Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Behavior”

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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Controlled Shape Memory Behavior of a Smectic Main-Chain Liquid Crystalline Elastomer

Here, we describe how a smectic main-chain liquid crystalline elastomer (LCE), with controlled shape memory behavior, is synthesized by polymerizing a biphenyl-based epoxy monomer with an aliphatic carboxylic acid curing agent. Microstructures of the LCEs, including their liquid crystallinity and cross-linking density, are modified by adjusting the stoichiometric ratio of the reactants to tailor the thermomechanical properties and shape memory behavior of the material. Thermal and liquid crystalline properties of the LCEs, characterized using differential scanning calorimetry and dynamic mechanical analysis, and structural analysis, performed using small-angle and wide-angle X-ray scattering, show that liquid crystallinity, cross-linking density, and network rigidity are strongly affected by the stoichiometry of the curing reaction. With appropriate structural modifications it is possible to tune the thermal, dynamic mechanical, and thermomechanical properties as well as the shape memory and thermal degradation behavior of LCEs.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Unique Phase Behavior of Inverse Tapered Block Copolymers: Self-Consistent Field Theory and Molecular Dynamics Simulations

Using theory and simulation, we study the microphase separated structures of inverse tapered block copolymers. These are AB block copolymers with a gradient region inserted between the pure A and B blocks that smoothly changes in composition from B to A, with the B-side of the taper bonded to the pure A block. Tapering is a means to increase miscibility between polymer blocks, and by controlling the length of the taper, the phase behavior and domain spacing can be adjusted. As opposed to better known ABAB tetrablock copolymers that also have four alternating A-rich and B-rich regions, here the intermediate region has a partially mixed composition, promoting relatively diblock-like behavior for shorter inverse tapers or low segregation strength but unique behavior as a function of increasing segregation strength for some systems. In particular, for systems in which 50% of the backbone is the taper, the larger of the two pure end blocks - composed of the overall majority component - can phase separate analogously to the minority component of a diblock copolymer, creating cylinder and network phases in which the majority component’s pure block is the minority phase in a matrix of a relatively disordered mixture of the tapered region and the minority component’s pure block.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of End-Block Dynamics on Deformation Behavior of Thermoresponsive Elastin-like Polypeptide Hydrogels

End-block association dynamics are known to influence deformation behavior in block copolymer systems. The ability to obtain precisely sequence controlled systems can help inform this deformation behavior, which is often influenced by dispersity in sequence and molar mass. Elastin-like polypeptides (ELPs) are a class of protein that consists of a sequence of five amino acids (XPGVG) that thermoresponsively aggregate in solution. These ELPs can be used as end-blocks in triblock fusion proteins with coiled-coil associating midblock domains to result in dual-associating, network-forming materials. By modifying the standard glycine-containing ELP sequence (XPGVG) to instead contain alanine in the third position of the repeat sequence (XPAVG), it is possible to improve the properties of the material in both shear and extension. In extension at 50 °C, the alanine-containing triblock (A 10 P 4 A 10 ) and the glycine-containing triblock (G 10 P 4 G 10 ) have similar Young’s moduli. However, while G 10 P 4 G 10 yields and breaks within 5 strain units, A 10 P 4 A 10 plastically deforms to an ultimate strain at break of over 15 strain units and a tensile stress of almost 90 kPa. In shear, G 10 P 4 G 10 exhibits a clear stress overshoot at less than one strain unit before plateauing at a steady-state shear stress of 0.43 kPa, while the shear stress of A 10 P 4 A 10 monotonically increases to a shear stress of 48.4 kPa after 2.4 strain units. In shear, these differences in behavior correlate to rearrangement of G 10 P 4 G 10 ’s nanostructure during viscous-dominated flow, while the nanostructure of A 10 P 4 A 10 initially elastically deforms. These differences are a function of the relative network relaxation time scales, where the presence of the faster glycine-containing ELP end-block sequence decreases the network relaxation time such that it occurs on the same order of magnitude as the imposed flow.

