Scientists at the Department of Energy's Oak Ridge National Laboratory have invented a coating that could dramatically reduce friction in common load-bearing systems with moving parts, from vehicle drive trains to wind and hydroelectric turbines. It reduces the friction of steel rubbing on steel at least a hundredfold. The novel ORNL coating could help grease a U.S. economy that each year loses more than $1 trillion to friction and wear—equivalent to 5% of the gross national product.
"When components are sliding past each other, there's friction and wear," said Jun Qu, leader of ORNL's Surface Engineering and Tribology group. Tribology, from the Greek word for rubbing, is the science and technology of interacting surfaces in relative motion, such as gears and bearings. "If we reduce friction, we can reduce energy consumption. If we reduce wear, we can elongate the lifespan of the system for better durability and reliability."
With ORNL colleagues Chanaka Kumara and Michael Lance, Qu led a study published inMaterials Today Nanoabout a coating composed ofcarbonnanotubes that imparts superlubricity to sliding parts. Superlubricity is the property of showing virtually no resistance to sliding; its hallmark is a coefficient of friction less than 0.01. In comparison, when dry metals slide past each other, the coefficient of friction is around 0.5. With an oil lubricant, the coefficient of friction falls to about 0.1. However, the ORNL coating reduced the coefficient of friction far below the cutoff for superlubricity, to as low as 0.001.
"Our main achievement is we make superlubricity feasible for the most common applications," Qu said. "Before, you'd only see it in either nanoscale or specialty environments."
For the study, Kumara grew carbon nanotubes on steel plates. With a machine called a tribometer, he and Qu made the plates rub against each other to generate carbon-nanotube shavings.
Themultiwalled carbon nanotubescoat the steel, repel corrosive moisture, and function as a lubricant reservoir. When they are first deposited, the vertically aligned carbon nanotubes stand on the surface like blades of grass. When steel parts slide past each other, they essentially "cut the grass." Each blade is hollow but made of multiple layers of rolledgraphene, an atomically thin sheet of carbon arranged in adjacent hexagons like chicken wire. The fracturedcarbon nanotubedebris from the shaving is redeposited onto the contact surface, forming a graphene-rich tribofilm that reduces friction to nearly zero.
Making the carbon nanotubes is a multistep process. "First, we need to activate the steel surface to produce tiny structures, on the size scale of nanometers. Second, we need to provide acarbon sourceto grow the carbon nanotubes," Kumara said. He heated a stainless-steel disk to form metal-oxide particles on the surface. Then he usedchemical vapor depositionto introduce carbon in the form of ethanol so that metal-oxide particles can stitch carbon there, atom by atom in the form of nanotubes.
The new nanotubes do not provide superlubricity until they are damaged. "The carbon nanotubes are destroyed in the rubbing but become a new thing," Qu said. "The key part is those fractured carbon nanotubes are pieces of graphene. Those graphene pieces are smeared and connected to the contact area, becoming what we call tribofilm, a coating formed during the process. Then both contact surfaces are covered by some graphene-rich coating. Now, when they rub each other, it's graphene on graphene."
The presence of even one drop of oil is crucial to achieving superlubricity. "We tried it without oil; it didn't work," Qu said. "The reason is, without oil, friction removes the carbon nanotubes too aggressively. Then the tribofilm cannot form nicely or survive long. It's like an engine without oil. It smokes in a few minutes, whereas one with oil can easily run for years."
The ORNL coating's superior slipperiness has staying power. Superlubricity persisted in tests of more than 500,000 rubbing cycles. Kumara tested the performances for continuous sliding over three hours, then one day and later 12 days. "We still got superlubricity," he said. "It's stable."
Usingelectron microscopy, Kumara examined the mowed fragments to prove that tribological wear had severed the carbon nanotubes. To independently confirm that rubbing had shortened the nanotubes, ORNL co-author Lance used Raman spectroscopy, a technique that measures vibrational energy, which is related to the atomic bonding and crystal structure of a material.
"Tribology is a very old field, but modern science and engineering provided a new scientific approach to advance technology in this area," Qu said. "The fundamental understanding has been shallow until the last maybe 20 years, when tribology got a new life. More recently, scientists and engineers really came together to use the more advanced material characterization technologies—that's an ORNL strength. Tribology is very multidisciplinary. No one is an expert in everything. Therefore, in tribology, the key to success is collaboration."
