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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 1,423 records · Page 79
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

AFe{sub 2}O{sub 4}/(Pb{sub 0.80}Sr{sub 0.20})TiO{sub 3} (A = Mn, Ni and Co): a New Room-Temperature Magnetoelectric Multiferroic Bi-layered Composite Films

The room temperature and magnetic field-dependent dielectric, impedance and magnetoelectric (ME) coupling effect of polycrystalline AFe{sub 2}O{sub 4}/(Pb{sub 0.80}Sr{sub 0.20})TiO{sub 3} (A = Mn, Ni and Co) bi-layered composite films have been investigated. The structural and microstructural analyses using the X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) reveal the presence of homogenous growth of both tetragonal and spinel phases without any extra phase and diffusion in the AFO/PST20 bi-layered composite films. Our results show that all composite films exhibit ferroelectric as well as considerable magnetic, indicating magnetoelectric coupling effect. Our results show that the dielectric and impedance properties of AFO/PST20 bi-layered composite films can be manipulated by the magnetic field at room temperature, also indicating the existence of magnetoelectric coupling. The impedance (Z{sup ′} and Z{sup ″}) Nyquist plots show distinct electrical responses with the magnetic field. The maximum magnetoelectric coefficient (α) is found to be α{sub ME}∼ 239 and ∼ 195 mV/cm/Oe for the MFO/PST20 and CFO/PST20 bi-layered composite films, respectively. The above results show that the AFO/PST20 bi-layered composite films are room-temperature multiferroic material that can be potentially used in magnetoelectric devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Thermal Properties of Carbon-Containing Iron Ore Composite Prepared by Vapor Deposition of Tar for Limonite

The optimal conditions for preparing composites, in which tar-derived carbonaceous materials completely fill the pores in Indonesian limonite(IL), were investigated using the vapor deposition (VD) method of tar. Characterization of the composites and their reactivity (reduction/combustion/gasification) during heat treatment was examined. The specific surface area and pore volume of the as-received-IL and dehydrated-IL decreased after the VD treatment for different combinations of tar pyrolysis temperature (TPT) and VD temperature (VDT). It was also noted that the carbon content and crushing strength of the samples increased after the VD treatment, and the optimal values for the TPT-VDT are 700 °C and 350 °C. The C content and the crushing strengths of the composites prepared at TPT-VDT = 700 °C to 350 °C increased with an increase of the VD time to 50 pct carbon content and 10 daN at 240 minutes, respectively. The strength was similar to that of commercial metallurgical coke used in blast furnaces. The reduction of the composite prepared at TPT-VDT = 700 °C to 350 °C for 240 minutes started above 400 °C and was almost completed at 1000 °C. This reduction rate was higher than that of commercial cold-bonded pellets or a coke/IL mixture. The combustion and gasification rates of the composites prepared under different conditions depended on the preparation condition of composites, and the rates were higher than those of commercial metallurgical coke used in blast furnaces.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Optimization of CCT Equations Using Calculated Grain Boundary Soluble Compositions for the Simulation of Austenite Decomposition of Steels

New CCT equations have been developed and optimized to simulate the start temperatures of the austenite decomposition process in low-alloyed steels using experimental CCT data published in the literature. Exceptionally, this optimization does not apply the nominal compositions of the steels, but the corresponding soluble compositions of the grain boundaries calculated using IDS software, depending on the reported austenitization treatments of the steels. These compositions, rather than the nominal ones, are expected to control the start of the austenite decomposition, which usually initiates at the grain boundaries. The new optimization treatment takes into account the solute microsegregation and the possible precipitate formation. Using IDS software, the new equations were validated with new experimental CCT data. Agreement was good not only for the austenite decomposition start temperatures, but also for the final phase fractions, indicating fairly reasonable predictions of phase transformation kinetics by the IDS. In addition, IDS simulations were compared with the experimental CCT data of five high-carbon steels, applying both the new equations based on grain boundary soluble compositions as well as the equations based on the nominal compositions. With the same experimental CCT data used in optimization, better agreement was obtained with the new equations, indicating the importance of determining the soluble compositions at the grain boundaries where the austenite decomposition process is likely to begin.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Effect of Titanium Dioxide (TiO{sub 2}) Nanoparticles on Hydroxyapatite (HA)/TiO{sub 2} Composite Coating Fabricated by Electrophoretic Deposition (EPD)

