When Tyrel McQueen taps the computer controls on the hulking blue-and-white steel furnace, there is a pocketa, pocketa sound as a high-capacity compressor pressurizes the device’s containment vessel with argon gas, and it chirps as blindingly hot xenon bulbs spark to life.
Working in the bunker-like basement of the Bloomberg Center for Physics and Astronomy, McQueen, associate professor, and his colleague, Adam Phelan, an associate research scientist, have spent months fine-tuning the commercial refrigerator-sized furnace, a one-of-a-kind instrument for growing ultrapure crystals of materials that have never been made before.
They are assembling one of the most advanced materials-fabrication labs in the world, preparing to blaze a trail for the creation of smaller, lighter, tougher, safer, more efficient and durable stuff.
Chasing the Science of Stuff
Tyrel McQueen, the director of the new PARADIM materials fabrication lab, has long been fascinated by the science of stuff.
During his junior and senior years in high school in Idaho, he was captain of the school’s Department of Energy’s Science Bowl team, traveling to Washington for the annual competitions. As an undergraduate at Harvey Mudd College near Los Angeles, he loaded up on courses in physics, chemistry, and math. In graduate school he started off studying theoretical chemistry, but after six months decided to s
witch back to the bench.
“I realized that after about six months, if I wasn’t doing things in a lab I was going to be bored out of my mind,” he says.
Today, he holds associate professor positions in three Hopkins departments: physics and astronomy, materials science and engineering, and chemistry.
As a chemist, he says, he hopes he brings more “intuition” to the physics side of chemistry—meaning an understanding of a physical phenomena beyond the math and formula-based descriptions of how materials behave at the subatomic level. At the same time, he says because of his mathematics training he can bring “more math rigor” to the chemistry side of his work.
His main area of research is quantum materials, a field as challenging as it is promising. While classical Newtonian physics governs the world we can see, touch, taste and smell, the quantum realm, which underlies our own, plays by a completely different set of rules.
It’s a world where every particle exists as both a discrete chunk of matter in a specific place and as a smear of potential states and locations. It’s a world that seemingly defies the limits imposed by the speed of light on our world, under some circumstances allowing two particles to communicate instantly over any given distance. In this realm, merely to measure something is to profoundly affect it.
Another major focus of McQueen’s research is superconductors. Normally, electrons moving through a solid bounce off atoms of the stuff or each other. That causes resistance, which generates heat and wastes energy. The colder a conductor gets, the better it conducts electricity. When sufficiently cooled, some conductors become “superconductors” and their resistance falls to
zero.
The electrons stop streaming through a material and pair off, beginning what McQueen calls a kind of waltz. “It’s like a room full of people dancing and never hitting each other,” he says. Newtonian physics can’t account for this. The dance of the electrons is another weird property of the quantum mechanical world.
High-temperature superconductors are already being used in machines like MRIs, power grids and cell tower transmitters and receivers. But “high” in this case typically means about as warm as a very cold day in Antarctica.
One of the holy grails of materials science is the discovery of a room temperature superconductor that could rewire our world. “That would be a game changer,” he says.
Things haven’t always gone so smoothly. After only a few uses, the furnace’s original solid sapphire chamber for growing crystals shattered explosively and wrecked the xenon bulb, delicate mirrors, and almost all of the interior hardware. It took months to reengineer and rebuild, and then the instrument was shut down for a week or so by a software glitch.
But by late last April the furnace was up and running, as two aluminum oxide rods resembling ivory chopsticks—one hanging above the other—melted at the tips, creating a small white-hot shaft of molten aluminum oxide in the gap. As the whitish ceramic cooled, it created a single crystal of the test material.
McQueen, wearing shorts and a Hawaiian shirt, adjusted the instrument’s touch-screen controls while watching a live video feed transmitted from inside the cabinet. Now the name of the game was patience, nursing the crystals as they grew at a rate of about a millimeter an hour. With some materials, growing a pure crystal can take up to three days. “You do have to pay very close attention,” he says.
The Hopkins PARADIM (Platform for the Accelerated Realization, Analysis and Discovery of Interface Materials) lab, being built with a $4.8 million National Science Foundation (NSF) grant, is an integral part of an effort by the United States to regain its former leadership in making the raw materials for building tomorrow’s technologies. It’s a field that until recently the United States had largely abandoned to other industrialized nations.
Reviving U.S. Leadership in Materials Science
For most of the 20th century, the United States led the world in the synthesis of new materials, ranging from the carbon fiber now being used to make the bodies of luxury autos to the single-crystal superalloys in jet engine turbines.
Major universities like Hopkins joined the research divisions of U.S. corporate giants in exploring the frontiers of the material world. Scientists at AT&T’s fabled Bell Labs didn’t just invent the floating-zone furnace technique for producing ultra-pure silicon chips, they developed the chip-based transistors that made modern computing possible.
