Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ceramic processing”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Phase controlled synthesis of transition metal carbide nanocrystals by ultrafast flash Joule heating

Nanoscale carbides enhance ultra-strong ceramics and show activity as high-performance catalysts. Traditional lengthy carburization methods for carbide syntheses usually result in coked surface, large particle size, and uncontrolled phase. Here, a flash Joule heating process is developed for ultrafast synthesis of carbide nanocrystals within 1 s. Various interstitial transition metal carbides (TiC, ZrC, HfC, VC, NbC, TaC, Cr 2 C 3 , MoC, and W 2 C) and covalent carbides (B 4 C and SiC) are produced using low-cost precursors. By controlling pulse voltages, phase-pure molybdenum carbides including β-Mo 2 C and metastable α-MoC 1-x and η-MoC 1-x are selectively synthesized, demonstrating the excellent phase engineering ability of the flash Joule heating by broadly tunable energy input that can exceed 3000 K coupled with kinetically controlled ultrafast cooling (>10 4 K s –1 ). Theoretical calculation reveals carbon vacancies as the driving factor for topotactic transition of carbide phases. The phase-dependent hydrogen evolution capability of molybdenum carbides is investigated with β-Mo 2 C showing the best performance.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2015

Electrically tunable materials for microwave applications

Microwave devices based on tunable materials are of vigorous current interest. Typical applications include phase shifters, antenna beam steering, filters, voltage controlled oscillators, matching networks, and tunable power splitters. The objective of this review is to assist in the material selection process for various applications in the microwave regime considering response time, required level of tunability, operating temperature, and loss tangent. The performance of a variety of material types are compared, including ferroelectric ceramics, polymers, and liquid crystals. Particular attention is given to ferroelectric materials as they are the most promising candidates when response time, dielectric loss, and tunability are important. However, polymers and liquid crystals are emerging as potential candidates for a number of new applications, offering mechanical flexibility, lower weight, and lower tuning voltages.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Structural, electrical and electrochemical properties of Li{sub 4}Zr{sub x}Si{sub 1-x}O{sub 4} (0.02 ≤ x ≤ 0.06) ceramic electrolytes

The aim of this work was to investigate the structural, electrical and electrochemical properties of Li{sub 4}Zr{sub x}Si{sub 1-x}O{sub 4} (0.02 ≤ x ≤ 0.06) compounds prepared via sol gel method. The X-ray Diffraction results showed that all compounds can be indexed to monoclinic structure in space group P2{sub 1/m}. The Li{sub 4}Zr{sub 0.06}Si{sub 0.94}O{sub 4} compound showed highest bulk, grain boundary and total conductivity values of 1.19 × 10{sup −4} S cm{sup −1}, 4.75 × 10{sup −5} S cm{sup −1} and 3.41 × 10{sup −5} S cm{sup −1} respectively. The insertion of Zr{sup 4+} is found to enhance conductivity of the parent sample Li{sub 4}SiO{sub 4}. Linear sweep voltammetry results showed that Li{sub 4}Zr{sub 0.06}Si{sub 0.94}O{sub 4} ceramic electrolytes was electrochemically stable up to 5.07 V versus a Li{sup +}/Li{sup +} reference electrode.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Microstructural studies of nanocrystalline barium zirconium titanate (BZT) for piezoelectric applications

Lead-free piezoelectric ceramics based on barium titanate (BaTiO{sub 3}) with substitution of Zr{sup 4+} were prepared using sol-gel method. The Ba(Zr{sub x}Ti{sub 1-x})O{sub 3}, (BZT) powders with x = 0.0, 0.1, 0.2 and 0.3 were pressed into pellets and sintered at 1250 °C for 2 h. Focusing on the effect of Zr{sup 4+} substitutions into BaTiO{sub 3} perovskite system, the phase transition and microstructural properties of BZT ceramics were studied using XRD, SEM and EDX spectroscopy. All X-ray diffractograms were fitted using Pawley refinement model. The XRD diffractograms revealed the progressive phase transition from tetragonal to cubic phase as Zr content increased. The crystallite exhibited decreasing trend and was supported by shrinkage in grain size. The EDX analysis confirmed the successful substitution of Ti{sup 4+} with Zr{sup 4+} in BaTiO3 crystal.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Grain size effect on activation energy in spinel CoFe{sub 2}O{sub 4} ceramic

