There’s more to multifunctional ultra-flyweight aerogel produced at a Zhejiang U. lab than just ‘world’s lightest material’ record
I suspect this story may seem a little like old news to some readers, but a lot of the pop-sci reporting in the last few days about a new ultralight aerogel (actually, a UFA or ultra-flyweight aerogel, i.e., less than 1 mg cm−3) has missed the point by a wide margin. The big takeaway from this story, as documented in a new Advanced Materials paper, is that the graphene–carbon nanotube (CNT) aerogel is relatively easy to make, appears to be easily scalable, and is moldable into any shape. Moreover, the new UFA, besides having ultralow density, also is extremely flexible and elastic—with the elasticity independent of temperature—and is thermally stable, a good electrical conductor, hydrophobic, and capable of absorbing extremely high capacities for organic liquids and phase change materials.
Now, certainly, there is a significant gee-whiz factor for gaining the “world’s lightest material” title, an achievement based on a density of 0.16 mg cm−3, accomplished by the research team at Zhejiang University headed by Gao Chao.
The group’s material is not the first UFA. Within the past 18 months, other researchers have constructed nickel foams with density of 0.9 mg cm−3 (via electroless plating and subsequently etching away a polymer template), and another group constructed an aerographite with a density of 0.18 mg cm−3 (via a ZnO template-based chemical vapor deposition approach). But, both groups’ dependency on a template also creates enormous limitations to scalability. Sol-gel-derived, low-density aerogels can be made on fairly large scales, but with sol-gel processes it is difficult to control the dimensions of the structures.
Gao’s group, instead, uses a process that involves freeze-drying aqueous solutions of CNTs and giant graphene oxide (GGO) sheets, followed by chemical reduction of graphene oxide into graphene using hydrazine vapor. The researchers named their method a “sol-cryo” approach and note in their paper that it is easy to make large samples:
Because of the simplicity of assembly process in our template-free “sol-cryo” methodology and the large-scale availability of GGO and CNTs, the integrated all-carbon aerogels with desired densities and shapes such as rods, cylinders, papers and cubes were readily accessible. More significantly, UFAs can be easily manufactured in a large-scale. For example, a UFA cylinder up to 1000 cm3 was made with a mold of 1-liter plate.
A story on the university’s website reports quotes Gao saying, ”With no need for templates, its size only depends on that of the container. [A] bigger container can help produce the aerogel in bigger size, even to thousands of cubic centimeters or larger.” The story also reports that Gao believes ”the value of this achievement lies not in the record but in its simple way in developing the material and the superior performance exhibited.”
Briefly speaking, the microstructure of the material is a 3D porous framework constructed with cell walls of randomly oriented, crinkly graphene sheets and CNT “ribs.” The macropores ranged from hundreds of nanometers to tens of micrometers. The authors of the paper say the properties of the UFA derive from the graphene-CNT synergy: “Giant graphene flakes build a framework with macro-pores, making the aerogel ultralight; the coating of CNTs reinforces the relatively flexible graphene substrate and endows their intrinsic elasticity to the coorganized aerogel.”
One of the UFA’s interesting properties is its elasticity that allows it to be repeatedly compressed and returned to its nearly original size. This sponginess comes in handy in combination with another property: It can rapidly absorb up to 900 times its own weight in oil or other organic liquids. For example, one gram can absorb 68.8 grams of organics per second. The elasticity remained the same in tests that ranged from −190 to 300°C. The elasticity also remained after researchers annealed the UFA at 900°C for five hours.
There are probably many ways the elasticity and absorbability can be useful, not the least of which is that, because of its hydrophobicity, it could be a reusable medium to soak up oil spills on lakes and oceans. Gao says in the university story, “Maybe one day when oil spill occurs, we can scatter them on the sea and absorb the oil quickly. Due to its elasticity, both the oil absorbed and the aerogel can be recycled.” (Another Chinese research group working at Tsinghua and Peking Universities published a paper in 2010 about the use of CNTs for oil spills, and I suspect that there is some overlap between the work of the two groups.)
