Search NASA⌕ Search

SEARCH · Search NASA

Results for “matrix structures”

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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Three-dimensional printed porous silicone matrix using leachable porogen

The silicone-based ink for additive manufacturing includes a siloxane macromer, and a porogen mixture comprising a water-soluble porogen and a surfactant. The product of additive manufacturing with a silicone-based ink includes a three-dimensional printed structure including a plurality of continuous filaments arranged in a predefined pattern and a plurality of inter-filament pores defined by the predefined pattern of the continuous filaments. In addition, each continuous filament of the three-dimensional printed structure includes a silicone matrix having an open cell structure with a plurality of intra-filament pores, and the intra-filament pores form continuous channels through the silicone matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Microstructural and micromechanical characteristics of ultra-high performance concrete with superabsorbent polymer (SAP)

In this study, the hydration product, C-S-H density, and pore structure at different layers from the drying surface were measured. Besides, the zone affected by the released internal curing water from SAP was identified by assessing the nanoindentation modulus. The results found that the SAP affected the moisture distribution and changed the evaporation and self-desiccation rates in the inner and outer layers. Such imposed moisture gradients affected the micromechanical properties of UHPC at different layers due to the change in the hydration degree of the binder, the density of C-S-H, and the pore structure of the matrix. The addition of SAP improved the hydration dynamics and transferred the LD C-S-H into HD or UHD C-S-H. As the distance from the drying surface increased, the affected zone of SAP increased from 60 to 120 μm, showing the more effectiveness of SAP at inner layers.

36 MATERIALS SCIENCE↗
NASA NTRS1974

Connective stability of nonlinear matrix systems

Consideration of stability under structural perturbations of free dynamic systems described by the differential equation dx/dt = A(t,x)x, where the matrix A(t,x) has time-varying nonlinear elements. The concept of 'connective stability' is introduced to study the structural properties of competitive-cooperative nonlinear matrix systems. It is shown that stability reliability in such systems is high and that they remain stable despite time-varying (including 'on-off') interaction among individual agents present in the system. The results obtained can be used to study stability aspects of mathematical models arising in as diverse fields as economics, biology, arms races, and transistor circuits.

Siljak, D. D.↗
NASA NTRS1979

High resolution transmission electron microscopy of two stony meteorites - Murchison and Kenna

Matrix material from the Murchison C2(M) carbonaceous chondrite and less than micrometer-size pyroxene inclusions in an olivine from the Kenna ureilite have been characterized using high resolution transmission electron microscopy. A diversity of textures and mineral associations, including serpentine-type and brucite-type mixed-layering, occur in the Murchison matrix. Such mixed layer structures are new types of layer silicate. Their presence in the matrix may prove to be genetically significant. The Kenna inclusions, formed at the olivine grain margins, are of two types: (1) a disordered orthopyroxene-clinopyroxene which may have inverted from protopyroxene and (2) a pigeonite with narrow anti-phase domains (80 A to 250 A) and boundaries parallel to (100).

Mackinnon, I. D. R.↗
DOE OSTI2014

Investigation of the Feasibility of Utilizing Gamma Emission Computed Tomography in Evaluating Fission Product Migration in Irradiated TRISO Fuel Experiments

In the High Temperature Gas-Cooled Reactor (HTGR) the TRISO particle fuel serves as the primary fission product containment. However the large number of TRISO particles present in proposed HTGRs dictates that there will be a small fraction (~10 -4 to 10 -5 ) of as manufactured and in-pile particle failures that will lead to some fission product release. The matrix material surrounding the TRISO particles in fuel compacts and the structural graphite holding the TRISO particles in place can also serve as sinks for containing any released fission products. However data on the migration of solid fission products through these materials is lacking. One of the primary goals of the AGR-3/4 experiment is to study fission product migration from failed TRISO particles in prototypic HTGR components such as structural graphite and compact matrix material. In this work, the potential for a Gamma Emission Computed Tomography (GECT) technique to non-destructively examine the fission product distribution in AGR-3/4 components and other irradiation experiments is explored. Specifically, the feasibility of using the Idaho National Laboratory (INL) Hot Fuels Examination Facility (HFEF) Precision Gamma Scanner (PGS) system for this GECT application is considered. To test the feasibility, the response of the PGS system to idealized fission product distributions has been simulated using Monte Carlo radiation transport simulations. Previous work that applied similar techniques during the AGR-1 experiment will also be discussed as well as planned uses for the GECT technique during the post irradiation examination of the AGR-2 experiment. The GECT technique has also been applied to other irradiated nuclear fuel systems that were currently available in the HFEF hot cell including oxide fuel pins, metallic fuel pins, and monolithic plate fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Bio-inspired nanocomposite by layer-by-layer coating of chitosan/hyaluronic acid multilayers on a hard nanocellulose-hydroxyapatite matrix

