by John Jones
First, the big picture: there are 93 naturally occurring elements; and That’s your lot, says God.
So, the task of material scientists is to make the best of them. Options include tinkering with microscopic structures, or re-arranging the ways in which the atoms of elements combine as “molecules”.
Elements, of course, include metals like iron, tungsten, gold, etc. and non-metals (including gases) such as carbon, phosphorus, chlorine. There are also elements that are half metal, half non-metal, called metalloids. These include boron, selenium and antimony.
Let’s take a look at some of the latest structures and compounds.
Microlattice is one hundred times lighter than styrofoam.
The use of light-sensitive plastics and stencil photography is becoming increasingly important in the construction of electronic parts and novel materials. Here’s one such use.
In 2012, HRL laboratories and California University made an extremely light, flexible material that they named “microlattice”. Microlattice is a nickel lattice only 1.7 times as heavy as air.
A two inch cube of Microlattice is light enough to sit on a dandelion seed-head, and falls slowly when dropped. Popular Mechanics magazine dubbed it one of 10 world-changing innovations.
Here’s how it is made. Light is shone through a moving stencil of tiny holes into a plastic that solidifies when illuminated. This procedure creates a lattice of plastic rods.
The unhardened plastic is washed out and the remaining plastic lattice dipped in a nickel salt solution. Hypo-phosphite solution is then added which deposits nickel on the plastic lattice. The plastic is dissolved out and we are left with a nickel metal lattice. Microlattice can be used for insulation, shock absorbers, and catalyst supports for exhausts, etc.
Wonder substance you can make in the kitchen
Material scientists have not finished tinkering with the molecular forms of carbon, though one, graphene, can be made by blending pencil leads. Graphene consists of single sheets of hexagonal-crystal carbon or graphene. The trick, though, is to isolate the single sheets of graphene. Graphene is excellent at repelling water and contaminants.
Also made of carbon is aerographite. Bizarrely, objects painted with aerographite are so black they seem to lose their features.
These compounds can be made into super-light, bouncy materials by vapour deposition onto sponge or evaporation and sintering of an aerographite/graphene gel-impregnated plastic sponge. They can be used in the construction of very light batteries for electric cars and bikes, for air and water filtration, or in satellite and aviation engineering.
Also tinkering with the small scale, and more immediately useful is Ductal. Ductal is concrete with added metal or plastic fibres. It is 7 times stronger than concrete, denser, and more flexible. This makes it resistant to corrosion and cracking – properties useful for under-water bridge supports and earthquake-resistant buildings.
Substance harder than diamond created by meteorites
Lonsdaleite is harder than diamond and is found in meteor impact zones. The enormous temperatures and pressures crush amorphous carbon or graphite present in the meteor into a special ultra-hard hexagonal form. Diamond is carbon in its cubic form and is also formed at high pressures.
Boron nitride is similar in crystal structure to diamond and made, funnily enough, of boron (B) – a metalloid, and nitrogen (N). In its special hexagonal form BN is also harder than diamond, and exists in minute quantities in nature.
Scientists have been able to synthesise both these compounds by a variety of methods such as vapour deposition from high temperature carbon plasma-gas.
A New Chemistry! (what? you ‘avin a laugh?)
New chemicals, yes. A “new chemistry”? – no way! But take a gander at “high-pressure chemistry” – it will surprise even the chemists among us.
Researchers from Stony Brook University have managed to change the formula of salt. You know, the stuff you put on your chips, sodium chloride or NaCl. They say they have made
“…crazy compounds that violate text-book rules, NaCl3, NaCl7, Na3Cll2…” The researchers point out that these are chemicals, and not just a material composite of sodium and chlorine.
Here’s the background. According to chemistry text-books, elements, like sodium (Na) and chlorine (Cl), have “valencies”. Valencies are like electro-statically gluey arms. Both sodium and chlorine have one valency which is why the formula of salt is NaCl – one atom of each.
But (and you won’t find this in standard text-books) under high pressure (200,000 atmospheres) this chemistry can change. Sodium can combine with 3 chlorines for example (NaCl3), or vice versa. Another compound, Na3Cl, conducts electricity through a sandwiched sodium-rich layer.
I cannot imagine where high-pressure chemistry will take us. The electronics industry have expressed a keen interest, and at least some of the reported compounds appear relatively stable at room temperature.
However, I am sure that stability of these new compounds will be a problem; but then that may be an asset. As with all these innovations, and there are many that I have not mentioned, the public must wait and see what eventually turns up.
Enjoyed this article?
Get the whole PDF newspaper to your inbox. 26 issues for £6.50