Fifty Materials That Make the World

If you Google “ABS”, you’ll likely get “anti lock brakes” or a reference to stomach muscles. ABS is also the acronym for Acrylonitrile Butadiene Styrene, the most popular engineering polymer - an engineering polymer is one that is used because of its mechanical properties. You have undoubtedly pounded on this material since one of its many applications is for computer keyboards. ABS plastic is an amorphous (lacks the long range order associated with crystals) thermoplastic (one that can repeatedly re-melted) with a glass transition temperature (when it gets significantly softer) of 105 °C and, thus, is easy to manufacture into products by extrusion or injection molding at relatively low temperatures of 204–238 °C. It is also easy to machine.

This is not like the lyrics of the George and Ira Gershwin song “Let’s Call the Whole Thing Off” sung by Fred Astaire and Ginger Rogers in the 1937 film “Shall We Dance”, of “you say tomatoes (to-may-toes), I say tomatoes (to-mah-toes)”. Americans and British pronounce the name of this element differently because they spell it differently. The metal was named aluminum even before it was first isolated by the British chemist Humphrey Davy (1778–1829) in 1807. The name was later changed to aluminium to bring its spelling more in line with other metallic elements that end in “ium”, a name that was adopted by the International Union of Pure and Applied Chemistry. Oddly, in 1925 the American Chemical Society decided to revert to the original name aluminum, which is now the usage in America, while elsewhere in the English-speaking world it is still aluminium. Whichever spelling you use, the name is derived from Alum, the common name of hydrated potassium aluminum sulfate.

If asked what is one of the most recycled materials, you might not expect the answer to be asphalt concrete., Asphalt concrete roads, that is roads made from a mixture of around 5% asphalt with an aggregate that contains stone, sand and gravel, date to only 1903 when British inventor Edgar Purnell Hooley (1860–1942) obtained a patent for tarmac in which he premixed asphalt and aggregate that was laid on the road and steamrolled. Hooley subsequently started the Tar Macadam Syndicate Ltd. The first tarmac road was Radcliffe Road in Nottingham, England. Tarmac built on earlier work by Scotsman John Loudon McAdam (1756–1836) who pioneered the use of macadam roads in the 1820s. Unfortunately, these early roads were less than optimum and were prone to generate dust and to rutting. Thus, around 1834, John Henry Cassel improved road building by starting with a tar layer, adding a layer of McAdam’s material and finishing with a mixture of tar and stone.

Invented in 1907 in Yonkers, New York, phenolformaldehyde was the first thermosetting polymer, that is, a polymer that once it has set can’t be remelted. The polymer was called Bakelite, or more properly Baekelite after its inventor the American chemist Leo Henricus Arthur Baekeland (1863–1944). One of its first uses may have been for the knob on a gear lever in a Rolls Royce automobile. Bakelite provided the long-sought solution to replace ivory for billiard balls and is now also used for bowling balls.

Imagine that you are on a battlefield somewhere in the Middle East at the beginning of the Bronze Age. You advance with your copper sword and engage a foe armed with a bronze sword (a copper-tin alloy). He swings, you parry and your sword bends. Hopefully, you have time to retreat and bend your sword straight before you are slain. Whether such a scenario would have happened is debatable. The copper swords would have likely accidentally contained arsenic, which make them harder. Indubitably, bronze swords could keep a sharper edge. In fact, some swords made in China as early as the Warring States period (475–221 B.C.) were engineered to have a high tin content (17–21% tin) along the edge, which makes it harder and better at holding an edge but more brittle, while the center of the sword has a lower tin content (10%) and is softer but more ductile.

Celluloid is a material that was invented to solve a materials shortage in a game – which it didn’t really do – but ended up in a enabling a whole new industry.

Clay seems mundane, but it provided essentials for life for our Ancestors in the form of shelter and as food storage containers, see Fig. 7.1. It’s use led to the advancement of civilization by providing a medium to record data, which eventually evolved into writing, and for artistic expression. The use of clay by early humans to make containers, cooking pots, counting tokens, musical instruments, bricks and figurines of gods or goddesses occurred throughout the World.

