Diamond
Scientists have made a diamond that’s harder than diamond.
Nature’s toughest material just got upgraded.
When most people think about the hardest naturally occurring material on Earth, they think of diamonds – those pretty stones in our engagement rings that can cut steel and rock.
But scientists have been gradually improving on that toughness over the past few years, and now a team of Australian researchers has just created a rare type of diamond that’s even harder than diamond.
This diamond is a version of Lonsdaleite, which has been found occurring naturally at the centre of a handful of meteorite impact sites around the world.
It’s special because most diamonds are made up of carbon in a cubic lattice, but Lonsdaleite has a hexagonal lattice, which makes it up to 58 percent harder than regular diamond.
Now researchers have been able to make a nano-scale version of Lonsdaleite in the lab, and they predict that it’s even harder than the naturally occurring version.
It’s so strong, in fact, that the team suggests its most immediate use will be in mine sites, where it can cut through ultra-solid materials, including regular diamonds.
“The hexagonal structure of this diamond’s atoms makes it much harder than regular diamonds, which have a cubic structure,” said lead researcher Jodie Bradby from the Australian National University.
“We’ve been able to make it at the nanoscale and this is exciting because often with these materials ‘smaller is stronger’.”
The team was able to create the new material by nanoengineering the diamond from scratch using a type of carbon that doesn’t have a set form, known as amorphous carbon.
Lonsdaleite was first discovered in the Canyon Diablo meteorite site back in 1967, and researchers have managed to make it in the lab before, but without great success. And it takes incredible temperatures of around 1,000 degrees Celsius (1,832 degrees Fahrenheit) to actually form the diamond.
Instead, Bradby and her team took a different approach.
They put this carbon into a device called a diamond anvil, which is made of two diamonds opposing each other to recreate the high pressures you’d find deep down inside Earth.
You can check it out in the video. URL:https://youtu.be/imysF6z9HEk
Using the device, they were able to create the diamonds at temperatures of just 400 degrees Celsius (752 degrees Fahrenheit) – around half as hot as previous methods, which means it’s a lot cheaper and more efficient. And the end result is also a lot harder.
The researchers now need to go through further testing of this structure to find out exactly how tough it is compared to existing materials, but if natural Lonsdaleite is anything to go off, they’re expecting it to be pretty hard.
“This new diamond is not going to be on any engagement rings. You’ll more likely find it on a mining site,” said Bradby.
“Any time you need a super-hard material to cut something, this new diamond has the potential to do it more easily and more quickly.”
Nanodiamond production in ambient conditions opens door for flexible electronics, implants and more.
Instead of having to use tons of crushing force and volcanic heat to forge diamonds, researchers at Case Western Reserve University have developed a way to cheaply make nanodiamonds on a lab bench at atmospheric pressure and near room temperature.
The nanodiamonds are formed directly from a gas and require no surface to grow on.
The discovery holds promise for many uses in technology and industry, such as coating plastics with ultrafine diamond powder and making flexible electronics, implants, drug-delivery devices and more products that take advantage of diamond’s exceptional properties.
Their investigation is published today in the scientific journal Nature Communications. The findings build on a tradition of diamond research at Case Western Reserve.
Beyond its applications, the discovery may offer some insight into our universe: an explanation of how nanodiamonds seen in space and found in meteorites may be formed.
“This is not a complex process: ethanol vapor at room temperature and pressure is converted to diamond,” said Mohan Sankaran, associate professor of chemical engineering at Case Western Reserve and leader of the project. “We flow the gas through a plasma, add hydrogen and out come diamond nanoparticles. We can put this together and make them in almost any lab.”
The process for making these small “forever stones” won’t melt plastic so it is well suited for certain high-tech applications. Diamond, renowned for being hard, has excellent optical properties and the highest velocity of sound and thermal conductivity of any material.
Unlike the other form of carbon, graphite, diamond is a semiconductor, similar to silicon, which is the dominant material in the electronics industry, and gallium arsenide, which is used in lasers and other optical devices.
While the process is simple, finding the right concentrations and flows—what the researchers call the “sweet spot”—took time.
The other researchers involved were postdoctoral researcher Ajay Kumar, PhD student Pin Ann Lin, and undergraduate student Albert Xue, of Case Western Reserve; and physics professor Yoke Khin Yap and graduate student Boyi Hao, of Michigan Technical University.
Sankaran and John Angus, professor emeritus of chemical engineering, came up with the idea of growing nanodiamonds with no heat or pressure about eight years ago. Angus’ research in the 1960s and 1970s led him and others to devise a way to grow diamond films at low pressure and high temperature, a process known as chemical vapor deposition that is now used to make coatings on computer disks and razor blades. Sankaran’s specialty, meanwhile, is making nanoparticles using cool microplasmas.
It usually requires high pressures and high temperatures to convert graphite to diamond or a combination of hydrogen gas and a heated substrate to grow diamond rather than graphite.
