Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “microstructure design”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

A leaf-molded transparent triboelectric nanogenerator for smart multifunctional applications

Transparent, flexible and highly efficient portable power sources are essential components of the next generation electronics and optoelectronic devices. However, complicated technology, expensive cost, environmental pollution and low-efficient output have limited its development. Herein, based on periodic contact/separation between human skin and the microstructured polydimethylsiloxane (PDMS) film, we demonstrate a transparent flexible triboelectric nanogenerator (TENG) through a relatively simple, low-cost, environmental-friendly and high-efficient method. For the first time, the natural leaves with rich surface textures were introduced to make microstructures on PDMS films as effective friction surface in the TENG. Furthermore, long silver nanowires (200 µm in length at least) through novel synthesis were assembled as high-performance electrode, resulting in the entirely flexible and transparent TENG. Owing to the unique design, the transparent flexible TENG was eventually obtained with an enhanced output (Voc=56 V; Isc=3.1 μA) and remarkable transparency (88%). Owing to compelling features of the TENG, a self-powered user-interactive wearable system was successfully established by integrating a flexible electrochromic device (ECD). The remarkable color-tunable ability via mechanical control of our system, highly inspired by chameleons, is potentially useful in military camouflage, monitoring human activity visually, as well as replacing performance of face change in Sichuan Opera. Therefore, this research is a substantial advancement toward the construction of transparent nanogenerator and its multifunctional applications in energy conversation, wearable electronics, healthcare, culture experience, and even environmental protection.

42 ENGINEERING↗
DOE OSTI2025

High-throughput synthesis of high-entropy alloys via parallelized electric field assisted sintering

Materials discovery and design is an expensive and time-consuming process, though necessary to advance many engineering fields. In this work, a novel tooling design is utilized in conjunction with electric field assisted sintering (EFAS) to effectively create a new high-throughput synthesis technique: parallelized EFAS. Through this technique, a wide range of material compositions and geometries can be synthesized in parallel as isolated samples or as part of contiguous arrays. Multiple tooling designs are explored to examine both the flexibility and limitations of the technique. A series of increasing complex alloys is produced simultaneously using in situ alloying, beginning with pure Ni and adding equimolar constituents up to the septenary high-entropy alloy AlCoCrCuFeMnNi. Microstructural characterization reveals each sample is effectively fully dense and chemically homogenous while exhibiting phases in agreement with CALPHAD predictions. Scalability of parallelized EFAS is then experimentally demonstrated and the implications for materials discovery and automation are discussed.

36 - MATERIALS SCIENCE↗
DOE OSTI2018

A compact and flexible induction furnace for in situ X-ray microradiograhy and computed microtomography at Elettra: design, characterization and first tests

A compact and versatile induction furnace for in situ high-resolution synchrotron and laboratory hard X-ray microradiography and computed microtomography is described. The furnace can operate from 773 to 1723 K. Its programmable controller enables the user to specify multiple heating and cooling ramp rates as well as variable dwell times at fixed temperatures allowing precise control of heating and cooling rates to within 5 K. The instrument can work under a controlled atmosphere. Thanks to the circular geometry of the induction coils, the heat is homogeneously distributed in the internal volume of the graphite cell ( ca . 150 mm 3 ) where the sample holder is located. The thermal gradient within the furnace is less than 5 K over a height of ca . 5 mm. This new furnace design is well suited to the study of melting and solidification processes in geomaterials, ceramics and several metallic alloys, allowing fast heating (tested up to 6.5 K s -1 ) and quenching (up to 21 K s -1 ) in order to freeze the sample microstructure and chemistry under high-temperature conditions. The sample can be held at high temperatures for several hours, which is essential to follow phenomena with relatively slow dynamics, such as crystallization processes in geomaterials. The utility of the furnace is demonstrated through a few examples of experimental applications performed at the Elettra synchrotron laboratory (Trieste, Italy).

