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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Material for solid state sintered material

A solid state sintered material is described that includes a mixed oxide of lanthanum, strontium, cobalt, iron and oxygen, and CaCO3 inclusions. The solid state sintered material can also include calcium oxide, which can form from thermal composition of calcium carbonate. The solid state sintered material can also include a pore-forming particulate material such as carbon black and/or a doped ceramic metal oxide ionic conductor such as Sm-doped ceria uniformly dispersed in the solid state sintered material. The solid state sintered material can be formed from a two-step process in which a portion of the CaCO3 is mixed with the mixed oxide materials and heated to form porous agglomerates, and the remaining CaCO3 is added during the formation of a sintering paste. The solid state sintered material described herein can be used as a cathode material for solid oxide fuel cell.

36 MATERIALS SCIENCE↗
DOE OSTI2025

High-throughput synthesis of high-entropy alloys via parallelized electric field assisted sintering

Materials discovery and design is an expensive and time-consuming process, though necessary to advance many engineering fields. In this work, a novel tooling design is utilized in conjunction with electric field assisted sintering (EFAS) to effectively create a new high-throughput synthesis technique: parallelized EFAS. Through this technique, a wide range of material compositions and geometries can be synthesized in parallel as isolated samples or as part of contiguous arrays. Multiple tooling designs are explored to examine both the flexibility and limitations of the technique. A series of increasing complex alloys is produced simultaneously using in situ alloying, beginning with pure Ni and adding equimolar constituents up to the septenary high-entropy alloy AlCoCrCuFeMnNi. Microstructural characterization reveals each sample is effectively fully dense and chemically homogenous while exhibiting phases in agreement with CALPHAD predictions. Scalability of parallelized EFAS is then experimentally demonstrated and the implications for materials discovery and automation are discussed.

36 - MATERIALS SCIENCE↗
DOE OSTI2020

Revealing the Structural Evolution and Phase Transformation of O3-Type NaNi 1/3 Fe 1/3 Mn 1/3 O 2 Cathode Material on Sintering and Cycling Processes

O-type layered oxide cathode materials can be easily synthesized for a full sodium stoichiometry with high specific capacity, but they all suffer from a capacity fade on cycling. The sintering process control and optimization are critical to ensure a high quality and consistency of the prepared cathode materials with stable structure. Herein, in situ high-energy X-ray diffraction (HEXRD) was first employed to investigate the phase evolution of the oxides during the sintering process of O3-type NaNi 1/3 Fe 1/3 Mn 1/3 O 2 . The in situ HEXRD and both operando Bragg coherent diffraction (BCXD) and coherent multicrystal diffraction (CMCD) were utilized to investigate the phase transformation of the cathode materials during the sodiation/desodiation process. A composite structure comprised of O-type and P-type oxides was formed after the initial electrochemical activation of the cathode material, resulting in good structural and electrochemical stability. This finding implies that strain engineering can be a new design philosophy for the development of next generation high-performance sodium ion cathodes.

25 ENERGY STORAGE↗
DOE OSTI2014

Effect of processing conditions on microstructural features in Mn–Si sintered steels

Sintering of steels containing oxidation sensitive elements is possible if such elements are alloyed with others which present lower affinity for oxygen. In this work, a master alloy powder containing Fe–Mn–Si–C, specifically designed to create a liquid phase during sintering, has been used for such purpose. The effect of processing conditions such as sintering temperature and atmosphere was studied with the aim of describing the microstructural evolution as well as the morphology and distribution of oxides in the sintered material, evaluating the potential detrimental effect of such oxides on mechanical properties. Chemical analyses, metallography and fractography studies combined with X-ray photoelectron spectroscopy analyses on the fracture surfaces were used to reveal the main mechanism of fracture and their correlation with the chemical composition of the different fracture surfaces. The results indicate that the main mechanism of failure in these steels is brittle fracture in the surrounding of the original master alloy particles due to degradation of grain boundaries by the presence of oxide inclusions. Mn–Si oxide inclusions were observed on intergranular decohesive facets. The use of reducing atmospheres and high sintering temperatures reduces the amount and size of such oxide inclusions. Besides, high heating and cooling rates reduce significantly the final oxygen content in the sintered material. A model for microstructure development and oxide evolution during different stages of sintering is proposed, considering the fact that when the master alloy melts, the liquid formed can dissolve some of the oxides as well as the surface of the surrounding iron base particles. - Highlights: • Oxide distribution in steels containing oxidation-sensitive elements • Mn, Si introduced in a master alloy powder, mixed with a base iron powder • Selective oxidation of Mn and Si on iron grain boundaries • Decohesive fracture caused by degradation of grain boundaries by oxide inclusions • Reducing agents efficient at low temperatures critical for avoiding oxide inclusions.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Synthesis and electrochemical performance of LiNi{sub 0.7}Co{sub 0.15}Mn{sub 0.15}O{sub 2} as gradient cathode material for lithium batteries