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

Can Relaxor Ferroelectric Behavior Be Realized for Poly(vinylidene fluoride- co -chlorotrifluoroethylene) [P(VDF–CTFE)] Random Copolymers by Inclusion of CTFE Units in PVDF Crystals?

Relaxor ferroelectric (RFE) polymers are attractive for various electrical applications such as electrostrictive actuation, electromechanical sensors, electric energy storage, and electrocaloric cooling because of their high dielectric constants and low hysteresis loss. Current state-of-the-art RFE polymers include poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF–TrFE)]-based random copolymers and terpolymers. However, the high costs due to a safety concern of TrFE make their near-term commercialization difficult. It is highly desirable to explore the opportunity of TrFE-free PVDF copolymers [e.g., P(VDF–CTFE); CTFE is chlorotrifluoroethylene] to achieve the RFE behavior by inclusion of CTFE in PVDF crystals (i.e., isomorphism). In this work, two strategies were employed to include CTFE in PVDF crystals. First, high-pressure crystallization was used to obtain extended-chain crystals via the pseudohexagonal paraelectric phase. Structural analyses indicated that CTFE units were largely excluded from the γ unit cells and ferroelectric domains of PVDF but located as kinks inside the extended-chain lamellae. As a result, no RFE behavior was observed because of large ferroelectric γ domains. The second strategy utilized mechanical stretching at low temperatures (–20 to 0 °C) to obtain oriented small β crystallites (ca. 5–7 nm). Structural analyses indicated that CTFE units were excluded from the β unit cells, locating at the crystal–amorphous interfaces. Although the hysteresis loops became somewhat slimmer as a result of small crystallite sizes, the RFE behavior with slim hysteresis loops was still not achieved. Furthermore, this study demonstrated that CTFE units were too large to be included in the tightly packed PVDF unit cells, whether the α, γ, or β phase. In the future, it is desirable to explore other PVDF copolymers with a smaller comonomer such as 1-chloro-1-fluoroethylene.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Elastic Properties and Fracture Behaviors of Biaxially Deformed, Polymorphic MoTe 2

Biaxial deformation of suspended membranes widely exists and is used in nanoindentation to probe elastic properties of structurally isotropic two-dimensional (2D) materials. However, the elastic properties and, in particular, the fracture behaviors of anisotropic 2D materials remain largely unclarified in the case of biaxial deformation. MoTe 2 is a polymorphic 2D material with both isotropic (2H) and anisotropic (1T' and T d ) phases and, therefore, an ideal system of single-stoichiometric materials with which to study these critical issues. Here, we report the elastic properties and fracture behaviors of biaxially deformed, polymorphic MoTe 2 by combining temperature-variant nanoindentation and first-principles calculations. It is found that due to similar atomic bonding, the effective moduli of the three phases deviate by less than 15%. However, the breaking strengths of distorted 1T' and T d phases are only half the value of 2H phase due to their uneven distribution of bonding strengths. Fractures of both isotropic 2H and anisotropic 1T' phases obey the theorem of minimum energy, forming triangular and linear fracture patterns, respectively, along the orientations parallel to Mo–Mo zigzag chains. Furthermore, our findings not only provide a reference database for the elastic behaviors of versatile MoTe 2 phases but also illuminate a general strategy for the mechanical investigation of any isotropic and anisotropic 2D materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Elucidating the Microscale Behavior and Phase Separation Kinetics of Thermally Responsive Ionic Liquid–Water Mixtures

