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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Block Krylov Subspace Methods for Functions of Matrices II: Modified Block FOM

We analyze an expansion of the generalized block Krylov subspace framework of [Electron. Trans. Numer. Anal., 47 (2017), pp. 100--126]. This expansion allows the use of low-rank modifications of the matrix projected onto the block Krylov subspace and contains, as special cases, the block GMRES method and the new block Radau--Arnoldi method. Within this general setting, we present results that extend the interpolation property from the nonblock case to a matrix polynomial interpolation property for the block case, and we relate the eigenvalues of the projected matrix to the latent roots of these matrix polynomials. Some error bounds for these modified block FOM methods for solving linear systems are presented. We then show how cospatial residuals can be preserved in the case of families of shifted linear block systems. This result is used to derive computationally practical restarted algorithms for block Krylov approximations that compute the action of a matrix function on a set of several vectors simultaneously. Finally, we prove some error bounds and present numerical results showing that two modifications of FOM, the block harmonic and the block Radau--Arnoldi methods for matrix functions, can significantly improve the convergence behavior.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Proton Conducting Sulfonated Poly(Ionic Liquid) Block Copolymers

Herein, we report the synthesis of proton-conducting sulfonated poly(ionic liquid) block copolymers (S-PILBCPs) containing one block with sulfonic acid (sulfonated styrene, SS) and the other with an IL moiety (vinylbenzylmethylimidazolium bis(trifluoromethylsulfonyl)imide, VBMIm-TFSI) using reversible addition–fragmentation chain-transfer (RAFT) polymerization and post-polymerization modifications (i.e., functionalization, anion exchange reactions, and sulfonation). The S-PILBCPs uniquely conjoin the SS block with mobile protons (H + ) and the PIL block with mobile anions (TFSI – ), where multiple highly desired properties, including high proton conductivity (from the SS block), and high IL-philicity and oxygen solubility (from the PIL block) can exist compartmentally within a microphase separated morphology (evidenced by differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS)). High ion conductivity of 79.7 mS/cm at a PIL block composition of 21.6 mol % was observed at 80 °C and 90% relative humidity (RH) (comparable to the benchmark Nafion ionomer). This work successfully demonstrates the design of S-PILBCPs as a new material platform and showcases its promise as an ionomer for proton exchange membrane fuel cells (PEMFCs) as they simultaneously and compartmentally combine proton conductivity and oxygen solubility. Furthermore, these benefits have recently been leveraged to achieve substantial improvement in oxygen reduction reaction (ORR) activity and subsequently fuel cell performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Synthesis and Characterization of Methacrylamide-Based Block Random Copolymers via Amine Functionalization of Polystyrene- Block -Poly(Pentafluorophenyl Methacrylate) Toward Enhanced Amenability to Manufacturing Criteria in Nanolithography

Recent interest in manipulating the chemistry of block copolymers (BCPs) to manage the covarying properties necessary to meet manufacturing criteria in nanolithography has resulted in the development and expansion of the A-block-(B-random-C) BCP architecture, where the random block allows for the decoupling of thermodynamic and wetting properties. Previous reports of such BCPs have used click chemistry to create the desired random block, but all such instances possess additional functional groups that are susceptible to undesirable side reactions upon annealing, such as cross-linking and surface grafting. This study reports the substitution reaction of polystyrene-block-poly(pentafluorophenyl methacrylate) (PS-b-PPFMA) with primary amines. The resulting methacrylamide structure of the functionalized random block has only an amide linkage between the attached functional group and the polymer backbone, thereby omitting any sources of side reactions within the BCP. The outcomes of this report also demonstrate the enhanced thermal stability of these materials by virtue of their stable amide bonds. A range of random copolymer compositions is assessed to develop BCPs in which the random block has approximately the same surface energy as the PS block. These BCPs can self-assemble into perpendicular lamellae and are therefore promising candidates for directed self-assembly.

block copolymers↗
DOE OSTI2023

Wetting Behavior of A -block- (B- random -C) Copolymers with Equal Block Surface Energies on Surfaces Functionalized with B- random -C Copolymers