We report on a layer-by-layer technique on the hard CNCs/hydroxyapatite (HAP) matrix using biodegradable and biocompatible chitosan and hyaluronic acid (HA). Inspired by the mineralized collagen in human bone, the CNCs/HAP matrix was synthesized by a facile in situ HAP coating on the CNCs fibers. The chemical and crystalline structure of the CNCs/HAP matrix was investigated with FTIR, XRD, HRTEM, and SAED. The surface of the CNCs/HAP matrix was analyzed by AFM which showed a flat structure with a roughness of 23.12 nm, however, the surface roughness increased to 56.09 nm with the assembly of chitosan and HA. After the LBL assembly, the surface hydrophilicity of the CNCs/HAP films was improved. Furthermore, the CNCs/HAP matrix showed enhanced mechanical property than pure CNCs matrix. Although there is compromise in the mechanical property after the LBL assembly, it is anticipated its bioaffinity and biocompatibility will increase with the incoporation of chitosan and HA.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Automated phase segmentation and quantification of high-resolution TEM image for alloy design

In the alloy design and development process, a wealth of atomically resolved structural high-resolution transmission electron microscopy (HRTEM) images are produced. Identifying the different nano-precipitate phases and tracking their evolution under various compositions and during manufacturing or post-processing requires hundreds of HRTEM images and thousands of precipitates. The nanoscopic phase information labeling and analysis purely relies on humans are prohibitively costly and time-consuming, sometimes not reliable because of the lack of authoritative knowledge. Here, in this work, we develop a novel unsupervised machine learning approach coupled with adaptive computer vision techniques with features in the Fourier space to automatically determine the number of phases and segment/quantify the phases with nanoscale resolution, allowing for quantitative correlation between nanostructure formation, processing and functional properties. To automate the phase extraction/quantification and ascertain its applicability, we have applied the developed framework to the HRTEM images from several alloy systems, processing conditions, image magnifications, and phase types and morphologies (precipitates, nano-twins, stacking faults, crystalline matrix, and amorphous structures) for verification. This study paves the road for compression, visualization, and translation of raw image structural data into physically relevant information in real-time with minimal human supervision. It shows the promise of enabling high-throughput materials characterization for the acceleration of alloy manufacturing and design.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Three-dimensional morphology of CuInS{sub 2}:P3HT hybrid blends for photovoltaic applications

Despite potential advantages, the performance of hybrid solar cells with colloidal nanocrystals remains low compared to pure organic solar cells, in particular, when Cd- and Pb-free nanocrystals are employed. To understand this discrepancy, we analyzed possible limiting factors of the performance of hybrid solar cells with CuInS{sub 2} nanoparticles and the polymer poly(3-hexylthiophene) (P3HT). Optimizing the thickness of the active layer indicated that charge transport limits the performance of the solar cells. Since charge transport is among others influenced by the morphology of the bulk heterojunction layer, we performed a detailed analysis of the blend morphology. Therefore, we used electron tomography which provides three-dimensional information on the interpenetrating network formed by the hybrid CuInS{sub 2}:P3HT system. Using statistical methods, we analyzed the distribution of the nanoparticles inside the polymer matrix and the structure of the percolation paths. We found that the morphology appears well suited for application in hybrid solar cells, meaning that other factors must be the bottleneck. Therefore, we investigated in a second step the influence of a post-deposition ligand exchange with acetic acid. This strategy resulted in a strong relative improvement of the solar cell performance, although absolute performance parameters remain low in comparison to hybrid solar cells with colloidal cadmium or lead chalcogenide nanocrystals.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Textural properties determined CO 2 capture of tetraethylenepentamine loaded SiO 2 nanowires from α-sepiolite

To understand the effect of porous parameters and chemical components on CO 2 capturing performance of solid state amine absorbents and their kinetic parameters, a clay mineral-based CO 2 absorbent was prepared by impregnating five different liquid amines onto SiO 2 nanowire clusters from fibrous sepiolite (Sep). Characterization was conducted by XRD, SEM, FTIR, and N 2 adsorption–desorption isotherm, CO 2 adsorption performances were measured by TGA. After acid treatment, the raw Sep mineral changed into amorphous silica nanowires, and the largest S BET of the obtained SiO 2 nanowires reached 320 m 2 /g, which was 8 times larger than the pristine mineral. Amongst the adapted amines, tetraethylenepentamine (TEPA) showed superiority in the CO 2 adsorption capacity. The optimized adsorption capacity reached 3.7 mmol/g at 75 °C from a CO 2 + N 2 mixture on a ~50 wt% TEPA loaded SiO 2 sample, and the capacity remained 3.6 mmol/g after ten circles of adsorption/desorption tests. The pore size and pore structure of the matrix, rather than the surface area, will obviously affect the adsorption ability of the product. Kinetic parameters for the CO 2 adsorption process fitted well with a fractional-order model, confirming that the CO 2 adsorption process by the solid absorbent should be a combination of both physical and chemical reactions. Results in this article provide detailed parameters for preparing and understanding these clay mineral based solid state CO 2 absorbents.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Closed-form solutions for linear regulator design of mechanical systems including optimal weighting matrix selection