Thermally responsive ionic liquids (ILs) exhibit liquid-liquid phase separation into a water-rich (WR) and ionic-liquid-rich (ILR) phase when heated above a lower critical solution temperature (LCST). This phase behavior has been leveraged for applications ranging from forward osmosis (FO) desalination, where the IL acts as a draw solute, to refrigeration and dehumidification cycles, where the IL acts as a liquid desiccant. While significant effort has been devoted to characterizing the thermodynamic and thermophysical properties of LCST ILs, their phase separation kinetics have not been investigated. In this work, we describe the macroscale phase separation kinetics (phase separation time) by gleaning insight into the microscale colloidal behavior of aqueous mixtures of four different materials, P 4444 TFA (tetrabutylphosphonium-2,4-trifluoroacetate), P 4444 DMBS (tetrabutylphosphonium-2,4-dimethyl-benzenesulfonate), N 4444 Sal (tetrabutylammonium salicylate), and P 4444 Sal (tetrabutylphosphonium salicylate) as a function of IL concentration at a separation temperature of 70 °C. We report the discontinuous microscale size distributions for each material and correlate their theoretical settling velocities to experimental phase separation times. The results indicate that a simple Stokes' law model can predict the phase separation time within reasonable accuracy. Overall, this work lays the foundation for understanding the micro- to macroscale phase separation behavior and kinetics of LCST ILs for various water-energy applications.

LCST↗
DOE OSTI2020

Macroscale and Nanoscale Photoelectrochemical Behavior of p-Type Si(111) Covered by a Single Layer of Graphene or Hexagonal Boron Nitride

Two-dimensional (2D) materials may enable a general approach to the introduction of a dipole at a semiconductor surface as well as control over other properties of the double layer at a semiconductor/liquid interface. Vastly different properties can be found in the 2D materials currently studied due in part to the range of the distribution of density-of-states. In this work, the open-circuit voltage (V oc ) of p-Si–H, p-Si/Gr (graphene), and p-Si/h-BN (hexagonal boron nitride) in contact with a series of one-electron outer-sphere redox couples was investigated by macroscale measurements as well as by scanning electrochemical cell microscopy (SECCM). The band gaps of Gr and h-BN (0–5.97 eV) encompass the wide range of band gaps for 2D materials, so these interfaces (p-Si/Gr and p-Si/h-BN) serve as useful references to understand the behavior of 2D materials more generally. The value of Voc shifted with respect to the effective potential of the contacting solution, with slopes (ΔV oc /ΔE Eff ) of -0.27 and -0.38 for p-Si/Gr and p-Si/h-BN, respectively, indicating that band bending at the p-Si/h-BN and p-Si/Gr interfaces responds at least partially to changes in the electrochemical potential of the contacting liquid electrolyte. Additionally, SECCM is shown to be an effective method to interrogate the nanoscale photoelectrochemical behavior of an interface, showing little spatial variance over scales exceeding the grain size of the CVD-grown 2D materials in this work. The measurements demonstrated that the polycrystalline nature of the 2D materials had little effect on the results and confirmed that the macroscale measurements reflected the junction behavior at the nanoscale.

2D material↗
DOE OSTI2021

Directly Probing the Fracture Behavior of Ultrathin Polymeric Films

Understanding fracture mechanics of ultrathin polymeric films is crucial for modern technologies, including semiconductor and coating industries. However, up to now, the fracture behavior of sub-100 nm polymeric thin films is rarely explored due to challenges in handling samples and limited testing methods available. In this work, we report a new testing methodology that can not only visualize the evolution of the local stress distribution through wrinkling patterns and crack propagation during the deformation of ultrathin films but also directly measure their fracture energies. Using ultrathin polystyrene films as a model system, we both experimentally and computationally investigate the effect of the film thickness and molecular weight on their fracture behavior, both of which show a ductile-to-brittle transition. Furthermore, we demonstrate the broad applicability of this testing method in semicrystalline semiconducting polymers. We anticipate our methodology described here could provide new ways of studying the fracture behavior of ultrathin films under confinement.

