Status: 5th year Ph.D. Candidate (Expected Graduation: Summer 2017)
Project: Instrumentation and Measurement of Thermoelectric and Structural Properties of Binary Chalcogenides and Half-Heusler Alloys at Extreme Conditions Using a Paris-Edinburgh Press
Advisor: Dr. Ravhi Kumar & Dr. Andrew Cornelius
- B.S. Physics: UNLV Completed 2008
- M.S. Physics: UNLV Completed 2012
- Thesis Title: Synthesis and High-Pressure Structural Studies of AuX2 (X = Al, Ga, In) Compounds
- Ph.D. Physics: UNLV Expected July 2017
- Dissertation Title: Instrumentation and Measurement of Thermoelectric and Structural Properties of Binary Chalcogenides and Half-Heusler Alloys at Extreme Conditions Using a Paris-Edinburgh Press
Research & Experience
As a Ph.D. student in the High-Pressure Science and Engineering Center (HiPSEC), I have had the opportunity to participate in and design a large variety of static high-pressure, high-temperature, and low-temperature experiments performed at Argonne National Laboratory (ANL) at the Advanced Photon Source (APS), specifically with the High-Pressure Collaborative Access Team (HPCAT) at Sector 16. These total well over 20 separate synchrotron experiments, many of which I acted as the primary experimenter. All of these experiments incorporated high-pressure structural and/or spectroscopic X-ray techniques in order to understand the equation of state (EOS), pressure-induced structural phase transitions, electrical and thermal properties, and phase diagram identification at high-pressure and high-temperature (HPHT) conditions. These measurements required the use of diamond-anvil cells (DACs) as well as the Paris-Edinburgh press, giving me a great deal of experience with preparation and use of these high-pressure tools.
My dissertation research has focused on the design and development of a specialized technique to measure electrical, thermal, and structural properties of materials at extreme conditions. A customized sample cell assembly for use with the Paris-Edinburgh large volume type press to measure electrical resistance, Seebeck coefficient, relative changes in thermal conductivity, and overall thermoelectric efficiency of materials at HPHT conditions alongside the capabilities to probe the structural properties via energy-dispersive X-ray diffraction has been developed for general users at the Sector 16 BM-B beamline as part of HPCAT. This technique has been utilized to understand the thermoelectric behavior of important thermoelectric materials at high-pressure conditions such as PbTe, SnTe, SnSe, TiNiSn, and TiCoSb. The simultaneous measurement capabilities of this apparatus are a powerful tool to understand the correlation between electronic and thermal behavior and structural properties of not only thermoelectric materials, but inherently any compound. In addition to a better understanding of the correlation between electrical, thermal, and structural properties, this technique also is capable of providing valuable experimental methods to validate theoretical modeling of high-pressure and high-temperature properties.
National Labs and Experiments Performed
- Participated in 20+ experiment runs at a variety of beam lines at the Advanced Photon Source (APS) at Argonne National Laboratory and 1 experiment at the Advance Light Source at Lawrence Berkeley National Laboratory. Experience totaling hundreds of hours.
- Performed extensive variety of techniques under static high-pressure conditions, including: powder X-ray diffraction, X-ray absorption spectroscopy, resonant inelastic X-ray scattering, electrical and thermal property measurements
- Internship at Los Alamos National Laboratory, Summer 2012
- Supervisor: Dr. Nenad Velisavljevic
- Responsibilities: Utilized computer software to create 3-D representation of PE cell assembly, aided in design and perform experiments using PE cell at APS, and analyze collected thermal, electrical, and EDXD from PE cell experiments.
- Pre-Doctoral Student, ANL, APS, HPCAT, June 2014
- Supervisor: Dr. Changyong Park
- Responsibilities: Continued design and preparation of customized sample cell assembly for the PE press and using an off-line PE press to perform several test experiments to solve electrical shorting issues encountered during normal beam-time experiments.
- Nenad Velisavljevic – Los Alamos National Laboratory
- Changyong Park – Argonne National Laboratory, HPCAT
- Curtis Kenney-Benson – Argonne National Laboratory, HPCAT
Professional Schools & Workshops
- Paris-Edinburgh Cell Workshop, May 2013. Training was provided for standard sample cell preparation, HPHT generation in the PE cell, ultrasonic velocity measurement, demonstration of falling sphere viscometry, and EDXD data analysis. Talks were given on a variety of topics including: Structure, dynamics and properties of liquids, new developments in PE cell, and user science highlights.