“But at the nanoscale, surface energy makes diamond more stable than graphite,” Sankaran explained. “We thought if we could nucleate carbon clusters in the gas phase that were less than 5 nanometers, they would be diamond instead of graphite even at normal pressure and temperature.”
After several ups and downs with the effort, the process came together when Kumar joined Sankaran’s lab. The engineers produced diamond much like they’d produce carbon soot.
They first create a plasma, which is a state of matter similar to a gas but a portion is becoming charged, or ionized. A spark is an example of a plasma, but it’s hot and uncontrollable.
To get to cooler and safer temperatures, they ionized argon gas as it was pumped out of a tube a hair-width in diameter, creating a microplasma. They pumped ethanol—the source of carbon—through the microplasma, where, similar to burning a fuel, carbon breaks free from other molecules in the gas, and yields particles of 2 to 3 nanometers, small enough that they turn into diamond.
In less than a microsecond, they add hydrogen. The element removes carbon that hasn’t turned to diamond while simultaneously stabilizing the diamond particle surface.
The diamond formed is not the large perfect crystals used to make jewelry, but is a powder of diamond particles. Sankaran and Kumar are now consistently making high-quality diamonds averaging 2 nanometers in diameter.
The researchers spent about a year of testing to verify they were producing diamonds and that the process could be replicated, Kumar said. The team did different tests themselves and brought in Yap’s lab to analyze the nanoparticles by Raman spectroscopy.
Currently, nanodiamonds are made by detonating an explosive in a reactor vessel to provide heat and pressure. The diamond particles must then be removed and purified from contaminating elements massed around them. The process is quick and cheap but the nanodiamonds aggregate and are of varying size and purity.
The new research offers promising implications. Nanodiamonds, for instance, are being tested to carry drugs to tumors. Because diamond is not recognized as an invader by the immune system, it does not evoke resistance, the main reason why chemotherapy fails.
Sankaran said his nanodiamonds may offer an alternative to diamonds made by detonation methods because they are purer and smaller.
The group’s process produces three kinds of diamonds: about half are cubic, the same structure as gem diamonds, a small percentage are a form suspected of having hydrogen trapped inside and about half are lonsdaleite, a hexagonal form found in interstellar dust but rarely found on Earth.
A recent paper in the journal Physical Review Letters suggests that when interstellar dust collides, such high pressure is involved that the graphitic carbon turns into londsdaleite nanodiamonds.
Sankaran and Kumar contend that an alternative with no high pressure requirement, such as their method, should be considered, too.
“Maybe we’re making diamond in the way diamond is sometimes made in outer space,” Sankaran proposed. “Ethanol and plasmas exist in outer space, and our nanodiamonds are similar in size and structure to those found in space.”
The group is now investigating whether it can fine-tune the process to control which form of diamond is made, analyzing the structures and determining if each has different properties. Lonsdaleite, for instance, is harder than cubic diamond.
The researchers have made a kind of nanodiamond spray paint. “We can do this in a single step, by spraying the nanodiamonds as they are produced out of the plasma and purified with hydrogen, to coat a surface,” Kumar said.
And they are working on scaling up the process for industrial use.
“Will they be able to scale up? That’s always a crap shoot,” Angus said. “But I think it can be done, and at very high rates and cheaply. Ultimately, it may take some years to get there, but there is no theoretical reason it can’t be done.”
If the scaled-up process is as simple and cheap as the lab process, industry will find many applications for the product, Sankaran said.
Nanodiamond thermometer can find the temperature inside a single living cell.
The mercury-in-glass thermometer has served us well for the past 270 years, but sometimes you need something smaller — say to find the temperature inside a single living cell. Researchers at Harvard have discovered a new technique using lasers and diamond nanocrystals to measure temperatures of microscopic structures, recording temperature fluctuations as small as 0.05 Kelvin (0.09ºF) in size.
The technique relies on the quantum properties of the diamonds’ tasty centers. In a diamond crystals with a nitrogen vacancy in its center — a kind of defect — the center’s electronic spin comes to depend on its temperature. Laser light bouncing out of one of these nanodiamonds shows up as a different color depending on the center’s temperature. And using diamonds also adds some other benefits. Because they’re highly chemically inert, changes in the surrounding chemistry don’t affect the outcome, and the method can be used over a broad range of temperatures, for the same reason. In one series of experiments (pictured above), the team implanted a human cell with a gold nanoparticle, used a laser to heat it up (thereby heating up the surrounding cell), and bounced a laser off a diamond implanted in the same cell to record the temperature difference. The results will be published in the August issue of Nature.
So why would you want to know the temperature inside a living cell? The team believes that the gold heating trick, precisely monitored with its diamond-and-laser nanothermometer, could make it possible to “engineer biological processes at the subcellular level,” possibly helping to screen for cancer, or cooking the perfect steak, one cell at a time.
Source: http://www.theverge.com
ARYAN'S BLOG 