Cobalt ferrite of different average crystallites (from nanocrystallite to micro crystallites) has been prepared by the Sol-Gel Method. The X-ray diffraction (XRD) analysis confirms the cubic spinel phase with no trace of impurity phases. The effect of annealing temperature on micro structure and electric transport properties as a function of frequency and temperature has been studied. It is observed that the electric impedance and conductivity are strongly dependent on grain size. The impedance spectroscopic study is employed to understand the electrical transport properties of cobalt ferrite.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Development of Agile and Cost Effective Routes for Manufacturing Reliable Ceramic Components for SOFC Systems (Final Report)

Additive manufacturing routes were explored and developed to enable the low to medium volume manufacturing of ceramic components with a short lead time, flexibility for iterative design, and without the high CAPEX and tooling costs associated with green machining or injection molding. Agile manufacturing route of gelcasting and 3D printing were selected and work focused on the production of ceramic manifold components utilized in the balance of plant for Saint-Gobain’s all-ceramic SOFC stack. This work showed that both gelcasting and a specific version of 3D printing were able to create parts with the proper fidelity and at lower cost than traditional powder processing followed by green machining.

03 NATURAL GAS↗
DOE OSTI2019

Development of Agile and Cost Effective Routes for Manufacturing Reliable Ceramic Components for SOFC Systems (Final Scientific Report Updated)

Additive manufacturing routes were explored and developed to enable the low to medium volume manufacturing of ceramic components with a short lead time, flexibility for iterative design, and without the high CAPEX and tooling costs associated with green machining or injection molding. Agile manufacturing route of gelcasting and 3D printing were selected and work focused on the production of ceramic manifold components utilized in the balance of plant for Saint-Gobain’s all-ceramic SOFC stack. This work showed that both gelcasting and a specific version of 3D printing were able to create parts with the proper fidelity and at lower cost than traditional powder processing followed by green machining.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A demonstration of glass bonding using patterned nanocomposite thermites deposited from fluid

Ceramics and other nonmetals are widely used in industrial and research applications. Although these materials provide many advantages, they often pose unique challenges during bonding. This work aims to expand on current processes, which have much narrower applications, to nd a more universal method for nonmetal bonding. We utilize inks comprised of aluminum-based nanoenergetics, (a heat source) and tin (a bonding agent). Requirements for successful bonding are explored and four key criteria are established. Through statistical simulation and thermochemical equilibrium calculations, we conclude that the presence of a diluent in large percentages negatively impacts reaction kinetics. Conversely, we show small percentages of added tin enhance gas generation and drive faster reaction rates. The bulk bonding material, thermite plus tin, forms a continuous structure during reaction, adhering well to the substrate surface. In some cases, these bonds failed above 1200 kPa.

