Innovation in Materials Characterization Award

Stig Helveg, Haldor Topsoe A/S

Electron Microscopy Advances in Catalysis

Written by Prachi Patel

Stig Helveg set the stage for his talk by emphasizing the importance of catalysis for a sustainable future. Catalysis is the backbone of chemical reactions to produce fertilizers, chemicals, and fuels. It will be critical for increasing food supply, reducing air pollutant emissions, and for harnessing renewable energy.

“It’s a field we cannot live without today and also, of course, tomorrow,” he said, before delving into the goal and the promise of his pioneering work on atomic-scale transmission electron microscopy under working reaction conditions to deepen the understanding of catalysis and advance catalyst research.

Helveg first highlighted how recent advances in electron microscopy have been able to address challenges in catalyst research. With tremendous advances in electron microscopy over the past 10 years, scientists can now observe materials at the atomic scale. Helveg and his colleagues, for example, published an article in 2014 showing how they were able to resolve the sites of single cobalt atoms in a Co‐Mo‐S catalyst that is used in desulfurization processes at oil refineries by analyzing the material at the single‐atom level. “There has been a debate for decades where Co atoms lie,” he said. “This really shows the power of electron microscopy.”

His work has been devoted to harnessing this power for insights into nanostructured catalysts. Researchers have in recent years focused on developing nanocatalysts given their abundant sites for catalysis, and to increase the activity of those sites by sculpturing and composing them. The challenge is that nanostructures are very sensitive to changes in their surroundings, he said. Chemical reactions can alter their surface, morphology, phase, and make them clump together or break apart. Understanding what happens to catalysts at the nanoscale under industrial chemical reaction conditions is critical to improve catalysis, and has driven his research at Haldor Topsoe A/S, Helveg said.

“Introducing reaction conditions into a microscope is really like mixing fat and water,” he said. Microscopes are high-vacuum machines that work at room temperature, while chemical plants work at high pressures and temperatures. Nonetheless, he and others have developed technologies such as aperture gas cells that have allowed performing reaction conditions from an industrial plant in a microscope. These tools have yielded key insight into several phenomena in catalysts, such as generation of active sites, restructuring, and compositional changes. Helveg offered a more detailed look on two case studies that illustrate the practical application of these techniques.

In one, they used high-resolution TEM to study vanadium oxide supported on titanium dioxide, which is a catalyst for removing nitrogen oxide emissions. They found that the vanadium oxide (001) facets oscillate between a clean edge and a smeared edge as the researchers switched between oxidizing and reducing conditions. Using this information on the catalyst system, Helveg is now working with researchers at Aarhus University and Innovation Fund of Denmark to create a better NOx reduction catalyst.

Another case study involves the use of a specialized window cell that the Haldor Topsoe A/S team developed with researchers at TU Delft and ThermoFisher Scientific. The cell is a tiny gas flow channel made with two 1-µm-thick silicon nitride membranes separated by 5-µm-tall pillars. Windows that are just 15-nm wide act like a nanoreactor, allowing atomic-resolution imaging of sub-nanoliter volumes of catalyst at ambient pressures of up to 14 bar and elevated temperatures of 660°C.

This device helped the research group elucidate previously unseen phenomenon during the oxidation of carbon monoxide by platinum. Many catalytic reactions oscillate, and it has been known for decades that this is because of dynamic changes to the catalyst surface. But no one had observed these changes in nanoparticle catalysts. Using their nanoreactor, Helveg and his colleagues saw that the nanocrystals undergo reversible refacetting, going back and forth between a rounded shape to a more pointed shape as the reaction oscillates.

To sum up, Helveg stressed how advances in electron microscopy have allowed the study of nanoparticle dynamics under meaningful catalytic conditions, and how he and his colleagues have linked their observations to functional analysis. Going forward, he appeals to those in the electron microscopy field to look into two critical issues: improving the understanding of the right electron dose for a chemically relevant signal, and understanding the mass-temperature distribution inside commercial reactor devices. “The future certainly looks very bright from where we are,” he concluded.

The Innovation in Materials Characterization Award honors an outstanding advance in materials characterization that notably increases knowledge of the structure, composition, in situ behavior under outside stimulus, electronic behavior, or other characterization feature, of materials. It is not limited to the method of characterization or the class of materials observed.

Helveg’s award citation is “for pioneering atomic-scale transmission electron microscopy under reactive gas environments, leading to groundbreaking insights in catalysis, crystal growth and corrosion.”

The Innovation in Materials Characterization Award has been endowed by Dr. Gwo-Ching Wang and Dr. Toh-Ming Lu.

