Tag: metal

Diamond helps discover microscopic metallic particles in the brain

Diamond helps discover microscopic metallic particles in the brain

A UK-led international team of researchers has discovered elemental metallic copper and iron in the human brain for the first time. The team, comprised of scientists from Keele University and the University of Warwick in collaboration with the University of Texas at San Antonio (UTSA), used Diamond, and the Advanced Light Source located in California (USA) to identify elemental metallic copper and magnetic elemental iron within the amyloid plaques, chemical forms of copper and iron previously undocumented in human biology.

The study, published in Science Advances and funded by the UKRI’s Engineering and Physical Sciences Research Council, looked at amyloid plaques isolated from the brain tissue of deceased Alzheimer’s patients. Amyloid plaques, a hallmark feature of Alzheimer’s disease, act as a site of disrupted metal chemistry in the Alzheimer’s brain, and are believed by many to be integral to disease progression.

Read more on Diamond website

Image: X-ray microscope images and X-ray absorption spectra obtained from two Alzheimer’s disease plaque cores, measured at Diamond’s beamline I08. Image: Science Advances.

Credit: Science Advances.

Surface instability and chemical reactivity of ZrSiS and ZrSiSe nodal-line semimetals

Surface instability and chemical reactivity of ZrSiS and ZrSiSe nodal-line semimetals

Among topological semimetals, in nodal-line semimetals (NLSM) conduction and valence bands cross each other. In particular, in NLSM, topological constraints protect band crossings and, moreover, band touching forms nodal lines or rings. Recently, topological nodal lines have been observed in bulk ZrSiX compounds (X = S, Se, Te). In ZrSiX, a tetragonal structure is formed by the stacking of X-ZrSi-Zr-X slabs covalently bonded between each other, whose strength decreases by replacing S with Se or Te ions. This class of materials exhibits large and non-saturating magnetoresistance and ultrahigh mobility of charge carriers.
The control over surface phenomena, including oxidation, degradation, and surface reconstruction is a crucial step in order to evaluate the feasibility of the exploitation in technology of ZrSiX.
By means of X-ray photoelectron spectroscopy (XPS) carried out at the APE-HE beamline, high-resolution electron energy loss (HREELS) and density functional theory, an international team of researchers from Italy, China, Russia, Taiwan, and USA (coordinated by University of L’Aquila) has studied the evolution of ZrSiS and ZrSiSe surfaces in oxygen and ambient atmosphere.
The chemical activity of ZrSiX compounds is mainly determined by the interactions of Si layer with ZrX sublayer. Any adsorption provides distortion of the Si layer (flat in bulk). In the case of ZrSiS, the ZrS sublayer is almost the same as in bulk and therefore adsorption is unfavorable because it provides distortions of Si layer. In the case of ZrSiSe, the ZrSe sublayer is already strongly distorted (structure different from bulk), and, therefore, further distortion of Si layer by adsorption is favorable (see figure).

>Read more on the Elettra website

Image: Atomic structure of different steps of the process of the oxidation of ZrSiSe from (a-d) Zr-sites and (e-h) Si-sites. Red, light blue, black and yellow balls represent O, Zr, Se, and Si atoms, respectively. On panels (a) and (e) physical adsorption of single oxygen molecule is depicted. Panels (b) and (f) represent the situation of uniform coverage of the surfaces by molecular oxygen. In panels (c) and (g), decomposition of single oxygen molecule on the surfaces is represented. Panels (d) and (h) show total oxidation of the surfaces.

Exotic properties of iridium compounds

Exotic properties of iridium compounds

Scientists at DESY’s X-ray source PETRA III and the London Centre for Nanotechnology, at University College London, have developed a new method for examining the astonishing properties of a special class of iridium oxides known as iridates. The team of principal author Pavel Alexeev, from the Dynamics Beamline P01 at PETRA III, is presenting the procedure in the journal Scientific Reports.

Many oxides belonging to certain groups of transition metals (chemical elements with an incomplete d electron shell) are known for their exotic magnetic and electronic properties. These can be attributed qualitatively to a range of interactions between the charge of the electrons, their magnetic moment, their localization within the crystals and their atomic orbitals. The relative strengths of the various interactions determine whether an oxide is magnetic, an insulator, an electrical conductor or even a superconductor. The so-called 4d and 5d transitions metals are particularly interesting in this respect.

