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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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Superior Corrosion Resistance Properties of TiN-Based Coatings on Zircaloy Tubes in Supercritical Water

Thin films of TiN and Ti0.35Al0.65N nanocomposite were deposited on polished Zircaloy-4 tubes. After exposure to supercritical water for 48 h, the coated tubes are remarkably intact, while the bare uncoated tube shows severe oxidation and breakaway corrosion. X-ray diffraction patterns, secondary electron images, backscattered electron images, and energy dispersive X-ray spectroscopy data from the tube surfaces and cross-sections show that a protective oxide, formed on the film surface, effectively prevents further oxidation and corrosion to the Zircaloy-4 tubes. This result demonstrates the effectiveness of thin film ceramics as protective coatings under extreme environments.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Microstructure characterization of recycled IN718 powder and resulting laser clad material

Highlights: • A simple and efficient recycling procedure of IN718 powder has been defined for the laser cladding process. • Characterization of wasted and cleaned powder and comparison with new IN718 powder pointed out a slight diameter increase. • Microstructure characterization of clad builds showed differences between builds with new and recycled powders. • Clad microstructure and porosity increase remain constant static properties but decrease rupture strain after 3 reuses. • Without special precautions for cladding, the recycled powder can be reused twice without modifying the properties of IN718. - Abstract: The possibility to reuse the metal powder wasted in Laser Material Deposition (LMD) process has been evaluated and a simple procedure developed. LMD uses metal powder which is fed through a nozzle into the focal point of a laser, where it melts the powder and the substrate material. During the process, a high ratio of particles hits against an unmelted area and directly bounces off the deposited area. The efficiency ratio of deposition can drop to 40% depending on the configuration and spot size. This work deals with the design of a procedure to recollect and reuse the wasted powder of a nickel based superalloy IN718. After usage, powder is recollected, undesired fractions are magnetically segregated and aggregates are removed by sieving. The particles are mixed again and ready for reuse. In order to study the effectiveness of the process, no new powder has been added to the recovered fraction, and this procedure has been repeated five times. Experimental tests show that deposited material present similar properties than those obtained with new powder grains. But, after 3 reuses, the porosity content increases consequently and the rupture strain decreases strongly. The implementation of this process allows the improvement of the final efficiency, reducing costs and decreasing the hazardous powder amount.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Ni content on the microstructure and mechanical properties of weld metal with both-side submerged arc welding technique

Highlights: • This manuscript primarily studied the effects of Ni content on the K65 weld metals; • Increase Ni content could significantly improve the strength and low temperature impact toughness of the weld metal. • The beneficial effect of Ni is attributed to its positive effect on phase transformation. • GBF keeps K-S or N-W relations only with one austenite and the variants belong to the same bain group are two reasons. • The M/A islands are considered to be another reason for the reduced toughness. - Abstract: The effects of nickel (Ni) content on the mechanical properties and microstructure evolution in the weld metals of commercial K65 oil and gas pipeline steel were studied. Increase Ni content could significantly improve the strength and low temperature impact toughness (−40 °C and −60 °C) of the weld metal. The above influences of Ni were attributed to the formation of predominant acicular ferrite (AF), at the expense of grain boundary ferrite (GBF), ferrite side plates (FSP) and martensite/austenite (M/A) constituent in weld metal. EBSD results indicated that GBF keeps K-S or N-W relations only with the prior austensite grain that belongs to one side of the grain boundary and the variants belong to the same bain group which always forms low angle boundary. Moreover, the retained austenite as one part of M/A constituent was mainly found in the weld metal with lower Ni content. It indicated that the transformation process could be promoted more completely by the increase of Ni content. The mechanism of the toughness improvement brought by Ni increasing was ascribed to the relatively uniform transformation to final microstructure, which reduces the appearance of GBF and M/A constituents.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of strain level on the evolution of microstructure in a recently developed AD730 nickel based superalloy during hot forging