Highlights: ► The gradient precursors Ni{sub 0.7}Co{sub 0.15}Mn{sub 0.15}(OH){sub 2} is prepared by hydroxide co-precipitating. ► The cathode materials is synthesized by mixing the precursor with 5% excess LiOH·H{sub 2}O. ► The XRD results show that cathode materials present layered α-NaFeO{sub 2} typical crystal. ► Material sintered at 850 °C shows the best performance, with high-capacity and recyclability. -- Abstract: LiNi{sub 0.7}Co{sub 0.15}Mn{sub 0.15}O{sub 2} as a cathode material for lithium batteries was synthesized by mixing hydroxide co-precipitated precursors with 5% excess LiOH·H{sub 2}O. Its structural and electrochemical properties were investigated using X-ray diffractometry, scanning electron microscopy, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy. The results indicated that well-ordering layered LiNi{sub 0.7}Co{sub 0.15}Mn{sub 0.15}O{sub 2} cathode materials were successfully prepared in air at 750, 800, and 850°C with α-NaFeO{sub 2} typical crystal. The results of charge–discharge test demonstrated that the gradient cathode material sintered at 850 °C exhibited the best electrochemical performance with the initial discharge capacity of 164 mA h g{sup −1} at 0.2 C and lower electrochemical impedance. Nickel has low price. LiNiO{sub 2} cathode materials have high specific capacity, their theoretical capacity is 274 mA h g{sup −1} and with low self-discharge rate. So the Ni, Co, Mn ternary layer-structural compounds with high Ni content are showing to be promising cathode materials for lithium batteries. The techniques and research results in this paper are utilizable for the study of this kind of lithium battery materials.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Improved cladding nano-structured materials with self-repairing capabilities

When designing nuclear reactors or the materials that go into them, one of the key challenges is finding materials that can withstand an outrageously extreme environment. In addition to constant bombardment by radiation, reactor materials may be subjected to extremes in temperature, physical stress, and corrosive conditions. A limitation in fuel burnup is and usage of the nuclear fuel material is related to the structural material radiation damage, that makes the fuel be removed with low-burnup and immobilized in the waste storage pools. The advanced burnup brings cladding material embitterment due to radiation damage effects corroborated with corrosion effects makes the fuel pellet life shorter. The novel nano-clustered structured sintered material may mitigate simultaneously the radiation damage and corrosion effects driving to more robust structural materials that may make the nuclear reactor safer and more reliable. The development of nano-clustered sinter alloys provides new avenues for further examination of the role of grain boundaries and engineered material interfaces in self-healing of radiation-induced defects driving to the design of highly radiation-tolerant materials for the next generation of nuclear energy applications. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2019

Effect of Annealing on the Impact Resistance and Fracture Mechanism of PNC-60 Sinters After Cold Plastic Deformation

Compaction of sintered metal powders by free upsetting at room temperature dangerously reduces their plastic properties, particularly the fracture toughness. The reason for the occurrence of two unfavorable phenomena accompanying this deformation route is sought. The first phenomenon depends on the initial porosity of the preform and the amount of cold work resulting in the destruction of bonds and violation of continuity between sintered powder particles. The second phenomenon is the deformation of the metal matrix, which reduces the plasticity of the sintered product. To correctly assess the effect of changes occurring in the matrix as a result of deformation, it is necessary to use the properly defined sintered matrix hardening parameter discussed in this study. The adverse effects of cold forming can be eliminated by annealing the deformed sinters at a temperature below the sintering point and above the recrystallization temperature. The annealing temperature causes favorable changes in the structure and increases the impact resistance of the deformed sinters depending on the degree of deformation of the sintered matrix and the initial porosity of the preform. Annealing at a properly selected temperature restores the ductility of the metal matrix and improves the integrity of the sintered material impaired by the effect of deformation. Annealing also causes favorable changes in the porosity morphology, removing defects in the form of gaps and resulting in the spheroidization of voids. With an appropriately selected initial porosity and degree of deformation, subsequent annealing of sinters compacted by free cold upsetting provides products with strength properties comparable to sinters with the same density and subjected to single compaction and sintering but with considerably higher fracture toughness.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Rapid microwave synthesis of indium filled skutterudites: An energy efficient route to high performance thermoelectric materials