The properties of many of these oxides can be specifically adjusted by applying external electric or magnetic fields, or exerting pressure on the material. This makes them interesting for numerous applications in micro- and nanoelectronics, for data storage and information processing. Such behaviour is particularly pronounced in the oxides of 5d transition metals, such as tantalum, tungsten, osmium and iridium. The oxides of iridium are especially remarkable because they lose their magnetisation when subjected to pressure, and even under normal conditions develop unexpected magnetic structures. Although some of their properties have been known for quite a while, efforts to explain this behaviour are still in their infancy. This makes it all the more important to develop methods that provide detailed insights into such materials.

A particularly suitable and extremely sensitive method of studying the electronic and magnetic properties of solids is nuclear resonant scattering (NRS) using synchrotron radiation. This method uses the nuclei of the atoms of certain isotopes as local probes for the material’s properties. In view of its numerous possible applications, specialised measuring stations have been set up for this purpose on the P01 beamline at PETRA III, which are used by many scientists from all over the world every year. Among other things, the method allows the orientation of atomic magnetic moments to be determined with great accuracy. NRS therefore complements other X-ray techniques and – in contrast to neutron techniques – makes it possible to study small samples, for example when used on samples subject to high pressure.

>Read more on the PETRA III at DESY website

Image: Samples of strontium-iridium-trioxid crystals.
Credit: University College London, James Vale/Emily Hunter

Mine tailings dumped into the sea analysed with synchrotron light

Mine tailings dumped into the sea analysed with synchrotron light

The case of Portmán Bay, at the Spanish Mediterranean coast, is one of the most extreme cases in Europe causing great impact on the marine ecosystem by disposal of mine tailings.

For more than 40 years, 60 million tonnes of mine waste were dumped directly into the sea, resulting from the open pit mining that took place in Sierra Minera in Cartagena. As a consequence, the Bay was literally filled with metal-rich artificial soil. Since 2014, a research group from the University of Barcelona (UB) has been studying Portmán Bay. Now, they have analysed samples of these sediments at ALBA because with synchrotron light they can obtain unprecedented information about the heavy metals contamination, such as arsenic.

Very few people know about Portmán Bay, where took place one of the most extreme cases of coastal ecological impact by mine activity in Europe. Figures speak for itself: the mining company Peñarroya dumped more than 60 million tonnes of mine waste into the sea through a 2km-long pipeline located at the west part of the bay. Over the years, the bay became totally filled with a mountain of artificial sediment. The shoreline moved 600m seaward and the trace of the pollution reached 12km out to sea.

>Read more on the ALBA website

Image: Miquel Canals putting sample supports, which were specifically designed and printed with 3D technology at ALBA, at the CLAESS beamline to be analysed with synchrotron light; with Carlo Marini, beamline scientist and Andrea Baza, PhD student from UB.

Copper mobilization and immobilization

Copper mobilization and immobilization

… along an organic matter and redox gradient- insights from a mofette site.

The metal copper (Cu) is known to be an essential trace element for many organisms but it is also considered a severe contaminant at higher concentrations. Especially in soils with changing redox conditions, Cu binding mechanisms and, thus, Cu mobility are hard to predict. The metal is known to have a high affinity to soil organic matter (SOM), i.e., it can either be sequestered by adsorption to solid-phase organic matter or mobilized by complexation with dissolved organic matter. Under reducing conditions, Cu(II) can also be reduced to Cu(I) via biotic and abiotic processes and precipitate in the form of sulfidic minerals.
>Read more on the SSRL website
Image: Picture of the investigated mofette site (left) and Cu sorption isotherms determined for mofette, transitions, and reference soil in a Cu spike experiment (right).
Credit: Reprinted with permission from Mehlhorn et al. 2018, ES&T, DOI: 10.1021/acs.est.8b02668, Copyright 2018 American Chemical Society

Visualising shared-ligand intermediates of metal exchange

Visualising shared-ligand intermediates of metal exchange

Visualized by Rapid Freeze Quench and Selenium EXAFS of Se-Labeled Metallochaperones. A Paradigm for Studying Copper-Mediated Host-Pathogen Interactions.

Mammalian hosts defend against invading pathogens via the import of toxic concentrations of copper into the phagolysosome. To combat this host-defense strategy, gram negative pathogens respond via sophisticated copper export systems which are able to neutralize the copper onslaught2. Chemical mechanisms of metal exchange between protein components of metal exporters are thus important factors in understanding pathogenic virulence and are believed to occur via formation of intermediates in which the metal is coordinated by ligands derived from each partner.  However, since these ligand sets are often similar (or even identical), following the kinetics of transfer has been challenging, and has required the development of sophisticated spectroscopic approaches.