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

Cellulose Nanocrystals’ Role in Critical Mineral Beneficiation: Dual Aggregate-Dispersant Behavior Supports Environmentally Benign Nickel Processing

Environmentally unsustainable and toxic chemical flocculants and dispersants from nickel (Ni) processing contribute to industrial effluents that greatly impact biodiversity and aquatic life. Despite the industry’s efforts to reduce its ecological footprint—primarily due to the lack of commercially available biodegradable, environmentally benign, and non-toxic reagents—these reagents continue to harm natural ecosystems. Chemicals used during the processing operations often target a specific unit operation that negatively affects downstream operations. In this study, we discover the concentration-dependent behavior of cellulose nanocrystals (CNCs) as a dispersant and flocculant, avoiding the use of various harmful chemicals in the nickel processing stages. Electrophoretic, optical brightfield microscopy, and quartz crystal microbalance-dissipation studies detected charge neutralization behavior by renewable and biodegradable CNCs, which can greatly benefit Ni processing operations. Microflotation experiments demonstrated that CNCs enhanced Ni recovery from 62 to 77 wt.% and concentrate grade from 15 to 20 wt.%. Settling and turbidity studies demonstrated the dual flocculant-dispersant behavior of CNCs resulting from the alignment of CNC fibers along the octahedral brucite basal and amphoteric edge plane of serpentine. CNCs can be used as dispersants during froth flotation to improve Ni beneficiation and as post-processing flocculants for tailings management and dewatering, which is one of the major environmental and social concerns facing the mining and mineral processing industry. This study paves the way for CNCs to be used as flocculants and dispersants in a range of industries from healthcare to pharmaceuticals to semiconductor devices.

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

Cluster-Spin-Glass Magnetic Behavior and Morphology in the Coordination Polymer Alloys Fe y Co 1– y BTT

We report the synthesis of a series of pseudo-1D coordination polymer (CP) materials with the formula Fe y Co 1–y BTT (BTT = 1,3,5-benzenetrithiolate). These materials were structurally characterized by PXRD Rietveld, EXAFS, and PDF analyses, revealing that the CP superstructure enables a continuous and isomorphous alloy between the two homometallic compounds. Lower Fe loadings exhibit emergent spin glass magnetic behavior, such as memory effects and composition-dependent spin glass response time constants ranging from 6.9 × 10 –9 s to 1.8 × 10 –6 s. These data are consistent with the formation of spin clusters within the lattice. The magnetic behavior in these materials was modeled via replica exchange Monte Carlo simulation, which provides a good match for the experimentally measured spin glassing and magnetic phase transitions. Furthermore, these findings underscore how the rigid superstructure of CP and MOF scaffolds can enable the systematic tuning of physical properties, such as the spin glass behavior described here.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Magnetic ordering-induced multiferroic behavior in [CH 3 NH 3 ][Co(HCOO) 3 ] metal-organic framework.

Here, we present the first example of magnetic ordering-induced multiferroic behavior in a metal–organic framework magnet. This compound is [CH 3 NH 3 ][Co(HCOO) 3 ] with a perovskite-like structure. The A-site [CH 3 NH 3 ] + cation strongly distorts the framework, allowing anisotropic magnetic and electric behavior and coupling between them to occur. This material is a spin canted antiferromagnet below 15.9 K with a weak ferromagnetic component attributable to Dzyaloshinskii–Moriya (DM) interactions and experiences a discontinuous hysteretic magnetic-field-induced switching along [010] and a more continuous hysteresis along [101]. Coupling between the magnetic and electric order is resolved when the field is applied along this [101]: a spin rearrangement occurs at a critical magnetic field in the ac plane that induces a change in the electric polarization along [101] and [10-1]. The electric polarization exhibits an unusual memory effect, as it remembers the direction of the previous two magnetic-field pulses applied. The data are consistent with an inverse-DM mechanism for multiferroic behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2018

High‐Pressure/Temperature Behavior of the Alkali/Calcium Carbonate Shortite (Na 2 Ca 2 (CO 3 ) 3 ): Implications for Carbon Sequestration in Earth's Transition Zone

