A shape-induced orientation phase within 3D nanocrystal solids

Designing nanocrystal (NC) materials aims at obtaining superlattices that mimic the atomic structure of crystalline solids. In such atomic systems, spatially anisotropic orbitals determine the crystalline lattice type. Similarly, in NC systems the building block anisotropy defines the order of the final solid: here, the NC shape governs the final superlattice structure. Yet, in contrast to atomic systems, NC shape-anisotropy induces not only positional, but also orientational order, ranging from full rotational disorder to a stable, fixed alignment of all NCs. This orientational relation is of special interest, as it determines to what extent atomically coherent connections between NCs are possible, thereby enabling complete wave function delocalization within the NC solid.
In addition to predicting the final NC orientation and position structure, the realization of NC materials demands a controllable fabrication process such that the designed order can be produced. Generally, such highly ordered NC superstructures are achieved through solvent evaporation induced self‐assembly on hard substrates. For applications where the 2D nature of this substrates process is limiting, nonsolvent into solvent diffusion, a technique commonly used to grow single crystals of dissolved molecules, is an attractive option. However, the precise influence of self-assembly parameters on the final superlattice outcome remains unknown. In this work, the researchers posed two closely related questions regarding the design of novel free-standing NC materials: (i) how can the NC self-assembly process be controlled to yield highly ordered free-standing supercrystals and (ii) what is the detailed positional and orientational order within the NC solid? A multidisciplinary team of collaborators, including the Austrian Small Angle X-ray Scattering (SAXS) beamline at Elettra, approached this challenge by a combined experimental and computational strategy.

>Read more on the Elettra Sincrotrone Trieste website

Image: Self‐assembly of 3D colloidal supercrystals built from faceted 20 nm Bi nanocrystals is studied by mens of in-situ synchrotron X‐ray scattering, combined with Monte Carlo simulations. 

X-rays uncover a hidden property that leads to failure in a lithium-ion battery material

Experiments at SLAC and Berkeley Lab uproot long-held assumptions and will inform future battery design.

Over the past three decades, lithium-ion batteries, rechargeable batteries that move lithium ions back and forth to charge and discharge, have enabled smaller devices that juice up faster and last longer.
Now, X-ray experiments at the Department of Energy’s SLAC National Accelerator Laboratory and Lawrence Berkeley National Laboratory have revealed that the pathways lithium ions take through a common battery material are more complex than previously thought. The results correct more than two decades worth of assumptions about the material and will help improve battery design, potentially leading to a new generation of lithium-ion batteries.

An international team of researchers, led by William Chueh, a faculty scientist at SLAC’s Stanford Institute for Materials & Energy Sciences and a Stanford materials science professor, published these findings today in Nature Materials.
“Before, it was kind of like a black box,” said Martin Bazant, a professor at the Massachusetts Institute of Technology and another leader of the study. “You could see that the material worked pretty well and certain additives seemed to help, but you couldn’t tell exactly where the lithium ions go in every step of the process. You could only try to develop a theory and work backwards from measurements. With new instruments and measurement techniques, we’re starting to have a more rigorous scientific understanding of how these things actually work.”

>Read more on the SLAC website

Image: When lithium ions flow into the battery’s solid electrode – illustrated here in hexagonal slices – the lithium can rearrange itself, causing the ions to clump together into hot spots that end up shortening the battery lifetime.
Credit: Stanford University/3Dgraphic

Ultralow-fluence for phase-change process

Ultrafast active materials with tunable properties are currently investigated for producing successful memory and data-processing devices. Among others, Phase-Change Materials (PCMs) are eligible for this purpose. They can reversibly switch between a high-conductive crystalline state (SET) and a low-conductive amorphous state (RESET), defining a binary code. The transformation is triggered by an electrical or optical pulse of different intensity and time duration. 3D Ge-Sb-Te based alloys, of different stoichiometry, are already employed in DVDs or Blu-Ray Disks, but they are expected to function also in non-volatile memories and RAM. The challenge is to demonstrate that the scalability to 2D, 1D up to 0D of the GST alloys improves the phase-change process in terms of lower power threshold and faster switching time. Nowadays, GST thin films and nanoparticles have been synthetized and have beenshown to function with competitive results.
A team of researchers from the University of Trieste and the MagneDyn beamline at Fermi demonstrated the optical switch from crystalline to amorphous state of Ge2Sb2Te5nanoparticles (GST NPs) with size <10 nm, produced via magnetron sputtering by collaborators from the University of Groeningen. Details were reported in the journal Nanoscale.
This work aims at showing the very low power limit of an optical pulse needed to amorphize crystalline Ge2Sb2Te5 nanoparticles. Particles of 7.8 nm and 10.4 nm diameter size were deposited on Mica and capped with ~200nm of PMMA. Researchers made use of a table-top Ti:Sapphire regenerative amplified system-available at the IDontKerr (IDK) laboratory (MagneDyn beamline support laboratory) to produce pump laser pulses at 400 nm, of ~100 fs and with a repetition rate from 1kHz to single shot.

