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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Ramp-release experiments for strength measurements: Strain-rate dependence

This paper presents an enhanced analysis method for investigating material properties at high strain rates, extending the capability of established experimental techniques to gain more information. The ramp-release method has been applied to many experiments reported at high (≈10 5 − 10 6 s −1 ) strain-rates. More recent data gathered at the National Ignition Facility (NIF) has enabled higher (≈10 8 s −1 ) strain-rates to be studied. Here, we present an initial application of ramp-release analysis to NIF ramp-compression data, illustrating both the opportunities and the practical challenges of extending these methods to laser-driven platforms. The higher strain-rates accessed at the NIF mean that there is more strain-rate enhancement to strength, and the experimental configuration means that this enhancement is more readily seen in the data. This is enabled by the capability of avoiding peak-compression attenuation through the sample thickness with a designed hold period made possible by the pulse-shaping capability of NIF. We propose that this combination of experimental conditions and an enhanced analysis method enables the strain-rate enhancement to strength to be studied, and potentially for this to inform physics models at smaller scales than the continuum.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Entropic formation of a thermodynamically stable colloidal quasicrystal with negligible phason strain

Quasicrystals have been discovered in a variety of materials ranging from metals to polymers. Yet, why and how they form is incompletely understood. In situ transmission electron microscopy of alloy quasicrystal formation in metals suggests an error-and-repair mechanism, whereby quasiperiodic crystals grow imperfectly with phason strain present, and only perfect themselves later into a high-quality quasicrystal with negligible phason strain. The growth mechanism has not been investigated for other types of quasicrystals, such as dendrimeric, polymeric, or colloidal quasicrystals. Soft-matter quasicrystals typically result from entropic, rather than energetic, interactions, and are not usually grown (either in laboratories or in silico) into large-volume quasicrystals. Consequently, it is unknown whether soft-matter quasicrystals form with the high degree of structural quality found in metal alloy quasicrystals. Here, we investigate the entropically driven growth of colloidal dodecagonal quasicrystals (DQCs) via computer simulation of systems of hard tetrahedra, which are simple models for anisotropic colloidal particles that form a quasicrystal. Using a pattern recognition algorithm applied to particle trajectories during DQC growth, we analyze phason strain to follow the evolution of quasiperiodic order. As in alloys, we observe high structural quality; DQCs with low phason strain crystallize directly from the melt and only require minimal further reduction of phason strain. Finally, we also observe transformation from a denser approximant to the DQC via continuous phason strain relaxation. Our results demonstrate that soft-matter quasicrystals dominated by entropy can be thermodynamically stable and grown with high structural quality––just like their alloy quasicrystal counterparts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Nanoscale elastic strain mapping of polycrystalline materials

Measuring elastic strain with nanoscale resolution has historically been very difficult and required a marriage of simulations and experiments. Nano precession electron diffraction provides excellent strain and spatial resolution but has traditionally only been applied to single-crystalline semiconductors. The present study illustrates that the technique can also be applied to polycrystalline materials. The strain resolution was determined to be 0.15% and 0.10% for polycrystalline copper and boron carbide, respectively. Local strain maps were obtained near grain boundaries in boron carbide and dislocations in magnesium and shown to correlate with expected values, thus demonstrating the efficacy of this technique. This study demonstrates that nano precession electron diffraction can be extended from semiconductor devices to polycrystalline metals and ceramics to map nanoscale elastic strain fields with high strain resolution.

