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Results for “sintering preparation”

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 OSTI2023

Experimental and computational investigations on the SO 2 poisoning of (La 0.8 Sr 0.2 ) 0.95 MnO 3 cathode materials

To study the formation of detrimental phases under the sulfur gas impurity to the long-term degradation in the LSM cathode material, the classic cathode material, (La 0.8 Sr 0.2 ) 0.95 MnO 3 (LSM), was prepared, sintered, and annealed at 800, 900, and 1000°C in the sulfur-containing atmospheres, respectively. Through X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission electron microscopy (TEM) techniques, as well as the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) methodology, the secondary phases, especially the detrimental ones, under different conditions were predicted and experimentally verified correspondingly. Furthermore, sulfur poisoning results indicate that the accelerated tests might have degradation mechanisms different from actual operation conditions. More importantly, comprehensive comparisons among various impurity-containing conditions were also made to recommend better operation parameters.

36 MATERIALS SCIENCE↗
NASA NTRS2006

Pulsed Laser Deposition of BaCe(sub 0.85)Y(sub 0.15)0(sub 3) FILMS

Pulsed laser deposition has been used to grow nanostructured BaCe(sub 0.85)Y(sub 0.15)0(sub 3) films. The objective is to enhance protonic conduction by reduction of membrane thickness. Sintered samples and laser targets were prepared by sintering BaCe(sub 0.85)Y(sub 0.15)O(sub 3) powders derived by solid state synthesis. Films 2 to 6 m thick were deposited by KrF excimer laser on Si and porous Al2O3 substrates. Nanocrystalline films were fabricated at deposition temperatures of 600-800 C deg at O2 pressure of 30 mTorr and laser fluence of 1.2 J/cm square. Films were characterized by x-ray diffraction, scanning electron microscopy and electrical impedance spectroscopy. Dense single phase BaCe(sub 0.85)Y((sub 0.15) 0(sub 3) films with a columnar growth morphology is observed, preferred crystal growth was found to be dependent upon deposition temperature and substrate type. Electrical conductivity of bulk samples produced by solid state sintering and thin film samples were measured over a temperature range of 100 C deg to 900 C deg in moist argon. Electrical conduction of the fabricated films was 1 to 4 orders of magnitude lower than the sintered bulk samples. With respect to the film growth direction, activation energy for electrical conduction is 3 times higher in the perpendicular direction than the parallel direction.

Dynys, F. W.↗
NASA NTRS2006

Pulsed Laser Deposition of High Temperature Protonic Films

Pulsed laser deposition has been used to fabricate nanostructured BaCe(0.85)Y(0.15)O3- sigma) films. Protonic conduction of fabricated BaCe(0.85)Y(0.15)O(3-sigma) films was compared to sintered BaCe(0.85)Y(0.15)O(3-sigma). Sintered samples and laser targets were prepared by sintering BaCe(0.85)Y(0.15)O(3-sigma) powders derived by solid state synthesis. Films 1 to 8 micron thick were deposited by KrF excimer laser on porous Al2O3 substrates. Thin films were fabricated at deposition temperatures of 700 to 950 C at O2 pressures up to 200 mTorr using laser pulse energies of 0.45 - 0.95 J. Fabricated films were characterized by X-ray diffraction, electron microscopy and electrical impedance spectroscopy. Single phase BaCe(0.85)Y(0.15)O(3-sigma) films with a columnar growth morphology are observed with preferred crystal growth along the [100] or [001] direction. Results indicate [100] growth dependence upon laser pulse energy. Electrical conductivity of bulk samples produced by solid state sintering and thin film samples were measured over a temperature range of 100 C to 900 C. Electrical conduction behavior was dependent upon film deposition temperature. Maximum conductivity occurs at deposition temperature of 900 oC; the electrical conductivity exceeds the sintered specimen. All other deposited films exhibit a lower electrical conductivity than the sintered specimen. Activation energy for electrical conduction showed dependence upon deposition temperature, it varied

Dynys, Fred W.↗
NASA NTRS1983

Characteristics of Si3N4-SiO2-Ce2O3 compositions sintered in high-pressure nitrogen

Full-density Si3N4-SiO2-Ce2O3 compositions were prepared by sintering with 2.5 MPa nitrogen pressure at temperatures of 1900 and 2090 C. Room-temperature flexural strengths near 700 MPa for sintered material compared favorably with the strength of hot-pressed material. At 1370 C, where flexural strengths as high as 363 MPa were obtained, it was observed that the coarsest structure was the strongest and the finest structure was the weakest. One of the compositions tested, Si3N4-8.7 wt pct SiO2-8.3 wt pct-Ce2O3, was found to have excellent 200-h oxidation resistance at 700, 1000, and 1370 C, without incidence of 700 to 1000 C phase instability and cracking.