>Read more on the Elettra Sincrotrone Trieste website

Image (extract): Trasmission Electron Microscopy image of the nanoparticles sample. Ultafast single-shot optical process with fs-pulse at 400 nm. Microscope images of amorphized and amorphized/ablated areas obtained on the nanoparticles sample. Comparison of amorphization threshold fluences between thin films and nanoparticles cases.
Please see here the entire image.

A closer look of zink behaviour under extreme conditions

Researchers have explored the phase diagram of zinc under high pressure and high temperature conditions, finding evidence of a change in its structural behaviour at 10 GPa. Experiments profited from the brightness of synchrotron light at ALBA and Diamond.

These results can help to understand the processes and phenomena happening in the Earth’s interior.

The field of materials science studies the properties and processes of solids to understand and discover their performances. Synchrotron light techniques permit to analyse these materials at extreme conditions (high pressure and high temperature), getting new details and a deep knowledge of them.

Studying the melting behaviours of terrestrial elements and materials at extreme conditions, researchers can understand the phenomena taking place inside them. This information is of great value for discovering how these materials react in the inner core of Earth but also for other industrial applications. Zinc is one of the most abundant elements in Earth’s crust and is used in multiple areas such as construction, ship-building or automobile.

>Read more on the ALBA website

Figure: P-T phase diagram of zinc for P<16 GPa and T<1600K. Square data points correspond to the X-ray diffraction measurements. Solid squares are used for the low pressure hexagonal phase (hcp) and empty symbols for the high pressure hexagonal phase (hcp’). White, red and black circles are melting points from previous studies reported in the literature. The triangles are melting points obtained in the present laser-heating measurements. In the onset of the figure is shown the custom-built vacuum vessel for resistively-heated membrane-type DAC used in the experiments at the ALBA Synchrotron. 

Empowering multicomponent cathode materials for sodium ion batteries

…by exploring three-dimensional compositional heterogeneities

Energy storage devices have revolutionized the modern electronics industry by enabling the widespread application of portable electronic devices. Moreover, these storage devices also have the potential to reduce the dependence on fossil fuels by implementing electric vehicles in the market. To date, lithium ion batteries have dominated the market because of the high energy density delivered by them. However, one should look into the sustenance of such devices because Li is not one of the most abundant metals on Earth’s crust. Thus, developing an alternative to lithium ion batteries has become one of the key issues to ensure the sustainable future of energy storage devices. Sodium ion batteries provide one such alternative. Out of all the components of a battery, cathode materials play one of the key roles in determining the overall performance of such batteries. Unfortunately, sodium-ion batteries have been lagging behind their lithium ion counterpart in terms of performance. Thus, new design strategies must be undertaken in order to improve the performance of cathode materials for sodium ion batteries.

>Read more on the SSRL at SLAC website

Image (extract): Three-dimensional elemental associations of pristine Na0.9Cu0.2Fe0.28Mn0.52O2 studied through transmission x-ray tomography. a) Visualizing the surface elemental associations at different angles with different colors corresponding to different association, and b) 2D cross-sectional association maps showing the bulk elemental associations. [Energy Environ. Sci., DOI: 10.1039/C8EE00309B (2018)] See entire figure here.

Topological excitations emerge from a vibrating crystal lattice

It has long been known that the properties of materials are crucially dependent on the arrangement of the atoms that make up the material. For example, atoms that are further apart will tend to vibrate more slowly and propagate sound waves more slowly. Now, researchers from Brookhaven National Laboratory have used Sector 30 at the Advanced Photon Source (APS) to discover “topological” vibrations in iron silicide (FeSi). These topological vibration arise from a special symmetrical arrangement of the atoms in FeSi and endow the atomic vibrations with novel properties such as the potential to transmit sound waves along the edge of the materials without scattering and dissipation. Looking to the future one might envisage using these modes to transfer energy or information within technological devices.

