Experience

National Institute of Standards and Technology

Research Staff • Gaithersburg, MD • July 2017 — Present

Developing thermodynamic and kinetic models of precipitate particle evolution and equilibrium in ternary alloys analogous to nickel-based superalloys.

National Institute of Standards and Technology

NRC Postdoctoral Associate • Gaithersburg, MD • July 2015 — June 2017

Implemented phase field model for solid-state transformation in alloy systems with three components and four phases, analogous to Inconel 625. Designed initial conditions based on electron micrographs of additively manufactured Inconel 625 to simulate microstructure evolution during heat treatment. Produced thermodynamic models through simplification of quantitative CALPHAD databases while retaining key phase diagram features, using computer algebra systems to accurately generate expressions and multivariable derivatives for import into phase field software.

Materials Science and Engineering Department, Rensselaer Polytechnic Institute

Graduate Assistant: Kinetics of Materials • Autumn 2012 and Spring 2015

Graduate Teaching Assistant: Materials Science for Engineers • Autumn 2014

Hosted well-attended office hours to review lecture material, clarify assignment questions and concepts, and answer questions. As graduate TA, taught bi-weekly laboratory and weekly recitation covering homework and exam solutions. Ferreted out plagiarists.

Veeco Instruments • Solar Process Development Center

Process Engineer, part time • Clifton Park, NY • July 2009 — August 2011

Researched non-toxic alternatives to CdS, reporting to senior management. Traveled to Helsinki, Finland to evaluate state-of-the-art atomic layer deposition reactor.

DayStar Technologies • Materials Development Group

Process Engineer • Clifton Park, NY • January 2009 — June 2009

Process Engineer • Clifton Park, NY • July 2006 — December 2008

Researched alternatives to chemical bath deposition of CdS thin films, including nontoxic materials and novel reactor geometries. Achieved 72× scaleup in CdS deposition area with only 6× increase in waste generation.

Skills

Scientific Computing

  • Parallel programming: OpenMP, MPI-2/MPI-IO, POSIX threads
  • Debugging: gdb, gprof, Valgrind
  • Version control: git, GitHub, branching workflows
  • Data management: mdadm (RAID1, RAID5, RAID6), rdiff-backup, rsnapshot
  • Cluster management: Ansible, Ganglia, NFS

Experimental Techniques

  • Metallographic polishing and etching: Fe-, Cr-, Cu-, Zn-, and Ni-based alloys
  • Scanning electron microscopy (SEM) of inorganic specimens
  • X-ray diffractometry
  • UV-visible light spectrophotometry
  • Contact profilometry of thin films

Education

Rensselaer Polytechnic Institute

Doctor of Philosophy, Materials Engineering • Troy, NY • 2011 — 2015

Thesis: "Bias in Polycrystal Topology Caused by Grain Boundary Motion by Mean Curvature."

Performed large-scale phase field simulations of normal isotropic grain growth on high performance computing clusters including AMOS, an IBM Blue Gene/Q supercomputer. Designed and implemented algorithms to reconstruct polyhedral grain topology (faces, edges, and vertices) from diffuse interfaces in 2D and 3D phase field datasets. Found the process of triangular face elimination responsible for biasing topology in populations of polyhedral grains in synthetic, simulated, and real metal microstructures.

Master of Science, Materials Engineering • Troy, NY • 2009 — 2011

Thesis: "Effects of Magnesium(II) on Zinc Oxide Nanorod Growth From Aqueous Solution."

Designed experiments to deposit ZnO on glass substrates using a novel flow-through aqueous chemical reactor under various combinations of temperature, pH, reactant concentrations, and flow rate. Found minor effects of Mg2+ ions on ZnO film stress and lattice parameters.

Bachelor of Science, Chemical Engineering • Troy, NY • 2002 — 2006

Projects

The Carpentries

Certified Instructor • September 2018 — Present

Trained to demonstrate and teach best practices in software development and data analysis using the framework created and maintained by the international Carpentries community. Taught a minimum of one lesson per year.

