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DOE OSTI2025

Room temperature buffer gas beam of metastable state titanium atoms

We produce beams of neutral titanium (Ti) atoms in their metastable 3d3(F4)4sa5F5 state by laser ablation into He, N2, and Ar buffer gases. The high temperatures associated with the ablation process populate the a5F5 level without the need for optical pumping. Remarkably, we observe that Ti atoms in the a5F5 state survive thousands of collisions with He and Ar buffer gas atoms without being quenched to lower-energy states. We study the yield of Ti atoms when ablated into buffer gases of varying species and pressure, quantify quenching rates and diffusion cross sections based on simple models, and provide insight into optimal design parameters for an ablation cell. Using a 3.3 cm ablation cell with interchangeable exit apertures, we produce metastable atom beams and quantify their brilliance and velocity distributions as functions of buffer gas pressure.

Schrott, Jackson↗

DOE OSTI2026

Titanium alloy response sensitivity to variations in spectral reconstructions of National Ignition Facility xenon line-emission x-ray sources

Thermomechanical shock experiments on the National Ignition Facility (NIF) aim to study high strain rate dynamic material response. In such experiments, the NIF laser is used to generate high fluence x-ray emission sources, which irradiate material samples of interest. Under sufficiently high x-ray energy deposition, thermomechanical impulses are generated in the materials. While it is known that the characteristics of x-ray generated impulses vary as a function of incident x-ray spectra, it remains unclear how spectral assumptions and uncertainties in NIF spectral reconstructions affect our interpretation of impulsive loading. Here, in this paper, we simulate the response of a standard titanium alloy baseline sample to synthetic analytically derived and measured NIF xenon line-emission x-ray sources with a radiation hydrodynamics code. We vary the source spectral characteristics based on different source reconstruction techniques to understand the resulting variation in baseline sample response and compare the simulated response with experimental results. We find that the response is highly sensitive to assumptions made about the spectral contents and that knowledge of spectral uncertainties bounds our understanding of the resulting material response. The results of this effort help to extend our ability to use baseline material samples to extract quantitative properties from x-ray experiments on the NIF.

Alloys↗

DOE OSTI2024

Identification of large polarons and exciton polarons in rutile and anatase polymorphs of titanium dioxide

Titanium dioxide (TiO 2 ) is a wide-gap semiconductor with numerous applications in photocatalysis, photovoltaics, and neuromorphic computing. The unique functional properties of this material critically depend on its ability to transport charge in the form of polarons, namely narrow electron wavepackets accompanied by local distortions of the crystal lattice. It is currently well established that the most important polymorphs of TiO 2 , the rutile and anatase phases, harbor small electron polarons and small hole polarons, respectively. However, whether additional polaronic species exist in TiO 2 , and under which conditions, remain open questions. Here, we provide definitive answers to these questions by exploring the rich landscape of polaron quasiparticles in TiO 2 via recently developed ab initio techniques. In addition to the already known small polarons, we identify three species, namely a large hole polaron in rutile, a large quasi-two-dimensional electron polaron in anatase, and a large exciton polaron in anatase. These findings complete the puzzle on the polaron physics of TiO 2 and pave the way for systematically probing and manipulating polarons in a broad class of complex oxides and quantum materials.

Dai, Zhenbang↗

DOE OSTI2023

Optical telecommunications-band clock based on neutral titanium atoms

Here, we propose an optical clock based on ultranarrow transitions in neutral titanium, which exhibit small blackbody radiation and quadratic Zeeman shifts and have wavelengths in the S-, C-, and L-telecommunications fiber bands, allowing for integration with robust laser technology. We calculate relevant properties using a high-precision relativistic hybrid method that combines configuration interaction and coupled-cluster approaches. To identify magic wavelengths, we have completed the largest-to-date direct dynamical polarizability calculations. Finally, we identify challenges that arise from magnetic dipole-dipole interactions and describe an approach to overcome them. A telecommunications-band atomic frequency standard will aid the deployment of optical clock networks and clock comparisons over long distances.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2024

Investigation on laser absorption and x-ray radiation in microstructured titanium targets heated by short-pulse relativistic laser pulses

