NOTE: End date changed to 9/30/2024 per NSSC information (Ed., 3/5/24)

NOTE: End date changed to 9/30/2023 per NSSC information (Ed., 6/20/23)

NOTE: End date changed to 9/30/2022 per M. Sansoucie/MSFC (Ed., 1/28/21)

June 2019: Note project had preliminary work performed Feb-August 2019

Reference: [1] S. Kohara, et al., “The origin of fragility in high-temperature oxide liquids - towards fabrication of novel non-equilibrium oxides,” JAXA flight project funded in 2017.

• Determine the structure of a non-conventional glass forming system based on a titanium dioxide network forming component. • Measure the density, thermal expansion coefficient, surface tension and viscosity of normal and supercooled liquids. • Investigate the properties of several glasses made in microgravity. • Measure the optical properties of rare earth doped glasses. • Publish and present results prior to uploading them to the NASA Physical Sciences Informatics (PSI) database. • Upload data from this work to the PSI system. • File two patents on glass materials made in reduced gravity. These are being pursued in commercial activities.

NOTE: End date changed to 9/30/2024 per NSSC information (Ed., 3/5/24)

NOTE: End date changed to 9/30/2023 per NSSC information (Ed., 6/20/23)

NOTE: End date changed to 9/30/2022 per M. Sansoucie/MSFC (Ed., 1/28/21)

June 2019: Note project had preliminary work performed Feb-August 2019

Reference: [1] S. Kohara, et al., “The origin of fragility in high-temperature oxide liquids - towards fabrication of novel non-equilibrium oxides,” JAXA flight project funded in 2017.

1. STATUS:

The project team includes Dr. Stephen Wilke; Mr. Abdulrahman Al-Rubkhi and Mr. Jared Rafferty from Materials Development Inc. (MDI); Dr. Shinji Kohara, National Institute for Materials Science, Japan; and Dr. Takehiko Ishikawa, Japanese Aerospace Exploration Agency (JAXA), Japan. The collaborators from Japan are not funded from this grant. The funded project work was completed in 2025. Some final in-progress publication edits are being completed. Data are being uploaded to the NASA Physical Sciences Informatics (PSI) system.

2. TECHNICAL ACTIVITIES:

Activities during the reporting period included: (i) Analysis of data from flight experiments, (ii) Performing ground-based measurements on samples recovered from the flight experiments, and (iii) Publishing/presenting results and uploading data to the NASA PSI system.

(i) A total of 30 samples covering 7 different compositions were investigated. For four compositions, multiple samples were stably levitated and fully melted. Drop size and oscillation power spectra were measured, and samples (glass for one composition) were recovered.

Sample composition RT-3 was very successful for several reasons. It levitated reliably and could be stably held over a wide range of temperatures as both solid and liquid. This enabled detailed measurements of properties and investigation of glass formation in microgravity. The samples were suitable for very detailed measurement of atomic structure using x-ray and isotope substitution neutron diffraction and modelling [3]. The results led to important new insights into glasses that form from liquids that do not contain conventional network forming species. In addition, the critical cooling rate for glass formation for the RT-3 material is in a range that is easily accessible on ISS and on the ground so that samples could be made, compared, and contrasted.

Analyses were performed on the video images, drop oscillation power spectra, and temperature data to obtain the temperature-dependent properties of the liquids. Considerable effort was invested into developing procedures for the analysis and to enable precise synchronization of the temperature and other measured data. A paper that describes the methods was published [4]. [Ed. Note: See References (below) and the Cumulative Bibliography.]

Results of density, thermal expansion coefficient, surface tension and viscosity were published for several compositions. Please see cited references [4,5].

(ii) Ground based experiments were performed in several areas. These include:

1. Optical property measurements, including fluorescence and Raman.

2. Thermodynamic property measurements on samples made on the ground and on the ISS.

The optical properties of several glasses have been measured in a collaboration with Professor Brian Topper at Clemson University and Professor Doris Moncke at Alfred University. The octahedral titanate network provides a low phonon energy host suitable for optical device materials. In addition, the glasses are strong and stable compared to typical low phonon energy halides. This work has led to four publications [6-10] and a patent filing [11].

Thermodynamic measurements on the glasses were made through a collaboration with Professor Alexandra Navrotsky, Dr. Tamil Subramani, and Dr. Laura Bonatti at the Navrotsky Eyring Center for Materials of the Universe (MotU) at Arizona State University [12]. The data show that the values of glass transition temperature and heat capacity of glasses made on Earth and in microgravity are within experimental error of each other.

