Tuesday, 13 February 2018 16:39

Erica Eggleton

Summer Scholar Erica Eggleton joins Van Vliet Lab to make and test lithium manganese oxide electrodes.
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Graduate student Frank McGrogan, left, is supervising the work of Summer Scholar Erica Eggleton on LMO electrodes for lithium ion batteries in the Van Vliet Lab. Photo, Denis Paiste, Materials Processing Center.

After studying fuel cells at Montana State University, Erica Eggleton knew she wanted to do some type of research this summer, either with a college or in industry. “I’ve always been really interested in renewable energy, and in my lab at Montana State, I study PEM [proton exchange membrane] fuel cells, so I wanted to stay in that realm of research,” she says.

Her quest brought Eggleton, who just finished her junior year, to MIT as a 2016 MPC-CMSE Summer Scholar, where she is working in the Van Vliet Lab on lithium manganese oxide [LMO] electrodes for lithium ion batteries. Materials science and engineering graduate student Frank McGrogan is supervising her work.

This year’s 11 Summer Scholars spent their first three days in the internship program hearing project pitches from faculty, postdocs and graduate students and touring their labs. “I definitely wanted to expand my knowledge on electrochemical-based processes and there were a couple of projects that were in that field. Then I looked more at the principal investigators [PIs] and talked to the grad students during the lab tours and this one definitely seemed like a good fit, community-wise. Also, I thought it would be beneficial for me to learn about the topic from more of a materials science standpoint, because I’m starting to question, if I want to go more into materials science in grad school or whether I’m actually more interested in chemical-based processes like now,” Eggleton says.

Lab head Krystyn Van Vliet, who holds MIT faculty appointments in both biological engineering and materials science and engineering, says, “From my perspective, REU [Research Experience for Undergraduates] students such as Erica bring great enthusiasm to our lab during the Summer Scholar research period. They provide a valuable mentoring opportunity to our graduate students who realize anew the excitement and potential of their challenging, multi-year research projects, and the REUs themselves contribute unique perspectives on how to solve lab challenges.

“I have had several REU students contribute so much to a project in the two months they were here that they were co-authors on publications, and the impressive career trajectories of those REUs who worked in my lab – ranging from young faculty to medical school to graduate engineering research – shows that they made the most of the REU opportunity at MIT,” Van Vliet adds.

Eggleton is studying the type of fatigue that makes lithium ion batteries less efficient over time. “We’re studying whether this is based off of certain stresses, cracking or fractures and how that’s affecting the overall efficiency of the battery. I know I’m going to be working on making different types of electrodes and then I will look at them using SEM [scanning electron microscopy] to analyze the film properties,” Eggleton says.

Working with McGrogan, Eggleton did indentation hardness testing and cracking tests in one of her first days on the job as an intern. She’ll be making electrodes and studying the materials with analytical techniques such as SEM.

McGrogan, in his first summer working with an undergraduate, says, “Working with my REU (Erica) has refreshed my perspective on my research, as she brings a new curiosity to the problems I'm trying to solve. Erica has met my research questions with eyes wide open, and I find her ambition and enthusiasm to be personally motivating. I feel certain that she will be an important contributor to my research projects by the end of the summer.”

MPC‬‬‬‬‬‪ and CMSE sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from NSF’s Materials Research Science and Engineering Centers program (grant number DMR-14-19807).‬ The program runs from June 7 through Aug. 6, 2016.‬‬‬‬‬

Denis Paiste, Materials Processing Center
June 29, 2016

 

 

Tuesday, 13 February 2018 16:37

Suna Njie

Summer Scholar Suna Njie works with new technique in Strano Lab.
Suna Njie Graphene 6487 Web
Suna Njie is working this summer in the Strano Lab on graphene fibers under postdoctoral associate Pingwei Liu. Two days into her project, Njie grew graphene and put it into an etching solution. Here, she removes salt contaminant from the graphene film by soaking it in water. The next step will be to scroll the graphene into fiber, a new technique developed by Liu. Photo, Denis Paiste, Materials Processing Center

Coming from a biology pre-med program at Alabama State University, junior Suna Njie wanted to try something new in her internship at MIT as an MPC-CMSE Summer Scholar. Her project on making graphene fibers in the Strano Lab is giving her just that opportunity.

“I chose this lab because it was different from what I have done before, however it is not too out of my comfort zone. This internship is about material science and engineering. I have never done anything in materials science, but here, I will be working with graphene to create fibers out that could possibly have biological implications. I could definitely use this in my future endeavors,” Njie says.

Njie hopes to pursue a joint M.D./PhD program after graduation. “When I enter an M.D./PhD program, I could use graphene in a project to further some technology in biology also, so it’s the best of both worlds,” she says.

Njie Graphene CloseUp IMG 6498 Web 
Close up of graphene film soaking in water to remove contaminants prior to scrolling the graphene into fiber. Photo, Denis Paiste, Materials Processing Center

Working under postdoctoral associate Pingwei Liu, Njie is fabricating polymer/graphene composite films and will scroll it into fiber, using a technique that Liu developed, which is is in the process of publication. In this project, Njie will do more mechanical tests to study the detailed elongation and failure mechanism of these new fibers, and check the stiffness and toughness of the fiber and the effect of the graphene.

“I grew graphene with a chemical vapor deposition method yesterday, and I put it into the etching solution, and now I’m trying to rinse the film in clean water,” Njie explains, during one of her first days working in the lab. “...So, right now I’m just waiting, leaving it in water, and repeating the rinse, so we can get as much of the salt contaminant out, and then I’m going to scroll it into fiber, and then I’ll have fiber.”

Michael S. Strano, Carbon P. Dubbs Professor of Chemical Engineering, says of the summer internship program, “The MPC-CMSE scholars are an extremely impressive, carefully selected set of students who have performed marvelously in my lab over the years. Although only with us for eight weeks, these students very often end up publishing with us, and always bring new ideas and energy to our projects.”

MPC‬‬‬‬‪ and CMSE sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from NSF’s Materials Research Science and Engineering Centers program (grant number DMR-14-19807).‬ The program runs from June 7 through Aug. 6, 2016.‬‬‬‬‬‬

– Denis Paiste, Materials Processing Center
June 29, 2016

 

Tuesday, 13 February 2018 15:26

Jennifer Coulter

Summer Scholar Jennifer Coulter models how spinning colloidal particles move through a fixed array of obstacles.

 

Summer Scholar Jenny Coulter 7081 Web
MPC_CMSE Summer Scholar Jennifer Coulter worked on modeling the behavior of ferromagnetic particles stimulated by a rotating magnetic field to spin in a passive cluster of non-magnetic particles. Image on computer in background shows map of the path traveled by individual active particles as they spin through the passive matrix, with colors denoting particle location at different times. Purple represents the particles’ positions at the start of the simulation, while red represents the particles’ positions at the end. Coulter interned under Alfredo Alexander-Katz, the Walter Henry Gale Associate Professor of Materials Science and Engineering at MIT. Photo, Denis Paiste, Materials Processing Center.

Earlier this year, MIT Associate Professor Alfredo Alexander-Katz’s group demonstrated experimentally that ferromagnetic particles spinning under a rotating magnetic field in a milky suspension are attracted to each other across relatively long distances in a crowd of non-magnetic particles.