>Read more on the SSRL website

Image: Middle: Se EXAFS Fourier transforms at increasing time points for the reaction of SeM-labeled apo-CusF with unlabeled Cu(I)-loaded CusB.  Left and right: in silico models of the proposed protein-protein interface and shared-ligand intermediate.

Intermittent plasticity in individual grains

Intermittent plasticity in individual grains

A study using high energy x-ray diffraction.

Understanding the behavior of metals undergoing deformation is critical to design for fuel efficiency, performance and safety/crashworthiness. Traditional engineering analysis treats metal deformation as a smooth motion, like a fluid, when in reality the flow is intermittent at finer length scales. Use of a new detector enabled the study of these intermittent bursts of deformation at the scale of individual crystals in a loaded test sample.
A metal component is polycrystalline, composed of many crystals or grains. At the scale of millimeters, the deformation of a metal appears to proceed smoothly, whereas at the microscopic scale the underlying processes occurring in individual grains proceed in fits and starts. In this collaboration between researchers at Cornell University, the University of Illinois at Urbana-Champaign, the Air Force Research Laboratory and the Advanced Photon Source of Argonne National Laboratory, a high-speed detector was used to study these microscale deformation bursts in a grain-by-grain manner.

>Read more on the CHESS website

Image: The MM-PAD is shown with the vacuum cover and x-ray window removed. The 2×3 arrangement of detector modules are the brownish squares in the center.  Each module consists of 128×128 square pixels, where each pixel is 150µm of a side. Each module is roughly 2 cm x 2 cm in size. There is a 5 pixel wide (0.75 mm) inactive area between adjacent modules. (This photo is of an MM-PAD with Si, instead of CdTe sensors; otherwise, the two types of MM-PADs look identical.)

Transition metal complexes: mixed works better

Transition metal complexes: mixed works better

A team at BESSY II has investigated how various iron-complex compounds process energy from incident light. They were able to show why certain compounds have the potential to convert light into electrical energy. 

The results are important for the development of organic solar cells. The study has now been published in the journal PCCP, and its illustration selected for the cover.
Transition-metal complexes – that is a cumbersome word for a class of molecules with important properties: An element from the group of transition metals sits in the centre. The outer electrons of the transition-metal atom are located in cloverleaf-like extended d-orbitals that can be easily influenced by external excitation. Some transition-metal complexes act as catalysts to accelerate certain chemical reactions, and others can even convert sunlight into electricity. The well-known dye solar cell developed by Michael Graetzel (EPFL) in the 1990s is based on a ruthenium complex.

Why not Iron?
However, it has not yet been possible to replace the rare and expensive transition metal ruthenium with a less expensive element, such as iron. This is astonishing, because the same number of electrons is found on extended outer d-orbitals of iron. However, excitation with light from the visible region does not release long-lived charge carriers in most of the iron complex compounds investigated so far.

>Read more on the Bessy II at HZB website

Image: The illustration shows a molecule with an iron atom at its centre, bound to 4 CN groups and a bipyridine molecule. The highest occupied iron orbital is shown as a green-red cloud. As soon as a cyan group is present, the outer iron orbitals are observed to delocalize so that electrons are also densely present around the nitrogen atoms.
Credit: T. Splettstoesser/HZB

Defense spending bill extends Air Force research partnership

Defense spending bill extends Air Force research partnership

For the past 10 years, the U.S. Air Force has funded research on high-performance materials at the Cornell High Energy Synchrotron Source (CHESS).

The partnership has resulted in numerous advances, including a greater understanding of metal fatigue and analysis of the best metals for aircraft.
This partnership was extended with $8 million in funding to CHESS as part of the fiscal year 2019 defense appropriations bill, a $674.4 billion package that President Donald Trump signed into law Oct. 1. The bill passed both the U.S. Senate – supported by New York Sens. Charles Schumer, who is Senate minority leader, and Kirsten Gillibrand – and the U.S. House of Representatives late last month.