Kudrna Prašek, Marko↗
DOE OSTI2014

Analysis of Phase Transformation Studies in Solute Addition Alloys

Components serving in a nuclear reactor plant must withstand a very harsh environment including extended time at elevated temperatures, neutron irradiation, stress, and/or corrosive media. The many modes of degradation are complex and very depending on material and service locations. However, understanding and managing materials degradation is paramount for the continued safe and reliable operation of nuclear power plants. For the reactor core and primary systems, several key areas have been identified. Thermomechanical considerations such as aging and fatigue must be examined. Irradiation-induced processes must also be considered for higher fluences under the life extension consideration of the current light water reactors (LWRs), which particularly includes the influence of radiation-induced segregation (RIS), swelling, and precipitation on component hardening and embrittlement. Corrosion takes many forms within the reactor core, although irradiation-assisted stress corrosion cracking (IASCC) and primary water stress corrosion cracking (PWSCC) are of high interest in extended life scenarios. Research in these areas can build upon other ongoing programs in the LWR industry as well as other reactor materials programs (such as fusion and fast reactors) to help resolve these issues for extended LWR life. Type 304 and 316 stainless steels are classic structural materials used in LWRs. A set of well designed type 304 and 316 variants by changing the amount of a single solute element were irradiated using the BOR-60 fast breeder reactor at ~320°C in Russia. This set of alloy samples has been used in this task to characterize detailed microstructural evolution and measure magnetic phase, swelling and hardness. This report summarizes the detailed microstructural results, characterized using conventional and scanning transmission electron microscopy (CTEM/STEM) and energy dispersive X-ray spectroscopy (EDS), and the newly developed model of strength factor for estimating radiation hardening. The results provide invaluable insights into understanding degradation mechanisms of key components and assists in the prediction of the life of similar materials and the base knowledge required to develop advanced radiation resistant alloys. The effect of solute elements on microstructural evolution under neutron irradiation is explored. The approximate correlation between microstructure changes and radiation hardening is established. The major results and implications are discussed below.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2019

Identification and Shipment Progress of the INL and LANL Samples to Be Received at ORNL

Ferritic-martensitic steel Grade 92, with T91 as a reference, together with austenitic stainless steel (or Incoloy Alloy) 800H and its grain-boundary-engineered version 800H-TMP (ThermoMechanical Processing), is investigated in this project. A total of fifteen Grade 92 samples from two or three heats, four T91 samples from two heats, and six 800H and six 800H-TMP samples from one heat were selected, which were primarily irradiated in the Advanced Test Reactor of Idaho National Laboratory (INL), with the rest in the High Flux Isotope Reactor of Oak Ridge National Laboratory (ORNL), BOR-60 of Russia, and Phénix reactor of France. The samples were irradiated in the temperature range of 241 to 720°C and a dose range of 1.28 to ~70 displacements per atom. All the INL samples, most of the ORNL samples, and part of the LANL (Los Alamos National Laboratory) samples from the ATR, BOR-60 and Phénix reactors have been received at the Irradiated Materials Examination and Testing (IMET) hot cell facility and Low Activation Materials Design and Analysis (LAMDA) laboratory of ORNL. Post-irradiation examination of the received samples is in progress at ORNL. The effects of irradiation temperature, dose, reactor (e.g., dose rate, neutron-spectrum-induced difference in transmutation), TMP, and heats variation on the microstructures and mechanical properties of the samples will be evaluated.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Establishment of a Vertically Integrated Domestic Manufacturing Process for Production of Substrates Needed for Manufacture of Gas Diffusion Layers

