Borrowing from pastry chefs, engineers create nanolayered composites | MIT News

Adapting an outdated trick used for hundreds of years by each metalsmiths and pastry makers, a group of researchers at MIT has discovered a approach to effectively create composite supplies containing a whole bunch of layers which are simply atoms thick however span the complete width of the fabric. The invention may open up wide-ranging prospects for designing new, easy-to-manufacture composites for optical units, digital methods, and high-tech supplies.

The work is described this week in a paper in Science by Michael Strano, the Carbon P. Dubbs Professor in Chemical Engineering; postdoc Pingwei Liu; and 11 different MIT college students, postdocs, and professors.

Supplies reminiscent of graphene, a two-dimensional type of pure carbon, and carbon nanotubes, tiny cylinders which are basically rolled-up graphene, are “a few of the strongest, hardest supplies we’ve obtainable,” says Strano, as a result of their atoms are held collectively totally by carbon-carbon bonds, that are “the strongest nature provides us” for chemical bonds to work with. So, researchers have been looking for methods of utilizing these nanomaterials so as to add nice energy to composite supplies, a lot the best way metal bars are used to strengthen concrete.

The most important impediment has been discovering methods to embed these supplies inside a matrix of one other materials in an orderly method. These tiny sheets and tubes have a robust tendency to clump collectively, so simply stirring them right into a batch of liquid resin earlier than it units doesn’t work in any respect. The MIT group’s perception was to find a approach to create giant numbers of layers, stacked in a wonderfully orderly method, with out having to stack every layer individually.

Though the method is extra complicated than it sounds, on the coronary heart of it’s a approach much like that used to make ultrastrong metal sword blades, in addition to the puff pastry that’s in baklava and napoleons. A layer of fabric — be it metal, dough, or graphene — is unfold out flat. Then, the fabric is doubled over on itself, pounded or rolled out, after which doubled over once more, and once more, and once more.

With every fold, the variety of layers doubles, thus producing an exponential enhance within the layering. Simply 20 easy folds would produce greater than 1,000,000 completely aligned layers.

Now, it doesn’t work out precisely that method on the nanoscale. On this analysis, quite than folding the fabric, the group reduce the entire block — itself consisting of alternating layers of graphene and the composite materials — into quarters, after which slid one quarter on high of one other, quadrupling the variety of layers, after which repeating the method. However the outcome was the identical: a uniform stack of layers, rapidly produced, and already embedded within the matrix materials, on this case polycarbonate, to type a composite.

Of their proof-of-concept checks, the MIT group produced composites with as much as 320 layers of graphene embedded in them. They had been in a position to display that regardless that the entire quantity of the graphene added to the fabric was minuscule — lower than 1/10 of a % by weight — it led to a clear-cut enchancment in total energy.

“The graphene has an successfully infinite facet ratio,” Strano says, since it’s infinitesimally skinny but can span sizes giant sufficient to be seen and dealt with. “It will probably span two dimensions of the fabric,” regardless that it’s only nanometers thick. Graphene and a handful of different identified 2-D supplies are “the one identified supplies that may do this,” he says.

The group additionally discovered a approach to make structured fibers from graphene, doubtlessly enabling the creation of yarns and materials with embedded digital features, in addition to one more class of composites. The tactic makes use of a shearing mechanism, considerably like a cheese slicer, to peel off layers of graphene in a method that causes them to roll up right into a scroll-like form, technically often known as an Archimedean spiral.

That would overcome one of many largest drawbacks of graphene and nanotubes, by way of their capacity to be woven into lengthy fibers: their excessive slipperiness. As a result of they’re so completely clean, strands slip previous one another as an alternative of sticking collectively in a bundle. And the brand new scrolled strands not solely overcome that drawback, they’re additionally extraordinarily stretchy, not like different super-strong supplies reminiscent of Kevlar. Which means they may lend themselves to being woven into protecting supplies that might “give” with out breaking.

One sudden characteristic of the brand new layered composites, Strano says, is that the graphene layers, that are extraordinarily electrically conductive, preserve their continuity all the best way throughout their composite pattern with none short-circuiting to the adjoining layers. So, for instance, merely inserting {an electrical} probe into the stack to a sure exact depth would make it doable to uniquely “handle” any one of many a whole bunch of layers. This might in the end result in new sorts of complicated multilayered electronics, he says.

This paper “describes a quite distinctive and artistic approach to make composites utilizing giant space graphene movies,” says Angelos Kyrlidis, analysis and growth supervisor for graphenes at Cabot Company who was not concerned with this work. He provides, “This work assembles the composites from chemical vapor deposition graphene, the place a really excessive facet ratio might be obtained, whereas nonetheless sustaining most of the options and properties of the only layer graphene. … It will be fairly attention-grabbing to judge in a broader vary of polymers, reminiscent of thermosets and in addition different thermoplastics.”

The analysis was supported by the U.S. Military Analysis Workplace via the Institute for Soldier Nanotechnologies at MIT.

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