Glass formation in space occurred at a slightly smaller cooling rate than was possible on Earth. We do not yet have a full explanation for the reasons. The current hypothesis is that it is due to heat transfer effects that favor glass formation in quiescent liquids compared to the stirred liquids that occur on Earth. This result was the basis for a patent that was filed in 2024 [13].

(iii) Publishing/presenting results. Several papers have been published based on the ISS experiments. These are listed in the references section. Talks were presented at the American Society for Gravitational and Space Research (ASGSR) meeting in Puerto Rico, December 2024 (Weber); American Ceramic Society Glass and Optical Materials meeting in Vancouver, May 2025 (Wilke and Weber); and the 17th International Conference on the Physics of Non-Crystalline Solids (PNCS-17), Tsukuba, Japan, August, 2025 (Weber, Invited).

Raw data is being uploaded to the NASA PSI system. Due to the large amount of video data from the drop shape and size measurements, the space allocation of the PSI account for this project was increased.

Plans: The project work is completed. Some follow-up work is needed to complete final in-process publications.

3. REFERENCES CITED:

[1] https://iss.jaxa.jp/en/kiboexp/1810_elf_en.html

[2] R. Weber, S.K. Wilke, and C.J. Benmore, “Containerless Techniques for in-situ X-Ray Measurements on Materials in Extreme Conditions,” J. Phys. Soc. Jpn., 91, 091008 (2022).

[3] S.K. Wilke, O.L.G. Alderman, C.J. Benmore, J. Neuefeind and R. Weber, “Octahedral oxide glass network in ambient pressure neodymium titanate,” Sci. Rep., 12:8258 (2022), https://doi.org/10.1038/s41598-022-12342-x

[4] S.K. Wilke, A. Al-Rubkhi, C. Koyama, T. Ishikawa, H. Oda, B. Topper, E.M. Tsekrekas, D. Möncke, O.L.G. Alderman, V. Menon, J. Rafferty, E. Clark, A.L. Kastengren, C.J. Benmore, J. Ilavsky, J. Neuefeind, S. Kohara, M. SanSoucie, B. Phillips and R. Weber, “Microgravity effects on nonequilibrium melt processing of neodymium titanate: thermophysical properties, atomic structure, glass formation and crystallization,” npj Microgravity, 10:26, (2024).

[5] S.K. Wilke, A. Alrubkhi, V. Menon, J. Rafferty, C. Koyama, T. Ishikawa, H. Oda, R. Hyers, R. Bradshaw, A. Kastengren, S. Kohara, M. SanSoucie, B. Phillips, and R. Weber, “Measuring the density, viscosity, and surface tension of molten titanates using electrostatic levitation in microgravity”, Appl. Phys. Lett., 124, 264102 (2024).

[6] B. Topper, S.K. Wilke, M. Pettes, A. Alrubkhi, V. Menon, A. Neumann, D. Möncke, R. Weber, and A. Mafi, “Mid-infrared luminescence properties of erbium and dysprosium doped lanthanum titanate glasses,” Opt. Mats. Express, 13, 2857 (2023).

[7] B. Topper, A. Neumann, A. Mafi, M. Pettes, A. Alrubkhi, S.K. Wilke and R. Weber, “Nonlinear optical properties of lanthanum titanate glasses prepared by levitation melting,” Appl. Phys. Lett., 124, 094104 (2024).

[8] B. Topper, A. Neumann, S.K. Wilke, R.E. Youngman, A. Abdulrahman and R. Weber, “Comparing Pr3+ and Nd3+ for deactivating the Er3+: 4I13/2 level in lanthanum titanate glass,” Opt. Mats. Express, 14, 1309 (2024).

[9] B. Topper, A. Neumann, S.K. Wilke, A. Alrubkhi, A. Mafi and R. Weber, “Site-selective fluorescence and spectroscopic properties of Yb-doped lanthanum titanate glasses,” Int. J. Glass. Sci., 15, 256 (2024).

[10] J. Tolliver, S.K. Wilke, A. Alrubkhi, A. Neumann, G. Balakrishnan, R. Weber, and Brian Topper, “Nd-doped lanthanum titanate glass laser,” Opt. Components and Mats. XXII, S. Jiang & M.J.F. Digonnet, Eds. Proc. of SPIE, 13362, 1336204 (2025). https://doi: 10.1117/12.3042163

[11] B. Topper, A. Mafi, J.R. Weber, S.K. Wilke, Rare earth doped glasses and their application, US20240279109A1 (2024).

