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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Simultaneously achieved large reversible elastocaloric and magnetocaloric effects and their coupling in a magnetic shape memory alloy

Large reversible caloric effects covering a broad temperature region are essential for high-efficiency and environment-friendly solid-state caloric refrigeration that can potentially replace the traditional vaporcompression-based cooling technology. Here, we report the simultaneously achieved large reversible magnetocaloric and elastocaloric effects in a Ni 43 Co 6 Mn 40 Sn 11 magnetic shape memory alloy. A reversible near-room-temperature magnetic entropy change Δ S m of as high as 19.3 J kg –1 K –1 under 5 T was experimentally obtained and the corresponding adiabatic temperature change Δ T ad was estimated to be 7.7 K. Meanwhile, a large reversible elastocaloric effect with a directly measured Δ T ad up to 7.1 K was attained. The elastocaloric effect exhibits high cyclic stability with no apparent degradation during 380 cycles of loading and unloading. Furthermore, we propose and demonstrate the utilization of the multicaloric approach under the coupled uniaxial stress and magnetic field to enlarge the refrigeration temperature region of reversible caloric effects. By combining the reversible magnetocaloric and elastocaloric effects and the reversible multicaloric effect under the coupling of uniaxial stress and magnetic field in the hysteresis region, large reversible caloric effects covering a broad temperature region from 257 K to 383 K can be obtained. Finally, this study may pave the way for designing advanced caloric materials with cyclically stable and reversible large caloric effects and wide refrigeration temperature region for solid-state refrigeration.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of composition and crystallographic ordering on the ferromagnetic transition in Ni–Co–Mn–In magnetic shape memory alloys

In the present study, the effects of composition and the level of crystallographic ordering were studied in Ni 45 Co 5 Mn 50-X In X magnetic shape memory alloys with X = 13.55, 13.71 and 13.92, in order to reveal the relationship between the Curie temperature (T C ) of the austenite phase and the degree of L2 1 ordering. Various samples were prepared using secondary heat treatments at different temperatures below the order-disorder transition temperature and for different durations, after solution heat treatment, in order to control the degree of ordering. T C s were determined using calorimetric and magnetometry measurements. The relationship between the T C and the degree of order was used to predict the evolution of the order during selected heat treatments. It was shown that the T C of austenite exhibits a monotonous non-linear dependence on the fraction of the L2 1 phase. This relationship was corroborated via ab initio numerical calculations within a mean field approximation. Dependence of the crystallographic order parameter on temperature and duration of secondary heat treatments showed that ordering kinetics is fast, the total degree of order depends only on the annealing temperature and cooling rate for long enough treatments, and maximum achievable degree of order is limited by the low thermal energy available for atomic diffusion at low temperatures. Lastly, small changes in composition were observed to have a significant impact on martensitic transformation temperatures, and a significant but smaller effect on the ferromagnetic transition in these systems.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Role of microstructure on the actuation fatigue performance of Ni-Rich NiTiHf high temperature shape memory alloys

Here, the focus of the present study was to systematically investigate the influence of microstructure on the actuation fatigue performance of a Ni-rich NiTiHf high temperature shape memory alloy (HTSMA). Different aging heat treatments led to the formation of H-phase nano-precipitates with different sizes and morphology within the matrix, enhancing thermo-mechanical stability and enabling control of transformation temperatures. The actuation fatigue testing of specimens was performed until failure through thermally-induced reversible martensitic transformation under a constant stress (300 MPa) with two distinct upper cycle temperatures (UCT) of 300 °C and 350 °C. Consequently, the specimens heated to 700 °C and furnace cooled to 100 °C in 48 h, with relatively large precipitates, failed at average fatigue life of 15,500 cycles and exhibited 1.0% average actuation strain in the 300 °C UCT experiments, while those aged at 550 °C for 3 h, with the precipitate sizes less than 20 nm, attained an average fatigue life of 10,800 cycles and an actuation strain of 2.5%. Samples with intermediate precipitate sizes after aging at 600 °C for 10 h failed at the shortest average fatigue life of 8,200 cycles with an intermediate average actuation strain of 2.0%. Furthermore, increase in UCT decreased the fatigue life and resulted in larger average actuation strains for all samples. Overall, the current findings constitute the first systematic results demonstrating the microstructure dependence of the evolution of actuation strain, irrecoverable strain, and transformation temperatures during actuation fatigue, and actuation fatigue life of the Ni-rich Ni 50.3 Ti 29.7 Hf 20 HTSMA, demonstrating the importance of controlling the H-phase precipitate size.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Acoustic emission analysis of cyclically loaded superelastic shape memory alloy fiber reinforced mortar beams

