Home » Scientists use laser flashes to make tiny DIAMONDS out of plastic bottles to help reduce waste

Scientists use laser flashes to make tiny DIAMONDS out of plastic bottles to help reduce waste

by Press room

Diamonds could soon be everyone’s best friend, as scientists have found a way to make the precious gems from used plastic bottles.

Their technology could help limit plastic waste, as the recycled nanodiamonds have a wide array of applications including medical sensors and drug delivery.

Researchers at the SLAC National Accelerator Laboratory in California were intending to recreate the ‘diamond rain’ phenomenon that occurs inside Neptune and Uranus.

Within these ice giants are temperatures of several thousand degrees Celsius, and the pressure is millions of times greater than in the Earth’s atmosphere.

These conditions are thought to be able to split apart hydrocarbon compounds, and then compress the carbon component into diamonds that sink deeper into the planets’ cores.

To mimic this process, the scientists fired a high-powered laser at polyethylene terephthalate (PET) plastic – a hydrocarbon material commonly used in single-use packaging – and witnessed the growth of diamond-like structures.

‘PET has a good balance between carbon, hydrogen and oxygen to simulate the activity in ice planets,’ said Dominik Kraus, a physicist at HZDR and professor at the University of Rostock.

To mimic the ‘diamond rain’ formation that occurs within ice giants, scientists fired a high-powered laser at polyethylene terephthalate (PET) plastic – a hydrocarbon materiel commonly used in single-use packaging – and witnessed the growth diamond-like structures.

Using a method called X-ray diffraction, the scientists watched as the atoms in the PET rearranged into small diamond regions, and also measured how large and quickly they grew. However, with the presence of oxygen in the material, they found the nanodiamonds were able to grow at lower pressures and temperatures than previously observed

Using a method called X-ray diffraction, the scientists watched as the atoms in the PET rearranged into small diamond regions, and also measured how large and quickly they grew. However, with the presence of oxygen in the material, they found the nanodiamonds were able to grow at lower pressures and temperatures than previously observed

HOW DID THE SCIENTISTS CREATE NANODIAMONDS? 

The scientists wanted to discover what effect the presence of oxygen had on the formation of nanodiamonds from hydrocarbon compounds inside Neptune and Uranus.

They used a high-powered optical laser at SLAC’s Linac Coherent Light Source to briefly heat a thin film of PET up to 10,800°F (6,000°C).

This generated a shockwave that compressed the material for a few nanoseconds, to a million times the atmospheric pressure.

Using a method called X-ray diffraction, the scientists watched as the atoms rearranged into small diamond regions, and also measured how large and quickly they grew.

With the presence of oxygen in the material, they found the nanodiamonds were able to grow at lower pressures and temperatures.

It is known that mixtures of compounds made of hydrogen and carbon are present about 5,000 miles beneath the surface of Uranus and Neptune.

This includes methane, a molecule with just one carbon bound to four hydrogen atoms, which causes the distinct blue cast of Neptune.

In a 2017 study, the SLAC team successfully simulated the diamond rain process for the first time by firing their optical laser at polystyrene.

Polystyrene was used to mimic the structure of methane, as it also only contains hydrogen and carbon. 

The intense X-rays produced shockwaves within the material, and the scientists observed carbon atoms being incorporated into small diamond structures up to a few nanometres wide.

‘But inside planets, it’s much more complicated,’ said Siegfried Glenzer, director of the High Energy Density Division at SLAC.

‘There are a lot more chemicals in the mix. And so, what we wanted to figure out here was what sort of effect these additional chemicals have.’

In addition to carbon and hydrogen, ice giants are thought to contain large amounts of oxygen.

The scientists wanted to discover what effect the element has on nanodiamond formation inside Neptune and Uranus.

To do this, they repeated their earlier experiment with a film of PET plastic – a hydrocarbon that also contains oxygen – which more accurately reproduces the composition of the planets.

Within Neptune and Uranus are temperatures of several thousand degrees Celsius, and the pressure is millions of times greater than in the Earth's atmosphere. These conditions are thought to be able to split apart hydrocarbon compounds, and then compress the carbon component into diamonds that sink deeper into the planets' cores. The scientists wanted to discover what effect the oxygen had on nanodiamond formation within the planets

Within Neptune and Uranus are temperatures of several thousand degrees Celsius, and the pressure is millions of times greater than in the Earth’s atmosphere. These conditions are thought to be able to split apart hydrocarbon compounds, and then compress the carbon component into diamonds that sink deeper into the planets’ cores. The scientists wanted to discover what effect the oxygen had on nanodiamond formation within the planets

They used a high-powered optical laser at SLAC’s Linac Coherent Light Source to briefly heat the sample up to 10,800°F (6,000°C).

