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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Microstructure‐Informed Analysis Framework for Lattice Structures: Guiding Topology‐Material Synergy in Titanium Alloys

In this work we discuss a microstructure‐informed analysis framework for lattice structures that maps the material's microstructural response to guide topology selection and mechanical performance optimization. By coupling geometrical topology with intrinsic material behavior, we demonstrate how anisotropic microstructural response can inform the design of optimized lattice structures. To illustrate this concept, we focus on two distinct classes of titanium alloys: Ti5553 (Ti‐5Al‐5Mo‐5V‐3Cr wt%), which exhibits a predominantly ‐phase microstructure, and Ti64 (Ti‐6Al‐4V wt%), which features a dual‐phase structure. These alloys exhibit markedly different mechanical responses under multiaxial loading in “fully dense” solid form. The strut‐level stress analysis of these alloys reveals how specific microstructural characteristics can guide the selection of appropriate lattice topologies. Two representative lattice configurations, one stretching‐dominated and one bending‐dominated, are evaluated under identical loading conditions to explore how microstructure‐driven design can lead to topology choices that are better suited to accommodate shear or other critical local stress states, thereby enhancing mechanical performance. A strut‐level mechanics‐based analysis is performed to evaluate shear stress distribution and highlight the role of topology‐microstructure synergy and compatibility in determining overall lattice behavior. The findings emphasize the importance of designing structures that are both load‐aware and microstructure‐responsive, enabling more effective material utilization in advanced engineering applications.

36 MATERIALS SCIENCE↗
DOE OSTI2021

High-Speed Ionic Synaptic Memory Based on 2D Titanium Carbide MXene

Synaptic devices with linear high-speed switching can accelerate learning in artificial neural networks (ANNs) embodied in hardware. Conventional resistive memories however suffer from high write noise and asymmetric conductance tuning, preventing parallel programming of ANN arrays. Electrochemical random-access memories (ECRAMs), where resistive switching occurs by ion insertion into a redox-active channel, aim to address these challenges due to their linear switching and low noise. ECRAMs using 2D materials and metal oxides however suffer from slow ion kinetics, whereas organic ECRAMs enable high-speed operation but face challenges toward on-chip integration due to poor temperature stability of polymers. Here, ECRAMs using 2D titanium carbide (Ti 3 C 2 T x ) MXene that combine the high speed of organics and the integration compatibility of inorganic materials in a single high-performance device are demonstrated. These ECRAMs combine the speed, linearity, write noise, switching energy, and endurance metrics essential for parallel acceleration of ANNs, and importantly, they are stable after heat treatment needed for back-end-of-line integration with Si electronics. The high speed and performance of these ECRAMs introduces MXenes, a large family of 2D carbides and nitrides with more than 30 stoichiometric compositions synthesized to date, as promising candidates for devices operating at the nexus of electrochemistry and electronics.

2D materials↗
DOE OSTI2022

Peptoid-Loaded Microgels Self-Defensively Inhibit Staphylococcal Colonization of Titanium in a Model of Operating-Room Contamination

Bacterial contamination of an exposed implantable medical device by the atmosphere of an operating room (OR) is increasingly implicated as a cause of device-associated infection. Here, OR contamination is modeled in vitro using an aerosolizing system to spray small quantities of staphylococci onto titanium rods. Contaminated rods always manifest culturable bacteria. Self-assembly is used to create a self-defensive Ti surface that substantially enhances the rod's resistance to such contamination. Poly(acrylic acid) microgels are electrostatically deposited onto small Ti rods and subsequently loaded by complexation with a cationic antimicrobial peptoid (TM1). The microgels are visualized in situ by optical microscopy, and changes in microgel diameter indicate the loading state. Further, these measurements show that TM1 can be quickly loaded from low-ionic-strength buffer and subsequently remained sequestered within the microgels for up to 4 weeks when soaked in phosphate buffered saline. TM1-loaded microgel-modified Ti surfaces are contaminated with aerosolized staphylococci, and subsequent assays indicate few or no culturable bacteria. In the absence of nutrients to enable metabolism, this finding suggests that bacteria trigger local TM1 release by contact transfer. The modified surfaces exhibit good in vitro cytocompatibility as manifested by the adhesion, spreading, and metabolic activity of human fetal osteoblasts.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Exploring the Interface of Skin-Layered Titanium Fibers for Electrochemical Water Splitting