Best Poster Award Winners – Wednesday

 

Jinghan Wang, Key Laboratory for Special Functional Materials of the Ministry of Education

QN08.08.13

Fabrication of Porphyrin Assemblies and Biological Applications

 

Pan Xia, University of California, Riverside

EP02.05.06

Controlling the Surface Chemistry of Quantum Confined Silicon Nanoparticles for NIR to Visible Upconversion

 

Michael Wang, University of Michigan

ES04.05.03

Mixed Electronic and Ionic Conduction Properties of Reduced Lithium Lanthanum Titanate

 

Ashley Gaulding, National Renewable Energy Laboratory

ES15.10.11|ES15.09.05

Spotlight Talk—Conductivity Tuning via Doping with Electron Donating and Withdrawing Molecules in Perovskite CsPbI3 Nanocrystal Films

Open Data Challenge Awards Announced!

1^st place

Battery Cycling During Extreme Fast Charging
P Attia, N Jin (Stanford University)

2^nd place

Deep Generative Models for Creating Synthetic Microstructures
V Shah et al. (Iowa State University)

3^rd place

Deep Spatial Fingerprint Neural Network Interatomic Potential Development
Z Shi, Wujie Wang (Massachusetts Institute of Technology)

Sponsored by  CITRINE Informatics

MRS “Outstanding Young Investigator Award” winner Sheng Xu discusses his award talk

Sheng Xu, University of California, San Diego, was awarded the MRS Outstanding Young Investigator Award “for materials and device designs in biointegrated electronics and stretchable energy systems."

 

MRS TV presents new broadcasts each day during the Meeting.  View it on monitors throughout the convention center, online at mrs.org/spring2019, and in the following hotels:

• Sheraton Phoenix – channel 89
• Hyatt Regency – channel 58
• Renaissance Phoenix – TV in lobby

Best Poster Award Winners – Tuesday

Jae Man Shin, Korea Advanced Institute of Science and Technology

CP04.04.07

Generation of Shape-Tuned, Monodisperse Block Copolymer Particles Through Particle Restructuring by Solvent Engineering

 

Diego Oyarzun, Stanford University

ES09.04.11

Theory and Experimental Validation of Selective Removal of Nitrate Using Capacitive Deionization with Surface Functionalization

 

Subash Gireesan, TU Eindhoven, Center for Computational Energy Research

QN04.04.33

Diffusive to Ballistic Heat Flow Transition in GaP Nanowires

 

Junsik Mun, Seoul National University

QN07.04.08

Relaxational Ferroelectricity of (111)-BaTiO₃ Epitaxial Films

 

Riddha Das, University of Massachusetts Amherst

SM05.03.05

Spatially Controlled Bioorthogonal Catalysis for Imaging and Drug Delivery

 

 

MRS/Sociedad Mexicana de Materiales Student Poster Award Exchange Program

Manuel Ceballos, Unidad Monterrey

Growth of Silver Dendritic Nanostructures Decorated with Gold Nanospheres and their Application as Sers Substrate

Written by Gargi Joshi

This presentation won one out of the three Poster awards during the XXVII International Materials Research Congress held last year. Manuel Ceballos talked about the surface-enhanced Raman spectroscopy (SERS) as a very powerful tool capable of providing lower limits of elemental detection regardless of the presence of interferences, enabling a range of materials to be analyzed. Noble metals like gold (Au) are used as coatings due to their inherent optical property of surface plasmon resonance. The work studied electrodeposited silver on preferably aluminum sheet as a substrate using silver nitrate solution. Next, the silver nanostructures were coated with gold nanospheres using the electrophoretic deposition. Detection of an ultralow value of 1 ppb analyte concentration demonstrated the advantage of this technique along with it being quick, affordable, and - most importantly - reproducible.

The other poster presenters were Kevin Fitzwell of the University of California, Los Angeles on Design of Galfenol/permalloy Nanolaminates for Incorporation Into a Strain-mediated Nanoscale Antenna and Arlet Ariadne Rodríguez of Instituto Politécnico Nacional – Ipn on Effect of Modification of the Surface of Mesoporous Silica in the Adsorption-desorption of Griseofulvine

Plenary Session Featuring The Fred Kavli Distinguished Lecture in Materials Science

Helena Van Swygenhoven, Paul Scherrer Institute and École Polytechnique Fédérale de Lausanne

Synchrotron Light to Investigate Materials in Operando

Written by Arthur L. Robinson

In operando refers to investigating in real time materials processes under conditions identical to, or at least close to, those expected to be encountered by the material during its service life. The more general term in situ relaxes the requirement for realistic operating conditions. Considering that the use of synchrotron light requires a relatively compact experimental station capable of reproducing these operating conditions at the synchrotron light source, one might be surprised that the scope of the title of Helena Van Swygenhoven’s Fred Kavli Distinguished Lectureship in Materials Science presentation is already too vast to cover even in broad brush strokes. Accordingly, Van Swygenhoven explained that she was narrowing her talk to four applications, mostly in materials manufacturing.