MPC-CMSE Summer Scholar Jennifer Coulter interned with Alexander-Katz, the Walter Henry Gale Associate Professor of Materials Science and Engineering at MIT, this summer on a project to develop a more generalized computer model for these active spinning particles in a passive colloidal mixture. “We’re studying the interactions of the spinners with the passive particles through simulation,” Coulter says. Describing this theoretical environment, Coulter explains, “Only the spinners move.” The non-magnetic particles are now fixed in a pattern without moving during the simulation.

This project fits into the Alexander-Katz lab’s work on a wide range of active soft matter challenges from understanding how neurotransmitters move from one neuron to another in the brain to how single-celled organisms sense each other at a distance. “The power of soft means [that] with very small stimuli we can actually have large or strong changes,” Alexander-Katz said during a presentation to Summer Scholars in June. Alexander-Katz is part of the Physics of Living Systems group.

For Coulter, a rising senior at Rutgers University whose prior work focused on high-energy physics, biophysics is new territory. “The way I’ve been working with him on this project has been an experience in using what I know in terms of computing and general physics knowledge to develop and explore a new system,” she says.

“I’ve actually found that a lot of the work I did in high-energy physics has been really useful because that’s also computational, even though it’s very different. So I had some skills coming in, but I’ve definitely had some time to work on them here,” Coulter says.

“I’m running larger scale things, where I have to deal with huge numbers and lots of data, so I need to consider things in Unix command lines,” she says. “I’m using different computers to run my code, because I can’t run it on my laptop. It would overheat or take days,” Coulter explains. She is writing much of the code for this project herself from scratch using Python and a mix of Unix tools including Bash and Shell scripts.

“I think that in terms of just general computing stuff, in Unix and other things, it’s been really good to spend more time working on that, because those are skills I hope to use in grad school. I’d like to go for computational physics, probably,” Coulter says.

Using this computer model, Coulter analyzed how changes in simulation specifications affect the end result. For example, she could alter the speed at which the magnetic field rotates, change the torque from hydrodynamic interactions and modify the attractive or repulsive force between spinners and passive particles.

MIT researchers led by Alfredo Alexander-Katz, the Walter Henry Gale Associate Professor of Materials Science and Engineering at MIT, found long-range interaction between particles in a liquid medium based entirely on their motions. Video, Melanie Gonick, MIT.

“The key thing that we’re going to vary is a parameter that’s going to help us describe the disorder of the way we’ve arranged the passive particles; so we want to study how disorder affects the transport of the spinners through the passive particles,” Coulter says. The simulations cover a range from a highly ordered system through a range of different distortions to the ordered system to see how spinners behave as disorder increases.

She hopes to learn under what conditions spinners move in a straight line versus a diffuse pattern, that is, scatter in different directions. “I think it would be cool if we could see really diffusive transport in relation to adding disorder to our system,” Coulter says. “The end goal is to compare the active matter system to a system that’s currently very popular in terms of topological materials and 2D materials and transport in those materials. So we would like to try to create this system as an analogue to that more difficult to study system.”

Coulter says Alexander-Katz has been an extremely involved advisor. “I think in terms of my personal growth, actually the best part of my experience here has been just working with Prof. Alexander-Katz,” she says. “It’s really nice to be able to talk to him for an hour or more at a time, several times a week. He’s really supported me and gives really good feedback, and I think in terms of my development as a scientist, a lot of what I’ve gained from this has just been in my experience working with him. I really appreciate his role as a mentor.”

Success for her project would be characterizing the disorder of the arrangement of passive particles, and how it changes the nature of transport for the spinners, Coulter suggests. “It’s actually, I think, something we’re pretty close to attaining, but since it was a smaller project, we are now starting to do some more final runs of the code. I’m about to get some of the last results soon ... so hopefully they’re the good kind. They’ve looked really promising up to this point.” 

‪MPC‬‬‬‬‬‪‬‬‬‬‬‬‬‬‬‬‬‬ and ‪CMSE‬‬‬‬‬‬ sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from ‪NSF‬‬‬‬‬‬’s Materials Research Science and Engineering Centers program (grant number DMR-1419807).‬ The program runs from June 7 through Aug. 6, 2016.‬‬‬‬‬ ‬‬‬‬

 

Denis Paiste, Materials Processing Center | Aug. 22, 2016

Tuesday, 13 February 2018 15:22

Victoria Yao

Summer Scholar Victoria Yao experiments with water-based, flow-driven battery concept in Brushett Lab.

Summer Scholar Victoria Yao 2 MEA Web
MPC-CMSE Summer Scholar Victoria Yao shows a mixture of sodium thiosulfate being stirred in a solution of copper hexacyanoferrate where its reacts to produce larger compounds that can be filtered out of the solution. These compounds are being developed for use in electrodes for a water-based flow-driven battery for grid level storage. Photo, Maria E. Aglietti, Materials Processing Center.

A convection oven cooks more uniformly because a fan creates a steady flow of hot air around the food being cooked. MIT’s St. Laurent Career Development Professor of Chemical Engineering, Fikile R. Brushett, is applying that principle to a new water-based battery design that pumps a steady flow of charge-carrying ions through a battery to create a more uniform distribution of ions in the cell.

“We’re fabricating an aqueous [water-based] battery which is safe, cheap and scalable,” MPC-CMSE Summer Scholar Victoria Yao explains. A rising junior at Vanderbilt University, Yao is majoring in chemical engineering. This summer, she worked with graduate student Thomas J. Carney to develop a convection cell battery, in which electrolyte would flow through the electrode material, rather than remain static as in a conventional battery.

During her summer internship in the Brushett Research Group, Yao synthesized electrode materials in the same chemical family as Prussian blue, which is commonly used to dye fabric and to color makeup such as eye shadow. Prussian blue is the common name for ferric ferrocyanide, but unlike some highly poisonous cyanide compounds, Prussian blue is considered non-toxic and is even ingested to treat radiation poisoning.

Yao created the Prussian blue-like materials in a liquid solution of metal nitrates, adding potassium hexacyanoferrate to precipitate the desired compounds, such as copper hexacyanoferrate. Sodium thiosulfate is added to make the particles bigger and change the amount of energy stored in the material. She then separated out the particles with a filter or centrifuge. Once dried, the colorful particles were mixed with additives to make “inks” that can be precisely dripped on carbon paper to form thin electrodes for battery testing. “Immediately after you make the ink, you need to pipette it onto carbon paper, let it dry, and then remove any contaminants under vacuum,” Yao says.

These thin electrode cells were tested in a flow-through reactor – an arrangement of glass components in an “H” configuration – that runs for hours at a time, sometimes overnight, to gather sufficient data to measure their capacity and efficiency. The carbon-paper electrodes are placed in the upright glass tubes with a sodium chloride [table salt] solution connecting the two through the middle. After adding a reference electrode, Yao bubbled argon gas through the experimental setup.

“I’ve made eight different powders, and tested their energy storage properties with thin electrodes,” she says.

After making and testing thin electrodes, Yao plans to move to producing thick porous electrodes, which could yield higher energy density. These thick electrodes require more raw material, which is compressed into pellets.

