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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 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Pressure Swing Absorption Device and Process for Separating CO 2 from Shifted Syngas and its Capture for Subsequent Storage

Using the ionic liquid (IL) 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]) as the absorbent on the shell side of a membrane module containing either a porous hydrophobized ceramic tubule or porous hydrophobized polyether ether ketone (PEEK) hollow fiber membranes, studies for CO 2 removal from hot simulated pre-combustion shifted syngas were carried out by a novel pressure swing membrane absorption (PSMAB) process. Helium was used as a surrogate for H 2 in a simulated shifted syngas with CO 2 around 40% (dry gas basis). In this cyclic separation process, the membrane module was used to achieve non-dispersive gas absorption from a high-pressure feed gas (689-1724 kPag; 100-250 psig) at temperatures between 25-100°C into a stationary absorbent liquid on the module shell side during a certain part of the cycle followed by among other cycle steps controlled desorption of the absorbed gases from the liquid in the rest of the cycle. Two product streams were obtained, one He-rich and the other CO 2 -rich. Addition of polyamidoamine (PAMAM) dendrimer of generation 0 to IL [bmim][DCA] improved the system performance at higher temperatures. The solubilities of CO 2 and He were determined in the ionic liquid with or without the dendrimer in solution as well as in the presence or absence of moisture; polyethylene glycol (PEG) 400 was also studied as a replacement for the IL. The solubility selectivity of the ionic liquid containing the dendrimer for CO 2 over helium was considerably larger than that for the pure ionic liquid. The solubility of CO 2 and CO 2 -He solubility selectivity of PEG 400 and a solution of the dendrimer in PEG 400 were higher than the corresponding ones in the IL, [bmim][DCA]. A mathematical model was developed to describe the PSMAB process; a numerical solution of the governing equations described successfully the observed performance of the PSMAB process for the pure ionic liquid-based system.

08 HYDROGEN↗
DOE OSTI2015

The influence of temperature induced phase transition on the energy storage density of anti-ferroelectric ceramics

Anti-ferroelectric (AFE) composite ceramics of (Pb{sub 0.858}Ba{sub 0.1}La{sub 0.02}Y{sub 0.008})(Zr{sub 0.65}Sn{sub 0.3}Ti{sub 0.05})O{sub 3}-(Pb{sub 0.97}La{sub 0.02})(Zr{sub 0.9}Sn{sub 0.05} Ti{sub 0.05})O{sub 3} (PBLYZST-PLZST) were fabricated by the conventional solid-state sintering process (CS), the glass-aided sintering (GAS), and the spark plasma sintering (SPS), respectively. The influence of the temperature induced phase transition on the phase structure, hysteresis loops, and energy storage properties of the composite ceramics were investigated in detail. The measured results of X-ray diffraction demonstrate that the composite ceramics exhibit the perovskite phases and small amounts of non-functional pyrochlore phases. Compared with the CS process, the GAS and SPS processes are proven more helpful to suppress the diffusion behaviors between the PBLYZST and PLZST phases according to the field emission scanning electron microscopy, thereby being able to improve the contribution of PBLYZST phase to the temperature stability of the orthogonal AFE phase. When the ambient temperature rises from 25 °C to 125 °C, CS and GAS samples have undergone a phase transition from orthorhombic AFE phase to tetragonal AFE phase, which results in a sharp decline in the energy storage density. However, the phase transition temperature of SPS samples is higher than 125 °C, and the energy storage density only slightly decreases due to the disorder of material microstructure caused by the high temperature. As a result, the SPS composite ceramics obtain a recoverable high energy storage density of 6.46 J/cm{sup 3} and the excellent temperature stability of the energy storage density of 1.16 × 10{sup −2} J/°C·cm{sup 3}, which is 1.29 × 10{sup −2} J/°C·cm{sup 3} lower than that of CS samples and about 0.43 times as that of GAS samples.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Reaction Current Heterogeneity at the Interface between a Lithium Electrode and Polymer/Ceramic Composite Electrolytes

Although lithium metal anodes are expected to increase the energy density of next-generation batteries, dendrite growth during charge remains a major bottleneck preventing widespread implementation. Composite solid electrolytes with ceramic particles embedded in a polymer matrix have the potential to prevent dendrites owing to the higher mechanical stiffness while also possessing the flexibility to maintain contact with the electrode. However, microscopically, the different mechanical and electrochemical properties of the polymer and ceramic domains can cause inhomogeneous charge transfer at the Li/electrolyte interface, which can lead to nonuniform Li deposition and propagation of dendrites. Here, we computationally examine the coupled electrochemical, transport, and mechanical processes at the interface to determine the propensity for dendrite formation and possible approaches to mitigate this issue. Predictions of two possible microstructures at the interface, namely, (i) where both the polymer and ceramic come in contact with Li metal and (ii) when only the polymer comes in contact with Li metal, suggest that the former has a greater tendency for nonuniform plating. In addition, predictions suggest that minimizing the interfacial resistance between polymers and ceramics and incorporating interlayers between the electrode and electrolyte help mitigate current heterogeneity. In conclusion, these predictions provide guidance for experimental approaches to prevent dendrites in composite electrolytes.