36 MATERIALS SCIENCE↗
DOE OSTI2016

New modalities of strain-control of ferroelectric thin films

Ferroelectrics, with their spontaneous switchable electric polarization and strong coupling between their electrical, mechanical, thermal, and optical responses, provide functionalities crucial for a diverse range of applications. Over the past decade, there has been significant progress in epitaxial strain engineering of oxide ferroelectric thin films to control and enhance the nature of ferroelectric order, alter ferroelectric susceptibilities, and to create new modes of response which can be harnessed for various applications. This review aims to cover some of the most important discoveries in strain engineering over the past decade and highlight some of the new and emerging approaches for strain control of ferroelectrics. We discuss how these new approaches to strain engineering provide promising routes to control and decouple ferroelectric susceptibilities and create new modes of response not possible in the confines of conventional strain engineering. To conclude, we will provide an overview and prospectus of these new and interesting modalities of strain engineering helping to accelerate their widespread development and implementation in future functional devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

In situ measurement of phase transformations and residual stress evolution during welding using spatially distributed fiber-optic strain sensors

Welding of high-strength steels can result in large tensile strains as the base metal and filler material cool from their molten state. To combat these large tensile strains, low-transformation-temperature (LTT) metal fillers have been proposed. These fillers undergo a martensitic phase transformation at a lower temperature which can ultimately reduce the tensile strain or can even introduce compressive strain adjacent to the weld metal. However, the process for optimizing the composition of the LTT material, as well as various weld parameters for each unique weld geometry, can be quite expensive, especially if the acceptance criterion requires using neutrons, x-ray beams, or destructive techniques to characterize residual stresses. This work describes a simple, low-cost method for quantifying residual stresses and phase transformations in situ during welding. Spatially distributed fiber-optic sensors were bonded to a cast iron plate, along with tack-welded thermocouples, to measure temperature and strain during multiple passes with LTT filler metals. Results show that the fiber-optic sensors can successfully resolve compressive strain adjacent to the weld region caused by the martensitic phase transformations in the LTT filler material.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

The ability of Salmonella enterica subsp. enterica strains to form biofilms on abiotic surfaces and their susceptibility to selected essential oil components

Abstract The ability of Salmonella enterica subsp. enterica to persist and form biofilms on different surfaces can constitute a source of food contamination, being an issue of global concern. The objective of this study was to understand the biofilm formation profile of 14 S. enterica strains among different serovars and sources and to evaluate the ability of essential oil (EO) components (carveol, citronellol, and citronellal) to disinfect the biofilms formed on stainless steel and polypropylene surfaces. All the strains were able to form biofilms with counts between 5.34 to 6.78 log CFU cm−2. Then, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of EO components were evaluated on two selected strains. All compounds inhibited the growth of Salmonella Typhimurium (strain 1; MIC = 800–1000 µg ml−1) and Salmonella Enteritidis (strain 5; MIC = 400–1000 µg ml−1) and only carveol showed bactericidal activity against strains 1 and 5 (MBC = 1200 µg ml−1). Biofilms were exposed to the EO components at 10 × MIC for 30 min and polypropylene surfaces were more difficult to disinfect showing reductions between 0.9 and <1.2 log CFU cm−2. In general, the S. enterica biofilms demonstrated a significant tolerance to disinfection, demonstrating their high degree of recalcitrance on food processing surfaces.

Pérez-Lavalle, Liliana (ORCID:0000000344825031)↗
DOE OSTI2020

Theory of strain-induced magnetic order and splitting of $T_c$ and $T_{\text{TRSB}}$ in Sr 2 RuO 4

The internal structure of the superconducting state in Sr 2 RuO 4 remains elusive at present, and exhibits evidence for time-reversal symmetry breaking. Recent muon spin relaxation measurements under uniaxial strain have revealed an increasing splitting between the superconducting critical temperature $T_c$ and the onset of time-reversal symmetry breaking $T_{\text{TRSB}}$ with applied strain. In addition, static magnetic order is induced by the uniaxial strain beyond ~1 GPa, indicating that unstrained Sr 2 RuO 4 is close to a magnetic quantum critical point. Here we perform a theoretical study of the magnetic susceptibility and the associated pairing structure as a function of uniaxial strain. In this work, it is found that the recent muon relaxation data can be qualitatively explained from the perspective of spin-fluctuation mediated pairing and the associated strain dependence of accidentally degenerate pair states in unstrained Sr 2 RuO 4 . In addition, while unstrained Sr 2 RuO 4 features mainly (2π /3, 2π /3) magnetic fluctuations, uniaxial strain promotes (π, ±π /2) magnetic order.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Revealing the competition between charge density wave and superconductivity in CsV 3 Sb 5 through uniaxial strain