- Malcolm F. Nicol Fellowship Recipient – UNLV, 2012 – 2013
- Outstanding Poster Award at SSAP Symposium – Chicago, IL April 2017
- SCCM/AIRAPT Conference in Seattle, WA – July 2013
In-Situ X-Ray Diffraction, Electrical Resistivity, and Thermal Conductivity Measurements Using a Paris-Edinburgh Cell
- American Physical Society (APS) March Meeting in Baltimore, MD – March 2013
High-Pressure Thermoelectric Measurements Using a Paris-Edinburgh Press
- Invited – Study of Matter at Extreme Conditions (SMEC) Conference, Eastern Caribbean – April 2017
High-Pressure Instrumentation: Thermal and Structural Properties of Half-Heusler Compounds
- Paris-Edinburgh Cell Workshop, Argonne National Laboratory, APS, HPCAT, May 2013
Thermal and Electrical Measurements Using Custom Cell Assembly in Paris-Edinburgh Cell
- Stewardship Science Academic Programs (SSAP) Symposium, Sante Fe, NM, March 2015
High-Pressure Structural, Electrical, and Thermal Measurements of Thermoelectric Compounds
- American Physical Society (APS) March Meeting in Baltimore, MD March 2016
High-Pressure Thermoelectric Measurements Using a Paris-Edinburgh Cell
- SSAP Symposium, Chicago, IL, April 2017
High-Pressure Thermoelectric and Structural Behavior of Half-Heusler Compounds
- High-pressure Seebeck coefficients and thermoelectric behaviors of Bi and PbTe measured using a Paris-Edinburgh cell. Baker, J., Kumar, R., Park, C., Kenney-Benson, C., Cornelius, A. & Velisavljevic, N. Synchrotron Rad. 23, 1368-1378; (2016)
- Pressure induced structural transitions in CuSbS2 and CuSbSe2 thermoelectric compounds. Jason Baker, Ravhi Kumar, Daniel Sneed, Anthony Connolly, Yi Zhang, Nenad Velisavljevic, Jayalakshmi Paladugu, Michael Pravica, Changfeng Chen, Andrew Cornelius, Yusheng Zhao Journal of Alloys and Compounds 643, 186 – 194, (2015).
- High pressure transport and structural studies on Nb3Ga superconductor. Vahe Mkrtcheyan, Ravhi Kumar, Jason Baker, Anthony Connolly, Daniel Antonio, Andrew Cornelius, Yusheng Zhao Physica B: Condensed Matter 459, 21 – 23, (2015).
- In-situ x-ray diffraction, electrical resistivity and thermal measurements using a Paris-Edinburgh cell at HPCAT 16BM-B beamline. Jason Baker, Ravhi Kumar, Nenad Velisavljevic, Changyong Park, Curtis Kenney-Benson, Yoshio Kono, Andrew Cornelius, Yusheng Zhao Journal of Physics: Conference Series 500, 142003, (2014).
- Effect of pressure and temperature on structural stability of MoS2. Nirup Bandaru, Ravhi Kumar, Daniel Sneed, Oliver Tschauner, Jason Baker, Daniel Antonio, Sheng-Nian Luo, Thomas Hartmann, Yusheng Zhao, Rama Venkat Journal of Physical Chemistry C 118 (6), 3230- 3235, (2014).
- Structural stability of WS2 under high pressure. Nirup, Bandaru, Ravhi Kumar, Jason Baker, Oliver Tschauner, Thomas Hartmann, Yusheng Zhao, Rama Venkat International Journal of Modern Physics B 28 (25), 1450168, (2014).
- Pressure induced high spin – low spin transition in FeSe superconductor studied by x-ray emission spectroscopy and ab initio calculations. Ravhi S. Kumar, Yi Zhang, Yuming Xiao, Jason Baker, Andrew Cornelius, Sathishkumar Veeramalai, Paul Chow, Changfeng Chen, Yusheng Zhao Applied Physics Letters 99, 061913, (2011).