Water electrolysis is the key to a decarbonized energy system, as it enables the conversion and storage of renewably generated intermittent electricity in the form of hydrogen. However, reliability challenges arising from titanium-based porous transport layers (PTLs) have hitherto restricted the deployment of next-generation water-splitting devices. Here, it is shown for the first time how PTLs can be adapted so that their interface remains well protected and resistant to corrosion across ˜4000 h under real electrolysis conditions. It is also demonstrated that the malfunctioning of unprotected PTLs is a result triggered by additional fatal degradation mechanisms over the anodic catalyst layer beyond the impacts expected from iridium oxide stability. Now, superior durability and efficiency in water electrolyzers can be achieved over extended periods of operation with less-expensive PTLs with proper protection, which can be explained by the detailed reconstruction of the interface between the different elements, materials, layers, and components presented in this work.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Surface Analysis Insight Note: Observations relating to photoemission peak shapes, oxidation state, and chemistry of titanium oxide films

It is common practice to describe the coordination of metal atoms in a binding configuration with their nearest neighbors in terms of oxidation state, a measure by which the number of electrons redistributed between atoms forming chemical bonds. In XPS terms, change to an oxidation state is commonly inferred by correlating photoemission signal with binding energy. The assumption, when classifying photoemission signals into distinct spectral shapes, is that a distribution of intensities shifted to lower binding energy is evidence of a reduction in oxidation state. In this Insight note, we raise the prospect that changes in photoemission peak shape may occur without obvious changes, determined by XPS in stoichiometry for a material. It is well known that TiO 2 measured by XPS yields reproducible Ti 2p photoemission peaks. However, on exposing TiO 2 to ion beams, Ti 2p photoemission evolves to complex distributions in intensity, which are particularly difficult to analyze by traditional fitting of bell-shaped curves to these data. For these reasons, in this Insight note, a thin film of TiO 2 deposited on a silicon substrate is chosen for analysis by XPS and linear algebraic techniques. Alterations in spectral shapes created from modified TiO 2 , which might be interpreted as the change in oxidation state, are assessed in terms of relative proportions of titanium to oxygen. It is found through detailed analysis of spectra that quantification by XPS, using procedures routinely used in practice, is not in accord with the typical interpretations of photoemission shapes. The data processing methods used and results presented in this work are of particular relevance to elucidating fundamental phenomena governing the surface evolution of materials-enabled energy processes where cyclic/non-steady usage changes the nature of bonding, especially in the presence of contaminants.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Unveiling the origins of work-hardening enhancement and mechanical instability in laser shock peened titanium

Laser shock-peening (LSP) produces complex gradients in microstructures and residual stresses, which enables fabrication of metallic engineering components with superior mechanical properties. In this work, we use non-destructive and spatially resolved high-energy X-ray diffraction (HE-XRD) to investigate the influences of LSP on microstructure, surface topography, and residual stress for high purity titanium plates. LSP is found to produce large compressive in-plane residual stresses near the peened surface which monotonically decay to zero about 2.5 mm below the surface. These properties were also tracked during in-situ tensile loading, allowing stress partitioning and work-hardening rates to be measured as a function of depth. The surface region is found to have the highest work-hardening rate and remain mechanically stable up to sample failure. In addition, a crystal rigid rotation along a transversal axis of about 27 & nbsp; was observed at large applied strain near the surface region, which is attributed to the formation of denser dispersed shear bands. Furthermore, a sudden drop in tensile stress was observed at a depth of similar to 160 mu m from the LSP surface, indicating the formation of a localized mechanical instability zone (LMIZ). The origin of this LMIZ could be attributed to the increase in shear stress induced by a load transfer from LSP surface due to the formation of denser dispersed shear bands. These observations indicate a localized transition in deformation behavior has occurred from dispersed shear banding to LMIZ and homogeneous deformation.

