Science/Materials

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This article lists and discusses various important materials from an engineering standpoint.

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STP Gases

Substances which are gases at STP.

Hydrogen

The least dense gas, and the most common element in the universe, being the primary constituent of stars and gas giants, though uncommon on terrestrial planets (at least after the first few million years). It has a very high heat capacity (ie, it takes a lot of energy to raise its temperature), and also is a very good source of energy.

Hydrogen compressed at 700 bar (seven hundred times atmospheric pressure) has an energy density of 123MJ/kg, whereas petrol (gasoline, to you foreigners) has only 47.2MJ/kg and alkaline batteries have only 0.59MJ/kg. Burning it with oxygen is a highly exothermic reaction and the only waste product is water. The trouble is getting and storing the hydrogen, though enormous greenhouses full of bioreactors containing algae that have been genetically engineered to produce more hydrogen might offer a solution to Earth's energy crisis.

It is one of the two atoms found in water.

Helium

Helium is the least reactive element, and the one with the lowest melting and boiling points (boiling at 4.22K). It is very important in cryogenics, particularly to cool superconducting magnets, and its single largest use is in MRI scanners. Room-temperature superconductors may be discovered in the near future, but until then, all superconductors must be kept at very low temperatures to do their job.

It is rare on Earth, but is the second-most common element in the universe. It can be found in natural gas fields.

Nitrogen

An unreactive gas. This makes up around 78% of the Earth's atmosphere, and much of Titan's and Mars'. It is important for many reasons, particularly the production of nitrates for fertiliser (and propellants/explosives!), as well as to produce ammonia, nitric acid, and cyanides. It is important in living organisms as a major part of amino acids.

Its unreactivity makes it hard to fix, but some bacteria can do it and the Haber process is the industrial method.

Oxygen

The third most abundant element in the universe, and the main constituent of the Earth's crust (being part of most minerals). It forms around 21% of the Earth's atmosphere, but must be continually replenished by oxygenic photosynthesisers, as it tends to react with things. It allows complex life (the worm from the Med wouldn't have been able to evolve without oxygen-breathing ancestors) as aerobic respiration produces around ten times more ATP than anaerobic respiration does. It also causes the generation of an ozone layer that stops much of the harmful UV radiation from the Sun.

It oxidises a very wide variety of things, and combustion requires the presence of oxygen. It is also used in very many industrial processes, including the smelting of iron ore and the production of most polymers. Many rockets use liquid oxygen as the oxidiser for their propellant.

It can be toxic at high partial pressures (the partial pressure of an atmosphere at one bar with 100% oxygen is the same as an atmosphere of two bars with 50% oxygen) around 50% at sea-level pressure on Earth. It is a hazard because it can make things burn or explode.

Fluorine

An extremely reactive light element, and the first halogen. It is far more common in planetary crusts than stars, mainly used in producing hydrofluoric acid and fluorides for industry (elemental fluorine is also used in uranium enrichment). Compounds containing fluorine are usually very stable, such as the freon gases. Fluoride ions help prevent tooth decay, but some people think that the problems of fluoride in water are greater than the benefits. CFCs contain fluorine, but it is the chlorine rather than the fluorine that damages the ozone layer.

Wood and water burn, with flames, when subjected to a jet of fluorine (no spark required). Hydrogen and fluorine react explosively, and the noble metals are the hardest to get to react with fluorine.

Argon

A noble gas. Argon makes up around 0.93% of the Earth's atmosphere, and is very unreactive. Incandescent light bulbs contain an argon atmosphere to preserve the filaments, and it is used as a shielding gas in welding and other high-temperature industrial processes. It is used in preservating foodstuffs and in dark matter detectors.

More sinister is its use for mass culling in the poultry industry after disease outbreaks or for slaughter.

Chlorine

This is the halogen below fluorine in the periodic table, less reactive but still nasty stuff. It boils at 239K, so is a gas at room temperature. It is, with sodium, one of the constituents of table salt, and is vital for life.

It is used to produce bleach and hydrochloric acid, as well as PVC and chlorinating swimming pools. It was used as a weapon in WW1, as it reacts with the lining of the lungs and can be lethal. Chlorine bombings were also carried out by insurgents in the Iraq War. Also, chlorine radicals (from CFCs) break down the ozone layer.

Carbon dioxide

CO2. In photosynthesis, CO2 is taken in by plants and used to produce carbohydrates, as part of the carbon cycle. It is produced by the combustion of molecules containing carbon, by respiration, and by volcanic activity. It is a strong greenhouse gas and a major player in ocean acidification.

This gas sublimates (at -78.5 degrees C), so goes straight from a solid to a gas without a liquid phase. The solid is called 'dry ice', and can cause frostbite if touched. It is used in food preservation, industry, as a solvent, in 'dry ice bombs'.