Sanders, W. A.↗
NASA NTRS1992

Fabrication Of Metal Chloride Cathodes By Sintering

Transition-metal chloride cathodes for use in high-temperature rechargeable sodium batteries prepared by sintering transition-metal powders mixed with sodium chloride. Need for difficult and dangerous chlorination process eliminated. Proportions of transition metal and sodium chloride in mixture adjusted to suit specific requirements. Cathodes integral to sodium/metal-chloride batteries, which have advantages over sodium/sulfur batteries including energy densities, increased safety, reduced material and thermal-management problems, and ease of operation and assembly. Being evaluated for supplying electrical power during peak demand and electric vehicles.

Bugga, Ratnakumar V.↗
DOE OSTI2023

Design, Fabrication, and Screening of Environmental‐Thermal Barrier Coatings Prepared by Ultrafast High‐Temperature Sintering

Abstract The demand for more efficient gas turbines relies heavily on the development of new environmental‐thermal barrier coatings (ETBCs). However, there is still uncertainty about which alloys and composites will be used for the next generation of turbine blades, as well as the most promising coating materials. Herein, an ETBCs development strategy is presented by integrating the coating design, synthesis, and screening using an ultrafast high temperature sintering (UHS) technique to accelerate coating improvements. The initial basis for composition selection is their thermal expansion mismatch with the substrate alloys; for which a temperature‐dependent coefficient of thermal expansion database is created. By combining tape casting method with the UHS technique a high‐throughput synthesis of single and multi‐layer coatings are realized with different compositions, layer stacking sequences, and layer thicknesses. To evaluate the coatings, thermal cycling tests from room temperature to 1300 °C are conducted. The approach enabled coatings on objects with complex geometries, multi‐layer ETBCs, and porosity tailoring by using staged UHS that runs with different temperatures and durations. The fast iteration strategy is more cost‐effective for the screening of ETBCs compared to conventional methods and greater throughput which can be further extended for rapid optimization of other materials systems.

Xie, Hua↗
DOE OSTI2023

Rational synthesis of high-performance Ni-rich layered oxide cathode enabled via probing solid-state lithiation evolution

Lithium (Li)-ion batteries using nickel (Ni)-rich layered oxide cathode have been pursued with interest due to high practical energy density. A fundamental understanding of the reaction pathways and structural evolution of the solid-phase synthesis of these materials is crucial for their rational design and process development for mass production. In this work, structural evolution during solid-state synthesis was traced via in situ technique, with a particular emphasis on the lithiation reaction and migration of transition metal (TM) ions. The sintering process is governed by the competitive relationship of decomposition and lithiation reactions, which can be regulated through temperature windows. Controlling the melting point of the Li sources, as well as their affinity to cathode precursors, is highly desired to maintain the layered ordering of TM ions throughout the whole synthesis process, which simplifies the manufacturing process and improves the quality of the manufactured cathode material.

25 ENERGY STORAGE↗
DOE OSTI2021

Processing and microstructure of ZrB 2 –SiC composite prepared by reactive spark plasma sintering

In-situ formation of ZrB 2 –SiC composites was investigated by reactive spark plasma sintering of precursor powders according to the reaction B4C + 2ZrC + 3Si → 3SiC + 2ZrB 2 . The reaction and process presented here involves a diffusion reaction between B4C and ZrC which facilitates the formation of ZrB 2 , while liquid phase sintering of silicon facilitates atomic diffusion and combines with free C from the B4C and ZrC reaction to form SiC within minutes of heating and there were some residual unreacted precursor materials. An interpenetrating matrix of ZrB 2 –SiC was formed that shows increased fracture toughness (6.03 ± 0.45 MPa m 1/2 ) despite relatively low density (95 %).

36 MATERIALS SCIENCE↗
DOE OSTI2025

Microscopic Characterization of Pb 10−x Cu x (PO 4 ) 6 O by 31 P and 63/65 Cu NMR Measurements

The report of the first room-temperature, ambient-pressure superconductivity in copper-doped lead apatite Pb 10−x Cu x (PO 4 ) 6 O has attracted lots of attention. However, subsequent studies revealed the presence of numerous impurity phases in the polycrystalline sample, and the sharp superconducting-like transition is not due to a superconducting transition but most likely due to a reduction in resistivity caused by the first-order structural phase transition of Cu 2 S at around 385 K from the β phase at high temperature to the γ phase at low temperature. Before now, only bulk measurements have been performed on a Pb 10−x Cu x (PO 4 ) 6 O powder sample, which could be affected by the impurity phases, masking the intrinsic properties of Pb 10−x Cu x (PO 4 ) 6 O. In this study, 31 P and 63/65 Cu nuclear magnetic resonance (NMR) measurements have been performed on a Pb 10−x Cu x (PO 4 ) 6 O powder sample to investigate its physical properties from a microscopic point of view. Our NMR data evidence the non-magnetic insulating nature of Pb 10−x Cu x (PO 4 ) 6 O without any trace of electron correlation effects. Furthermore, the 63/65 Cu NMR results suggest that no copper or very little copper is substituted for Pb in Pb 10 (PO 4 ) 6 O prepared by sintering Pb 2 SO 5 and Cu 3 P.