In presenting this project, which he calls Convection Enhanced Electrochemical Energy Storage, to Summer Scholars in June, Brushett said, “We’ve got a proof of concept, and we’re really excited. ... Ideally we’d like to translate this proof-of-concept device into a little canister-like flow cell with thick porous electrodes and pump electrolyte through the reactor... and there we should have our convection battery.”

Summer Scholar Victoria Yao 1 MEA Web
MPC-CMSE Summer Scholar Victoria Yao holds a container with a thin electrode made of carbon with a copper hexacyanoferrate [Prussian blue] type active area at the top end. Photo, Maria E. Aglietti, Materials Processing Center

“Prussian blue-related chemical compounds have an open framework that allows ions to move in and out of the two battery electrodes while remaining solvated (bound to water molecules) by the electrolyte solution which, in turn, enables fast reactions. When coupled with a flowing electrolyte we may be able to develop energy dense batteries with thick electrodes and tunable power output,” Brushett says. The project fits into the Brushett lab’s larger goal of helping to build a sustainable energy economy through innovative, new energy storage technologies.

“Victoria has been instrumental in synthesizing and characterizing Prussian blue analogue materials for use in convection-based energy storage devices this summer. The MPC-CMSE Summer Scholar’s program provides opportunities for talented undergraduates from across the country to work on cutting-edge research projects here at MIT,” Brushett says. “Not only do these students learn of the discipline, tenacity, and creativity required to perform fundamental research but our graduate students learn how to mentor enthusiastic but less experienced lab workers. Her dedication and aptitude have directly accelerated our research! We are very happy to have hosted her this summer.”

‪MPC‬‬‬‬‬‪‬‬‬‬‬‬‬‬‬‬‬‬ and ‪CMSE‬‬‬‬‬‬ sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from ‪NSF‬‬‬‬‬‬’s Materials Research Science and Engineering Centers program (grant number DMR-14-19807).‬ The program runs from June 7 through Aug. 6, 2016.‬‬‬‬‬ ‬‬‬‬ 

 

Denis Paiste, Materials Processing Center | Aug. 22, 2016

 Related: Going with the Flow Battery

Tuesday, 13 February 2018 15:19

Grant Smith

Summer Scholar Grant Smith works to establish parameters for making ferromagnetic thin films in Luqiao Liu lab.

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MPC-CMSE Summer Scholar Grant Smith looks into a sputter deposition chamber where he makes ultra thin films [from 2 to 10 nanometers thick] of special magnetic materials suitable for spin-based electronics. He is working under MIT Assistant Professor of Electrical Engineering and Computer Science Luqiao Liu. Smith’s summer project involves growing the films, making experimental device prototypes and measuring their properties. Spin-based systems such as magnetic tunnel junctions are often used in computer memory systems. Photo, Denis Paiste, Materials Processing Center.

MPC-CMSE Summer Scholar Grant Smith is working in the lab of MIT Assistant Professor of Electrical Engineering and Computer Science Luqiao Liu, to create special thin film materials suitable for spin-based devices such as magnetic tunnel junctions used in computer memory.

Smith is operating a sputter deposition chamber where he grows these ultra thin films from 2 to 10 nanometers thick. His summer project involves making devices that are precursors to a memory device and measuring their properties.

Magnetic tunnel junctions used in spin-based systems for computer memory got their start with a key breakthrough in 1994 at MIT by Dr. Jagadeesh S. Moodera and colleagues. They are especially valued because they retain information even when the power is off.

A magnetic tunnel junction pairs two thin film materials, each with a special property called ferromagnetism. “Those ferromagnetic layers can either have their magnetizations aligned or anti-aligned,” Smith explains. If they are aligned, that is their magnetic fields both point in the same direction, the electrons in one layer will have more states available for them in the other layer, but if they are anti-aligned [with magnetic fields pointing in opposite directions], there will be fewer states for electrons available in that other layer.

Change in resistance

“When you’re trying to push a current through and the magnetizations are aligned, the resistance is much lower. So if you fix one of the magnetic layers and flip the other one based on whether you want it to be a zero or a one or if you’re just trying to detect the existence of a magnetic field, you’ll be able to see something on the order of a 100 to 300 percent change in the resistance of that device,” Smith says. This is about 10 to 30 times greater that the approximately 10 percent shift in resistance in the first such devices.

Smith is working with a dual-layer of an antiferromagnet called iridium manganese and a ferromagnet called cobalt iron boron. “Those two in conjunction, when you condition them in a specific way, they pin the magnetization of the one ferromagnet in that one specific direction. So that is your fixed layer,” he explains.

For his summer project, Smith seeks to establish that ability to grow these magnetic tunnel junctions in Liu’s lab, and if that is a success, to try to manipulate that magnetization with the spin texture of a topological semimetal in order to do switching.

Nice spot to be

“I’m just happy to learn anything about this field basically,” says Smith, a rising senior at Penn State majoring in physics, who hopes to pursue a doctorate in the sciences. “I’m glad to be learning how to manufacture these magnetic tunnel junctions. That’s a really important skill. They’re used everywhere as far as doing experiments in this field. They’re useful in industry. It’s actually a very nice spot to be in.”

Liu, who joined the MIT faculty in September 2015, says, “So far I have been very glad with summer intern Grant Smith’s performance. Having a summer intern working in our lab does provide a good advantage to our research as it allows us to look into directions that we were not able to previously due to a shortage of manpower. Moreover, Mr. Smith is really diligent and smart. It is a very nice experience so far to work with such a motivated undergraduate student.”

Change of pace

For Smith, working in Liu’s lab on materials at room temperature is a change of pace from his work at Penn State on materials at extremely low temperatures in the range of 4 kelvin [minus 452.47 F]. “When you’re working with these sort of things you can learn about new behaviors, new scientific phenomenon,” he says. “Here everything is very room temperature focused working much closer towards, working much more closely with the place industry is at right now,” Smith says.

MPC‬‬‬‬‬‬‬‪ and CMSE sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from NSF’s Materials Research Science and Engineering Centers program (grant number DMR-14-19807). The program runs from June 7 through Aug. 6, 2016. ‬‬‬‬‬‬‬

 

Denis Paiste, Materials Processing Center | July 27, 2016

Tuesday, 13 February 2018 15:11

Ashley Kaiser

Summer Scholar Ashley Kaiser delves into hybrid carbon nanotube materials research in nectslab.

Ashley Kaiser 6 MEA Web
Ashley Kaiser holds samples of carbon nanotubes she grew in the Wardle lab as part of her summer project studying carbon nanotube-based aligned nanofiber carbon matrix nanocomposites [CNT A-CMNCs]. The carbon nanotubes are on the left, and the pyrolytic carbon is on the right. These new materials have potential aerospace applications. Photo, Maria E. Aglietti.

University of Massachusetts Amherst chemical engineering major Ashley Kaiser joined MIT Professor of Aeronautics and Astronautics Brian L. Wardle's necstlab this summer with past experience in growing graphene and examining it with Raman spectroscopy.

During her new summer internship, Kaiser, who is a rising senior, is learning new fabrication and characterization techniques to further necstlab’s research on carbon nanotube aligned nanofiber carbon matrix nanocomposites [CNT A-CMNCs].