[12] L. Bonatti, T. Subramani, S.K. Wilke, R. Weber, A. Navrotsky, Energetics of neodymium titanate glass made on Earth and in space, ACS Earth and Space Chemistry (2025), in press.

[13] J.R. Weber, S.K. Wilke, Method for glass formation and morphology of products made from non-equilibrium liquids by processing in reduced gravity, US20250145513A1 (2024).

NOTE: End date changed to 9/30/2024 per NSSC information (Ed., 3/5/24)

NOTE: End date changed to 9/30/2023 per NSSC information (Ed., 6/20/23)

NOTE: End date changed to 9/30/2022 per M. Sansoucie/MSFC (Ed., 1/28/21)

June 2019: Note project had preliminary work performed Feb-August 2019

Reference: [1] S. Kohara, et al., “The origin of fragility in high-temperature oxide liquids - towards fabrication of novel non-equilibrium oxides,” JAXA flight project funded in 2017.

1. Status: The project team includes Dr. Stephen Wilke, Mr. Abdulrahman Al-Rubkhi, and Mr. Jared Rafferty from Materials Development, Inc. (MDI); Dr. Shinji Kohara, National Institute for Materials Science, Japan; and Dr. Takehiko Ishikawa, Japanese Aerospace Exploration Agency, Japan. The collaborators from Japan are not funded from this grant.

2. Technical Activities: Activities during the reporting period included: (i) Running ISS ELF experiments on samples launched in mid-2023, (ii) Analyzing data from flight experiments, (iii) Performing ground-based measurements on samples recovered from the earlier flight experiments, and (iv) Publishing/presenting results.

(i) Three sets of flight experiments have been performed. The first was in August 2021, the second in December 2021 through March 2022, and the third in February 2024. During the February 2024 experiments, Richard Weber and Stephen Wilke traveled to the JAXA facility in Tsukuba to participate in the work. This single visit to JAXA was important to develop a full understanding of the experimental work. During these experiments, 16 of 19 samples were levitated and melted in ELF.

A total of 30 samples covering 7 different compositions were investigated. For four compositions, multiple samples were stably levitated and fully melted. Drop size and oscillation power spectra were measured, and samples (glass for one composition) were recovered.

Samples of the RT-3 composition for experiments in February 2024 were larger than previously used: 2.2 instead of 2.0 mm diameter. All samples used in the prior work formed glass when they were cooled in the ELF. This means that the critical cooling rate for glass formation was achieved. The larger samples cooled at a slower rate due to their smaller surface area:volume. Since the larger samples also formed glass, the results demonstrate a decrease in the critical cooling rate compared to the same composition samples processed on Earth.

Cooling rate data were measured for several samples made in ELF and on the ground using aerodynamic levitation. The cooling rates on the ground resulted from both radiative and forced convective cooling. The stagnant gas in the ELF experiments means that cooling was mainly by radiation with some conduction through the gas. The smallest cooling rate in the ISS experiments was for the 2.2 mm diameter samples. Glasses were made at somewhat smaller cooling rates in space than in the ground-based measurements. This is an important result. It suggests that the critical cooling rate in reduced gravity is slightly smaller than in Earth-based experiments where extensive fluid motion occurs.

(ii) Analyses were performed on the video images, drop oscillation power spectra, and temperature data to obtain the temperature-dependent properties of the liquids. During the early part of the work, considerable effort was put into developing procedures for the analysis and to enable precise synchronization of the temperature and other measured data. A paper that describes the methods has been submitted and is in peer review.

Results of density, thermal expansion coefficient, surface tension and viscosity have been published for several compositions. Please see cited references [3,4].