In this paper we report the effect of uniaxial strain ε applied along the crystalline a axis on the newly discovered kagome superconductor CsV 3 Sb 5 . At ambient conditions, CsV 3 Sb 5 shows a charge-density wave (CDW) transition at T CDW = 94.5K and superconducts below T c = 3.34K. In our paper, when the uniaxial strain ε is varied from –0.90% to 0.90%,T c monotonically increases by ~33% from 3.0 to 4.0 K, giving rise to the empirical relation T c (ε) = 3.4 + 0.56ε + 0.12ε 2 . On the other hand, for ε changing from –0.76% to 1.26%,TCDW decreases monotonically by ~10% from 97.5 to 87.5 K with T CDW (ε) = 94.5 – 4.72ε – 0.60ε 2 . The opposite response of T c and T CDW to the uniaxial strain suggests strong competition between these two orders. Comparison with hydrostatic pressure measurements indicate that it is the change in the c axis that is responsible for these behaviors of the CDW and superconducting transitions, and that the explicit breaking of the sixfold rotational symmetry by strain has a negligible effect. Combined with our first-principles calculations and phenomenological analysis, we conclude that the enhancement in Tc with decreasing c is caused primarily by the suppression of T CDW , rather than strain-induced modifications in the bare superconducting parameters. We propose that the sensitivity of T CDW with respect to the changes in the c axis arises from the impact of the latter on the trilinear coupling between the $M$$^{+}_{1}$ and the $L$$^{–}_{2}$ phonon modes associated with the CDW. Altogether, our paper reveals that the c-axis lattice parameter, which can be controlled by both pressure and uniaxial strain, is a powerful tuning knob for the phase diagram of CsV 3 Sb 5 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Manipulating the metal-to-insulator transition and magnetic properties in manganite thin films via epitaxial strain

Strain engineering of epitaxial transition metal oxide heterostructures offers an intriguing opportunity to control electronic structures by modifying the interplay between spin, charge, orbital, and lattice degrees of freedom. Here, we demonstrate that the electronic structure, magnetic and transport properties of La 0.9 Ba 0.1 MnO 3 thin films can be effectively controlled by epitaxial strain. Spectroscopic studies and first-principles calculations reveal that the orbital occupancy in Mn eg orbitals can be switched from the d 3z 2 -r 2 orbital to the d x 2 -y 2 orbital by varying the strain from compressive to tensile. Further, the change of orbital occupancy associated with Mn 3d-O 2p hybridization leads to dramatic modulation of the magnetic and electronic properties of strained La 0.9 Ba 0.1 MnO 3 thin films. Under moderate tensile strain, an emergent ferromagnetic insulating state with an enhanced ferromagnetic Curie temperature of 215 K is achieved. These findings not only deepen our understanding of electronic structures, magnetic and transport properties in the La 0.9 Ba 0.1 MnO 3 system, but also demonstrate the use of epitaxial strain as an effective knob to tune the electronic structures and related physical properties for potential spintronic device applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Strain-induced orbital-energy shift in antiferromagnetic RuO 2 revealed by resonant elastic x-ray scattering

In its ground state, RuO 2 was long thought to be an ordinary metallic paramagnet. Recent neutron and x-ray diffraction revealed that bulk RuO 2 is an antiferromagnet with T N above 300 K. Furthermore, epitaxial strain induces superconductivity in thin films of RuO 2 below 2 K. Here, we present a resonant elastic x-ray scattering study at the Ru L 2 edge of the strained RuO 2 films exhibiting the strain-induced superconductivity. Here, we observe an azimuthal modulation of the 100 Bragg peak consistent with bulk. Most notably, in the strained films displaying superconductivity, we observe a ~ 1 eV shift of the Ru e g orbitals to a higher energy. The energy shift is smaller in thicker, relaxed films and films with a different strain direction. Our results provide further evidence of the utility of epitaxial strain as a tuning parameter in complex oxides.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