If you ask most people what the most commonly used material is, they might say wood, or steel, or aluminum. The correct answer is actually concrete, which is used in larger quantities than the combined weight of all metals used in a year. Twice as much concrete is used as all other building materials - three tonnes per person are used annually. Another common belief about concrete is that when concrete is being used it has to “dry out”. In fact, concrete is a composite material consisting of rock and sand that are “glued” together by cement which itself undergoes a complex set of reactions with water during which it hardens.

Copper is a commonly-encountered metal and most people would easily recognize a piece. So the perception may be that it is common metal, but it is not. It comprises only 0.0068% of the Earth’s crust. By comparison, iron and aluminum are 6.3% and 8.1% of the Earth’s crust, respectively. The name copper comes from the Latin name aes cyprium or the “Cypriot metal”, which later became cuprum – Cyprus being a major source of copper in Roman times. Elemental copper, which is a reddish-orange color face-centered cubic metal (like aluminum), is one of only four colored metals – the others are the bluish element osmium, and the yellow-colored gold and cesium.

The innocuous-looking, even delicate cotton boll has had a huge impact on history. Whether the Glorious Revolution of 1688 provided the legal and cultural genesis of the Industrial Revolution in Great Britain is still debated, but technologically the steam engines of Thomas Savery (1650–1715) and Thomas Newcomen (1650–1715), patented in 1698 and developed about 1712, respectively, and later improved in a new design of 1781 by James Watt (1736–1819) were fundamental to the industrial revolution as machines initially to pump water from mines and later to power factories and mills. Improvements in metallurgy and mining were also very important, as was the production of wool and linen, but the mechanization of cotton production was the greatest showcase of the First Industrial Revolution providing gains of factors of 40–50 in output per person.

“Diamonds are Forever” according to the 1956 Ian Fleming novel, which was made into a film in 1971, about the British secret agent James Bond. Diamonds may last an awfully long time but they are not forever. Diamond is a metastable (long-lived, but not equilibrium) crystalline form of carbon that has a crystal structure referred to as diamond cubic, which is also adopted by both silicon and germanium. The stable or equilibrium form of carbon is graphite, the stuff in the middle of your “lead” pencil. However, not to worry, even though diamonds are only metastable, if kept at room temperature it will likely take billions of years before they turn into graphite. On the other hand, they will burn if heated to 850–1000 °C generating the far less valuable greenhouse-gas carbon dioxide.

You have probably never seen gallium arsenide (GaAs) and may not have even heard of it but every day you likely encounter devices that use this metallic compound and its related compounds aluminum gallium arsenide and indium gallium arsenide. Gallium arsenide has a similar crystal structure to silicon, but each atom of gallium has an arsenic atom nearest neighbor and vice versa. These materials are the core, along with the compound indium phosphide and its derived compounds (which are mostly used in telecommunications), of semiconductor lasers, which are also sometimes called semiconductor diodes or injection lasers. The function of a semiconductor laser is to turn electrical energy into light energy in a directed narrow beam. The best semiconductor lasers can turn around 70% of the input electrical power into light.

Glass is a supercooled liquid in which the atoms do not have time during cooling from the melt to find their correct locations to form a crystal. The simplest glass, composed of the two elements that are most common in the Earth’s crust, is pure silica or silicon dioxide (SiO₂), which melts at over 1650 °C. The resulting glass is called fused silica or quartz glass. It has low thermal expansion of 5.5 × 10–7 °C−1 (one third of that of common soda-lime glass), is very resistant to thermal shock, corrosion resistant, is hard, and is strong at high temperature. Thus, it is used in applications like chemical glassware and furnace tubes and crucibles. It is, of course more expensive than soda-lime glass because of the high temperature required to melt it.

Glass fiber reinforced polymer (GFRP), commonly called fiberglass, is used for a huge variety of applications including boat hulls, car bodies, roofing shingles, pipes, flooring and various containers and storage tanks. GFRP is referred to as a composite material since it is a combination of two different materials, that is, glass fibers in the form of either a woven fabric or a chopped mat in a polymer matrix. Most often used for the matrix are the thermosetting polymers (polymers which cannot be remelted) epoxy or polyester, and less-commonly the thermosetting polymers vinyl ester, phenolics and silicones, or the thermoplastic polymers (polymers which can be remelted) nylon, polycarbonate and polystyrene. The fibers are coated with a coupling agent to aid bonding to the polymer matrix and a sizing agent to protect the fibers.

