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

pyrophoric A substance is pyrophoric (from , , '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 organolithium compounds and triethylb ...

alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

of mischmetal (

cerium Cerium is a chemical element; it has Chemical symbol, symbol Ce and atomic number 58. It is a hardness, soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it ...

, lanthanum,

neodymium Neodymium is a chemical element; it has Symbol (chemistry), 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 element, rare-earth metals. It is a hard (physics), hard, sli ...

, other trace

lanthanides The lanthanide () or lanthanoid () series of chemical elements comprises at least the 14 Metal, metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium. In the periodic table, they fill the 4f orbitals. Lutetium ...

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

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

and/or

magnesium Magnesium is a chemical element; it has Symbol (chemistry), 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 ...

. When struck with a harder material,

friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...

produces hot fragments that oxidize rapidly when exposed to the oxygen in the air, producing sparks that can reach temperatures of . The effect is due to the low ignition temperature of cerium, between . Ferrocerium has many commercial applications, such as the ignition source for lighters, strikers for gas welding and cutting torches, deoxidization in

metallurgy Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys. Metallurgy encompasses both the ...

, 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

firelighting Fire making, fire lighting or fire craft is the process of artificially starting a fire. It requires completing the fire triangle, usually by heating tinder above its autoignition temperature. Fire is an essential tool for human survival and t ...

device in

survival kit A survival kit is a package of basic tools and supplies prepared as an aid to survival skills, survival in an emergency. Civil and military aircraft, lifeboat (shipboard), lifeboats, and spacecraft are equipped with survival kits. Survival ki ...

s. The ferrocerium is referred to as a "flint" in this case, as both are used in fire lighting. However, ferrocerium and natural flint have opposite mechanical operation.

Discovery

A spark lighter in action Ferrocerium alloy was invented in 1903 by the Austrian chemist Carl Auer von Welsbach. It takes its name from its two primary components:

(from ), and the rare-earth element

, which is the most prevalent of the

in the mixture. Except for the extra iron and

magnesium oxide Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions ...

s added to harden it, the mixture is approximately the combination found naturally in tailings from

thorium Thorium is a chemical element; it has symbol Th and atomic number 90. Thorium is a weakly radioactive light silver metal which tarnishes olive grey when it is exposed to air, forming thorium dioxide; it is moderately soft, malleable, and ha ...

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 upright=1.2, Crystals of lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals is a controversial and ambiguous term for metallic elements with relatively h ...

. A modern ferrocerium firesteel product is composed of an

rare-earth metal The rare-earth elements (REE), also called the rare-earth metals or rare earths, and sometimes the lanthanides or lanthanoids (although scandium and yttrium, which do not belong to this series, are usually included as rare earths), are a set of ...

s called mischmetal, containing approximately 20.8% iron, 41.8% cerium, about 4.4% each of praseodymium,

, 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 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 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 a striker, similarly to natural flint-and-steel, though ferrocerium takes on the opposite role to the traditional system; instead of a natural flint rock striking tiny iron particles from a firesteel, a striker (which may be in the form of hardened steel wheel) strikes particles of ferrocerium off of the "flint". This manual rubbing action creates a spark due to cerium's low ignition temperature between . Any material that is harder than the rod itself may be used to produce sparks. Though the striker must have a sharp corner, sharp edge, or a knurled surface in order to produce sparks, carbon steel is not required. The idea that carbon steel is needed to produce sparks from a ferrocerium rod is an oft repeated myth, though carbon steel does make the spark more prevalent when striking. Ferrocerium is most commonly used to start Bunsen burners and oxyacetylene welding torches. About 700 tons were produced in 2000.

References

External links

* {{Firelighting Ferroalloys Fire making Pyrophoric materials