He added, "Somewhere, you can find a scientist with expertise in carbon nanotubes, a scientist with expertise in tribology, a scientist with expertise in materials characterization. But they are isolated. Here at ORNL, we are together."
ORNL's tribology teams have done award-winning work that has attracted industrial partnerships and licensing. In 2014, an ionic anti-wear additive for fuel-efficient engine lubricants, developed by ORNL, General Motors, Shell Global Solutions and Lubrizol, won an R&D 100 award. ORNL's collaborators were Qu, Huimin Luo, Sheng Dai, Peter Blau, Todd Toops, Brian West and Bruce Bunting.
Similarly, the work described in the current paper was a finalist for an R&D 100 award in 2020. The researchers have applied for a patent of their novel superlubricity coating.
"Next, we hope to partner with industry to write a joint proposal to DOE to test, mature and license the technology," Qu said. "In a decade we'd like to see improved high-performance vehicles and power plants with less energy lost to friction and wear."
PhD candidate Jordan Noronha holding a sample of the new titanium lattice structure 3D printed in cube form. [Credit: RMIT]
By Michael Quin, RMIT University
A 3D-printed "metamaterial" boasting levels of strength for weight not normally seen in nature or manufacturing could change how we make everything from medical implants to aircraft or rocket parts.
RMIT University researchers in Melbourne, Australia, created the new metamaterial -- a term used to describe an artificial material with unique properties not observed in nature -- from common titanium alloy.
However, it's the material's unique lattice structure design, recently revealed in theAdvanced Materialsjournal, that makes it anything but common: Tests show it is 50% stronger than the next strongest alloy of similar density used in aerospace applications. Interestingly, the initial lattice shape was inspired by corals.
In their paper, the researchers list potential applications as: "in demanding thermal protection systems such as those for hypersonic vehicles," "titanium drones used to monitor or fight bushfires or severe industrial fires at close range and with extended flight times," or "as implant materials, as well as lightweight structures to replace magnesium alloy components in defense and aerospace (being lighter, stronger, and more heat and corrosion resistant)."
Improving nature's own design Lattice structures made from hollow struts were originally inspired by nature: strong hollow-stemmed plants like the Victoria water lily or the hardy organ pipe coral (Tubipora musica) showed the way in combining lightness and strength.
However, as RMIT's Distinguished Professor Ma Qian explained, decades of trying to replicate these hollow "cellular structures" in metals has been frustrated by the common issues of manufacturability and load stress concentrating on the inside areas of the hollow struts, leading to premature failures.
"Ideally, the stress in all complex cellular materials should be evenly spread," Qian said. "However, for most topologies, it is common for less than half of the material to mainly bear the compressive load, while the larger volume of material is structurally insignificant."
Metal 3D printing provides unprecedented innovative solutions to these issues.
By pushing 3D printing design to its limits, the RMIT team optimized a new type of lattice structure to distribute the stress more evenly, enhancing its strength or structural efficiency.
"We designed a hollow tubular lattice structure that has a thin band running inside it. These two elements together show strength and lightness never before seen together in nature," said Qian. "By effectively merging two complementary lattice structures to evenly distribute stress, we avoid the weak points where stress normally concentrates."
Compression testing shows (left) stress concentrations in red and yellow on the hollow strut lattice, while (right) the double lattice structure spreads stress more evenly to avoid hot spots. [Credit: RMIT]
Laser-powered strength They 3D printed this design at RMIT's Advanced Manufacturing Precinct using a process called laser powder bed fusion, where layers of metal powder are melted into place using a high-powered laser beam.
Testing showed the printed design -- a titanium (Ti-6Al-4V TP-HSL) lattice cube -- was 50% stronger than cast magnesium alloy WE54, the strongest alloy of similar density used in aerospace applications. The new structure had effectively halved the amount of stress concentrated on the lattice's infamous weak points.
The double lattice design also means any cracks are deflected along the structure, further enhancing the toughness.
Study lead author and RMIT PhD candidate Jordan Noronha said they could make this structure at the scale of several millimeters or several meters in size using different types of printers.
This printability, along with the strength, biocompatibility, corrosion, and heat resistance, make it a promising candidate for many applications from medical devices such as bone implants to aircraft or rocket parts.
