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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Investigation on the Influence of EVA Content on the Mechanical and Thermal Characteristics of Poly(lactic acid) Blends

Poly(lactic acid) (PLA) has gained considerable attention nowadays as a biocompatible polymer owing to its advantage of being prepared from renewable resources. PLA exhibits excellent tensile strength, fabricability, thermal plasticity and biocompatibility properties comparable to many petroleum based plastics. However, low heat distortion temperature, brittleness and slow crystallization rate limit the practical applications of PLA. In order to address these limitations, an attempt has been made in the current work to prepare binary blends of PLA with ethylene vinyl acetate (EVA) at different compositions via melt mixing technique. Systematic investigation on the mechanical properties, thermal degradation and crystallization behavior for PLA-EVA blends was carried out. The impact strength of binary blends of PLA–EVA was found to increase significantly by 176% for 15 wt% of EVA compared to virgin PLA. This is due to the strong interfacial adhesion among PLA and EVA resulting in brittle to ductile transition. Scanning electron microscopy analysis for impact fractured surfaces of binary blends of PLA implied the toughening effect of PLA by EVA. Thermogravimetry analysis results revealed that the activation energy of PLA–EVA blends decreased with increase in EVA content in the PLA matrix. While, differential scanning calorimetry results obtained for PLA–EVA blends revealed the improvement in crystallinity when compared with neat PLA. The effect of EVA on non-isothermal melt crystallization kinetics of PLA was also examined via DSC at various heating rates. Decreasing trend in the t{sub 1/2} values indicated the faster rate of crystallization mechanism after addition of EVA in the PLA matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The Effect of Carboxyl Group Content on Water Uptake Capacity and Tensile Properties of Functionalized Soy Protein-Based Superabsorbent Plastics

This manuscript studies the relation between macroscopic properties of the soy protein isolate (SPI)-based superabsorbent polymers (SAP) (e.g., water uptake capacity and tensile properties) and the extent of chemical modification conducted on the protein. The increase in the carboxyl group content, obtained from electrometric titrations, for acylated systems compared to native SPI brings with it an improvement in the protein hydrophilic character, as revealed by the determination of the water imbibing capacity. SEM images show that larger porous regions were developed in the acylated plastics. As for their mechanical properties, static tensile measurements indicated that acylated plastics with greater water uptake values display higher extensibility, compared to the reference sample. These natural-based SAP materials could be appropriate for applications in which maintaining the dimensional stability during service is not crucial (e.g. in agriculture and horticulture).

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of MCC Content on the Structure and Performance of PLA/MCC Biocomposites

Green composites of polylactic acid (PLA) with microcrystalline cellulose (MCC) as reinforcement of the polymer matrix were produced by melt blending to improve the brittleness of PLA. The MCC was prepared by hydrolysis of wheat straw cellulose with sulfuric acid to remove amorphous area. The biocomposites were prepared with different MCC contents (2, 4, 6, 8 wt%). Scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, differential scanning calorimetry, Fourier transform infrared and mechanical testing were used to study the structure and properties of MCC and biocomposites. The tensile modulus and the strength of PLA/MCC biocomposites increased from 206 to 262 MPa and from 67.35 to 73.01 MPa, respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Small Fe Content on the Structure, Magnetic and Magnetocaloric Properties of SmNi{sub 3−x}Fe{sub x} (x = 0; 0.3 and 0.8) Intermetallic Compounds

