Thank you!

The 2019 MRS Spring Meeting & Exhibit came to a successful conclusion on Friday, April 26, with materials researchers and exhibitors gathered from around the world.

Our congratulations go to Meeting Chairs Yuping Bao, Bruce Dunn, Subodh Mhaisalkar, Subhash L. Shinde, and Ruth Schwaiger for putting together an excellent technical program along with various special events. MRS would also like to thank all the Symposium Organizers, Session Chairs, and Symposium Assistants for their part in the success of this meeting. A thank you goes to the Exhibitors, Symposium Support, and to the sponsors of the special events and activities.

Contributors to news on the 2019 MRS Spring Meeting & Exhibit include Meeting Scene reporters Chiung-Wei Huang (@CWHuang14), Gargi Joshi, Judy Meiksin (@Judy_Meiksin), Aashutosh Mistry, Don Monroe, Bharati Neelamraju (@Bharati_30), Prachi Patel, Arthur L. Robinson, and Lori Wilson; Bloggers Kony Chatterjee, Dale E. Karas, and Dongwei Sun; and photographers Stephanie Gabborin and Heather Shick; with newsletter production by Karen Colson and Shayla Poling, and newsletter design by Erin Hasinger.

Thank you to MRS Meeting Scene sponsors SPI Supplies; Goodfellow Corporation; Lake Shore Cryotronics, Inc.; Thermo Fisher Scientific; American Elements; Rigaku; and MDPI.       

Thank you for subscribing to the MRS Meeting Scene newsletters from the 2019 MRS Spring Meeting & Exhibit. We hope you enjoyed reading them and continue your subscription as we launch into the 2019 MRS Fall Meeting & Exhibit - the conversation already started at #f19mrs! We welcome your comments and feedback.

Symposium ES04: Solid-State Electrochemical Energy Storage

Miaofang Chi, Oak Ridge National Laboratory

Electron Microscopy for All-Solid-State Batteries—Addressing Challenges at Atomic Scale

Written by Aashutosh Mistry

Battery science has seen a fundamental shift in recent years toward the use of solid electrolytes. Conventional liquid electrolytes cause a conformal contact at the electrode–electrolyte interface, which switches to intrinsically nonconformal solid–solid contact in the newer setting. However, the issues with the solid electrolytes extend beyond this geometrical nonconformity, and in order to investigate the fundamental origins of electrochemical limitations the state-of-the-art characterization tools are insufficient since they were designed explicitly for solid–liquid electrochemical contact. Thus, there is an urgent requirement to invent (or modify) a host of characterization techniques for this new class of electrochemistry.

Miaofang Chi and her colleagues at Oak Ridge National Laboratory have been advocating the use of in situ functional imaging—electron-microscopy techniques posing requisite scientific merit. She emphasized that the primary bottleneck in solid-state electrochemistry is the myriad set of interfacial phenomena, namely, instability, impurity, elemental diffusion, and space charge, for instance. In one of the examples, the researchers explored the grain boundary resistivity for two different solid electrolytes (LLTO and LLZO, lithium lanthanum titanium oxide and lithium lanthanum zirconium oxide) and found that the LLZO grain boundaries exhibit similar chemical composition as the grains, while LLTO grain boundaries are lithium-deficient which explains a greater grain boundary resistance in LLTO. Another puzzling observation had been the relative stability of Li–LiPON (another solid electrolyte) interface. The researchers’ in situ observation of Li and LiPON contact showed that a chemical reaction takes place upon contact between the two solids which results in a new interphase between the two. This interphase is stable over the electrochemical operation and is the root cause for extended cycling. Upon elemental mapping using EELS (electron energy-loss spectroscopy), it was revealed that this interphase represents the decomposition of LiPON into Li₃N, Li₂O, and Li₃P. The developed techniques are suitable for different types of 4D (space and time) in situ investigations of solid–solid electrochemistry.