Graphical abstract: Filled skutterudites are promising thermoelectric materials. We report the microwave assisted synthesis of CoSb{sub 3} and In{sub 0.2}Co{sub 4}Sb{sub 12}. This method reduces the calcination time for skutterudite phase formation from 2 days to 2 min, thereby significantly reducing the time and energy needed to produce materials suitable for property and device testing. Highlights: Black-Right-Pointing-Pointer The microwave assisted solid state synthesis of CoSb{sub 3} and In{sub 0.2}Co{sub 4}Sb{sub 12} is reported. Black-Right-Pointing-Pointer This method allows the calcination time to be reduced from 2 days to 2 min. Black-Right-Pointing-Pointer Physical properties of microwave samples match those prepared conventionally. -- Abstract: Filled skutterudites are promising thermoelectric materials due to reduced thermal conductivity upon inserting a guest atom or 'rattler' into the CoSb{sub 3} structure. By using an indium rattler dimensionless Figure of Merit (ZT) values >1 at 650 K have been reported. The conventional synthesis of these compounds typically takes several days ({approx}3 days) to obtain the final well-sintered material for property measurements. We report here a microwave-assisted synthesis method that reduces the initial calcination time from 2 days to 2 min. This route significantly reduces the time needed to produce materials suitable for property and device testing.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Power Electronics Thermal Control (Presentation)

Thermal management plays an important part in the cost of electric drives in terms of power electronics packaging. Very promising results have been obtained by using microporous coatings and skived surfaces in conjunction with single-phase and two-phase flows. Sintered materials and thermoplastics with embedded fibers show significant promise as thermal interface materials, or TIMs. Appropriatecooling technologies depend on the power electronics package application and reliability.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2020

Ultra‐Uniform Nanocrystalline Materials via Two‐Step Sintering

Abstract Nanocrystalline materials with superior properties are of great interest. Much is discussed about obtaining nanograins, but little is known about maintaining grain‐size uniformity that is critical for reliability. An especially intriguing question is whether it is possible to achieve a size distribution narrower than what Hillert theoretically predicted for normal grain growth, a possibility suggested—for growth with a higher growth exponent—by the generalized mean‐field theory of Lifshitz, Slyozov, Wagner (LSW), and Hillert but never realized in practice. Following a rationally designed two‐step sintering route, it has been made possible in bulk materials by taking advantage of the large growth exponent in the intermediate sintering stage to form a uniform microstructure despite residual porosity, and freezing the grain growth thereafter while continuing densification to reach full density. The bulk dense Al 2 O 3 ceramic thus obtained has an average grain size of 34 nm and a size distribution much narrower than Hillert's prediction. Bulk Al 2 O 3 with a grain‐size distribution narrower than the particle‐size distribution of starting powders is also demonstrated, as are highly uniform bulk engineering metals (refractory Mo and W‐Re alloy) and complex functional ceramics (BaTiO 3 ‐based alloys with superior dielectric strength and energy capacity).

Dong, Yanhao↗
DOE OSTI2014

Synthesis of ZrO{sub 2} nanoparticles by hydrothermal treatment

Zirconium oxide (zirconia, ZrO{sub 2}) is the most common material used for electrolyte of solid oxide fuel cells (SOFCs). Zirconia has attracted attention for applications in optical coatings, buffer layers for growing superconductors, thermal-shield, corrosion resistant coatings, ionic conductors, and oxygen sensors, and for potential applications including transparent optical devices and electrochemical capacitor electrodes, fuel cells, catalysts, and advanced ceramics. In this work, zirconia particles were synthesized from ZrCl{sub 4} precursor with hydrothermal treatment in a batch reactor. Hydrothermal treatment may allow obtaining nanoparticles and sintered materials with controlled chemical and structural characteristics. Hydrothermal treatment was carried out at temperatures of 150 – 200°C with precursor concentration of 0.1 – 0.5 M. Zirconia particles obtained from this treatment were analyzed by using SEM, PSD and XRD to characterize the morphology, particle size distribution, and crystallinity, respectively. Based on the analysis, the size of zirconia particles were around 200 nm and it became smaller with decreasing precursor concentration. The increasing temperature caused the particles formed having uniform size. Zirconia particles formed by hydrothermal treatment were monoclinic, tetragonal and cubic crystal.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Chromium segregation at phase boundaries in Cr-doped WC-Co cemented carbides