“Cornell University is deeply grateful to Leader Schumer and Senator Gillibrand for securing $8 million in additional funding for CHESS,” Cornell President Martha E. Pollack said in a statement. “Maintaining our scientific infrastructure is essential if the U.S. is to keep its competitive advantage in research and development. Over the years, taxpayers have invested more than $1 billion in CHESS, an investment that’s paid off many times over in new discoveries, breakthrough technologies, [science, technology, engineering, math] education and workforce development.”

Image: Matthew Miller, right, associate director of the Cornell High Energy Synchrotron Source (CHESS), watches graduate student Mark Obstalecki prepare a sample for analysis in the F2 hutch at CHESS.

Insulator metal transition at the nanoscale

Insulator metal transition at the nanoscale

An international team of researchers has been able to probe the insulator-conductor phase transition of materials at the nanoscale resolution. This is one of the first results of MaReS endstation of BOREAS beamline.

Controlling the flow of electrons within circuits is how electronic devices work. This is achieved through the appropriate choice of materials. Metals allow electrons to flow freely and insulators prevent conduction. In general, the electrical properties of a material are determined when the material is fabricated and cannot be changed afterwards without changing the material. However, there are materials that can exhibit metal or insulator behaviour depending on their temperature. Being able switch their properties, these materials could lead to a new generation of electronic devices.

Vanadium Dioxide (VO2) is one such material. It can switch from an insulating phase to a metallic phase just above room temperature, a feature exploited already for sensors. However, the reason why the properties of this material change so dramatically has been a matter of scientific debate for over 50 years.

One of the challenges in understanding why and how this switch occurs is due to a process called phase separation. The insulator-metal phase transition is similar to the ice to liquid transition in water. When ice melts, both liquid and solid water can coexist in separate regions. Similarly, in VO2, insulating and metallic regions of the material can be coexisting at the same time during the transition. But unlike water, where the different regions are often large enough to see with the naked eye, in VO2 this separation occurs on the nanoscale and it is thus challenging to observe. As a result, it has been hard to know if the true properties of each phase, or the mixture of both phases, are being measured.

>Read more on the ALBA Synchrotron website

Image: (extract, original here) reconstructed holograms at the vanadium and oxygen edges (518, 529, and 530.5 eV) used to encode the intensities of the three color channels of an RGB (red, green, blue) image. At 330 K, an increase in intensity of the green channel, which probes the metallic rutile phase (R) through the d∥ state, is observed in small regions. As the sample is heated further, it becomes increasingly clear that the blue channel, which probes a intermediate insulating M2 phase, also changes but in different regions. At 334 K, three distinct regions can be observed corresponding to the insulating monoclinic M1, M2, and metallic R phases. As the temperature increases, the R phase dominates. The circular field of view is 2 μm in diameter. (taken from Vidas et al, Nanoletters, 2018).

Tungsten accumulation in bone raises health concerns

Tungsten accumulation in bone raises health concerns

McGill University scientists have identified exposure to tungsten as problematic after they determined how and where high levels of the metal accumulate and remain in bone.

“Our research provides further evidence against the long-standing perception that tungsten is inert and non-toxic,” said Cassidy VanderSchee, a PhD student and a member of a McGill research group headed by chemistry professor Scott Bohle.

Tungsten is a hard metal with a high melting point and, when combined with other metals and used as an alloy, it’s also very flexible.

Because of these properties and under the assumption that tungsten is non-toxic, it has been tested for use in medical implants, including arterial stents and hip replacements, in radiation shields to protect tissue during radiation therapy, and in some drugs. Tungsten is found in ammunition as well as in tools used for machining and cutting other metals.

Tungsten also occurs naturally in groundwater where deposits of the mineral are found. Exposure to high levels of tungsten in drinking water in Fallon, Nevada, was investigated for a possible link with childhood leukemia in the early 2000s. This investigation lead scientists to question the long-held belief that exposure to tungsten is safe and prompted the Centers for Disease Control and Prevention in the U.S. to nominate tungsten for toxicology and carcinogenesis studies.