Mesoscale Microstructure Simulation Project (MMSP)

Software Developer • January 2013 — Present

MMSP is an open source library for phase-field and kinetic Monte Carlo simulations written in C++ with MPI. Invited to join project as co-developer based on contributed patches to eliminate memory leaks and resolve race conditions in parallel computing environments. Eliminated corruption in parallel I/O on large-block filesystems, enabling clean execution of phase field and kinetic Monte Carlo research simulations on IBM Blue Gene/Q supercomputers with up to 4096 cores. Implemented testing of proposed source code changes through automatic online continuous integration.

Refereed Publications

  • T. Keller, G. Lindwall, S. Ghosh, L. Ma, B. Lane, F. Zhang, U. Kattner, J. Heigel, E. Lass, Y. Idell, M. Williams, A. Allen, J. Guyer, and L. Levine. "Application of finite element, phase-field, and CALPHAD-based methods to additive manufacturing of Ni alloys." Acta Materialia 139 (2017) 244—253. DOI: 10.1016/j.actamat.2017.05.003.
  • T. Keller, B. Cutler, E. Lazar, and D. Lewis. "Comparative grain topology." Acta Materialia 66 (2014) 414—423. DOI: 10.1016/j.actamat.2013.11.039.
  • T. Keller, B. Cutler, M. Glicksman, and D. Lewis. "Enumeration of polyhedra for grain growth analysis." In Proceedings of the First International Conference on 3D Materials Science (3DMS’12), Seven Springs, PA, July 8—12, 2012, pages 97—106.

Presentations*

  • T. Keller (invited), G. Lindwall, U. Kattner, and J. Guyer. "Abstraction, acceleration, and analysis: Integrating CALPHAD and phase-field models for AM superalloys." SIAM Conference on Mathematical Aspects of Materials Science. Portland, OR: July 9, 2018.
  • T. Keller, G. Lindwall, U. Kattner, and J. Guyer. "Reversion in ternary alloys using phase-field and CALPHAD methods." TMS Annual Meeting. Phoenix, AZ: March 20, 2018.
  • T. Keller. "HiPerC: High performance computing strategies for boundary value problems." CHiMaD Phase Field Workshop VI. Northwestern University: February 21, 2018.
  • T. Keller, G. Lindwall, U. Kattner, and J. Guyer. "Pitfalls of modeling additively manufactured materials: Case study with Inconel 625." NIST MML MSED Baglunch. Gaithersburg, MD: October 11, 2017.
  • T. Keller (invited). "Mesoscale modeling of solid state reactions: Pathways toward microstructure design." Lawrence Livermore National Laboratory. Livermore, CA: April 12, 2017.
  • T. Keller, G. Lindwall, U. Kattner, and J. Guyer. "Pitfalls of modeling additively manufactured materials: Case study with Inconel 625." TMS Annual Meeting. San Diego, CA: February 28, 2017.
  • T. Keller, G. Lindwall, U. Kattner, and J. Guyer. "Arresting deleterious particle growth in Inconel 625: Phase field model description." MS&T Annual Meeting. Salt Lake City, UT: October 27, 2016.
  • T. Keller (invited), B. Cutler, and D. Lewis. "Finite grain boundary networks from phase-field grain growth data." NIST Material Science & Engineering Division. Gaithersburg, MD: December 8, 2014.
  • T. Keller, B. Cutler, and D. Lewis (invited). "Comparative analysis of polycrystals in simulated & experimental datasets." MS&T Annual Meeting. Pittsburgh, PA: October 15, 2014.
  • T. Keller, D. Crist, D. Lewis, Y. Tan, K. Huang, and C. Li. "Realtime prediction of grain growth during materials processing." PICS3. Marseille, France: May 2014.
  • T. Keller and D. Lewis. "Topological characterization of 3D microstructures with diffuse interfaces." TMS Annual Meeting. San Diego, CA: February 19, 2014.
  • T. Keller, D. Lewis, B. Cutler, and E. Lazar. "Topological comparison of synthetic microstructures." MS&T Annual Meeting. Montreal, QC, Canada: October 28, 2013.
  • T. Keller, D. Lewis, B. Cutler, B. Yener, S. Rock, G. Saunders, and M. Muench. "The topology of polycrystals." PICS3. Marseille, France: July 2013.
  • T. Keller, B. Cutler, G. Yauney, and D. Lewis. "Topological analysis of collapsing grains." MS&T Annual Meeting. Pittsburgh, PA: October 10, 2012.
  • T. Keller, B. Cutler, G. Yauney, and D. Lewis. "Polyhedral graphs & grain topology." International Conference on 3-Dimensional Materials Science (3DMS). Seven Springs, PA: July 11, 2012.