About a quarter-century ago, the leadership in materials research began shifting overseas. Partly because, says Tyrel McQueen, director of the Hopkins’ PARADIM crystal growth lab, U.S. corporations couldn’t figure out how to capitalize on their own discoveries. While scientists at Bell Labs invented the transistor, companies like Intel and Microsoft reaped the profits decades later.
Partly, he says, the problem lay in academia, where scientists tended to regard solid state chemistry as a field where all the major questions had been answered. “We have not been at the forefront of new materials discovery in the United States, because for a long time you could not get tenure at a U.S. institution by doing solid state chemistry,” he says. “Why? Because it was viewed as a solved problem.”
Today Germany and Japan are the leaders in materials discovery. In 1962, American scientists patented the first practical light-emitting diode. But it only emitted dim infrared light. A Japanese team won the 2014 Nobel Prize in physics for their contribution to the development of much brighter blue LEDs, which was rapidly followed by the development of white ones.
Now the federal government, in partnership with major universities, is trying to revive the U.S. leadership in the field.
Hopkins has long been among the leaders. Edwin Hall discovered the “Hall effect,” a measure of resistance in materials, during graduate work at Hopkins in 1879. Others developed titanium-based paints, designed a mass spectrometer for studying the chemistry of Mars, and synthesized saccharine and acetaminophen.
“There is an incredible history of materials science developed by folks at Hopkins,” McQueen says. Currently, he estimates, almost a quarter of the Homewood campus’ more than 500 faculty members are engaged in some kind of materials-related work, in places like the Hopkins Extreme Materials Institute, the Institute for Quantum Matter and the Institute for Nanobiotechnology.
McQueen says the PARADIM lab will help Hopkins remain a leader in materials discovery. “This is the only place in the world that has this capability,” he says. “This is what lets us make materials that no one else can make.”
Meanwhile the demand for advanced materials has surged, thanks to the world’s voracious appetite for faster computers, clearer communications, and cheaper, cleaner energy sources. New materials may one day multiply the battery life of cell phones, laptops, drones, and automobiles. They could make it possible to cram all of today’s computing power worldwide into a device that could fit in the palm of your hand.
Today, McQueen says, there are about 50 million known chemical compounds, nearly all of them organic compounds developed by biomedical researchers. But there may be billions, or trillions, of new combinations of the hundred-odd chemical elements in the periodic table just waiting to be discovered.
“Existing materials have been studied to death. What we’re doing has never been done before. Even the mistakes we’ve made in the furnace have never been made before.”
The PARADIM program is part of the federal government’s Materials Genome Initiative, launched in 2011. The initiative is focused on rebuilding U.S. capacity to invent and manufacture new materials, with the aim of doubling the speed and slashing the costs of innovation in the field. So far, a host of federal agencies have spent half-a-billion dollars on the push.
With its advanced materials fabrication technology and scientific expertise, McQueen says, the Hopkins PARADIM lab is preparing to make a major contribution to those efforts. More than a dozen research groups have applied to use the Hopkins lab for academic research, and one corporation is already using it for commercial work.
The aim isn’t to help improve the performance of known materials by a factor of two or three. It’s to build new materials that could extend the life of batteries, for example, by a factor of ten thousand.”
Tyrel McQueen
Other groups at Johns Hopkins are sharing resources or facilities with PARADIM. They include the Department of Energy-funded Institute for Quantum Matter; the Maryland Advanced Research Computing Center, or MARCC, which runs a supercomputer jointly owned with the University of Maryland and located on Hopkins’ Bayview Campus; and the Hopkins Institute for Data Intensive Engineering and Science, or IDIES.
PARADIM will be the best-equipped lab of its kind in the world, McQueen says, rivaled only by the Leibniz Center for Crystal Growth and Technical University in Berlin. The aim isn’t to help improve the performance of known materials by a factor of two or three. It’s to build new materials that could extend the life of batteries, for example, by a factor of ten thousand.
The goal is to help take materials science into areas “where we don’t understand the system,” he says. “We’re making materials that are going to power the next revolution in our standard of living.”
Partners in PARADIM
Phelan, a PhD and associate director of the Hopkins PARADIM lab, came to Baltimore from the hills of Arkansas by way of Louisiana State University. In his office across the hall from the lab, he adopts a pained smile when asked how he explains his work to non-scientists. To the lay public, he says, chemistry means scientists in white coats mixing bubbling liquids in beakers. They sometimes draw a blank, he says, when he explains that he works on inventing new solid materials.
“The world we live in is made up of solids—watches, cell phones, and hybrid vehicles,” he says. And new devices often require novel materials to make them work.
He reels off some important recent developments in the field. Scientists have discovered iron arsenides, a new class of high-temperature superconductors, materials that carry a current with zero resistance. New compounds called organo-halides, meanwhile, could make solar cells a lot cheaper to produce.
