Ferrocerium (also known in Europe as Auermetall) is a synthetic

pyrophoric A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolit ...

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...

mischmetal Mischmetal (from german: Mischmetall – "mixed metal") is an alloy of rare-earth elements. It is also called cerium mischmetal, or rare-earth mischmetal. A typical composition includes approximately 55% cerium, 25% lanthanum, and 15 ...

(

cerium Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the +3 ...

, lanthanum,

neodymium Neodymium is a chemical element with the symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth metals. It is a hard, slightly malleable, silvery metal that quickly tarnishe ...

, other trace

lanthanides The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and ytt ...

and some iron – about 95% lanthanides and 5% iron) hardened by blending in oxides of

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

and/or

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

. When struck with a harder material, the mixture produces hot sparks that can reach temperatures of when rapidly oxidized by the process of striking the rod. Striking both scrapes fragments off, exposing them to the oxygen in the air, and easily ignites them by

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of ...

heat due to cerium's remarkably low ignition temperature of ~. Its easy flammability gives ferrocerium many commercial applications, such as the ignition source for lighters, strikers for gas welding and cutting torches, deoxidization in metallurgy, and ferrocerium rods. Because of ferrocerium's ability to ignite in adverse conditions, rods of ferrocerium (also called ferro rods, spark rods, and flint-spark-lighters) are commonly used as an emergency fire lighting device in

survival kit A survival kit is a package of basic tools and supplies prepared as an aid to survival in an emergency. Civil and military aircraft, lifeboats, and spacecraft are equipped with survival kits. Survival kits, in a variety of sizes, contain su ...

s. The ferrocerium is referred to as a "flint" in this case despite being dissimilar to

natural flint Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and start fires ...

as both are used in conjunction for fire lighting, albeit with opposite mechanical operation.

Discovery

A spark lighter in action Ferrocerium alloy was invented in 1903 by the Austrian chemist

Carl Auer von Welsbach Carl Auer von Welsbach (1 September 1858 – 4 August 1929), who received the Austrian noble title of Freiherr Auer von Welsbach in 1901, was an Austrian scientist and inventor, who separated didymium into the elements neodymium and praseo ...

. It takes its name from its two primary components:

(from la, ferrum), and the

rare-earth element The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides ( yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silv ...

, which is the most prevalent of the

in the mixture. Except for the extra iron and magnesium oxides added to harden it, the mixture is approximately the combination found naturally in

tailings In mining, tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different to overburden, which is the waste rock or other material that overli ...

from

thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high ...

mining, which Auer von Welsbach was investigating. The pyrophoric effect is dependent on the brittleness of the alloy and its low autoignition temperature.

Composition

In Auer von Welsbach's first

, 30% iron (ferrum) was added to purified

, hence the name "ferro-cerium". Two subsequent Auermetalls were developed: the second also included lanthanum to produce brighter sparks, and the third added other heavy metals. A modern ferrocerium firesteel product is composed of an

of rare-earth metals called

, containing approximately 20.8% iron, 41.8% cerium, about 4.4% each of

praseodymium Praseodymium is a chemical element with the symbol Pr and the atomic number 59. It is the third member of the lanthanide series and is considered to be one of the rare-earth metals. It is a soft, silvery, malleable and ductile metal, valued for i ...

, and

, plus 24.2% lanthanum. A variety of other components are added to modify the spark and processing characteristics. Most contemporary flints are hardened with iron oxide and magnesium oxide.

Uses

A Mora knife with a ferrocerium rod that can be stored in the handle Ferrocerium is used in fire lighting in conjunction with steel, similarly to natural flint-and-steel, though ferrocerium takes on the opposite role to the traditional system; instead of a

rock striking tiny iron particles from a

firesteel A fire striker is a piece of carbon steel from which sparks are struck by the sharp edge of flint, chert or similar rock. It is a specific tool used in fire making. History In early times, percussion fire making was often used to start fir ...

, a steel striker (which may be in the form of hardened steel wheel) strikes particles of ferrocerium off of the "flint". This manual rubbing action, done by squeezing the handle, creates a spark due to cerium's low ignition temperature between . Carbon steel works better than most other materials, in much the same way natural flint and firesteel are used. It is most commonly used for

Bunsen burner A Bunsen burner, named after Robert Bunsen, is a kind of ambient air gas burner used as laboratory equipment; it produces a single open gas flame, and is used for heating, sterilization, and combustion. The gas can be natural gas (which is ma ...

s, propane grills, and oxyacetylene welding torches. About 700 tons were produced in 2000.

References

External links

* {{Firelighting Ferroalloys Firelighting using percussion