 1990s. 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. 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 A thermobaric weapon, also called an aerosol bomb, or a vacuum bomb, is a type of explosive munition that works by dispersing an aerosol cloud of gas, liquid or powdered explosive. The fuel is usually a single compound, rather than a mixture o ...

are one potential application of nanoenergetic materials.

Types

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

Aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

molybdenum(VI) oxide Molybdenum trioxide describes a family of inorganic compounds with the formula MoO3(H2O)n where n = 0, 1, 2. The anhydrous compound is produced on the largest scale of any molybdenum compound since it is the main intermediate produced when molybd ...

* Aluminium-

copper(II) oxide Copper(II) oxide or cupric oxide is an inorganic compound with the formula CuO. A black solid, it is one of the two stable oxides of copper, the other being Cu2O or copper(I) oxide (cuprous oxide). As a mineral, it is known as tenorite, or so ...

* Aluminium-

iron(II,III) oxide Iron(II,III) oxide, or black iron oxide, is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (Fe ...

Antimony Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...

potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, which dissolves in water as K+ and ions to give an intensely pink to purple solution. Potassium permanganate is widely us ...

* Aluminium-

bismuth(III) oxide Bismuth(III) oxide is a compound of bismuth, and a common starting point for bismuth chemistry. It is found naturally as the mineral bismite (monoclinic) and sphaerobismoite (tetragonal, much more rare), but it is usually obtained as a by-produc ...

* Aluminium-

tungsten(VI) oxide Tungsten(VI) oxide, also known as tungsten trioxide is a chemical compound of oxygen and the transition metal tungsten, with formula WO3. The compound is also called tungstic anhydride, reflecting its relation to tungstic acid . It is a light ...

hydrate * Aluminium-

fluoropolymer A fluoropolymer is a fluorocarbon-based polymer with multiple carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases. The best known fluoropolymer is polytetrafluoroethylene under the brand name "Teflon, ...

(typically Viton) *

Titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

boron Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...

(burns to

titanium diboride 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,J. Schmidt et al. "Preparation of titanium diboride TiB2 by spark p ...

, which belongs to a class of compounds called intermetallic composites). In military research, aluminium-

molybdenum oxide Molybdenum oxide may refer to: * Molybdenum(IV) oxide (molybdenum dioxide, ) * Molybdenum(VI) oxide (molybdenum trioxide, ) Other stoichiometric binary molybdenum-oxygen compounds include and . References

{{Chemistry index ...

, aluminium-

Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from ...

and aluminium-copper(II) oxide have received considerable attention. Other compositions tested were based on nanosized

RDX RDX (Research Department Explosive or Royal Demolition Explosive) or hexogen, among other names, is an organic compound with the formula (CH2N2O2)3. It is white, odorless, and tasteless, widely used as an explosive. Chemically, it is classified ...

and with

thermoplastic A thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains as ...

elastomer An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus (E) and high failure strain compared with other materials. The term, a portmanteau of ''ela ...

PTFE Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off fro ...

or other fluoropolymer can be used as a

binder Binder may refer to: Businesses * Binder FBM, a former German jewelry manufactory * Binder Dijker Otte & Co., the expansion of "BDO" in BDO International Computing * Binder Project, package and share interactive, reproducible environments * Fil ...

for the composition. Its reaction with the aluminium, similar to magnesium/teflon/viton thermite, adds energy to the reaction. Of the listed compositions, that with potassium permanganate has the highest pressurization rate. 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 Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development Laboratory, laboratories of the United States Department of Energy National Laboratories, United States Department of Energy ...

. A variant of the method is being used at the Indian Head Division of the

Naval Surface Warfare Center The Naval Surface Warfare Center (NSWC) is part of the Naval Sea Systems Command (NAVSEA) operated by the United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United Sta ...

. 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. 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. An application of the sol-gel method, developed by Randall Simpson, Alexander Gash and others at the

Lawrence Livermore National Laboratory Lawrence Livermore National Laboratory (LLNL) is a Federally funded research and development centers, federally funded research and development center in Livermore, California, United States. Originally established in 1952, the laboratory now i ...

, 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. 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.

Ignition

As with all explosives, research into control yet simplicity has been a goal of research into nanoscale explosives. Some can be ignited with

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...

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

lead styphnate Lead styphnate (lead 2,4,6- trinitroresorcinate, C6HN3O8Pb ), whose name is derived from styphnic acid, is an explosive used as a component in primer and detonator mixtures for less sensitive secondary explosives. Lead styphnate is only slight ...

lead azide Lead(II) azide is an inorganic compound. More so than other azides, it is explosive. It is used in detonators to initiate secondary explosives. In a commercially usable form, it is a white to buff powder. Preparation and handling Lead(II) azi ...

) in

percussion cap The percussion cap, percussion primer, or caplock, introduced in the early 1820s, is a type of single-use percussion ignition device for muzzle loader firearm locks enabling them to fire reliably in any weather condition. Its invention gave ...

s and

electric match An electric match is a device that uses an externally applied electric current to ignite a combustible compound. Electric matches use a bridgewire consisting of a heating element to ignite a pyrogen, which is a quantity of readily ignited pyrotec ...

es. Compositions based on Al-Bi₂O₃ tend to be used.

PETN Pentaerythritol tetranitrate (PETN), also known as PENT, pentyl, PENTA (''ПЕНТА'', primarily in Russian), TEN (tetraeritrit nitrate), corpent, or penthrite (or, rarely and primarily in German, as ''nitropenta''), is an explosive material. ...

may be optionally added.

powder can be added to nano

explosives An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...

has a relatively low combustion rate and a high

enthalpy of combustion The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The ''calorific value'' is the total energy release ...

. 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.

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 Electrostatic discharge (ESD) is a sudden and momentary flow of electric current between two differently-charged objects when brought close together or when the dielectric between them breaks down, often creating a visible electric spark, spark as ...

(ESD). Surrounding the metal oxide particles with carbon nanofibers may make nanothermites safer to handle.

References

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
* {{cite thesis , author=John J. Granier , publisher=Texas Tech University , title=Combustion Characteristics of Al Nanoparticles and Nanocomposite Al+MoO₃ Thermites , date=May 2005 , url=http://etd.lib.ttu.edu/theses/available/etd-05032005-162438/unrestricted/JGranier_dissertation_FINAL.pdf , access-date=May 3, 2009 , type=PhD thesis , archive-url=https://web.archive.org/web/20080908063107/http://etd.lib.ttu.edu/theses/available/etd-05032005-162438/unrestricted/JGranier_dissertation_FINAL.pdf , archive-date=September 8, 2008 , url-status=dead Incendiary weapons Explosives Nanoparticles Pyrotechnic compositions

Potential uses

Types

Production

Ignition

Hazards

See also

References

External links