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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Study of Superconductivity in YBa{sub 2}Cu{sub 3}O{sub 7-x}/SrTiO{sub 3} Composites

Superconducting properties of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO)/SrTiO{sub 3} (STO) polycrystalline composites were investigated. The composites were obtained by rapid thermal processing of the 20% YBCO–80% STO mixtures in the air in the temperature range 700–1000 °C for 2 min. Magnetization measurements showed that the superconducting critical temperature (T{sub c}) is practically not changed if optimally doped YBCO is used in YBCO/STO composites. In contrast, a strong increase of T{sub c} from 65 to 90 K was found in the case of underdoped YBCO. This increase of T{sub c} can be explained by unusually fast diffusion of oxygen from STO to YBCO grains in sintered composites. Obtained results show that the YBCO oxidation process can be significantly accelerated in underdoped YBCO/STO composites during rapid high-temperature processing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Microstructure and Mechanical Properties of CNT-Reinforced AZ31 Matrix Composites Prepared Using Hot-Press Sintering

AZ31 matrix composites reinforced by carbon nanotubes (CNTs) were fabricated using hot-press sintering. The microstructure and mechanical properties of the composites (denoted as Mg-3wt.%Al-1wt.%Zn-xwt.%CNTs, x = 0-1.5) were investigated. The results showed that the elastic modulus, yield strength, tensile strength and elongation of the composites were significantly improved when compared with the matrix alloy AZ31. Of the tested composites Mg-3wt.%Al-1wt.%Zn-1.0wt.%CNTs exhibited the most favorable mechanical properties: compared with Mg-3wt.%Al-1wt.%Zn, the elastic modulus improved by 25.85%, yield strength increased by 23.48%, and tensile strength and elongation showed 19.35 and 48.23% improvement, respectively. The fracture surface of the Mg-3wt.%Al-1wt.%Zn-CNTs composites displayed features of brittle fracture, which suggests that CNTs do not markedly enhance the plasticity of AZ31.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Static and Dynamic Mechanical Properties of Graphene Oxide-Incorporated Woven Carbon Fiber/Epoxy Composite

This study investigates the synergistic effects of graphene oxide (GO) on the woven carbon fiber (CF)-reinforced epoxy composites. The GO nanofiller was incorporated into the epoxy resin with variations in the content, and the CF/epoxy composites were manufactured using a vacuum-assisted resin transfer molding process and then cured at 70 and 120 °C. An analysis of the mechanical properties of the GO (0.2 wt.%)/CF/epoxy composites showed an improvement in the tensile strength, Young’s modulus, toughness, flexural strength and flexural modulus by ~ 34, 20, 83, 55 and 31%, respectively, when compared to the CF/epoxy composite. The dynamic mechanical analysis of the composites exhibited an enhancement of ~ 56, 114 and 22% in the storage modulus, loss modulus and damping capacity (tanδ), respectively, at its glass transition temperature. The fiber–matrix interaction was studied using a Cole–Cole plot analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Corrosion Performance of Composite MAO/TiO{sub 2} Sol–Gel Coatings on Magnesium Alloy AZ91D

In this paper, the composite coatings on the surface of magnesium alloy were successfully prepared by the combination of micro-arc oxidation (MAO) and sol–gel method. Oxide ceramic layers were formed on AZ91D magnesium alloy using MAO process. The sol–gel layers were coated on MAO ceramic layers. The composition of the composite coatings was analyzed by x-ray diffraction and x-ray photoelectron spectroscopy. The microstructure of the composite coatings was analyzed by scanning electron microscope. The results show that the composite coatings can reduce the gap membrane effectively. The polarization curves and electrochemical impedance spectroscopy were used to evaluate the corrosion resistance. The results of corrosion tests show that the sol–gel layer enhances the corrosion resistance of the magnesium alloys significantly.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Study on Texture Evolution and Shear Behavior of an Al/Ni/Cu Composite