36 MATERIALS SCIENCE↗
DOE OSTI2021

High-speed characterization of two-phase flow and bubble dynamics in titanium felt porous media for hydrogen production

Bubble dynamics and two-phase flow phenomena are closely related to the performance of proton exchange membrane electrolyzer cells (PEMECs). This paper reports an in-situ study of the oxygen bubble behavior and associated multiphase evolutions in the anode side of PEMECs with titanium (Ti) felt liquid gas diffusion layers (LGDLs) by a high-speed visualization system. The micro oxygen bubble dynamics was captured and analyzed at different locations and virous operating conditions. The results show that the bubble detachment frequency and detachment diameter greatly increase with the operating current density. Additionally, they are significantly impacted by the local pore structure and morphology of Ti felt LGDLs. In the flow channels, there exist only several discrete micro bubbles at a low current density (0.04 A/cm 2 ) and a large flow velocity (133 mm/s). At a current density (0.2 A/cm 2 ) and a flow velocity (67 mm/s), a number of gas slugs are formed in the follow channels, in addition to discrete micro bubbles. At a high current density (1 A/cm 2 ) and a flow velocity (67 mm/s), more bubbles appear in the channel, and the flow field is dominated by slug or annular flows. These investigations can help to better understand the two-phase flow and bubble detachment mechanism, and provide a foundation for electrochemical reaction, multiphase flow studies and optimize the design of gas diffusion layers and flow fields for PEMECs in the future.

08 HYDROGEN↗
DOE OSTI2022

Brazing characteristics, microstructure, and wettability of laser powder bed fusion additive manufactured GRCop-84 compared to CuCrZr and OFC, and brazing to titanium-zirconium-molybdenum alloy limiters

Laser Powder Bed Fusion (L-PBF) of Glenn Research Copper 84 (GRCop-84), a Cr 2 Nb (8 at. % Cr, 4 at. % Nb) precipitation hardened alloy, produces a fully dense, high conductivity alloy with a yield strength of 500 MPa and ultimate tensile strength (UTS) of 740 MPa with 20% elongation; superior to other competing copper alloys. Braze wetting characteristics of GRCop-84 with Ag-Cu-X, and Au-Cu brazes were similar to CuCrZr, but less than oxygen free copper. No difference in wetting was observed between infill and surface contour areas in L-PBF GRCop-84. Wet sanding to 240 grit (R a =0.24 µm) was considered the optimal surface condition. Silver diffusing through GRCop-84 depleted Cr 2 Nb precipitates from the copper grain and deposited agglomerations of coarsened precipitates within silver-rich regions of intergranular diffusion once a density threshold was reached. Microstructure modification was minimized with 50Au-50Cu braze implying that silver caused precipitate coarsening and agglomeration, and not high temperature exposure. Coarsened precipitates were observed on the surface within braze pools implying a contribution to braze wetting. Palcusil-25, Ticusil, CuSil-ABA, and 50Au-50Cu brazes were suitable for brazing to unplated Titanium-Zirconium-Molybdenum (TZM), while sulfamate nickel plating to allows wetting with CuSil or other non-active brazes. Additionally, vacuum brazing techniques were developed to join a 1 mm thick layer of TZM to the front of additive manufactured GRCop-84 waveguides considering the brazing characteristics of both GRCop-84, TZM, and internal stress from the difference in coefficient in thermal expansion.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Thermal and structural analysis of a new WEST reciprocating probe head with Titanium-Zirconium-Molybdenum armour material