In quantum mechanics, atomic motions in crystals are described in terms of vibrational modes called phonons. Similar to electrons moving in metals, phonons can also propagate through materials. The detailed properties of these excitations determine many of the thermal, mechanical and electronic properties of the material. In 2017, part of the current collaborative team from the Chinese Academy of Science, theoretically predicted the existence of the topological phonons in transition metal monosilicides. As shown in Fig.1, these topological phonons are formed by two Dirac-cones with different slopes and are protected by symmetry. Since the mathematical description of each Dirac-cone is intimately related to the famous Weyl-equation that was originally proposed in high-energy physics, these topological phonons are consequently called double-Weyl excitations.

>Read more on the Advanced Photon Source website

Image: (extract) Schematic view of the double-Weyl phonon dispersion. Full image here.
Credit: Brookhaven National Laboratory

High-caliber research launches NSLS-II beamline into operations

Pratt & Whitney conduct the first experiments at a new National Synchrotron Light Source II beamline.

A new experimental station (beamline) has begun operations at the National Synchrotron Light Source II (NSLS-II)—a U.S. Department of Energy (DOE) Office of Science User Facility at DOE’s Brookhaven National Laboratory. Called the Beamline for Materials Measurement (BMM), it offers scientists state-of-the-art technology for using a classic synchrotron technique: x-ray absorption spectroscopy.

“There are critical questions in all areas of science that can be solved using x-ray absorption spectroscopy, from energy sciences and catalysis to geochemistry and materials science,” said Bruce Ravel, a physicist at the National Institute of Standards and Technology (NIST), which constructed and operates BMM through a partnership with NSLS-II.

X-ray absorption spectroscopy is a research technique that was developed in the 1980s and, since then, has been at the forefront of scientific discovery.

“The reason we’ve used this technique for 40 years and the reason why NIST built the BMM beamline is because it adds a great value to the scientific community,” Ravel explained.

The first group of researchers to conduct experiments at BMM came from jet engine manufacturer Pratt & Whitney. Senior Engineer Chris Pelliccione and colleagues used BMM to study the chemistry of jet engines.

>Read more on the National Synchrotron Light Source II (NSLS-II) website

Image: Pratt & Whitney Senior Engineer Chris Pelliccione (left) with NIST’s Bruce Ravel (right) at BMM’s workstation.

Understanding reaction pathways leading to MnO2 polymorph formation

Computational driven design of materials has provided guidelines for designing novel materials with desired properties, especially for metastable materials, which may have superior functionalities than its stable counterparts [1]. However, the synthesis of these metastable materials is usually challenging. The current computational approaches are not able to predict reaction pathways passing through intermediate or metastable phases. As a consequence, the synthesis of many compounds still remains Edisonian, meaning that repeated iteration is usually required to find the reaction conditions needed for synthesizing targeted materials with desired properties. To reduce the amount of cost and effort during this discovery process, a predictive theory for directing the synthesis of materials is necessary.

In the recent article “Understanding Crystallization Pathways Leading to Manganese Oxide Polymorph Formation [2]”, researchers from SLAC, LBNL, MIT, Colorado School of Mines, and NREL combined theory and experimental approaches to develop and demonstrate a theoretical framework that guides the synthesis of intermediate/metastable phases. This ab initio-computation based framework calculates the influence of particle size and solution composition on the stability of polymorph (substances having the same composition but different crystallographic structures), and predicts the phases that will appear along the different reaction pathways.

>Read more on the SSRL at SLAC website

Image (extract): (a) Size-dependent phase diagram of MnO2 polymorphs. The three arrows mark the reaction progression from nano-size to bulk at different potassium concentrations. (b-d) The evolution of x-ray scattering pattern with time along [K+] = 0 M (b), 0.2 M (c), and 0.33M (d). The identities and the fractions of the phases are marked in the subfigure to the right. (e-f) Electron beam diffraction patterns of the δ” phase and δ’ phase harvested from [K+] = 0 M and 0.2 M, respectively. See all figures here.

A designed material untangles long-standing puzzle

This approach could lead to new materials with emergent physics and unique electronic properties, supporting broader research efforts to revolutionize modern electronics.

When atoms or molecules assemble to form bulk matter, new properties (such as conductivity and ferromagnetism) that didn’t exist in the constituent parts can emerge from the whole. Similarly, stacking atomically thin layers into nanostructures (heterostructures) can give rise to a rich variety of emergent phases not found in bulk materials.

