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Material World
Element · C

Carbon

The element whose two common crystal forms — diamond and graphite — differ more from each other than almost any other pair of substances.

Carbon is the standard example of why crystal structure matters as much as composition. Diamond and graphite are both pure carbon. Diamond is the hardest natural substance known and an electrical insulator; graphite is soft enough to write with and conducts electricity. Nothing about the chemistry distinguishes them — only the arrangement of the atoms.

This is the reason Material World treats polymorphs as separate entities rather than as variants of one substance. Calling them both 'carbon' and stopping there discards the fact that actually matters.

Uses

Carbon's uses span almost the whole range of materials science because its allotropes have almost nothing in common. Graphite lubricates, moderates reactors, and forms the anode of every lithium-ion battery. Diamond cuts and grinds what nothing else will. Carbon black reinforces rubber and is why tyres are black.

Carbon fibre gives composites their stiffness. Activated carbon filters water and air by adsorption. Coke reduces iron ore to iron, which is the single largest industrial use of carbon by mass, and carbon in solution is what turns iron into steel.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is found in

  • Diamond — mineral Wikidata
  • Graphite — mineral Wikidata
  • Silicon carbide — compound
  • Polyethylene — material
  • Wood — material
  • Aragonite — mineral Wikidata
  • Paper — material · as cellulose
  • Polyvinyl chloride — material
  • Natural rubber — material
  • Tungsten carbide — compound · the other half of the formula, and what turns a hard metal into a very hard ceramic Wikidata
  • Air — material · as carbon dioxide, at a few hundredths of one per cent — the component that does most of the arguing in public
  • Polypropylene — material · the backbone, and a methyl group on every second one — the arrangement of those groups is what decides whether the material is useful or a gum
  • Polyethylene terephthalate — material · the backbone and the aromatic ring that makes the chain stiff enough to hold a bottle's shape
  • Nylon — material · the chain between the links
  • Polystyrene — material · the backbone and a benzene ring hanging off every second atom, which is what makes it rigid and brittle at once
  • Polytetrafluoroethylene — material · the chain, entirely shielded — there is nothing for a reagent to reach
  • Polycarbonate — material · the backbone and the aromatic rings that supply the stiffness
  • Coal — rock · the defining constituent, rising from about sixty per cent in lignite to over ninety in anthracite as the other elements are driven off
  • Shale — rock · as organic matter in the black shales, where oxygen-poor bottom water preserved it — the same preservation that made coal, in a different setting
  • Cotton — material · the backbone of the cellulose the fibre is made of
  • Wool — material · the protein backbone of keratin
  • Silk — material · the protein backbone
  • Seawater — material · as dissolved carbonate and bicarbonate, in a reservoir far larger than the atmosphere's — which is why the ocean takes up so much of what is emitted, and why it is acidifying
  • Ethylene — compound · two of them, joined by the double bond that is the whole of its usefulness
  • Propylene — compound · three, one of them the methyl group that makes polypropylene stiffer than polyethylene
  • Styrene — compound · eight, six of them in the benzene ring that stiffens every polymer it goes into
  • ABS — material · the backbone of all three monomers
  • PMMA — material · the backbone and the ester side group
  • POM — material · alternating with oxygen — the backbone is nothing but carbon and oxygen, which is unusual and is where the crystallinity comes from
  • PEEK — material · aromatic rings throughout, which is where the thermal stability comes from
  • PLA — material · the backbone, and it came out of the atmosphere within the last growing season rather than out of the ground
  • Aramid fibre — material · aromatic rings in the backbone, which is what makes the molecule a rigid rod rather than a flexible chain
  • Silicone rubber — material · only in the methyl groups on the silicon, which is why it burns poorly and ages so well
  • Neoprene — material · the backbone
  • Epoxy resin — material · the aromatic backbone of the common bisphenol-based resins
  • Polyurethane — material · the backbone of both components
  • Phenolic resin — material · aromatic rings crosslinked into a network dense enough that the material chars rather than melts
  • Crude oil — material · the bulk of it, in molecules from one carbon to fifty and more
  • Naphtha — material · five to ten per molecule, which is what defines the cut
  • Tool steel — alloy · 0.3–2.5% · the element that makes hardening possible at all — below about 0.3 per cent no useful martensite forms
  • High-speed steel — alloy · 0.7–1.5% · without which none of the carbides form
  • Wootz steel — alloy · 1–2% · around 1.5 per cent, high enough that the carbide bands which produce the pattern can form
  • Lime mortar — material · as carbonate — driven off in the kiln and reabsorbed from the air as the mortar sets
  • Carbon fibre composite — material · the fibre, and it is electrically conductive — which is why an aluminium fitting bolted to it corrodes
  • Resin — material · the terpene backbone, and most of the mass
  • Amber — material · around 79 per cent — it is a hydrocarbon polymer, and this is why it burns
  • Jet — material · the great majority — jet is lignite, and the rank of a coal is a statement about how much of everything else has been driven out
  • Nacre — material · in the carbonate, and in the chitin and protein of the matrix
  • Bone — material · in the collagen, and as carbonate substituting into the mineral
  • Charcoal — material · the great majority, and rising with the kiln temperature — the higher the burn the less of the wood's volatile fraction is left in it
  • Peat — material · and peatlands hold roughly a third of all soil carbon on about three per cent of the land, which is more than every forest in the world combined
  • Beeswax — material · the long hydrocarbon chains that are most of it — mostly esters of fatty acids and long-chain alcohols
  • Battery graphite — material · better than 99.95 per cent of it, which is most of what the processing is for
  • Azurite — mineral Wikidata
  • Bastnäsite — mineral
  • Calcite — mineral Wikidata
  • Malachite — mineral Wikidata
  • Strontianite — mineral Wikidata