The SmNi{sub 3−x}Fe{sub x} (x = 0; 0.3 and 0.8) were synthesized by arc melting and annealed at 1073 K for 1 week. The Rietveld refinement showed that these compounds crystallize in the PuNi{sub 3}-type structure (R3̄m-Space group) and the substitution of nickel by iron leads to an increase of the unit cell volume. The Curie temperature (T{sub C}) of the SmNi{sub 3−x}Fe{sub x} (x = 0; 0.3 and 0.8) samples increases from 60 K for SmNi{sub 3} to 230 K for SmNi{sub 2.2}Fe{sub 0.8}, the enhancement of T{sub C} is ruled by electronic and magnetovolumic effects. All the samples exhibit a second-order magnetic phase transition at Curie temperature T{sub C}. The magnetic entropy change ΔS{sub M} was estimated from isothermal magnetization curves and it decreases with the increase of Fe content from 2.3 J/kg.K (x = 0) to 0.6 J/kg.K (x = 0.8) at 50 kOe. The critical properties of SmNi{sub 2.7}Fe{sub 0.3} (as an example) intermetallic compound at the ferromagnetic-paramagnetic (FM-PM) transition have been analyzed. The estimated critical exponents derived from the magnetic data using various methods such as modified Arrott plot, Kouvel-Fisher method and critical magnetization isotherms M(T{sub C}, H). The critical exponent values for the material are in a close agreement with those predicted for the mean-field theory. The reason for this behavior may be long-range interactions between spins in this system.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Structural, Magnetic, and Magnetoelastic Properties of High Nd-Content Laves Alloys Prepared by Solid-State Synthesis

The magnetostrictive alloys with composition Tb{sub 0.4}Nd{sub 0.6}(Fe{sub 0.8}Co{sub 0.2}){sub x} (1.50 ≤ × ≤ 1.90) are synthesized using the solid-state mechanical alloying (MA) method followed by sintering. The phase component, structure, thermal stability, and magnetoelastic properties are investigated as functions of composition, milling process, and annealing temperature. An amorphous phase companied by free alpha-iron is formed by MA in a high-energy ball mill, which crystallizes into MgCu{sub 2}-type and PuNi{sub 3}-type structures with different annealing temperatures. A single Laves phase for the high Nd-content Tb{sub 0.4}Nd{sub 0.6}(Fe{sub 0.8}Co{sub 0.2}){sub 1.60} is formed at optimal conditions for heat treating at 700 °C for 30 min. A large linear anisotropic magnetostriction λ{sub a} (=λ{sub ||}–λ{sub ⊥}) as high as 560 ppm at 12 kOe is obtained for the sintered alloy, which may make it a promising magnetostrictive material. Meanwhile, this work may help to open up a new way to search for Laves phase magnetostrictive materials containing Nd.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Design of XPM based all optical contention detection circuit at 120 Gbps

This paper presents the design approach of all optical contention detection circuit based on the cross phase modulation interaction between two copropagating signal inside highly nonlinear fiber at the data rate of 120 Gbps. The error free operation has been achieved with the optimized signal power, length and effective area of optical fiber.

42 ENGINEERING↗
DOE OSTI2018

MC Carbide Characterization in High Refractory Content Powder-Processed Ni-Based Superalloys

Carbide precipitates in Ni-based superalloys are considered to be desirable phases that can contribute to improving high-temperature properties as well as aid in microstructural refinement of the material; however, they can also serve as crack initiation sites during fatigue. To date, most of the knowledge pertaining to carbide formation has originated from assessments of cast and wrought Ni-based superalloys. As powder-processed Ni-based superalloys are becoming increasingly widespread, understanding the different mechanisms by which they form becomes increasingly important. Detailed characterization of MC carbides present in two experimental high Nb-content powder-processed Ni-based superalloys revealed that Hf additions affect the resultant carbide morphologies. This morphology difference was attributed to a higher magnitude of elastic strain energy along the interface associated with Hf being soluble in the MC carbide lattice. The composition of the MC carbides was studied through atom probe tomography and consisted of a complex carbonitride core, which was rich in Nb and with slight Hf segregation, surrounded by an Nb carbide shell. The characterization results of the segregation behavior of Hf in the MC carbides and the subsequent influence on their morphology were compared to density functional theory calculations and found to be in good agreement, suggesting that computational modeling can successfully be used to tailor carbide features.