25 ENERGY STORAGE↗
NASA NTRS2004

Signal Processing Variables for Optimization of Flaw Detection in Composites Using Ultrasonic Guided Wave Scanning

This study analyzes the effect of signal processing variables on the ability of the ultrasonic guided wave scan method at NASA Glenn Research Center to distinguish various flaw conditions in ceramic matrix composites samples. In the ultrasonic guided wave scan method, several time- and frequency-domain parameters are calculated from the ultrasonic guided wave signal at each scan location to form images. The parameters include power spectral density, centroid mean time, total energy (zeroth moment), centroid frequency, and ultrasonic decay rate. A number of signal processing variables are available to the user when calculating these parameters. These signal processing variables include 1) the time portion of the time-domain waveform processed, 2) integration type for the properties requiring integrations, 3) bounded versus unbounded integrations, 4) power spectral density window type, 5) and the number of time segments chosen if using the short-time fourier transform to calculate ultrasonic decay rate. Flaw conditions examined included delamination, cracking, and density variation.

Roth, Don J.↗
DOE OSTI2021

Electronic Structure, Chemical Bonding and Electrocatalytic Activity of Novel Ba(Fe0.7Ta0.3)O3-d Compounds

Ba(Fe0.7Ta0.3)O3-d (BFTO) compounds were synthesized using conventional, high-temperature solid-state ceramic reaction method by varying the sintering temperature (Ts=1200-1350 °C). The crystal structure, electronic structure and electrocatalytic activity of BFTO compounds were evaluated. Processing temperature induced phase transformations and structural quality influences the electronic structure and electrocatalytic activity of BFTO compounds. At Ts=1200 oC, Ba(Fe0.7Ta0.3)O3-d stabilizes in mixed phase of orthorhombic + rhombohedral phase (Amm2 + R3m). With increasing Ts (=1250 oC), Ba(Fe0.7Ta0.3)O3-d ceramics stabilize in tetragonal + rhombohedral [P4mm + R3m] mixed phase with a variation in the quantity of respective phases. High-resolution X-ray photoelectron spectroscopy of constituent elements, namely, Ba 3d, Fe2p, Ta 4f and O 1s reveal the electronic structure changes due to changes in chemical environment resulted from structural transformation. The electrocatalytic activity of BFTO was evaluated towards hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Though all the samples demonstrated appreciable electrocatalytic properties, the best electrochemical catalytic activity was shown by BFTO samples sintered at 1350 °C. BFTO-1350 oC showed an onset potential of -0.690 V vs. RHE for HER and an onset potential of 0.73 V vs. RHE for ORR indicating its significant electrocatalytic performance. A general increase in activity with sintering temperature is potentially due to the improved structural quality of the BFTO ceramics. In addition to offering the fundamental insights into solid state materials based on doped BaTiO3 for electrocatalysis, the present work may contribute to the design and development of materials for high-temperature electrocatalytic converters.

Ba(Fe0.7Ta0.3)O3-d, Phase Transformation↗
NASA NTRSDate not supplied

Joining and Integration of Silicon Carbide-Based Ceramic Materials for Aerospace Applications: An Overview

In order to fully utilize silicon carbide-based ceramics and ceramic matrix composites (CMCs) for aerospace and ground based applications, advanced joining and integration technologies are critically needed for achieving large, complex shaped, and integrated components. Careful material selection of joining inter-layers needs to consider chemical and thermal compatibilities with the parent materials that are being joined. Also, optimization needs to be conducted to select the proper processing conditions for achieving robust joints that are well adhered, strong, uniform, crack free, and have minimal residual stresses. NASA GRC developed pressureless and pressure aided approaches for joining ceramics and CMCs include brazing, diffusion bonding, refractory eutectic phase joining, and Single-step Elevated Temperature (SET) Joining. For joining ceramics and CMCs to metals, several brazes have been utilized. Brazing approaches for joining ceramics and metals have also included tailored brazes with multiple interlayers and particle additions. An overview of the joining approaches will be provided. In addition, processing-microstructure-property relationships will be discussed.