The Tore Supra tokamak was transformed into an X-point divertor fusion device in the frame of the WEST (W-for tungsten-Environment in Steady-state Tokamak) project, launched in support of the ITER tungsten divertor strategy. WEST began operation in 2017. A new reciprocating probe head, equipped with a Titanium-Zirconium-Molybdenum (TZM) heat shield, was recently built and operated on WEST during the C9 Campaign in early 2024. TZM was chosen as armour material for its very good mechanical properties between 700 °C and 1400 °C. This material was already extensively used for probe heads and other plasma facing components on the Alcator C-Mod tokamak. Here, this paper presents the design of the new WEST probe head. It is equipped with tungsten filaments that can be heated to emit electrons and provide a direct measurement of the plasma potential in the scrape-off layer, and it is also equipped with a pair of Langmuir probes. The probe plunges vertically into the plasma, reaches its maximum dive depth, then returns to its protected resting position in about 0.25 s. Thermal loads are calculated using as input the thermal properties of TZM and radial profiles of the heat flux measured in the past by other reciprocating probes, and scaled upwards to the expected heat loads in the WEST scrape-off layer. An analytical estimation of Electromagnetic (EM) loads will also be presented, as well as a thermal and structural analysis of the probe for 15 cycles at maximum plunge depth. The probe is observed by an infrared camera. Comparisons between the heat flux deduced by the Langmuir probe and the infrared radiance of the probe housing during plasma exposure are finally presented.

Diagnostic↗
DOE OSTI2022

Sinter formation during directed energy deposition of titanium alloy powders

During directed energy deposition (DED) additive manufacturing, powder agglomeration and sintering can occur outside of the melt pool when using titanium alloy powders. Using in situ synchrotron radiography we investigate the mechanisms by which sintering of Ti6242 powder occurs around the pool, performing a parametric study to determine the influence of laser power and stage traverse speed on sinter build-up. The results reveal that detrimental sinter can be reduced using a high laser power or increased stage traverse speed, although the latter also reduces deposition layer thickness. The mechanism of sinter formation during DED was determined to be in-flight heating of the powder particles in the laser beam. Calculations of particle heating under the processing conditions explored in this study confirm that powder particles can reasonably exceed 700 °C, the threshold for Ti surface oxide dissolution, and thus the powder is prone to sintering if not incorporated into the melt pool. The build-up of sinter powder layer on deposit surfaces led to lack of fusion pores. To mitigate sinter formation and its detrimental effects on DED component quality, it is essential that the powder delivery spot area is smaller than the melt pool, ensuring most powder lands in the melt pool.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Correlation of optical properties with particle size, morphology, and polymorph of fine- and nano-particle formulations of titanium dioxide powders

Titanium dioxide (TiO 2 ) particulates are known to exhibit different visible and infrared optical properties compared to the bulk material, showing strong dependence on particle size, crystal structure, and morphology. In this study, the optical properties, sizes, and morphologies of TiO 2 particles from two different sources (nano and fine powders) having a) nominally different particle sizes and b) various crystal polymorph mixture fractions are compared using a combination of single particle mass spectrometry, optical spectroscopies, and aerosol characterization methods. The nano sample was found to be largely particles of the anatase polymorph (88% by mass), while the fine sample was found to consist largely of rutile particles (95% by mass). Two distinct particle morphologies (fractal and compact) were found in each powder sample and could be identified and separated in-situ based on particle aerodynamic properties. The attenuation of near-infrared, visible and ultraviolet light by TiO 2 particles shows strong dependence on particle morphology. Furthermore, while the fine particles were found to have larger near-infrared (675–800 nm) extinction coefficients by mass than the nanoparticles, the reverse was true in the ultraviolet and visible regions (370–675 nm). However, for polydisperse particles with different sizes and shapes, the optical behaviors are not straightforward to directly correlate to a combination of physical parameters.