Transmutation of a base metal into gold (symbol Au from the Latin Aurum) is possible not through the alchemist’s chemistry, but by nuclear transmutation as demonstrated by the American Glenn Seaborg (1912–1999) and his collaborators who turned bismuth into gold using a particle accelerator at the Lawrence Berkeley Laboratory in California in 1981. Turning lead into gold by such an approach is difficult and definitely not a profitable venture - the reverse nuclear transmutation is easier but even less valuable.

Carbon exists in many forms: as the crystalline allotropes graphite and diamond, as amorphous carbon, and as the nanomaterials carbon nanotubes, graphene and Buckminsterfullerene that was named after Buckminster Fuller (1895–1983) and more often called buckyballs or fullerenes. The last three forms are one-dimensional, two-dimensional and three-dimensional nanostructures that were first synthesized in 1991, 2004 and 1985, respectively. The British chemist Harold Kroto (1939–2016) and the two American chemists Robert Curl (1933-) and Richard Smalley (1943–2005) were awarded the 1996 Nobel Prize in Chemistry for their discovery of buckyballs, while two British physicists Andre Geim and Konstantin Novoselov were awarded the 2010 Nobel Prize in Physics for their isolation of graphene. Carbon nanotubes were first synthesized by Japanese researcher Sumio Iijima (1939-). Only graphite, which is found naturally as a gray metallic-looking mineral, is the stable or equilibrium form of carbon.

Gutta Percha has few uses nowadays apart from in endodontics, for which it has been used for over 150 years. Gutta Percha, or technically trans-1,4-polyisoprene, is chemically identical to latex or natural rubber, which is cis-1,4-polyisoprene. Such molecules that are chemically the same but differ in the spatial arrangements of the atoms are referred to as stereoisomers. This difference is important since latex is amorphous (non-crystalline) whereas Gutta Percha crystallizes when it solidifies. While latex is produced from the sap of a rubber tree, Gutta Percha is a milky latex-like substance produced from a tree whose Malay name is Getah Perca. The Malay people had used Gutta Percha for many centuries before its introduction to the West in applications such as handles for knives and walking sticks amongst other uses.

Iron, a lustrous silvery, malleable, very ductile metal, exists in three different crystal structures or allotropes: up to 912 °C it is body centered cubic (b.c.c.); from 912-1394 °C it is face centered cubic (f.c.c.); and from 1394 °C up to the melting point of 1538 °C it is again b.c.c., see Fig. 18.1. Iron is the fourth most abundant element in the Earth’s crust at 6.3% and the second most abundant metal after aluminum at 8.1%. In addition, the Earth’s inner and outer cores, which constitute 35% of the mass of the planet, are composed of iron and nickel.

The name poly-paraphenylene terephthalamide, doesn’t exactly roll of the tongue, which is presumably why Dupont gave it the much cooler commercial name of Kevlar. Kevlar was invented by Stephanie Louise Kwolek (1923–2014) and Paul Wintrop Morgan (1911–1992) at E. I. du Pont de Nemours and Company for which US patent 3287323A “Process for the production of a highly orientable, crystallizable, filament forming polyamide” was awarded in 1966. It is produced by the condensation reaction between 1,4-phenylene-diamine and terephthaloyl chloride: the condensate, that is the chemical left over from the reaction, is hydrochloric acid. Mechanical drawing of the product produces Kevlar fibers. Kevlar can be considered one of a family of aromatic polyamide, which is usually contracted to “aramid”, fibers that include Nomex, Technora, Teijinconex and Twaron.