High temperature composites

MPC-CMSE Summer Scholar Kaiser is making these composites, which are treated at high temperatures from 600 to 1400 Celsius [1112 F to 2552 F], and analyzing their composition to study the confinement effects of the carbon nanotubes in the carbon matrix. Similar heat-treated material, called pyrolytic carbon [PyC], is currently used for aerospace applications but in a simpler form without embedded carbon nanotubes. “It’s super hard and lightweight, and since carbon nanotubes are also very strong and lightweight as well, we would like to introduce these nanotubes inside this existing matrix,” Kaiser explains.

“Ashley’s primary contribution is to help us understand how the aligned carbon nanotubes facilitate the self-organization and meso-scale evolution of the graphitic crystallites that comprise the pyrolytic carbons, and how control over the processing (i.e., pyrolysis) temperature can modify the structure and morphology of A-CNT-PyC hybrid nanocomposite materials on the nanoscale,” necstlab Postdoctoral Associate Itai Stein says.

“The results from Ashley’s project will be invaluable to better understanding the process-structure-property relations of these high temperature materials,” Stein adds. Kaiser’s project builds on work done in necstlab by 2015 MPC-CMSE Summer Intern Alexander Constable, who studied the structural evolution of pyrolytic carbon (PyC) as a function of processing parameters and the effects of aligned carbon nanotube (A-CNT) confinement.

Four key steps

Her project consists of four steps, Kaiser explains:

• Carbon nanotube growth
• Polymer resin infusion
• Oven curing the polymer matrix nanocomposites
• High temperature heat treatment (pyrolysis)

“Basically, we want to fabricate and characterize the composites to see what effect the carbon nanotubes are having on the final structure to address several questions – what it looks like, if the nanotubes stay aligned, are there functional groups inside of that, are there defects, what’s the crystallite size, etc.” Kaiser says.

“We are seeing that when we are putting our nanotubes into our composite, the effect of them governs the meso-scale [submicron scale], which means that the way the atoms are arranging in our crystallites isn’t changing too much just from having our nanotubes there, which is interesting. So in terms of scaling this up to, say, something in industry, the fact that it’s not changing the entire atomic scale is beneficial because it means that processing may not be too different,” she says.

“This composite is a closely-related material with similar strength to PyC because the atoms are arranged similarly, but it’s more lightweight, at least we think, which is a step up in improving the current technology,” she adds.

Adding new skills

Although she previously grew graphene using chemical vapor deposition, growing the carbon nanotubes using a similar chemical vapor deposition process at MIT and making the final nanocomposites requires more steps. “After the CNT growth, I do polymer infusion under vacuum, then the samples are cured in an oven, and then they are pyrolyzed in an even larger furnace. In this way, I’m working on many different pieces of equipment in the lab, which is great experimental experience,” Kaiser says.

Ashley Kaiser 3 MEA Web
Ashley Kaiser prepares to grow carbon nanotubes [CNTs] on a silicon wafer with a coating of alumina and iron in a 1-inch furnace. Alumina and iron act as catalysts to stimulate the CNTs to grow. During her summer project in the Wardle lab, Kaiser grew pyrolytic carbon as a control in addition to growing carbon nanotubes, turning out 5 samples of each at a time. Photo, Maria E. Aglietti.

Although she has previous experience with Raman spectroscopy at UMass and from her 2015 summer internship at 3M, she is learning new characterization skills at MIT this summer, including SEM [scanning electron microscopy], FTIR [Fourier Transform Infrared Spectroscopy], XRD [X-ray Diffraction] and SAXS [Small Angle X-ray Scattering]. “I think that’s going to be really beneficial experience moving forward into graduate work,” she suggests.

Diamond-like structure

“The overarching goal is to study the impact of carbon nanotube confinement on the graphitic crystallites that comprise the pyrolytic carbon, or the matrix of our nanocomposites,” Kaiser explains. “We are finding that as our temperature is increasing, our material is evolving, and it’s forming essentially a lower density pyrolytic carbon which may be more diamond-like, and very strong. We are interested in examining how the nanotubes are affecting the carbon matrix crystallite growth in the composite at various processing temperatures. If this material can be processed to maintain high strength while becoming even lighter, it could be an ideal candidate for aerospace applications.

“I’m essentially doing all the processing, characterization and analysis on my own, so I’m really very solo on this project. I have about 50 robust samples to fabricate and analyze over the course of my summer internship here at MIT,” Kaiser explains. “I’m definitely quite busy with that, but I’m very excited about it at the same time.”

MPC‬‬‬‬‬‪‬‬‬‬ and ‪CMSE‬‬‬ sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from ‪NSF‬‬‬’s Materials Research Science and Engineering Centers program (grant number DMR-14-19807).‬ The program runs from June 7 through Aug. 6, 2016.‬‬‬‬‬ ‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬

 

Denis Paiste, Materials Processing Center | July 27, 2016

Tuesday, 13 February 2018 14:54

Alexandra Barth

Summer Scholar Alexandra Barth analyzes carbon monoxide resistance of core-shell nanoparticle catalysts in the Román Lab.

Alexandra Barth 3 MEA Web
MPC-CMSE Summer Scholar Alexandra Barth works at a hood where she makes carbide core-platinum shell nanoparticles for electrocatalytic applications such as fuel cells and electrolyzers in the lab of MIT Associate Professor of Chemical Engineering Yuriy Román-Leshkov. The process of making core-shell nanoparticles consists of many steps and takes three to five days to complete. Photo, Maria E. Aglietti, Materials Processing Center.

In May the group of MIT Associate Professor of Chemical Engineering Yuriy Román-Leshkov published a study showing that an ultra-thin shell of platinum on a carbide core could catalyze hydrogen evolution and oxidation reactions as effectively as pure platinum at a fraction of the cost. MPC-CMSE Summer Scholar Alexandra T. Barth is helping to advance this work by studying the tunability of these core-shell materials and their performance in a number of electrocatalytic applications.

“What’s been interesting is we found even when we’re creating nanoparticles that are just coated with an atomically thin layer of platinum, they act as effectively as conventional platinum-only nanoparticle catalysts,” Barth explains.

Platinum is a key component in many traditional and emerging technologies, including automobile catalytic converters, oil reforming, fuel cells and electrolyzers. The goal of the project, Dr. Maria Milina, a postdoctoral associate in the Román group explains, is to design noble metal catalysts with significantly reduced metal loadings but improved activity and stability. “We tackle this challenge through the synthesis of core-shell nanoparticles, in which a cheap metal carbide core not only reduces the requirements for expensive platinum but also beneficially modifies its electronic properties,” says Milina.

Avoiding carbon monoxide poisoning

The research of Prof. Román shows that platinum-coated carbide nanoparticles can be used as catalysts for hydrogen evolution and hydrogen oxidation reactions that occur at the cathode of water electrolyzers and at the anode of fuel cells, respectively. Simultaneously they demonstrate remarkable resistance to carbon monoxide, a common catalyst poison. “You want to create a catalyst that will activate hydrogen even when carbon monoxide is present in fuel streams,” Barth says. Carbon monoxide is known to bind strongly to platinum and to block its ability to catalyze other reactions. “Metal carbide cores favorably modulate electronic properties of platinum through subsurface strain and ligand effect leading to the reduced carbon monoxide binding energy of platinum in a core-shell architecture,” explains Prof. Román.