Another property of the UFA is that it has elasticity-dependent electrical conductivity. For example, they report connecting an LED lamp top the UFA bulk, and “its brightness fluctuates upon compressing and releasing the aerogel. This phenomenon promises the application of UFAs as pressure-responsive sensors.”
They also say that by loading the UFA with tiny amounts of certain liquids (say, CCl4 or 1-hexadecanol), they can make conductive composites with very high electrical conductivity compared to just CNT- or graphene-based composites.
Video of variable conductivity of UFA demonstrating current change to LED when aerogel is compressed and released. Credit: Gao et al.; Advanced Materials.
Gao and the other authors also suggest the UFA could find use as supercapacitors and catalyst beds, but another intriguing application they only hint at is its use as a medium that enhances phase-change energy storage materials. For example, unlike other composites, a UFA-paraffin combination delivers higher phase-change enthalpy (ΔH) than ordinary paraffin.
These applications may only be the beginning. When it comes to learning how to leverage the properties of their fluffy stuff, the researchers say their new UFA is “just like a new-born baby.” A baby that was, perhaps, born with a silver spoon in its mouth.
Official video (in Spanish only) on new “Innovative Argentina 2020. Credit: Ministry of Science.
I am someone who thinks people in the United States pay far too little attention and give far too little credit to what goes on in Central and South America. For that reason, I try to follow some of the larger news developments in that region, particularly if it has to do with science and engineering. Thus, it definitely caught my attention last week when I saw a report that the Argentine government proposed a new national science strategy, a plan called (I think translated correctly) “Innovative Argentina 2020.” (hat tip to the Knight Science Journalism Tracker at MIT).
As far as I can tell, the new plan sets some huge and admirable goals—I am agnostic about whether the nation has the resources and leadership to achieve them—the main features of which are 1) triple the investment in science, 2) double the number of researchers, and 3) get Argentine researchers who have settled elsewhere to return to their homeland.
The time frame for the first two goals is seven years. Unfortunately, I haven’t been able to find anything that lays out a roadmap for either one, or explains the funding sources for expanding the National System of Science, Technology and Innovation.
However, a Google translation of the story I have linked to above seems to indicate that the repatriation issue is a touchy one. Lino Barañao, the government’s science and technology minister, asked rhetorically while presenting the plan, which of the nations great resources were the most poorly managed? He said that most people would suggest the answer is oil. Barañao said the right answer is “even more embarrassing—it is the brains of Argentine scientists.” He went on to say that, in essence, Argentina generously gave free brainpower, and the ability it has to generate prosperity, to the northern hemisphere, and because education in Argentina is free, this means there was “a clear net transfer of resources.”
I don’t claim to know all the factors that come into play when an Argentine scientist or engineer is making a decision about whether to stay or leave, but I do know that there was a time under an adverse political and military situation in Argentina when people with or pursuing degrees were persona non grata, and often among the “disappeared.” Indeed, Barañao, himself, noted there was a time when researchers were “considered dangerous, or at least expendable, ‘because the technology was coming from outside’.”
Lack of respect may be another problem. Barañao explained that because of the lack of support, scientists believe, “We do not ask anything [of Argentina], but do not ask anything of us.” In these circumstances some sit and distance themselves from a society they consider not sufficiently appreciated. The story also speaks of other cultural issues:
Barañao spoke of strengthening the system that involves more collaboration, and that both science universities and companies must pull in the same direction, so that citizens actually receive something in return for their taxes. There is reticence among all the parties, in which the scientist sees the entrepreneur as a selfish entity only thinking of profit, and the employer sees the researcher as a parasite that sucks but never produces anything but sterile knowledge.Barañao said these ideas are false and must be banished by all sides.
I traveled in Argentina around 2003 and, as I recall, the nation then was trying to elevate science and technology, so I assume the new plan is an attempt at achieve some exponential growth. The story reports that investment in science and technology in 2002 was about 0.44 percent of GDP, and the new plan will increase funding from the current 0.65 percent of GDP to 1.65 percent in 2020.