Lead is a bluish-white face centered cubic (f.c.c.) metal that usually looks gray due to the rapid formation of an oxide or a carbonate on the surface. Lead appears to be the first metal smelted from its ore, typically galena. The earliest known site, which dates from the early sixth millennium B.C., is Çatalhöyü in current-day Turkey. Both sculptures and coins made from lead have been found in Egyptian tombs dated to 5000 B.C. The Romans used lead extensively for utensils, drinking vessels and bowls, ballistics, cosmetics and for plumbing. The word plumbing is derived from the Latin for lead Plumbum, which is also the origin of the chemical symbol for lead of Pb and of plumb bob and plumb line (a weight attached to a line), which are used for determining verticals or the depth of water. Many of these uses meant that Romans were sure to have ingested significant amounts of lead.

Ceramics are inorganic, non-metallic, solids that consist of a metal, a non-metal, a metalloid such as silicon, or a combination of these. Ceramics utilize ionic or covalent bonding, or both. When thinking of a ceramic you may think of pottery. This is perfectly reasonable since the word “ceramic” is derived from the Greek word keramikos, which means “of pottery” or “for pottery”. “Keramic” is an old, rare, now disused spelling of “ceramic”. The main commercial piezoelectric ceramic is Lead Zirconium Titanate with a typical composition of PbZr0.52Ti0.48O3. It is referred to a PZT and adopts the perovskite crystal structure.

When you think of leather you likely think of shoes, bags, belts, jackets and other clothing. The Assyrians, Ancient Egyptians, Ancient Greeks and Romans are all known to have used leather goods, clothes and footwear. Leather has even been used as part of armor. Animal skins, a by-product of killing animals for food, have likely been used for shoes, clothing, and tents for as long as mankind has been killing animals. Animal skins have also been used as parchment for writing since the Bronze Age. But skins easily rot and smell if too wet, become stiff at low temperatures and can be damaged by higher temperatures.

You may remember lithium from high school chemistry where a favorite demonstration is to put lithium on water. Yes, on water. Lithium with an atomic number of 3 is the element with the lowest atomic number that is solid at room temperature and is the lightest elemental solid at only 534 kg m−3 and, thus, is much less dense than water at 1000 kg m−3 . The lithium reacts violently with water whizzing around the surface as it forms an oxide and releases hydrogen, which burns with a blue flame. The other alkali metals that one can do this with are sodium and potassium since they are also less dense than water at 968 kg m−3 and 862 kg m−3, respectively, but their reaction with water is much more violent. Lithium is a silvery white metal that oxidizes so rapidly in air that it is stored under either argon or oil.

You may have encountered magnesium not as the metal but as milk of magnesia, which is a suspension of magnesia or magnesium oxide (Mg(OH)₂) in water, in which it is insoluble. It is taken for various digestive tract ills. You may also have encountered it in medicinal Epsom salts, named after Epsom in Surrey, England, which is magnesium sulfate (MgSO₄). If you are a car enthusiast, you will have heard of Mag Alloy wheels. Magnesium alloys were the first materials to be used for die cast wheels since they are very lightweight compared to steel, and, thus, have a high specific strength and a high damping capacity. They were first produced in the 1930s but were largely superseded by aluminum wheels in the 1960s apart from in the competitive racing market. If you are reading this in a car or on a plane, you may well be sitting on a seat whose frame is made of magnesium.

The reason that vast numbers of people fly these days is because flying is relatively inexpensive. Once the aircraft has been paid for, the big operating cost for airlines is the cost of the fuel, and fuel efficiency has increased by over 45% since the 1940s. Aircraft have become increasingly fuel efficient by changing from turbojet engines, where all the air from the compressor blades (the large blades that you can see at the front of the engine) passes through the engine, to turbofans, where most of the air traveling through the compressor blades passes around the engine, with increasingly higher bypass ratios (the amount of air that goes around the engine compared to the amount of air that passes through the engine). An essential step is to run the engine hotter, which improves efficiency. The key to doing this was the introduction and development of nickel-based superalloys used for the turbine blades in the hottest part of the engine.