Lockwood, Schuyler P. [Pacific Northwest National ↗
DOE OSTI2023

Impact of titanium content on the thermo-mechanical and oxidation response of TiAlTa

This study aimed to analyze how the addition of titanium (Ti) to TiAlTa alloys affects their mechanical properties (Young’s modulus and hardness) and oxidation behavior. Alloys with three different Ti additions and equi-atomic Al and Ta were fabricated with nominal compositions of 33Ti-33Al-33Ta at%, 50Ti-25Al-25Ta at%, and 70Ti-15Al-15Ta at%. Phase identification of as-processed and compositionally homogenized alloys was conducted by coupling various electron microscopy, diffraction, and chemical analysis techniques. Composition and structures were modeled using CALPHAD-based phase predictions and compared with experimental results. Each of the alloys exhibited a unique set of microstructures with distinctly different ordered precipitates, dependent on cooling rate and chemical composition. Subsequently, nanoindentation tests were performed at temperatures of 25°C, 250°C, 500°C, and 750°C. Oxidation studies were conducted under static air at 750°C for up to 200 h. 33Ti-33Al-33Ta at% and 70Ti-15Al-15Ta at% alloys showed higher hardness and modulus than 50Ti-25Al-25Ta at% at room temperature. The 50Ti-25Al-25Ta at% alloy exhibited higher hardness and modulus values but lower oxidation resistance at 750°C when compared with the other specimens. The X-ray photoelectron spectroscopy experiments were conducted to further analyze the oxides present in the samples. Despite each sample displaying combinations of mixed oxide layers, TiO 2 was the preferred oxide forming in the 50Ti-25Al-25Ta composition, while the other samples preferred to form Al 2 O 3 . In conclusion, the findings from this systematic exploration of phase evolution in the TiAlTa alloy space provide insights for optimized material chemistries, processing, and properties.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Direct measurement of the effective properties of an additively manufactured titanium octet truss unit cell using high energy X-ray diffraction

Additively manufactured lattice structures offer a high specific strength-to-density ratio in comparison to conventional, fully dense parts. The small feature size and intricate geometry of lattice structures make it challenging to directly characterize their mechanical properties. This study presents direct measurement of the elastic mechanical properties of an additively manufactured titanium alloy octet truss unit cell. Strut stress and strain were measured using high-energy X-ray diffraction during quasi-static compressive loading. The crystallographic stress-strain relationship was converted into the stress-strain relationship of the octet truss lattice unit cell using the known symmetry of the struts. The sample studied herein was best fit by an orthorhombic linear elastic stress-strain relationship. In conclusion, this technique shows promise for studying additively manufactured lattice structures at length scales not previously reported.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Plasmon mediated deposition of Ni on titanium nitride nanoparticles: Applications in enhanced photoreduction of bicarbonate

A suitably designed plasmonic catalyst can provide versatile and energy-efficient strategies to utilize visible light to drive different catalytic reactions. Here we have successfully developed composite plasmonic catalysts by visible-light-induced deposition of popular transition metal nanocatalysts such as Ni and Pt on refractory plasmonic titanium nitride (TiN) nanoparticles. Here, the catalytic properties of the TiN composite nanoparticles were evaluated using the visible light-mediated bicarbonate to formate reduction reaction in the presence of glycerol as the hole-scavenger. Deposition of Ni and Pt nanocatalysts on TiN significantly improves its catalytic efficiency towards the reaction. However, Ni deposited on TiN nanoparticles exhibited better catalytic properties in comparison to that of TiN_Pt composites. The findings of this study can be used to develop stable and efficient visible light-responsive plasmonic composite catalysts which can accelerate different energy extensive reactions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Multifunctional transition metal doped titanium dioxide reduced graphene oxide composites as highly efficient adsorbents and photocatalysts