Materials Science↗
DOE OSTI2018

Effects of the Cr{sub 2}O{sub 3} Content on the Viscosity of CaO-SiO{sub 2}-10 Pct Al{sub 2}O{sub 3}-Cr{sub 2}O{sub 3} Quaternary Slag

The present study experimentally investigates the effect of Cr{sub 2}O{sub 3} on the viscosity of molten slags. The viscosities of CaO-SiO{sub 2}-10 pct Al{sub 2}O{sub 3}-Cr{sub 2}O{sub 3} quaternary slags with two different binary basicities (R, basic slag with R = 1.2 and acidic slag with R = 0.8) were measured by the rotating cylindrical method from 1813 K to 1953 K (1540 °C to 1680 °C). The results showed that the viscosity of both types of slag decreased as the Cr{sub 2}O{sub 3} content increased, but the viscosity of acidic slags exhibited a greater decrease. The slags showed good Newtonian behavior at such high temperatures. Cr{sub 2}O{sub 3} could act as a network modifier to simplify the Si-O-Si tetrahedral structure, as verified by the Raman spectral analysis, which was consistent with the decreasing trend of viscosity. The activation energy of viscous flow decreased slightly with increasing Cr{sub 2}O{sub 3}, but increasing the basicity seemed to be more effective in decreasing the viscosity than adding Cr{sub 2}O{sub 3}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Thermodynamic Study on MgO Solubility in High-Alumina-Content Slag System

In the current study, the MgO solubility in molten slag was measured to clarify the effect of basicity and Al{sub 2}O{sub 3} content on the MgO solubility equilibrating with the spinel solid phase in the CaO-SiO{sub 2}-Al{sub 2}O{sub 3} system. The MgO solubility decreased with the increasing basicity of the slag. However, the MgO solubility in the spinel equilibrium region exhibited different dependence when compared with the basicity dependence in the MgO equilibrium region. The aforementioned experimental results were quantitatively analyzed using magic-angle spinning (MAS) {sup 27}Al nuclear magnetic resonance (NMR) spectroscopy, in which the fraction of Al ions in the slag of spinel equilibrium region was changed to 4, 5, and 6. In addition, the analysis of the degree of Al avoidance modeling indicated that the change in bridging oxygen (BO) linkage species (distinguished into Al-O-Al, Si-O-Si, and Al-O-Si) was based on the Al/Si ratio change. The aforementioned change in BO linkage species led to a change in the MgO solubility with the stability of the alumina. Thus, the spinel equilibrium dissolution mechanism is discussed in detail in terms of the thermodynamic and structural influence in molten slag.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Tuning Weld Metal Mechanical Responses via Welding Flux Optimization of TiO{sub 2} Content: Application into EH36 Shipbuilding Steel

A series of TiO{sub 2}-containing basic-fluoride-type agglomerated fluxes was applied to join EH36 shipbuilding steel under high heat input SAW. The effects of TiO{sub 2} content on composition, microstructure features, inclusions characteristics, and mechanical properties of ensuing weld metals (WMs) were systematically investigated. 6 wt pct TiO{sub 2} leads to the most optimal mechanical properties. Such behaviors were elucidated via transfer of alloying elements, which enables a good combination of acicular ferrites (AFs) and accompanying microstructures.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Deposition Pressure, Nitrogen Content and Substrate Temperature on Optical and Mechanical Behavior of Nanocomposite Al-Si-N Hard Coatings for Solar Thermal Applications

Hard and optically transparent nanocomposite Al-Si-N thin films were deposited using DC magnetron sputtering at different process parameters. There was a significant effect of these parameters on the film properties affecting its mechanical and optical behavior. The nitrogen content or pressure, deposition pressure and substrate temperature strongly influence the phase formation which governs the hardness and optical transparency of the coating. Hardness was measured between 18 and 30 GPa. The band gap could be varied in the range of 3.8-4.2 eV by varying nitrogen pressures in the chamber during deposition. The films showed (0-80)% transparency in UV and visible region depending on the sputtering conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The Effect of Boron Content on Wetting Kinetics in Si-B Alloy/h-BN System

In this work, the effect of boron content on the high-temperature wetting behavior in the Si-B alloy/h-BN systems was experimentally examined. For this reason, hypoeutectic, eutectic and hypereutectic Si-B alloys (Si-1B, Si-3.2B and Si-5.7B wt.%, respectively) were produced by electric arc melting method and then subjected to sessile drop/contact heating experiments with polycrystalline h-BN substrates, at temperatures up to 1750 °C. Similar to pure Si/h-BN system, wetting kinetics curves calculated on a basis of in situ recorded drop/substrate images point toward non-wetting behavior of all selected Si-B alloy/h-BN couples. The highest contact angle values of ~ 150° were obtained for hypoeutectic and eutectic Si-B alloys in the whole examined temperature range.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of MWCNT Content on the Structure and Properties of Spark Plasma-Sintered Iron-MWCNT Composites Synthesized by High-Energy Ball Milling