To form nanopatterns with self-assembled block copolymers (BCPs), it is desirable to have through-film domains that are oriented perpendicular to the substrate. The domain orientation is determined by the interfacial interactions of the BCP domains with the substrate and with the free surface. Here, we use thin films of two different sets of BCPs with A-block-(B-random-C) architecture matched with a corresponding B-random-C copolymer nanocoating on the substrate to demonstrate two distinct wetting behaviors. The two sets of A-b-(B-r-C) BCPs are made by using thiol–epoxy click chemistry to functionalize polystyrene-block-poly(glycidyl methacrylate) with trifluoroethanethiol (TFET) and either 2-mercaptopyridine (2MP) or methyl thioglycolate (MTG). For each set of BCPs, the composition ratio of the two thiols in the BCP (φ 1 ) is found that results in the two blocks of the modified BCP having equal surface energies (Δγ air = 0). The corresponding B-r-C random copolymers were synthesized and used to modify the substrate, and the composition ratio (φ 2 ) values that resulted in the two blocks of the BCP having equal interfacial energy with the substrate (Δγ sub = 0) were determined with scanning electron microscopy. The correlation between each block’s γ sub value and the interaction parameter, χ, is employed to explain the different wetting behaviors of the two sets of BCPs. For the thiol pair 2MP and TFET, the values of φ 1 and φ 2 that lead to Δγ air = 0 and Δγ sub = 0, respectively, are significantly different. A similar difference was observed between the φ 1 and φ 2 values that lead to Δγ air = 0 and Δγ sub = 0 for the BCPs made with the thiol pair MTG and TFET. In the latter case, for Δγ sub = 0 two windows of φ 2 are identified, which can be explained by the thermodynamic interactions of the specific thiol pair and the A-b-(B-r-C) architecture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Alignment frustration in block copolymer films with block copolymer grafted TiO 2 nanoparticles under soft-shear cold zone annealing

Block copolymers (BCPs) have received significant attention as promising candidates for sequestering nanoparticles and fabrication of aligned nanostructures with optimal optical or electrical properties. We investigate the influence of static and dynamic thermal field on the alignment of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) BCP morphology with the loading of novel poly(methyl methacrylate-block-Polystyrene) (PMMA-b-PS)-grafted-TiO 2 nanoparticles (BCP-g-TiO 2 ). Observation of characteristics IR peaks for PMMA and PS in BCP-g-TiO 2 nanoparticles and Transmission Electron Microscopy (TEM) results of the outer coating of core nanoparticle, validate the grafting to approach in synthesizing BCP-g-TiO 2 . In this work, we report that under the sharp dynamic thermal field, at low loading of BCP-g-TiO 2 , there is good dispersion of nanoparticles in unidirectionally aligned BCP matrix in film interior probed by GISAXS, while, at high nanoparticle loading (~10 wt%), there is local frustration in the unidirectional alignment of the BCP matrix due to aggregation of BCP-g-TiO 2 nanoparticles. However, Grazing incidence small angle X-ray scattering (GISAXS) shows clearly that the BCP films remain largely locally ordered at the domain scale, despite these large perturbations to long-range ordering even at high loading level, while bringing in new TiO 2 functionality to the BCP films, such as UVO absorptivity or biofouling prevention, important to potential new applications of such membranes.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

blocks_3d: software for general 3d conformal blocks

We introduce the software blocks_3d for computing four-point conformal blocks of operators with arbitrary Lorentz representations in 3d CFTs. It uses Zamolodchikov-like recursion relations to numerically compute derivatives of blocks around a crossing-symmetric configuration. It is implemented as a heavily optimized, multi-threaded, C++ application. We give performance benchmarks for correlators containing scalars, fermions, and stress tensors. As an example application, we recompute bootstrap bounds on four-point functions of fermions and study whether a previously observed sharp jump can be explained using the “fake primary” effect. We conclude that the fake primary effect cannot fully explain the jump and the possible existence of a “dead-end” CFT near the jump merits further study.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

p-Block Metal Oxide Noninnocence in the Oxygen Evolution Reaction in Acid: The Case of Bismuth Oxide

