This Instrumentation and Facilities award through the NSF Division of Earth Sciences will support acquisition of a high-precision, single-crystal X-ray diffractometer to carry out topical geomaterials research and education in the Department of Earth and Planetary Sciences (EPS) at Northwestern University. X-ray diffraction allows definitive identification of minerals at the grain-size scale and determination of crystal structures and related physical properties of materials in the crust-mantle system. This instrument will be interfaced with the PI?s unique high-pressure ultrasonic system for basic mineral physics research on thermodynamic equations of state for Earth and planetary materials.
The instrument will be installed in the new EPS Integrated Laboratories of Northwestern (EPSILoN), a new interdisciplinary research and graduate training facility with five adjoining laboratories for mineralogy/mineral physics, stable isotope geochemistry, organic geochemistry, and sedimentary and aqueous geochemistry. Basic research in the PI?s laboratory, currently supported by the faculty early career development program (CAREER) seeks to understand the role of water cycling between the crust and mantle from atomic to geophysical scales. New knowledge of the effects of hydration on the structure and elasticity of mantle materials is applied to remote (geophysical) detection of water in the deep mantle. In addition, the instrument will serve broader departmental and regional needs for specialized mineral phase analysis, characterization, and applied laboratory instruction for undergraduate and graduate courses in Earth materials at Northwestern. Research with the proposed diffractometer has broader impacts as the PI engages in technology transfer between high-pressure geosciences and applied materials research.
This NSF Instrumentation and Facilities award through EAR supported the acquisition of a high-precision, single-crystal X-ray diffractometer to carry out topical geomaterials research and education in the department of Earth and planetary sciences at Northwestern University. X-ray diffraction allows definitive identification of minerals at the grain-size scale and determination of crystal structures and related physical properties of materials in the crust-mantle system. This particular instrument interfaces with the PI’s unique high-pressure ultrasonic system for fundamental mineral physics research on the physical properties of Earth and planetary materials. The field of mineral physics deals with the materials science of geophysical processes. Unlike other laboratory X-ray diffraction systems at Northwestern and in the region, this instrument is customized for use with high-pressure and high-temperature diamond-anvil cells. By measuring, for example, the lattice spacing of atoms in crystals as a function of pressure and temperature, researchers can obtain the mineral’s equation of state, which relates density, pressure, and temperature. These measurements facilitate geophysical (remote) interpretation of Earth’s constitution; especially the composition and mineralogy of the inaccessible interior beyond direct observation or drilling. The team at Northwestern is focused on the role of volatiles on mineral behavior. Volatiles, such as hydrogen and carbon, are incorporated into crystal structures at high pressures and temperatures and strongly influence the physical properties of Earth materials, which can be studied with the instrument developed here. These studies will lead to a better understanding of hydrogen and carbon geochemical cycles between the Earth’s crust and mantle. Experimentally measured equations of state for hydrated mantle minerals will be combined with geophysical observations from seismology to interpret the amount and distribution of water in the Earth’s mantle. Here, water does not refer to liquid water, but the hydrogen and oxygen components of water, dissolved into crystal structures. This X-ray diffraction system is especially capable of detecting the changes in lattice parameters on hydration or dehydration, which are used to infer the hydration state of Earth’s interior. Hydration of the Earth’s mantle influences geophysical processes ranging from convection to gas-driven dynamic volcanism at the surface. Beyond studying the physical properties of Earth and planetary materials, the instrument is being used to investigate the physical properties of novel materials for industry. For example, the addition of boron to diamond results in semi-conducting properties. Measuring changes in the lattice parameters of diamond with varying boron content is critical to understanding how its physical properties might be optimized for semi-conducting applications. The Northwestern group is also using the instrument to study changes in the diamond structure as both boron and nitrogen are added; the so-called B-C-N materials have hardness rivaling diamond, but improved thermal properties over diamond. These and other applications to material science broaden the scope of this instrument beyond Earth science. Technology transfer between high-pressure geosciences and applied materials research is one of the PI’s primary research interests. The PI enganges in education and outreach at all levels. As a member of Northwestern’s Project Excite team, Center for Talent Development, he teaches 3-4th graders after-school Earth science courses aimed at closing the enrollment gap of minority students in advanced placement science and mathematics courses at Evanston Township High School in Evanston. Jacobsen also serves on the ad-hoc Education and Outreach Committee of the NSF-COMPRES consortium. As a centerpiece instrument in the mineral physics laboratory at Northwestern, undergraduates, graduate students, and postdoctoral researchers are being trained in the science and art of X-ray diffraction, and here they are developing specialized skills in high-pressure diffraction. These employable skills will apply to their future pursuit of jobs in academia or industry, as X-ray diffraction is a common tool to nearly every branch of materials research from basic chemistry and physics to biology, materials science and geology. The instrument acquired under this award is used in several courses at Northwestern in hands-on laboratory exercises, and the PI opens up the laboratory for tours to dozens of outside visitors every year including K-12 students, parents, and curious members of the community who find unusual rocks and minerals in their backyard and want to know; what is it?