Composite coatings of Hydroxyapatite (HA) with ceramics, polymers and metals are used to modify the surface structure of implants. In this research, HA/TiO{sub 2} composite coating was fabricated by electrophoretic deposition (EPD) on 316 stainless steel substrate. HA/TiO{sub 2} composite coatings with 5, 10 and 20 wt.% of TiO{sub 2}, deposited at 40 V and 90 s as an optimum condition. The samples coated at this condition led to an adherent, continuous and crack-free coating. The influence of TiO{sub 2} content was studied by performing different characterization methods such as scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), corrosion resistance in simulated body fluid (SBF), coating’s dissolution rate in physiological solution and bond strength to the substrate. The results showed that the higher amount of TiO{sub 2} in the composite coating led to increase in bond strength of coating to stainless steel substrate from 3 MPa for HA coating to 5.5 MPa for HA-20 wt.% TiO{sub 2} composite coating. In addition, it caused to reduction of corrosion current density of samples in the SBF solution from 18.92 μA/cm{sup 2} for HA coating to 6.35 μA/cm{sup 2} for HA-20 wt.% TiO{sub 2} composite coating.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Corrosion Behavior of Zn/Graphene Oxide Composite Coatings Fabricated by Direct Current Electrodeposition

The zinc (Zn) and Zn/graphene oxide (Zn/GO) composite coatings on the mild steel were fabricated by direct current electrodeposition from an acidic chloride bath without GO and that with four different concentrations (50, 100, 200 and 300 mg/L) of GO, respectively. The GO first is synthesized by using the typical Hummer method. Physical characterizations including the surface and cross-sectional morphology, chemical composition and crystal structure of the Zn and Zn/GO composite coatings were done by scanning electron microscope, energy-dispersive x-ray and x-ray diffraction. The crystalline size, texture coefficient, water contact angle and hardness of the Zn and Zn/GO composite coatings were measured. The corrosion behavior of the Zn and Zn/GO composite coatings was studied by the electrochemical corrosion tests including the potentiodynamic polarization test and the electrochemical impedance spectroscopy test and the immersion test. The result reveals that the corrosion resistance of the Zn coating is remarkably increased by the incorporation of GO. Furthermore, it does not show a linear increase with the increase in the amount of incorporated GO and an optimal corrosion resistance is provided by the Zn/GO composite coating attained from the electrolyte containing 100 mg/L GO. The influence of the incorporation of GO on the corrosion resistance of the Zn coating is explained in combination with their physical characterizations.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Preparation and Oxidation Performance of a NiCoCrAlYSiHf + NiAl Composite Coating Deposited by Arc Ion Plating and Magnetron Sputtering Techniques

A NiCoCrAlYSiHf+NiAl composite coating was deposited onto a second-generation single-crystal superalloy René N5 by methods of arc ion plating and magnetron sputtering. After vacuum annealing, the composite coating exhibited a gradient distribution of elements, in which Al was enriched in outer layer and Cr was enriched in inner layer. Compared with conventional NiCoCrAlYSiHf and β-NiAl coatings, the composite coating was evaluated in isothermal and cyclic oxidation tests at 1100 °C in ambient air. The results showed that the oxidation rate of the composite coating was lower than that of NiCoCrAlYSiHf coating. Meanwhile, the extent of interdiffusion between coating and substrate in the composite coating was slighter compared with that in the β-NiAl coating. Microstructure evolutions of the composite coating after annealing and further oxidation test are investigated.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Prolonged Ultraviolet Radiation Exposure on the Blast Response of Fiber Reinforced Composite Plates