The enhancement effect of a microstructured surface on laser absorption and characteristic K α emission has been investigated by measuring K-shell emission from titanium (Ti) targets irradiated with high-intensity ( ∼ 10 20 W cm − 2 ), subpicosecond (500 fs) laser pulses. The experimental results indicate a modest enhancement ( 1.6 × ) of K α emission from microstructured targets compared to flat foils, but with a similar intensity and profile of He α and Li-like satellites. Particle-in-cell (PIC) simulations are implemented to further understand the underlying physical processes in the laser interaction with both targets, interpreting the mechanisms responsible for the K α enhancement. The reasons for the lower-than-expected enhancement of K α emission are discussed. The rapid heating of the bulk plasma might result in the premature shutdown of K α emission before the thermalization of hot electrons or even the end of laser pulses, suggesting that the use of K α emission as a diagnostic of the hot-electron yield or relaxation could lead to a misinterpretation. Published by the American Physical Society 2024

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2026

High-pressure melt dynamics in shock-compressed titanium

In this work we study the high-pressure melting behavior of titanium using laser-driven shock compression with in situ femtosecond x-ray diffraction and molecular-dynamics simulations based on a machine-learned interatomic potential. The MD simulations predict the solid-liquid coexistence on the Hugoniot in the ∼111−124GPa range. Experimentally, we observe the first evidence of liquid at 86 GPa. We also observe pronounced microstructural changes with pressure, with strong grain refinement associated with the emergence of liquid, within the solid-liquid coexistence (∼110−126GPa). Above 126 GPa, we observe the persistence of residual levels of highly textured crystalline Ti to ∼180GPa, well above the expected melt completion pressure. We discuss the accuracy that current laser-shock experimental platforms have at determining the melt onset and completion pressures.

36 MATERIALS SCIENCE↗

DOE OSTI2020

In situ high-temperature X-ray diffraction study of Sc-doped titanium oxide nanocrystallites

Titanium dioxide is an inexpensive wide-gap highly ionic semiconductor with striking photocatalytic capabilities in several heterogeneous photoredox reactions. A small crystal size is desirable to maximize the surface area, since photocatalytic reactions occur at the surface of a photocatalyst. Presented in this work are the synthesis and microstructural characterization of 4 at.% Sc-doped TiO 2 (4SDT) prepared by water-based co-precipitation. The crystal structure of 4SDT was examined via in situ high-temperature powder X-ray diffraction experiments from 25 to 1200°C. Rietveld analysis revealed single-phase anatase up to 875°C, while at 900°C the anatase-to-rutile phase transformation occurred and at higher temperatures additional reflections of Sc-rich phases (Sc 2 TiO 5 from 975°C and Ti 3 Sc 4 O 12 or Sc 2 O 3 at 1200°C) were observed. Debye function analysis (DFA) was applied to model the total scattering pattern directly in reciprocal space, allowing the reconstruction of Ti vacancies. Both Rietveld and DFA methods were applied to estimate the nanocrystallite size and shape with consistent growth in crystallite size with temperature: an ellipsoid shape with equatorial ~4.7 nm / axial (001) ~6.9 nm at 25°C to equatorial ~27.9 nm / axial (001) ~39.6 nm at 900°C refined by Rietveld analysis, versus a cylinder shape with D a , b = 4.3 nm and size dispersion σ ab = 1.5 nm, L c = 4.9 nm and σ c = 2.3 nm at 25°C to D a , b = 21.4 nm, σ ab = 8.3 nm, L c = 23.9 and σ c = 10.9 nm at 900°C estimated by DFA. The microstructural changes obtained by Rietveld and DFA methods were supported by high-resolution transmission electron microscopy image analysis, as well as by the less direct nitrogen sorption techniques that provide information on the size of non-agglomerated and dense particles. The Ti site-occupancy factor showed a linear increase from 0.6–0.8 at 25°C to unity at 900°C for anatase, and from ~0.7 at 900°C to unity at 1200°C for rutile, via Rietveld analysis and DFA.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Low pH Titanium Electrochemistry in the Presence of Sulfuric Acid and its Implications for Redox Flow Battery Applications

Titanium (Ti) is a promising elemental redox active species for redox flow batteries (RFBs) due to its 100x availability in the Earth crust, and 10x lower cost (compared to elemental vanadium). Furthermore, Ti salts are highly soluble in water and concentrations >5 M can be easily obtained. Seeking to harness the higher solubility (and hence energy density) of the Ti electrolyte for flow battery applications, the Ti 4+ /Ti 3+ redox couple was investigated at high concentrations (up to 5 M) relevant to RFB applications. The behavior of Ti ions in H 2 SO 4 supported electrolytes was investigated by varying the ratio of Ti redox active species to counterion. The electrochemical characteristics, transport properties, and redox kinetics of the Ti 4+ /Ti 3+ redox couple were measured and the impact of the Ti x+ to solvating ligand ratio was examined. The coordination structures around solvated Ti x+ ions were spectroscopically determined and the effect of solvation structure on the Ti 3+ /Ti 4+ redox rate constants were examined and correlated to the calculated solvation energy (hence distinguishing between inner- and outer-sphere processes) and the role of catalysts was addressed. The Ti electrolyte development guidelines presented herein will advance the development of Ti-based RFBs as a promising pathway towards cost effective, grid-scale energy storage.