Silicon carbide↗
DOE OSTI2020

LiAlO 2 /LiAl 5 O 8 Membranes Derived from Flame-Synthesized Nanopowders as a Potential Electrolyte and Coating Material for All-Solid-State Batteries

Recently, γ-LiAlO 2 has attracted considerable attention as a coating in Li-ion battery electrodes. However, its potential as a Li + ceramic electrolyte is limited due to its poor ionic conductivity (<10 –10 S cm –1 ). Here, we demonstrate an effective method of processing LiAlO 2 membranes (<50 μm) using nanopowders (NPs) produced via liquid-feed flame spray pyrolysis (LF-FSP). Here, membranes consisting of selected mixtures of lithium aluminate polymorphs and Li contents were processed by conventional tape casting of NPs followed by thermocompression of the green films (100 °C/10 kpsi/10 min). The sintered green films (1100 °C/2 h/air) present a mixture of LiAlO 2 (~72 wt %) and LiAl 5 O 8 (~27 wt %) phases, offering ionic conductivities (>10 –6 S cm –1 ) at ambient with an activation energy of 0.5 eV. This greatly increases their potential utility as ceramic electrolytes for all-solid-state batteries, which could simplify battery designs, significantly reduce costs, and increase their safety. Furthermore, a solid-state Li/Li 3.1 AlO 2 /Li symmetric cell was assembled and galvanostatically cycled at 0.375 mA cm –2 current density, exhibiting a transference number ≈ 1.

25 ENERGY STORAGE↗
DOE OSTI2021

Flexural strength of a conventionally processed and additively manufactured debased 94% alumina

Mechanical strength of a 94 wt% debased alumina was measured using ASTM-C1161 specimens fabricated via conventional and lithography-based ceramic manufacturing (LCM) methods. The effects of build orientation and a 1500°C wet hydrogen fire added to the LCM firing sequence on strength were evaluated. Additionally, a Weibull fit to the conventional flexural specimen data yielded 20 and 356 MPa for the modulus and characteristic strength, respectively. Weibull fits of the data from the LCM specimens yielded moduli between 7.5 and 11.3 and characteristics strengths between 333 and 339 MPa. A Weibull fit to data from LCM specimens subjected to the wet hydrogen fire yielded 14.2 and 376 MPa for the modulus and characteristic strength, respectively. The 95% confidence intervals for all Weibull parameters are reported. Average Archimedes bulk densities of LCM and conventional specimens were 3.732 and 3.730 g/cm 3 , respectively. Process dependent differences in surface morphology were observed in scanning electron microscope (SEM) images of specimen surfaces. SEM images of LCM specimen cross-sections showed alumina grain texture dependent on build direction, but no evidence of porosity concentrated in planes between printed layers. Fracture surfaces of LCM and conventionally processed specimens revealed hackle lines and mirror regions indicative of fracture initiation at the sample surface rather than the interior.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Hot Isostatic Pressing of Radioactive Nuclear Waste: The Calcine at INL - 16348

Hot Isostatic Pressing (HIP) is a technology that has been around for 60+ years. By using high temperature and high gas pressure, dry metal and ceramic powders can be consolidated and a volume decrease can be achieved. This paper presents the efforts using the HIPing process at the Idaho National Laboratory to treat the calcine radioactive waste. Once loaded into collapsible canisters, the HIPing would be used to treat the waste before final disposal. The resulting volume reduction was shown to be 20-70% and the cost ratio vs vitrification is 1:1.74. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2026

Multi-material direct ink writing and co-sintering of gadolinium oxide – zirconium oxide components

Methods for fabrication of multi-material or functionally graded ceramic composite architectures are of interest for numerous applications. However, conventional co-sintering of multi-material ceramic parts is a challenge because differences in the sintering behavior of the two materials leads to interfacial strain and, ultimately, component failure. Direct ink writing (DIW) is an extrusion-based additive manufacturing process that excels at multi-material printing because multiple extrusion nozzles can be installed on the same gantry system. Furthermore, the use of DIW as a method to fabricate multi-material ceramic green bodies offers an additional variable for controlling and potentially matching sintering kinetics in the slurry formulation used for two dissimilar feedstocks. In the work documented in this manuscript, we explored two strategies to successfully co-sinter multi-material ceramic oxides: slurry optimization to match sintering kinetics and material gradients to step from one material to another. This manuscript also quantifies the allowable mismatch that avoids part cracking in solid solution forming multi-material systems and discusses best strategies to reduce mismatch during co-sintering. Inks composed of gadolinium oxide (Gd 2 O 3 ) and zirconium oxide (ZrO 2 ), a surrogate for uranium oxide (UO 2 ), were thermally matched, which resulted in a sintering mismatch reduction of over 10%. It was found that ~1% mismatch is tolerable during debind cycles and that ~5% mismatch is manageable during sintering cycles after slurry formulations are optimized to match the sintering behavior. Use of continuous gradients is shown to reduce sintering mismatch, although geometric resolution may be lost due to solid solution formation.