An experimental study with corresponding numerical simulations was conducted to evaluate the blast response of composite plates after prolonged exposure to ultraviolet radiation. Two composite materials were used in this study, namely carbon fiber/epoxy and glass fiber/vinyl ester. The composite materials consisted of four unidirectional fiber plies oriented in a [± 45°]s layup. The plates were placed in a QUV Accelerated Weathering Tester for 500 h of exposure on each face, totaling 1000 h of ultraviolet radiation exposure, equivalent to 2.5 MJ/m{sup 2} of energy. The QUV Accelerated Weathering Tester was equipped with eight UVA-340 lamps to provide real service life exposure conditions. Material characterization experiments were performed on virgin specimens, as well as specimens exposed to ultraviolet radiation for 1000 h to determine its effect on the mechanical properties of the composites. Blast experiments were conducted on the composite plates to investigate the dynamic response before and after exposure to ultraviolet radiation. The plates were clamped on all edges and subjected to an air blast using a shock tube apparatus. Three-dimensional digital image correlation was coupled with high-speed photography to obtain full-field displacements of the specimens during blast loading. Furthermore, three piezoelectric pressure transducers were mounted on the shock tube apparatus and utilized to measure the pressure history of the shock wave loading. The quasi-static material characterization showed that the tensile modulus E{sub 1} had minimal change after exposure to ultraviolet radiation for 1000 h. However, matrix-dominated properties such as the in-plane shear modulus G{sub 12} increased after exposure to ultraviolet light for both the carbon and glass fiber composites, which resulted in lower out-of-plane displacements during blast loading. For the carbon fiber plates, the forced vibration frequency induced by the transverse blast load was higher in plates exposed to ultraviolet radiation when compared to virgin specimens. However, for the glass fiber plates exposed to ultraviolet radiation, the forced vibration frequency decreased when compared to virgin specimens. Finally, the finite element simulations were in good agreement with the experimental results. The simulations revealed that the glass fiber plates exposed to ultraviolet radiation had higher failure strains at the boundary than virgin specimens, despite having higher stiffness. A parametric study in which higher loading was simulated also showed that the glass fiber plates experienced more damage after 1000 h of ultraviolet radiation exposure.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Fabrication, Microstructures, and Properties of 50 vol.% SiCp/6061Al Composites via Hot Pressing

Nearly fully dense 50 vol.% SiCp/6061Al composites were fabricated via hot pressing (HPing) at temperatures ranging from 610 to 650 °C, with the axial load and holding time fixed as 25 MPa and 120 min, respectively. The interfacial reactions, microstructures, and properties of the SiCp/Al alloy were studied. The interface reaction between SiCp and the Al alloy was suppressed at annealing temperatures of 620 °C and below; however, the reaction intensified as the annealing temperature increased, producing Al{sub 4}C{sub 3}, Si, and Mg{sub 2}Si. With an increase in HPing temperature from 610 to 630 °C, the 6061Al alloy melted and gradually filled the pores in the SiC particles under the applied load. The density, bending strength, and thermal conductivity (TC) of the composites increased, whereas the coefficient of thermal expansion (CTE) of the composites decreased. With an increase in HPing temperature increased from 630 to 650 °C, the 6061Al alloy melt leaked through the sintered bodies, resulting in the microstructural degradation and property reduction of the composites. The 50 vol.% SiCp/6061Al composites fabricated by HPing at 630 °C exhibited optimal comprehensive properties [bending strength, 332.4 MPa; TC, 186.3 W(m K){sup −1}; and CTE, 7.9 × 10{sup −6}/°C (20-100 °C)], which were attributed to the highest relative density and the best SiCp/Al interfacial structure of the composites.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Fabrication and Characterization of A5083-WC-Al{sub 2}O{sub 3} Surface Composite by Friction Stir Processing