Metals

Metallic substances.

Lithium

The third element in the periodic table. Lithium is a reactive alkali metal, tarnishing in air and reacting with water to produce a flame. It is not very dense (0.534g/cm^3), but has a very high heat capacity and is probably the best metal for heat sinks. It can be extracted from seawater, but usually from clays.

Lithium is used to make heat-resistant ceramics and glass, as well as aircraft alloys, lithium-ion batteries, lithium-polymer batteries and in fusion fuel for thermonuclear bombs (as lithium deuteride).

Aluminium

This is the third most abundant element in the Earth's crust, after oxygen and silicon, at about 8%. It is very reactive, but this works to its advantage because it produces a layer of unreactive, corrosion-resistant aluminium oxide over its surface when exposed to oxygen. It has low density (2.698g/cm^3) but high strength. It is used in a wide variety of applications, including in vehicles, packaging, construction, paint, mirrors, and pyrotechnics. Its melting point is quite low.

Because of its reactivity, it is hard to extract aluminium. It is usually extracted electrolytically, which accounts for a large proportion of an industrial nation's electricity usage. This is why it is better to recycle aluminium than extract more, despite its abundance.

Titanium

Titanium, when exposed to air, produces hard and corrosion-resistant layers of titanium nitride and dioxide over its surface. It has high strength and low density (4.54g/cm^3) Highly pure grades of titanium have similar strength to low-grade steels, while being around 45% lighter, and is more than twice as strong as most aluminium alloys while being only 60% denser. It loses strength at temperatures in excess of 430 degrees C, however. It is a poor conductor of heat and electricity.

Ti is the ninth most abundant element in the crust. It is non-toxic and used in hip replacements and piercings. Titanium nitride is as hard as sapphire, and used in drill bits and cutting tools.

Iron

The most common element in the Earth as a whole, iron also makes up around 5% of the crust. This is due to its production in stellar fusion. The production of iron (via Ni-56) is the last fusion reaction which yields energy, rather than requiring it. Pure iron is quite soft, but unreactive, magnetic, and resistant to high temperatures. It is usually used to make steels, which can have a strength of 1000 times of that of pure iron. Pure iron has a density of 7.874g/cm^3.

It is produced in blast furnaces from the iron oxide haematite. It is important in biological systems, particularly in haemoglobin and enzymes. Some chemosynthesisers reduce iron. Too much iron is toxic, which is why vampire bats have a specialised digestive tract.

Nickel

Nickel forms the majority of the Earth's core, along with iron, and is common in iron-nickel meteorites. However, it is far less prevalent at the surface. Its density is higher than that of iron, at 8.912g/cm^3. It is corrosion-resistant, and so often used to plate iron, and is used in chemical apparatus. Nickel is ferromagnetic, like iron, and so used to make permanent magnets- however, its main use is in steels. Superalloys often contain nickel.

Some enzymes incorporate nickel. It is usually extracted by roasting its ores.

Silver

Silver is the element with the highest electrical and thermal conductivity. It is quite unreactive, and can be found in its pure form naturally. It is rare, and dense at 10.5g/cm^3.

It is used in utensils, jewelry, electrical contacts, and conductors. It forms some notable compounds, such as those used in photographic film, disinfectants and antibacterial materials. Many of these salts are also toxic.

Caesium

A highly reactive alkali metal, caesium must be stored in an inert atmosphere. It is the softest of all the elements, and melts at 28.4 degrees centigrade. It ignites spontaneously in air and reacts explosively with water, even at -116 degrees centigrade. It is classed as a hazardous material.

Hafnium

A dense (13.31g/cm^3) and lustrous metal, hafnium is mainly used in its oxide as part of integrated circuits for semiconductors. It is also used in some superalloys. It is good at absorbing neutrons, and so is part of many types of nuclear control rod. It is corrosion-resistant due to the formation of a layer of hafnium dioxide on its surface, and resistant to most acids, but vulnerable to halogens. Fine hafnium can ignite spontaneously in air.

Theoretically, rapid energy releases (as gamma rays) were possible from one nuclear isomer of Hafnium- 178m2Hf. Potentially, such a release could be 100,000 times more energetic than chemical reactions, and a third as energetic as nuclear reactions. In 1998, one group reported initiating this kind of activity, but the results could not be replicated, and later studies concluded that the technology to use this mechanism was beyond that humanity possessed.

Tantalum

A corrosion-resistant, hard, and dense (16.654 g/cm^3) metal, tantalum has a very high melting point (3269 degrees K) and is used in laboratory equipment as well as as a replacement for platinum. Tantalum capacitors are the main use for the element. Out of the acids, only hydrofluoric acid and hot sulphuric acid can corrode tantalum.