Nitinol is the most prominent and most utilized of a class of seemingly magical materials called Shape Memory Alloys that can “remember” a shape from a different temperature or at a different stress. The shape memory effect was discovered by a Swedish Chemist Arne Ölander (1902–1984) in gold-cadmium alloys in 1932. The effect was later observed in a beta brass (Cu-Zn) alloy in the 1950s and in Nitinol in 1959. The name Nitinol arises because the shape memory effect was discovered in a nickel titanium alloy by William J. Buehler and Frederick Wang at the Naval Ordnance Laboratory. Hence, the name Nickel Titanium Naval Ordnance Laboratory.

At one time “nylons” was synonymous with “stockings”, but the terminology has fallen out of use as, to a large extent, as has the wearing of stockings. Nylons were introduced as an affordable alternative to silk stockings and were an instant hit. Nylon was invented at E. I. du Pont de Nemours and Company, Wilmington, DE, U.S.A. by the American chemist Wallace Carothers (1896–1937) in 1935 and in 1939, the year that Nylon stockings first went on sale, 64 million pairs were sold. This use declined rapidly to zero along with other commercial uses of Nylon, such as making toothbrush bristles, during the Second World War as Nylon was diverted to the U.S. war effort to make tire cords, flak vests, ropes and parachutes. The latter application arose when Asian supplies of silk that had been used to make parachutes dried up.

With the advent of personal computers, the paperless society was predicted by the British-American information scientist Frederick Wilfrid Lancaster (1933–2013). It didn’t quite work out that way and the amount of paper consumed continues to increase every year. In fact since Lancaster’s prediction in 1978 the amount of paper and paperboard used has roughly tripled with much of the growth coming from developing economies.

Platinum is not a common element at 3.7% × 10−7% or 0.003 parts per million (p.p.m.) in the Earth’s Crust, although it is about ten times more common than gold. It is in a group of noble precious metals in the middle of the transition metal block of the Periodic Table referred to as the platinum group metals, which includes ruthenium, rhodium, palladium, osmium and iridium. Platinum is a silvery white metal, whose name is derived from the Spanish for silver plata. Platinum, along with the platinum group metals rhodium, palladium and iridium adopts the face centered cubic crystal structure – the other two platinum group metals ruthenium and osmium adopt the hexagonal-close-packed crystal structure. Its most useful properties are that it is very malleable and, thus, can be drawn into wire and beaten in thin sheets, and its excellent corrosion and oxidation resistance.

Most likely you hadn’t considered that the clothes that you are wearing are made out of the same material as the bottle that your fizzy drink arrives in or that your expensive coffee beans are stored in. The clothing label will indicate polyester or a cotton/polyester mix, the bottle material will likely be called PET and the bag will be shiny aluminized mylar, but they are all forms of polyester.

Polyethylene, also called by its International Union of Pure and Applied Chemistry (IUPAC) systematic name polyethene, is commonly known as polythene. It is a thermoplastic polymer meaning that it can be melted (at 120–180 °C) so that it flows and can be cooled to the solid state repeatedly. The name polyethylene is derived from the fact that the molecule consists of many (poly) “mers” or repeat units of the gaseous molecule ethylene. It is the simplest possible carbon-based polymer consisting only of a backbone of carbon atoms with hydrogen atoms attached.

The last of the common thermoplastic polymers to be invented, polypropylene or propylene (PP) has a repeat unit similar to that of polyethylene except that a methyl (CH₃) group replaces one of the hydrogen atoms. This asymmetric monomer raises the possibility of producing polymers with different tacticity that is with different spatial arrangements of the methyl group. The methyl groups can be in repeating arrangement where all the methyl groups are either on only one side of the polymer chain, an arrangement referred to as isotactic, or alternate between the opposite sides of the polymer chain, an arrangement referred to as syndiotactic. The final arrangement is called atatic, which is a random arrangement of the methyl groups.

You can’t easily tell one plastic from another simply by looking at it, but most of us would easily recognize polystyrene in its foam form called expanded polystyrene or by its (Dow Chemical Company) trademarked name Styrofoam. Polystyrene, as its name suggests, is made from the monomer styrene. Styrene, a sweet smelling oily liquid, was first produced by M. Bonastre in 1831 via distillation of storax or styrax balsam, which is the resin of the Liquidambar genus of trees. Styrene, whose systematic name is Ethenylbenzene, is now one of most widely manufactured chemicals at around a 35 million tonnes annual production and growing at around 5% per year. It is now usually made by dehydrogenation of ethylbenzene. Ethylbenzene occurs naturally in petroleum, but most is produced by combining benzene and ethylene.