The microstructure, texture, and mechanical properties of the Al/Ni/Cu composite during various accumulative roll bonding (ARB) cycles were studied using optical microscopy, scanning electron microscopy, x-ray diffraction, shear punch test, and hardness test. In addition, ImageJ software and Rietveld software were used in order to study microstructure and dislocation density variations, respectively. It was found that Ni and Cu layers were fractured and distributed in the Al matrix due to differences in their mechanical properties. Fracture and distribution of Cu and Ni particles after cycle five led to the alteration of the composite structure from a layered to a particle-reinforced structure. ARB process leads to the formation of strong orientation along the β-fiber and also to pronounced copper and dillamore components in both Al and Cu phases. Furthermore, the shear yield stress and ultimate shear strength of the composite increased as the ARB process advanced; however, shear elongation presented a non-uniform variation. Investigation of the fracture surfaces revealed that the mechanical properties of the composite are affected not only by the strain hardening of the Cu layer, but also by the structural change in the composite during the initial ARB cycles. During the last stages of the process, however, changes in mechanical properties were mostly governed by reinforcement particles serving as strain concentration zones and the strain hardening of the Al matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Development of Pore-Free Ti-Si-C MAX/Al-Si Composite Materials Manufactured by Squeeze Casting Infiltration

Open-porous MAX phase skeletons from Ti{sub 3}SiC{sub 2} were manufactured by Microwave-Assisted Self-propagating High-temperature Synthesis (MASHS) and subsequently subjected to squeeze casting infiltration with an Al-Si lightweight casting alloy (EN AC-44200). This alloy was chosen due to its high flowability, corrosion resistance and good machinability. The manufactured composites, together with a reference sample of the original alloy, underwent testing of thermal properties, including thermal conductivity and diffusivity, specific heat and thermal expansion in the temperature range 50-500 °C, which corresponds to the expected working temperatures of the material. The fabricated AlSi/Ti{sub 3}SiC{sub 2} composites have significantly increased thermal stability, with coefficients of thermal expansion (approximately 10-11 × 10{sup −6} °C{sup −1}) half that of the original alloy. As regards mechanical properties, the instrumental Young’s modulus and Vickers hardness of the composite materials are 170.8 and 8.5 GPa, respectively. Moreover, the microstructure and phase composition, structural defects and potential impacts between constituents of the manufactured composites were characterized using SEM, TEM and STEM microscopy and EDS and XRD analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Fused filament fabrication of novel phase-change material functional composites

Additively manufactured polymer heat exchangers are of recent interest in the thermal sciences due to their lightweight and intricate heat-transfer-enhancing geometrical features. The goal of the present research is to directly encapsulate phase-change material (PCM) into polymer filament for the purpose of 3D printing polymer heat exchangers capable of latent heat thermal energy storage and management. PCMs have the ability to absorb large amounts of latent heat while undergoing a solid-to-liquid phase change at a nearly constant temperature. Encapsulation or containment of PCMs is necessary to prevent leaking since the material continuously cycles between a liquid and a solid state. An organic-based PCM and high-density polyethylene (HDPE) were combined and extruded into a functional composite filament. For the first time, with the aid of a heated enclosure and HDPE build plates, it was demonstrated that these functional composite materials can be printed using fused filament fabrication (FFF). Printing HDPE is known to be difficult; however, based on what was observed in the current study, the PCM and HDPE composite was easier to print than pure HDPE. Thermal properties, such as latent heat of fusion, phase-change temperature, and thermal conductivity, of the composite filament and 3D printed samples were investigated and compared with compression-molded bulk material. Finally, the microstructures of the composite filament and 3D printed samples were visualized, and the basic structures of the HDPE and PCM within both the filament and 3D printed parts were clearly delineated.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Development and thermal performance verification of composite insulation boards containing foam-encapsulated vacuum insulation panels

High-performance thermal insulation is a critical need for buildings. This article presents the development and thermal characterization of composite foam insulation boards containing low-cost vacuum insulation cores. The composite foam-vacuum insulation boards were created in a semi-automatic operation in a foam insulation manufacturing plant. The low-cost vacuum insulation is a new technology called modified atmosphere insulation. The production process of modified atmosphere insulation is much simpler than traditional vacuum insulation manufacturing, and it has the potential for significant cost reduction at the same thermal performance. Prototypes of small- and full-scale composite insulation boards were created for testing and evaluation under laboratory and natural weatherization conditions. The laboratory tests showed that the overall thermal resistance of the composite insulation board is at least twice that of current rigid foam insulation used in building envelope. Lastly, ongoing test of the composite insulation in a natural exposure test facility indicates that the high thermal performance was retained through handling and installation as well as natural aging over a period of one and a half years.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2024

