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Category: materials – Page 252

A combined team of researchers from Lawrence Livermore National Laboratory in the U.S. and Atomic Weapons Establishment in the U.K. has found that rapidly compressing lead to planetary-core type pressures makes it stronger than steel. In their paper published in the journal Physical Review Letters, the group describes how they managed to compress the metal so strongly without melting it.

Defining strength in a material is difficult. Strength can refer to a material’s ability withstand bending or breaking under certain conditions. Making things even more complicated is that the strength of any given material can change under varying conditions—such as when heat or compression are applied. In this new effort, the researchers showed just how difficult it can be to nail down how strong a material is—in this case, lead.

Lead is not very strong. Pressing a fingernail against a car’s battery terminal is enough to create indentations, for example. But the researchers with this new effort report that the metal can be strengthened considerably by exerting .

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In the Marshall Islands, locals have a nickname for the Runit Dome nuclear-waste site: They call it ‘The Tomb’.

The sealed pit contains more than 3.1 million cubic feet (87,800 cubic meters) of radioactive waste, which workers buried there as part of efforts to clean hazardous debris left behind after the US military detonated nuclear bombs on the land.

From 1977 to 1980, around 4,000 US servicemen were tasked with cleaning up the former nuclear testing site of Enewetak Atoll. They scooped up the contaminated soil, along with other radioactive waste materials such as military equipment, concrete, and scrap metal.

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We could essentially control water at the coast lines with magnetism keeping it from eroding things.

Fuel-efficient ships that produce no wakes could soon be a reality thanks to computer simulations of “water cloaks” done by two researchers in the US. Yaroslav Urzhumov and Dean Culver of Duke University have shown that ions present in ocean water can be accelerated by electromagnetic waves in such a way that any turbulence created by sea-going vessels is cancelled out. Their work offers new opportunities for creating ships with greater propulsion efficiency – and could also be used to make vessels that are harder to detect.

“This cloaking idea opens a new dimension to create forces around an underwater vessel or object, which is absolutely required to achieve full wake cancellation,” says Urzhumov.

Guiding waves

Initial ideas for a water cloak were based on developing a specially designed metamaterial to coat the hulls of ships. Metamaterials are more common in optics and acoustics and comprise structures that can bend light or sound waves in ways not possible with conventional materials. In 2011, Urzhumov and colleagues hoped to develop a porous material interspersed with a complex network of miniscule pumps, to act as a metamaterial for guiding water waves. It was hoped that the system could cancel-out any turbulence caused by a moving vessel.

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Superhydrophobic materials, which are excellent at repelling water, can be extremely useful for a whole range of reasons, both obvious and not-so-obvious. They can prevent ice from building up on surfaces, make electronics waterproof, make ships more efficient or keep people from peeing in public. Now engineers have found a quirky new use for superhydrophobic materials – making “unsinkable” metals that stay floating even when punctured.

Superhydrophobic materials get their water-repelling properties by trapping air in complex surfaces. These air bubbles make it hard for water to stick, so droplets instead bounce or roll right off. But, of course, air also makes things buoyant, so the team set out to test how superhydrophobic materials could be used to make objects that float better.

The researchers used ultra-fast laser pulses to etch microscale and nanoscale patterns onto the surfaces. That traps large volumes of air, making the metals both superhydrophobic and buoyant. But the problem was that these complex surfaces would eventually wear away due to friction in the water, reducing the effectiveness of both of those properties.

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Trillions of plastic fragments are afloat at sea, which cause large “garbage patches” to form in rotating ocean currents called subtropical gyres. As a result, impacts on ocean life are increasing and affecting organisms from large mammals to bacteria at the base of the ocean food web. Despite this immense accumulation of plastics at sea, it only accounts for 1 to 2 percent of plastic debris inputs to the ocean. The fate of this missing plastic and its impact on marine life remains largely unknown.

It appears that sunlight-driven photoreactions could be an important sink of buoyant plastics at sea. Sunlight also may have a role in reducing plastics to sizes below those captured by oceanic studies. This theory could partly explain how more than 98 percent of the plastics entering the oceans go missing every year. However, direct, experimental evidence for the photochemical degradation of marine plastics remains rare.

A team of scientists from Florida Atlantic University’s Harbor Branch Oceanographic Institute, East China Normal University and Northeastern University conducted a unique study to help elucidate the mystery of missing plastic fragments at sea. Their work provides novel insight regarding the removal mechanisms and potential lifetimes of a select few microplastics.

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In superconducting materials, an electric current will flow without any resistance. There are quite a few practical applications of this phenomenon; however, many fundamental questions remain as yet unanswered. Associate Professor Justin Ye, head of the Device Physics of Complex Materials group at the University of Groningen, studied superconductivity in a double layer of molybdenum disulfide and discovered new superconducting states. The results were published in the journal Nature Nanotechnology on 4 November.

Superconductivity has been shown in monolayer crystals of, for example, molybdenum disulphide or tungsten disulfide that have a thickness of just three atoms. “In both monolayers, there is a special type of in which an protects the from external magnetic fields,” Ye explains. Normal superconductivity disappears when a large external magnetic field is applied, but this Ising superconductivity is strongly protected. Even in the strongest static magnetic field in Europe, which has a strength of 37 Tesla, the superconductivity in tungsten disulfide does not show any change. However, although it is great to have such strong protection, the next challenge is to find a way to control this protective effect, by applying an electric field.

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