Lenses Provide Nano Scale X-ray Microscopy

Scientists at DESY (Germany) have developed novel lenses that enable X-ray microscopy with record resolution in the nanometre regime. Using new materials, the research team led by DESY scientist Saša Bajt from the Center for Free-Electron Laser Science (CFEL) has perfected the design of specialised X-ray optics and achieved a focus spot size with a diameter of less than ten nanometres. A nanometre is a millionths of a millimetre and is smaller than most virus particles. They successfully used their lenses to image samples of marine plankton.

Modern particle accelerators provide ultra-bright and high-quality X-ray beams. The short wavelength and the penetrating nature of X-rays are ideal for the microscopic investigation of complex materials. However, taking full advantage of these properties requires highly efficient and almost perfect optics in the X-ray regime. Despite extensive efforts worldwide this turned out to be more difficult than expected, and achieving an X-ray microscope that can resolve features smaller than 10 nm is still a big challenge.

 

The silica shell of the diatom Actinoptychus senarius, measuring only 0.1 mm across, is revealed in fine detail in this X-ray hologram recorded at 5000-fold magnification with the new lenses. The lenses focused an X-ray beam to a spot of approximately eight nanometres diameter – smaller than a single virus – which then expanded to illuminate the diatom and form the hologram

The new lenses consist of over 10 000 alternating layers of a new material combination, tungsten carbide and silicon carbide. “The selection of the right material pair was critical for the success,” emphasises Bajt. “It does not exclude other material combinations but it is definitely the best we know now.” The resolution of the new lenses is about five times better than achievable with typical state-of-the-art lenses.

We produced the world’s smallest X-ray focus using high efficiency lenses,” says Bajt. The new lenses have an efficiency of more than 80 per cent. This high efficiency is achieved with the layered structures that make up the lens and which act like an artificial crystal to diffract X-rays in a controlled way.

The researchers have reported their work in the journal Light: Science and Applications.

Source: http://www.desy.de/

More Durable Fuel Cells For Hydrogen Electric Car

Take a ride on the University of Delaware’s (UDFuel Cell bus, and you see that fuel cells can power vehicles in an eco-friendly way. In just the last two years, Toyota, BMW and Honda have released vehicles that run on fuel cells, and carmakers such as GM, BMW and VW are working on prototypes.  If their power sources lasted longer and cost less, fuel cell vehicles could go mainstream faster. Now, a team of engineers at UD has developed a technology that could make fuel cells cheaper and more durable.

Hydrogen-powered fuel cells are a green alternative to internal combustion engines because they produce power through electrochemical reactions, leaving no pollution behind. Materials called catalysts spur these electrochemical reactions. Platinum is the most common catalyst in the type of fuel cells used in vehicles. However, platinum is expensive — as anyone who’s shopped for jewelry knows. The metal costs around $30,000 per kilogram. Instead, the UD team made a catalyst of tungsten carbide, which goes for around $150 per kilogram. They produced tungsten carbide nanoparticles in a novel way, much smaller and more scalable than previous methods.

The material is typically made at very high temperatures, about 1,500 Celsius, and at these temperatures, it grows big and has little surface area for chemistry to take place on,” explains Vlachos, professor at the Catalysis Center for Energy Innovation (UD). “Our approach is one of the first to make nanoscale material of high surface area that can be commercially relevant for catalysis.”

The researchers made tungsten carbide nanoparticles using a series of steps including hydrothermal treatment, separation, reduction, carburization and more. The results are described in a paper published in Nature Communications.

Source: https://www.udel.edu/