The author of the story injects some of his own opinion, writing that after listening to the plan, “You do not stop thinking about the senseless stupidity that is to ignore the brightest minds of a country.” But he goes on to note that not every Argentine leader has a firm grip on science, and reports that President Cristina Fernandez, bumbled her role in announcing the plan by asserting, for example, that “diabetes is a disease of affluent people” and that Argentine Amaranth also has some essential amino acids “that we do not have.” Of course, Argentina does not have a lock on the stockpile of politicians who haven’t got a clue about S&T.
Today I am linking to videos mainly because they are cool and not because they have a strong tie to materials science. These short looping videos, which are oddly hypnotic (for me, anyway), are the work of Jean Rajchenbach, Didier Clamond, and Alphonse Leroux, whose paper on “Observation of star-shaped surface gravity waves,” is slated for a future issue of Physical Review Letters (preprint pdf).
The authors work at CNRS, in France, and their paper reports on their observation of new types of standing waves. Nonlinear effects in certain fluids, according to an email from the American Physical Society, “can give rise to remarkable phenomena such as ‘freak,’ ‘horse-shoe,’ and ’solitary’ waves (solitons), which sometimes are found to have important counterparts in other domains of physics, from optics to cold-atom physics. … The shapes of the waves are entirely determined by gravity, rather than surface tension, and can display a star-like or a polygonal shape, depending on the amplitude and frequency of the driving vibration. The resulting wave patterns, according to the authors’ model, stem from the resonant and nonlinear interactions between multiple waves traversing the liquid.”
As it it turns out, the emergence of the idea that solitons actually exist is a great example of early computer modeling and simulation. According to a separate APS story, the 1965 discovery and explanation for solitons was a direct result of the nascent computer technology available in federal lab. The story goes:
In 1955 Enrico Fermi, John Pasta, and Stanislaw Ulam (FPU) came across a puzzling result when using the MANIAC I computer at what was then called the Los Alamos Scientific Laboratory in New Mexico. They wrote a program to follow the motion of up to 64 masses connected by springs in a horizontal line. Each mass could move only in the direction of the line, stretching or compressing the two springs connected to it.
The team started the simulation by displacing each mass from its initial position in a pattern that formed one half of a sine wave, with the end masses having zero displacement and the middle masses having the greatest displacement. The masses would then oscillate, and if the springs were strictly linear—that is, if their force were proportional to the amount of stretch or compression—then a snapshot of the motion at any time in the future would show the masses still in a sine wave pattern. But Fermi and his colleagues added a small degree of nonlinearity to the springs’ force, expecting it to break up the sine wave and cause the oscillation energy to become, in time, equally distributed among all the masses.
That’s not what happened. Although the sine wave indeed evolved into a more complex oscillation, the motion of the masses never became completely disorderly, and in fact it periodically returned to the initial state.
A decade later, Norman Zabusky, then at Bell Labs in Whippany, N.J., collaborated with Martin Kruskal of Princeton University to re-examine the FPU work. They transformed the discrete masses-and-springs equation into one for a continuous system similar to water waves. The team then programmed a computer to calculate the wave motion over a fixed horizontal distance but in such a way that a disturbance passing out of one side of the range reappeared at the other side. Like FPU, Zabusky and Kruskal set the system in motion with an initial sine wave pattern. As the wave rolled along, its leading edge became steadily steeper and then developed smaller-wavelength ripples. These ripples eventually grew into individual waves that moved independently, with a velocity that depended on their height. Remarkably, when these new waves occasionally collided, they passed through each other, emerging almost wholly unscathed from their encounters. In addition, the waves would regularly align to reproduce the initial sine wave, momentarily, before separating again and repeating—not quite perfectly—the same cycle. This phenomenon was similar to the periodic return to the initial state that FPU had observed.
The discovery may have brought a sense of relief to those who had reported (documented sightings go back to the 1830s) seeing single waves in oceans and canals.
One of the highlights of the Expo each year during the ICACC conference is the Shot Glass Drop Competition sponsored by the Schott North America. The competition—mainly for fun and bragging rights—involves engineering a container composed only of plastic straws that is designed to protect a glass shot glass as it is dropped from increasing heights.
