New insights into the photochemical activity of titanium dioxide

Not so many compounds are as important to industry and medicine today as titanium dioxide (TiO2). The electronic structure of transition metal oxides is an important factor determining the chemical and optical properties of materials. Specifically for metal-oxide structures, the crystal-field interaction determines the shape and occupancy of electronic orbitals. Consequently, the crystal-field splitting and resulting unoccupied state populations can be foreseen as modeling factors of the photochemical activity. The research on titanium dioxide inaugurated the presence of IFJ PAN scientists in research programs carried out at the SOLARIS synchrotron. The measurements, co-financed by the National Science Center, were carried out at the XAS beamline.

In many chemical reactions, TiO2 appears as a catalyst. As a pigment, it occurs in plastics, paints, and cosmetics, while in medical implants, it guarantees their high biocompatibility. A group of scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow, led by Dr. Jakub Szlachetka, engaged in research on the oxidation processes of the outer layers of titanium samples and related changes in the electronic structure of this material. Scientists from the IFJ PAN conducted their latest measurements, co-financed by the National Science Center, at the XAS beamline. They analyzed how X-rays are absorbed by the surface layers of titanium samples previously produced at the Institute under carefully controlled conditions.

Read more on the SOLARIS website

Researchers capture how materials break apart following an extreme shock

Understanding how materials deform and catastrophically fail when impacted by a powerful shock is crucial in a wide range of fields, including astrophysics, materials science and aerospace engineering. But until recently, the role of voids, or tiny pores, in such a rapid process could not be determined, requiring measurements to be taken at millionths of a billionth of a second.

Now an international research team has used ultrabright X-rays to make the first observations of how these voids evolve and contribute to damage in copper following impact by an extreme shock. The team, including scientists from the University of Miami, the Department of Energy’s SLAC National Accelerator Laboratory and Argonne National Laboratory, Imperial College London and the universities of Oxford and York published their results in Science Advances.

“Whether these materials are in a satellite hit by a micrometeorite, a spacecraft entering the atmosphere at hypersonic speed or a jet engine exploding, they have to fully absorb all that energy without catastrophically failing,” says lead author James Coakley, an assistant professor of mechanical and aerospace engineering at the University of Miami. “We’re trying to understand what happens in a material during this type of extremely rapid failure. This  experiment is the first round of attempting to do that, by looking at how the material compresses and expands during deformation before it eventually breaks apart.”

Read more on the SLAC website

Image: To see how materials respond to intense stress, researchers shocked a copper sample with picosecond laser pulses and used X-ray laser pulses to track the copper’s deformation. They captured how the material’s atomic lattice first compressed and subsequently expanded,, creating pores, or voids, that grew, coalesced, and eventually fractured the material.

Credit: Greg Stewart/SLAC National Accelerator Laboratory

Investigating 3D-printed structures in real time

Scientists used ultrabright x-rays to watch the developing structure of a 3D-printed part evolve during the printing process.

A team of scientists working at the National Synchrotron Light Source II (NSLS-II) at the U.S. Department of Energy’s (DOE’s) Brookhaven National Laboratory has designed an apparatus that can take simultaneous temperature and x-ray scattering measurements of a 3D printing process in real time, and have used it to gather information that may improve finished 3D products made from a large variety of plastics. This study could broaden the scope of the printing process in the manufacturing industry and is also an important step forward for Brookhaven Lab and Stony Brook University’s collaborative advanced manufacturing program.

The researchers were studying a 3D printing method called fused filament fabrication, now better known as material extrusion. In material extrusion, filaments of a thermoplastic—a polymer that softens when heated and hardens when cooled—are melted and deposited in many thin layers to build a finished structure. This approach is often called “additive” manufacturing because the layers add up to produce the final product.

Read more on the NSLS-II website

Image: The photo shows the research team, (from front to back) Yu-Chung Lin, Miriam Rafailovich, Aniket Raut, Guillaume Freychet, Mikhail Zhernenkov, and Yuval Shmueli (not pictured), placing the 3D printer into the chamber of the Soft Matter Interfaces (SMI) beamline at Brookhaven Lab’s National Synchrotron Light Source II (NSLS-II).

Note: this photo was taken in March 2020, prior to current COVID-19 social distancing guidelines.

How new materials increase the efficiency of direct ethanol fuel cells

A group from Brazil and an HZB team have investigated a novel composite membrane for ethanol fuel cells. It consists of the polymer Nafion, in which nanoparticles of a titanium compound are embedded by the rarely explored melt extrusion process. At BESSY II they were able to observe in detail, how the nanoparticles in the Nafion matrix are distributed and how they contribute to increase proton conductivity.

Ethanol has five times higher volumetric energy density (6.7 kWh/L) than hydrogen (1.3 kWh/L) and can be used safely in fuel cells for power generation. In Brazil in particular there is great interest in better fuel cells for ethanol as all the country distributes low-cost ethanol produced in a renewable way from sugar cane. Theoretically, the efficiency of an ethanol fuel cell should be 96 percent, but in practice at the highest power density it is only 30 percent, due to a variety of reasons. So there is great room for improvements.

Nafion with nanoparticles

A team led by Dr. Bruno Matos from the Brazilian research institute IPEN is therefore investigating novel composite membranes for direct ethanol fuel cells. A promising solution is tailoring new polymer-based composite electrolyte materials to replace the state-of-the-art polymer electrolyte such as Nafion. Matos and his team use melt extrusion process to produce composite membranes based on Nafion with additional titanate nanoparticles, which have been functionalized with sulfonic acid groups.

Read more on BESSY II (at HZB) website

Image: The material consists of Nafion with embedded nanoparticles.

Credit: © B.Matos/IPEN