In this project, AvCarb, LLC evaluated the baseline performance metrics of commercial carbon veils and their corresponding Gas Diffusion Layers (GDLs) with the goal of establishing an optimized, vertically integrated production system for wet-laid nonwoven substrates used in gas diffusion media for electrochemical energy storage and conversion devices. Mechanical testing and microstructural characterization were conducted and used to develop a multiscale computational model capable of simulating and predicting the performance of GDLs in fuel cells. Although the project successfully generated foundational transport and modeling data, it was terminated prior to identifying the critical GDL design parameters necessary for full optimization. The program aimed to improve carbon veil fabrication through enhanced fiber dispersion, fiber-fiber adhesion control, and improved web formation, enabling the production of high-quality, uniform substrates. Simulations were intended to guide mixing and solution delivery system design and process conditions, followed by production-scale trials to evaluate fiber dispersion, web uniformity, and mechanical robustness. At full deployment, the proposed production line would have been capable of producing approximately 650,000 m² of carbon veil annually. This capability remains strategically important, as the United States currently lacks a domestic source of wet-laid nonwoven carbon substrates that satisfy the stringent quality requirements for fuel-cell GDLs and electrolyzers representing an ongoing supply-chain vulnerability. Beyond supply-chain benefits, the project established a robust benchmarking dataset for existing commercial carbon veils while advancing next-generation material concepts targeting improved performance and manufacturing consistency.

Olson, Cynthia Lemay↗
DOE OSTI2019

A Reactive Element Approach to Improve Fracture Healing in Metallic Systems

Self-healing materials demonstrate the ability to close fractures and regain mechanical integrity after a catastrophic failure. However, self-healing in metals can be inhibited by the natural tendency for technologically-relevant metallic systems to oxidize on the crack surface. This study seeks to provide a thermodynamically-based mechanism to enhance healing capability at a solid/liquid interface through alloys designed with a reactive element alloying addition possessing a lower free energy of oxide formation than the parent element. In this study, model Sb-Cu and Sb-Zn systems enable comparisons between mechanistic behaviors based only on thermodynamic reactivity. Mechanical and microstructural investigation demonstrated that the more reactive alloying addition resulted in more effective bonding through increasing bond area and load-bearing capacity of the system. The improved bonding was attributed to improved wetting and reduction of the passivating surface oxide across an interface. The work has potential to advance self-healing capabilities in metallic systems through more appropriate alloy selection to enable improved healing.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Stress-Controlled Creep–Fatigue of an Advanced Austenitic Stainless Steel at Elevated Temperatures

Creep–fatigue interaction occurs in many structural components of high-temperature systems operating under cyclic and steady-state service conditions, such as in nuclear power plants, aerospace, naval, and other industrial applications. Thus, understanding micromechanisms governing high-temperature creep–fatigue behavior is essential for safety and design considerations. In this work, stress-controlled creep–fatigue tests of advanced austenitic stainless steel (Alloy 709) were performed at a 400 MPa stress range and 750 °C with tensile hold times of 0, 60, 600, 1800, and 3600 s, followed by microstructural examinations. The creep–fatigue lifetime of the Alloy 709 was found to decrease with increasing hold time until reaching a saturation level where the number of cycles to failure did not exhibit a significant decrease. Softening behavior was observed at the beginning of the test, possibly due to the recovery of entangled dislocations and de-twining. In addition, hysteresis loops showed ratcheting behavior, although the mean stress was zero during creep–fatigue cycling, which was attributed to activity of partial dislocations. Microstructural examination of the fracture surfaces showed that fatigue failure dominated at small hold times where the cracks initiated at the surface of the sample. Larger creep cracks were found for longer hold times with a lower probability of dimpled cavities, indicating the dominance of creep deformation. The results were compared with other commonly used stainless steels, and plausible reasons for the observed responses were described.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2001