The effect of multiwall carbon nanotube (MWCNT) content on the physical and mechanical properties of Fe-MWCNT composites has been studied. High-energy ball milling (HEBM) is employed to produce the composite powder; following this, spark plasma sintering (SPS) process has been adopted for powder consolidation. The composite powder and the sintered products were subjected to structural characterization by XRD. Microstructural studies were carried out by optical, field-emission scanning and high-resolution transmission electron microscopy. While Fourier transform infrared spectroscopic study of composites was done to understand the bonding characteristics, Raman spectroscopy was employed to assess the structural damage of MWCNT after HEBM. The effects of processing on the behavior of C-C, C-O and Fe-O bonds are studied by x-ray photoelectron spectroscopy. Microhardness and compressive strength of composites are also determined. Finally, magnetic and electrical properties of the composites were characterized. It was observed that optimized ball milling conditions help to preserve the structural identity of MWCNT. Consolidation by SPS insured good interfacial bonding. The microhardness and compression strength are significantly improved in MWCNT-reinforced iron matrix composite. MWCNT has appreciably improved the electrical conductivity of the composites. Tethering of MWCNT by iron oxide has led to appreciable improvement in saturation magnetization till 3 wt.% MWCNT.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Cobalt Content on Thermal, Mechanical, and Microstructural Properties of Al{sub 0.4}FeCrNiCo{sub x} (x = 0, 0.25, 0.5, 1.0 mol) High-Entropy Alloys

Al{sub 0.4}FeCrNiCo{sub x} (x = 0, 0.25, 0.5, 1.0 mol) high-entropy alloys are developed by arc melting route to investigate the effect of cobalt content on thermal, mechanical, and microstructural properties. The phase, microstructure, and chemical composition are analyzed using x-ray diffraction, transmission electron microscope, and scanning electron microscope with attached energy-dispersive x-ray spectrometer. The obtained results have shown that the Al{sub 0.4}FeCrNiCo{sub x} (x = 0-0.5 mol) high-entropy alloys form a simple FCC + BCC-type solid solution and Al{sub 0.4}FeCrNiCo{sub x=1} HEA forms a single-phase FCC structure. The compressive yield strength, microhardness, and thermal conductivity are observed to decrease from 965.22 to 233.37 MPa, 253.6 to 155.6 HV, and from 4.87 to 2.674 W/mK, respectively, whereas the electrical resistivity is observed to increase from 150.30 to 273.74 µΩ-cm with the addition of cobalt from x = 0-1 mol. Differential scanning calorimetry analysis has indicated that the Al{sub 0.4}FeCrNiCo{sub x} (x = 0, 0.25, 0.5, 1.0 mol) high-entropy alloys are thermally stable up to 1000 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Nb Content on Microstructures and Mechanical Properties of Ti-xNb-2Fe Alloys

β-Type Ti-Nb-based alloys exhibit satisfactory biocompatibility and low Young’s modulus for biomedical applications. The microstructure and mechanical properties of a series of Ti-(14, 16, 18, 20, 22, 24)Nb-2Fe alloys fabricated by arc melting were investigated by XRD, optical microscopy, and tensile tests. Both ω and α″ phases existed in the Ti-14Nb-2Fe alloy, while just a single β phase existed in the other alloys. Twinning is an important deformation mechanism that causes work hardening and twinning-induced plasticity. It was found in the Ti-(14, 16, 18, 20)Nb-2Fe alloys and not in the Ti-22Nb-2Fe alloy. The Ti-14Nb-2Fe alloy exhibited the highest tensile strength and the highest Young’s modulus owing to the existence of the ω phase. The tensile strength decreased gradually from 830 MPa (highest) for the Ti-14Nb-2Fe alloy to 540 MPa (lowest) for the Ti-24Nb-2Fe alloy with an increase in the Nb content. The Young’s modulus decreased from 90 GPa for the Ti-14Nb-2Fe alloy to 63 GPa for the Ti-22Nb-2Fe alloy and then increased to 71 GPa for the Ti-24Nb-2Fe alloy. Elongation shows the same trend as the Young’s modulus. The Ti-22Nb-2Fe alloy, with a low Young’s modulus of 63 GPa, tensile strength of 570 MPa, and 15% elongation, was found suitable for biomedical applications. The Ti-20Nb-2Fe alloy also exhibits a high tensile strength, a Young’s modulus ratio of 9.24 × 10{sup −3}, and 18% elongation and is thus considered another valuable Ti alloy for biomedical applications.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Molybdenum Content on Structure and Properties of a Co-Cr Biomedical Alloy