The Pourbaix diagrams of p-block Pb, Sb, and Bi establish a robust stability for their oxides in acidic solutions. Such oxides have found utility as stable frameworks to support metals that are active for oxygen evolution reaction (OER) catalysis, but they also possess two-electron redox couples, which can potentially engender OER activity. Thus, the use of p-block oxide supports provides an imperative for understanding the OER activity of the unary oxides. Toward this end, we report BiO x films that are able to perform OER catalysis at moderate overpotentials for extended periods of operation (>110 h) in highly acidic solutions (pH 1.0–2.25) with no sign of decreased OER activity during operation at current densities of 1–5 mA cm –2 . X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and UV-vis spectroelectrochemistry reveal a change in the Bi oxidation state prior to OER catalysis, from predominantly Bi 3+ in the as-deposited films to primarily Bi 5+ in the catalytically active films. Furthermore, this transformation is accompanied by a prominent color change from orange to dark brown. Simulations of the cyclic voltammogram catalytic profiles suggest two OER pathways for BiO x involving Bi IV O x and Bi V O x catalysts with the Bi V O x pathway prevailing after catalyst activation. Together, these results demonstrate the ability of BiO x to facilitate OER in acid with high functional stability and underscore the noninnocent role that p-block metal oxides may play in OER catalysis in acidic media.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Characterization of a Sulfonated Poly(Ionic Liquid) Block Copolymer as an Ionomer for Proton Exchange Membrane Fuel Cells using Rotating Disk Electrode

Ionic liquid (IL) additives to both traditional and advanced oxygen reduction reaction (ORR) electrocatalysts have yielded remarkable improvements in catalyst performance and durability. However, incorporating ILs or IL-modified catalysts into the electrodes of a proton exchange membrane fuel cell (PEMFC) membrane electrode assembly (MEA) has proven to be challenging. Sulfonated poly(ionic liquid) block copolymers (S-PILBCP) present an opportunity to incorporate IL functionality directly into the ionomer, orthogonal to protonic conductivity. Here, we use a rotating disc electrode (RDE) to characterize the interface between a S-PILBCP and Pt catalyst in comparison to Nafion. Catalyst thin films prepared with S-PILBCP show an 80% improvement in the ORR activity over those containing Nafion. Thin films of S-PILBCP also show a significantly reduced degree of poisoning sulfonate adsorption on a Pt(111) surface in comparison to Nafion. Furthermore, these half-cell results provide useful insights that help to highlight the source of the impact of the S-PILBCP on PEMFC MEA performance.

25 ENERGY STORAGE↗
DOE OSTI2020

Long-Range Ordered Amorphous Atomic Chains as Building Blocks of a Superconducting Quasi-One-Dimensional Crystal

Crystalline and amorphous structures are two of the most common solid-state phases. Crystals having orientational and periodic translation symmetries are usually both short-range and long-range ordered, while amorphous materials have no long-range order. Short-range ordered but long-range disordered materials are generally categorized into amorphous phases. In contrast to the extensively studied crystalline and amorphous phases, the combination of short-range disordered and long-range ordered structures at the atomic level is extremely rare and so far has only been reported for solvated fullerenes under compression. Here, a report on the creation and investigation of a superconducting quasi-1D material with long-range ordered amorphous building blocks is presented. Using a diamond anvil cell, monocrystalline (TaSe4)(2)I is compressed and a system is created where the TaSe(4)atomic chains are in amorphous state without breaking the orientational and periodic translation symmetries of the chain lattice. Strikingly, along with the amorphization of the atomic chains, the insulating (TaSe4)(2)I becomes a superconductor. The data provide critical insight into a new phase of solid-state materials. The findings demonstrate a first ever case where superconductivity is hosted by a lattice with periodic but amorphous constituent atomic chains.

combination of crystalline and amorphous structure↗
DOE OSTI2022

A Moving Embedded Boundary Approach for the Compressible Navier-Stokes Equations in a Block-Structured Adaptive Refinement Framework