Detection and Characterization of Imperfections in Composite Pressure Vessels

The thermographic evaluation of composite structures for delaminations, disbonds, inclusions, porosity and microcracking has proven to be a valuable asset in the field of nondestructive testing. Coupling large area coverage, variable sensitivity and minimal surface contact with a photographic type image representation of structural anomalies; thermography has become a primary inspection method for composite structures. Thermography works well for locating both surface and subsurface defects in most composite systems ranging in thickness of up to 0.25 inch (0.64 cm) or more. The thermographic method for inspection of composite structures typically involves applying an external source of heat to the structure and then recording the changes in the surface heat profile manifested by embedded defects or by material property variations. If these temperature variations are large enough and an infrared camera with sufficient sensitivity is used, then the material or structural abnormality can be detected and referred back to its source. Interpreting the information given in a thermogram, can be a difficult task under ideal circumstances and extremely challenging in a real world setting. Variables including depth, thermal conductivity, orientation and size of the abnormality can all have a great influence on how its heat pattern will be seen by the imager. The work discussed in this paper illustrates how the microstructure of several commonly found defects in composite structures relate to their thermographic image counterpart. Two test cases are studied herein, including a large graphite/epoxy RP-1 fuel tank and a graphite composite cryogenic fuel feedline. The structures used in this study were designed to serve as manufacturing proof of concept specimens and to undergo hydroburst testing to verify manufacturing practices and structural design. Prior to hydrostatic testing the structures underwent 100% thermographic evaluation to ensure that no manufacturing or handling damage was present. Due to a large inclusion found in the feedline, it was pulled from service and dissected without performing the hydroproof The thermographic indications found in the RP-1 tank were below critical limits so it underwent a complete hydroproof loading series and finally a hydroburst. Following the hydroburst samples were cut from the tank in regions where thermography had located damage before the test. These regions were thermographically and then were cross-sectioned and photomicrographed.

Walker, James L.↗
NASA NTRS2005

Soldering Tested in Reduced Gravity

Whether used occasionally for contingency repair or routinely in nominal repair operations, soldering will become increasingly important to the success of future long-duration human space missions. As a result, it will be critical to have a thorough understanding of the service characteristics of solder joints produced in reduced-gravity environments. The National Center for Space Exploration Research (via the Research for Design program), the NASA Glenn Research Center, and the NASA Johnson Space Center are conducting an experimental program to explore the influence of reduced gravity environments on the soldering process. Solder joint characteristics that are being considered include solder fillet geometry, porosity, and microstructural features. Both through-hole (see the drawing and image on the preceding figure) and surface-mounted devices are being investigated. This effort (the low-gravity portion being conducted on NASA s KC-135 research aircraft) uses the soldering hardware currently available on the International Space Station. The experiment involves manual soldering by a contingent of test operators, including both highly skilled technicians and less skilled individuals to provide a skill mix that might be encountered in space mission crews. The experiment uses both flux-cored solder and solid-core solder with an externally applied flux. Other experimental parameters include the type of flux, gravitational level (nominally zero,

Struk, Peter M.↗
DOE OSTI2019

Investigation of Powder Processing, Heat Treating, and Texturing to Improve Gas Atomized alnico Magnets for use in Electric Drive Motors

Alnico permanent magnet materials have been proposed as a rare earth free permanent magnet alternative during an ongoing search to replace rare earth permanent magnets that are used for interior permanent magnet motors, a common motor found in electric vehicles. A powder processing approach was used to study two alnico alloys (Full-Co and lower cost Co-Lean, both with enhanced coercivity) to anticipate high volume manufacturing needed to supply millions of permanent magnets to interior permanent magnet motors. In this study the two alloys were gas atomized, compression molded, and solid-state sintered to fabricate near-final shape alnico magnets. The Full-Co displayed abnormal grain growth (resulting in >1 mm size grains) during sintering while the Co-Lean did not (~20 μm – 400 μm sized grains depending on the sintering hold times). Solid state grain alignment was used to promote a <001> textured (easy axis) microstructure to enhance magnetic properties, yet both alloys did not show predicted grain alignment behavior. Comparisons of the powder processing, microstructures, and magnetic properties of the two alloys will be discussed, as well as an evaluation as to why non-theoretical processing behavior of the Full-Co and Co-Lean alnico permanent magnets is occurring. Preliminary interior permanent magnet motor designs for alnico magnets are discussed, as this is the overarching objective for powder-based alnico permanent magnets.