Highlights: • Experimental evidence of a mixed (W,Cr) carbide layer on WC grain surfaces • Evidence of Cr segregation in the Co-rich binder phase in front of WC grain surfaces • Temperature dependent equilibrium segregation of Cr estimated from atom probe data • Experimental observations supported by predictions from thermodynamic modelling - Abstract: Atom probe tomography has shown (Cr,W)C to be present as a thin WC grain surface layer in an as-sintered Cr-doped WC-Co cemented carbide microstructure slowly cooled from the sintering temperature. The Co-rich binder phase contained a segregation of Cr in front of this surface layer. The mixed carbide layer was not observed when the as-sintered material had been heat treated at 1000 °C for 3000 s and then quickly cooled. A reduced amount of segregated Cr was, however, still present in the binder phase in front of the WC grain surface. These observations are supported by predictions from thermodynamic modelling; (Cr,W)C becomes stable at temperatures below 940 °C in the absence of other secondary carbides. The equilibrium segregation of Cr in the binder phase was estimated to 0.8 and 0.4 monolayer in the as-sintered and heat treated materials, respectively. The energy of segregation was calculated to 0.22 eV/Cr atom from the atom probe data. This value would result in a Cr segregation of 0.3 monolayer at the sintering temperature 1410 °C, provided that the energy of segregation in the Co-rich liquid phase sintering medium is the same as in the Co-rich binder phase. This Cr segregation may explain the WC grain growth inhibiting effect of Cr additions to WC-Co cemented carbide materials.

36 MATERIALS SCIENCE↗
DOE OSTI2010

DEVELOPMENT OF CERAMIC WASTE FORMS FOR AN ADVANCED NUCLEAR FUEL CYCLE

A series of ceramic waste forms were developed and characterized for the immobilization of a Cesium/Lanthanide (CS/LN) waste stream anticipated to result from nuclear fuel reprocessing. Simple raw materials, including Al{sub 2}O{sub 3} and TiO{sub 2} were combined with simulated waste components to produce multiphase ceramics containing hollandite-type phases, perovskites (particularly BaTiO{sub 3}), pyrochlores and other minor metal titanate phases. Three fabrication methodologies were used, including melting and crystallizing, pressing and sintering, and Spark Plasma Sintering (SPS), with the intent of studying phase evolution under various sintering conditions. X-Ray Diffraction (XRD) and Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM/EDS) results showed that the partitioning of the waste elements in the sintered materials was very similar, despite varying stoichiometry of the phases formed. Identification of excess Al{sub 2}O{sub 3} via XRD and SEM/EDS in the first series of compositions led to a Phase II study, with significantly reduced Al{sub 2}O{sub 3} concentrations and increased waste loadings. The Phase II compositions generally contained a reduced amount of unreacted Al{sub 2}O{sub 3} as identified by XRD. Chemical composition measurements showed no significant issues with meeting the target compositions. However, volatilization of Cs and Mo was identified, particularly during melting, since sintering of the pressed pellets and SPS were performed at lower temperatures. Partitioning of some of the waste components was difficult to determine via XRD. SEM/EDS mapping showed that those elements, which were generally present in small concentrations, were well distributed throughout the waste forms.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

SEM and TEM characterization of microstructure of stainless steel composites reinforced with TiB{sub 2}

Steel-8TiB{sub 2} composites were produced by two new sintering techniques, i.e. Spark Plasma Sintering (SPS) and High Pressure-High Temperature (HP-HT) sintering. This study discusses the impact of these sintering methods on the microstructure of steel composites reinforced with TiB{sub 2} particles. Scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS), X-ray diffraction, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used to analyze the microstructure evolution in steel matrix composites. The results of microscopic examinations revealed a close relationship between the composite microstructure and the methods and conditions of sintering. Substantial differences were observed in the grain size of materials sintered by HP-HT and SPS. It has been demonstrated that the composites sintered by HP-HT tend to form a chromium-iron-nickel phase in the steel matrix. In contrast, the microstructure of the composites sintered by SPS is characterized by the presence of complex borides and chromium-iron phase. - Highlights: •The steel-8TiB{sub 2} composites were fabricated by Spark Plasma Sintering (SPS) and High Pressure-High Temperature (HP-HT). •Sintering techniques has an important effect on changes in the microstructure of steel-8TiB{sub 2} composites. •New phases of different size and morphology were identified.