In a brief review, she summarized the general kinds of measurements possible when a material is illuminated by synchrotron light, divided into elastic scattering (imaging, small-angle scattering to study particles in the sample, and diffraction to identify the phases present) and inelastic scattering, such as x-ray fluorescence to map the chemical constituents. She emphasized that if it is the brightness of synchrotron light that makes many of these measurements possible, the requirement to record the data with the resolution needed and in a timely manner makes advanced detectors just as important. She cited photon-counting strip and pixel detectors developed at the Paul Scherrer Institute, home of the Swiss Light Source, with frame rates up to 40 kHz and 22 kHz, respectively, as examples. While the number of synchrotron light sources around the world is now so large that most researchers can find one relatively close by, so far only a few are equipped with experimental stations able to conduct in operando experiments relevant to manufacturing.

Moving into the meat of her presentation, Van Swygenhoven took a metallurgical process as the first of her four examples. Specifically, she described in operando investigations of additive manufacturing by selected laser melting. One begins with a bed of powder and scans the laser in a pattern across the powder, locally melting the powder, which then solidifies. Repeating this process layer by layer builds up the net-shape object desired. Important variables are the laser (power, spot size, and wavelength), the powder (size, morphology, and thickness), and the scanning process (speed, hatch spacing, and scan strategy). Experiments of this type have been conducted at the Stanford Synchrotron Radiation Lightsource, the Advanced Photon Source, and the Diamond Light Source, and a new experiment chamber with an ultrafast detector for selected laser melting has been installed at the Swiss Light Source. Experiments on a Ti₆Al₄V alloy of interest to the Swiss watch industry have demonstrated the importance of the scan pattern in determining the cooling rate as the laser spot passes and hence the resulting microstructure. Studies of laser-based processing of aluminum-oxide parts have also been undertaken.

For her second example, Van Swygenhoven chose mechanosynthesis of hybrid organic–inorganic iodides. Milling is a common technique for making metal alloys, but more recently chemists have begun to apply mechanical force at the molecular level, especially with the availability of suitable experiment stations at synchrotron light sources. A milling chamber comprises a jar containing the reactants and stainless steel balls. To study the process in operando, an incident x-ray beam irradiates the chamber and the resulting diffraction pattern is recorded. But there are contributions to the diffraction by the jar wall and the steel balls as well as the sample material. To remove the steel-ball contributions, researchers at the Swiss Light Source have developed a more sophisticated chamber in which the milling and probing area are separated, and they have verified its effectiveness. One application is searching for new perovskites for solar cells. By varying the reactants in an in operando study different perovskite structures can be synthesized via molecular-level milling.

Van Swygenhoven switched direction at this point with a description of malaria parasites in infected red blood cells. When the malaria parasite infects a cell, it consumes the globin, leaving heme, which is toxic to the parasite, so why doesn’t it perish? It turns out that the parasite is saved because a protein causes the heme to crystallize to hemozoin, which is no longer toxic to the parasite. One question for those seeking pharmaceuticals to combat the parasite is how long does the crystallization take? By applying soft x-ray tomography to image the red blood cell and x-ray fluorescence microscopy to map the iron content over time, one could in principle obtain this information, but it cannot be strictly in operando because the x-rays would damage the structure being studied. Measuring at liquid nitrogen temperature after different times since infection ameliorates this problem. In the end, one obtains the crystallization rates for the heme.

To finish up, Van Swygenhoven turned to in situ tomography to study crack propagation in Al + Al₂O₃ under tensile load. She showed a movie (9 seconds, 180 frames) of the propagating crack. One challenge arises from the need to rapidly rotate the sample in order to obtain the images at enough angles to reconstruct three-dimensional images over a time interval, 600 rpm in the case of the crack propagation movie. For samples, such as a fly, that cannot withstand high rotation rates, a gated technique was developed in which measurements are made at specific intervals over, in this case, multiple wing-beat periods. The resulting imaging clearly showed the muscles driving the wing beats. Finally, to avoid rotation altogether, necessary for motions that are not quasi-periodic like the beating wings of flies, a multi-beam technique can be invoked. Here, a polychromatic beam illuminates a single crystal and generates a Laue pattern, which then is incident on a sample placed closely enough to the single crystal to catch most of the diffracted beams from the crystal. The multiple beams are equivalent to the multiple rotations normally used for tomography. Van Swygenhoven calls this multi-projection imaging and showed tomography of gold nanoparticles imaged in this way. The technique has not yet been applied to in operando studies.