Tungsten

This is Holbenilord's favourite element. It is the hardest, even when without impurities, and has the highest melting point (3680K) bar carbon. It resists attack by acids, alkalis, and oxygen, being extremely corrosion-resistant. It forms tungsten carbide, which is extremely hard and resistant to corrosion, being used in many power tools. It is relatively uncommon, but many tens of thousands of tonnes are extracted every year, primarily for making tungsten carbide and tungsten steels.

It is extremely dense- more so than lead and similar to gold, at 19.25g/cm^3. With impurities, it is also quite brittle.

Rhenium

Rhenium is one of the rarest elements in the crust, at around only one part per billion. It has the third-highest melting point of the elements, at 3452K, and is very dense indeed, at 21.02g/cm^3 (only platinum, iridum, and osmium are denser). It is mainly used in the high-wear components of jet engines in steels.

Osmium

Osmium is the densest natural element, at 22.59g/cm^3. It has a similar bulk modulus (resistance to uniform compression) to diamond, so is very hard to work. Its melting point is around 3300K.

It is rarely used in its pure state, because it will then react with oxygen to form osmium tetroxide. This is highly volatile, penetrates skin, and is very toxic, causing lung congestion and skin or eye damage. However, it is used in alloys, which are very hard and robust.

Iridium

Hard, brittle, and silvery-white, iridium is the most corrosion-resistant metal, even at two thousand degrees centigrade, and the second densest, at 22.56g/cm^3. Fine iridium dust, however, is irritant and flammable. It is very rare in the Earth's crust, but far more plentiful in meteorites. The presence of a band of iridium-rich materials was evidence for the meteorite theory of the KT extinction.

Around 10.4 tonnes were on demand in 2010. Iridium is produced as a by-product of nickel and copper processing and mining. Iridium is used in certain alloys which must be very durable and resistant to corrosion, and as a hardening agent in platinum alloys.

Platinum

Platinum is the least reactive metal. It is extremely rare, and is found in copper and nickel deposits. It exhibits very good corrosion resistance even at high temperatures. Its density is high, at 21.46g/cm^3. Only a few hundred tonnes of it are produced annually, so it is in very high demand, and its rarity and appearance makes it very valuable in jewelry.

The element is most commonly used for its catalytic properties, for example in a car's catalytic converter. It is also used in electrodes, and in alloys where corrosion resistance is very important. Platinum salts are irritant.

Gold

A very attractive metal, gold is very dense (19.3g/cm^3) and very corrosion-resistant. Its unreactivity means that it often can be found in its pure state, as nuggets or veins. Most gold is used in jewelry, but some is used in industry and electronics. It is a very good conductor. Very good at reflecting EM radiation from radio waves to visible light, and so thin layers are sometimes used to coat satellites and the faceplates of space and thermal protection suits.

Lead

With a density of around 11.3g/cm^3, lead is a soft and very workable metal. It tarnishes in air to become a dull grey. It is far more common than any of its surrounding elements on the periodic table, due to its being the final product of s-process fusion.

Most lead is used in cars, which use lead-acid batteries to generate electricity. It is also used as a radiation shield, which it is very effective as. It is very toxic, primarily effecting the nervous system, and cause brain and kidney damage.

Thorium

A radioactive element, thorium has a density of 11.72g/cm^3 and quite soft. It undergoes a slow reaction with water. It is around four times more abundant than uranium, and thorium-based power stations were a challenger to uranium-based ones. Uranium won out because that process allows the creation of nuclear weapons.

You can read about thorium reactors here.

Uranium

Best known for its radioactive properties, uranium is a silvery-white, hard and dense (18.95g/cm^3) metal. It is highly reactive, and a layer of uranium oxide will form if it is exposed to the air.

7kg of uranium-235 can be used to make an atomic bomb. One kilogram of U-235 could theoretically produce as much energy as 3000 tonnes of coal. Depleted uranium is used in kinetic penetrators, armour plating, and as a radiation shield.

Plutonium

A dense metal, about as hard and brittle as cast iron, with poor conductive properties, plutonium is a very reactive element. It oxidises very quickly to form a dull grey surface layer. It is radioactive and can be induced to undergo nuclear fission.

There are several isotopes of plutonium. The quantity of Pu-240 affects how large the core of a nuclear weapon can be, as it increases the risk of premature detonation. One kilogram of Pu-239 could produce 21 kilotons of TNT equivalent in an explosion. Plutonium is highly toxic, and about as dangerous as nerve gas- one pound of plutonium dust in the atmosphere could kill over two million people by inhalation.

Alloys

Alloys are metallic mixtures comprised of several elements.

Steels

Steels are alloys of iron and other elements, usually mainly carbon. Carbon steels make up the vast majority of steel production, which are made of carbon and iron alone. HSLA steels have other elements added, such as manganese, which provide strength increases.