You may never have heard of polytetraflouroethylene (PTFE), which is quite a mouthful, but you have surely used it when you use a non-stick frying pan or saucepan coated with it. You may have also used it as sealing tape in plumbing. PTFE was invented by accident in 1938 at the American company E. I. du Pont de Nemours and Company, Wilmington, DE, by Roy Plunkett (1910–1994) who was trying to develop a new refrigerant. PTFE was patented in 1941 and in 1945 DuPont registered Teflon as its trademark for this material.

Polyvinyl chloride (IUPAC name: poly(1-chloroethene)), commonly referred to by its abbreviation PVC, sometimes has a poor reputation for its use as a cheap imitation leather, but PVC is invaluable for many applications. PVC, a thermoplastic (it can be melted and set repeatedly) polymer, has a repeat unit similar to that of polyethylene except that a chlorine atom replaces one of the hydrogen atoms. PVC is one of the earliest synthetic materials that man has produced.

The word magnet landed in English via the Latin magnes, which is derived from the Greek magnēs lithos meaning a stone (lodestone) from Magnesia, a Greek city. Permanent magnets in the form of lodestone, a naturally-occurring weak magnet, were known to the Ancient Chinese, Romans, Greeks and, presumably, to other ancient societies. Lodestone consists mainly of ferrimagnetic magnetite (Fe₃O₄) with inclusions of ferromagnetic maghemite (γ-Fe₂O₃) that have been magnetized: interestingly, not all naturally-occurring magnetite has been magnetized. Although the magnetized lodestone could be shown to attract iron, Ancient Peoples made no practical use of these permanent magnets. The first practical use of a permanent magnet had to wait until eleventh century China (the Song dynasty) when a mariner’s compass was developed that used a magnetized iron needle. The best current permanent magnets are the so-called Rare Earth Magnets.

Rayon was the first man-made fiber. However, it is not considered a synthetic fiber since it is made from regenerated cellulose, which is mostly derived from very high-cellulose wood pulp from softwoods. Although there are a number of steps to the manufacturing process, in essence the cellulose is converted to liquid form squeezed through small holes in a spinnerette and then converted back into cellulose fibers.

As anyone who has stretched an elastic or rubber band knows the behavior of rubber is quite different to that of most other materials. If you pull on a crystalline material such as steel it can be stretched only about 0.1–0.2% before it remains permanently stretched: pull it less than 0.2% and the material will spring back to its original length (although this is such a small a change that you would be hard pressed to notice it). Rubber, sometimes called India Rubber, behaves very differently. It can be stretched over 500% and still behave elastically, that is it will spring back to its original length.

Until recently, silicon was a material that we all used in various electronic devices but rarely saw. However, the increasing deployment of photovoltaic solar panels means that we now often see silicon either in polycrystalline, monocrystalline or amorphous (non-crystalline) forms. In fact, the use of elemental silicon in solar cells has been growing so rapidly in recent years that more silicon is now used in solar cells than in electronic devices. Still, most silicon (80%) is not used in elemental form but as an alloying element in various metals principally iron (ferro-silicon) and aluminum (aluminum-silicon) and in making silicones, which are silicon-oxygen polymers. Silicon is also present as an oxide or silicate in ceramics, glasses and various building materials.

Few probably remember “Silver Thursday”, March 27th, 1980 when the collapse in the price of silver produced panic on the futures and commodity exchanges. In 1979–1980, the American oil billionaire brothers Nelson Bunker Hunt (1926–2014) and William Herbert Hunt (1929-) attempted to corner the silver market and it is estimated eventually held $10 billion worth of silver (195 million troy ounces). This amounted to one third of the World silver supply, and led to a price increase from January 1st, 1979 of $6.08 per troy ounce to $49.94 per troy ounce a little over a year later on January 18th, 1980. The Hunt brothers borrowed heavily to purchase the silver and when the New York Commodity Exchange, Inc. (COMEX) placed restrictions on purchasing on margin, they were caught in a classic margin call debacle. Within 2 months of its high point, the price of silver had dropped to less than $11 per troy ounce. The brothers, lost over $1 billion.

