Karl D. Hammond
Karl D. Hammond, Associate Professor
Biomedical, Biological & Chemical Engineering
Karl Hammond is an associate professor in the Department of Biomedical, Biological and Chemical Engineering at the University of Missouri and is involved in the Nuclear Engineering Program. His research focuses on topics in catalysis and materials science relevant to the production and utilization of energy. His research group uses tools from computational chemistry and physics combined with insights from experimental characterization to study adsorption and transport in porous materials, such as zeolites; damage in metals due to irridation; simulation of plasma-facing and fusion-relevant materials; and the role of impurities and defects in catalysis and materials science. His work potentially influences chemical separations, biomass-derived fuels, membrane separations processes, plasma devices and nuclear fusion reactors.
- PhD from the University of Massachusetts-Amherst
- BS from the California Institute of Technology
Computational materials science
Plasma-facing materials/nuclear fusion materials
Hammond Research Group
The Hammond research group uses a combination of computational modeling and experimental characterization to study materials that have energy applications. This includes adsorption, transport, separations, and catalysis using zeolite-like materials for both “traditional” and “renewable” fuels (such as biomass-derived molecules) as well as radiation damage to materials in nuclear reactors (some in fission reactors, but primarily in experimental fusion reactors and plasma devices).
Our primary aim is to use computational techniques in tandem with experiments to achieve a better understanding of the underlying physical and chemical processes involved. This might mean direct investigation of a reaction or diffusion mechanism, or it may involve a series of calculations that, when viewed as a whole, paint a picture of the process from the atomic scale all the way up to entire device.
The truly inspiring aspect of computational materials science and catalysis research is an atomic-scale understanding of physical and chemical processes that is impossible using purely experimental means. Simulations also provide feedback as to what the next set of experiments should be; similarly, that set of experiments often provides a direction for the next set of simulations, and so on.
My group conducts research in materials for nuclear energy, catalysis, adsorption, and other energy-related applications. Particular focus is given to simulation of materials for plasma-facing environments, including nuclear fusion reactors; transport and radiation damage in materials, including simulations of nuclear fission reactor fuels; catalytic and adsorption processes in zeolites and other porous materials; characterization of materials; and modeling and simulation of porous materials.
Nuclear fusion is the source of all energy we utilize today. Unfortunately, the best reactors to produce energy from nuclear fusion are, well, a little bulky.
The nearest one to us, for example, has a mass of almost 2 × 1030 kg and produces 400 YW (4 × 1026 W) of power (you might know it as the Sun). Clearly, this gravitationally confined environment is not feasible on Earth, so we have had to get more clever.
Instead, humans have envisioned inertial confinement reactors, in which high-power lasers focus onto a very small sample, instantaneously compressing it and starting fusion reactions. Inertial confinement is the basis of the National Ignition Facility in California (pictured at left). Unfortunately, this type of reactor (like all others) has many hurdles to overcome as well.
The third option devised to date is magnetically confined fusion, which is the basis for ITER, a test reactor currently under construction near Cadarache, France. ITER is the culmination of around 50 years of plasma physics research, and is expected to be the first terrestrial fusion reactor to produce more power than is required to heat the plasma for longer than a few seconds. However, the conditions of the plasma in ITER and future magnetic confinement devices are becoming increasingly hostile to the materials from which the device is constructed. These materials challenges may come to dominate research in fusion during the coming years, as we strive to achieve the dream of a terrestrial nuclear fusion reactor.
Recent work in plasma-facing materials has revealed that helium, the product of nuclear fusion, creates many unexpected and/or detrimental phenomena when implanted in metals due to helium plasma exposure. Helium bubbles, in particular, are possible sources of increased hydrogen (specifically tritium) retention, as well as plasma contamination by the divertor material (tungsten). Our work comes in at the microscopic level: we examine the transport processes involved in hydrogen, helium, lithium, and beryllium transport inside the divertor and first wall of the reactor, as well as smaller plasma devices intended as model systems for ITER. Specifically, we wish to determine the interplay between the various reactor materials as they sputter and redeposit on other surfaces, changing the surface and diffusion properties within the metal.
While nuclear fusion holds great promise, it is, at present, impractical as a source of energy for our everyday use. Nuclear fission, on the other hand, provides approximately 20% of electrical energy in the United States and represents approximately 8% of our total energy use annually. Nuclear reactors have the distinct advantage that, once built, they are extremely cheap to operate, and they have excellent safety records: in the USA, accidents at nuclear power facilities have claimed just three lives—ever. In fact, fission power causes fewer deaths per unit of electricity than all other power sources, and most of those deaths are those of miners.
Nuclear reactors, much like cell phone data plans, are generally divided into “generations,” such as “Generation III reactors.” A big part of the progress in nuclear energy is our improved understanding of nuclear reactor physics, particularly how the reactor behaves during disruptions from steady-state in terms of power output and radiation production. Nuclear reactor materials, which include fuel, cladding, and structural materials, are susceptible to damage both from neutrons and the resulting hydrogen they decay into, as well as fission gas production (xenon, krypton) from the fission process and radioactive decay of fission products to produce high-energy electrons (beta particles) and helium nuclei (alpha particles).