Superelastic shape memory alloys (SMAs) are metallic alloys that can recover their nonlinear deformations upon unloading. The use of SMAs in cementitious composites as fibers can enable crack recovery and re-centering capabilities. In this study, the crack recovery characteristics of SMA fiber reinforced mortar specimens subjected to flexural cyclic loading are studied through acoustic emission analysis. SMA fiber reinforced mortar specimens with fiber volume ratios of 0.3%, 0.5% and 1.0% are tested under cyclic flexural loads. Acoustic emissions (AE) signals are captured and analyzed to characterize the crack formation and crack width development at each cycle of loading. In addition, the crack width propagation of the specimens is monitored by Digital Image Correlation measurement system and is used as a basis in AE analyses. Results show that the SMA fiber reinforced mortars exhibit considerable re-centering and crack recovery characteristics at large deformation amplitudes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Parallel projection—An improved return mapping algorithm for finite element modeling of shape memory alloys

Here, we present a novel finite element analysis of inelastic structures containing Shape Memory Alloys (SMAs). Phenomenological constitutive models for SMAs lead to material nonlinearities, that require substantial computational effort to resolve. Finite element analysis methods, which rely on Gauss quadrature integration schemes, must solve two sets of coupled differential equations: one at the global level and the other at the local, i.e. Gauss point level. In contrast to the conventional return mapping algorithm, which solves these two sets of coupled differential equations separately using a nested Newton procedure, we propose a scheme to solve the local and global differential equations simultaneously. In the process we also derive closed-form expressions used to update the internal/constitutive state variables, and unify the popular closest-point and cutting plane methods with our formulas. Numerical testing indicates that our method allows for larger thermomechanical loading steps and provides increased computational efficiency, over the standard return mapping algorithm.

42 ENGINEERING↗
DOE OSTI2020

On the elastocaloric effect in CuAlBe shape memory alloys: A quantitative phase-field modeling approach

We report the reversible stress-induced phase transformation in shape memory alloys (SMAs) is a dissipative process during which heat is absorbed or released. The inherent temperature variations inside the material has an elastocaloric effect (eCE) with appealing applications in solid-state cooling technology such as compact and efficient on-board refrigeration system for eletronic devices. In this manuscript, we conduct the first study of eCE of CuAlBe SMAs utilizing phase-field modeling. For an applied stress of 500 MPa, the results for polycrystalline Cu-Al11-2Be (at. %) show a minimum adiabatic unloading temperature change of -10 K over a pseudoelastic window of 40 K. In the absence of plastic deformation, the material demonstrates good reproducibility of the eCE over a few loading–unloading cycles. The presence of plastic deformation is found to cause functional fatigue that deteriorates the cooling capacity; however, the coefficient of performance only decreases from 9.04 to 8.03, which is still a very good value. These results place CuAlBe as a frontrunner SMA for solid-state cooling compared to the expensive NiTi.