Barth, a rising senior from Florida State University, is interning in the Román lab at MIT this summer. She is synthesizing core-shell nanoparticles with varying core and shell composition, examining their structure with techniques such as infrared spectroscopy and powder X-ray diffraction, and conducting electrocatalytic experiments to analyze their performance in hydrogen evolution/hydrogen oxidation reactions.

A multistep process

The process of making core-shell nanoparticles consists of many steps and takes three to five days to complete, Barth notes. “It’s interesting because the entire process was devised in this lab, so it’s like nothing that’s been done before,” she says. The process involves synthesizing the nanoparticles in a reverse microemulsion, heating the sample in a methane atmosphere to produce a carbide core, and separating the nanoparticles from their silica templates simultaneously dispersing them on a high surface area carbon support in a diluted hydrofluoric acid. The last step in the process, working with hydrofluoric acid, required special safety training.

After synthesis, Barth tests the core-shell nanoparticle catalyst in a three-electrode electrochemical cell. “We initially determine the hydrogen evolution and oxidation activity of the catalysts in a pure hydrogen atmosphere. Then we intentionally introduce carbon monoxide poison into the hydrogen stream and record how quickly catalyst deactivates and how high is the overpotential required to strip carbon monoxide from the platinum surface,” she says.

Infrared spectroscopy challenge

While characterization of solids by X-ray diffraction was a familiar skill from her work at FSU, Barth was facing a challenge with infrared spectroscopy. “We know what we’re expecting of this analysis. I firstly need to record a spectrum of a reduced in hydrogen catalyst, then I should saturate it with carbon monoxide and, after removal of physisorbed species, register another spectrum with the absorbances corresponding to platinum-carbon monoxide interactions. But the use of infrared spectroscopy for carbon-supported catalysts has been always a challenge due to the high opacity of these materials. So that’s been a work in progress,” she says.

“Back at FSU, I do radiochemistry research, so I make crystals with nuclear elements,” she explains. “This is out of my comfort zone because I’ve never done nanoparticle research before, and I’ve never done catalysis research before. But what I have realized through doing this summer project is that I could advance my current research at FSU by including new catalytic studies.” Barth is considering modifying her honors thesis to bridge radiochemistry and catalysis, taking her work from just making crystals to testing their catalytic properties.

Barth is pursuing a major in chemistry at Florida State and hopes to pursue a doctorate in inorganic chemistry.

‪MPC‬‬‬‬‬‪‬‬‬‬‬‬‬‬‬‬‬‬ and ‪CMSE‬‬‬‬‬‬ sponsor the nine-week National Science Foundation Research Experience for Undergraduates (NSF REU) internships with support from ‪NSF‬‬‬‬‬‬’s Materials Research Science and Engineering Centers program (grant number DMR-14-19807).‬ The program runs from June 7 through Aug. 6, 2016.‬‬‬‬‬ ‬‬‬‬

 – Denis Paiste, Materials Processing Center | July 27, 2016

 

Merger of the Materials Processing Center and the Center for Materials Science and Engineering melds a rich history of materials science and engineering breakthroughs.
MRL Director Carl V Thompson 9321 DP Web
MIT MRL Director Carl V. Thompson. Photo, Denis Paiste, MIT MRL.

The Materials Research Laboratory at MIT starts from a foundation of fundamental scientific research, practical engineering applications, educational outreach and shared experimental facilities laid by its merger partners, the Materials Processing Center and the Center for Materials Science and Engineering.

“We’re bringing them together and that will make communication both inside and outside MIT easier and will make it clearer especially to people outside MIT that for interdisciplinary research on materials, this is the place to learn about it,” says MRL Director Carl V. Thompson.

The Materials Research Laboratory serves interdisciplinary groups of faculty researchers, spanning the spectrum of basic scientific discovery through engineering applications and entrepreneurship to ensure that research breakthroughs have impact on society. The center engages with approximately 150 faculty members and scientists from across the Schools of Science and Engineering who are conducting materials science research. MRL will work with MIT.nano to enhance the toolset available for groundbreaking research as well as collaborate with the MIT Innovation Initiative and The Engine.

MRL will benefit from the long history of research breakthroughs under MPC and CMSE such as “perfect mirror” technology developed through CMSE in 1998 that led to a new kind of fiber optic surgery and a spinout company, OmniGuide Surgical, and the first germanium laser operating at room temperature, which is used for optical communications, in 2012 through MPC’s affiliated Microphotonics Center.

The Materials Processing Center brings to the partnership its wide diversity of materials research, funded by industry, foundations and government agencies, while the Center for Materials Science and Engineering brings its seed projects in basic science and Interdisciplinary Research Groups, educational outreach and shared experimental facilities, funded under the National Science Foundation Materials Research Science and Engineering Center program [NSF-MRSEC]. Combined research funding was $21.5 million for the fiscal year ended June 30, 2017.

MPC’s research volume more than doubled during the past nine years under Thompson’s leadership. “We do have a higher profile in the community both internal as well as external. We developed over the years a close collaboration with CMSE, including outreach. That will be greatly amplified through the merger,” he says. Thompson is the Stavros Salapatas Professor of Materials Science and Engineering at MIT.

Tackling energy problems

With industrial support, MPC and CMSE launched the Substrate Engineering Lab in 2004. MPC affiliates include the AIM Photonics Academy, the Center for Integrated Quantum Materials and the MIT Skoltech Center for Electrochemical Energy Storage. Other research includes Professor ‪Harry L. Tuller’s‬‬‬‬ Chemomechanics of Far-From-Equilibrium Interfaces (COFFEI) project, which aims to produce better oxide-based semiconductor materials for fuel cells, and ‬‬‬‬‬‬‬Senior Research Scientist Jurgen Michel’s Micro-Scale Optimized Solar-Cell Arrays with Integrated Concentration (MOSAIC) project, which aims to achieve overall efficiency of greater than 30 percent. ‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬

The MPC kicked off the Singapore-MIT Alliance for Research and Technology Center’s program in Low Energy Electronic Systems [SMART-LEES] in January 2012, managing the MIT part of the budget. SMART-LEES, led by Eugene A. Fitzgerald, the Merton C. Flemings-SMA Professor of Materials Science and Engineering at MIT, was renewed for another five years in January 2017.

Shared experimental facilities, including X-Ray diffraction, scanning and transmission electron microscopy, probe microscopy, and surface analytical capabilities, are used by more than 1,100 individuals each year. “The amount of investment that needs to be made to keep state-of-the-art shared facilities at a university like MIT is on the order of 1 to 2 million dollars per year in new investment and new tools. That kind of funding is very difficult to get. It certainly doesn’t come to us through just NSF funding,” says TDK Professor of Polymer Materials Science and Engineering Michael F. Rubner, who is retiring after 16 years as CMSE director. “MIT.nano, in concert with MRL, will be able to work together to look at new strategies for trying to maintain state-of-the-art equipment and to find funding sources and to figure out ways to not only get the equipment in, but to have highly trained professionals running that equipment.”