(iii) Ground based experiments and modeling are proceeding in several areas. These include: 1. Measurements of the atomic structure and dynamics of liquids and glasses. 2. Measurements of internal structure of samples using x-ray tomography. 3. Optical property measurements including fluorescence and Raman. 4. Thermodynamic property measurements on samples made on the ground and on ISS. The most detailed atomic structure measurements were made on the RT-3 neodymium titanate composition glasses. These were studied using both x-ray and neutron diffraction, including with isotope substitution. This combination of measurements provided the basis for a detailed and well-constrained structure model for the glass network that has been cited extensively[5]. As the Advanced Photon Source (APS) is currently closed for upgrade, MDI has sent some rare earth titanate composition glass samples to Dr. Shinji Kohara for measurements of the pair distribution functions (pdf) at the SPring-8 synchrotron facility. In collaboration with Professor Collin Wilkinson at Alfred University, molecular dynamics (MD) simulations have been developed to investigate the diffusion of different species in the molten RT-3 composition. These simulations use interatomic potentials that were refined to provide good agreement with X-ray scattering data on levitated melts, and the model exhibits viscosities similar to those observed in the ELF measurements. A manuscript is in preparation to publish this study. After completion of atomic structure measurements and release from the neutron source (~August 2023), samples were sent to the Materials of the Universe (MotU) laboratory at Arizona State University. Thermal properties of glasses made on ISS and on the ground were measured using drop solution calorimetry and differential scanning calorimetry. These measurements provide the glass transition temperature and enthalpy of vitrification. Work is being prepared for publication. The optical properties of several glasses have been measured in a collaboration with Dr. Brian Topper at University of New Mexico and Professor Doris Monke at Alfred University. The octahedral titanate network provides a low phonon energy host enabling long fluorescence lifetimes and generation of infrared wavelengths that are typically not possible in hard oxide glasses. In addition, the glasses are strong and stable compared to typical low phonon energy halides. This work has led to four publications [6-9] and a patent filing. Raman spectroscopy measurements made at Alfred University show a composition-dependent trend in the connectivity of the network as a function of rare earth content. This work complements x-ray pdf measurements. (iv) Publishing/presenting results. Several papers have been published based on the ISS experiments. These are listed in the references section. Talks were presented at the ASGSR meeting in Washington, DC (Weber), American Ceramic Society Glass and Optical Materials meeting in Las Vegas, May 2024 (Weber invited, Wilke), 22nd Symposium on Thermophysical Properties in Boulder, CO, June 2024 (Weber) and Non-Crystalline Materials (NCM-15), Cambridge, UK, July 2024 (Weber, Wilke). Additional papers are in preparation. Plans: Plans for the next project period are: (i) Continue data analysis, (ii) Perform post-flight analysis and ground-based measurements on samples from the recent flight experiment, (iii) Continue post-flight sample analysis, (iv) Prepare publications based on the research. 3. References cited [1] https://iss.jaxa.jp/en/kiboexp/1810_elf_en.html. [2] R. Weber, S.K. Wilke, and C.J. Benmore, “Containerless Techniques for in-situ X-Ray Measurements on Materials in Extreme Conditions,” J. Phys. Soc. Jpn., 91, 091008 (2022). [3] S.K. Wilke, A. Al-Rubkhi, C. Koyama, T. Ishikawa, H. Oda, B. Topper, E.M. Tsekrekas, D. Möncke, O.L.G. Alderman, V. Menon, J. Rafferty, E. Clark, A.L. Kastengren, C.J. Benmore, J. Ilavsky, J. Neuefeind, S. Kohara, M. SanSoucie, B. Phillips and R. Weber, “Microgravity effects on nonequilibrium melt processing of neodymium titanate: thermophysical properties, atomic structure, glass formation and crystallization,” npj Microgravity, 10:26, (2024). [4] S.K. Wilke, A. Alrubkhi, V. Menon, J. Rafferty, C. Koyama, T. Ishikawa, H. Oda, R. Hyers, R. Bradshaw, A. Kastengren, S. Kohara, M. SanSoucie, B. Phillips, and R. Weber, “Measuring the density, viscosity, and surface tension of molten titanates using electrostatic levitation in microgravity”, Appl. Phys. Lett., in revision. [5] S.K. Wilke, O.L.G. Alderman, C.J. Benmore, J. Neuefeind and R. Weber, “Octahedral oxide glass network in ambient pressure neodymium titanate,” Sci. Rep., 12:8258 (2022), https://doi.org/10.1038/s41598-022-12342-x [6] B. Topper, S.K. Wilke, M. Pettes, A. Alrubkhi, V. Menon, A. Neumann, D. Möncke, R. Weber, and A. Mafi, “Mid-infrared luminescence properties of erbium and dysprosium doped lanthanum titanate glasses,” Opt. Mats. Express, 13, 2857 (2023). [7] B. Topper, A. Neumann, A. Mafi, M. Pettes, A. Alrubkhi, S.K. Wilke and R. Weber, “Nonlinear optical properties of lanthanum titanate glasses prepared by levitation melting,” Appl. Phys. Lett., 124, 094104 (2024). [8] B. Topper, A. Neumann, S.K. Wilke, R.E. Youngman, A. Abdulrahman and R. Weber, “Comparing Pr3+ and Nd3+ for deactivating the Er3+: 4I13/2 level in lanthanum titanate glass,” Opt. Mats. Express, 14, 1309 (2024). [9] B. Topper, A. Neumann, S.K. Wilke, A. Alrubkhi, A. Mafi and R. Weber, “Site-selective fluorescence and spectroscopic properties of Yb-doped lanthanum titanate glasses,” Int. J. Glass. Sci., (2024) in press.