Rinko, Emily↗
DOE OSTI2023

Revisiting Wagner’s Criteria to Predict Establishment and Retention of Alumina Scales on Ternary NiCrAl Alloys

Despite the advent of numerical modeling approaches and high-performance computing infrastructure, the design and development of corrosion-resistant high temperature alloys (> 500 °C) continue to be largely empirical and typically involve extensive experimentation. This is mainly due to the lack of a single unified physics-based model that can address the impact of multiple competing factors such as time, environment, alloy composition, microstructure, and geometry. The classical Wagner’s criteria have been foundational to estimate the minimum concentrations required of an oxide-forming element to establish and sustain a protective oxide scale. However, the formulation is primarily limited to lower-order alloy systems (binary alloys) and ignores the time dependence of subsurface compositional changes in the alloy. The lack of key data on the temperature and composition dependence of the solubility and transport of oxidants in multicomponent-multiphase alloys further exacerbates the problem. In the present work, a few of these limitations were addressed using a flux-based approach (FLAP) which tracks the spatiotemporal evolution of the fundamental flux balance between oxygen and the oxide-forming elements to enable the prediction of the formation of an external alumina scale in ternary NiCrAl alloys. In conclusion, the modeling results were validated with the literature findings and additional experimental work conducted in the present work.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Strong, ductile, and hierarchical hetero-lamellar-structured alloys through microstructural inheritance and refinement

The strength−ductility trade-off exists ubiquitously, especially in brittle intermetallic-containing multiple principal element alloys (MPEAs), where the intermetallic phases often induce premature failure leading to severe ductility reduction. Hierarchical heterogeneities represent a promising microstructural solution to achieve simultaneous strength−ductility enhancement. However, it remains fundamentally challenging to tailor hierarchical heterostructures using conventional methods, which often rely on costly and time-consuming processing. Here, we report a multiscale microstructural inheritance and refinement strategy to process “structural hierarchy precursors” in as-cast heterogeneous Al 0.7 CoCrFeNi MPEAs, which lead directly to a hierarchical hetero-lamellar structure (HLS) after simple rolling and annealing. Interestingly, it takes only 10 min of annealing time, two orders of magnitude less than that required to render the state-of-the-art properties during conventional processing of Al 0.7 CoCrFeNi, for us to achieve record-high strength−ductility combinations via the hierarchical HLS design that sequentially stimulates multiple unusual deformation and reinforcement mechanisms. In particular, the HLS-enabled high hetero-deformation-induced (HDI) internal stress triggers profuse <111>-type dislocations on over five independent slip systems in the supposedly brittle intermetallic phase and activates extensive stacking faults (SFs) and nanotwinning in the adjoining soft phase with a rather high SF energy. These unexpected, dynamically reinforcing hetero-deformation mechanisms across multiple length scales facilitate high sustained HDI strain hardening, along with a salient microcrack-mediated extrinsic ductilization effect, suggesting that the proposed microstructural inheritance and refinement strategy provides an efficient, fast, and low-cost approach to overcome the strength−ductility trade-off in a broad range of structural materials.

Science & Technology - Other Topics↗
DOE OSTI2014

Approaching attometer laser vibrometry

The heterodyne two-beam interferometer has been proven to be the optimal solution for laser-Doppler vibrometry regarding accuracy and signal robustness. The theoretical resolution limit for a two-beam interferometer of laser class 3R (up to 5 mW visible measurement-light) is in the regime of a few femtometer per square-root Hertz and well suited to study vibrations in microstructures. However, some new applications of RF-MEM resonators, nanostructures, and surface-nano-defect detection require resolutions beyond that limit. The resolution depends only on the noise and the sensor sensitivity to specimen displacements. The noise is already defined in nowadays systems by the quantum nature of light for a properly designed optical sensor and more light would lead to an inacceptable influence like heating of a very tiny structure. Thus, noise can only be improved by squeezed-light techniques which require a negligible loss of measurement light which is impossible for almost all technical measurement tasks. Thus, improving the sensitivity is the only possible path which could make attometer laser vibrometry possible. Decreasing the measurement wavelength would increase the sensitivity but would also increase the photon shot noise. In this paper, we discuss an approach to increase the sensitivity by assembling an additional mirror between interferometer and specimen to form an optical cavity. A detailed theoretical analysis of this setup is presented and we derive the resolution limit, discuss the main contributions to the uncertainty budget, and show a first experiment proving the sensitivity amplification of our approach.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2004

Structured-groove phase gratings for control and optimization of the spectral efficiency