Vibration in modern structural and mechanical systems can be reduced in amplitude by increasing stiffness, redistributing stiffness and mass, and/or adding damping if design techniques are available to do so. Linear Quadratic Regulator (LQR) theory in modern multivariable control design, attacks the general dissipative elastic system design problem in a global formulation. The optimal design, however, allows electronic connections and phase relations which are not physically practical or possible in passive structural-mechanical devices. The restriction of LQR solutions (to the Algebraic Riccati Equation) to design spaces which can be implemented as passive structural members and/or dampers is addressed. A general closed-form solution to the optimal free-decay control problem is presented which is tailored for structural-mechanical system. The solution includes, as subsets, special cases such as the Rayleigh Dissipation Function and total energy. Weighting matrix selection is a constrained choice among several parameters to obtain desired physical relationships. The closed-form solution is also applicable to active control design for systems where perfect, collocated actuator-sensor pairs exist.

Hanks, Brantley R.↗
DOE OSTI2013

Experimental studies of nuclear matrix elements for neutrino-less ββ decays

Nuclear matrix elements M{sup 0ν} for neutrino less double beta decays (0νββ) are crucial for neutrino studies in 0νββ experiments. The neutrino mass to be studied is sensitive to M{sup 0ν}, while theoretical calculations for M{sup 0ν} are hard. Thus experimental studies of nuclear structures and single β matrix elements M{sub β} associated with 0νββ are useful to confirm and help the theoretical calculations. This reports briefly experimental methods and recent charge exchange reaction studies for M{sub β}. The single β elements for M{sup ±}(2{sup −}) associated with M{sup 0ν}(2{sup −}), which is the major component of M{sup 0ν}, are found to be reduced (quenched) much by the spin isospin correlation and the nuclear medium (non-nucleonic isobar) effect. The present result suggests that the spin isospin components of M{sup 0ν} is fairly reduced (quenched)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed into the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2017

An accurate and asymptotically compatible collocation scheme for nonlocal diffusion problems

Here, in this paper, we develop and analyze a collocation scheme for solving the linear nonlocal diffusion problem with general kernels. To approximate the nonlocal diffusion operator, we take a classic trapezoidal rule based on the linear interpolation as the starting point, and then carefully derive a new improved quadrature rule, which is not only more accurate but also could avoid the evaluations of singular integrals. We then use this rule to construct a collocation scheme for solving the nonlocal diffusion equations, that produces a symmetric positive definite stiffness matrix with Toeplitz structure. The proposed scheme is rigorously shown to be of second order accurate with respect to the mesh size for the nonlocal problem with fixed horizon, and in particular, it can achieve higher order accuracy for the commonly used kernels in the literature. Furthermore, we also prove that the scheme is asymptotically compatible, i.e., the approximate solution of the nonlocal diffusion problem converges to the exact solution of the corresponding local PDE problem when the horizon and the mesh size both go to zero. Finally, numerical experiments are presented to verify the theoretical results.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Osteocytic oxygen sensing: Distinct impacts of VHL and HIF-2alpha on bone integrity

Skeletal fracture resistance emerges from multiple components of bone structure like microarchitecture, matrix mineralization, and organization. These characteristics are engendered via mechanisms like the hypoxia-inducible factors (HIF) pathway, involving two paralogs, HIF-1α and HIF-2α. Under normoxia, HIF-α is targeted for degradation via von-Hippel Lindau (VHL); hypoxia enables HIF-α stabilization and induction of target genes. We previously showed that osteocytic Vhl deletion or expression of degradation-resistant HIF-2α cDR female mice each produced high bone mass, whereas degradation-resistant osteocytic HIF-1α produced no overt phenotype. We report within that Vhl cKO increased bone strength, while HIF-2α cDR displayed markedly reduced bone strength below Cre-negative controls. This suggests that VHL and HIF-2α drive distinct responses that promote disparate effects on bone strength. Both Vhl deletion or HIF-2α accumulation generated two discrete bone morphologies: an outer lamellar cortex and a woven, poorly mineralized endocortex that imparted dramatically different functional outcomes. Our studies reveal novel influence of osteocytic HIF-2α signaling on collagen matrix organization, mineralization, and bone strength.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Structure and tribological properties of steel after non-vacuum electron beam cladding of Ti, Mo and graphite powders