Associate Professor of Materials Science and Engineering Geoffrey S.D. Beach succeeds Rubner as co-director of the MIT MRL and principal investigator for the NSF-MRSEC.

Spinning out jobs

Merton Flemings Merger 8974 DP MIT MRL
Merton C. Flemings, founding director [1980-82] of MIT Materials Processing Center and retired Toyota Professor of Materials Processing. Photo, Denis Paiste, MIT MRL.

NSF-MRSEC-funded research through CMSE has led to approximately 1,100 new jobs through spinouts such as American Superconductor [superconductivity], OmniGuide Surgical [optical fibers] and QD Vision [quantum dots], which Samsung acquired in 2016. Many of these innovations began with seed funding, CMSE’s earliest stage of support, and evolved through joint efforts with MPC, such as microphotonics research that began with a seed grant in 1993, followed by Interdisciplinary Research Group funding a year later. In 1997, MIT researchers published two key papers in Nature and Physical Review Letters, won a two-year, multi-university award through DARPA for Photonic Crystal Engineering, and formed the Microphotonics Center. Further research led to the spinout in 2002 of Luminus Devices, which specializes in solid-state lighting based on light emitting diodes [LEDs].

“Our greatest legacy is bringing people together to produce fundamental new science, and then allowing those researchers to explore that new science in ways that may be beneficial to society, as well as to develop new technologies and launch companies,” Rubner says. He recalls that research in complex photonic crystal structures began with Francis Wright Davis Professor of Physics John D. Joannopoulos as leader. “They got funding through us, at first as seed funding and then IRG [interdisciplinary research group] funding, and over the years, they have continued to get funding from us because they evolved. They would seek a new direction, and one of the new directions they evolved into was this idea of making photonic fibers, so they went from photonic crystals to photonic fibers and that led to, for example, the launching of OmniGuide.” An outgrowth of basic CMSE research, the company’s founders included Professors Joannopolous, Yoel Fink, and Edwin L. [“Ned”] Thomas, who served as William and Stephanie Sick Dean of the George R. Brown School of Engineering at Rice University from 2011 to 2017.

Under Fink’s leadership, that work evolved into Advanced Functional Fabrics of America [AFFOA], a public-private Manufacturing Innovation Institute devoted to creating and bringing to market revolutionary fibers and textiles. The institute, which is a separate nonprofit organization, is led by Fink, while MIT on-campus research is led by Lammot du Pont Professor of Chemical Engineering Gregory C. Rutledge.

Susan D. Dalton, NSF-MRSEC Assistant Director, recalls the evolution of perfect mirror technology into life-saving new fiber optic surgery. “From an administrator’s point of view,” Dalton says, “it’s really exciting because day to day, things happen that you don’t know are going to happen. When you think about saving people’s lives, that’s amazing, and that’s just one example,” she says.

Government, industry partners

Through its Collegium and close partnership with the MIT‪ Industrial Liaison Program (‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬ILP), MPC has a long history of government and industrial partnerships as well as individual faculty research projects. Merton C. Flemings, who is MPC’s founding director [1980-82], and a retired Toyota Professor of Materials Processing, recalls that the early focus was primarily on metallurgy, but ceramics work also was important. “It’s gone way beyond that, and it’s a delight to see what’s going on,” he notes.‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬

“From the time of initiation of the MPC, we had interdepartmental participation, and quite soon after its formation, we initiated an industrial collegium to share in research formulation and participate in research partnerships. I believe our collegium was the first to work collaboratively with the Industrial Liaison Program. It was also at a period in MIT history when working directly with the commercial sector was rare,” Flemings says.

Founded in February 1980, the Materials Processing Center won early support from NASA, which was interested in processing materials in space. A question being asked then was: “What would it be like when you’re in zero gravity and you try and purify a metal or make anything out there? Dr. John R. Carruthers headed this zero gravity materials processing activity in NASA, and as he considered the problem, he realized we didn’t really have much of a science base of materials processing on earth, let alone in space. With that in mind, at Carruthers’ instigation, NASA provided a very generous continuing grant to MIT that was essential to us starting in those early years,” Flemings explains.

Carruthers went on to become director of research with Intel and is now Distinguished Professor of Physics, at Portland [Oregon] State University. The two men – Flemings at MIT and Carruthers at the University of Toronto – had been familiar with each other’s work in the study of how metals solidify, before Carruthers joined NASA as director of its materials processing in space program in 1977. Both Flemings and Carruthers wanted to understand how the effects of gravitationally driven convection influenced the segregation processes during metals solidification.

John Carruthers Merger MIT MRL
Dr. John R. Carruthers headed zero gravity materials processing activity in NASA, and provided critical early funding for MIT Materials Processing Center. Courtesy photo.

“In molten metal baths, as the metal solidifies into ingots, the solidification process is never uniform. And so the distribution of the components being solidified is very much affected by fluid flow or convection in the molten metal,” Carruthers explains. “We were both interested in what would happen if you could actually turn gravity down because most of the convective effects were influenced by density gradients in the metal due to thermal and compositional effects. So, we were quite interested in what would happen given that those density gradients existed, if you could actually turn the effects of gravity down.”

“When the NASA program came around, they wanted to try to use the low gravity environment of space to actually fabricate materials,” Carruthers recalls. “After a couple of years at NASA, I was able to secure some block grant funding for the center. It subsequently, of course, has developed its own legs and outgrown any of the initial funding that we provided, which is really great to see, and it’s a tribute to the MIT way of doing research, of course, as well. I was really quite proud to be part of the early development of the center,” Carruthers says. “Many of the things we learned in those days are relevant to other areas. I’m finding a lot of knowledge and way of doing things is transferrable to the biomedical sciences, for example, so I’ve become quiet interested in helping to develop things like nanomonitors, you know, more materials science-oriented approaches for the biomedical sciences.”

Expanding research portfolio

From its beginnings in metals processing with NASA support, MPC evolved into a multi-faceted center with diverse sponsors of research in energy harvesting, conversion and storage; fuel cells; quantum materials and spintronics; materials integration for microsystems; photonic devices and systems; materials systems and sustainability; solid-state ionics; as well as metals processing, an old topic that is hot again.

MRL-affiliated MIT condensed matter physicists include experimentalists Raymond C. Ashoori, Joseph G. Checkelsky, Nuh Gedik, and Pablo Jarillo-Herrero, who are exploring quantum materials for next-generation electronics, such as spintronics and valleytronics, new forms of nanoscale magnetism, and graphene-based optoelectronic devices. Riccardo Comin explores electronic phases in quantum materials. Theorists Liang Fu and Senthil Todadri envision new forms of random access memory, Majorana fermions for quantum computing, and unusual magnetic materials such as quantum spin liquids.

In the realm of biophysics, Associate Professor Jeff Gore tests fundamental ideas of theoretical ecology and evolutionary dynamics through experimental studies of microbial communities. Class of 1922 Career Development Assistant Professor Ibrahim Cissé uses physical techniques that visualize weak and transient biological interactions to study emergent phenomena in live cells with single molecule sensitivity. On the theoretical front, Professor Thomas D. & Virginia W. Cabot Career Development Associate Professor of Physics Jeremy England focuses on structure, function, and evolution in the sub-cellular biophysical realm.