As featured in the above video the 2013 competition literally reached new heights with the help of a motorized lift platform. In previous years, the designs were so good that many shot glasses survived drops from the tallest ladder available, a 15-footer. This year, organizers arranged for a motorized lift to be available—and it was needed! Two shot glass entries survived even 18-foot drops, forcing the competition to a record 21-foot height. This final drop pitted a container designed by Sylvia Johnson, an ACerS Member and chief materials technologist for entry systems and technology at NASA Ames Research Center, against a design by Christian Espinoza-Santos and Daniel Ribero Rodriquez, graduate students at the University of Illinois at Urbana–Champaign.
The winner: the team of Espinoza-Santos and Ribero Rodriquez—by a crack!
Also, a big thanks goes to Vision Research, a company that provided the audience that watched the competition with super slow-motion replays of the shot glass impacts. Vision Research is a manufacturer of the Phantom brand of digital high-speed imaging systems used across a wide variety of applications including defense, engineering, science, medical research, industrial manufacturing, packaging, sports broadcast, TV production, and digital cinematography. According to the Wayne, N.J.-based company, Vision Research “designs and manufactures the most comprehensive range of digital high-speed cameras available today, all of which deliver unsurpassed light-sensitivity, image resolution, acquisition speed and image quality. Over the course of its 60+ year history, Vision Research has earned numerous awards in recognition of its innovations in high-speed digital camera technology and sensor design, including a technical Emmy and an Academy Award. Vision Research sets the benchmark in the high-speed imaging industry, adding a new dimension to the sense of sight, allowing the user to see details of an event when it’s too fast to see, and too important not to.” For additional information regarding Vision Research, please visit the company’s website.
Two new developments and announcements related to graphene research indicate that the European region is more than ever committed to major R&D work with the extraordinary material.
The first development came in a formal announcement from the UK’s University of Cambridge, which announced that on Feb. 1, 2013, the school would begin work on a new graphene research center that it hopes to dedicate by the end of the year. The Cambridge Graphene Center will be launched with £12 million from the government’s Engineering and Physical Sciences Research Council, plus an estimated additional £13 million from private-sector partners that include Nokia, Dyson, Plastic Logic, Philips and BAE Systems. According to the university’s announcement, the center “will target the manufacture of graphene on an industrial scale, and applications in the areas of flexible electronics, energy, connectivity, and optoelectronics.”
The second development came in the form of news leaks about a huge new graphene consortium that is a frontrunner in a unique and nicely endowed scientific-technical competition organized by the European Commission. The AAAS has described the EU’s Future and Emerging Technologies Flagship Initiative (FET) as “the biggest funding contest the European Union has ever hosted,” with over €100 million to be given to the winner(s) in the first few years and the possibility of even more in outlying years.” The winner(s) of the competition are to be officially announced Monday (Jan. 28), but the word on the street is that a project called the Graphene Flagship is one of two FET winners (the other project be enormous supercomputer-based neuroscience effort called the Human Brain Project).
If true—and there has been no EU denial—the two projects will share €107 million for the first two-and-a-half years, and then €50 million each per year after that. The Graphene Flagship, an enormous entity that according to its website encompasses 74 legal partners, 136 principal investigators, 120 research groups, and four Nobel laureates, also could benefit from £70 million in outside funding. The details of the GF proposal are a little sketchy, and a public roadmap is supposed to be forthcoming.
All of this is on top of the Graphene Global Research and Technology Hub, announced in late 2011, centered at the UK’s University of Manchester.
It is hard to imagine that all three projects won’t cooperate both formally and informally. Indeed, the university announced that the Cambridge initiative would receive an additional £11 million of European Research Council funding to support activities with the Manchester effort. Further, the video below was produced by Cambridge University on behalf of the Graphene Flagship, so it would appear that a cooperative R&D community focused on graphene is already underway in Europe.
It’s also hard to imagine that a focus of this scale on this two-dimensional material won’t yield in multidimensional strategic payoff that will elevate Europe’s scientific prestige in the world.