This generated a shockwave that compressed the material for a few nanoseconds to a million times the atmospheric pressure.

Using a method called X-ray diffraction, the scientists watched as the atoms rearranged into small diamond regions, and also measured how large and quickly they grew.

However, with the presence of oxygen in the material, they found the nanodiamonds were able to grow at lower pressures and temperatures than previously observed. 

‘The effect of the oxygen was to accelerate the splitting of the carbon and hydrogen and thus encourage the formation of nanodiamonds,’ Dr Kraus said. 

‘It meant the carbon atoms could combine more easily and form diamonds.’ 

At the Matter in Extreme Conditions (MEC) instrument at SLAC's Linac Coherent Light Source, researchers recreated the extreme conditions found inside Neptune and Uranus

At the Matter in Extreme Conditions (MEC) instrument at SLAC’s Linac Coherent Light Source, researchers recreated the extreme conditions found inside Neptune and Uranus 

They used a high-powered optical laser at SLAC's Linac Coherent Light Source to briefly heat the sample up to 10,800°F (6,000°C). This generated a shockwave that compressed the material for a few nanoseconds to a million times the atmospheric pressure

They used a high-powered optical laser at SLAC’s Linac Coherent Light Source to briefly heat the sample up to 10,800°F (6,000°C). This generated a shockwave that compressed the material for a few nanoseconds to a million times the atmospheric pressure

The researchers predict that the diamonds inside Neptune and Uranus would actually become much larger than those produced in these experiments – potentially millions of carats in weight.

This could mean that, over thousands of years, these heavier crystals will sink through the planets and assemble a thick layer around the solid planetary core. 

In addition to the diamonds, evidence was found in the experiments that ‘superionic water’ might form within the planets.

This is created when water molecules break apart as a result of the high temperatures and pressures.

The oxygen atoms then form a regular lattice structure, inside which the remaining hydrogen atoms can float around and, as they are charged, can conduct electricity.

The currents this unique phase of water carries could explain the unusual magnetic fields on Uranus and Neptune.

These findings, published today in Science Advances, could impact our understanding of ice giants outside our solar system, which may experience the same phenomena.

As the presence of oxygen makes diamond formation more likely, it is probably also occurring on other planets under their unique internal conditions.

The researchers want to perform similar experiments on samples containing ethanol, water and ammonia – all present on Uranus and Neptune – to get closer to simulating what could be going on inside other planets.

The study has also indicated a way of producing nanodiamonds by creating laser-driven shockwaves in cheap PET plastics

Nanodiamonds are already used in abrasives and polishing agents, but in the future they could also be used for quantum sensors or to accelerate reactions for renewable energy, like splitting carbon dioxide.

‘The way nanodiamonds are currently made is by taking a bunch of carbon or diamond and blowing it up with explosives,’ said SLAC scientist and collaborator Benjamin Ofori-Okai. 

‘This creates nanodiamonds of various sizes and shapes and is hard to control. 

‘What we’re seeing in this experiment is a different reactivity of the same species under high temperature and pressure. 

‘In some cases, the diamonds seem to be forming faster than others, which suggests that the presence of these other chemicals can speed up this process. 

‘Laser production could offer a cleaner and more easily controlled method to produce nanodiamonds. 

‘If we can design ways to change some things about the reactivity, we can change how quickly they form and therefore how big they get.’

HOW ARE DIAMONDS FORMED?  

Naturally occurring diamonds were formed over 3 billion years ago deep within the Earth’s crust under conditions of intense heat and pressure. 

These conditions cause carbon atoms to crytallise, forming diamonds. 

Diamonds are found at a depth of approcimately 150 to 200 kilometres (93 – 124 miles). 

Here, temperatures average 900 to 1,300 degrees Celsius, with pressures of 45 to 60 kilobars (which is around 50,000 times that of atmospheric pressure at the Earth’s surface).

Under these conditions, molten lamproite and kimberlite (known as magma) are also formed within Earth’s upper mantle, and they expand at rapid rates. 

This expansion causes the magma to erupt, forcing it to Earth’s surface and taking along with it diamond bearing rocks.

The magma erupts by forming a ‘pipe’ to the surface, and as it cools the magma hardens to form Kimberlite, settling in vertical structures called kimberlite pipes. 

These pipes are the most significant sources of diamonds, yet only about 1 in every 200 kimberlite pipes contain gem-quality diamonds.

The name ‘Kimberlite’ comes from the South African town of Kimberley, where the first diamonds were found in this type of rock. 

Source: Cape Town Diamond Museum

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