36 MATERIALS SCIENCE↗
DOE OSTI2026

PET waste- and bio-derived imine vitrimers for shape-memory, intrinsic flame-retardant, and recyclable carbon fiber composites

Developing circular multifunctional vitrimers and carbon fiber–reinforced polymers (CFRPs) that are simultaneously recyclable, mechanically robust, and intrinsically flame retardant remains a major challenge. Here, in this study, we report multifunctional vitrimers and their carbon fiber–reinforced vitrimer (CFRV) composites, where the vitrimer design integrates closed-loop recyclability, enhanced interfacial adhesion, and intrinsic flame retardancy within a single materials platform. The vitrimer matrix is synthesized from post-consumer polyethylene terephthalate (PET) waste and a vanillin-derived phosphorus-containing crosslinker, forming an imine-based network. The resulting vitrimer resin exhibits high tensile strength, thermal healability, repeated reprocessability, programmable shape memory, and rapid chemical depolymerization under mild conditions. Amine-functionalized carbon fibers significantly improve fiber–matrix interfacial bonding, yielding CFRVs with tensile strengths up to 789 MPa and complete recovery of structurally intact fibers after chemical recycling. The phosphorus-rich aromatic network further imparts intrinsic flame retardancy, enabling self-extinguishing behavior without external additives. This work advances a materials design paradigm for next-generation multifunctional, sustainable vitrimers and CFRVs, while simultaneously addressing the recycling challenges associated with both plastic and CFRP waste.

Bio-derived crosslinker↗
DOE OSTI2025

HydroEcoLSTM: A Python package with graphical user interface for hydro-ecological modeling with long short-term memory neural network

Machine learning (ML) is emerging as a promising tool for modeling hydro-ecological processes due to the increasing availability of large environmental data. However, the use of ML requires sufficient programming knowledge due to a lack of a graphical user interface (GUI). In this study, we introduced a GUI package, named HydroEcoLSTM, with the long short-term memory network (LSTM) as the core model, that allows non-ML experts to utilize their domain knowledge to construct complex ML models. We demonstrated the functionalities of HydroEcoLSTM with two practical examples, including (1) predictions of streamflow in both gauged and ungauged catchments and (2) predictions of multiple outputs (i.e., streamflow and isotope transport from two catchments). The simulation results obtained in both case experiments are satisfactory. In the first example, the average Nash–Sutcliffe Efficiency (NSE) for streamflow simulation during the testing period is 0.79 while the application of the trained model in two assumed ungauged catchments also achieves the average NSE of 0.68. In the second example, the average NSE for streamflow and instream isotope simulation during the testing period is 0.71. Ultimately, applications of HydroEcoLSTM with real-world examples demonstrate its potential use for practical applications and research without requiring extensive coding skills.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Transformation-induced fracture toughening in CuAlBe shape memory alloys: A phase-field study

Stress-induced transformation ahead of a crack tip can relax the stress concentration and produce fracture toughness in shape memory alloys (SMAs). In this manuscript, we utilize a nonisothermal phase-field model (PFM) to study the martensitic transformation induced crack tip toughening in CuAlBe SMA. The force-displacement curve, transformation zone and high stress zone in single crystalline samples show high dependency on the grain orientation with respect to the crack alignment. Comparison between isothermal and non-isothermal simulations reveals that the transformation-induced self-heating decreases the toughening capability by increasing the critical transformation stress. Investigating the high stress zones in CuAlBe and the nontransforming CuAl alloy shows that the toughening is obtained by redistributing the stress concentration far from the crack tip, as the high stress zone follows the tip of the transformation zone. Increasing the acuity of the crack tip is found to generate more symmetric martensite wings on both side of the crack axis and a more localized high stress zone. The polycrystal specimen displays higher toughening due to the internal constraints related to the presence of various grains with difference orientations. Depending on the orientation of the grain inclosing the crack tip, the toughening can be lower or higher. Finally, coincidence of the crack tip with a triple junction is found to improve the toughening behavior.