36 MATERIALS SCIENCE↗
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 OSTI2016

Computational Fluid Dynamics Simulation of a Pilot-Scale Waste Glass Melter

The INL has been developing a high-fidelity computational fluid dynamics (CFD) model of a Joule-heated ceramic-lined waste glass melter. The purpose is to better understand the dynamics of heat transfer within the system, in order to provide support for the optimization of the Hanford Waste Treatment Plant (WTP) that will be used for vitrification of legacy tank waste. The simulation presented here is for the DM1200 pilot-scale system, which has been operated by the Vitreous State Laboratory (VSL) over the past several decades. This system is about one-third of the scale of the full size WTP melter. Experimental data from this system is being used to validate computational simulations. The examination of the melter with a fully coupled CFD model should give an accurate assessment of the heat transfer into the reactive cold cap region. Heat is provided to the cold cap region from conduction and convection from the molten glass pool as well as radiation from the hot plenum above the cold cap. The CFD model implements a mathematical model of the cold cap developed for the assessment of the melting rate during the vitrification of tank waste. This sub-model implemented directly into the CFD model combines the mass and enthalpy balance of the cold cap together with the conversion kinetics of the feed. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Investigating ceramic breeder pebble beds thermomechanics evolution using novel pressure mapping technology

Ceramic breeder pebble beds undergo complex thermomechanical interactions during blanket operation due to stress build-up and relaxation under the effects of confined thermal expansion, thermal cycling, and creep. Understanding the evolution of such processes can aid in guiding blanket design/assembly, breeder materials developments, predicting performance and possible failure modes. This study introduces experimental techniques that enable us to create an environment in which the pebble bed stresses are organically generated as a result of relevant temperature gradients and magnitudes that allows us to observe the combined thermomechanical interaction effects. A novel non-intrusive in-situ tactile pressure sensing technology is used to generate real-time contact pressure maps revealing the spatial and temporal stress evolution with emphasis on understanding the roles that each of the thermo-mechanical forces play in dictating the pebble bed’s equilibrium conditions. Two types of bed-wall contact pressure drop were recorded: (1) within the subsequent cycles due to pebbles irreversible rearrangements, and (2) within the cycle itself as a result of creep/stress-relaxation. Consequently, by the fourth cycle, the contact pressure drops to negligible values and remains stable. This stability is attributed to two modes of self-regulation: (1) stress self-regulation as a result of pressure rise and fall due to thermal expansion and creep/thermal cycling, respectively, and (2) temperature self-regulation due to the locally enhanced thermal conductivity in the core region of the bed accompanied by deteriorated interface conductance. These two mechanisms are desirable as they lower the probability of the events of pebbles crushing and thermal runaways under high temperatures/stresses and poor heat extraction.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Green micromachining of ceramics using tungsten carbide micro-endmills

This paper presents an experimental analysis on micromachining of green-state silicon carbide (SiC) and aluminum nitride (AlN) using uncoated tungsten carbide (WC) micro-endmills. Although the unique properties of ceramics make them ideal materials for many applications involving micro-scale features, the industrial adaptation of ceramics at the micro-scale has been hindered due to the lack of viable ceramic micro-manufacturing techniques. Green micromachining (GMM), where micro-scale features are created by micromachining green-state ceramics that contain ceramic particles and a polymer binder, offers a potential solution for this problem by affording tremendous improvements in micromachinability with respect to sintered ceramics. After the completion of GMM, the green parts are debound and sintered to obtain the final component with the desired microscale features. In this work, we evaluated GMM characteristics of powder-injection molded green-state SiC and AlN to correlate process conditions and green-material compositions with the micromachining forces, quality, and tool wear. An experimental study that involves full immersion micromilling tests with 254 μm diameter micro-endmills at different cutting speeds and feed rates is conducted. For each of the two materials, two binder states (with and without wax) and two powder states (with micro particles only, or with both micro- and nanoparticles) are investigated. Green micromachining forces, specific energies and the resulting surface roughness are analyzed quantitatively. A qualitative analysis of burr formation and channel quality, as well as a preliminary study on micro-tool wear are also performed. Both the machining conditions and the material compositions are seen to have a strong effect on micro-machinability of green-state ceramics. Overall, we conclude that GMM can be a viable ceramic micro-manufacturing strategy if favorable (or optimal) micromachining and material parameters are identified through the presented (or a similar) micromachinability study.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Production of LEU fully ceramic microencapsulated fuel for irradiation testing

