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DE-FG02-06ER46291: Phase Transitions in Metastable Multicaloric Materials

Award Status: Active
  • Institution: Board of Trustees Southern Illinois University, Carbondale, IL
  • DUNS: 939007555
  • PM: Kortan, Ahmet Refik
  • Most Recent Award Date: 05/10/2019
  • Number of Support Periods: 14
  • PI: Ali, Naushad
  • Current Budget Period: 07/01/2019 - 06/30/2020
  • Current Project Period: 07/01/2019 - 06/30/2022
  • Supplement Budget Period: N/A

Public Abstract

Phase Transitions in Metastable Multicaloric Materials

Shane Stadler, Louisiana State University (Principle Investigator)

Naushad Ali (PI) and Saikat Talapatra (Co-I), Southern Illinois University


Significant changes in temperature can be induced in some solid-state materials when they are subjected to external stimuli such as strain, pressure, electric fields, or magnetic fields. These solid-state caloric materials will be important in future cooling technologies since they are predicted to be more energy efficient and environmentally friendly than their conventional, vapor-compression-based predecessors. The largest solid-state caloric effects are usually observed in materials that undergo coupled magnetic and structural transitions, or magnetostructural transitions. Magnetostructural transitions are the source of extreme physical phenomena, including solid-state caloric effects, shape memory effects, large magnetoresistance, magnetoelasticity, exchange bias, and giant anomalous Hall effects. In many cases, due to the nature of magnetostructural transitions, two or more of these physical properties may occur in the same material. Such materials are said to be multifunctional, and may have specific multi-function applications in future technologies. It is also possible that a magnetostructural transition simultaneously generates two (or more) types of caloric effects; such materials are called multicaloric materials. Investigating these materials may provide new insights into the mechanisms responsible for the abovementioned phenomena, and may therefore have a significant impact on solid-state physics.

In this collaborative effort between Louisiana State University and Southern Illinois University, we will study phase transitions in three classes of materials with a focus on those that generate magnetic-field-induced (magnetocaloric) effects and pressure-induced (barocaloric) effects near room temperature. First, we will investigate MnTX (T = Ni, Fe, Co, Cu and X = Si, Ge, Sn) multicaloric compounds. When synthesized under high pressure and temperature, some materials form in different structures than when they are produced at atmospheric pressure. A well-known example of such a system is carbon: when it is synthesized at high pressure it forms diamond, rather than in some other form of carbon such as graphite. The high-pressure phase in this case is preserved under ambient conditions and is said to be metastable. One objective of this project is to use high-pressure synthesis and thermal quenching to form metastable high-temperature/pressure phases of MnTX compounds near room temperature, potentially resulting in magnetostructural transitions that generate solid-state cooling properties.

High-entropy alloys (HEAs) are formed by combining five or more elemental constituents in equal atomic ratios, resulting in high mixing entropy and potentially novel physical behaviors. Our second objective is to synthesize new magnetic high-entropy alloys and investigate their phase transitions, and corresponding magnetic and magnetocaloric properties. Our third objective is to explore the effects of carbon (doping and surface coatings) on magnetic transitions in intermetallic and Heusler alloy systems.

The MnTX and HEA materials will be fabricated using conventional melting/quenching techniques, as well as under high pressure conditions (~8 GPa) in a high pressure/temperature furnace. Carbon-incorporated intermetallic materials will be synthesized using conventional melting and chemical vapor deposition (CVD) techniques. All samples will be characterized using magnetometry, transport, thermal, compositional, and structural techniques.

The objectives of this project are the following: (i) to develop new metastable multicaloric MnTX materials, and to understand the underlying physics of the phase transitions in these systems; (ii) to develop new magnetic high-entropy alloys, understand their magnetic properties, and explore magnetocaloric effects at their phase transitions; and (iii) to understand the effects of carbon (including nanotube coatings) on phase transitions in intermetallic alloys.

The scientific outcomes include: (i) the development of new multicaloric and multifunctional materials; (ii) a deeper understanding of the physics of the phase transitions responsible for multicaloric and multifunctional behaviors; and (iii) the discovery of new physical phenomena in metastable alloy phases and high-entropy alloys.  

The discovery of a practical and effective solid-state refrigeration material will lead to more efficient cooling systems. The impact of this could be profound: it would be one step towards energy independence, as this is one of our most energy-demanding technologies. 

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