42 ENGINEERING↗
DOE OSTI2015

Large magnetic entropy change and magnetoresistance in a Ni 41 Co 9 Mn 40 Sn 10 magnetic shape memory alloy

A polycrystalline Ni 41 Co 9 Mn 40 Sn 10 (at. %) magnetic shape memory alloy was prepared by arc melting and characterized mainly by magnetic measurements, in-situ high-energy X-ray diffraction (HEXRD), and mechanical testing. A large magnetoresistance of 53.8% (under 5 T) and a large magnetic entropy change of 31.9 J/(kg K) (under 5 T) were simultaneously achieved. Both of these values are among the highest values reported so far in Ni-Mn-Sn-based Heusler alloys. The large magnetic entropy change, closely related to the structural entropy change, is attributed to the large unit cell volume change across martensitic transformation as revealed by our in-situ HEXRD experiment. Furthermore, good compressive properties were also obtained. Lastly, the combination of large magnetoresistance, large magnetic entropy change, and good compressive properties, as well as low cost makes this alloy a promising candidate for multifunctional applications.

36 MATERIALS SCIENCE↗
DOE OSTI2019

In-situ TEM analysis of the phase transformation mechanism of a Cu–Al–Ni shape memory alloy

We report that minimizing phase transformation (PT) hysteresis is of crucial importance for reliability of shape memory alloy (SMA)-based devices, where the lattice strain/stress caused by thermal hysteresis leads to functional degradation. As a result, understanding structural factors that control PT pathway is critical for development of materials with high reversibility. In this study, two distinct PT mechanisms (from γ$'\atop{1}$ martensite to β 1 austenite phase) in Cu–Al–Ni SMAs were revealed by in-situ TEM observation. A growth-dominant conventional PT mechanism shows in the fast quench sample, whereas a nucleation-dominant PT mechanism that suppresses interface propagation and induces high thermal hysteresis displays in the slow quench sample. By characterizing the atomic scale composition and microstructure we discover that slow quenching induces nanoprecipitation that changes chemistry of the matrix alloy, which in turn causes the higher PT hysteresis and temperature, while fast quenching avoids the formation of these nanoprecipitates. Lastly, our finding provides valuable insights into the fabrication of SMAs with better reliability.

36 MATERIALS SCIENCE↗
DOE OSTI2015

APOE effect on Alzheimer's disease biomarkers in older adults with significant memory concern

This study assessed apolipoprotein E (APOE) ε4 carrier status effects on Alzheimer's disease imaging and cerebrospinal fluid (CSF) biomarkers in cognitively normal older adults with significant memory concerns (SMC). Cognitively normal, SMC, and early mild cognitive impairment participants from Alzheimer's Disease Neuroimaging Initiative were divided by APOE ε4 carrier status. Diagnostic and APOE effects were evaluated with emphasis on SMC. Additional analyses in SMC evaluated the effect of the interaction between APOE and [ 18 F]Florbetapir amyloid positivity on CSF biomarkers. SMC ε4+ showed greater amyloid deposition than SMC ε4-, but no hypometabolism or medial temporal lobe (MTL) atrophy. SMC ε4+ showed lower amyloid beta 1-42 and higher tau/p-tau than ε4-, which was most abnormal in APOE ε4+ and cerebral amyloid positive SMC. Lastly, SMC APOE ε4+ show abnormal changes in amyloid and tau biomarkers, but no hypometabolism or MTL neurodegeneration, reflecting the at-risk nature of the SMC group and the importance of APOE in mediating this risk.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Determination of single crystal thermal expansion in Uranium-6wt%Niobium shape memory alloy using in-situ diffraction and modeling of textured polycrystalline samples

In-situ neutron diffraction and ex-situ dilatometry experiments were performed on a chemically banded, quenched uranium-6wt% niobium shape memory alloy to study the impact of deformation-(detwinning-) induced texture on the evolution of thermally induced strains (and associated stresses). Thermal heating and cooling cycles between 5K and 473K were performed in-situ with neutron diffraction, and the lattice strain evolution is reported for the observed monoclinic α" phase. Comparisons between the measured diffraction strains and macroscopic dilatometry experiments reveal relationships between micro- and macro-level thermal expansion. Softening of the texture during heating suggests that twin boundary motion can accommodate the large internal thermal strains which are approximately 2% greater than that typically observed during the 175K heating interval used to age more randomly oriented polycrystalline material. Assuming weak constraint of neighboring grains in randomly textured polycrystals, the single crystal thermal expansion tensor is extracted from measurements of lattice strains over the range 5K to 473K. Predictions of polycrystalline thermal expansion, based upon this single crystal thermal expansion tensor, are shown to compare favorably with bulk thermal expansion observations of the as quenched microstructure. However, such a lower-bound estimate is insufficient to explain all aspects of the behavior of the textured material, where the matrix is not isotropic. In conclusion, it is hypothesized that relaxation processes which occur within the quenched microstructure during heating are responsible for the distinct thermal expansion behavior observed during the initial heating cycle compared to cooling and subsequent cycling.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Modeling injection-induced fault slip using long short-term memory networks