>Read more on the Canadian Light Source website

Image: Cassidy VenderSchee

Edges and corners increase efficiency of catalytic converters

Edges and corners increase efficiency of catalytic converters

X-rays reveal oxide islands on noble metal nanoparticles

Catalytic converters for cleaning exhaust emissions are more efficient when they use nanoparticles with many edges. This is one of the findings of a study carried out at DESY’s X-ray source PETRA III. A team of scientists from the DESY NanoLab watched live as noxious carbon monoxide (CO) was converted into common carbon dioxide (CO2) on the surface of noble metal nanoparticles like those used in catalytic converters of cars. The scientists are presenting their findings in the journal Physical Review Letters. Their results suggest that having a large number of edges increases the efficiency of catalytic reactions, as the different facets of the nanoparticles are often covered by growing islands of a nano oxide, finally rendering these facets inactive. At the edges, the oxide islands cannot connect, leaving active sites for the catalytic reaction and an efficient oxygen supply.
Catalytic converters usually use nanoparticles because these have a far greater surface area for a given amount of the material, on which the catalytic reaction can take place. For the study presented here, the scientists at DESY’s NanoLab grew platinum-rhodium nanoparticles on a substrate in such a way that virtually all the particles were aligned in the same direction and had the same shape of truncated octahedrons (octahedrons resemble double pyramids). The scientists then studied the catalytic properties of this sample under the typical working conditions of an automotive catalytic converter, with different gaseous compositions in a reaction chamber that was exposed to intense X-rays from PETRA III on the P09 beamline.

>Read more on the PETRA III at DESY website

Image: With increasing oxygen (red) concentration, an oxide sandwich forms on the surface of the metallic nanoparticles, inhibiting the desired reaction of carbon monoxide to carbon dioxide. At the edges, however, the oxide sandwich brakes up, leaving free active sites for catalysis. The more edges the nanoparticles posses, the more efficient will the catalytic converter work.
Credit: DESY, Lucid Berlin

Stressing over new materials

Stressing over new materials

Titanium is a workhorse metal of the modern age. Alloyed with small amounts of aluminum and vanadium, it is used in aircraft, premium sports equipment, race cars, space craft, high-end bicycles, and medical devices because of its light weight, ability to withstand extreme temperatures, and excellent corrosion resistance. But titanium is also expensive. Metallurgists would love to understand exactly what makes it so strong so that they could design other materials with similarly desirable properties out of more common, less expensive elements. Now, researchers utilizing the U.S. Department of Energy’s Advanced Photon Source (APS) have used high-intensity x-rays to show how titanium alloy responds to stress in its (until now) hidden interior. Eventually, the researchers believe they will be able to predict how strong a titanium part such as an aircraft engine will be, just by knowing how the crystals are arranged inside of it. And materials scientists may be able to use such a computational model to swap in atoms from different metals to see how their crystalline structures compare to that of titanium.

>Read more on the Advanced Photon Source website

Figure: (extract) (A) A computational model of crystals inside a block of titanium, (B) includes effects noticed during the experiment to place permanent deformations (the darkened areas,) [not visible here, entire picture here]  while (C) models permanent deformations without incorporating the diversity of load seen in the experiment.

How metal 3-D printing can avoid producing flawed parts

How metal 3-D printing can avoid producing flawed parts

The goal of these X-ray studies is to find ways to improve manufacturing of specialized metal parts for the aerospace, aircraft, automotive and healthcare industries.

Scientists at the Department of Energy’s SLAC National Accelerator Laboratory are using X-ray light to observe and understand how the process of making metal parts using three-dimensional (3-D) printing can leave flaws in the finished product – and discover how those flaws can be prevented. The studies aim to help manufacturers build more reliable parts on the spot – whether in a factory, on a ship or plane, or even remotely in space – and do it more efficiently, without needing to store thousands of extra parts.

The work is taking place at the lab’s Stanford Synchrotron Radiation Lightsource (SSRL) in collaboration with scientists from the DOE’s Lawrence Livermore National Laboratory and Ames Laboratory.

The 3-D printing process, also known as additive manufacturing, builds solid, three-dimensional objects from a computer model by adding material layer by layer. The use of plastics and polymers in 3-D printing has advanced rapidly, but 3-D printing with metals for industrial purposes has been more challenging to sort out.

“With 3-D printing, you can make parts with very complex geometries that are not accessible for casting like regular metal parts,” says SLAC staff scientist Johanna Nelson Weker, who is leading the project. “Theoretically, it can be a quick turnaround – simply design, send, print from a remote location. But we’re not there yet. We still need to figure out all of the parameters involved in making solid, strong parts.”

>Read more on the Stanford Synchrotron Radiation Lightsource website

Image: SLAC staff scientist Johanna Nelson Weker, front, leads a study on metal 3-D printing at SLAC’s Stanford Synchrotron Radiation Lightsource with researchers Andrew Kiss and Nick Calta, back.
Credit: Dawn Harmer/SLAC