Archive for the ‘materials science’ Category

Conditions like those inside Neptune cause diamond formation

August 27th, 2017

Enlarge / That lovely blue exterior could be hiding a heart of diamond. (credit: NASA)

Carbon, oxygen, and nitrogen are some of the easiest heavier elements to form through fusion. As a result, they’re common in our Solar System, typically found combined with hydrogen to make ammonia, water, and methane. In the gas and ice giants of the outer Solar System, however, these chemicals are placed under extreme pressures, where chemistry starts to get a bit weird. Do these chemicals survive the crushing interiors of these planets?

One intriguing idea is that methane doesn’t survive. As pressure and temperature increase, methane should start condensing into more complex hydrocarbons. Then, as pressures increase further, calculations indicate the hydrogen and carbon should separate out, leaving pure carbon to sink to the depths of these planets. As a result, it’s been hypothesized that, close to their core, planets like Neptune and Uranus have a layer of pure diamond.

While some evidence supporting this theory has surfaced over the years, it’s been hard to precisely replicate the temperatures and pressures found inside the planets. Now, new work done at the SLAC X-ray laser facility supports the idea that these planets are full of diamonds. But the work indicates the diamonds only form at greater depths than we’d previously thought.

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Carbon nanotube “yarn” generates electricity when stretched

August 24th, 2017

Enlarge / When the yarn is stretched, the LED lights up. (credit: AAAS/Science)

Spare energy is all around us, from the pressure exerted by every footfall to the heat given off by heavy machinery. In some cases, like regenerative braking in cars, it’s easy to harvest, and the equipment needed to do so is simple and economic. In many others, however, we’re not there yet.

It’s not that we don’t have the materials to do so. Piezoelectric generators can harvest stresses and strains, while triboelectric generators can harvest friction, to give two examples. The problem is that their efficiency is low and the cost of the materials is currently high, making them bad fits for any applications.

But a study in today’s issue of Science describes a “yarn” made of carbon nanotubes that can produce electricity when stretched. Its developers go on to demonstrate its use in everything from wearable fabrics to ocean-based wave power generators. Given that the raw material for carbon nanotubes is cheap and there are lots of people trying to bring their price down, this seems to have the potential to find some economic applications.

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New surface is so slippery, shellfish can’t get a grip

August 19th, 2017

Enlarge / A sticky situation. (credit: University of Washington)

When engineers look at mussels, they’re typically looking in awe at how they anchor themselves to nearly every surface imaginable, all while under water. The fibers they use to attach themselves are incredibly strong, and the adhesive works wet or dry on all sorts of materials. For the most part, engineers are looking to create a substance with similar properties.

This week, however, brings an exception: engineers who want to try to keep mussels from sticking to everything. Zebra mussels, a species that has invaded the Great Lakes, is estimated to cost utilities hundreds of millions of dollars each year due to clogged pipes and intakes. Ships, buoys, and pretty much anything else we put in the water also ends up needing to have mussels cleared off.

The international team behind the new work has designed a material that mussels can’t seem to get a grip on. It’s not because the mussel’s adhesive fail; instead, the mussel itself doesn’t seem to know what it’s touching when it’s set down on the material.

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Posted in adhesives, Biology, materials science, science | Comments (0)

Researchers use lasers to weld spider silk to kevlar

August 16th, 2017

Enlarge (credit: National Park Service/J Schmidt)

Spider silk has some amazing material properties, so there’s lots of enthusiasm for the prospect of using it to make something useful. Unfortunately, spiders aren’t domesticated, and attempts to make the silk proteins in other organisms haven’t been entirely successful. And then there’s the matter of what to do with silk once you have it. It doesn’t always cooperate with modern manufacturing techniques.

But some researchers in India figured out a way to get spider silk to play nicely with lasers. Under the right conditions, the silk itself helps amplify a laser’s power, to the point where it can either cut the silk in specific locations, or soften it to the point where it can be bent or welded.

The work relies on a physics effect termed “nonlinear multiphoton interactions.” In the simplest terms, the effect allows two photons of a given energy to act as a single photon of twice the energy (higher combinations are also possible). It’s a nonlinear effect, since it involves a sudden jump in energy; you don’t end up with any photons in between, at 1.5x the original energy.

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