Abstract The behavior of shortite (Na 2 Ca 2 (CO 3 ) 3 ) has been probed using synchrotron‐based single crystal X‐ray diffraction and Raman spectroscopy at high pressures and following laser heating to illuminate carbon retention within the deep earth, and phase equilibria of alkali/calcium carbonate‐rich systems. Above 15 GPa, a transition to the shortite‐II structure occurs at 300 K. This phase is novel as it involves a large distortion of the carbonates, with an onset of 3 + 1 coordination and near‐dimerization of carbonate groups. Above 22 GPa, shortite‐II amorphizes. Samples laser heated at pressures between 12 and 30 GPa crystallize in a new structure, shortite‐III. Below 12 GPa, this phase appears to decompose into a mixture of shortite, nyerereite (Na 2 Ca(CO 3 ) 2 ), and aragonite (CaCO 3 ) in accord with prior phase equilibria results. The high‐pressure behavior of nyerereite using Raman spectroscopy was also investigated to 25 GPa. The structural response of shortite to pressure is modulated by the sodium cations in the structure; hence, the behavior of alkali‐rich carbonates within kimberlitic systems at depth is likely dependent on the bonding and local geometry of alkali cations. Our results show that complex, dense high‐pressure structures are generated in the shortite system, and phase equilibria of the protoliths of carbonatites and kimberlites at deep upper mantle and transition zone pressures will involve intermediate alkali‐calcium carbonate phases, including the high‐pressure phases of shortite. Moreover, 3 + 1 coordination of carbon is observed at far lower pressures than other systems: this coordination could become important in complex carbonates and possibly liquids at substantially shallower depths than previously anticipated.

Vennari, Cara E.↗
DOE OSTI2020

Physical and behavioral adaptations to prevent overheating of the living wings of butterflies

The wings of Lepidoptera contain a matrix of living cells whose function requires appropriate temperatures. However, given their small thermal capacity, wings can overheat rapidly in the sun. Here we analyze butterfly wings across a wide range of simulated environmental conditions, and find that regions containing living cells are maintained at cooler temperatures. Diverse scale nanostructures and non-uniform cuticle thicknesses create a heterogeneous distribution of radiative cooling that selectively reduces the temperature of structures such as wing veins and androconial organs. These tissues are supplied by circulatory, neural and tracheal systems throughout the adult lifetime, indicating that the insect wing is a dynamic, living structure. Behavioral assays show that butterflies use wings to sense visible and infrared radiation, responding with specialized behaviors to prevent overheating of their wings. Our work highlights the physiological importance of wing temperature and how it is exquisitely regulated by structural and behavioral adaptations.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Quantum critical behavior in the asymptotic limit of high disorder in the medium entropy alloy NiCoCr 0.8

The behavior of matter near a quantum critical point is one of the most exciting and challenging areas of physics research. Emergent phenomena such as high-temperature superconductivity are linked to the proximity to a quantum critical point. Although significant progress has been made in understanding quantum critical behavior in some low dimensional magnetic insulators, the situation in metallic systems is much less clear. Here, we demonstrate that NiCoCr x single crystal alloys are remarkable model systems for investigating quantum critical point physics in a metallic environment. For NiCoCr x alloys with x ≈ 0.8, the critical exponents associated with a ferromagnetic quantum critical point are experimentally determined from low temperature magnetization and heat capacity measurements. All of the five exponents (γ T ≈ 1/2, β T ≈ 1, δ ≈ 3/2, νz m ≈ 2, α¯ T ≈ 0) are in remarkable agreement with predictions of Belitz–Kirkpatrick–Vojta theory in the asymptotic limit of high disorder. Using these critical exponents, excellent scaling of the magnetization data is demonstrated with no adjustable parameters. We also find a divergence of the magnetic Gruneisen parameter, consistent with a ferromagnetic quantum critical point. This work furthermore demonstrates that entropy stabilized concentrated solid solutions represent a unique platform to study quantum critical behavior in a highly tunable class of materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