NMR study of Ni 50+x ⁢Ti 50-x strain glasses

Here, we studied Ni 50+x ⁢Ti 50-x with compositions up to x = 2, performing 47 Ti and 49 Ti nuclear magnetic resonance (NMR) measurements from 4 to 400 K. For large x in this system, a strain glass appears in which frozen ferroelastic nanodomains replace the displacive martensite structural transition. Here, we demonstrate that NMR can provide an extremely effective probe of the strain-glass freezing process, with large changes in NMR line shape due to the effects of random strains which become motionally narrowed at high temperatures. At the same time with high-resolution x-ray diffraction we confirm the lack of structural changes in x ≥ 1.2 samples, while we show that there is little change in the electronic behavior across the strain-glass freezing temperature. NMR spin-lattice relaxation time (T 1 ) measurements provide a further measure of the dynamics of the freezing process, and indicate a predominantly thermally activated behavior both above and below the strain-glass freezing temperature. We show that the strain-glass results are consistent with a very small density of critically divergent domains undergoing a Vogel-Fulcher-type freezing process, coexisting with domains exhibiting faster dynamics and stronger pinning.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Domain wall fluctuations in ferroelectrics coupled to strain

Using a Ginzburg-Landau-Devonshire model that includes the coupling of polarization to strain, we calculate the fluctuation spectra of ferroelectric domain walls. The influence of the strain coupling differs between 180 degrees. and 90 degrees. walls due to the different strain profiles of the two configurations. The finite speed of acoustic phonons, vs, retards the response of the strain to polarization fluctuations, and the results depend on v(s). For v(s) -> infinity, the strain mediates an instantaneous electrostrictive interaction, which is long-range in the 90 degrees. wall case. For finite v(s), acoustic phonons damp the wall excitations, producing a continuum in the spectral function. As v(s) -> 0, a gapped mode emerges, which corresponds to the polarization oscillating in a fixed strain potential.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Strain sensitivity of band gaps of Sn-containing semiconductors

Tuning of band gaps of semiconductors is a way to optimize materials for applications within photovoltaics or as photocatalysts. One way to achieve this is through applying strain to the materials. Here, we investigate the effect of strain on a range of Sn-containing semiconductors using density functional theory and many-body perturbation theory calculations. We find that the band gaps of bulk Sn oxides with SnO 6 octahedra are highly sensitive to volumetric strain. By applying a small isotropic strain of 2% (–2%), a decrease (increase) of band gaps as large as 0.8 to 1.0 eV are obtained. We attribute the ultrahigh strain sensitivity to the pure Sn s-state character of the conduction-band edges. Other Sn-containing compounds may show both increasing and decreasing gaps under tensile strain and we show that the behavior can be understood by analyzing the role of the Sn s states in both the valence and the conduction bands.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Strain phase separation: Formation of ferroelastic domain structures

Phase decomposition is a well-known process leading to the formation of two-phase mixtures. Here we show that a strain imposed on a ferroelastic crystal promotes the formation of mixed phases and domains, i.e., strain phase separation with local strains determined by a common tangent construction on the free energy versus strain curves. It is demonstrated that a domain structure can be understood using the concepts of domain/phase rule, lever rule, and coherent and incoherent strain phase separation, in a complete analogy to phase decomposition. The proposed strain phase separation model is validated using phase-field simulations and experimental observations of PbTiO 3 and BiFeO 3 thin films as examples. Finally, the proposed model provides a simple tool to guide and design domain structures of ferroelastic systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Epitaxial strain modulated electronic properties of interface controlled nickelate superlattices