36 MATERIALS SCIENCE↗
DOE OSTI2010

PRELIMINARY STUDY OF CERAMICS FOR IMMOBILIZATION OF ADVANCED FUEL CYCLE REPROCESSING WASTES

The Savannah River National Laboratory (SRNL) developed a series of ceramic waste forms for the immobilization of Cesium/Lanthanide (CS/LN) and Cesium/Lanthanide/Transition Metal (CS/LN/TM) waste streams anticipated to result from nuclear fuel reprocessing. Simple raw materials, including Al{sub 2}O{sub 3}, CaO, and TiO{sub 2} were combined with simulated waste components to produce multiphase ceramics containing hollandite-type phases, perovskites (particularly BaTiO{sub 3}), pyrochlores, zirconolite, and other minor metal titanate phases. Identification of excess Al{sub 2}O{sub 3} via X-ray Diffraction (XRD) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) in the first series of compositions led to a Phase II study, with significantly reduced Al{sub 2}O{sub 3} concentrations and increased waste loadings. Three fabrication methodologies were used, including melting and crystallizing, pressing and sintering, and Spark Plasma Sintering (SPS), with the intent of studying phase evolution under various sintering conditions. XRD and SEM/EDS results showed that the partitioning of the waste elements in the sintered materials was very similar, despite varying stoichiometry of the phases formed. The Phase II compositions generally contained a reduced amount of unreacted Al{sub 2}O{sub 3} as identified by XRD, and had phase assemblages that were closer to the initial targets. Chemical composition measurements showed no significant issues with meeting the target compositions. However, volatilization of Cs and Mo was identified, particularly during melting, since sintering of the pressed pellets and SPS were performed at lower temperatures. Partitioning of some of the waste components was difficult to determine via XRD. SEM/EDS mapping showed that those elements, which were generally present in small concentrations, were well distributed throughout the waste forms. Initial studies of radiation damage tolerance using ion beam irradiation at Los Alamos National Laboratory (LANL) showed little if any modification of the material after irradiation. Additional study in this area is needed. Chemical durability was briefly studied using the Product Consistency Test (PCT). Most of the elements measured were retained by the ceramic waste forms, indicating good chemical durability. Cs, Mo, and Rb were released at somewhat higher rates as compared to the matrix components, although benchmark compositions and additional characterization are needed in order to qualify the PCT results.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Integrating fiber optic sensors into metallic components for sensing in harsh environments

The integration of fiber optic sensors into high-temperature materials is critical for real-time monitoring and autonomous operation of engineering systems. This study demonstrated a spark plasma sintering (SPS)-assisted embedding process for integrating sapphire fiber optic sensors into stainless steel components during part fabrication. Optical fibers were encapsulated in stainless steel 316L powders which were sintered at different fabrication conditions using SPS to investigate the effects of sintering parameters on the embedment. Measurements of optical transmittance, combined with microstructural analysis (X-ray computed tomography and scanning electron microscopy) and mechanical testing (tensile and microhardness), were conducted to examine the fiber functionality, fiber–matrix bonding quality, and properties of the sintered materials. Here, the results show that under suitable fabrication conditions, intact optical fibers can be encapsulated in highly-densified (>98 % relative density) stainless steel components. These conditions also led to a good bond at the fiber–matrix interface with micron-sized material interdiffusion across the interface. The sintering parameters were observed to affect fiber optical attenuation, where high temperature, pressure, and hold time during SPS enhanced fiber–matrix bonding and adversely affected optical transmission. Tensile testing confirmed the superior tensile strength and ductility of the matrix fabricated by SPS. Furthermore, the materials exhibited limited strength reduction (~70 MPa) upon the integration of fibers. This study demonstrates the effectiveness of SPS for fiber-material integration for high-temperature applications.

36 MATERIALS SCIENCE↗
DOE OSTI2025

High-temperature nanoindentation creep studies on castable and sintered nanostructured low-activation ferritic-martensitic alloys

In this article, we present the creep characteristics of two reduced activation ferritic-martensitic steels of identical starting compositions formed by different fabrication routes: a nanostructured ferritic alloy commonly referred to as a castable nanostructured alloy (CNA) and a sintered nanostructured alloy (SNA) variant. Through a series of nanoindentation experiments spanning a temperature range of 25 °C to 650 °C, with a maximum load of 100 mN, we find creep behaviors in the cast and sintered materials to be remarkably similar. The creep stress exponent (n) for CNA and SNA were found to be in the range of 8–35 and the activation volume was ∼14–42b 3 , underscoring a dominance of dislocation-mediated mechanisms in both alloys. Notably, we observed a decline in the creep stress exponent with increasing temperature, attributable to the heightened influence of thermally activated dislocations. This phenomenon suggests a potential transition in the deformation mechanism towards a thermally activated dislocation climb process, significantly impacting the observed creep behavior.

36 MATERIALS SCIENCE↗