Phase gratings are used as dispersers in a variety of imaging spectroscopic instruments. However, conventional phase gratings provide limited spectral range and flexibility to fully optimize instrument performance for challenging applications. Presented here is a new design method that tailors and optimizes the spectral efficiency by introducing an arbitrary structure into the grating groove profile.

diffraction gratings↗
DOE OSTI2026

Physics-informed machine learning exploration of Na storage mechanisms in disordered carbon

Sodium-ion batteries are a cost-effective, sustainable alternative to lithium-ion systems for large-scale energy storage. However, optimizing sodium storage in carbon-based anodes with microstructural complexity and atomic disorder remains a major challenge. The intrinsic inhomogeneity of these materials produces diverse local environments, making it difficult for conventional methods to predict and control ion dynamics. Hard carbon (HC) anodes, composed of ranges of ordered-to-disordered graphitic and amorphous nanodomains, offer tunable ion storage and rate capacity, yet rationale design remains a challenge due to poorly understood correlation between local atomic feature and ion transport mechanism. Here, to address this challenge, we introduce a data-driven framework that integrates validated machine-learned interatomic potentials, large-scale molecular dynamics simulations, and machine learning to elucidate sodium transport mechanisms as a function of carbon and sodium loading densities. By computing per-ion structural descriptors and applying unsupervised learning, we identify distinct diffusion modes governed by microscopic features. Supervised analysis and correlation mapping then establish quantitative links between these transport regimes and processing variables such as bulk carbon density and sodium content. This physics-informed approach establishes quantitative structure–transport relationships and offers actionable design principles for engineering high-performance HC anodes.

Data-driven framework↗
DOE OSTI2024

Two–Photon Printing of Base–Catalyzed Resins Involving Thiol–Michael Network Formation

Two-photon printing is accomplished using a photobase generator, 2-(2-nitrophenyl)-propyloxycarbony tetramethyl guanidine, to locally catalyze thiol-ene coupling between multifunctional monomers while mitigating chain-growth polymerization with free radical scavengers. Microstructures printed from base-catalyzed resins exhibit higher resolution (linewidths < 400 nm) and lower print error (<3%) than analogous microstructures printed using a photosensitive, free radical initiator. Further, Raman spectroscopy reveals that resins polymerized using the photobase generator in the presence of free radical scavengers exhibit higher selectivity of thiol-ene coupling over radical polymerization, resulting in stiffer, more uniform polymer networks. The base-catalyzed resins are capable of producing 3D microstructures printed with high accuracy and minimal post-processing defects. As a result, a direct comparison between free radical and base-initiated resins highlights the need for mindful consideration of how chemical reaction pathway influences printability and network end-properties when designing resins.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Investigation of the Toughening Mechanism of PHBV/PBAT with a Novel Hyperbranched Ethylenediamine Triazine Polymer Based Modifier: The Formation of the Transition Layer and the Microcrosslinking Structure

A new type of designed hyperbranched ethylenediamine trazine polymer (HBETP) is successfully synthesized and characterized based upon NMR and GPC. The prepared HBETP is used to modify the poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/poly(butylene adipate-co-terephthalate) (PBAT) blends. The effect of HBETP on the microstructure, mechanical properties and thermal properties of the blends is studied. The results indicate that upon addition of 1.0 wt% of HBETP, the impact strength of the PHBV/PBAT blends is increased by 47.1%; ∆T{sub g} of the blends decreases from 53.2 to 49.9 °C. These results, together with the morphology analysis of the fractured surface of the blends, conclude the formation of the transition layer between PHBV and PBAT. Also, the XRD result shows that the addition of HBETP can limit the growth of the PHBV crystals and causes the decrease of both the crystallinity and the grain crystalline size. The DSC result demonstrates that the addition of HBETP mainly affects the crystallization of the HB-HV binary eutectic region within PHBV. The mechanism of PHBV/PBAT toughening is due to the formation of the strong physical hydrogen bonding and the chemical micro-crosslinking between HBETP and PHBV/PBAT, which is proposed based on XPS characterization.

77 NANOSCIENCE AND NANOTECHNOLOGY↗