Highlights: • Hot forging of AD730 led to formation of large non-recrystallized grains. • Similarity in chemical compositions of the non-recrystallized zones and the matrix. • Increase in strain level promoted recrystallization. - Abstract: Design and control of microstructure of engineering parts made from nickel based superalloys with superior mechanical properties for high temperature applications, require the parts to be subjected to certain thermo-mechanical processing during forging. This often includes sequential straining and annealing at elevated temperatures followed by subsequent aging heat treatments at lower temperatures. In this study, the effect of strain magnitude on the evolution of microstructure during hot forging of a recently developed AD730 nickel based superalloy has been investigated. Microstructural heterogeneity was observed in a forged material manifested in a form of large non-recrystallized grains within the recrystallized matrix that is observed to be dependent on the level of deformation (i.e. strain magnitude). Analyses of microstructure indicated significant reduction in the fraction of low-angle grain boundaries and sub-structures with an increase in the applied strain, suggesting higher fraction of recrystallization with higher levels of strains. It was concluded that the lower strain levels were insufficient to provide enough driving force for complete recrystallization throughout the entire microstructure of the forged material.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Development of microstructure and texture during single and multiple pass friction stir processing of a strain hardenable aluminium alloy

Highlights: • Development of microstructure and texture during single and multiple pass FSP of a strain hardenable aluminium alloy • Strain induced boundary migration (SIBM) is the dominant nucleation mechanism for recrystallization • Weak crystallographic texture development influenced by SIBM with the relative dominance of shear texture components • Stable microstructure and texture development after multiple pass FSP • FSP is a promising method for the secondary processing of strain hardenable aluminium alloys - Abstract: In the present study, microstructure and texture development during single and multiple pass friction stir processing (FSP) of a strain hardenable wrought AlMg alloy (AA5086) was investigated. Subtle differences were observed while comparing with heat treatable alloys in the nucleation mechanism of the recrystallized microstructure observed in the nugget zone. Strain induced boundary migration was the dominant mechanism of microstructure evolution in the alloy, which influenced the crystallographic texture development by weakening it. Micro-texture measurements reveal variations in the crystallographic texture along the thickness of the sample. Recrystallization texture components were observed in the nugget zone indicative of a pronounced static recrystallization in the alloy as compared to the heat treatable alloys. Bulk texture measurements within the nugget zone of the optimally processed sample reveal a relatively dominant C component of shear texture. Average grain size in the nugget zone remained the same and the bulk crystallographic texture components were retained during multiple-pass FSP. The lower strain energies involved and the enhanced recovery processes due to the high temperature materials processing of the alloy during FSP resulted in a stable microstructure and texture. In summary, FSP could be promoted as a competent and suitable secondary processing technique for the bulk production of ultra-fine-grained materials in strain hardenable aluminium alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of build geometry on the microstructural development of 316L parts produced by additive manufacturing

Highlights: • Stainless steel ribs were created via direct metal laser sintering to investigate microstructural effect of part design. • EBSD confirmed the presence of large elongated grains in the center of the part, with preferred orientation. • Small grains at the rib surface were found to grow towards the center of the rib with random orientation. • By changing rib thickness and build angle varying texture was observed in the final products. • Large intragranular misorientations were observed in all samples. - Abstract: Additive manufacturing (AM) technology has shown great potential in manufacturing complex products, such as lattice structures without extensive tooling. The focus of this study was to understand the effect of the part geometry on the resulting microstructure. Direct metal laser sintering was used for fabrication of ribs with thicknesses varying between 0.2 and 3.0 mm as well as inclined ribs the with build angles of 30° and 45°. The investigation showed that grains were growing in an epitaxial manner parallel to the building direction. The large elongated grains had a preferential orientation, resulting from the temperature gradient. Additionally, it was found that small grains had formed close to the part surface which were inclined towards the center of the rib. In contrast to the elongated grains, they had a random orientations. The results also indicated that at build angles below 45°, the formed microstructure consisted of the large grains elongated in the building direction. For the used process parameters, the critical part thickness to avoid large elongated grains was found to be about 0.4 mm. These findings allowed us to establish the basics for design rules when it comes to thin wall structures.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of filling materials on the microstructure and properties of hybrid laser welded Al-Mg-Si alloys joints

