2021 Highlights

High school student experience: going containerless

2021 Broader Impacts DMR-2015852, CER

Alexandra Navrotsky, Arizona State University

High school senior Nicholas To joined the group in the Summer 2021. Together with ASU undergraduate Ivan Matyushov he assembled acoustic levitator using design published my Marzo et al. (2017).

It uses 3D printed parts made at Makerspace in ASU library, low cost ultrasonic transducers, and Arduino microcontrollers.

With help from Victor Contreras (Instituto de Ciencias Fisicas, Morelos, Mexico) over Zoom, Nicholas and Ivan modified the design and demonstrated acoustic levitation of AI2O3.

Nicholas was admitted as a freshman at ASU majoring in mechanical engineering. He and Ivan continue working in the group as paid undergraduate research assistants preparing the levitator for tests with the laser heating system and diffractometer.

A photo shows Nicholas To demonstrating the acoustic levitator he assembled to Alexandra Navrotsky and another person.

Another photo shows levitation of a 2 mm AI2O3 sphere in the version modified with help from Victor Contreras.

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Ceramics under extreme conditions

2021 Intellectual Merit DMR-2015852, CER

Alexandra Navrotsky, Arizona State University

Aerodynamic levitation with laser heating is currently used for:

  • Drop and catch calorimetry on ceramic samples at ASU.
  • High temperature synchrotron X-ray diffraction at Advanced Photon Source (APS, 6-ID-D, ANL).
  • High temperature neutron diffraction at Spallation Neutron Source (SNS, Nomad, ORNL).

The main limitation of technique is thermal gradient induced in the sample due to laser heating from the top and cooling by levitation gas from the bottom.

Electromagnetic levitation (EML) offers both bulk induction heating and levitation which can be realized from vacuum to hyperbaric conditions for high temperature diffraction and calorimetry.

We demonstrated EML feasibility for ultra-high temperature ceramic (UHTC) materials — refractory carbides, borides and nitrides of transition metals, with electric conductivity.

In collaboration with David Lipke and William Fahrenholtz (Missouri University of Science and Technology), Juergen Brillo (German Aerospace Center), Hiroyuki Fukuyama (Tohoku University, Japan).

One image shows synchrotron diffraction pattern on laser-heated aerodynamically levitated ER2O3 (around 3 mm in diameter).

Another image shows electromagnetically heated and levitated solid ZrC pellet (around 5 mm in diameter).

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Configurational Entropy Stabilizes Crystallographic Shear Structures

Schematic image illustrates how the increase of Nb5+ content decreases the energetic stability of TiNbxO2+2.5x crystallographic shear phases. Source: A. A. Voskanyan, M. Abramchuk, and A. Navrotsky, Chem. Mater., 32, 5301-5308 (2020).

Scientific Achievements

Wadsley-Roth shear phases of TiNbsO7, TiNb5O14.5, and TiNb24O62 are energetically stabilized via configurational entropy contribution.

Significance and Impact

This work accentuates the underlying role of thermodynamic studies in engineering materials with enhanced stability for next-generation lithium-ion batteries.

Research Details

  • Crystallographic shear phases constitute a new and extensive class of “entropy-stabilized oxides.”
  • The thermodynamic stability of Wadsley-Roth homologues increases with the decreasing Nb/Ti molar ratio.
  • TiNb24O62 is much more disordered than TiNb2O7 and TiNb5O14.5 and they are stable at synthesis temperature, metastable at ambient temperature, and TiNb2O7 has the lowest temperature of decomposition.

Work was performed at School of Molecular Sciences, Arizona State University, Tempe, AZ

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