Gizmorama - June 7, 2017

Good Morning,

Are you ready to use hydrogen fuel? Researchers believe it's how things will run in the future, and new technology has given this possibility a dramatic push forward.

Learn about this and more interesting stories from the scientific community in today's issue.

Until Next Time,
Erin

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* Toy cars, scaling model helps scientists understand how tires drive over sand *
Thanks to a new scaling law, scientists can study the physics of tires traveling across sand by analyzing toy car models.

Researchers used scaling laws to study air flow across airplane wings, testing miniature jets in wind tunnels, but this is the first time scaling laws have been developed for studying sand as a transportation medium.

The findings -- published in the journal Physical Review E -- could help engineers design superior bulldozers and tanks, or even a more efficient Mars rover.

"I'm excited that this could be a new tool we can use to design rovers for Mars," Ken Kamrin, an associate professor of mechanical engineering at MIT, said in a news release. "If we had a simulant of Martian soil in the lab, we could do experiments with a wheel shape that we want to test, and then use this scaling law to, with more accuracy, be able to tell you if that wheel would get stuck on Mars."

To scale air flow models, physicists look to scaleable equations that describe how air behaves -- specifically how it acts on an air foil at varying speeds. Similarly, researchers at MIT focused on arithmetic describing granular flow. The resistive force theory includes several equations that describe the resistive force acted on a moving object by a granular medium.

"RFT is not going to predict how sand moves or distributes stress," Kamrin said. "Its sole purpose is to tell how much force is needed to move an object of an arbitrary shape, in a certain direction, through sand."

Kamrin and his colleagues simplified RFT equations by removing dimensions, or units, from the inputs, allowing them to create a scaling law from the theory.

"For example, 'meters' is not a natural length -- it's something we invented," Kamrin said. "If we get rid of all these units, we will be left with the meat, some truth to the system."

To test their scaling law, researchers 3D-printed a large and small version of two wheel shapes, lug and cylindrical, and drove them across a bed of sand in the lab. Lug wheels are designed to dig out pockets of sand as they drive, preventing slippage, while cylindrical wheels move more smoothly across the sands surface, preventing sinkage.

Researchers tested the different wheels at various speeds and under various amounts of weight, and then used their scaling law to see if the miniature models could be used to predict the performance of the larger models.

"Our data followed the predictions," Kamrin said. "The small tests predicted the big tests, to a quantitative degree. We validated many times over the accuracy of the scaling law."



* Water-splitting technologies could usher in hydrogen economy *
Researchers at Penn State University have developed a new, cheaper and more efficient way to split water molecule and produce pure hydrogen fuel.

Hydrogen has been promised as the remedy for the world's addiction to fossil fuels. But the fuel isn't cheap or easy to make -- at least not cheap enough to make it an economical substitute for traditional oil and gas fuels.

In addition to being relatively expensive, current methods for hydrogen production are energy intensive and yield unwanted byproducts.

Most industrial hydrogen is made by steam reforming methane. Unfortunately, the production process releases carbon dioxide into the atmosphere, limiting its environmental advantages. Other methods rely on waste heat from alternative energy sources, like solar arrays and nuclear power plants. These methods are more eco-friendly but they're not easily scaled. Some industrial hydrogen is made from water molecules split by a platinum catalyst, but platinum is prohibitively expensive.

Scientists at Penn State set out to find a cheaper catalyst to trigger the water-splitting chemical reactions needed to produce hydrogen. According to a new study published in the journal ACS Nano, they've found one.

The promising new catalyst is an altered form of molybdenum disulfide.

"Molybdenum disulfide has been predicted as a possible replacement for platinum, because the Gibbs free energy for hydrogen absorption is close to zero," Mauricio Terrones, a professor of physics, materials science, engineering and chemistry at Penn State, said in a news release.

But molybdenum disulfide is a semiconductor and doesn't conduct electrons efficiently. Researchers amended the material with reduced graphene oxide, an extremely conductive form of carbon. The addition of tungsten made the molybdenum disulfide even more efficient at hydrogen absorption.

Researchers created their new low-energy water splitting catalyst by alternative thin layers of graphene and tungsten-molybdenum disulfide. The catalyst is submerged in a water solution and a small electric current is delivered by an electrode. The catalyst pulls protons from the water, forming a hydrogen bubble that migrates to the surface and is released.

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