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At least 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Oleophilic foams for oil spill mitigation

A method of fabricating an oleophilic foam includes providing a foam comprising a base material. The base material is coated with an inorganic material using at least one of an atomic layer deposition (ALD), a molecular layer deposition (MLD) or sequential infiltration synthesis (SIS) process. The SIS process includes at least one cycle of exposing the foam to a first metal precursor for a first predetermined time and a first partial pressure. The first metal precursor infiltrates at least a portion of the base material and binds with the base material. The foam is exposed to a second co-reactant precursor for a second predetermined time and a second partial pressure. The second co-reactant precursor reacts with the first metal precursor, thereby forming the inorganic material on the base material. The inorganic material infiltrating at least the portion of the base material. The inorganic material is functionalized with an oleophilic material.

04 OIL SHALES AND TAR SANDS↗
DOE OSTI2021

Oleophilic foams for oil spill mitigation

A method of fabricating an oleophilic foam includes providing a foam comprising a base material. The base material is coated with an inorganic material using at least one of an atomic layer deposition (ALD), a molecular layer deposition (MLD) or sequential infiltration synthesis (SIS) process. The SIS process includes at least one cycle of exposing the foam to a first metal precursor for a first predetermined time and a first partial pressure. The first metal precursor infiltrates at least a portion of the base material and binds with the base material. The foam is exposed to a second co-reactant precursor for a second predetermined time and a second partial pressure. The second co-reactant precursor reacts with the first metal precursor, thereby forming the inorganic material on the base material. The inorganic material infiltrating at least the portion of the base material. The inorganic material is functionalized with an oleophilic material.

Darling, Seth B.↗
DOE OSTI2023

Performance analysis of functionally graded multifunctional piezoelectric energy harvesting microgyroscopes

Functionally graded materials (FGMs) are composite materials with varying material properties in one or more directions. These materials possess distinct characteristics compared to their constituent components. The ability to control material distribution and compositions in FGMs offers improved constraints over the natural frequencies of the system, making them highly suitable for energy harvesting applications. In this study, we focus on a piezoelectric FGM composed of Platinum (Pt) and Lead Titanate Zirconate (PZT). By utilizing FGMs for energy harvesting, we simplify the system from a multilayer structure to a single-layer system, thereby increasing power density by reducing volume. In this work, a power law distribution is used to model the material variation throughout the thickness of the single-layered beam. The governing equations of motion and boundary conditions for FG energy harvesting microgyroscope are derived using Euler-Bernoulli beam theory, the constitutive piezoelectric principle, and the extended Hamilton's principle. To simulate the nonlinear motion of the FG energy harvester, we employ the differential quadrature method (DQM). Subsequently, an investigation is carried out to examine the effects of various factors including material distribution, platinum percentage, base rotation, DC voltage, and electrical load resistance on the energy harvesting microgyroscope with functionally graded materials. Here, the findings suggest that functionally graded energy harvesting gyroscopes can be adjusted to obtain effective energy harvesting and sensing capabilities by carefully selecting the material distribution, input voltage, and electrical load resistance.

42 ENGINEERING↗
DOE OSTI2016

Bioinspired synthesis and self-assembly of hybrid organic–inorganic nanomaterials

Nature is replete with complex organic–inorganic hierarchical materials of diverse yet specific functions. These materials are intricately designed under physiological conditions through biomineralization and biological self-assembly processes. Tremendous efforts have been devoted to investigating mechanisms of such biomineralization and biological self-assembly processes as well as gaining inspiration to develop biomimetic methods for synthesis and self-assembly of functional nanomaterials. In this work, we focus on the bioinspired synthesis and self-assembly of functional inorganic nanomaterials templated by specialized macromolecules including proteins, DNA and polymers. The in vitro biomineralization process of the magnetite biomineralizing protein Mms6 has been investigated using small-angle X-ray scattering. Templated by Mms6, complex magnetic nanomaterials can be synthesized on surfaces and in the bulk. DNA and synthetic polymers have been exploited to construct macroscopic two- and three-dimensional (2D and 3D) superlattices of gold nanocrystals. Employing X-ray scattering and spectroscopy techniques, the self-assembled structures and the self-assembly mechanisms have been studied, and theoretical models have been developed. Our results show that specialized macromolecules including proteins, DNA and polymers act as effective templates for synthesis and self-assembly of nanomaterials. These bottom-up approaches provide promising routes to fabricate hybrid organic–inorganic nanomaterials with rationally designed hierarchical structures, targeting specific functions.