The non-vacuum electron beam cladding technique was used to fabricate layers alloyed with Ti, Mo and C on the surface of low-alloyed steel. Two types of experiments were carried out. In the first experiment, a mixture of Ti and graphite powders was used for cladding; in the second, a mixture of Ti, Mo and graphite powders was used for cladding. CaF{sub 2} powder or a mixture of CaF{sub 2} and LiF powders was used as flux. The thickness of the cladded layers was in the range of 2–2.2 mm. The structure of the layers was studied using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The microhardness after cladding of the layers fabricated by cladding of Ti and graphite powders was 8–9 GPa, while the microhardness of layers with Mo additions reached 11–12 GPa. The highest wear resistance at sliding friction and friction in abrasive environment was reached in the samples fabricated using Ti, Mo and graphite mixture due to the higher hardness and the martensite–austenite structure of the matrix. The wear resistance against fixed abrasive particles was 2.4 times higher compared to that of carburized and quenched steel. - Highlights: • Ti, C and Mo mixture of powders was cladded using non-vacuum electron beam treatment. • The depth of the cladded layers was 2.0 … 2.2 mm. • The microhardness of layer with Mo, Ti and C additions reached ~ 11 … 12 GPa. • The hardening of the layers caused by the formation of TiC particles and martensitic matrix • Wear resistance of cladded coatings was 2.4 higher than carburized steel.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Surfactant-assisted intercalation of high molecular weight poly(ethylene oxide) into vanadyl phosphate di-hydrate

Graphical abstract: CuK{sub {alpha}} X-ray diffraction patterns of the VOPO{sub 4}/PEO (A) e VOPO{sub 4}/CTA (B) and VOPO{sub 4}/CTA/PEO (C). Highlights: Black-Right-Pointing-Pointer VOPO{sub 4}/PEO has been synthesized by using CTAB, thereby improving PEO intercalation. Black-Right-Pointing-Pointer The d-spacing increase from 1.30 nm (VOPO{sub 4}/PEO) to 2.94 nm (VOPO{sub 4}/CTA/PEO). Black-Right-Pointing-Pointer This strategy was viable for intercalation of PEO with high molecular weight. -- Abstract: A high molecular weight poly(ethylene oxide)/layered vanadyl phosphate di-hydrate intercalation compound was synthesized via the surfactant-assisted approach. Results confirmed that surfactant molecules were replaced with the polymer, while the lamellar structure of the matrix was retained, and that the material presents high specific surface area. In addition, intercalation produced a more thermally stable polymer as evidenced by thermal analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effect of Cr and Ni concentrations on resilience of cast Nb- alloyed heat resistant austenitic steels at extreme high temperatures

Austenitic Cr–Ni alloyed heat resistant steels with Nb additions are used for intensively thermo-mechanically loaded cast components working in extreme high temperature oxidizing environment. Their performance during static oxidation and transient thermo-mechanical loading was investigated to recommend an optimal cost-effective Cr/Ni composition of Nb-alloyed austenitic class steels. Here, the static oxidation and transient thermo-mechanical behavior of three austenitic steels with different Cr/Ni alloying levels were investigated and compared for variety of working conditions. Static oxidation was performed between 900 °C and 1000 °C in air for 400 h. The critical temperature which increases spallation during static oxidation was determined for each of the steel alloying levels. In addition, thermal cycling of a constrained specimen was done with varying upper cycling temperatures between 850 °C and 1000 °C. SEM and TEM analyses were supported by thermodynamic simulation of the phases precipitated in the metal matrix and the structure of formed oxide layers. These studies were used to determine the mechanisms of degradation of thermo-mechanically loaded Cr/Ni austenitic steels at extreme high temperatures. A recommendation for a cost-effective Cr/Ni alloying level for different working conditions was determined.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Mild chemical recycling of carbon fiber-reinforced epoxy composites in aqueous buffers and development of hydrothermally recyclable vitrimer composites from recyclates

Carbon fiber-reinforced polymer (CFRP) composites have gained widespread adoption across diverse industries. However, their inherent stability, stemming from the crosslinked structure of the matrix resin, poses a significant challenge in managing the growing volume of CFRP waste. Consequently, there is a pressing need for an eco-friendly upcycling method that effectively recovers and reuses both the valuable carbon fibers and the polymer matrix from CFRP waste. This study presents a novel approach for upcycling CFRP waste under environmentally friendly conditions. Firstly, CFRP waste with an amine-cured epoxy matrix was completely decomposed in aqueous buffer solutions under mild conditions (≤ 220 °C, pH = 4.8). Further, decomposed matrix polymer (DMP) was employed to transform conventional epoxy resins into recyclable vitrimers. Lastly, new composites that can be hydrothermally recycled were fabricated using both DMP and recovered carbon fibers. As a result, this work proposes a novel strategy for achieving a circular economy within the CFRP industry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