In this study, WC-Al{sub 2}O{sub 3} ceramic composite was incorporated into Al5083 to produce a surface composite by friction stir processing (FSP), and the microstructure, hardness and wear properties of Al5083-WC-Al{sub 2}O{sub 3} surface composite were evaluated. Optical microscopy of FSPed samples showed grain refinement in the stir zone. The addition of WC-Al{sub 2}O{sub 3} particles as well as increase in FSP pass number had a considerable effect on grain refinement, and the grain size of Al5083 base metal of 36 µm reduced to 11 µm for Al5083-WC-Al{sub 2}O{sub 3} surface composite after four passes. The SEM observation of the surface composite revealed that the WC-Al{sub 2}O{sub 3} particles distributed homogenously in the matrix and by increasing the FSP passes, the initial agglomerates of mechanochemically synthesized WC-Al{sub 2}O{sub 3} powders could be fractured. Microhardness evaluation showed a substantial improvement by adding WC-Al{sub 2}O{sub 3} particles and increase in FSP pass number. The maximum microhardness value of 101 HV belonged to surface composite after four passes, while the microhardness of the base metal was 65 HV. Wear test results revealed enhanced tribological behavior with a similar trend of microhardness values. Scanning electron microscopy tests revealed both adhesive and abrasive wear mechanisms on the surface of the wear test specimens.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of Particle Characteristic Parameters on the Electrical Conductivity of TiB{sub 2}/Cu Composites: A Modified Model for Predicting Their Electrical Conductivity

High-strength and highly conductive copper matrix composites can not only maintain excellent electrical and thermal conductivity but also enhance the strength and hardness of materials, showing that composites have a bright future for development. Predictions of the effective electrical conductivity of copper matrix composites disagree with experimental data due to the dependence of the composites on several factors. Most prediction models simply consider the influence of the particle volume fraction on conductivity. In the present study, the influence of the volume fraction and the size of the TiB{sub 2} particle on the electrical conductivity of TiB{sub 2}/Cu composites are investigated. The obtained electrical conductivity results correlate with the volume fraction, size, and distribution of particles in a pure copper matrix. A modified model for predicting the electrical conductivity is proposed where the particle spacing parameters are introduced into the existing Maxwell model. The particle spacing parameter, as a fitting parameter, fits the experimental data of the copper matrix composites excellently.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Corrosion Protection of Cu Electrical Cable by W-Ni Composite Coatings Doped with TiO{sub 2} Nanoparticles: Influence of Pulse Currents

W-Ni-TiO{sub 2} nano-composite layers were electrodeposited on copper surface by both direct (DC) and pulse (PC) currents. The copper substrates are samples from the main electrical cable used for the Renault K-Z (the latest 100% electric vehicle). In order to investigate coating morphology, atomic force microscopy was used, while energy-dispersive x-ray analysis was applied to determine nano-composite composition. Based on surface morphology, the W-Ni-TiO{sub 2} (DC) alloy surface was covered by massive agglomerates, especially when the W-Ni-TiO{sub 2} (PC) nano-composite coating was more compact, thicker and exhibited smaller grain size. The coated surface revealed different contents such as 43.4 and 65.4% of W in DC and PC coatings, respectively, which are considered to be a novel composition of the W-Ni alloy. XRD studies revealed that the NiW{sub 2} phase only occurs in the W-Ni-TiO{sub 2} (PC) nano-composite alloy. Electrical and thermal conductivities, microhardness and porosity values are enhanced by the addition of TiO{sub 2} to the alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Wear and Corrosion Behavior of Graphene-Nanoplate-Reinforced Copper Matrix Composites Prepared Through Electrostatic Self-Assembly

Synthesis of graphene nanoplates (GNPs)/copper (Cu) composites is one of the key challenges in the uniform dispersion of GNPs in the Cu matrix because of their density difference. In this work, GNPs/Cu composites are synthesized through electrostatic self-assembly and spark plasma sintering. The GNPs are uniformly dispersed in the Cu matrix. The graphene protective films are formed in the composites to protect the Cu matrix. The antifriction performance of the GNPs/Cu composites is investigated using a ball-on-disk apparatus. The corrosion resistance of the GNPs/Cu composites is estimated using potentiodynamic polarization curves. Wear and corrosion mechanisms are analyzed through scanning electron microscopy with energy-dispersive spectroscopy. The antifriction performance and corrosion resistance of the composites can be significantly improved by adding GNPs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Mechanical Characterization of High-Temperature Carbon Fiber-Polyphenylene Sulfide Composites for Large Area Extrusion Deposition Additive Manufacturing