Materials that exhibit emergent phenomena (“quantum materials”) often feature multiple phases with simultaneous phase transitions. A great deal of effort is currently being expended to disentangle such transitions, to discover what drives them and to ultimately harness them in new materials with desired functionalities. Most of these efforts have relied on external perturbations (light, pressure, etc.) to decouple the transitions. In this work, researchers found a way to do this intrinsically, through layer-by-layer design of stacking sequences with mismatched periodicities.

>Read more on the Advanced Light Source website

Image: (a) Rare-earth (RE) nickelates (RENiO3) host multiple types of entangled orderings. This illustration depicts a magnetic ordering (spin directions indicated by yellow arrows) and a charge ordering (a checkerboard of two nickel oxidation states, indicated by sphere size and color) in bulk RENiO3 (RE and O atoms omitted for clarity). 
Please find the entire image here.

Research shows how to improve the bond between implants and bone

Research carried out recently at the Canadian Light Source (CLS) in Saskatoon has revealed promising information about how to build a better dental implant, one that integrates more readily with bone to reduce the risk of failure.

“There are millions of dental and orthopedic implants placed every year in North America and a certain number of them always fail, even in healthy people with healthy bone,” said Kathryn Grandfield, assistant professor in the Department of Materials Science and Engineering at McMaster University in Hamilton.

A dental implant restores function after a tooth is lost or removed. It is usually a screw shaped implant that is placed in the jaw bone and acts as the tooth roots, while an artificial tooth is placed on top. The implant portion is the artificial root that holds an artificial tooth in place.

Grandfield led a study that showed altering the surface of a titanium implant improved its connection to the surrounding bone. It is a finding that may well be applicable to other kinds of metal implants, including engineered knees and hips, and even plates used to secure bone fractures.

About three million people in North America receive dental implants annually. While the failure rate is only one to two percent, “one or two percent of three million is a lot,” she said. Orthopedic implants fail up to five per cent of the time within the first 10 years; the expected life of these devices is about 20 to 25 years, she added.

“What we’re trying to discover is why they fail, and why the implants that are successful work. Our goal is to understand the bone-implant interface in order to improve the design of implants.”

>Read more on the Canadian Light Source website

X-Ray Experiment confirms theoretical model for making new materials

By observing changes in materials as they’re being synthesized, scientists hope to learn how they form and come up with recipes for making the materials they need for next-gen energy technologies.

Over the last decade, scientists have used supercomputers and advanced simulation software to predict hundreds of new materials with exciting properties for next-generation energy technologies.

Now they need to figure out how to make them.

To predict the best recipe for making a material, they first need a better understanding of how it forms, including all the intermediate phases it goes through along the way – some of which may be useful in their own right.

Now experiments at the Department of Energy’s SLAC National Accelerator Laboratory have confirmed the predictive power of a new computational approach to materials synthesis. Researchers say that this approach, developed at the DOE’s Lawrence Berkeley National Laboratory, could streamline the creation of novel materials for solar cells, batteries and other sustainable technologies.

>Read more on the Stanford Synchrotron Radiation Lightsource at SLAC website

Image: In an experiment at SLAC, scientists loaded ingredients for making a material into a thin glass tube and used X-rays (top left) to observe the phases it went through as it was forming (shown in bubbles). The experiment verified theoretical predictions made by scientists at Berkeley Lab with the help of supercomputers (right).
Credit: Greg Stewart/SLAC National Accelerator Laboratory

Magnetization ratchet in cylindrical nanowires

A team of researchers from Materials Science Institute of Madrid (CSIC), University of Barcelona and ALBA Synchrotron reported on magnetization ratchet effect observed for the first time in cylindrical magnetic nanowires (magnetic cylinders with diameters of 120nm and lengths of over 20µm).

These nanowires are considered as building blocks for future 3D (vertical) electronic and information storage devices as well as for applications in biological sensing and medicine. The experiments have been carried out at the CIRCE beamline of the ALBA Synchrotron. The results are published in ACS Nano.

The magnetic ratchet effect, which represents a linear or rotary motion of domain walls in only one direction preventing it in the opposite one, originates in the asymmetric energy barrier or pinning sites. Up to now it has been achieved only in limited number of lithographically engineered planar nanostructures. The aim of the experiment was to design and prove the one-directional propagation of magnetic domain walls in cylindrical nanowires.