Stainless steels contain at least 11% chromium, and are highly resistant to corrosion. Tool steels contain tungsten or cobalt to maximise hardness and improve temeprature resistance.

Titanium alloys

Titanium is often alloyed to improve corrosion resistance and to make it withstand higher temperatures. For most applications, titanium is alloyed and around 6% aluminium and 4% vanadium by weight.

Non-Metals

Not metals.

Boron

As it is not produced by stellar nucleosynthesis, boron is not a common element. It forms massive covalent structures, which are black and shiny, and elemental boron has a Mohs hardness of around 9.5, where sapphire/ruby/emeralds are 9 and diamond is 10. It is more dense than carbon, at around 2.34g/cm^3, has a high heat capacity, and has a high melting point- 2573K. However, elemental boron is very difficult to prepare, and expensive. It forms a large number of compounds.

Boron nitrides form compounds similar to those formed by carbon. Cubic boron nitride is similar in structure to diamond, and is one of the hardest known materials. It is used in high-wear, high-stress applications. Borosilicate glass is very strong and thermally resistant.

Boron is also a good neutron absorber, and so is used in nuclear control rods. It is an essential plant nutrient, important for the integrity of their cell walls. Most boron compounds and elemental boron are non-toxic, requiring many grams to cause damage. However, boranes are poisonous and highly flammable.

Carbon

The fourth most abundant element in the universe and the fifteenth most abundant in the crust, carbon is a light and versatile element. Elemental carbon has several allotropes (forms) including diamond, graphite, amorphous carbon, and fullerenes.

Except when under extreme pressure, carbon does not melt- instead, it sublimates straight from solid to gas at 3915 degrees kelvin. It is extremely resistant to corrosion, acids, halogens, and more, reacting with oxygen only at heightened temperatures in the process of combustion.

Allotropes:

Amorphous carbon is similar to graphite, but non-crystalline. Charcoal and soot are this, in an irregular and glassy state. This is used in industry to reduce many metal oxides to pure(ish) metal.

Graphite is formed from layers of carbon atoms, each bonded to three others, with free electrons. It is very soft, electrically conductive, an effective insulator, and a good lubricant. Single layers are called graphene, and graphene is the strongest material ever tested.

Diamond is formed from carbon atoms bonded to four others in a giant lattice. It is one of the hardest materials known, while also being transparent, an electrical insulator, and the best known natural thermal conductor. Diamond has twice the density of graphite, and is only formed in extremes of heat and pressure. It is usually flawed, with fractures and microfractures in its structure- hence why diamonds can be broken using a steel chisel. Synthetic diamonds make up the majority of industrially used diamonds.

Nanodiamond is slightly denser than diamond and is the hardest material produced. It is a series of interconnected diamond nanorods, usually produced by extreme compression of fullerite.

Fullerenes are like graphite, but also have pentagons and heptagons of carbon atoms in addition to hexagons. As such, these molecules can form spheres and cylinders.

Lonsdaleite has a crystal structure like diamond, but is formed from hexagons. It has been found on Earth, impurities making it have a Mohs hardness of around 7.5, but pure lonsdaleite has been predicted to be 58% harder than diamond (on a scratch test).

Carbon is also the basis of organic chemistry, which includes all biological molecules.

Silicon

The element below carbon in the periodic table, silicon is the most common element in the Earth's crust. It is less reactive than carbon, and forms less stable molecules. Elemental silicon has a density of 2.33g/cm^3 and a melting point of 1683K, forming a cubic crystal structure like diamond.

It has a very high affinity for oxygen, and so almost all silicon is found in silicate rocks, which make up around 90% of the Earth's crust. Quartz is a notable form of silicon dioxide, and other silicates include mica and feldspar (which occur in clays and granite, among others).

Silicon is a semiconductor, and useful in the electronics industry when very pure.

Bromine

At room temperature, bromine is a reddish-brown liquid that evaporates easily to produce a brownish vapour. A halogen, it reacts vigorously with most metals, producing bromide salts. The largest use of bromine is in flame retardants, but also as an insecticide and for medical uses (eg. as an anti-convulsant).

Bromine is even more effective at ozone depletion than chlorine. Two million metric tons would destroy the ozone layer completely, resulting in the destruction of all land plants within hours and second-degree burns for anyone outside. This would cost around $52 million, provided the bromine was bought in 2300 gallon tanks.

Notes

Degrees Kelvin = degrees centigrade +273.15, so 0K is absolute zero.

No, you can't make a new element to suit yourself. There's no space between the existing elements and all the ones afterwards decay in a fraction of a second, though they wouldn't be very interesting anyway. You can't reach the island of stability because before that the atom's electrons would have to travel FTL.

And you can't make a new compound either, because we would have already found it.