Stress changes due to changes in fluid pressure and temperature in a faulted formation may lead to the opening/shearing of the fault. This can be due to subsurface (geo)engineering activities such as fluid injections and geologic disposal of nuclear waste. Such activities are expected to rise in the future making it necessary to assess their short- and long-term safety. Here, a new machine learning (ML) approach to model pore pressure and fault displacements in response to high-pressure fluid injection cycles is developed. The focus is on fault behavior near the injection borehole. To capture the temporal dependencies in the data, long short-term memory (LSTM) networks are utilized. To prevent error accumulation within the forecast window, four critical measures to train a robust LSTM model for predicting fault response are highlighted: (i) setting an appropriate value of LSTM lag, (ii) calibrating the LSTM cell dimension, (iii) learning rate reduction during weight optimization, and (iv) not adopting an independent injection cycle as a validation set. Several numerical experiments were conducted, which demonstrated that the ML model can capture peaks in pressure and associated fault displacement that accompany an increase in fluid injection. The model also captured the decay in pressure and displacement during the injection shut-in period. Further, the ability of an ML model to highlight key changes in fault hydromechanical activation processes was investigated, which shows that ML can be used to monitor risk of fault activation and leakage during high pressure fluid injections.

58 GEOSCIENCES↗
DOE OSTI2013

Simultaneous probing of phase transformations in Ni-Ti thin film shape memory alloy by synchrotron radiation-based X-ray diffraction and electrical resistivity

Nickel–Titanium (Ni–Ti) thin film shape memory alloys (SMAs) have been widely projected as novel materials which can be utilized in microdevices. Characterization of their physical properties and its correlation with phase transformations has been a challenging issue. In the present study, X-ray beam diffraction has been utilized to obtain the structural information at different temperatures while cooling. Simultaneously, electrical resistivity (ER) was measured in the phase transformation temperature range. The variation of ER and integral area of the individual diffraction peaks of the different phases as a function of temperature have been compared. A mismatch between the conventional interpretation of ER variation and the results of the XRD data has been clearly identified. - Highlights: ► Phase transformation characterization of Ni–Ti thin film SMA has been carried out. ► Simultaneous monitoring of the XRD and ER with temperature is performed. ► The variation of ER and integral area of the diffraction peaks have been compared. ► A shift of the transformation temperatures obtained by two techniques is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Comparative study of structure formation and mechanical behavior of age-hardened Ti–Nb–Zr and Ti–Nb–Ta shape memory alloys