There are numerous types of steels and so it is useful to start with a definition of steel. In fact, for simplicity rather than defining steel, let’s start by defining plain carbon steel. A plain carbon steel is an alloy of iron and carbon with 0.05–2.1 weight percent (wt. %) carbon. Historically, iron-carbon alloys with very low levels of carbon (less than about 0.08 wt. %), and often containing some slag from the melting process, have been called wrought iron. Conversely, iron carbon alloys with large carbon contents of 1.8–4 wt.% carbon are called cast irons. The monikers wrought and cast result from the method of processing. Iron has a body centered cubic (b.c.c.) crystal structure at room temperature, which is referred to as ferrite. Carbon atoms are virtually insoluble in b.c.c. iron, because the carbon atom is too big to easily fit into the holes or interstices in the carbon unit cell. Thus, the carbon that can’t dissolve in the b.c.c. iron forms a carbide precipitate, Fe₃C, called cementite, which has a complex orthorhombic crystal structure.

To quote from the 1949 book “Stainless steels: an elementary text for consumers” by Carl Andrew Zapffe (1912–1994) “‘Stainless steel’ is not an alloy - it is the name inherited by a great group of alloys, a special classification of special steels, and a field of study in itself.” The key difference between stainless steels and other steels is that the former has a few nanometer layer of chromium oxide on the surface while the later form iron oxides. The chromium oxide is adherent and protective against further oxidation and corrosion by many chemicals, but not against chloride attack, whereas iron oxide, which we call rust, is not protective. At least 11% chromium is needed to confer corrosion resistance and produce a stainless steel. The corrosion resistance is enhanced by the addition of some other alloying elements, such as nickel and molybdenum.

The Stone Age was the long epoch in human history that ended around the fifth millennium B.C. with the smelting of metals in the Fertile Crescent, and elsewhere somewhat later. We can date the start of the Stone Age to around 3.3 million years ago, the date of the oldest known stone tools found in Kenya. Oddly, these particular tools appear to predate any evidence of humans. This suggests either that humans weren’t the first to use stone tools or that humans existed before the oldest evidence of their existence that has been found to date. The oldest stone tools that were clearly used by humans date to 2.6 million years ago, and were found in Ethiopia. Stone tools were made from a variety of materials including a number of silica-based rocks and minerals such as the sedimentary rocks chert or flint and radiolarite; the mineral chalcedony; basalt; and metamorphic quartzite.

Historically, the most important use of tin was to alloy it with copper to produce bronze. Tin is easily melted since it has a melting point of only 232 °C. Bronze was used as early as 3500 B.C. in present-day Turkey and ushered in a new age. However, neither copper nor tin are very abundant in the Earth’s crust at 0.0068% and 0.00022%, respectively, and they are rarely found together. In the Ancient Western World, principally south-west England, in what would become the county of Cornwall, was a prime source of tin as early as 2150 B.C. and mining continued there until 1998 – tin was also found in northern Spain and Brittany, France. As tin sources in the Middle East were exhausted, Cornish tin became an important source. Tin is easily extracted from its principal ore, Cassiterite, which is tin oxide, by heating with carbon.

Titanium can be considered a god among metals. Like the Titans of Greek mythology, deities of incredible strength, alloys made of titanium are extremely durable and can be very strong. Thus, in 1795 the Austrian chemist Martin Klaproth (1743–1817) named the metal after these deities. Like most pure metals, the pure silvery gray pure metal is relatively soft, but titanium alloys such as Ti-3%Al-8%V-6%Cr-4%Zr-4%Mo can be very strong (yield strength of 1100 MPa) and because of the relatively low density of titanium (4500 kg/m3), they have a much better specific strength (strength/density) than many steels. Titanium and its alloys are also resistant to oxidation and corrosion. Perversely, the resistance to degradation arises because titanium is very reactive and rapidly forms adherent titanium dioxide, TiO₂, which prevents further environmental attack on the underlying metal.