A series of novel, mesoporous transition metal doped titanium dioxide-reduced graphene oxide composites are synthesized where the dopants were Mn, Co, Ni, Mo, and W. An in-situ synthesis method was used which involves a green, economic, hydrothermal process which can be scaled up easily. The composites show high surface areas (165–245 m 2 /g) and monomodal pore size distributions with average pore diameters in the range of 3–5 nm. The homogeneous distributions of the dopants are seen in SEM-EDX mapping data. The indirect band gaps of the composite materials are in the range of 2.20–2.48 eV. The composites show excellent dye adsorption activities where 100% adsorption of Rhodamine B occurs within 5 min when Mo–TiO 2 /rGO composite is used. Furthermore, the adsorbed dye can either be desorbed or photocatalytically degraded and the composite is reusable up to 10 cycles without losing significant activity. Mo–TiO 2 /rGO composite showed excellent adsorption of both cationic and anionic dyes at neutral pH.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Minor titanium addition markedly improves the co-deformability of copper-tantalum composites

We investigated the microstructures of equal channel angular extrusion (ECAE) processed sintered composites of copper (Cu) and tantalum (Ta). These composites were produced with nominal Ta volume percentages ranging from 25% to 75%. Additional composites of the same nominal Ta content were prepared with a minor amount of titanium (Ti) added to facilitate interphase bonding. Ti addition was found to markedly improve the strength and co-deformability of the composites, allowing reliable extrusion of Cu-Ta composites with novel microstructures. A major influence of the Ti appears to be to soften the Ta, which contributes to improved co-deformability by reducing the flow stress mismatch between the composite constituents. Here, a change in the fracture surface morphology in the Ti-modified composite compared to the unmodified composite suggests that the Ti may also improve cohesion between Cu and Ta by reducing Ta surface oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Effect of single atom Platinum (Pt) doping and facet dependent on the electronic structure and light absorption of Lanthanum Titanium Oxide (La 2 Ti 2 O 7 ): A Density Functional Theory study

Charge generation and separation are two key processes for semiconductor photocatalysis. Here, we use Pt as a single atom catalyst to systematically examine the facet-dependent electronic band structure and light absorption of the layered perovskite-type wide-gap semiconductor, lanthanum titanium oxide (La 2 Ti 2 O 7 , LTO) by means of density functional theory simulations. In this study, it is found that single Pt atom doping of different LTO surfaces (here, (100), (101) and (001)) can not only create states in the bandgap that would promote the formation of recombination centers, but also shift the optical absorption edge to the visible region. Interestingly, the Pt doping forms a heterojunction, with the valence band maximum consisting of Pt states and the conduction band minimum consisting of LTO states, respectively. To study the facet dependent surface activity, acetic acid (CH 3 COOH) was used as a model molecule to investigate the adsorption and charge transfer on the (101), (100) and (001) Pt-LTO surface facets. The results show that the (101) facet could enable stronger adsorption of CH 3 COOH by promoting more electron transfer during the interfacial interaction. Our theoretical findings aim to promote the design and optimization of the single atom catalysts (SACs) for photocatalytic applications and other broad catalysis systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Comparison of three measurement modalities for 3D characterization of manufactured features and process-induced porosity in titanium alloy additively manufactured parts

Nondestructive characterization of internal features and defects within complex components is vital for many industrial applications, particularly with the advent of additive manufacturing (AM) technologies. However, community understanding of the limitations of nondestructive methods such as X-ray Computed Tomography (CT) can be limited in certain industrial sectors as these may be emergent applications. In this paper, we investigate the limits of X-ray CT measurements and compare extracted data with mechanical polishing serial sectioning (MPSS) and confocal laser scanning microscopy (CLSM). The test object is an additively manufactured titanium alloy disk that contains both process-induced porosity and machined features, including focused ion beam milled features designed to probe the resolution limits of X-ray CT. Results show that each of these characterization techniques has advantages and disadvantages. We compare data acquisition times, spatial resolution, geometric measurement accuracy and defect visualization fidelity across these modalities to establish a practical framework.

Additive manufacturing↗