 

Symposium CP04: Interfacial Science and Engineering—Mechanics, Thermodynamics, Kinetics and Chemistry

Ricardo Castro, University of California-Davis

Nano-scale Effects on Grain Growth—Grain Boundary Energy and Velocity in Magnesium Aluminate

Written by Aashutosh Mistry

Most of the materials of engineering relevance are polycrystalline in nature. Desired properties of such materials strongly depend on the underlying grain structure, making the study of grain formation and growth scientifically important. With advances, it has become possible to create a grain structure with nanosized grains. Nanograins possess lucrative characteristics of increased grain boundary density, greater resistance to dislocation movement, and equivalently higher mechanical strength. At such small dimensions, interfacial effects are expected to play a crucial role; however, such effects remain poorly understood.

Ricardo Castro and his research group have been investigating the nanoscale effects on grain growth. The essential question is: do nanosized grains grow differently than the microsized ones? The researchers studied MgAl₂O₄ spinel as a model system. Since the grain growth is a thermally activated process, they carried out DSC (differential scanning calorimetry) measurements over different temperature ranges to obtain different average grain sizes. Over the course of such experiments, the heat release due to grain growth recorded which in turn gives a measure of surface energies for different grain sizes. Their experiments demonstrate higher surface energies for smaller grains and approaching to the nominal value for microsized grains. Their ongoing work deals with identifying the origins of such excess surface energy.

Symposium SM01: Materials for Biological and Medical Applications

Caroline Ajo-Franklin, Lawrence Berkeley National Laboratory

Living Foundations: Programming Cells to Synthesize Hierarchically Ordered Materials

Written by Gargi Joshi

Structural hierarchy found in nature imparts several survival characteristics to organisms including high toughness as observed in shells, bones, and teeth to prevent crack propagation. The components involved are a mix of hard and soft features across multiple length scales. We as researchers learn from such examples and try to mimic nature by synthesizing such materials but understanding of the key processes has not been unveiled. Caroline Ajo-Franklin is trying to assess the mechanisms by using a bottom-up synthesis of assembling engineered living systems similar to nacre (pearl from mollusks). Synthetic biology provides this scope as two strains having different properties of surface attachment were associated together by artificial engineering. The designed combination demonstrated behavior of a hydrogel similar to that in living systems. Not only this, but the behavior can be dynamically modified by altering the crosslinking densities in the hydrogel to display switchable mechanical properties.

Symposium QN03: 2D Materials—Tunable Physical Properties, Heterostructures and Device Applications

Clarissa Towle, University of California, Berkeley and Lawrence Berkeley National Laboratory

4D STEM Study of Au-Induced Epitaxial Strain in Few- and Monolayer MoS₂

Written by Bharati Neelamraju

Associated with both UC Berkeley and Lawrence Berkeley National Lab (LBNL), most of Clarissa Towle’s work was done at LBNL using the four-dimensional (4D) scanning transmission electron microscope (STEM). Towle explains that this microscopy is 4D because the microscope scans a 2D array of 2D diffraction patterns of a given sample. She works on the epitaxial growth of gold on 2D transition metal dichalcogenides (TMDCs) to understand the role of strain on the top layer of a stack for opto-electronic device fabrications. Towle emphasized the fact that this technique uses about 2000 images or more to provide precise useful data. The researchers also use neural networks to increase the pace of their “Big Data” set analysis. They teach the neural network about the diffraction patterns of the gold on TMDCs. While the neural network gives the basic lattice diffraction peaks, it still does not understand all the nuances and says the same. Her excitement connected with the 4D STEM images and the data they have so far was contagious.