The present study aimed to develop several Co-Cr biomedical alloys with different amounts of molybdenum. The weight percentages of molybdenum were in the range of 0-4 wt.% in the base alloy (Co-30Cr). The microstructures, phases, density, mechanical strength, wear behavior and corrosion characteristics of these alloys were evaluated. The results showed that density, hardness and compressive strength increased by increase in Mo content in the alloy. In contrast, corrosion rate decreased when the Mo weight percentage was increased. Furthermore, addition of Mo up to 3 wt.% caused the volumetric wear loss to increase. However, 4 wt.% Mo in the alloy led to a reduction in the volumetric wear loss, even lower than that of Co-30Cr alloy without molybdenum. The variations of friction coefficient, however, were different under different operating conditions. Since no single alloy could merely satisfy all the desired characteristics, the entropy–analytic hierarchy process (AHP)–gray relational analysis (GRA) technique was utilized to select the best alloy among the examined materials. From the ranking order gained, it was indicated that M-4 (having 4 wt.% Mo) biomedical alloy possesses the best combination of all the properties.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Tensile Properties of a Cast Al-Si-Mg Alloy with Reduced Si Content and Cr Addition at High Temperature

Tensile properties of an Al-Si-Mg casting alloy with reduced Si content and Cr addition were investigated at room and high temperatures. It was found that the studied alloy exhibits a remarkable performance up to 200 °C, with comparable or slightly higher strength than typical values for Al-Si-Mg-Cu alloys, commonly used for high-temperature applications, and good elongation. This is due to the choice of proper heat treatment and to the formation of dispersoids containing Cr during heat treatment, which are stable at the considered temperatures, as demonstrated by scanning and transmission electron microscopy (STEM) analysis. Interestingly, exposure to 300 °C during tensile tests enhanced an additional formation of dispersoids. It is believed that heating the material in T6 condition led to such observed dispersoids formation since precursors were already present in the Al matrix. This is not sufficient to avoid material softening at 300 °C, but it represents an interesting point in order to develop alternative heat treatment routes for dispersion-strengthened Al alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Drier Climatic Conditions Increase Withanolide Content of Withania coagulans Enhancing Its Inhibitory Potential Against Human Prostate Cancer Cells

Prostate cancer is one of the major causes of cancer-related deaths in men and there is a growing interest in identifying natural compounds for its management. We analyzed bioactive withanolides in Withania coagulans from 11 different sites in Pakistan and evaluated the antiprostate cancer activities of leaf extracts from two sites with the greatest amounts. Total withanolide concentration differed by ~ 17-fold between sites, ranging from 1.01 ± 0.01 mg/g dry weight (mean ± SE) at Jand to 16.83 ± 0.02 mg/g at Mohmand Agency. Different tissues varied in their total withanolide content with roots having the least (0.42 ± 0.07 mg/g dry weight) and leaves the most (2.45 ± 0.45 mg/g). We found strong inverse correlations between site annual precipitation versus withanolide amounts in fruits (r = − 0.84, P = 0.001), leaves (r = − 0.88, P < 0.001), roots (r = − 0.91, P < 0.001), and total (r = − 0.89, P < 0.001), but not stems (r = − 0.20, P = 0.556). Extracts made from Mianwali and Mohmand Agency leaves possessed high anticancer activity in terms of increased induction of apoptosis and decreased cell viability, cell proliferation, invasion, and migration of different prostate cancer cell lines. These results are useful for the selection of withanolide-rich germplasm with potent anticancer properties.

60 APPLIED LIFE SCIENCES↗