3D printed lignin/polymer composite with enhanced mechanical and anti-thermal-aging performance

Lignin is the most abundant natural aromatic polymer globally but is still underutilized as a renewable material, even with its versatile properties. One approach to using lignin is to incorporate it in polymer composites, but this application is often limited by the poor mechanical performance of the resultant composite due to the poor interfacial adhesion. Following the structure–property relationship, stronger interactions were designed to be enhanced by alternating the functional groups of lignin. Here, this study applied a demethylation method to hardwood lignin (Ori-Lig) to introduce more phenolic hydroxyl groups. Research studies with rheology behavior and molecular simulations demonstrated that an increased phenolic hydroxyl content could improve the adhesion between the modified lignin (OH-Lig) and the polymer matrix at the interface. The tensile performance of the samples from the fused depositional modeling (FDM) 3D printing technique was also improved due to the improved interfacial adhesion. Specifically, by adding 10 wt% of the modified lignin, the tensile strength of the 3D printed samples could reach 46.1 MPa (40.2 MPa of Polyamide 12, PA12), and Young’s Modulus could be improved to 1.73 GPa (1.48 GPa of PA12). OH-Lig also improved anti-aging performance so that the tensile strength of the OH-Lig composite after thermo-aging (100 h at 140 °C) remained ~48MPa. The enhanced mechanical performance with anti-aging properties indicated that the OH-Lig composite may replace PA12 to reduce the use of petrol-based materials. This work showed the method of purposefully designing and modifying lignin structures to fulfill the interaction requirements between lignin and polymer matrix. The as-prepared lignin could be used to prepare functional composites to achieve improved mechanical performance and targeted functions at the same time.

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

Stable perovskite-fluorite dual-phase composites synthesized by one-pot solid-state reactive sintering for protonic ceramic fuel cells

We report that this work synthesized a series of oxide composites with nominal compositions of BaCe 05 Zr 0.4 Y 0.1 O 3-δ (BCZY)-Ce 0.5 Y 0.5 O 2-δ (YDC) based on the BCZY/YDC molar ratios of 0.5:1, 1:1, 2:1, and 4:1 (BCZY-YDC-0.5–1, BCZY-YDC-1-1, BCZY-YDC-2-1, and BCZY-YDC-4-1) using a one-pot solid state reactive sintering (SSRS) method. The X-ray diffraction (XRD) patterns and refinement proved that the one-pot SSRS at 1450 °C for 12 h could achieve the perovskite-fluorite dual-phase composites (DPCs) with the desired structure compositions. The scanning electron microscopy (SEM) images showed that the two DPCs of BCZY-YDC-1-1 and BCZY-YDC-2-1 formed excellent percolation for perovskite and fluorite phases. The conductivity measurement by electrochemical impedance spectroscopy (EIS) and the transference number measurement by the electromotive force (EMF) test proved that changing the BCZY/YDC molar ratio and operating condition could adjust the DPC's conduction property to make them suitable for electrolytes and electrode scaffolds for protonic ceramic fuel cells (PCFCs). The long-term conductivity testing and the crystal structure analysis after EMF testing under versatile conditions indicated that the DPCs of BCZY-YDC-2-1 and BCZY-YDC-1-1 were durable PCFC component materials. The PCFC button cells with the as-discovered BCZY-YDC-2-1 and BCZY-YDC-1-1 as an electrolyte and an anode scaffold, respectively, and the reported Ba–Ce–Fe–Co–O perovskite-perovskite composite as a cathode showed promising performance under H 2 /air gradient.

08 HYDROGEN↗
DOE OSTI2020

Real-time cure monitoring of fiber-reinforced polymer composites using infrared thermography and recursive Bayesian filtering

Despite the desirable characteristics of fiber-reinforced polymer (FRP) composites, their utilization in high volume production industries is limited by a lack of efficient manufacturing techniques. Monitoring the curing process of these composites can help with improving the quality and efficiency of the manufacturing process. This article discusses a method that uses Kalman-filter-based fusion of the information obtained from infrared thermography (surface temperature measurements) and a heat conduction model to estimate degrees of cure and internal temperatures of curing FRP composite parts in real time. The effectiveness of the methodology is demonstrated by successfully monitoring the curing of an FRP composite part in a laboratory experiment. Finally, the proposed methodology is a crucial step towards identifying anomalies in the curing process that negatively impact the quality of FRP composite parts.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Investigation of 3D printed lightweight hybrid composites via theoretical modeling and machine learning