Additive manufacturing (AM) is evolving from rapid prototyping to production of structural components. The widespread application of AM demands a high level of mechanical performance from these components, and it is therefore essential to improve feedstock material in order to meet these mechanical expectations. However, compared to traditional manufacturing techniques, the mechanical properties of AM materials and their resulting components are not well understood. In this study, we investigated the processability, microstructure, and mechanical performance of twin-screw compounded short carbon fiber reinforced polyphenylene sulfide (PPS) pellets as a feedstock material for big area AM (BAAM). The performance of the AM components was compared to that of traditional processing methods, namely injection molding (IM) and extrusion-compression molding (ECM). It was found that the AM composites exhibited 118% lower tensile strength and 55% lower tensile modulus when compared to traditional injection molding composite specimens; however, AM composites exhibited comparable properties to ECM composites. This response was attributed to highly aligned fibers in IM and AM samples. However, the AM composites contained porosity (15.5% volume), which reduced their mechanical properties in comparison to ECM composites. Finally, the IM process showed the maximum amount of fiber attrition with minimum porosity (0.007% volume), while the ECM process exhibited the least fiber attrition with 4.3% volume porosity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Densification and oxidation behavior of spark plasma sintered Hafnium Diboride-Hafnium Carbide composite

This study reports on the sintering and oxidation behaviors of Hafnium Diboride (HfB 2 ) and Hafnium Carbide (HfC) based ultra-high temperature ceramic (UHTC) composites. Pure Hafnium Diboride, Hafnium Carbide, and HfB 2 -50 vol% HfC composite were consolidated using spark plasma sintering (SPS) without the use of sintering aids. HfB 2 -HfC composite displayed a high sintered density of 98% as compared to 87% density of pure HfB 2 . The increased density of the HfB 2 -HfC composite is attributed to the bimodal powder distribution, which allowed for the smaller HfC particle to occupy the voids between the larger HfB 2 particles resulting in improved packing efficiency. Moreover, the higher planar surface energy, for the (111) and the (200) planes for HfC, contributed to the smaller HfC particle being a significant driving force in the sintering process. Oxidation studies of each material were carried out by exposing them to a high-speed plasma jet in a temperature exceeding 2700 °C. The results of these studies show an improved oxidation resistance of HfB 2 -HfC composite by 54% and 70% over pure HfC and HfB 2 , respectively. The enhanced oxidation behavior is attributed to B 2 O 3 filling in the porosity between the HfO 2 scale and protecting the underlying material. This study provides a new alternative to improve the sinterability of UHTC diborides by introducing another UHTC (i.e., HfC) to form a fully dense composite without sintering aid and superior oxidation resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Enhanced ductility in in-layer glass-carbon fiber/epoxy hybrid composites produced via tailored fiber placement

Experimental mechanical property results of composite materials with hybrid reinforcements (commingled glass and carbon fibers) are detailed and compared with single-fiber composite properties. In-layer hybrid materials, with carbon and glass fiber tows laid side-by-side, were produced via tailored fiber placement (TFP) technology. Detailed experiments showed a phenomenon of “enhanced ductility” of carbon fiber in the hybrid composites of 12–24% relative to an all-carbon fiber composite and multiple stress–strain peaks were observed. Here, this enhanced ductility was hypothesized to be due to the glass fibers mitigating the shock waves arising from the initial failures of carbon fibers, and preventing the premature failure of the remaining carbon fibers. A novel way to engineer the stress–strain behavior of a hybrid composite to achieve a metal-like ductile response (plateau of stress–strain behavior, often termed “elastic–plastic deformation”) was demonstrated by carefully selecting the type and composition of carbon and glass fiber materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Economic competitiveness of pultruded fiber composites for wind turbine applications