My group’s work in this area, supported by a Faculty Development Grant from the Nuclear Regulatory Commission, uses the tools of computational materials science and applied physics to model heat and mass transfer processes in nuclear materials, particularly radiation effects and thermal transient phenomena. We also study the thermodynamics and materials physics of alternative nuclear fuels such as metallic uranium—molybdenum alloys. Our work is in tandem with the Missouri University Research Reactor (MURR), the largest academic research reactor in the country.
Zeolites and Similar Porous and Catalytic Materials
Zeolites are crystalline aluminosilicates that revolutionized the petrochemicals industry when they were introduced into the cracking and refining processes decades ago. The key to this revolution was the small pores zeolites possess: the constrained environment of a zeolite pore either prevents large molecules (e.g., asphalt-range hydrocarbons) from forming, or prevents their diffusion out of the zeolite before they react again.
Zeolite-catalyzed processes typically involve acid sites, another prominent feature of zeolite chemistry: the aluminum atoms, which have trivalent chemistry, create a net negative charge when in the tetravalent sites normally occupied by silicon atoms. This negative formal charge creates a Lewis base site near each aluminum atom. If the compensating cation is hydrogen, the zeolite has net Brønsted acidity. Most zeolites, especially low-aluminum zeolites, are strong acids, making them fairly potent acid catalysts capable of doing size-selective chemistry.
My group’s primary research in zeolites is in their spectroscopic properties. Specifically, we want to be able to predict—quickly and accurately—the infrared spectrum of a zeolite using nothing but computational tools. Sounds simple, right? Except that the vibrations are tightly coupled, the crystals are huge (as simulations go, at least), and the models we have…well…stink. As such, we proceed along all of these fronts, doing DFT-based calculations of periodic structures as a baseline, comparing those to simulations of finite, molecule-like portions of zeolite crystals, and comparing both sets of calculations to faster, though typically less-accurate, models of zeolite vibration.
Another avenue of research in my group is zeolites that have been modified to act as Brønsted bases. Our goal is to find the right combination of crystal structure and Si/Al ratio, combined with treatment procedure and catalytic reaction conditions, which will make nitrided zeolite catalysis a reality. This research is directed toward oxygenated molecules, which are often upgraded by way of base-catalyzed reactions.
K. D. Hammond, I. V. Naeger, W. Widanagamaachchi, L.-T. Lo, D. Maroudas, and B. D. Wirth. “Flux Effects on Helium Bubble Growth and Surface Morphology in Plasma-Facing Tungsten from Large-Scale Molecular Dynamics Simulations.” Nuclear Fusion 59 (6): 066035 (2019).
A. M. Mofrad, C. Peixoto, J. Blumeyer, J. Liu, H. K. Hunt, and K. D. Hammond. “Vibrational Spectroscopy of Sodalite: Theory and Experiments.” Journal of Physical Chemistry C 122 (43): 24765–24779 (2018).
Yang, Z. and K. D. Hammond. “Helium In-Plane Migration Behavior on 〈100〉 Symmetric Tilt Grain Boundaries in Tungsten.” Journal of Physics: Condensed Matter 30 (32): 325002 (2018).
A. A. Saltos, N. J. Peters, and K. D. Hammond. “Thermal Neutron Scattering Cross Sections of 238U and 235U in the γ Phase.” Journal of Physics: Condensed Matter 30 (41): 415401 (2018).
Yang, Z., L. Hu, D. Maroudas, and K. D. Hammond. “Helium Segregation and Transport Behavior Near 〈100〉 and 〈110〉 Symmetric Tilt Grain Boundaries in Tungsten.” Journal of Applied Physics 123 (22): 225104 (2018).
Iasir, A. R. M., N. J. Peters, and K. D. Hammond. “Estimation of the Effective Thermal Conductivity in U-10Mo Fuels with Distributed Xenon Gas Bubbles.” Journal of Nuclear Materials 508: 159–167 (2018).
Guo, J. and K. D. Hammond. “A Potential for the Simulation of Siliceous Zeolites Fit to the Infrared Spectra of Silica Polymorphs.” Journal of Physical Chemistry C 122 (21): 11345–11354 (2018).
Hackett, C. and K. D. Hammond. “Simulating the Effect of the Quadrupole Moment on the Adsorption of Nitrogen in Siliceous Zeolites.” Microporous and Mesoporous Materials 263: 231–235 (2018).
Hammond, K. D.. “Helium, Hydrogen, and Fuzz in Plasma-Facing Materials.” Materials Research Express 4 (10): 104002 (2017). Emerging Investigators in Materials Science special issue
Hammond, K. D., S. Blondel, L. Hu, D. Maroudas, and B. D. Wirth. “Large-Scale Atomistic Simulations of Low-Energy Helium Implantation into Tungsten Single Crystals.” Acta Materialia 144: 561–578 (2018).
Sefta, F., K. D. Hammond, N. Juslin, and B. D. Wirth. “Tungsten Surface Evolution by Helium Bubble Nucleation, Growth, and Rupture.” Nuclear Fusion 53 (7): 073015 (2013).
Dogan, F., K. D. Hammond, G. A. Tompsett, W. C. Conner, S. M. Auerbach, and C. P. Grey. “Searching for Microporous, Strongly Basic Catalysts: Experimental and Calculated 29Si NMR Spectra of Heavily Nitrogen-Doped Y~Zeolites.” Journal of the American Chemical Society 131 (31): 11062–11079 (2009).