"Compared with the strongest available cast magnesium alloy currently used in commercial applications requiring high strength and light weight, our titanium metamaterial with a comparable density was shown to be much stronger or less susceptible to permanent shape change under compressive loading, not to mention more feasible to manufacture," Noronha said.
The team plans to further refine the material for maximum efficiency and explore applications in higher-temperature environments.
While currently resistant to temperatures as high as 350 °C, they believe it could be made to withstand temperatures up to 600 °C using more heat-resistant titanium alloys for applications in aerospace or firefighting drones.
As the technology to make this new material is not yet widely available, its adoption by industry might take some time.
"Traditional manufacturing processes are not practical for the fabrication of these intricate metal metamaterials, and not everyone has a laser powder bed fusion machine in their warehouse," he said. "However, as the technology develops, it will become more accessible and the printing process will become much faster, enabling a larger audience to implement our high-strength multi-topology metamaterials in their components. Importantly, metal 3D printing allows easy net shape fabrication for real applications."
Technical Director of RMIT's Advanced Manufacturing Precinct, Distinguished Professor Milan Brandt, said the team welcomed companies wanting to collaborate on the many potential applications. "Our approach is to identify challenges and create opportunities through collaborative design, knowledge exchange, work-based learning, critical problem solving, and translation of research," he said.
The U.S. Department of Defense has finally, after much speculation and anticipation, given the green light to production of the Northrop Grumman B-21 Raider, the Air Force’s newest stealth bomber. The aircraft is named after the daring air raid of Japan's islands, including Tokyo, during World War II. These were led by Lt. Col. James “Jimmy” Doolittle, a mission that the Air Force said “changed the course of World War II.”
Defense undersecretary William LaPlante told Defense One that Northrop Grumman will begin production in low numbers following the B-21's testing and then providing a solid path forward for its manufacture.
The U.S. Air Force wants at least 100 B-21 aircraft, but Northrop Grumman pointed out that a few defense analysts have said they believe the order number should be closer to 200.
The first B-21s could be delivered as soon as 2025-2026. The B-21 Raider has been in the development and planning stage for more than a decade now. Once it becomes operational, the B-21 will serve as a nuclear deterrent and help carry out national security objectives.
The Air Force described the B-21 Raider as a component of a larger family of long-range strike systems including intelligence, reconnaissance, attack, and communications. The aircraft is designed to carry nuclear weapons and will be able to support both manned and unmanned operations.
Incredibly, this shape can cover an infinite area with a pattern that never repeats. A small sample of that pattern is shown above.
The 13-sided tile also called “the hat” can fully cover an infinite plane without gaps. The tile’s pattern never repeats, making it an example of a long-sought shape known as an “Einstein.” This hat was the first true example of an “einstein.” That’s the name for a special type of shape that can tile a plane. Much like common ceramic wall or floor tile, it can cover an entire surface with no gaps or overlaps. It can even tile a plane that’s infinitely big. But the magic is that an Einstein tile does this with a pattern that never repeats.
Scientifically, they are described as being aperiodic shapes. That means the Einstein or hat shape cannot form a repeating pattern.
Scientists have solved a decades-long puzzle and unveiled a near unbreakable substance that could rival diamond as the hardest material on earth, a new study says.
A research team from Scotland, Germany, and Sweden has found that when carbon and nitrogen precursors are subjected to extreme heat and pressure, the resulting materials, known as carbon nitrides, are tougher than cubic boron nitride, the second-hardest material after diamond.
The breakthrough opens doors for multifunctional materials to be used for industrial purposes including protective coatings for cars and spaceships, high-endurance cutting tools, solar panels, and photodetectors, the experts say.
Materials researchers have attempted to unlock the potential of carbon nitrides since the 1980s, when scientists first noticed their exceptional properties, including high resistance to heat. Yet, after more than three decades of research and multiple attempts to synthesize them, no credible results were reported.
Now, an international team of scientists, led by researchers from the Center for Science at Extreme Conditions at the University of Edinburgh and experts from the University of Bayreuth, Germany, and the University of Linkoping, Sweden, have finally achieved a breakthrough.
The team subjected various forms of carbon nitrogen precursors to pressures between 70 and 135 gigapascals -- around one million times our atmospheric pressure -- while heating them to temperatures of more than 1,500 degrees C.
To identify the atomic arrangement of the compounds under these conditions, the samples were illuminated by an intense X-ray beam at three particle accelerators: the European Synchrotron Research Facility in France, the Deutsches Elektronen-Synchrotron in Germany, and the Advanced Photon Source based in the United States.
The researchers discovered that three carbon nitride compounds were found to have the necessary building blocks for super hardness. Remarkably, all three compounds retained their diamond-like qualities when they returned to ambient pressure and temperature conditions.
Further calculations and experiments suggest the new materials contain additional properties including photoluminescence and high energy density, where a large amount of energy can be stored in a small amount of mass.
Researchers say the potential applications of these ultra-incompressible carbon nitrides is vast, potentially positioning them as ultimate engineering materials to rival diamonds.
"These materials provide strong incentive to bridge the gap between high-pressure materials synthesis and industrial applications," said Dr. Dominique Laniel, Future Leaders Fellow, Institute for Condensed Matter Physics and Complex Systems, School of Physics and Astronomy, University of Edinburgh.
ORNL's vertically aligned carbon nanotubes reduce friction to nearly zero to improve energy efficiency. Credit: Chanaka Kumara/ORNL, U.S. Dept. of Energy
Scientists at the Department of Energy's Oak Ridge National Laboratory have invented a coating that could dramatically reduce friction in common load-bearing systems with moving parts, from vehicle drive trains to wind and hydroelectric turbines. It reduces the friction of steel rubbing on steel at least a hundredfold. The novel ORNL coating could help grease a U.S. economy that each year loses more than $1 trillion to friction and wear—equivalent to 5% of the gross national product.
"When components are sliding past each other, there's friction and wear," said Jun Qu, leader of ORNL's Surface Engineering and Tribology group. Tribology, from the Greek word for rubbing, is the science and technology of interacting surfaces in relative motion, such as gears and bearings. "If we reduce friction, we can reduce energy consumption. If we reduce wear, we can elongate the lifespan of the system for better durability and reliability."
With ORNL colleagues Chanaka Kumara and Michael Lance, Qu led a study published inMaterials Today Nanoabout a coating composed ofcarbonnanotubes that imparts superlubricity to sliding parts. Superlubricity is the property of showing virtually no resistance to sliding; its hallmark is a coefficient of friction less than 0.01. In comparison, when dry metals slide past each other, the coefficient of friction is around 0.5. With an oil lubricant, the coefficient of friction falls to about 0.1. However, the ORNL coating reduced the coefficient of friction far below the cutoff for superlubricity, to as low as 0.001.
"Our main achievement is we make superlubricity feasible for the most common applications," Qu said. "Before, you'd only see it in either nanoscale or specialty environments."
For the study, Kumara grew carbon nanotubes on steel plates. With a machine called a tribometer, he and Qu made the plates rub against each other to generate carbon-nanotube shavings.
Themultiwalled carbon nanotubescoat the steel, repel corrosive moisture, and function as a lubricant reservoir. When they are first deposited, the vertically aligned carbon nanotubes stand on the surface like blades of grass. When steel parts slide past each other, they essentially "cut the grass." Each blade is hollow but made of multiple layers of rolledgraphene, an atomically thin sheet of carbon arranged in adjacent hexagons like chicken wire. The fracturedcarbon nanotubedebris from the shaving is redeposited onto the contact surface, forming a graphene-rich tribofilm that reduces friction to nearly zero.
Making the carbon nanotubes is a multistep process. "First, we need to activate the steel surface to produce tiny structures, on the size scale of nanometers. Second, we need to provide acarbon sourceto grow the carbon nanotubes," Kumara said. He heated a stainless-steel disk to form metal-oxide particles on the surface. Then he usedchemical vapor depositionto introduce carbon in the form of ethanol so that metal-oxide particles can stitch carbon there, atom by atom in the form of nanotubes.
A stainless-steel disk was heated to create iron and nickel oxide particles on its surface. The particles catalyzed carbon nanotube growth during chemical vapor deposition. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
ORNL researchers used a tribometer for friction testing to show that carbon nanotubes in the presence of even one drop of oil could sustain superlubricity over 500,000 cycles. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
A stainless-steel disk was heated to create iron and nickel oxide particles on its surface. The particles catalyzed carbon nanotube growth during chemical vapor deposition. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
ORNL researchers used a tribometer for friction testing to show that carbon nanotubes in the presence of even one drop of oil could sustain superlubricity over 500,000 cycles. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
The new nanotubes do not provide superlubricity until they are damaged. "The carbon nanotubes are destroyed in the rubbing but become a new thing," Qu said. "The key part is those fractured carbon nanotubes are pieces of graphene. Those graphene pieces are smeared and connected to the contact area, becoming what we call tribofilm, a coating formed during the process. Then both contact surfaces are covered by some graphene-rich coating. Now, when they rub each other, it's graphene on graphene."
The presence of even one drop of oil is crucial to achieving superlubricity. "We tried it without oil; it didn't work," Qu said. "The reason is, without oil, friction removes the carbon nanotubes too aggressively. Then the tribofilm cannot form nicely or survive long. It's like an engine without oil. It smokes in a few minutes, whereas one with oil can easily run for years."
The ORNL coating's superior slipperiness has staying power. Superlubricity persisted in tests of more than 500,000 rubbing cycles. Kumara tested the performances for continuous sliding over three hours, then one day and later 12 days. "We still got superlubricity," he said. "It's stable."
Usingelectron microscopy, Kumara examined the mowed fragments to prove that tribological wear had severed the carbon nanotubes. To independently confirm that rubbing had shortened the nanotubes, ORNL co-author Lance used Raman spectroscopy, a technique that measures vibrational energy, which is related to the atomic bonding and crystal structure of a material.
"Tribology is a very old field, but modern science and engineering provided a new scientific approach to advance technology in this area," Qu said. "The fundamental understanding has been shallow until the last maybe 20 years, when tribology got a new life. More recently, scientists and engineers really came together to use the more advanced material characterization technologies—that's an ORNL strength. Tribology is very multidisciplinary. No one is an expert in everything. Therefore, in tribology, the key to success is collaboration."
He added, "Somewhere, you can find a scientist with expertise in carbon nanotubes, a scientist with expertise in tribology, a scientist with expertise in materials characterization. But they are isolated. Here at ORNL, we are together."
Chanaka Kumara of ORNL used a chemical vapor deposition system, in the background, to coat a stainless-steel disc, in the foreground, with carbon nanotubes. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
Jun Qu of ORNL shows stainless-steel disks before (silver) and after (black) coating with carbon nanotubes that provide superlubricity. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
Chanaka Kumara of ORNL used a chemical vapor deposition system, in the background, to coat a stainless-steel disc, in the foreground, with carbon nanotubes. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
Jun Qu of ORNL shows stainless-steel disks before (silver) and after (black) coating with carbon nanotubes that provide superlubricity. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
ORNL's tribology teams have done award-winning work that has attracted industrial partnerships and licensing. In 2014, an ionic anti-wear additive for fuel-efficient engine lubricants, developed by ORNL, General Motors, Shell Global Solutions and Lubrizol, won an R&D 100 award. ORNL's collaborators were Qu, Huimin Luo, Sheng Dai, Peter Blau, Todd Toops, Brian West and Bruce Bunting.
Similarly, the work described in the current paper was a finalist for an R&D 100 award in 2020. The researchers have applied for a patent of their novel superlubricity coating.
"Next, we hope to partner with industry to write a joint proposal to DOE to test, mature and license the technology," Qu said. "In a decade we'd like to see improved high-performance vehicles and power plants with less energy lost to friction and wear."
More information:Chanaka Kumara et al, Macroscale superlubricity by a sacrificial carbon nanotube coating,Materials Today Nano(2022).DOI: 10.1016/j.mtnano.2022.100297
Bearings need a minimum load to function properly. Inadequate load can be as damaging as excessive load. Damage from insufficient load appears as smearing on the rolling elements and races. This is especially important with cylindrical roller bearings since they are designed for larger loads.
This Is Your Bearing On Drugs - Bearing Maintenance Or A Lack Thereof
Have a regular maintenance program for your machines? If not, this can happen:
This was once the center roller bearing in a planetary gear box. The I.D. measures about 100mm, give or take about 30mm.
The shop that this machine was in had fired their previous maintenance manager because, according to them, "They were experiencing too much downtime because of his excessive maintenance of the machines".
So this is the result of what is called, "deferred maintenance"
So if you want to upgrade your bearings to square rollers, keep on deferring maintenance. It helps OUR business!