For this study, perovskite nickelate heterostructures consisting of single unit cells of EuNiO 3 and LaNiO 3 have been grown on a set of single crystalline substrates by pulsed laser interval deposition to investigate the effect of epitaxial strain on electronic and magnetic properties at the extreme interface limit. Despite the variation of substrate in-plane lattice constants and lattice symmetry, the structural response to heterostructuring is primarily controlled by the presence of the EuNiO 3 layer. In sharp contrast to bulk LaNiO 3 or EuNiO 3 , the superlattices grown under tensile strains exhibit metal-to-insulator transitions (MIT) below room temperature. The onset of magnetic and electronic transitions associated with the MIT can be further separated by application of large tensile strain. Furthermore, these transitions can be entirely suppressed by very small compressive strain. X-ray resonant absorption spectroscopy measurements reveal that such strain-controlled MIT is directly linked to a strain-induced self-doping effect without any chemical doping.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Ferroelectricity in [111]-oriented epitaxially strained SrTiO 3 from first principles

We use first-principles density-functional theory calculations to investigate the effect of biaxial strain in the low-temperature structural and ferroelectric properties of [111]-oriented SrTiO 3 . In this work we find that [111] biaxial strain, achievable by coherent epitaxial growth along the [111] direction, induces structural distortions in SrTiO 3 that are not present in either bulk or [001]-oriented SrTiO 3 . Under [111] biaxial strain, SrTiO 3 displays ferroelectricity at tensile strain, and paraelectricity at compressive strain. We compute the phonon spectrum and macroscopic polarization of SrTiO 3 as a function of [111] biaxial strain, and relate our results to the predictions of the free-energy phenomenological model of Pertsev, Tagantsev, and Setter

36 MATERIALS SCIENCE↗
DOE OSTI2020

Local strain-dependent electronic structure and perpendicular magnetic anisotropy of a MnGaN 2D magnetic monolayer

Local strain-dependent spin-polarized electronic structure of a two-dimensional (2D) magnetic layer is an exciting property for practical applications. For example, it holds the promise for advanced ultrathin spintronic nanodevices with customized electronic and magnetic properties by local strain engineering. Here, we demonstrate that the spin-polarized electronic structure of a 2D manganese gallium nitride (MnGaN-2D) magnetic monolayer is sensitive to intrinsic local lattice strain, as proven by first-principles calculations and indicated by scanning tunneling spectroscopy measurements. Atomic resolution images reveal a highly non-Gaussian lattice spacing/strain distribution, while the spectroscopy reveals variations in the electronic density of states. Simulations of the MnGaN-2D monolayer based on first-principles calculations, including both isotropic and anisotropic strains, confirm a highly strain-dependent manganese partial density of states. Spin-orbit coupling is included which indicates either out-of-plane perpendicular magnetic anisotropy (PMA) or in-plane magnetic anisotropy, dependent on the type of strain whether compressive or tensile, suggesting that MnGaN-2D is magnetoelastic. The MnGaN-2D PMA is further supported by superconducting quantum interference device magnetometry measurements which reveal a high spin polarization of ~ 79 % at room temperature.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Strain-dependent insulating state and Kondo effect in epitaxial SrIrO 3 films

The large spin-orbit coupling in iridium oxides plays a significant role in driving novel physical behaviors, including emergent phenomena in the films and heterostructures of perovskite and Ruddlesden-Popper iridates. Here, in this Letter, we study the role of epitaxial strain on the electronic behavior of thin SrIrO 3 films. We find that compressive epitaxial strain leads to metallic transport behavior, but a slight tensile strain shows gapped behavior. Temperature-dependent resistivity measurements are used to examine different behaviors in films as a function of strain. We find Kondo contributions to the resistivity, with stronger effects in films that are thinner and under less compressive epitaxial strain. These results show the potential to tune SrIrO 3 into Kondo insulating states and open possibilities for a quantum critical point that can be controlled with strain in epitaxial films.

36 MATERIALS SCIENCE↗