The Advanced Fuels Campaign of the US DOE Fuel Cycle Research/Development program is currently engaged in production of FCM fuel for irradiation testing in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL). FCM fuel production is a serial process with 3 major steps namely kernel, TRISO, and compact production. The first step in the kernel process is production of air-dried UO{sub 3} gel spheres with suspended carbon particles. These spheres, roughly 2 mm in size, are then calcined to produce a mixture of UO{sub 2} and carbon. This calcination step may be performed in either argon, hydrogen, or mixtures of these gases. Once the calcination step is complete, temperature is increased (>1400 Celsius degrees) to convert this mixture to UO{sub 2} + UC{sub x}. Once dense oxide-carbide kernels are available, the inert environment is switched to a nitrogen containing one to facilitate carbothermic reduction of kernels and production of UN. Essentially, the oxygen and carbon in the oxide-carbide kernels react with one another to produce CO and are replaced with nitrogen inside the lattice. The TRISO step in fuel production is incorporation of a porous carbon buffer layer, a dense inner pyrolytic carbon layer (IPyC), a SiC layer, and finally and outer pyrolytic carbon layer (OPyC) onto the UN kernels. The coating layer deposition step is carried out inside a graphite furnace using a fluidized bed chemical vapor deposition (CVD) process. In essence, a mixture of reactant and inert gasses flow from the bottom through a bed of particles that are in turn fluidized by the gas stream. The particles undergo CVD and once a different coating layer is to be incorporated, the furnace temperature is adjusted and the reactant gases are changed. The final step in the series of fuel production activities is the consolidation of UN TRISO particles inside the SiC matrix to produce cylindrical pellets. It entails 3 critical areas: SiC powder mixing, over-coating of particles, and high-temperature densification. Optimal execution of the powder mixing step is vital to achieve a fully dense SiC matrix at the end of the process. The SiC matrix is consolidated using a special form of liquid phase sintering (LPS) involving nano-powder feedstock that is designated as the NITE process. The SiC nano-powder slurry is sprayed directly onto the particle surface using a piezoelectric nozzle. Once the over-coated particles are available, final consolidation step at high temperatures (1875 Celsius degrees) is carried out.

36 MATERIALS SCIENCE↗
DOE OSTI2017

An Advanced Extreme-Environment Wireless Telemetry System for Turbine Blade Instrumentation

As advanced natural gas power generation systems evolve, the thrust for increased efficiencies and reduced emissions results in increasingly harsh conditions inside the turbine environment. These high temperatures, pressures, and corrosive atmospheres result in accelerated rates of degradation, leading to failure of turbine materials and components. Wolfspeed, A Cree Company, Siemens Energy, and Siemens Corporate Technology, in collaboration with the Department of Energy (DOE)'s National Energy Technology Laboratory, are developing a reliable and long-term monitoring capability in the turbine hot gas path in the form of novel ceramic-based thermocouples and wide bandgap instrumentation electronics that will contribute to the overall reliability of gas turbines. When equipped with better monitoring and controls, power plants can operate with increased fuel-burning efficiency, improved process dynamics and gas concentrations, and increased overall longevity of the power plant components. This will result in increased turbine availability and a reduction in outages and maintenance costs. The technology being developed in this program is based on advanced techniques and innovations in nearly every aspect of high-temperature electronics, including materials, semiconductor devices, subcomponents, electronic packaging, and system integration. The environment in which this wireless system must operate has continuous centrifugal loads with a gravitation force on the order of 16,000 times the force of gravity (16,000 g) and temperatures exceeding 400°C. This article will specifically discuss the background and motivation for the high-temperature instrumentation system and will explain the high-level electrical system, the construction of the instrumentation package, the techniques used for integration onto rotating components, as well as the wireless power and data transmission systems. In addition to the electrical and mechanical design, this article will also discuss results from laboratory bench testing as well as heated spin rig testing. Lastly, this article will highlight the future direction of the instrumentation system evolution, with a final objective of insertion into Siemens natural gas turbine power plants.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