is a component of

  • Steel — alloy · 0.02–2.1% · the element whose proportion separates steel from iron and governs its hardness
  • Carbon fibre — material · 92–100% · carbonised from a polymer precursor until little but carbon remains
  • Cast iron — alloy · two to four per cent, which drops the melting point enough to pour and precipitates as graphite flakes

is used as

  • Alloying — application · the addition that turns iron into steel

is produced by

  • Acheson process — process · as synthetic graphite, made by driving the reaction past silicon carbide until the silicon boils away and leaves the carbon behind

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • PubChem
    US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors

Questions this page answers

Where it comes from, and what it becomes

Follow Carbon back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Carbon → is produced by (as synthetic graphite, made by driving the reaction past silicon carbide until the silicon boils away and leaves the carbon behind) → Acheson process → takes as input (sand and coke, heated to 2,500 °C, which is how silicon carbide has been made since 1893) → Sand → is sourced from (the ultimate source of most of it — granite weathers, the feldspar becomes clay and washes out, and the quartz survives as grains) → Granite → is composed of (by volume, alongside feldspar and lesser mica) → Quartz
  • Carbon → is produced by (as synthetic graphite, made by driving the reaction past silicon carbide until the silicon boils away and leaves the carbon behind) → Acheson process → takes as input (as silica sand, the silicon half of the charge) → Quartz
  • Carbon → is produced by (as synthetic graphite, made by driving the reaction past silicon carbide until the silicon boils away and leaves the carbon behind) → Acheson process → takes as input (sand and coke, heated to 2,500 °C, which is how silicon carbide has been made since 1893) → Sand → is composed of (almost everywhere, because quartz is what is left when everything else in a rock has weathered away — though a volcanic beach is basalt grains and a tropical one is broken shell) → Quartz
  • Carbon → is produced by (as synthetic graphite, made by driving the reaction past silicon carbide until the silicon boils away and leaves the carbon behind) → Acheson process → takes as input (sand and coke, heated to 2,500 °C, which is how silicon carbide has been made since 1893) → Sand → is sourced from (the ultimate source of most of it — granite weathers, the feldspar becomes clay and washes out, and the quartz survives as grains) → Granite → is composed of (the pink or cream mineral that gives much granite its colour) → Orthoclase
  • Carbon → is produced by (as synthetic graphite, made by driving the reaction past silicon carbide until the silicon boils away and leaves the carbon behind) → Acheson process → takes as input (sand and coke, heated to 2,500 °C, which is how silicon carbide has been made since 1893) → Sand → is sourced from (the ultimate source of most of it — granite weathers, the feldspar becomes clay and washes out, and the quartz survives as grains) → Granite → is composed of (one of the two common micas in granite, alongside biotite) → Muscovite
  • Carbon → is produced by (as synthetic graphite, made by driving the reaction past silicon carbide until the silicon boils away and leaves the carbon behind) → Acheson process → takes as input (sand and coke, heated to 2,500 °C, which is how silicon carbide has been made since 1893) → Sand → is sourced from (the ultimate source of most of it — granite weathers, the feldspar becomes clay and washes out, and the quartz survives as grains) → Granite → is composed of (alongside the potassium feldspar and quartz) → Plagioclase

These are the most distinct paths back. Carbon can be traced through others besides.

Downstream — what it becomes

  • Carbon → is a component of (two to four per cent, which drops the melting point enough to pour and precipitates as graphite flakes) → Cast iron → is an input to (as pig iron tapped from the blast furnace, carrying the carbon the process removes) → Basic oxygen steelmaking → produces (most of the world's primary steel) → Steel → is associated with (produced in small quantities long before it could be made reliably) → Iron Age complete chain
  • Carbon → is a component of (the element whose proportion separates steel from iron and governs its hardness) → Steel → is associated with (produced in small quantities long before it could be made reliably) → Iron Age complete chain
  • Carbon → is a component of (carbonised from a polymer precursor until little but carbon remains) → Carbon fibre → is used in (in the spar caps of the longest blades, where stiffness stops the tip striking the tower) → Wind turbine blade → is used in (and it is the part of a turbine with no established end-of-life route, where the tower and foundation are steel and concrete) → Energy generation
  • Carbon → is used as (the addition that turns iron into steel) → Alloying
  • Carbon → is a component of (two to four per cent, which drops the melting point enough to pour and precipitates as graphite flakes) → Cast iron → is associated with (the material of the later industrial expansion rather than of the period itself) → Iron Age complete chain
  • Carbon → is a component of (the element whose proportion separates steel from iron and governs its hardness) → Steel → is an input to (and the same steel becomes a spring, a cutting edge or a machinable bar depending only on the schedule) → Heat treatment → produces (laid up as fibre and resin and cured under heat and pressure, usually in an autoclave — and the cure schedule is as much of the specification as the fibre is) → Carbon fibre composite → is used as (aircraft primary structure since the 1990s, where stiffness per unit mass is what is being bought) → Structural engineering

These are the most distinct paths onward. Carbon ends up in others besides.