36 MATERIALS SCIENCE↗
NASA NTRS2002

Higher-Order Theory: Structural/MicroAnalysis Code (HOTSMAC) Developed

The full utilization of advanced materials (be they composite or functionally graded materials) in lightweight aerospace components requires the availability of accurate analysis, design, and life-prediction tools that enable the assessment of component and material performance and reliability. Recently, a new commercially available software product called HOTSMAC (Higher-Order Theory--Structural/MicroAnalysis Code) was jointly developed by Collier Research Corporation, Engineered Materials Concepts LLC, and the NASA Glenn Research Center under funding provided by Glenn's Commercial Technology Office. The analytical framework for HOTSMAC is based on almost a decade of research into the coupled micromacrostructural analysis of heterogeneous materials. Consequently, HOTSMAC offers a comprehensive approach for analyzing/designing the response of components with various microstructural details, including certain advantages not always available in standard displacement-based finite element analysis techniques. The capabilities of HOTSMAC include combined thermal and mechanical analysis, time-independent and time-dependent material behavior, and internal boundary cells (e.g., those that can be used to represent internal cooling passages, see the preceding figure) to name a few. In HOTSMAC problems, materials can be randomly distributed and/or functionally graded (as shown in the figure, wherein the inclusions are distributed linearly), or broken down by strata, such as in the case of thermal barrier coatings or composite laminates.

Arnold, Steven M.↗
NASA NTRS2013

Covalent Crosslinking of Carbon Nanotube Materials for Improved Tensile Strength

Carbon nanotubes have attracted much interest in recent years due to their exceptional mechanical properties. Currently, the tensile properties of bulk carbon nanotube-based materials (yarns, sheets, etc.) fall far short of those of the individual nanotube elements. The premature failure in these materials under tensile load has been attributed to inter-tube sliding, which requires far less force than that needed to fracture individual nanotubes.1,2 In order for nanotube materials to achieve their full potential, methods are needed to restrict this tube-tube shear and increase inter-tube forces.Our group is examining covalent crosslinking between the nanotubes as a means to increase the tensile properties of carbon nanotube materials. We are working with multi-walled carbon nanotube (MWCNT) sheet and yarn materials obtained from commercial sources. Several routes to functionalize the nanotubes have been examined including nitrene, aryl diazonium, and epoxide chemistries. The functional nanotubes were crosslinked through small molecule or polymeric bridges. Additionally, electron beam irradiation induced crosslinking of the non-functional and functional nanotube materials was conducted. For example, a nanotube sheet material containing approximately 3.5 mol amine functional groups exhibited a tensile strength of 75 MPa and a tensile modulus of 1.16 GPa, compared to 49 MPa and 0.57 GPa, respectively, for the as-received material. Electron beam irradiation (2.2x 1017 ecm2) of the same amine-functional sheet material further increased the tensile strength to 120 MPa and the modulus to 2.61 GPa. This represents approximately a 150 increase in tensile strength and a 360 increase in tensile modulus over the as-received material with only a 25 increase in material mass. Once we have optimized the nanotube crosslinking methods, the performance of these materials in polymer matrix composites will be evaluated.