*Presenter's name is underlined.

Posters*

  • T. Keller and D. Lewis. "Trijunction drag affects grain topology." NIST Chapter of Sigma Xi, Annual Postdoctoral Poster Session. Gaithersburg, MD: February 19, 2016.
  • T. Keller and D. Lewis. "Grain topology from 3D phase-field simulations." Eastern New York Chapter of ASM International, Spring Symposium. Troy, NY: November 18, 2014.
  • T. Keller, B. Cutler, G. Yauney, and D. Lewis. "Grain topologies in synthetic, simulated, and real microstructures." Rensselaer Moves into Petascale Computing: Celebration & Workshop. Troy, NY: October 3, 2013.
  • T. Keller, B. Cutler, G. Yauney, and D. Lewis. "Topological distributions in synthetic microstructures and grains." 8th International Conference on Porous Metals and Metallic Foams (MetFoam). Raleigh, NC: June 23-26, 2013.
  • D. Lewis, G. Saunders, S. Rock, T. Keller, J. Mao, M. Muench, J. Symons, D. Hoffman, M. Oullette, and C. LaBarre. "Development of an automated serial sectioning system." CATS/CEG Advanced Manufacturing Conference. Troy, NY: April 22, 2013.
  • T. Keller, G. Yauney, B. Cutler, and D. Lewis. "Grain populations in topological space." Eastern New York Chapter of ASM International, Spring Symposium. Troy, NY: December 5, 2012.

*Presenter's name is underlined.

Recognition

National Institute of Standards and Technology

MML Accolade • 2018

Acta Materialia

Outstanding Reviewer Award • 2017

International Conference on Porous Metals and Metallic Foams (MetFoam)

2nd Place Poster Award • 2013

Professional Development

CHiMaD Phase Field Working Group

Workshop VII • September 25—27, 2018

Workshop VI • February 20—22, 2018

Workshop V • August 1—3, 2017

Workshop IV & Installathon • January 17—20, 2017

Workshop III & Hackathon II • May 3—5, 2016

Workshop II & Hackathon I • October 13—16, 2016

Active participant in time-limited coding activities and discussions of progress toward a "community code" for phase field simulations.

NIST Women in STEM

STEM Role Model Training • November 29, 2016

Meal with a Mentor • June 28, 2016

Active participant in one-on-one, group, and panel discussions with high school, undergraduate, and graduate students on the pursuit of careers in STEM.

Software Carpentry

Instructor of"Automatic Version Control with Git" at NIST • September 11, 2018

Student at NIST Instructor Training • April 2—3, 2018

Student at NIST Workshop • September 23—24, 2015

Worked through exercises in common scientific software tools and learned the finer points of teaching such tools to fellow researchers.

IIMEC Summer School

Computational Materials Science Across Scales • June 2—11, 2014

Lecture topics included density functional theory, molecular dynamics, thermodynamics, phase-field models, and continuum mechanics. Equal coverage of theory and numerical exercises in collaborative workshops.

Society for Industrial and Applied Mathematics (SIAM)

Member in good standing • 2014 — Present

Project Links