Snarr, Patrick L. [Oak Ridge National Laboratory (↗
NASA NTRS2016

Advanced Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: NASA's Perspectives

This presentation reviews NASA environmental barrier coating (EBC) system development programs and the coating materials evolutions for protecting the SiC/SiC Ceramic Matrix Composites in order to meet the next generation engine performance requirements. The presentation focuses on several generations of NASA EBC systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. The current EBC development emphasis is placed on advanced NASA 2700F candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance are described. The research and development opportunities for advanced turbine airfoil environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling are discussed.

Ceramic Matrix Composites↗
DOE OSTI2015

Giant dielectric response and low dielectric loss in Al{sub 2}O{sub 3} grafted CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

This study sheds light on the effect of alumina on dielectric constant and dielectric loss of novel CaCu{sub 3}Ti{sub 4}O{sub 12} composite ceramics. Alumina, at several concentrations, was deposited on the surface of CaCu{sub 3}Ti{sub 4}O{sub 12} particles via sol-gel technique. The dielectric constant significantly increased for all frequencies and the dielectric loss substantially decreased for low and intermediate frequencies. These observations were attributed to the change in characteristics of grains and grain boundaries. It was found that the insulating properties of the grain boundaries are improved following the addition of Al{sub 2}O{sub 3}. The relative density of CaCu{sub 3}Ti{sub 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics decreased compared to the pure CaCu{sub 3}Ti{sub 4}O{sub 12} and the grain size was greatly changed with the alumina content affecting the dielectric properties. With the addition of alumina into CaCu{sub 3}Ti{sub 4}O{sub 12}, tighter interfaces formed. The 6%- and 10%-alumina ceramics showed the minimum dielectric loss and the maximum dielectric constant, respectively. Both the dielectric constant and loss tangent decreased in the 20%-alumina ceramic due to the formation of CuO secondary phase. It was revealed that Al serves as an electron acceptor decreasing the electron concentration, if Al{sup 3+} ions substitute for Ti{sup 4+} ions, and as an electron donor increasing the electron concentration, if Al{sup 3+} ions substitute for Ca{sup 2+} ions. We established a processing-microstructure-properties paradigm which opens new avenues for novel applications of CaCu{sub 3}Ti{sub 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Low Cost Glass-Ceramic Matrix Composites for Harsh Environment Heat Exchangers (Final Technical Report)

Nearly all high temperature heat exchangers are currently constructed from metallic alloys that can have good capability but are limited to hot inlet temperatures in the range of 1,200 to 1,400 °F. In general, increasing the hot inlet temperature will improve existing application cycles to operate more efficiently, and it will enable new application cycles to be viable that otherwise would not be. The objective of this project was to mature the technologies associated with the development of a ceramic-class heat exchanger that would significantly increase the operating temperature to 1,600 °F and above. The approach taken was to use Glass-Ceramic Matrix Composite (G-CMC) material and to fabricate coupon-scale tube sheet heat exchangers (HXs) to identify risks, refine details of the process and develop a pathway for this novel approach.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Closed Fuel Cycle Waste Treatment Strategy