lead apatite↗
NASA NTRS1984

On Heat-Treatable Copper-Chromium Alloy, 1

A mother alloy of 10% Cr and 90% Cu was prepared by sintering. This was alloyed with the Cu melt and Cu-Cr alloys containing about 0.5% Cr was obtained. These alloys could be deformed easily in both the hot and cold states. By measuring the hardness change, age-hardening properties of cast alloys were studied, which were quenched from 950 deg and aged at 300 to 700 deg for 1 hour. The maximum hardness was obtained with the tempering temperature of 500 deg. For the temperature of solution-treatment, 950 deg was insufficient and that above 1000 deg necessary. For the tempering time, a treatment at 500 deg for 1 hr. or at 450 deg for 3 hrs. yielded the maximum hardness. As for the properties for electrical conductors, 3 kinds of wires (diam. 2 mm.) were made: (1) after cold-drawn to 2 mm., solution-treated, quenched, and then tempered (500 deg, 1 hr.); (2) after quenching, cold-drawn (75% reduction) to 2 mm. and tempered (500 deg, 1 hr.); and (3) after quenching, cold-drawn (81%) to intermediate diameter, tempered (500 deg, 1 hr.) and then cold-drawn (88%) again. Properties obtained for the 3 kinds, respectively, were as follows: conductivity 91, 90, and 86%. Tensile strength and strength for electrical conductivity are given.

Koda, S.↗
NASA NTRS1984

Model studies in catalysis with uhv-deposited metal particles and clusters

Small supported metal particles have become a popular area of intense research interest, and important contributions to the considered problems are being made from the fields of uhv technology, thin film physics surface science, and surface and thin film instrumentation. Attention is given to insulating supports, particulate metal deposits and their properties, metal/support interactions and gas exposures, and integrated experimental approaches. It is concluded that major contributions to the field of model catalysis should be forthcoming in the near future from uhv-based methods of research. Catalysis and catalysis-related problem areas expected to benefit from advanced model studies include catalyst preparation processing, sintering mechanisms for metals and alloys, separation of initial and final state effects for supported clusters, and the influence of particle and/or support morphologies.

Poppa, H.↗
NASA NTRS1986

A high-temperature heat sensitive element

This invention concerns the high-temperature heat sensitive element which is stable at high temperatures. A solid solution of the main component MgO-Al2O3-Cr2O3-Fe2O3 which contains spinel crystal structure is mixed with the secondary component ZrO2 at the mol ratio of 100 : 0.1 to 5.0 and sintered to prepare a high-temperature heat sensitive element.

Oguro, M.↗
NASA NTRS1989

Grinding Si3N4 Powder In Si3N4 Equipment

Three methods of grinding compared. Report based on study of grinding silicon nitride powder in preparation for sintering into solid ceramic material. Attrition, vibratory, and ball mills lined with reaction-bonded silicon nitride tested. Rates of reduction of particle sizes and changes in chemical compositions of powders measured so grinding efficiences and increases in impurity contents from wear of mills and media evaluated for each technique.

Herbell, Thomas P.↗
NASA NTRS1992

Development of electrostrictive ceramic motor actuators

Electrostriction, which exists in all materials, exhibits many potential applications in electronic and optically controlled systems. Few materials, however, possess electrostrictive effects large enough to be of practical usefulness. The development of materials with high electrostrictive coefficients has been a major impetus of much research in this area. The Pb(x)Ba(1 - x)(Zr(y)Ti(1 - y))O3 (PBZT) ceramic system appears to be a very promising candidate because of the electrostrictive coefficients, Q(sub 11) and Q(sub 12), are among the highest discovered today. In this paper, we describe the preparation and sintering of the PBZT(73/37) ceramic, and the effect of some sintering conditions on sintered samples. The results on the measurement of the electrostrictive and related properties are presented. In addition, a brief discussion of characteristics of PBZT ceramics is provided.

Gene H. Haertling↗
NASA NTRS2019

Effect of Processing on Morphology of Hydroxyapatites: Bioactive Glasses and Crystalline Composites

Recent studies on multinary oxides for applications as laser hosts and high dielectric capacitors have shown that processing at high temperature provides glassy or crystalline materials based on thermal treatments and cooling rates. Since hydroxyapatites are now subject of great interests due to their bioactivity, interest in producing soft and hard materials with glassy and crystalline nature by processing parameters has become very important. Crystalline materials by using Bridgman, Czochralski and flux growth methods are costly and require huge investment. We have observed that even low temperature solidification in organic flux produced oriented fibers. This organic treated material has different characteristics than in situ oxide materials prepared by sintering and grain growth. Examples of phosphate and silicate-based systems will be presented to demonstrate soft and hard materials. Effect of TiO2 and other hardening elements will be also reported.

McAdams, Joel↗