Symposium ES15: Fundamental Understanding of the Multifaceted Optoelectronic Properties of Halide Perovskites

James Sadighian, University of Oregon

In Situ Transient Absorption Spectroscopy of Perovskite Nanocrystal Formation and Growth

Written by Gargi Joshi

Perovskite nanocrystals (NC) have attracted significant interest due to their tunable properties and applicability in light-emitting diodes, lasers, and optical sensors. Usually it is difficult to use time-resolved spectroscopy techniques with the fast synthesis rate of preparation of NCs as well as the unstable nucleation centers behaving as nascent nanocrystals. In order to modulate the functional electronic properties of these particles it is of utmost importance to be able to clarify development of the excited stable dynamics during their formation. James Sadighian prepared methylammonium lead halide perovskite NCs by a ligand-mediated NC synthesis comprising of reaction timescales favorable for study via transient absorption spectroscopy. With this room temperature synthesis initiated by solvation of the precursors with passivating ligands, Sadighian has done first known characterization of immature perovskite NCs in the dynamic unstable state. Future work includes measurement of the growth of these NCs in real-time using the single-shot transient absorption spectrometer, which can give entire transient results in a few seconds.

Symposium X: Frontiers of Materials Research

Bart Biebuyck, The Fuel Cells and Hydrogen Joint Undertaking

Development of Fuel Cells and Hydrogen Technologies in Europe Toward Commercialization from 2020 Onward

Written by Prachi Patel

Bart Biebuyck gave an excellent overview of the progress on fuel cell and hydrogen technologies in Europe. The Joint Undertaking is a public-private partnership of the European Commission, and the industry and research arms of the Hydrogen Europe group. With 1.7 billion Euros in funding, the partnership’s mission is to accelerate research and development (R&D) and bring these technologies to market readiness by 2020.

The goals of the Undertaking are to produce hydrogen in a green way by using less critical raw materials; low-cost fuel cells for transportation, heat, and electricity; and, the key driver for Europe, hydrogen storage for integrating renewables on the grid.

Several ongoing projects on electrolysis to produce hydrogen have already generated materials breakthroughs and slashed the cost of electrolysers since 2011, he said. This has boosted capacity. Megawatt scale electrolysers that produce green hydrogen fuel are now operating at various industrial plants around Europe. A large bakery in Völs, Austria, for instance, uses the hydrogen from its 3.4 MW hydro-electricity-powered electrolyser to heat bread ovens. This offsets the carbon emissions from baking bread, each gram of which produces a gram of carbon dioxide, Biebuyck said.

Research is also underway on using solar power to split water, but improvements in efficiency are needed, he said. The EU industry has launched an initiative to have a 40 GW electrolyser by 2040.

Next, he addressed progress in the area of fuel cells for transport. The focus of materials research here is to find catalysts that use little or, ideally, no platinum. Today’s platinum-based catalysts make up a third of fuel cell cost. Another avenue to reduce cost is to eliminate rare-earth materials found in some components.

The Joint Undertaking also supports fuel cell vehicles and infrastructure. Asian car manufacturers dominate the market today, but some European auto companies plan to have hydrogen car prototypes by 2025. As for refueling stations, there are 120 now in Europe, but 50 member states have committed to building more, reaching a target of about 850 by 2025. “We are also focusing on fuel cell buses to clean up cities,” Biebuyck said. Fuel-cell buses are expected to reach cost-parity with diesel and battery buses in the next 2–3 years. Meanwhile, the first fuel-cell garbage trucks are starting to appear on the market. 

Biebuyck went on to talk about the potential of fuel cells in railway transport, and promising demonstrations in hydrogen-powered aircraft and ships. For ships, there needs to be regulations, and there is a need for research on liquid-hydrogen storage and megawatt-scale fuel cells for ships.

Finally, in the area of heating and cooling, there is a need for research advances in solid-oxide fuel cells. Breakthrough concepts like 3D-printing are being funded by the Joint Undertaking. And installations of “washing machine-sized” micro combined heat and power systems are going up steadily in Europe.

Biebuyck ended by giving a glimpse into the future. Last year, 28 European countries signed an agreement to work on hydrogen research. In the 100 billion Euro Horizon Europe research program “you will find hydrogen and fuel cells many times in the text, even more than batteries,” he said.

But for solid progress to be made in this area, international cooperation is going to be critical, he stressed. And there is a dearth of talented materials scientists and engineers in the area. “We really need you,” he said to the audience, “because in hydrogen and fuel cells, materials research is very important. Look at hydrogen fuel cells, because I guarantee you it will be a successful future.”