Alan Taub, Professor of Materials Science and Engineering at the University of Michigan, has become a member of the new Materials Research Laboratory External Advisory Board. Taub previously served in senior materials science management roles with General Motors, Ford Motor Co. and General Electric and served as chairman of the Materials Processing Center Advisory Board from 2001-2006. He notes that under Director Lionel Kimerling [1993-2008], MPC embraced the new area of photonics. “That transition was really well done,” Taub says. The MRL-affiliated Microphotonics Center has produced collaborative roadmapping reports since 2007 to guide manufacturing research and address systems requirements for networks that fully exploit the power of photonics. Taub also is chief technical officer of LIFT Manufacturing Innovation Institute, in which MIT Assistant Professor of Materials Science and Engineering Elsa Olivetti and senior research scientist Randolph E. [Randy] Kirchain are engaged in cost modeling.

From its founding, Taub notes, MPC engaged the faculty with industry. Advisory board members often sponsored research as well as offering advice. “So it was really the way to guide the general direction, you know, teach them that there are things industry needs. And remember, this was the era well before entrepreneurism. It really was the interface to the Fortune 500’s and guiding and transitioning the technology out of MIT. That’s why I think it survived changes in technology focus, because at its core, it was interfacing industry needs with the research capabilities at the Institute,” Taub says.

Alan Taub Merger MIT MRL
Alan Taub, Professor of Materials Science and Engineering at the University of Michigan, has become a member of the new Materials Research Laboratory External Advisory Board. Courtesy photo.

Broadening participation

Susan Rosevear, who is the Education Officer for the NSF-MRSEC, is responsible for an extensive array of programs, including the Summer Scholars program, which is primarily funded through NSF’s Research Experience for Undergraduates (REU) program. Each summer a dozen or so top undergraduates from across the country spend about two months at MIT as lab interns working with professors, postdocs and graduate students on cutting edge research.

CMSE also conducts summer programs for community college students and teachers, middle and high school teachers, and participates in the Women’s Technology Program and Boston Area Girls' STEM Collaborative. “Because diversity is also part of our mission, part of what our mission from NSF is, in all we do, we try to broaden participation in science and engineering,” Rosevear says.

Teachers who participate in these programs often note how collaborative the research enterprise is at MIT, Rosevear notes. Several have replaced cookbook-style labs with open-ended projects that let students experience original research.

Confidence to test ideas

Merrimack [N.H.] High School chemistry teacher Sean Müller first participated in the Research Experience for Teachers program in 2000. “Through my experiences with the RET program, I have learned how to ‘run a research group’ consisting of my students. Without this experience, I would not have had the confidence to allow my students to research, develop, and test their original ideas. This has also allowed me to coach our school’s Science Olympiad team to six consecutive state titles, to mentor a set of students that developed a mini bio-diesel processor that they sold to Turner Biodiesel, and to mentor another set of students that took second place in Embedded Systems at I.S.E.F. [Intel International Science and Engineering Fair] last year for their ChemiCube chemical dispensing system,” Müller says.

Müller says he is always looking for new ideas and researching older ideas to develop lab activities in his classroom. “One year my students made light emitting thin films. We have grown beautiful bismuth crystals in our test furnace, and currently I am working out how to make glow-in-the-dark zinc sulfide electroluminescent by doping it with copper so that we can make our own electroluminescent panels,” he says. “Next year we are going to try to make the clear see-through wood that was in the news earlier this year. I am also bringing in new materials that they have not seen before such as gallium-indium eutectic. These novel materials and activities generate a very high level of enthusiasm and interest in my students, and students that are excited, interested, and motivated learn more efficiently and more effectively.”

Müller developed a relationship with Prof. Steve Leeb that has brought Müller back to MIT during past summers to present a brief background in polymer chemistry, supplemented by hands-on demonstrations and activities, for the Science Teacher Enrichment Program (STEP) and Women’s Technology program. “Last year I showed them how they could use their cell phone and a polarized film to see the different areas of crystallization in polymers when they are stressed,” Müller says. “I enjoy the presentation because it is more of a conversation with all of the teachers, myself included, asking questions about different activities and methods and discussing what has worked and what has not worked in the past.” 

Conducive environment

Looking back on his nine years as MPC director, Thompson says, “The MPC served a broad community, but many people at MIT didn’t know about it because it was in the basement of Building 12. So one of the things that I wanted to do was raise the profile of MPC so people better understood what the MPC did in order to better serve the community.” MPC rolled out a new logo and developed a higher profile Web page, for example. “I think that was successful. I think many more people understand who we are and what we do and that enables us to do more,” Thompson says. In 2014 MPC moved to Building 24 as the old Building 12 was razed to make way for MIT.nano. The new MRL is consolidating its offices in Building 13.

“Research breakthroughs by their very nature are hard to predict, but what we can do is we can create an environment that leads to research breakthroughs,” Thompson says. “The successful model in both MPC and CMSE is to bring together people interested in materials, but with different disciplinary backgrounds. We’ve done that separately, we’ll do it together, and the expectation is that we’ll do it even more effectively.”

 – Denis Paiste, Materials Research Laboratory
October 10, 2017
Updated January 25, 2018

Tuesday, 23 January 2018 15:51

A new approach to rechargeable batteries

New metal-mesh membrane could solve longstanding problems and lead to inexpensive power storage.

MIT Battery Membranes PRESS Web

A type of battery first invented nearly five decades ago could catapult to the forefront of energy storage technologies, thanks to a new finding by researchers at MIT and other institutions. Illustration modified from an original image by Felice Frankel

A type of battery first invented nearly five decades ago could catapult to the forefront of energy storage technologies, thanks to a new finding by researchers at MIT. The battery, based on electrodes made of sodium and nickel chloride and using a new type of metal mesh membrane, could be used for grid-scale installations to make intermittent power sources such as wind and solar capable of delivering reliable baseload electricity.

The findings are being reported in the journal Nature Energy, by a team led by MIT professor Donald Sadoway, postdocs Huayi Yin and Brice Chung, and four others.

Although the basic battery chemistry the team used, based on a liquid sodium electrode material, was first described in 1968, the concept never caught on as a practical approach because of one significant drawback: It required the use of a thin membrane to separate its molten components, and the only known material with the needed properties for that membrane was a brittle and fragile ceramic. These paper-thin membranes made the batteries too easily damaged in real-world operating conditions, so apart from a few specialized industrial applications, the system has never been widely implemented.

But Sadoway and his team took a different approach, realizing that the functions of that membrane could instead be performed by a specially coated metal mesh, a much stronger and more flexible material that could stand up to the rigors of use in industrial-scale storage systems.

“I consider this a breakthrough,” Sadoway says, because for the first time in five decades, this type of battery — whose advantages include cheap, abundant raw materials, very safe operational characteristics, and an ability to go through many charge-discharge cycles without degradation — could finally become practical.

While some companies have continued to make liquid-sodium batteries for specialized uses, “the cost was kept high because of the fragility of the ceramic membranes,” says Sadoway, the John F. Elliott Professor of Materials Chemistry. “Nobody’s really been able to make that process work,” including GE, which spent nearly 10 years working on the technology before abandoning the project.