polymer matrix composites↗
NASA NTRS2002

Efficient Reformulation of the Thermoelastic Higher-order Theory for Fgms

Functionally graded materials (FGMs) are characterized by spatially variable microstructures which are introduced to satisfy given performance requirements. The microstructural gradation gives rise to continuously or discretely changing material properties which complicate FGM analysis. Various techniques have been developed during the past several decades for analyzing traditional composites and many of these have been adapted for the analysis of FGMs. Most of the available techniques use the so-called uncoupled approach in order to analyze graded structures. These techniques ignore the effect of microstructural gradation by employing specific spatial material property variations that are either assumed or obtained by local homogenization. The higher-order theory for functionally graded materials (HOTFGM) is a coupled approach developed by Aboudi et al. (1999) which takes the effect of microstructural gradation into consideration and does not ignore the local-global interaction of the spatially variable inclusion phase(s). Despite its demonstrated utility, however, the original formulation of the higher-order theory is computationally intensive. Herein, an efficient reformulation of the original higher-order theory for two-dimensional elastic problems is developed and validated. The use of the local-global conductivity and local-global stiffness matrix approach is made in order to reduce the number of equations involved. In this approach, surface-averaged quantities are the primary variables which replace volume-averaged quantities employed in the original formulation. The reformulation decreases the size of the global conductivity and stiffness matrices by approximately sixty percent. Various thermal, mechanical, and combined thermomechanical problems are analyzed in order to validate the accuracy of the reformulated theory through comparison with analytical and finite-element solutions. The presented results illustrate the efficiency of the reformulation and its advantages in analyzing functionally graded materials.

Bansal, Yogesh↗
DOE OSTI2013

Dependence of the mechanical behavior of alloys on their electron work function—An alternative parameter for materials design

In this article, we demonstrate that the electron work function (EWF) as an intrinsic parameter can provide information or clues in a simple or straightforward way for material design, modification, and development. A higher work function of a material represents a more stable electronic state, which consequently generates a higher resistance to any attempt of changing the electronic state and other corresponding states, e.g., changes in structure or microstructure caused by mechanical and electrochemical actions. Using Cu-Ni alloy as an example, we demonstrate the correlation between the EWF and Young's modulus of the material as well as its hardness. The properties of a material can be modified using elements with appropriate work functions. This is also applicable for tailoring inter-phase boundaries or interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Verification Testing For Solid-Element Material Models 11-19 in DYNA3D/ParaDyn

This technical report documents the creation and implementation of verification tests for solid-element material models 11 through 19 available in DYNA3D/ParaDyn. The verification tests covered all aspects of each material model, except for the Weibull distribution functionality in material models 15 and 19. General test cases were created to verify the elastic and plastic behavior of the material models. Other additional tests were developed to examine the intricacies of each material model. Each test involved the use a kinematic load case and specification of material parameters necessary to activate corresponding features of the material model. The load cases prescribed the full time history of the kinematic motion for the solid elements, and these loads are independent of the material model or element formulation. When possible, closed form solutions were then derived for each verification test in a continuum setting. The DYNA3D simulations for each test were carried out over a unit time interval, t ϵ [0, 1], and the as implemented DYNA3D response was compared to the closed form solutions evaluated at discrete points in time. A relative error measure was determined for each test to justify the proper implementation of the material model. The relative errors comparing the DYNA3D solution to the analytical solution were, in general, on the order of machine precision except where noted. This signifies the proper implementation of solid-element material models 11-19. In the development of these verification tests, six bugs were found and fixed in the source code. Additionally, this work generated eighteen DYNA3D input decks and answer extraction scripts in the DYNA3D/ParaDyn Software Quality Assurance test suite, which are comprised of a total of 285 solid-element tests. Testing for each material model utilizes two input decks and answer extraction scripts, where one focuses on the linear elastic response and the other examines the inelastic and remaining functionalities of the material model. In total, this work added 285 individual verification test problems in the DYNA3D/ParaDyn test suite.