Tungsten, a lustrous silvery-white metal, is one of the so-called refractory metals that includes tantalum, molybdenum, niobium and rhenium that all melt above 2475 °C – tungsten has the highest melting point amongst metals at 3422 °C. The refractory metals are hard and relatively chemically inert, but unfortunately generally have poor oxidation resistance. Tungsten’s crust abundance is only 0.00011%. Tungsten, was discovered by the Spanish chemist brothers, Fausto de Elhuyar (1755–1833) and Juan José Elhuyar Lubize (1754–1796) in 1783. Apart from in French and English, tungsten is called Wolfram in most European languages, hence its Periodic Table symbol is W. The name comes from “tung sten” the Swedish for “heavy stone”, which arises because it is one of the densest metals at 19,300 kg.m−3. Tungsten is one of only seven elements with densities over 17,000 kg.m−3 and the only element that is of practical use in most density-driven applications.

Uranium, a silvery white metal, was isolated in 1841 by French chemist Eugène-Melchior Péligot (1811–1890) and named after the planet Uranus. Later, in 1896 French physicist Antoine Henri Becquerel (1852–1908) , showed that uranium salts and uranium were radioactive and, hence, discovered radioactivity for which he received the Nobel prize in 1903 sharing it with the French husband and wife team Marie Skłodowska-Curie (1867–1934) and Pierre Curie (1859–1906) who also made huge contributions to the study of radioactivity., There are three naturally occurring isotopes of uranium (uranium has eight isotopes in all): uranium-238, uranium-235, and uranium-234, which have half-lives of 4.6 billion years, 700 million years and 25 million years, respectively. The long half-life of uranium-238, which is close to the age of the Earth, means that it is by far the most abundant isotope (99.27% of any natural uranium).

Along with stone, wood is the oldest material utilized by man. Originally it was indubitably used for fuel, for weapons and in construction of buildings and bridges. It was even used for keys by the Ancient Egyptians 4000 years ago. Wood can be considered both to be a natural cellular composite material and a hierarchical structure constituted from micro-fibrils of several organic polymers: cells made of cellulose (~40–50%), a polymer consisting of 5000–10,000 mers or repeat units run along the trunk or branch held together in a matrix of hemicellulose (which constitutes from ~20% in deciduous trees to ~30% in conifers) and lignin (which constitutes from ~23% in deciduous tress to ~27% in conifers). The lignin is a complex polymer that provides rigidity to the wood and also does not easily decompose.

Sheep have both hair, referred to as kemp, and wool and the wild sheep first domesticated had more hair than wool, a feature that selective breeding has inverted. The first evidence of such selective breeding is from Iran around 6000 B.C. with the earliest wool clothing dating from to 3000–4000 B.C.Wool has a protective coating composed of hygroscopic protein (keratin) fibers created in the sheep’s skin. The fibers themselves are dead. Wool is distinguished from fur in that it grows in clusters or staples. Also, unlike fur, which grows to a fixed length and stops growing, wool grows continuously. This continuous growth is a trait shared with the hair on sheep. In fact, some sheep, typically those bred in warmer climates, grow more hair than wool. Hair, is also a protein fiber composed largely of keratin.

You have most likely encountered zinc as a dietary supplement. Even though the pill container may say “Zinc”, it isn’t zinc metal, it’s likely zinc gluconate, zinc acetate or zinc oxide. This medicinal use of zinc accounts for little of the actual use of zinc. Zinc is a hexagonal-close-packed (h.c.p.), bluish-white metal that is relatively hard, and has low ductility. It is reactive and tarnishes in air forming a corrosion-resistant oxide. Zinc is the fourth most commonly-used metal after iron, aluminum and copper even though it is only the 24th most common element at 0.0078% of the Earth’s crust. It is typically found in ores containing lead and copper with the most common ore being mined as a form of zinc sulfide called Sphalerite. Thirty-eight percent of the 2016 World mining production of 12 million tonnes was extracted in China with the next largest producer, Peru, generating less than 30% of China’s production.