As Sadoway and his team explored various options for the different components in a molten-metal-based battery, they were surprised by the results of one of their tests using lead compounds. “We opened the cell and found droplets” inside the test chamber, which “would have to have been droplets of molten lead,” he says. But instead of acting as a membrane, as expected, the compound material “was acting as an electrode,” actively taking part in the battery’s electrochemical reaction.

“That really opened our eyes to a completely different technology,” he says. The membrane had performed its role — selectively allowing certain molecules to pass through while blocking others — in an entirely different way, using its electrical properties rather than the typical mechanical sorting based on the sizes of pores in the material.

In the end, after experimenting with various compounds, the team found that an ordinary steel mesh coated with a solution of titanium nitride could perform all the functions of the previously used ceramic membranes, but without the brittleness and fragility. The results could make possible a whole family of inexpensive and durable materials practical for large-scale rechargeable batteries.

The use of the new type of membrane can be applied to a wide variety of molten-electrode battery chemistries, he says, and opens up new avenues for battery design. “The fact that you can build a sodium-sulfur type of battery, or a sodium/nickel-chloride type of battery, without resorting to the use of fragile, brittle ceramic — that changes everything,” he says.

The work could lead to inexpensive batteries large enough to make intermittent, renewable power sources practical for grid-scale storage, and the same underlying technology could have other applications as well, such as for some kinds of metal production, Sadoway says.

Sadoway cautions that such batteries would not be suitable for some major uses, such as cars or phones. Their strong point is in large, fixed installations where cost is paramount, but size and weight are not, such as utility-scale load leveling. In those applications, inexpensive battery technology could potentially enable a much greater percentage of intermittent renewable energy sources to take the place of baseload, always-available power sources, which are now dominated by fossil fuels.

The research team included Fei Chen, a visiting scientist from Wuhan University of Technology; Nobuyuki Tanaka, a visiting scientist from the Japan Atomic Energy Agency; MIT research scientist Takanari Ouchi; and postdocs Huayi Yin, Brice Chung, and Ji Zhao. The work was supported by the French oil company Total S.A.

back to newsletterDavid L. Chandler | MIT News Office
January 22, 2018

Approach could bypass the time-consuming steps currently needed to test new photovoltaic materials.
MIT Assessing PVs Web
This experimental setup was used by the team to measure the electrical output of a sample of solar cell material, under controlled conditions of varying temperature and illumination. The data from those tests was then used as the basis for computer modeling using statistical methods to predict the overall performance of the material in real-world operating conditions. Image, Riley Brandt

The worldwide quest by researchers to find better, more efficient materials for tomorrow’s solar panels is usually slow and painstaking. Researchers typically must produce lab samples — which are often composed of multiple layers of different materials bonded together — for extensive testing.

Now, a team at MIT and other institutions has come up with a way to bypass such expensive and time-consuming fabrication and testing, allowing for a rapid screening of far more variations than would be practical through the traditional approach.

The new process could not only speed up the search for new formulations, but also do a more accurate job of predicting their performance, explains Rachel Kurchin, an MIT graduate student and co-author of a paper describing the new process that appears this week in the journal Joule. Traditional methods “often require you to make a specialized sample, but that differs from an actual cell and may not be fully representative” of a real solar cell’s performance, she says.

For example, typical testing methods show the behavior of the “majority carriers,” the predominant particles or vacancies whose movement produces an electric current through a material. But in the case of photovoltaic (PV) materials, Kurchin explains, it is actually the minority carriers — those that are far less abundant in the material — that are the limiting factor in a device’s overall efficiency, and those are much more difficult to measure. In addition, typical procedures only measure the flow of current in one set of directions — within the plane of a thin-film material — whereas it’s up-down flow that is actually harnessed in a working solar cell. In many materials, that flow can be “drastically different,” making it critical to understand in order to properly characterize the material, she says.

“Historically, the rate of new materials development is slow — typically 10 to 25 years,” says Tonio Buonassisi, an associate professor of mechanical engineering at MIT and senior author of the paper. “One of the things that makes the process slow is the long time it takes to troubleshoot early-stage prototype devices,” he says. “Performing characterization takes time — sometimes weeks or months — and the measurements do not always have the necessary sensitivity to determine the root cause of any problems.”

So, Buonassisi says, “the bottom line is, if we want to accelerate the pace of new materials development, it is imperative that we figure out faster and more accurate ways to troubleshoot our early-stage materials and prototype devices.” And that’s what the team has now accomplished. They have developed a set of tools that can be used to make accurate, rapid assessments of proposed materials, using a series of relatively simple lab tests combined with computer modeling of the physical properties of the material itself, as well as additional modeling based on a statistical method known as Bayesian inference.

The system involves making a simple test device, then measuring its current output under different levels of illumination and different voltages, to quantify exactly how the performance varies under these changing conditions. These values are then used to refine the statistical model.

“After we acquire many current-voltage measurements [of the sample] at different temperatures and illumination intensities, we need to figure out what combination of materials and interface variables make the best fit with our set of measurements,” Buonassisi explains. “Representing each parameter as a probability distribution allows us to account for experimental uncertainty, and it also allows us to suss out which parameters are covarying.”

The Bayesian inference process allows the estimates of each parameter to be updated based on each new measurement, gradually refining the estimates and homing in ever closer to the precise answer, he says.

In seeking a combination of materials for a particular kind of application, Kurchin says, “we put in all these materials properties and interface properties, and it will tell you what the output will look like.”

The system is simple enough that, even for materials that have been less well-characterized in the lab, “we’re still able to run this without tremendous computer overhead.” And, Kurchin says, making use of the computational tools to screen possible materials will be increasingly useful because “lab equipment has gotten more expensive, and computers have gotten cheaper. This method allows you to minimize your use of complicated lab equipment.”

The basic methodology, Buonassisi says, could be applied to a wide variety of different materials evaluations, not just solar cells — in fact, it may apply to any system that involves a computer model for the output of an experimental measurement. “For example, this approach excels in figuring out which material or interface property might be limiting performance, even for complex stacks of materials like batteries, thermoelectric devices, or composites used in tennis shoes or airplane wings.” And, he adds, “It is especially useful for early-stage research, where many things might be going wrong at once.”

Going forward, he says, “our vision is to link up this fast characterization method with the faster materials and device synthesis methods we’ve developed in our lab.” Ultimately, he says, “I’m very hopeful the combination of high-throughput computing, automation, and machine learning will help us accelerate the rate of novel materials development by more than a factor of five. This could be transformative, bringing the timelines for new materials-science discoveries down from 20 years to about three to five years.”

The research team also included Riley Brandt '11, SM '13, PhD '16; former postdoc Vera Steinmann; MIT graduate student Daniil Kitchaev and visiting professor Gerbrand Ceder, Chris Roat at Google Inc.; and Sergiu Levcenco and Thomas Unold at Hemholz Zentrum in Berlin. The work was supported by a Google Faculty Research Award, the U.S. Department of Energy, and a Total research grant.

David L. Chandler | MIT News Office
December 20, 2017

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