Bismuth selenide is a rare “topological insulator,” meaning that it conducts electricity on its surface but not on the inside. That’s a very strange behavior, and researchers are only starting to explore what the applications might be.
A major aim of the Hopkins PARADIM lab is to produce new bulk materials to serve as the foundation, or substrate, for advanced computer chips. Clark Atlanta University is providing theoretical support, and Princeton will direct the program. Cornell is engaged in the research and development of new thin film coatings for the base materials developed at Hopkins.
The NSF established the lab to serve as a platform for collaborative research, and to further that goal McQueen and Phelan launched a summer school for materials science here. Last July about 20 graduate students, postdocs, junior faculty, and industry scientists from around the world arrived at Hopkins for the one-week course, with morning lectures by more than a dozen senior scientists, and afternoons and evenings growing materials.
During the first summer school in 2016, the focus was on frontiers in crystal growth and design, while in 2017 the subject was topological insulators. Physicists and materials scientists from Rutgers, MIT, and Germany’s Max Planck Institute for Solid State Research gave presentations.
Over the next 10 years, PARADIM’s chief objective is to help develop new transistors that use so-called “valleytronics.” Current transistor materials allow only one “off” setting, or minimum level of energy, McQueen says.
A valleytronic transistor would have a range of these minimum energy levels, called valleys, and could in theory be used to build far faster and smaller switches. That would boost the efficiency of a host of electronic devices. “We’re something like a billion times less efficient than we could be,” he says. “There’s a lot of area for improvement there.”
The PARADIM lab’s array of equipment also includes a machine called a spark plasma sintering instrument, which uses heat and pressure to fuse submicroscopic nanoparticles together without melting them. Another high temperature precision furnace, which resembles a transparent grandfather clock, transforms 50-kilowatts of electricity—enough to power a small American neighborhood—into radio waves that can melt steel like wax.
Last spring, the lab took delivery of another cutting-edge instrument: a tilting laser diode optical floating zone furnace, made in Japan. By precisely aiming the device’s five lasers, McQueen says, operators will be able to control crystal growth at the atomic scale.
The lab’s equipment can be temperamental. Tiny flaws in the design of the sapphire chamber in the SciDre high-pressure optical floating zone furnace, built by Germany’s Scientific Instruments Dresden, caused it to fail catastrophically in mid-February 2017. The sound of the explosion, which said was louder than a gunshot at close range, echoed through the cavernous basement of Bloomberg Hall. Thanks to SciDre’s armored cabinet, there was no external damage and no one was hurt.
The process by which SciDre makes crystals is roughly analogous to the process for making rock candy. Rock candy is made by boiling water, pouring in sugar until the liquid is saturated and watching crystals form on strings as the water cools. Instead of boiling water, SciDre uses oxygen or argon gas under tremendous pressure. Instead of temperatures of a few hundred degrees, it generates temperatures of over 5,400 degrees Fahrenheit—about half those on the surface of the Sun. And instead of rock candy, it can make crystal compounds out of a host of chemical elements, including nickel, iridium, and gold.
“What are the things we can do with this that you can’t do anywhere else in the world?” McQueen says, referring to the SciDre furnace. “Well, take gold oxide. Gold usually can’t form oxides. But under these kind of conditions you can make gold oxides that have never been made anywhere before.”
The floating zone crystal-growing technique, pioneered by Bell Labs in the 1950s, melts small blocks of material arranged vertically and gradually cools the molten material to form crystals. Furnace operators rely on surface tension to hold the material in place while in its molten state. (Surface tension is the elastic property of liquids that, for example, allows insects to walk across the surface of a pond.)
SciDre’s sapphire containment vessel is used to isolate the space where top- and bottom-mirrors focus the intense heat generated by two high-powered xenon lamps, similar to those used in movie projectors.
The furnace’s single crystal sapphire containment is a cylinder about the size of a coffee can. It is sealed and connected to twin high-efficiency pumps, originally designed for the fracking industry, which can pressurize gases up to 300 times atmospheric pressure. That’s 4,400 pounds per square inch, or about the same crushing pressure as the ocean exerts at a depth of 10,000 feet.
Originally, McQueen says, he hoped to help design and build a new instrument capable of monitoring the structure of crystals as they were being formed, at scales as small as about 10,000 atoms across. He envisioned something akin to a computerized tomography scanner, the medical imaging device, but one adapted to monitor crystal growth.
But he’s delayed the project for a couple of years until the technology advances. ”It turns out to be a very difficult engineering feat,” he says. “At some point, you realize the fundamental laws of nature are against you.”
It’s only a temporary setback, he says. The frontiers of materials science are quickly expanding, driven by discoveries in physics and chemistry. Solutions to the mysteries of the material world are increasingly within reach. “From my perspective, we’re in a sort of golden age, where it is possible to carve out an intuitive and understandable explanation of the world,” he says.
