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

oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...

, 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#-re ...

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

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 ). In other words, an oxid ...

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 commonly reducing agents include the Earth meta ...

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

reactive material In the United States Department of Defense, 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 fragmentati ...

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

pyrotechnics Pyrotechnics is the science and craft of creating such things as fireworks, safety matches, oxygen candles, explosive bolts and other fasteners, parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demolition. ...

. What distinguishes MICs from traditional

thermite 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 ...

s is that the oxidizer and a reducing agent, normally

iron oxide Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of whic ...

and

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

, are in the form of extremely fine powders (

nanoparticle A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 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 1 ...

s). This dramatically increases the reactivity relative to

micrometre The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...

-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 other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...

s, explosives,

incendiary device Incendiary weapons, incendiary devices, incendiary munitions, or incendiary bombs are weapons designed to start fires or destroy sensitive equipment using fire (and sometimes used as anti-personnel weaponry), that use materials such as napalm, th ...

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, a vacuum bomb or a fuel air explosive (FAE), is a type of explosive that uses oxygen from the surrounding air to generate a high-temperature explosion. The fuel–air explosive is one of the be ...

are one potential application of nanoenergetic materials.

Types

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

Aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

molybdenum(VI) oxide Molybdenum trioxide describes a family of inorganic compounds with the formula MoO3(H2O)n where n = 0, 1, 2. These compounds are produced on the largest scale of any molybdenum compound. The anhydrous oxide is a precursor to molybdenum metal, ...

* 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. It i ...

* Aluminium-

iron(II,III) oxide Iron(II,III) 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 (Fe2O3) which also occur ...

Antimony Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient time ...

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

* Aluminium-

bismuth(III) oxide Bismuth(III) oxide is perhaps the most industrially important compound of bismuth. It is also a common starting point for bismuth chemistry. It is found naturally as the mineral bismite (monoclinic) and sphaerobismoite (tetragonal, much more rare) ...

* 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 ye ...

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 with the 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 with the 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 th ...

(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 describes a family of inorganic compounds with the formula MoO3(H2O)n where n = 0, 1, 2. These compounds are produced on th ...

, aluminium-

Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemou ...

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

RDX RDX (abbreviation of "Research Department eXplosive") or hexogen, among other names, is an organic compound with the formula (O2N2CH2)3. It is a white solid without smell or taste, widely used as an explosive. Chemically, it is classified as a n ...

and with

thermoplastic A thermoplastic, or thermosoft 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 associate ...

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

PTFE Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemour ...

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. 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 laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...

. A variant of the method is being used at the

Indian Head Division Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

of the

Naval Surface Warfare Center * A Naval Surface Warfare Center (NSWC) is part of the Naval Sea Systems Command (NAVSEA) operated by the United States Navy. NAVSEA Warfare Centers supply the technical operations, people, technology, engineering services and products needed t ...

. 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. Current production levels are now beyond 100 kg/month. 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 federal research facility in Livermore, California, United States. The lab was originally established as the University of California Radiation Laboratory, Livermore Branch in 1952 in response ...

, 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.

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" is an acronym for "light amplification by stimulated emission of radiation". The fir ...

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 slightly ...

lead azide Lead(II) azide is an inorganic compound. More so than other azides, 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) azide is ...

) in

percussion cap The percussion cap or percussion primer, 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. This crucial invention gave rise t ...

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, PENTA, (ПЕНТА, primarily in Russian) TEN, corpent, or penthrite (or, rarely and primarily in German, as nitropenta), is an explosive material. It is the nitrate ester of pentaerythri ...

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 expl ...

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 relea ...

. 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 electrically charged objects caused by contact, an short circuit, electrical short or dielectric breakdown. A buildup of static electricity can be caused ...

(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 book, 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, postscript=(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 Pyrotechnic compositions Incendiary weapons Explosives Nanoparticles

Potential uses

Types

Production

Ignition

Hazards

See also

References

External links