Pultrusion manufacturing of fiber reinforced polymers has been shown to yield some of the highest mechanical properties for unidirectional composites, having a high degree of fiber alignment with consistent performance. Pultrusions offer a low-cost manufacturing approach for producing unidirectional composites with a constant cross-section and are used in many applications, including spar caps of wind turbine blades. However, as an intermediate processing step for wind blades, the additional cost of manufacturing pultrusions must be accompanied by sufficient increases in mechanical performance and system benefits. Wind turbine blades are manufactured using vacuum-assisted resin transfer molding with infused unidirectional fiberglass or carbon pultrusions for the spar cap. Infused fiberglass composites are among the most cost-effective structural materials available and replacing this material in the cost-driven wind industry has proven challenging, where infused fiberglass spar caps are still the predominant material system in use. To evaluate alternative material systems in a pultruded composite form, it is necessary to understand the costs for this additional manufacturing step which are shown to add 33%–55% on top of the material costs. A pultrusion cost model has been developed and used to quantify cost sensitivities to various processing parameters. The mechanical performance for pultruded composites is improved versus resin-infusion manufacturing with a 17% increase in design strength at a constant fiber volume fraction, but also enables higher achievable fiber volume fractions. The cost-specific mechanical performance is compared as a function of processing parameters for pultruded composites to identify the opportunities for alternative material and manufacturing approaches for wind turbine spar caps. Finally, four materials are compared in a representative wind turbine blade model to assess the performance of pultruded carbon fiber systems and pultruded fiberglass relative to infused fiberglass, where the pultruded systems produce lower weight blades with various cost distinctions.

42 ENGINEERING↗
DOE OSTI2023

Crashworthiness of recycled carbon fiber composite sinusoidal structures at dynamic rates

Fiber reinforced polymer composites are finding applications in the automotive space for structurally critical applications including crash management. The use of recycled carbon fiber reinforcement can greatly reduce carbon emissions. In this study, recycled carbon fiber composites were manufactured into a self-supporting geometry using three matrices: polyphenylene sulfide (PPS), acrylonitrile butadiene styrene (ABS), and a structural epoxy, and subsequently crushed between flat platens at dynamic rates ranging from 4.6 to 9.1 ms -1 at temperatures in a range of -40°C to 80°C. Load-displacement data was used to evaluate their specific energy absorption, crush efficiency, and steady-state crush stress. Further, the energy absorption of the ABS composites was strongly sensitive to temperature, while the PPS composites exhibited strong crush efficiency dependence with both rate and temperature. The epoxy composites exhibited stable crush behavior at dynamic crush rates but exhibited a dramatic reduction in crush efficiency relative to quasi-static tests. The results of this study indicate that recycled fiber composites can achieve very high energy absorption levels (50–80kJkg -1 at room temperature) that make them an excellent alternative to more expensive and less environmentally friendly continuous virgin fiber laminates.

42 ENGINEERING↗
DOE OSTI2019

Fluorescent detection of cholesterol using p-Sulfonatocalix[4]arene functionalized carbon nanotubes and thermally reduced graphite oxide composites

In the present study, carbon nanotube (CNT), thermally reduced graphite oxide (TRGO), and CNT-TRGO were functionalized with p-sulfonatocalix[4]arene (SC4) and then investigated for fluorescent detection of cholesterol in the presence of rhodamine 6G (R6G). All of the composite samples show effective quenching of R6G fluorescent intensity without cholesterol, but the fluorescence intensity significantly increases with the addition of cholesterol. The results indicate a strong interaction between SC4 composites and cholesterol rather than between the SC4 composites and R6G, increasing R6G fluorescence intensity in the presence of cholesterol due to the release of R6G from the SC4 composites. Formation of the complex, made of the SC4 composite plus the cholesterol, enables the detection of cholesterol in the wide range of cholesterol concentration up to 109 µM. The binding constant between SC4 and cholesterol has been calculated, indicating that the SC4 composites display the maximum binding constant of 1.9 × 10 4 M -1 with cholesterol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