Symposium ES04: Solid-State Electrochemical Energy Storage

Jan Allen, US Army Research Laboratory

Synthesis and Characterization of Fast Li-ion Conducting Solid State Electrolytes

Written by Aashutosh Mistry

Solid electrolytes represent a key research area in lithium batteries for a safer future. Many different solid electrolytes have been invented in recent years with the primary aim of matching ionic conductivity to their liquid counterparts. Most of the electrolytes are poor ion conductors in their pristine form, and elemental doping appears to be an effective strategy to advance these materials. Toward that end, Jan Allen and his collaborators have studied various different solid electrolytes and their subsequent substitutions to assess the relative usefulness. They identified that a reduction of titanium Ti⁴⁺ is an issue for perovskite (e.g., LLTO lithium lanthanum titanium oxide) and NaSICON (e.g., LATP lithium aluminum titanium phosphate) type electrolytes. On the contrary, zirconium-based solid electrolytes, specifically LZP (lithium zirconium phosphate) and LLZO (lithium lanthanum zirconium oxide) are more stable. Both these materials are amenable to substitution via other cations (calcium, yttrium, aluminum, tantalum, gallium, etc.) and provide increased conductivity. For example, consider substitution to LLZO structure via Ta, Al, and Ga. Ta replaces Zr sites and changes the unit cell, Ga has an octahedral site preference, and Al prefers tetrahedral sites (which competes with Li). Ta-doped LLZO has higher conduction than Ga-doped and Al-doped is inferior given the competition of Al with Li distribution. Such experiments provide valuable design rules for choosing solid electrolytes and appropriate substitutions.

Symposium CP04: Interfacial Science and Engineering—Mechanics, Thermodynamics, Kinetics and Chemistry

Shen Dillon, University of Illinois

Oxide Grain Boundary Deformation and Failure Characterized by In Situ TEM

Written by Gargi Joshi

Along with synthesis and preparation of metal oxide incorporating materials comes defects and dislocations. In this regard the grain boundaries in these metal oxides tend to significantly affect the final mechanical response. The major concern is their weak presence in the bulk, which causes deformations/fractures. The influence is observed in bulk polycrystalline measurements and poses difficulty in assessing individual contributions. Shen Dillion has done single interface measurements at a small scale using the technique of in situ TEM. This contributed in determining the fracture energies from real interfaces in the polycrystals and answers the characterization of interface mechanics. Dillon specially focused on the factors of grain boundary sliding and grain rotation inversing the stress response (Hall-Petch strengthening) in such materials.

Symposium QN04: Nanoscale Heat Transport—Fundamentals

Pierre-Olivier Chapuis, CNRS - INSA Lyon

Scanning Thermal Microscopy—Probing Temperature and Heat Dissipation Down to the Few-Nanometers Scale

Written by Bharati Neelamraju

Pierre-Olivier Chapuis covered the use of scanning thermal microscopy, which is based on the concept of atomic force microscopy but with heat. This technique has applications at micro- and nanoscale levels of samples where the researchers can characterize local thermal conductivity, local melting temperature, and local heating in ICS, for example. Some other uses of this technique include nano-lithography and data storage. This technique competes with other optical methods and has a shortcoming when the sample roughness is too high. Chapuis showed that in their laboratory, SThM is used under varying environments that include vacuum, a homemade SEM system, and a homemade cryo cooled sample. Chapuis discussed the sensitivities of a microprobe and a nanoprobe with varying materials and emphasized the need for proper calibration. He showed that as of now, thinner samples had a higher error bar while thicker samples had very precise measurements. He emphasized that SThM makes measurements in the cross plane direction while most other techniques only do it in the in-plane direction of the sample. The final dream of this project is to be able to take precise thermal conductivity measurements with no contact under vacuum. From theoretical calculations the researchers compute a flux between probe and sample that gives a spatial resolution for non-contact SThM to be approximately 10 nm.