A Global Building Occupant Behavior Database

This paper introduces a database of 34 field-measured building occupant behavior datasets collected from 15 countries and 39 institutions across 10 climatic zones covering various building types in both commercial and residential sectors. This is a comprehensive global database about building occupant behavior. The database includes occupancy patterns (i.e., presence and people count) and occupant behaviors (i.e., interactions with devices, equipment, and technical systems in buildings). Brick schema models were developed to represent sensor and room metadata information. The database is publicly available, and a website was created for the public to access, query, and download specific datasets or the whole database interactively. The database can help to advance the knowledge and understanding of realistic occupancy patterns and human-building interactions with building systems (e.g., light switching, set-point changes on thermostats, fans on/off, etc.) and envelopes (e.g., window opening/closing). With these more realistic inputs of occupants’ schedules and their interactions with buildings and systems, building designers, energy modelers, and consultants can improve the accuracy of building energy simulation and building load forecasting.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Tensile deformation behavior of twist grain boundaries in CoCrFeMnNi high entropy alloy bicrystals

High entropy alloys (HEA) are a class of materials that consist of multiple elemental species in similar concentrations. The use of elements in far from dilute concentrations introduces a multi-dimensional composition design space by which the properties of metallic systems can be tailored. While the mechanical behavior of HEAs has been the subject of active research recently, the role of grain boundaries (GBs) in their deformation behavior remains poorly understood. Motivated by recent experiments on HEAs demonstrating that GBs act as nucleation sites for deformation twins, herein, we leverage atomistic simulations to construct a series of equiatomic CoCrFeMnNi HEA bicrystals with $\langle 110 \rangle$ and $\langle 111 \rangle$ symmetric twist GBs and examine their tensile behavior and underlying deformation mechanisms at 77 K. Simulation results reveal that plastic deformation proceeds by the nucleation of partial dislocations from GBs, which then grow with further loading by bowing into the bulk crystals leaving behind stacking faults. Variations in the nucleation stress exist as function of GB character, defined in this work by the twist angle. Our results provide future avenues to explore GBs as a microstructure design tool to develop HEAs with tailored properties.

36 MATERIALS SCIENCE↗
DOE OSTI2025

A temperature-induced hysteretic behavior of resistivity and magnetoresistance of electrodeposited bismuth microbridges for X-ray transition-edge sensor absorbers

This study investigates the temperature-induced hysteretic behavior of resistivity and magnetoresistance in electrodeposited bismuth films, with a focus on their application as absorbers in transition-edge sensors (TESs) for X-ray detection. Through a series of resistivity versus temperature measurements from room temperature to a few Kelvin, we explore the change in the conductive behavior of bismuth electrodeposited on various substrates. Our findings show for the first time both hysteretic and irreversible changes in resistivity as a function of temperature. Further, magnetoresistance measurements reveal notable variations in resistance behavior under different magnetic fields, highlighting the impact of magnetic fields on these films’ electronic transport properties, with an indication of potential weak anti-localization effects at the lowest temperatures. This study not only provides a deeper understanding of bismuth’s conductivity characteristics at low temperatures but also sheds light on the practical implications for developing more effective TESs for synchrotron X-ray facilities.

42 ENGINEERING↗
DOE OSTI2025

Rooftop solar and energy storage programs can remediate energy-limiting behaviors of energy insecure households in the United States

Energy insecurity, or the inability to afford energy needs, affects most low-income households in the United States and leads to risky choices and additional insecurities including food and health. Although there are government programs designed to provide relief from energy insecurity, eligibility is usually determined by household income, and those with incomes close to the threshold face uncertainty or may be left out. In many cases, these households turn to energy-limiting behaviors as a strategy to lower their electric utility bills. Here we explore the relationship between energy insecurity and energy-limiting behaviors and investigate alternative solutions such as energy storage and rooftop solar. This analysis demonstrates that solar and energy storage can offset two-thirds of the bill savings that households could attain through severe energy-limiting behavior. These systems could complement existing energy assistance programs to provide long-term bill relief, enabling occupants to live in their homes with comfort and dignity.

Kerby, Jessica R. [Pacific Northwest National Labo↗