>Read more on the ALBA website

Image: (extract) Unidirectional propagation of magnetization as seen in micromagnetic simulations and XMCD-PEEM experiments. See entire image here.

Dark-field X-ray microscopy provides surprising insight on ferroelectrics

Thanks to the unique capabilities of in-situ dark-field X-ray microscopy, scientists have now been able to see the complex structures hidden deep inside ferroelectric materials. The results, published today in Nature Materials, contradict previous studies in which only the surface was studied. This revolutionary new technique will be the main feature of a new beamline for the new EBS machine currently being built at the ESRF.

“Until now we could only see the surface of the material; dark-field x-ray microscopy is like creating a window to its interior”, explains Hugh Simons, assistant professor at the Technical University of Denmark and corresponding author of the study. “It provides incredible contrast for even the subtlest structures inside these materials, giving us a much clearer picture of how they work”, he adds.

Simons, together with the team of ID06 – the beamline where the technique is being developed – studied the ferroelectric material BaTiO3, which is used every day in cars, computers and mobile phones. By imaging their internal structure at the same time as they applied an electric field on it, they could see how these internal structures behave and change dynamically.

>Read more on the European Synchrotron (ESRF) website

Image: (extract) Crosssectional dark-field x-ray microscopy maps of the embedded BaTiO3 grain. (…) the reconstructed strain map reveals the structural relationship between domain clusters. Full picture here.
Credit: H. Simons.

Brookhaven Lab scientist receives Early Career Research Program Funding

Valentina Bisogni, an associate physicist at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, has been selected by DOE’s Office of Science to receive significant research funding as part of DOE’s Early Career Research Program.

The effort, now in its ninth year, is designed to bolster the nation’s scientific workforce by providing support to exceptional researchers during the crucial early career years, when many scientists do their most formative work. Bisogni is among a total of 84 recipients selected this year after a competitive review of proposals. Thirty winners come from DOE national laboratories and 54 from U.S. universities.

“Supporting talented researchers early in their career is key to building and maintaining a skilled and effective scientific workforce for the nation. By investing in the next generation of scientific researchers, we are supporting lifelong discovery science to fuel the nation’s innovation system,” said Secretary of Energy Rick Perry. “We are proud of the accomplishments these young scientists have already made, and look forward to following their achievements in years to come.”

Each researcher will receive a grant of up to $2.5 million over five years to cover their salary and research expenses. A list of the 84 awardees, their institutions, and titles of their research projects is available on DOE’s Early Career Research Program webpage.

>Read more on the NSLS-II at Brookhaven Lab website

Image: Valentina Bisogni is shown preparing samples at NSLS-II’s Soft Inelastic X-ray Scattering beamline, where she will conduct her research funded through DOE’s Early Career Research Program.

The 2018 Julian David Baumert Ph.D. Thesis Award

Maxwell Terban received the 2018 Julian Baumert Ph.D. Thesis Award at this year’s Joint CFN and NSLS-II Users’ Meeting.

Maxwell Terban, a postdoctoral researcher at the Max-Plank Institute for Solid State Research, Stuttgart, is this year’s recipient of the Julian Baumert Ph.D. Thesis Award. Terban was selected for developing new research methods, based around a technique called pair distribution function (PDF), for extracting and analyzing structural signatures from materials. His research incorporated measurements from the now-closed National Synchrotron Light Source (NSLS) and the recently opened National Synchrotron Light Source II (NSLS-II)—a U.S. Department of Energy (DOE) Office of Science User Facility located at Brookhaven National Laboratory.

Each year, the Baumert Award is given to a researcher who has recently conducted a thesis project that included measurements at NSLS or NSLS-II. The award was established in memory of Julian David Baumert, a young Brookhaven physicist who worked on x-ray studies of soft-matter interfaces at NSLS.

Terban holds a bachelor’s degree in chemical engineering from the University of Massachusetts, Amherst, and a master’s degree in materials science and engineering from Columbia University. He graduated with a Ph.D. in materials science and engineering from Columbia University in 2018, and completed his doctoral dissertation under the guidance of Simon Billinge, a professor of materials science and engineering and applied physics and mathematics at Columbia.

>Read more on the NSLSI-II at Brookhaven National Laboratory website

Image: Maxwell Terban, a postdoctoral researcher at the Max-Plank Institute for Solid State Research, Stuttgart, is this year’s recipient of the Julian Baumert Ph.D. Thesis Award.

Molecular Anvils Trigger Chemical Reactions