Highlights: • A serious comparison was made on the hybrid laser welded AA6061-T6 joint with different filling materials. • The microstructure of the welded joint was characterized using EBSD and SEM. • A strength model was successfully built to predict the strength of the hybrid laser welded AA6061-t6 joint. • The study shed new insights on how to select appropriate filling materials when using hybrid laser welding. - Abstract: A serious investigation was conducted to examine the influence of filling materials on the microstructure and properties of hybrid laser welded AA6061-T6 joints. The results of the tensile tests showed that the welded joint with ER4043 filling materials had higher tensile strength than that with ER5356 filling material. Based on the results obtained a strength model was built to predict and explain the enhancement of the yield strength of the hybrid laser welded AA6061-T6 joint with different welding wires. In contrast to the tensile strength, the ER4043 joint showed lower fatigue strength than that of the ER5356 joint due to extensive presence of micropores in fusion zone. Further, the corrosion experiment illustrated that the ER4043 joint had poorer resistance to the corrosive attack under 3.5% NaCl solution. A summary was made on the performance of both welded joints to shed new insights on selecting appropriate filling materials when welding AA6061-T6 by hybrid laser welding method.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Densification, microstructure and properties of TiB2 ceramics fabricated by spark plasma sintering

Highlights: • Nearly full densification of in-house processed TiB{sub 2} ceramic powders at 1500 °C. • Microstructures revealing the size and shape of TiB{sub 2} grains after SPS. • The effect of sub-micron particles on the densification during SPS. • The effect of sintering pressure on the microstructure. • Microhardness and nano-indentation measurements along with oxidation studies. - Abstract: This study reports the fabrication of high-density TiB{sub 2} ceramics at reduced temperatures (1500 °C) by using field assisted sintering technology/spark plasma sintering (FAST/SPS) technique. In-house processed TiB{sub 2} powders with high purity were employed as starting materials. The effects of SPS conditions on the sintering behavior and microstructure of TiB{sub 2} were investigated. Sub-micron character of TiB{sub 2} particles has a strong influence on the densification during SPS. Microstructural analyses revealed that the high pressure affected both the grain size and the shape of TiB{sub 2} crystallites. Elongated grains with average size of 6 μm were perceived in TiB{sub 2} sample fabricated by SPS at 1500 °C under 60 MPa pressure with a relative density of 96.7%. The microhardness and elastic modulus were measured as 27.4 GPa and 685.2 GPa, respectively. This sample revealed an improved oxidation resistance due to the formation of a thin oxidation layer on the surface when heated up to 1200 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Thermo-mechanical processing window for β phase recrystallization inTi-5Al-5Mo-5V-3Cr alloy

Highlights: • A processing window has been developed to obtain fine uniform recrystallized grains. • High deformation (90%) with annealing at intermediate temperature (950 °C) suggested • Dynamic recrystallization (Drx) should be avoided. • DRx reduces driving force for static rx. It gives bimodal distribution of grains. • Final deformation step should be in the α + β phase field. Ti-5Al-5Mo-5V-3Cr (Ti-5553) is a high strength β titanium alloy. It is now commonly used in thick section aerospace components. In general, the thermo-mechanical processing (TMP) of β titanium alloys done at high temperature to obtain uniformly recrystallized fine grain structure is one of the major challenges. Through this work, a TMP window for Ti-5553 (through systematic variation in % reduction and post deformation annealing temperature) has been developed to obtain fine uniformly recrystallized β grains. Grain size has been quantified on EBSD generated orientation maps, by applying stereological methods, image processing and automated reconstruction. Effects of % deformation and post deformation annealing temperature, as well as that of initial ingot size prior to deformation and the capacity of the forge on the static and dynamic recrystallization behavior, which eventually determine the final grain size distribution, have been illustrated.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Orientation and morphology of Pt nanoparticles in γ-alumina processed via ion implantation and thermal annealing

Structure and chemistry of metal/metal-oxide interfaces are critical for many catalytic processes and sensing. Pristine interfaces of Pt and γ-Al 2 O 3 were fabricated using high-energy ion implantation and thermal processing. Amorphous regions of alumina develop in single crystal α-alumina during Pt+ implantation and an 800 °C thermal treatment crystalizes amorphized alumina to γ-Al 2 O 3 and allows Pt ions to precipitate within the developing γ-alumina, yielding Pt nanoparticle tetrahedra terminated by {111} surfaces. The phase of alumina that developed and the distribution, morphology, and orientation of Pt nanoparticles was determined using x-ray diffraction, Rutherford backscattering spectrometry, transmission electron microscopy and scanning transmission electron microscopy.