42 ENGINEERING↗
DOE OSTI2023

The nature and suppression strategies of interfacial reactions in all-solid-state batteries

Solid-state Li batteries are promising energy storage devices owing to their high safety and high theoretical energy density. However, the serious interfacial reaction between solid state electrolytes and cathodes deteriorates the battery performance, impeding the realization of long-term cyclability. The buried nature of the interphase layer presents a significant challenge in achieving a comprehensive understanding of the underlying interfacial reaction mechanisms. Herein, we systematically explore the interfacial reaction evolutions and interphase compositions and electronic properties between the popular oxide cathodes and sulfide solid electrolytes (SSEs). This includes analysis of the chemical and electrochemical reactions between cathodes/coatings and SSEs, as well as the electrochemical self-decomposition of SSEs by thermodynamic phase equilibrium analysis. Herein, we disclose that the driving force of the electrochemical reaction at the chemical potential of μ Li is much stronger than that of the chemical reaction, which dominates the interfacial reaction. Preventing the formation of an electronically conductive interphase is crucial in inhibiting the continuous interfacial degradation during long-term cycling, which can be achieved through the optimized combination of cathodes and SSEs, as well as the introduction of functional coatings between them. Based on these findings, the percentage of molar fraction ( f ) of electronically conductive species in the formed interphase is proposed as a key factor for indicating the interfacial stability for the first time. Furthermore, we propose a specific high-throughput screening scheme to filter the functional coating materials by comprehensively evaluating their functionality. The tiered screening identifies 48 coating materials with optimal properties. The work highlights the significant roles of rational coupling of the cathodes and SSEs, and optimizing interfacial coating materials for solid-state batteries. It opens new avenues for engineering an interphase with improved interfacial compatibility to realize long-term cyclability.

25 ENERGY STORAGE↗
DOE OSTI2021

Systematic Evaluation of Carbon Hosts for High-Energy Rechargeable Lithium-Metal Batteries

Rechargeable lithium batteries (RLBs) have attracted wide attention for achieving high energy and low cost, but the poor stability of the Li anode has remained as a large challenge. In the last several years, great efforts have been made to develop carbon anode structures for RLB applications. A wide range of carbon structures as well as many chemical modification strategies have been investigated to improve the Coulombic efficiency and extend the cycle life of the anodes or the cells. However, currently there is no clear conclusion on key factors that determine the performance of such the types of carbon structures due to the wide range of experimental conditions used in such studies. In this study, we systematically evaluated and compared the electrochemical properties of representative carbon anode materials as well as chemically functionalized carbon materials in different electrolytes. We have found that chemical functionalization, metallic loading, and the types of micro or nano-structures all have an effect on Li deposition/stripping process, but by far the most critical factor is the nature of the electrolytes. All carbon materials produced poor Coulombic efficiency and cycle life in conventional carbonate or ether-based electrolytes. However, when a Li metal compatible is used, the average Coulombic efficiency of Li metal deposition on all carbon structures is increased to 99% or higher. This study provides critical lessons on the directions for carbon anodes for RLBs. Based on these findings, we constructed Li metal coin cells using prelithiated hard carbon, LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode, and compatible electrolyte and tested the cells under conditions of lean electrolyte, lean Li metal and high cathode loading required for more than 300 Wh kg-1 specific energy. More than 200 stable cycles were demonstrated with over 80% capacity retention. Furthermore, the existing challenges and potential approaches have been discussed to further extend the cyclability of lithium-metal batteries under practical conditions.

Liu, Yao↗
DOE OSTI2025

Reversible Modification of Rashba States in Topological Insulators at Room Temperature by Edge Functionalization

Quantum materials with novel spin textures from strong spin-orbit coupling (SOC) are essential components for a wide array of proposed spintronic devices. Topological insulators have a necessary strong SOC that imposes a unique spin texture on topological states and Rashba states that arise on the boundary, but there is no established methodology to control the spin texture reversibly. Here, it is demonstrated that functionalizing Bi 2 Se 3 films by altering the step-edge termination directly changes the strength of SOC and thereby modifies the Rashba strength of 1D edge states. Scanning tunneling microscopy/spectroscopy shows that these Rashba edge states arise and subsequently vanish through the Se functionalization and reduction process of the step edges. The observations are corroborated by density functional theory calculations, which show that a subtle chemical change of edge termination fundamentally alters the underlying electronic structure. Importantly, fully reversible and repeatable switching of Rashba edge states across multiple cycles at room temperature is experimentally demonstrated. The results imply Se functionalization as a practical method to control SOC and spin texture of quantum states in topological insulators.