Electrochemistry↗

DOE OSTI2021

Broadband titanium nitride disordered metasurface absorbers

We experimentally demonstrate titanium nitride (TiN) broadband metasurface perfect absorbers by conformally coating plasmonic TiN films onto disordered anodic aluminum oxide (AAO) nanotemplates. The disordered metasurface absorbers exhibit polarization-insensitive and weak angle-dependent perfect absorption over the entire visible and near-infrared spectral regions (300 < λ < 2500 nm). We show from experimental results and numerical simulations that the light scattering induced by the strong disorder of the AAO nanopores and the strong absorption of the TiN deposited on their sidewall are of critical importance for achieving broadband perfect absorption. The TiN disordered metasurface perfect absorbers are superior to many other types of broadband perfect absorbers previously reported and are more suitable for practical applications especially in harsh environments. The device concept for broadband perfect absorption based on plasmonic metal-nitride film coated disordered dielectric media could potentially be extended to significantly enhance the efficiency of solar energy harvesting and the performance of hot-carrier based optoelectronics.

Chang, Chun-Chieh (ORCID:0000000337282454)↗

DOE OSTI2020

Dynamically controlled random lasing with colloidal titanium carbide MXene

Control of lasing properties through tailorable and dynamically tunable materials and reconfigurable compositions can augment the performance of random lasers for a wide range of applications. Here, a colloid of randomly dispersed weakly scattering single-layer titanium carbide (Ti 3 C 2 T x ) MXene flakes embedded within rhodamine 101 gain medium is experimentally shown to provide feedback for random lasing. Additionally, in contrast to previously reported random laser systems where the optical properties of scatterers are static, the relative permittivity of Ti 3 C 2 T x MXene flakes can be varied under optical pumping due to the saturable absorption properties. Numerical simulations indicate that the observed nonlinear response of Ti 3 C 2 T x MXene flakes enables dynamically tunable random lasing. Thus, pumping the Ti 3 C 2 T x MXene flakes with a second optical source decreases the gain threshold required to obtain random lasing. Also, using numerical simulations, it is shown that the control over the intensity of the second pump enables tuning the field distribution of the random lasing modes. Considering the diversity of the MXenes family, the proposed MXene colloidal metamaterial design opens up a new avenue to advanced control of lasing properties for photonic applications.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Solid-state ionics: The key to the discovery and domination of lithium batteries: some learnings from β-alumina and titanium disulfide

We report solid state ionics, the study of fast ion transport in solids, expanded explosively after the discovery of sodium ion transport in b-alumina 50 years ago and has revolutionized energy storage. Lithium ion batteries have come from a dream with titanium disulfide to enabling the communications revolution and are enabling renewable energy. Much can be learnt from these early studies, that will allow the attainment of a fossil-free society and a sustainable environment.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Resolving intragranular stress fields in plastically deformed titanium using point-focused high-energy diffraction microscopy

Abstract The response of a polycrystalline material to a mechanical load depends not only on the response of each individual grain, but also on the interaction with its neighbors. These interactions lead to local, intragranular stress concentrations that often dictate the initiation of plastic deformation and consequently the macroscopic stress–strain behavior. However, very few experimental studies have quantified intragranular stresses across bulk, three-dimensional volumes. In this work, a synchrotron X-ray diffraction technique called point-focused high-energy diffraction microscopy (pf-HEDM) is used to characterize intragranular deformation across a bulk, plastically deformed, polycrystalline titanium specimen. The results reveal the heterogenous stress distributions within individual grains and across grain boundaries, a stress concentration between a low and high Schmid factor grain pair, and a stress gradient near an extension twinning boundary. This work demonstrates the potential for the future use of pf-HEDM for understanding the local deformation associated with networks of grains and informing mesoscale models. Graphical abstract

36 MATERIALS SCIENCE↗

DOE OSTI2022

Accelerated beta radiation aging of interlayer titanium nitride in gallium nitride contacts

Currently, there is no good way to determine the influence of the radiation on the aging of betavoltaic electrical contacts. Here, this work tested a method to accelerate the aging of the contacts inside a betavoltaic by enhancing energy deposition within the interfacial region of interest. An electrical contact of gold-titanium on gallium nitride was aged by exposure to tritium betas and electrons in a beamline. The interface stoichiometry was compared to the electrical performance of the contact. The method to age the betavoltaic component could help predict lifetime performance of the internal electrical contacts and provide assurance of deployment reliability.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Design and Development of Low Weight, Titanium Aluminide Airfoils for High Performance Industrial Gas Turbines meeting 65% Combined Cycle Efficiency (Final Report)