Hybrid composites combine two or more different fillers to achieve multifunctional or advanced material properties, such as lightweight and enhanced mechanical properties. The properties of the composites significantly depend on their microstructures, which can be tailored via advanced 3D printing processes. Understanding the process-structure-property relationships is critical to enable the design and engineering of novel hybrid composites for applications in aerospace, automotive, and protective coatings. Here, for this work, we develop 3D printable and lightweight hybrid composites and leverage the conventional design of experiments, a theoretical hybrid model, and an image-driven machine learning (ML) method to investigate their mechanical behaviors. The hybrid composites are formulated with elastomer matrix, microfillers, and thin-shell particles, enabling a significant degree of design freedom of microstructures with densities and mechanical properties varying up to 70% and 91%, respectively. Our statistical analysis indicates that the 3D printing path direction and the microfibers fraction are dominating process parameters with contribution percentages of 45.3% and 57.7% on the specific stiffness and strength, respectively. A hybrid mechanics model is developed based on a simple Weibull distribution function and classical single-filler models to effectively capture the variations in mechanical properties, however, it overestimates the values due to its statistical constraints and idealization of experimental uncertainty. The image-driven ML model leverages the microscale images directly without losing the structural details, shows more accurate predictions with experimental data, and has 48.6% lower root mean square error than the theoretical model.

3D printing↗
DOE OSTI2020

Experimental investigation on the effects of fabric architectures on mechanical and damage behaviors of carbon/epoxy woven composites

The mechanical behaviors and damage evolutions of carbon/epoxy woven fabric composites with three different geometries, i.e., one plain weave and two twill weave patterns with different areal densities, are studied under tensile loading. The effects of weave patterns on mechanical properties are investigated by monotonic and cyclic tension tests. Remarkable variations in stress–strain curve, Poisson’s ratio, residual strain and strain map exist in the three composites. Crimp ratio is found to be a critical factor to govern the mechanical properties. With smaller crimp ratio, a quasi-linear stress–strain curve with higher elastic modulus and strength is observed. The stress–strain curves of composites with higher crimp ratio contain transition stages with significant tangent modulus degradation. Elastic modulus, strength and damage initiation are all correlated with the crimp ratio linearly regardless of the fabric pattern. Dramatic nonlinear evolution in Poisson’s ratio occurs in the composite with higher crimp ratio. Cyclic tension results indicate that the residual strain is a more appropriate damage indicator than the unloading elastic modulus. Microstructure examination shows that damage developments are essentially related to the fabric geometry, and result in various mechanical behaviors. This work provides important insights into the geometry-deformation mechanism-mechanical property relationship of the woven composites.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Corrosion of Al 2 O 3 /Cr and Ti 2 O 3 /Cr composites in flowing air and CO 2 at 750°C

Hot-pressed Al 2 O 3 /Cr and Ti 2 O 3 /Cr composites were exposed to synthetic air or CO 2 at 750 °C. The Al 2 O 3 /Cr composites formed external Cr 2 O 3 scales, and exhibited slow parabolic oxidation kinetics, in both gases. The Cr 2 O 3 scales formed in CO 2 possessed finer grains, and thickened at a faster rate, than Cr 2 O 3 scales formed in air. The Ti 2 O 3 /Cr composites formed thick external TiO 2 scales with internal oxidation zones that also contained Cr 2 O 3 scales on subsurface Cr grains. After 20 h at 750 °C, the Ti 2 O 3 /Cr composites exhibited parabolic oxidation kinetics in both gases, although the oxidation rates were significantly higher than for the Al 2 O 3 /Cr composites.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Consolidation of cubic and hexagonal boron nitride composites