36 MATERIALS SCIENCE↗
NASA NTRS1971

Measurement of lattice damage caused by ion-implantation doping of semiconductors.

Discussion of two new techniques used to measure the lattice damage produced in GaAs by the implantation of 60 keV cadmium ions. In the first method, optical reflection spectra of the ion-implanted samples were measured in the wavelength range from 2000 to 4600 A. The decrease in reflectivity resulting from ion-implantation was used to determine the relative amount of lattice damage as a function of ion dose. The second technique employed the scanning electron microscope. Patterns very similar in appearance to Kikuchi electron diffraction patterns are obtained when the secondary and/or backscattered electron intensity is displayed as a function of the angle of incidence of the electron beam on a single crystal surface. The results of measurements made by both methods are compared with each other and with data obtained by the method of measuring lattice damage by Rutherford scattering of 1 MeV helium ions.

Hunsperger, R. G.↗
NASA NTRS1999

Surface Diagnostics in Tribology Technology and Advanced Coatings Development

This paper discusses the methodologies used for surface property measurement of thin films and coatings, lubricants, and materials in the field of tribology. Surface diagnostic techniques include scanning electron microscopy, transmission electron microscopy, atomic force microscopy, stylus profilometry, x-ray diffraction, electron diffraction, Raman spectroscopy, Rutherford backscattering, elastic recoil spectroscopy, and tribology examination. Each diagnostic technique provides specific measurement results in its own unique way. In due course it should be possible to coordinate the different pieces of information provided by these diagnostic techniques into a coherent self-consistent description of the surface properties. Examples are given on the nature and character of thin diamond films.

Miyoshi, Kazuhisa↗
NASA NTRS1999

Measurements and Diagnostics of Diamond Films and Coatings

The commercial potential of chemical-vapor-deposited (CVD) diamond films has been established and a number of applications have been identified through university, industry, and government research studies. This paper discusses the methodologies used for property measurement and diagnostic of CVD diamond films and coatings. Measurement and diagnostic techniques studied include scanning electron microscopy, transmission electron microscopy, atomic force microscopy, stylus profilometry, x-ray diffraction, electron diffraction, Raman spectroscopy, Rutherford backscattering, elastic recoil spectroscopy, and friction examination. Each measurement and diagnostic technique provides unique information. A combination of techniques can provide the technical information required to understand the quality and properties of CVD diamond films, which are important to their application in specific component systems and environments. In this study the combination of measurement and diagnostic techniques was successfully applied to correlate deposition parameters and resultant diamond film composition, crystallinity, grain size, surface roughness, and coefficient of friction.

Miyoshi, Kazuhisa↗
DOE OSTI2016

Microstructural Characterization of Irradiated Fuels and Materials for the United States High Performance Research Reactor Fuel Development Program and the Fuel Cycle Research and Development Program

In an effort to contribute to the development of advanced nuclear fuel for research reactors, monolithic and dispersion plate fuels will be examined to determine how irradiation parameters such as fission density, fission rate, and irradiation temperature, as well as mechanical parameters such as composition and fabrication, affect the final microstructure of the fuel, post irradiation. Electron Backscatter Detection (EBSD) analysis capabilities of irradiated materials will be developed as well as improvements on irradiated sample preparation in order to provide higher quality samples for SEM, FIB, and TEM. In addition, image analysis techniques developed at Idaho National Laboratory (INL) will be employed to examine microstructural features such as fission product precipitates and fission gas bubbles. The main goals are to further develop EBSD capabilities on irradiated material; characterize microstructure of irradiated fuel to support qualification; develop a consistent, effective process for image analysis using INL developed software; and provide repeatable, statistically-confident, critically assessed data to further modeling efforts. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2013