MRS TV speaks with Plenary Session/Kavli Lecturer Helena Van Swygenhoven-Moens

Helena Van Swygenhoven-Moens of the Material Science Institute at École Polytechnique Fédérale de Lausanne (EPFL)  discusses her Plenary/Kavli talk, “Synchrotron Light to Investigate Materials In Operando.”

 

MRS TV presents new broadcasts each day during the Meeting.  View it on monitors throughout the convention center, online at mrs.org/spring2019, and in the following hotels:

• Sheraton Phoenix – channel 89
• Hyatt Regency – channel 58
• Renaissance Phoenix – TV in lobby

2019 MRS Communications Lecture with Timothy J. Bunning, Air Force Research Laboratory

Timothy Bunning discusses his MRS Communications Lecture, “Dynamic Optical Properties of Gold Nanoparticles/Cholesteric Liquid-Crystal Arrays.”

 

MRS TV presents new broadcasts each day during the Meeting.  View it on monitors throughout the convention center, online at mrs.org/spring2019, and in the following hotels:

• Sheraton Phoenix – channel 89
• Hyatt Regency – channel 58
• Renaissance Phoenix – TV in lobby

MRS Outstanding Young Investigator Award

Sheng Xu, University of California, San Diego

Soft electronics for noninvasive health care—From the skin to below the skin

Written by Don Monroe

Flexible electronic systems have gotten a lot of attention in recent years for their ability to monitor mechanical, electrical, and chemical signals on curved, flexible, or rough surfaces, for example for biomedical applications. In his Outstanding Young Investigator talk, Sheng Xu, of the University of California, San Diego, showed devices that extend this sensing ability several centimeters into the body.

Specifically, Xu showed a flexible patch containing an array of ultrasound transducers. When applied to the skin over a major blood vessel, for example in the neck, this device provides a continuous record of the vessel dimensions and thus of the blood pressure. In addition to providing greater temporal detail, the patch can be used during exercise and away from the clinic, in part because the flexibility allows for intimate skin contact without the usual ultrasound gel. “It enables a new sensing modality that gives us an overwhelming abundant information that is not accessible by conventional modalities,” for blood-pressure monitoring, Xu said, and “effectively opened up a new sensing dimension for the wearable community.”

The ultrasound device takes advantage of versatile platform for flexible electronics. One key enabler is that even stiff materials like metals and semiconductors become highly flexible when they are thin enough, as well as being less prone to fatigue because defects can easily find their way to the surface.

Xu and others have shown that such flexible structures can also be integrated with stiff components, including commercial chips, batteries, and other devices, to leverage their functions and low costs. In particular, stiff islands can be connected by thin, wavy bridges that absorb any external strain. Following encapsulation, for example with a soft polymer, the resulting sheets of “hybridized material” can be strained by 50% or more without losing their functionality. Moreover, they can form intimate contact with complex, flexible surfaces like skin with reduced irritation, better signal quality, and robust operation outside the clinic.

Another important feature Xu’s group developed is “mechanically invisible” integration. This technique bonds large rigid structures only at a small footprint, avoiding the strains that would otherwise concentrate around large-area devices.

Complex electronic systems often include multiple functional layers, with electrical communication provided by vertical vias that connect specific layers, but most flexible electronics schemes provide only a single layer. Xu and his colleagues developed selective laser ablation techniques to open vias, and he showed a four-layer flexible device that allows “new functions that are not possible in single-layer devices,” he said.

In addition to the ultrasound device, Xu showed several other devices that he and his collaborators built with the flexible electronic platform. These included a flexible bio-fuel cell, a wearable chemical sensor, and a patch that measures and wirelessly transmits electrocardiograms or other physiological signals. He also showed a device that measures the orientation of a person’s arm and uses that control a prosthesis.

Xu emphasized that soft electronics importance goes beyond new fabrication and materials strategies. “It is truly a field driven by the unmet need, especially in this clinical, medical area.”

The MRS Outstanding Young Investigator Award recognizes outstanding, interdisciplinary scientific work in materials research by a young scientist or engineer. The award recipient must also show exceptional promise as a developing leader in the materials area.  

Xu’s award citation is “for materials and device designs in biointegrated electronics and stretchable energy systems."