This project funded under DOE-FOA-0001816 was performed with the intent of evaluating the potential of utilizing a low density, high specific strength Titanium Aluminide (TiAl) alloy in a large annulus last stage gas turbine blade with the intent of improving combined cycle gas turbine efficiency toward a goal of reaching 65% efficiency. The project consisted of identifying a potentially suitable TiAl material for manufacture of such a large blade by investment casting. This included estimation of design properties for the selected alloy, trade studies using a baseline design created for a nickel based alloy cast in the TiAl alloy to evaluate potential design changes required for the use of this material and optimization of a prototype design for the same baseline application using the selected TiAl alloy. Several rounds of optimization were completed with the intent of meeting the baseline design targets with a resulting design that showed at least equivalent performance in terms of creep, LCF/TMF, HCF and aerodynamic damping potential. While it was found that significant reductions in blade loading on the disk were possible, the design resulting from the optimization met most lifing targets at the baseline size, but showed a reduction in margins in some areas in comparison to the Ni-based baseline design. Additionally, it was found that the low strain tolerance of the TiAl alloy for temperatures at and below the operational temperature of the attachment resulted in marginal, although still acceptable, creep rupture performance of the design. Due to results indicating the reduced potential for increasing turbine annulus compared to expectations a Phase II award was not proposed and it is not recommended to pursue additional design optimization efforts until further material advances with TiAl materials are achieved.

03 NATURAL GAS↗

DOE OSTI2021

Adhesion of Titanium Coatings on Additively Manufactured Stainless Steel [Slides]

Additive manufacturing can improve fuel cell development by increasing design development speed, enabling complex designs through more flexible fabrication, and reducing wasted excess material. The goal of the project is to develop a process for strongly adhering a coating of titanium to additively manufactured stainless steel.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Research on high power, doped titanium-niobium oxide anodes

The main objective of this project is to synthesize titanium niobium oxide (TNO) that has a nanoporous structure with porous channels for rapid lithium diffusion, enabling extreme fast charging (XFC). The focus of this project is to improve the electronic conductivity and ion diffusion coefficient in TNO to achieve high capacities under extreme fast charge conditions. In addition, electrolytes with additives will be formulated to promote stable interphase formation on the NMC cathode surface to improve long cycling stability.

25 ENERGY STORAGE↗

DOE OSTI2022

Progress Towards a Titanium-Zirconium-Molybdenum Alloy Coreblock Prototype Using Powder Bed Fusion

Microreactor designs make use of a coreblock for structural stability allowing for these devices to provide powder generation while being portable and inherently safe. In order to maximize energy output of the microreactors, materials must be able to withstand high temperature without melting and without substantial decreases in mechanical properties. As simultaneous projects looking at steels, graphite, and other materials are on-going, this work package will investigate titanium – zirconium – molybdenum alloy (TZM) as it allows for potentially higher microreactor operating temperatures than traditional reactor materials such as stainless steel. Notably, this alloy was developed in the 1960s for use in rockets and has a very high melting point (2623°C) but is difficult to form, machine and join. With limited needs in aerospace, literature is appropriately sparce in looking at the AM of TZM (examples include [1,2]). However, the properties appear to be an excellent match for the needs of the microreactor coreblock leading to the current project. In addition, small washers form the bulk of TZM parts needed in aerospace while the microreactor community was looking at larger, more complex parts. Therefore, AM of TZM is being explored to enable near – net shape of components with the needed complexity to impact the nuclear energy field.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Life-Cycle Inventory of Critical Materials: Nickel, Copper, Titanium, and Rare-Earth Elements

The United States has developed a list of critical minerals/materials whose sustained and reliable supply is pivotal to the robust functioning of critical industrial sectors. A key concern with these minerals is their environmental effects as a function of their production location. This requires material and energy flow details for their processing steps. This report provides a life-cycle inventory (LCI) for producing four critical minerals and/or material systems (nickel, copper, titanium, and rare-earth elements) incorporated in the updated GREET® (Greenhouse gases, Regulated Emissions, and Energy use in Technologies) model. For these systems, we provide an LCI as a function of production location – domestic (within the United States) and international (geographies from where the US imports these minerals). Our LCI also considers variations in ore grades for nickel and copper. This report also provides an LCI for all intermediate materials used to produce these critical materials.

58 GEOSCIENCES↗