Microstructure and thermal oxidation behavior of yttria-stabilized hafnia nanostructured coatings deposited on alumina

Nanostructured yttria-stabilized hafnia (YSH) coatings were grown on α-Al2O3 substrates with variable coating thickness in a wide range of ~50 nm to 1 μm. Microstructure and thermal oxidation behavior of the grown YSH coatings were studied employing X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), scanning electron microscopy (SEM) and isothermal furnace oxidation testing. The effect of coating thickness on the crystal structure, surface/interface morphology and thermal oxidation was investigated. X-ray diffraction analyses revealed the formation of monoclinic phase for relatively thin coatings (b100 nm) indicating that the interfacial phenomena play a dominant role in phase stabilization. The evolution towards stabilized cubic phase with increasing coating thickness is observed. The SEM results indicate the dense, columnar structure of YSH coatings as a function of thickness. Thermal oxidation measurements indicate the enhanced hightemperature oxidation resistance of cubic YSH coatings.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructure and surface morphology of InAsSbBi grown by molecular beam epitaxy

The physical and chemical properties of 210 nm thick InAsSbBi layers grown by molecular beam epitaxy at temperatures between 400 and 430 °C on (100) GaSb substrates are investigated using Rutherford backscattering, X-ray diffraction, transmission electron microscopy, Nomarski optical microscopy, and atomic force microscopy. The results indicate that the layers are nearly lattice matched, coherently strained, and contain dilute Bi mole fractions. Large surface droplets with diameters on the order of 1 μm and densities on the order of 106 cm−2 are observed when the InAsSbBi growth is performed with lean As overpressures around 1%. Surface droplets are not observed when the As overpressure is increased to 4%. Small crystalline droplets with diameters on the order of 70 nm and densities on the order of 1010 cm−2 are observed between the large droplets for InAsSbBi grown at 430 °C. Analysis of one of the small droplets indicates a misoriented zinc blende crystal structure composed primarily of In, Sb, and Bi, with a lattice constant of 6.543 ± 0.038 Å. Lateral modulation in the Bi mole fraction is observed in InAsSbBi layers grown at 400 °C.

Kosireddy, R. R.↗
DOE OSTI2012

Nickel vacancy behavior in the electrical conductance of nonstoichiometric nickel oxide film

Nickel vacancy behavior in electrical conductance is systematically investigated using various analysis methods on nickel oxide films deposited at different oxygen partial pressures. The results of Rutherford backscattering, x-ray diffraction, and Auger electron spectroscopy analyses demonstrate that the sputtered nickel oxide films are nickel-deficient. Through the deconvolution of Ni2p and O1s spectra in the x-ray photoelectron spectroscopy data, the number of Ni{sup 3+} ions is found to increase with the O{sub 2} ratio during the deposition. According to the vacancy model, nickel vacancies created from the non-stoichiometry are concluded to produce Ni{sup 3+} ions which lead to an increment of the conductivity of the nickel oxide films due to the increase of the hole concentration.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Sublattice-specific ordering of ZnO layers during the heteroepitaxial growth at different temperatures

The effect of the substrate temperature on the sublattice ordering in ZnO layers grown by reactive pulsed magnetron sputtering on sapphire has been investigated by different techniques. The improvement of the crystal quality and heteroepitaxial growth at relatively low temperatures (550 deg. C) is verified by x-ray diffraction, high-resolution transmission electron microscopy, Rutherford backscattering spectrometry in channeling mode (RBS/C), and Raman spectroscopy. Sublattice-resolved analysis by resonant RBS/C and Raman spectroscopy reveals that the progressive transition to the single crystal phase is accomplished in a faster way for Zn- than for O-sublattice. This behavior is attributed to the preferential annealing of defects in the Zn sublattice at low temperatures when compared to those of the O sublattice.

36 MATERIALS SCIENCE↗