NOTE: End date changed to 9/30/2023 per NSSC information (Ed., 6/20/23)

NOTE: End date changed to 9/30/2022 per M. Sansoucie/MSFC (Ed., 1/28/21)

June 2019: Note project had preliminary work performed Feb-August 2019

Reference: [1] S. Kohara, et al., “The origin of fragility in high-temperature oxide liquids - towards fabrication of novel non-equilibrium oxides,” JAXA flight project funded in 2017.

June 2019: Note project had preliminary work performed Feb-August 2019

Reference: [1] S. Kohara, et al., “The origin of fragility in high-temperature oxide liquids - towards fabrication of novel non-equilibrium oxides,” JAXA flight project funded in 2017.

Technical activities during the reporting period included: (i) Performing flight experiments on samples that were launched on SpX-22, (ii) analyzing data from flight experiments, (iii) performing ground-based measurements on samples recovered from the flight experiments, (iv) publishing/presenting results, and (v) preparing additional samples that will be launched in early 2023.

Two sets of flight experiments have been performed. The first set was in August 2021; the second was in December 2021 through March 2022. A total of 26 samples covering 7 different compositions were investigated. For four compositions, multiple samples were stably levitated and fully melted. Drop size and oscillation power spectra were measured, and samples (glass for one composition) were recovered.

Analysis was performed on the video images, drop oscillation power spectra, and temperature data to obtain the temperature-dependent properties of the liquids. During the early part of the work, considerable effort was put into developing procedures for the analysis and to enable precise synchronization of the temperature and other measured data. The video data were received as .TS video files. These were converted into a sequence of bitmap images (.BMP) using Adobe Premier Pro. The bitmap images were analyzed using a calibration sample of precisely known diameter as a length reference. The volume of the sample was obtained from the measured diameter and fitting of spherical harmonic functions to the circumference.

June 2019: Note project had preliminary work performed Feb-August 2019

Reference:

[1] S. Kohara, et al., “The origin of fragility in high-temperature oxide liquids - towards fabrication of novel non-equilibrium oxides,” JAXA flight project funded in 2017.

Samples were sent to JAXA for ground-based testing that included the following: Vibration to evaluate potential fracture or powdering during launch operations; Exposure to humidity to evaluate potential degradation during storage ; X-ray examination (radiography) to detect internal voids or large cracks; Laser beam heating using the 980 nm wavelength similar to the ELF to verify heating.

Flight experiments are planned for August 2021. JAXA has prepared a timeline for the work and MDI (Materials Development Inc.) is planning precise details of the measurements to be made. The surface tension of the molten samples was estimated by reviewing literature for similar compositions. The estimate was used to calculate the expected resonant frequency for mode 2 oscillation of the drop. The oscillation frequency was also calculated using surface tension values 100 mN/m larger and smaller than the estimate. This approach provides 30-40 Hz range of frequencies over which the sample will be excited to determine the resonant frequency of a liquid drop. Once this is done for each composition, the plan will be refined. Work is in progress to evaluate different algorithms to convert the raw video data from ELF into .avi format that will be used for analysis of sample size to extract density as a function of temperature.

Ground based measurements focused on neutron and x-ray diffraction measurements of glass samples made by levitation. A neutron diffraction isotope substitution method was used at the NOMAD (Nanoscale-Ordered Materials Diffractometer) beamline at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory in order to determine the partial structure factors for neodymium and titanium in a neodymium titanate composition glass. Complementary x-ray measurements were made at the Advanced Photon Source at Argonne National Laboratory.

Two papers are in preparation. Abstracts have been submitted to both the ISS Research & Development conference that will be held virtually in August 2021 and the American Society for Gravitational & Space Research (ASGSR) annual meeting that will be held in person in Baltimore in early November 2021.

June 2019: Note project had preliminary work performed Feb-August 2019

Reference:

[1] S. Kohara, et al., “The origin of fragility in high-temperature oxide liquids - towards fabrication of novel non-equilibrium oxides,” JAXA flight project funded in 2017.

Currently, ground based work has been focused on using DL-Poly to model structure and dynamics of the liquids. This approach will be used to compare measured values with the model in order to improve predictive capabilities for liquid properties and structure.

Reference:

[1] S. Kohara, et al., “The origin of fragility in high-temperature oxide liquids - towards fabrication of novel non-equilibrium oxides,” JAXA flight project funded in 2017.