This work sets out to study the peculiar effects of aging treatment on the structure and mechanical behavior of cold-rolled and annealed biomedical Ti–21.8Nb–6.0Zr (TNZ) and Ti–19.7Nb–5.8Ta (TNT) (at.%) shape memory alloys by means of transmission electron microscopy, X-ray diffractometry, functional fatigue and thermomechanical testing techniques. Dissimilar effects of aging treatment on the mechanical behavior of Zr- and Ta-doped alloys are explained by the differences in the ω-phase formation rate, precipitate size, fraction and distribution, and by their effect on the alloys' critical stresses and transformation temperatures. Even short-time aging of the TNZ alloy leads to its drastic embrittlement caused by “overaging”. On the contrary, during aging of the TNT alloy, formation of finely dispersed ω-phase precipitates is gradual and controllable, which makes it possible to finely adjust the TNT alloy functional properties using precipitation hardening mechanisms. To create in this alloy nanosubgrained dislocation substructure containing highly-dispersed coherent nanosized ω-phase precipitates, the following optimum thermomechanical treatment is recommended: cold rolling (true strain 0.37), followed by post-deformation annealing (600 °C, 15–30 min) and age-hardening (300 °C, 30 min) thermal treatments. It is shown that in TNT alloy, pre-transition diffraction effects (diffuse reflections) can “mask” the β-phase substructure and morphology of secondary phases. - Highlights: • TNZ alloy is characterized by much higher ω-phase precipitation rate than TNT alloy. • Difference in precipitation rates is linked to the difference in Zr and Ta diffusion mobility. • Aging of nanosubgrained TNZ alloy worsens its properties irrespective of the aging time. • Aging time of nanosubgrained TNT alloy can be optimized to improve its properties.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Microstructure and transformation behavior of Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25} high temperature shape-memory alloy with Sc micro-addition

NiTiPd shape-memory alloys (SMAs) are potential functional materials for use as solid-state actuators in the temperature range 100–250 °C. The present study investigates the effect of 1.0 at.% Sc micro-addition to Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25} alloy, Sc replacing either Ti or Ni. Results show that all the three alloys studied have stable transformation behavior on stress-free thermal cycling and hence, are suitable for cyclic actuation applications. However, the addition of Sc to NiTiPd alloy leads to decrease of transformation temperatures, the magnitude of decrease being greater for the alloy with Sc replacing Ni. The martensite finish (M{sub f}) temperature of 181 °C for the NiTiPd alloy decreased to 139 °C for Sc replacing Ti and 83 °C for Sc replacing Ni. Also, the indentation modulus of NiTiPdSc (Sc replacing Ni) alloy is found to be significantly low compared to the other alloys. Analysis indicates that the observed differences in the alloy properties are related to the solubility of Sc in the NiTiPd matrix. While the quaternary NiTiPdSc alloy, Sc replacing Ti, has a single phase microstructure, the alloy with Sc replacing Ni shows the presence of Sc-rich and TiPd-type second phases in the microstructure. TEM examination revealed that the TiPd-type phase has a distinct rod-like morphology (30–50 nm) arranged in a grid-like structure. The transformation and indentation behavior of the alloys is elucidated using thermodynamic calculations of frictional energy and an electronic structure based analysis. - Highlights: • TEM of Ni{sub 23.7}Ti{sub 50.3}Pd{sub 25}Sc{sub 1} showed distinct grid of TiPd-type phase nanorods < 50 nm. • Stress-free thermal cycling of all the three alloys showed stable transformation behavior. • Ni{sub 24.7}Ti{sub 49.3}Pd{sub 25}Sc{sub 1} and Ni{sub 23.7}Ti{sub 50.3}Pd{sub 25}Sc{sub 1} showed single and multiphase structures. • Sc micro-addition (1 at.%) to Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25} alloy decreased TTs significantly. • Ni{sub 23.7}Ti{sub 50.3}Pd{sub 25}Sc{sub 1} exhibited lower modulus of 67 GPa to 85 GPa of Ni{sub 24.7}Ti{sub 50.3}Pd{sub 25}.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Study of the microstructure evolution of heat treated Ti-rich NiTi shape memory alloy

Martensitic evolution in Ti-rich NiTi alloy, Ti50.5Ni49.5, has been investigated as a function of annealing, solution treatment and a combination thereof and a detailed electron microscopic investigation carried out. Self-accommodated martensite plates resulted in all heat treated samples. Martensitic < 011 > type II twins, which are common in NiTi shape memory alloys, was found in both as-received and heat-treated samples. Solution treated samples, additionally, showed {11-1} type I twinning was also found in samples that have been annealed after solution-treatment. Another common feature of the microstructure in both as-received and heat treated samples is the formation of Ti{sub 2}Ni precipitates. The size, number and dispersions of these precipitates can be controlled by resorting to a suitable heat treatment e.g. solution treatment.

36 MATERIALS SCIENCE↗