A Model of Grain Boundary Complexion Transitions and Grain Growth in Yttria-Doped Alumina

In this work, we present a physically-parameterized microstructure evolution model for the Yttria-doped alumina system. Yttria-doped alumina is a well-known ceramic system which undergoes first-order phase-like transitions at grain boundaries, which can radically alter interface properties. The change in interfacial properties in turn can radically change microstructure outcomes during processing, including the induction of abnormal grain growth modes. In this work, we develop a simulation that evolves alumina microstructure as a function of yttria concentration and temperature. In the window studied, we achieve strong agreement with reviewed experimental results in identifying the windows for large grains, small grains, abnormal grain growth, and complexion transition kinetics. We then apply the model to study and demonstrate how the possible inclusion of second-phase particles or uneven solute distribution profiles will impact microstructure evolution. It is found that particles do not significantly affect abnormal grain growth in the window studied (but do lead to reduced grain size through pinning effects). It is found that even modest amounts of solute inhomogeneity will result in substantial changes in microstructure outcomes, frequently leading to clusters of abnormal grains. This model largely corroborates the expectations and hypotheses made from recent experimental studies in oxide-doped alumina systems. Further, it is found that there exists a peak transition fraction for the system at which abnormal grain size tends to be maximized.

Grain Growth, Grain Boundary Complexion, abnormal ↗
DOE OSTI2016

Additive manufacturing of hybrid circuits

There is a rising interest in developing functional electronics using additively manufactured components. Considerations in materials selection and pathways to forming hybrid circuits and devices must demonstrate useful electronic function; must enable integration; and must complement the complex shape, low cost, high volume, and high functionality of structural but generally electronically passive additively manufactured components. This article reviews several emerging technologies being used in industry and research/development to provide integration advantages of fabricating multilayer hybrid circuits or devices. First, we review a maskless, noncontact, direct write (DW) technology that excels in the deposition of metallic colloid inks for electrical interconnects. Second, we review a complementary technology, aerosol deposition (AD), which excels in the deposition of metallic and ceramic powder as consolidated, thick conformal coatings and is additionally patternable through masking. As a result, we show examples of hybrid circuits/devices integrated beyond 2-D planes, using combinations of DW or AD processes and conventional, established processes.

36 MATERIALS SCIENCE↗
DOE OSTI2019

An Advanced Extreme Environment Wireless Telemetry System for Turbine Blade Instrumentation

As advanced natural gas power generation systems evolve, the thrust for increased efficiencies and reduced emissions results in increasingly harsh conditions inside the turbine environment. These high temperatures, pressures, and corrosive atmospheres result in accelerated rates of degradation, leading to failure of turbine materials and components. The University of Arkansas (UA) and Siemens, in collaboration with the DoE's National Energy Technology Laboratory (NETL), are developing a reliable and long-term monitoring capability in the turbine hot gas path in the form of novel ceramic-based thermocouples and integrated wide band gap instrumentation electronics that will contribute to the overall reliability of gas turbines. When equipped with better monitoring and controls, power plants can operate with increased fuel-burning efficiency, improved process dynamics and gas concentrations, and increased overall longevity of the power plant components. This will result in increased turbine availability and a reduction in outages and maintenance costs. One of the key aspects to driving forward turbine monitoring capability is the development of high temperature capable integrated circuit (IC) electronics. Previous papers have described 500 °C + electronics that were developed primarily from a combination of discrete single transistors combined with supporting high temperature passive components. While these circuits have been tested successfully in high temperature spin test environments, the move to an IC approach will greatly increase the performance and reliability of turbine monitoring systems. This program is developing such capability through the implementation of silicon carbide (SiC) based ICs, and this paper details the initial approach and early testing of the developed devices. This research represents an important step towards the realization of a field deployable high reliability turbine condition monitoring system.

47 OTHER INSTRUMENTATION↗