This study is aimed at evaluating the existing waste management approaches for nuclear fuel cycle facilities in comparison to the objectives of implementing an advanced fuel cycle in the U.S. under current legal, regulatory, and logistical constructs. The study begins with the Global Nuclear Energy Partnership (GNEP) Integrated Waste Management Strategy (IWMS) (Gombert et al. 2008) as a general strategy and associated Waste Treatment Baseline Study (WTBS) (Gombert et al. 2007). The tenets of the IWMS are equally valid to the current waste management study. However, the flowsheet details have changed significantly from those considered under GNEP. In addition, significant additional waste management technology development has occurred since the GNEP waste management studies were performed. This study updates the information found in the WTBS, summarizes the results of more recent technology development efforts, and describes waste management approaches as they apply to a representative full recycle reprocessing flowsheet. Many of the waste management technologies discussed also apply to other potential flowsheets that involve reprocessing. These applications are occasionally discussed where the data are more readily available. The report summarizes the waste arising from aqueous reprocessing of a typical light-water reactor (LWR) fuel to separate actinides for use in fabricating metal sodium fast reactor (SFR) fuel and from electrochemical reprocessing of the metal SFR fuel to separate actinides for recycle back into the SFR in the form of metal fuel. The primary streams considered and the recommended waste forms include; Tritium in low-water cement in high integrity containers (HICs); Iodine-129: As a reference case, a glass composite material (GCM) formed by the encapsulation of the silver Mordenite (AgZ) getter material in a low-temperature glass is assumed. A number of alternatives with distinct advantages are also considered including a fused silica waste form with encapsulated nano-sized AgI crystals; Carbon-14 immobilized as a CaCO3 in a cement waste form; Krypton-85 stored as a compressed gas; An aqueous reprocessing high-level waste (HLW) raffinate waste immobilized by the vitrification process; An undissolved solids (UDS) fraction from aqueous reprocessing of LWR fuel either included in the borosilicate HLW glass or immobilized in the form of a metal alloy or titanate ceramics; Zirconium-based LWR fuel cladding hulls and stainless steel (SS) fuel assembly hardware super-compacted for disposal or purified for reuse (or disposal as low-level waste, LLW) of Zr by reactive gas separations; Electrochemical process salt HLW incorporated into a glass bonded Sodalite waste form; and Electrochemical process UDS and SS cladding hulls melted into an iron based alloy waste form. Mass and volume estimates for each of the recommended waste forms based on the source terms from a representative flowsheet are reported. In addition to the above listed primary waste streams, a range of secondary process wastes are generated by aqueous reprocessing of LWR fuel, metal SFR fuel fabrication, and electrochemical reprocessing of SFR fuel. These secondary wastes have been summarized and volumes estimated by type and classification. The important waste management data gaps and research needs have been summarized for each primary waste stream and selected waste process.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Engineering lithium-ion battery cathodes for high-voltage applications using electromagnetic excitation

Microwave radiation (MWR), a type of electromagnetic excitation source, reduces the synthesis temperature and processing time for chemical reactions compared to traditional synthesis methods. Recently, we demonstrated that MWR can engineer ceramics with different crystal phases compared to traditional methods [ Journal of Materials Chemistry A 5 , 35 (2017)]. Here, we further apply the MWR-assisted technique to improve the electrochemical performance of LiCoO 2 cathodes by engineering TiO 2 and ZrO 2 ceramic coatings. Electrochemical tests suggest that the TiO 2 coating improves the rate capability of the LiCoO 2 electrode. Both TiO 2 and ZrO 2 coatings improve the high-voltage (4.5 V) cycling stability of LiCoO 2 . The capacity remaining is improved from 52.8 to 84.4% and 81.9% by the TiO 2 coating and the ZrO 2 coating, respectively, after 40 cycles. We compare these results with existing studies that apply traditional methods to engineer TiO 2 /ZrO 2 on LiCoO 2 , and find that the MWR-assisted method shows better performance improvement. X-ray photoelectron spectroscopy measurements suggest that the improved cycling stability arises from the formation of metal fluorides that protect the electrode from side reactions with electrolytes. This mechanism is further supported by the reduced Co dissolution from TiO 2 /ZrO 2 -coated LiCoO 2 electrode after cycling. This study provides a new toolbox facilitating the integration of many delicate, low melting point materials like polymers into battery electrodes.

25 ENERGY STORAGE↗
DOE OSTI2015

Advanced thermal barrier coatings for operation in high hydrogen content fueled gas turbines

The Center for Thermal Spray Research (CTSR) at Stony Brook University in partnership with its industrial Consortium for Thermal Spray Technology is investigating science and technology related to advanced metallic alloy bond coats and ceramic thermal barrier coatings for applications in the hot section of gasified coal-based high hydrogen turbine power systems. In conjunction with our OEM partners (GE and Siemens) and through strategic partnership with Oak Ridge National Laboratory (ORNL) (materials degradation group and high temperature materials laboratory), a systems approach, considering all components of the TBC (multilayer ceramic top coat, metallic bond coat & superalloy substrate) is being taken during multi-layered coating design, process development and subsequent environmental testing. Recent advances in process science and advanced in situ thermal spray coating property measurement enabled within CTSR has been incorporated for full-field enhancement of coating and process reliability. The development of bond coat processing during this program explored various aspects of processing and microstructure and linked them to performance. The determination of the bond coat material was carried out during the initial stages of the program. