Discover Magazine, January 1999, page 38
Technology 1998 --Tomorrow's Tubes
by Jeffrey Winter
Ever since they were discovered in 1991, carbon nanotubes --cylindrical molecules of graphite that look a bit like rolled-up chicken wire -- have been touted as the material of the future. Pound for pound, carbon nanotubes are about a hundred times stronger than steel and transport heat better than any other known material. But while bridges suspended from whisker-thin nanotube cables are probably some decades away, a newly discovered realm of application for the strange molecules -- electronics -- may be at hand.
When a carbon atom links up with neighboring carbons to make a sheet of graphite, some of the atoms' electrons are left unbound, free to roam around and conduct electricity throughout the sheet. Because carbon nanotubes are simply graphite tubes, it was not surprising that they could also conduct electricity.
But in June, Walter de Heer and his colleagues at Georgia Tech found that nanotubes can do something no ordinary wires can do-- conduct electricity with almost no resistance at room temperature.
While nanotubes are not superconductors (the current in a superconductor, unlike that in nanotubes, continues to flow even when the power source is shut off), their highly regular molecular structure allows electrons to flow freely without losing energy in collisions with stray atoms. Resistance-free nanotube wires could greatly reduce the size of electronic components.
Other research groups found equally surprising properties. In January, teams at Harvard and at Delft University of Technology in the Netherlands demonstrated that nanotubes made of a single layer of carbon could conduct electricity either like a metal or like a semiconductor, depending on the alignment of carbon atoms in the nanotube. By May, Cees Dekker of the Delft team had managed to rig up the world's first nanotube transistor; it was less than a tenth of the size of a conventional semiconductor transistor.
Physicists are already talking about stringing together nanotubes to create carbon-based molecular electronic devices to replace the ubiquitous silicon- based computer chips.
Says Walter de Heer: "There's a new era of electronics awaiting for us."
2002 NASA Web page
The Right Stuff for Super Spaceships
Tomorrow's spacecraft will be built using advanced materials with mind-boggling properties.
Revolutions in technology--like the Industrial Revolution that replaced horses with cars--can make what seems impossible today commonplace tomorrow.
Such a revolution is happening right now. Three of the fastest-growing sciences of our day--biotech, nanotech, and information technology--are converging to give scientists unprecedented control of matter on the molecular scale. Emerging from this intellectual gold-rush is a new class of materials with astounding properties that sound more at home in a science fiction novel than on the laboratory workbench.
Imagine, for example, a substance with 100 times the strength of steel, yet only 1/6 the weight; materials that instantly heal themselves when punctured; surfaces that can "feel" the forces pressing on them; wires and electronics as tiny as molecules; structural materials that also generate and store electricity; and liquids that can instantly switch to solid and back again at will. All of these materials exist today ... and more are on the way.
With such mind-boggling materials at hand, building the better spacecraft starts to look not so far fetched after all.
... Composite materials, like those used in carbon-fiber tennis rackets and golf clubs, have already done much to help bring weight down in aerospace designs without compromising strength. But a new form of carbon called a "carbon nanotube" holds the promise of a dramatic improvement over composites: The best composites have 3 or 4 times the strength of steel by weight--for nanotubes, it's 600 times!
"This phenomenal strength comes from the molecular structure of nanotubes," explains Dennis Bushnell, a chief scientist at Langley Research Center (LaRC), NASA's Center of Excellence for Structures and Materials. They look a bit like chicken-wire rolled into a cylinder with carbon atoms sitting at each of the hexagons' corners. Typically nanotubes are about 1.2 to 1.4 nanometers across (a nanometer is one-billionth of a meter), which is only about 10 times the radius of the carbon atoms themselves.
Nanotubes were only discovered in 1991, but already the intense interest in the scientific community has advanced our ability to create and use nanotubes tremendously. Only 2 to 3 years ago, the longest nanotubes that had been made were about 1000 nanometers long (1 micron). Today, scientists are able to grow tubes as long as 200 million nanometers (20 cm). Bushnell notes that there are at least 56 labs around the world working to mass produce these tiny tubes.
"Great strides are being made, so making bulk materials using nanotubes will probably happen," Bushnell says. "What we don't know is how much of this 600 times the strength of steel by weight will be manifest in a bulk material. Still, nanotubes are our best bet."
Beyond merely being strong, nanotubes will likely be important for another part of the spacecraft weight-loss plan: materials that can serve more than just one function.
"We used to build structures that were just dumb, dead-weight holders for active parts, such as sensors, processors, and instruments," Marzwell explains. "Now we don't need that. The holder can be an integral, active part of the system."
Imagine that the body of a spacecraft could also store power, removing the need for heavy batteries. Or that surfaces could bend themselves, doing away with separate actuators. Or that circuitry could be embedded directly into the body of the spacecraft. When materials can be designed on the molecular scale such holistic structures become possible...
Other
July 2001 -- Army R&D developing super-lightweight armor
In the excerpt below, notice how the article talks about creating body armor that theoretically could be 2 or even 3 orders of magnitude lighter in weight than present armor. Something as thin as a piece of paper could stop a .45 caliber bullet. Furthermore, it could have electronics and power supply integrated right into the armor. Though not stated, the proposed armor is probably based around carbon nanotubules with their enormous strength, lightness, plus the ability to vary their electrical properties and theoretically create integrated electronics.
Army Exploring Nanotechnology And Robotics
by Kelly Hearns, UPI Technology Writer, 7/1/01
Q. How much is the Army going to use nanotechnology, say, over the next decade?
A. The university laboratories have been making pretty good progress in nanoscience. And technology follows science. Until you understand the science you can't move into technology efforts. You have to have equipment to allow for the fabrication of materials and devices on the nanoscale. So we have to have a good characterization before we are ready to move into the fabrication and application state. We'll see progress in the field of materials, new materials and our new Institute For Soldier Nanotechnology will focus on soldiers' uniforms.
Our first step is to develop a uniform, using nanoscale materials to integrate electronics, computer devices and power supply. And for ballistic protection. For example, today if you want to stop a .45 caliber bullet you need about 10 to 20 pounds per square foot. Where we are headed with nanoscience and technology is the ability to stop a bullet with as much as two or three orders of magnitude less in pounds, something as thin and light as a piece of paper stopping a .45 caliber bullet. That's the potential. If we could drop this under one pound per square foot we've made dramatic progress. So, our mark on the wall is more than a factor of 10 drop in that ballistic protection. Also, we hope to get technologies into the marketplace so volumes will grow and prices will drop.
1997 NASA TECHNICAL REPORT
(Originally at http://www.nas.nasa.gov/nanotechnology)
The following portions of a technical report from NASA described a paper by Jie Han, Al Globus, Richard Jaffe and Glenn Deardorff of NASA's Ames Research Center, Mountain View, CA. In this paper, the authors describe the physical properties of materials which their computer models indicate could be assembled at the molecular level through the use of molecular "nanomachines."
"We would like to write computer programs that would enable assembler/ replicators to make aerospace materials, parts and machines in atomic detail," he [Globus] said. "Such materials should have tremendous strength and thermal properties."
A long range goal, according to Globus, is to make materials that have radically superior strength-to-weight ratio. Diamond, for example, has 69 times the strength-to-weight ratio of titanium. A second goal is to make "active" or "smart" materials.
"There is absolutely no question that active materials can be made," Globus explained. "Look at your skin. It repairs itself. It sweats to cool itself. It stretches as it grows. It's an active material," he said.
NSS (NATIONAL SPACE SOCIETY) POSITION PAPER
ON SPACE AND NANOTECHNOLOGY
[From former Website http://www.public.iastate.edu/~bhein/txt/mmsg.txt]
[Nanotech aerospace] products might include bulk structures such as spacecraft components made of a diamond-titanium composite, or other "wonder" materials. The theoretical strength-to-density ratio of matter is about 75 times that currently achieved by aerospace aluminum alloys, partially because current manufacturing capability allows macro-molecular defects that weaken the material.
A dense network of distributed embedded sensors throughout a manned or unmanned spacecraft could continuously monitor (and affect, if they could be operated as actuators) mechanical stresses, temperature gradients, incident radiation, and other parameters to ensure mission safety and optimize system control. In an advanced spacecraft, the outer skin would not only keep out the cold and the vacuum, but it might also function as a multi-sensor camera and antenna.
Tiny computers, sensors and actuators, trivially cheap on a per-unit basis, may allow things like smart walls to automatically repair micrometeorite damage.
Super Titanium Alloys
(New! Added March 2004)
DISCOVER Magazine, Vol. 25 No. 04, April 2004
Glassy Metals
Harder, stronger, and better--the material of the future
By Brad Lemley
The wispy metal strip in my hands is 8 inches long, 1 inch wide, and as thin as aluminum foil. "Try to tear it," says William Johnson, a materials science professor at Caltech in Pasadena. I pull first gently, but soon with all my might. No go.
"See if you can cut this," suggests Johnson's postgraduate assistant Jason Kang, handing me a mirror-bright piece of the same metal. It's an inch long, a quarter inch wide, and thinner than a dime. I bear down with a heavy-duty pair of wire cutters. The metal will not cut. I try again, squeezing with both hands until my fingers ache. Nothing.
A steel sphere dropped on a rigid plate of amorphous metal bounces like a rubber Super Ball. Conventional metals would dent as the crystals that compose them dislocate. But the plate--an alloy of zirconium, titanium, nickel, copper, and beryllium--has no crystals. Any atoms in the alloy that are displaced under impact quickly snap all the way back, enabling the sphere to continue bouncing with very little loss of energy.
It's all astounding, yet oddly familiar. In the typical science fiction film circa 1950, there's that scene in which scientists return from the just-landed flying saucer and tell the Army brass that no tool known to humankind can cut, burn, bend, or otherwise scar the hull. But the metal in front of me is decidedly terrestrial in origin
It is called metallic glass, or amorphous metal, and it appears to be nothing less than an entirely new class of material that can be used to build lighter, stronger versions of anything. ... it is two to three times the strength of conventional alloys...
... If upon solidifying the resulting metallic "button" is reflective like a mirror, he knows instantly that he has made a glass. The surface reflects for the same reason the surface of a liquid reflectsthe amorphous atoms form a smooth skin that bounces light uniformly.
.... Analysis of the thin ribbons hinted that a heavy hunk of material, thick enough to be formed into structural shapes, would be like nothing seen on Earth before. Conventional metals dent, tear, and rust because of defects known as grain boundaries and dislocations, in which the crystals are pushed out of alignment and provide entry points for oxidation. Amorphous metals have no crystals that could be affected by such imperfections and hence are springy, extremely strong, and corrosion-proof.
..."Amorphous metal is really more like a plastic than anything else," says... Johnson.... "What we really have here is a metal polymer."
...Strength is not its only virtue. It can also be formed like a plastic... Better yet, it can be readily made into a foam. The fact that amorphous metal is thick and like plastic when molten permits the formation of a foam panel that is 99 percent air but roughly 100 times stronger than polystyrene. A sandwich made of two thin sheets of amorphous metal flanking amorphous foam would be strong, light, insulating, fireproof... Such panels could form buildings, ship hulls, airplanes, and car bodies.
...On the military front, the Army is testing an armor-piercing bullet called a kinetic energy penetrator for use by ground-attack jets and armored vehicles, while the Navy evaluates lightweight amorphous-alloy fragmentation bombs.
New Metal Alloy Is Super Strong.
By PETER SVENSSON, AP Business Writer
NEW YORK (AP) - July 5, 2002 -It could be the new superhero of metals.
More than twice as strong as titanium and steel, it doesn't rust and it can be cast like plastic and honed to an edge as sharp as glass. And like any superhero, it has a weakness: don't heat it too much, or it loses its strength.
The fruit of a 1992 discovery at the California Institute of Technology, the alloy, called Liquidmetal, has already been used in golf clubs. And it may soon show up in cell phone casings, baseball bats and scalpels.
..."It combines uniquely a material with exceptional properties and the ability to process the material to exceptional shapes," says Dr. Michael Ashby, professor of engineering at Cambridge University in Britain and an advisor to the company.
Liquidmetal's surprising properties come of a structure different from ordinary metals. When a conventional metal cools, it forms grains, each a small crystal where the atoms are oriented in a grid. The boundaries between these grains are a metal's weak points--it's where cracks can form and rust starts, for instance.
Scientists discovered in 1959 that if some alloys are cooled very quickly the atoms don't have time to form crystals. Instead, they remain jumbled, as in a liquid or in glass. ...In 1992, Dr. William Johnson and Dr. Atakan Pekers at the Caltech discovered a way around the cooling problem. They made an alloy of elements that fit very poorly together: titanium, copper, nickel, zirconium and beryllium. These elements' atoms are of different sizes so they don't readily form crystals, even when cooled slowly. Pieces up to an inch thick could now be made.
In the mold, Liquidmetal reveals another quality: it doesn't shrink when it solidifies. Ordinary metals do, meaning the product is rough out of the mold and needs machining.
"What happens with Liquidmetal, in essence, is that you can form parts sort of the way you form plastics," says John Kang, chief executive of Liquidmetal Technologies.
Liquidmetal can be cast with a precision down to 1 micron, or 1/25,000th of an inch, according to Johnson, now an advisor to Liquidmetal Technologies. Given a good die, it is possible to cast a scalpel blade and have it come sharp out of the mold.
...The Defense Advanced Research Projects Agency is also investigating several different uses of the alloy. One project is looking at using it in armor-piercing shells as a replacement for depleted uranium, which has been a focus of health and environmental concerns.
Then there's the issue of heat.
Much like glass, Liquidmetal softens when heated--the earliest alloy at about 750 degrees Fahrenheit. By comparison, steel becomes malleable at about 2,100 degrees. Some newer amorphous alloys are, however, much more resistant to heat, Johnson says.
...Caltech researchers are trying to create alloys consisting of cheaper metals. "If we can make a processable amorphous iron alloy with a raw material cost of a dollar a pound, it could be an enormously pervasive material," Johnson says. "It could even make its way into cars."
On the Web:
http://www.liquidmetal.com
http://www.darpa.mil/dso/thrust/md/sam/index.html
Superstrong "Plastic" Steel (New! Added Nov. 29, 2004)
Scientific American, December 2004, p. 46
Amorphous steel that could strengthen skyscapers and armor-piercing rounds
The strength of conventional steel is limited by defects that inevitably pop up in the crystalline organization of the atoms. Joseph Poon and Gary Shiflet (Prof. of physics and Prof of materials science, Univ. of Virginia) and their colleagues devised amorphous steel that lacks those defects because it has randomly arranged molecular bonds. The resulting metal has triple the strength of its crystalline counterpart and better corrosion resistance. Although scvientists have created amorphous alloys in the past, Poon and his team reported in the May 2004 Journal of Materials Research a way to make amorphous steel in bulk. The secret was adding the element yttrium, which discourages crystalization as the molten stell solidfies. The metal can then be cast in molds or shaped in the same way plastic can.
Separately, researchers at Oak Ridge National Laboratory also reported making amorphous steel in bulk. Intriguingly, both steels are nonmagnetic, which has raised the U.S. Navy's hopes of using the material in submarine and other hulls that could evade magnetic sensors.
Superalloy Announced (New! Added April 29, 2003)
New alloys bend the rules
Metal mixes are supple, stretchy, strong and heat stable.
18 April 2003
PHILIP BALL
© Corbis
A new class of metal alloys has a remarkable combination of unusual and useful properties: all its members are strong, heat-stable, supple and elastic.
The materials are compounds of titanium, zirconium, vanadium, niobium and tantalum - elements clustered together in the middle of the periodic table, in a larger group known as the transition metals. A small amount of oxygen provides an essential seasoning in the mix.
Most metals would be permanently deformed if stretched to up to 2.5 times their original length. But the new alloys spring back again - earning them the title 'super-elastic'. When pulled harder, they extend by a further 20% before they snap. This degree of stretchiness is most unusual for a metal, and is dubbed superplasticity.
The mixtures' super-elasticity means that they don't dent easily; their superplasticity means that they can be moulded without the need for heat. But it doesn't stop there, say developers Takashi Saito, of Toyota Central Research and Development Laboratories in Nagakute, Japan, and his colleagues.
When warmed, the alloys barely expand. This rare, 'invar' behaviour is characteristic of some nickel-steel mixes that were discovered in the 1890s and are used in parts of delicate mechanisms such as wristwatches and scientific measuring instruments. This refusal to expand when warmed means that the devices are accurate across a range of temperatures.
The new compounds also show 'elinvar' behaviour - their stiffness remains constant when they are heated. This effect holds over an amazingly wide temperature range - from as low as -194 °C to over 200 °C.
To cap it all, the alloys are very strong. Their tensile strength - the amount of pulling that they can stand - is about twice that of steel. And they can be bent and straightened repeatedly without becoming brittle; they don't suffer from 'work hardening', in other words.
<.....>
References
Saito, T. et al. Multifunctional alloys obtained via a dislocation-free plastic deformation mechanism. Science, 300, 464 - 467, (2003). |Homepage|
"Rubber Metal"
"Smart skin" holds promise for morphing wings and wearable computers.
by Laura Allen
Terrible, horrible things can be done to this millimeters-thick patch of shimmering material crafted by chemists at NanoSonic in Blacksburg, Virginia. Twist it, stretch it double, fry it to 200°C, douse it with jet fuel the stuff survives. After the torment, it snaps like rubber back to its original shape, all the while conducting electricity like solid metal. "Any other material would lose its conductivity," says Jennifer Hoyt Lalli, NanoSonic's director of nanocomposites.
The abused substance is called Metal Rubber... The company's small office has been flooded with calls from Fortune 500 companies and government agencies eager to test Metal Rubber's use in everything from artificial muscles to smart clothes to shape-shifting airplane wings.
... its 12-inch-by-12-inch samples... take custom-built robots up to three days to create. ...Metal Rubber, a product of nanotechnology, must be fabricated molecule by molecule.
The manufacturing process, called electrostatic self-assembly, starts with two buckets of water-based solutions, one filled with positively charged metallic ions, the other with oppositely charged elastic polymers. The robot dips a charged substrate (glass, for example) alternately from one bucket to the next. The dipping slowly builds up tight, organized layers of molecules, bonded firmly by opposing charges. Afterward the substrate is removed, leaving a freestanding sheet of Metal Rubber....