A computational technique has been developed to perform compressible flow simulations involving moving boundaries using an embedded boundary approach within the block-structured adaptive mesh refinement (SAMR) framework of AMReX [1], [91], [92]. We leverage the SAMR capability to obtain quantitatively accurate results whilst using robust, second-order finite volume schemes. A conservative, unsplit, cut-cell approach is utilized and a ghost-cell approach is developed for computing the flux on the moving, embedded boundary faces. A third-order least-squares formulation has been developed to compute the wall velocity gradients, and was found to significantly improve the performance of the solver in terms of the quantitative comparison of surface quantities such as the skin friction coefficient. Various test cases are performed to validate the method, and compared with analytical, experimental, and other numerical results in literature. Inviscid and viscous test cases are performed that span a wide regime of flow speeds - acoustic (harmonically pulsating sphere), smooth flows (expansion fan created by a receding piston) and flows with shocks (shock-cylinder interaction, shock-wedge interaction, pitching NACA 0012 airfoil and shock-cone interaction). A closed system with moving boundaries - an oscillating piston in a cylinder, showed that the percentage error in mass within the system decreases with refinement, demonstrating that the numerical scheme is conservative with grid refinement, but is not discretely conservative. Viscous test cases involve that of a horizontally moving cylinder at Re = 40, an inline oscillating cylinder at Re = 100, and a transversely oscillating cylinder at Re = 185. The judicious use of adaptive mesh refinement with appropriate refinement criteria to capture the regions of interest leads to well-resolved flow features, and good quantitative comparison is observed with the results available in literature.

adaptive refinement↗
DOE OSTI2022

Poly( N -vinylpyrrolidone)- block -Poly(dimethylsiloxane)- block -Poly( N -vinylpyrrolidone) Triblock Copolymer Polymersomes for Delivery of PARP1 siRNA to Breast Cancers

Nearly 20% of HER2-positive breast cancers develop resistance to HER2-targeted therapies requiring the use of advanced therapies. Silencing RNA therapy may be a powerful modality for treating resistant HER2 cancers due to its high specificity and low toxicity. However, the systemic administration of siRNAs requires a safe and efficient delivery platform because of siRNA’s low stability in physiological fluids, inefficient cellular uptake, immunoreactivity, and rapid clearance. We have developed theranostic polymeric vesicles to overcome these hurdles for encapsulation and delivery of small functional molecules and PARP1 siRNA for in vivo delivery to breast cancer tumors. The 100 nm polymer vesicles were assembled from biodegradable and non-ionic poly(N-vinylpyrrolidone) 14 -block-poly(dimethylsiloxane) 47 -block-poly(N-vinylpyrrolidone) 14 triblock copolymer PVPON 14 -PDMS 47 -PVPON 14 using nanoprecipitation and thin-film hydration. We demonstrated that the vesicles assembled from the copolymer covalently tagged with the Cy5.5 fluorescent dye for in vivo imaging could also encapsulate the model drug with high loading efficiency (40%). The dye-loaded vesicles were accumulated in tumors after 18 h circulation in 4TR breast tumor-bearing mice via passive targeting. We found that PARP1 siRNA encapsulated into the vesicles was released intact (13%) into solution by the therapeutic ultrasound treatment as quantified by gel electrophoresis. Additionally, the PARP1 siRNA-loaded polymersomes inhibited the proliferation of MDA-MB-361TR cells by 34% after 6 days of treatment by suppressing the NF-kB signaling pathway, unlike their scrambled siRNA-loaded counterparts. Finally, the treatment by PARP1 siRNA-loaded vesicles prolonged the survival of the mice bearing 4T1 breast cancer xenografts, with the 4-fold survival increase, unlike the untreated mice after 3 weeks following the treatment. These biodegradable, non-ionic PVPON 14 -PDMS 47 -PVPON 14 polymeric nanovesicles capable of the efficient encapsulation and delivery of PARP1 siRNA to successfully knock down PARP1 in vivo can provide an advanced platform for the development of precision-targeted therapeutic carriers, which could help develop highly effective drug delivery nanovehicles for breast cancer gene therapy.

60 APPLIED LIFE SCIENCES↗