When we Consolidate cubic boron nitride (cBN) it typically requires either a matrix of metal bearing materials that are undesirable for certain applications, or very high pressures within the cBN phase stability field that are prohibitive to manufacturing size and cost. We present new methodology for consolidating high stiffness cBN composites within a hexagonal boron nitride (hBN) matrix (15–25 vol%) with the aid of a binder phase (0–6 vol%) at moderate pressures (0.5–1.0 GPa) and temperatures (900–1300 °C). The composites are demonstrated to be highly tailorable with a range of compositions and resulting physical/mechanical properties. Ultrasonic measurements indicate that in some cases these composites have elastic mechanical properties that exceed those of the highest strength steel alloys. Moreover, two methods were identified to prevent phase transformation of the metastable cBN phase into hBN during consolidation: 1. removal of hydrocarbons, and 2. increased cBN particle size. Lithium tetraborate worked better as a binder than boron oxide, aiding consolidation without enhancing cBN to hBN phase transformation kinetics. These powder mixtures consolidated within error of their full theoretical mass densities at 1 GPa, and had only slightly lower densities at 0.5 GPa. This shows potential for consolidation of these composites into larger parts, in a variety of shapes, at even lower pressures using more conventional manufacturing methods, such as hot-pressing.

36 MATERIALS SCIENCE↗
DOE OSTI2022

The evolution of composition and morphology during the initial growth of electrodeposited Ni-Fe films: Comparison between the potentiostatic mode and the pulse-reverse potential mode

The anomalous codeposition of Ni-Fe tends to develop a composition gradient zone along the growth direction within the near-substrate region. Although it has been shown that such a composition gradient can be mitigated by the pulsed deposition method, a fundamental understanding of this behavior based on the anomalous codeposition mechanism has not been achieved yet. In this work, the evolution of the composition and the morphology during the (pulsed) electrodeposition of Ni-Fe films was reported. Further, a theory based on the Fe deposition mechanism originally described by Bockris, Drazic, and Despic was proposed and described in detail, which was used to rationalize not only the occurrence and the decline of the composition gradient, but also the opposite signs of the composition gradient observed under the potentiostatic mode and the pulse-reverse potential mode.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

A comprehensive study on two types of supercapacitor composite electrodes comprising MnO 2 and activated carbon nanofibers: Self-supporting membrane and ground powder

Manganese dioxide (MnO 2 )@carbon composites have been attractively considered as electrode materials for supercapacitors (SCs) due to synergistic effects. This work systematically investigated the structure of MnO 2 @carbon nanofiber (CNF) composite electrodes with the different forms of CNFs and the corresponding electrochemical performance of SCs. In brief, novel activated carbon nanofibers were first fabricated by electrospinning the hydroxyl-containing poly(amic acid) solution, and then the preferred CNF material was decorated by MnO 2 crystals in the form of self-supporting membrane and ground powders, respectively. Additionally, the synthesis parameters were investigated and optimized based on the electrochemical performance of SCs. The results reveal that the powdered composite electrode exhibits a higher specific surface area of 501 m 2 g –1 compared to the self-supporting membrane composite electrode under the same conditions, resulting in a promising specific capacity of 214.1 mAh g –1 (770.8 Fg –1 ) in 6M KOH solution at 0.5 A g –1 . In addition, the capacitance of the symmetrical SC device assembled by G-HMC-1:3–80 reaches 179.8 Fg –1 , coupled with an energy density of 24.86 Whkg –1 at 230 Wkg –1 power density. This work provides valuable hints for designing SC composite electrode materials with outstanding performance.

25 ENERGY STORAGE↗
DOE OSTI2017

Martensitic transformation in a B2-containing CuZr-based BMG composite revealed by in situ neutron diffraction

Here, CuZr-based bulk-metallic-glass (BMG) composites reinforced by a B2-type CuZr crystalline-phase (CP) have been widely studied, and exhibit that the plastic deformation of the CP induces martensitic transformation from the B2 to B19', which plays a dominant role in the deformation behavior and mechanical properties. In the present study, 2.0% Co containing CuZr-based BMG composites were investigated using in-situ neutron-diffraction technique. The in-situ neutron-diffraction results reveal the continuous load transfer from the glass matrix to B2 CP and martensitic transformation from the B2 CP to B19' during the deformation of the composite. Moreover, it was found that the martensitic transformation is initiated at the applied stress higher than 1500 MPa, and is significantly suppressed during the deformation, as compared to other 0.5% Co-containing CuZr-based BMG composites. Based on these in-situ neutron-diffraction results, the martensitic transformation is strongly affected by the amount of the addition of Co, which determines the mechanical properties of CP-reinforced BMG composites, such as ductility and hardening capability.

36 MATERIALS SCIENCE↗

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