Rashba edge states↗
DOE OSTI2015

Charge Recombination, Transport Dynamics, and Interfacial Effects in Organic Solar Cells

The need for renewable sources of energy is well known. Conversion of sunlight to electricity using solar cells is one of the most important opportunities for creating renewable energy sources. The research carried out under DE-FG02-08ER46535 focused on the science and technology of “Plastic” solar cells comprised of organic (i.e. carbon based) semiconductors. The Bulk Heterojunction concept involves a phase separated blend of two organic semiconductors each with dimensions in the nano-meter length scale --- one a material that functions as a donor for electrons and the other a material that functions as an acceptor for electrons. The nano-scale inter-penetrating network concept for “Plastic” solar cells was created at UC Santa Barbara. A simple measure of the impact of this concept can be obtained from a Google search which gives 244,000 “hits” for the Bulk Heterojunction solar cell. Research funded through this program focused on four major areas: 1. Interfacial effects in organic photovoltaics, 2. Charge transfer and photogeneration of mobile charge carriers in organic photovoltaics, 3. Transport and recombination of the photogenerated charge carriers in organic photovoltaics, 4. Synthesis of novel organic semiconducting polymers and semiconducting small molecules, including conjugated polyelectrolytes. Following the discovery of ultrafast charge transfer at UC Santa Barbara in 1992, the nano-organic (Bulk Heterojunction) concept was formulated. The need for a morphology comprising two interpenetrating bicontinuous networks was clear: one network to carry the photogenerated electrons (negative charge) to the cathode and one network to carry the photo-generated holes (positive charge) to the anode. This remarkable self-assembled network morphology has now been established using Transmission electron Microscopy (TEM) either in the Phase Contrast mode or via TEM-Tomography. The steps involved in delivering power from a solar cell to an external circuit are the following: • Photo-excitation of the donor (or the acceptor). • Charge transfer with holes in the donor domain and electrons in the acceptor domain. • Sweep-out to electrodes prior to recombination by the internal electric field. • Energy delivered to the external circuit. Each of these four steps was studied in detail using a wide variety of organic semiconductors with different molecular structures. This UC Santa Barbara group was the first to clarify the origin and the mechanism involved in the ultrafast charge transfer process. The ultrafast charge transfer (time scale approximately 100 times faster than the first step in the photo-synthesis of green plants) is the fundamental reason for the potential for high power conversion efficiency of sunlight to electricity from plastic solar cells. The UCSB group was the first to emphasize, clarify and demonstrate the need for sweep-out to electrodes prior to recombination by the internal electric field. The UCSB group was the first to synthesize small molecule organic semiconductors capable of high power conversion efficiencies. The results of this research were published in high impact peer-reviewed journals. Our published papers (40 in number) provide answers to fundamental questions that have been heavily discussed and debated in the field of Bulk Heterojunction Solar Cells; scientific questions that must be resolved before this technology can be ready for commercialization in large scale for production of renewable energy. Of the forty publications listed, nineteen were co-authored by two or more of the PIs, consistent with the multi-investigator approach described in the original proposal. The specific advantages of this “plastic” solar cell technology are the following: a. Manufacturing by low-cost printing technology using soluble organic semiconductors; this approach can be implemented in large scale by roll-to-roll printing on plastic substrates. b. Low energy cost in manufacturing; all steps carried out at room temperature (approx. a factor of ten less than the use of Silicon which requires high temperature processing). c. Low carbon footprint d. Lightweight, flexible and rugged Because of the resolution of many scientific issues, a significant fraction of which were addressed in the research results of DE-FG02-08ER46535, the power conversion efficiencies are improving at an ever increasing rate. During the funding period of DE-FG02-08ER46535, the power conversion efficiencies of plastic solar cells improved from just a few per cent to values greater than 11% with contributions from our group and from researchers all over the world.

14 SOLAR ENERGY↗