Biography

IMG_efrain


CONTACT INFORMATION


Office Phone: 301-405-1541
Office Address: 4101
 Email: efrain@umd.edu
 Group Website

Assistant Professor

Education

  • B.S. Materials Science and Engineering, 2003 Massachusetts Institute of Technology
  • Ph.D. Materials, University of California Santa Barbara (with Anthony K. Cheetham, FRS)
  • National Research Council Post-doctoral Fellow, NIST Center for Neutron Research, National Institute of Standards and Technology (with Mark A. Green)

Professional Experience

  • Graduate Researcher, 2004-2009, Materials Research Lab, UCSB
  • Post-baccalaureate intern, 2003, and Graduate Research Assistant, 2007-2009, Lujan Neutron Center, Los Alamos National Laboratory

 Research Interests

Materials and solid state chemistry. Inorganic materials. Synthesis and characterization of transition metal (TM) compounds including oxides, chalcogenides and pnictides. Preparation of metastable materials for energy applications via chemie douce, or soft chemical, methods. Functional TM compounds with properties such as magnetic, electronic, and mixed conductivity (ionic and electrical). Advanced characterization of compounds including X-ray and neutron diffraction coupled with magnetization and electrical transport measurements

Major Recognitions and Honors

  • NSF Integrative Graduate Education and Research Traineeship (IGERT) research fellowship, UCSB, 2004-2006
  • National Research Council Post-doctoral Fellow
  • Selected to participate at the 58th Annual Meeting of Nobel Laureates in Lindau, Germany
  • Graduate School Research and Scholarship Award
  • NSF CAREER Award, 2015-2020
  • Office of Naval Research, MURI on Superconductivity, 2015-2020

 Significant Professional Service and Activities

  • Faculty Co-Advisor of the American Chemical Society Club
  • Co-organizer of the first ever Neutron Day at the University of Maryland, 2014
  • Mentor to Beckman Scholar and ASPIRE (www.aspire.umd.edu) undergraduate researchers, 2013-2015
  • Organizer of the following symposia: ACS National Meeting 2015 Synthetic Chemistry Approaches to Magnetic Materials, American Crystallographic Association Meeting 2015 Materials Discovery and Crystal Growth

Research

We are a solid state chemistry laboratory interested in preparing functional inorganic materials and studying their structures and dynamics with X-ray and neutron scattering. We focus on magnetism, superconductivity, and energy conversion materials.

Magnetism and correlated electron behavior in microporous oxides

Our goal is to prepare new metal oxides with microporous and mesoporous structures, some of which are known from naturally occurring minerals such as hollandite and todorokite. The 1D channels are constructed purely of edge-sharing MO6 octahedra where M is a transition metal and cations such as K+ and Ba2+ reside in those channels. We have focused on Mn-based oxides for magnetic properties, Ti-based oxides for catalytic and energy storage applications, and V-based oxides for electrical transport properties such as metal-to-insulator transitions. The hollandite-type structure is especially versatile and can readily accommodate several members of the transition metal series, which allows for facile doping to tune the electronic and magnetic properties.

rodriguez figure 1

Late transition metal chalcogenides with “Hund metallicity”

Inspired by our past work on iron-based superconductors, our goal is to prepare new two-dimensional and three dimensional chalcogenides of the late transition metals (iron, cobalt, and nickel) for manipulating charge, spin, and orbital degrees of freedom. In all of our compounds, we are focused on materials that are either metallic or semimetallic, and where some d-orbitals exhibit localized behavior while others itinerant. Hund’s coupling between the two sets leads to a new way of understanding magnetism in these metals. In all of these chalcogenides, the M2+ ions are in tetrahedral coordination, and those MCh4 tetrahedra are edge-sharing. For the 2D materials, we are primarily interested in how to build new

Rodriguez figure 2 2015heterostructures to manipulate the magnetism and superconducting properties. For the 3D materials, we are interested in the fundamental interactions between the magnetism and itinerant electrons. In all cases, we are looking to find new synthetic routes towards new materials and single crystal growth.

 

Anion manipulation of transition metal oxides and in-situ diffraction studies

Our goal is to perform soft chemistry on oxides to manipulate their anionic structure. Ultimately, we would like to understand the criteria that lead to either anion substitution or complete anion removal during reactions such as reductive de-intercalation with electropositive metal hydrides or other reducing environments. We perform in-situ studies with neutrons and synchrotron X-rays to understand these topochemical reactions. Some time-dependent diffraction experiments at the Advanced Photon Source on our oxides under a methane gas stream can have time resolution of down to 5 seconds, allowing us to find metastable states of such oxides. Potential applications include chemical looping cycles for combustion of fuels and tuning of magnetic properties via anion manipulation.

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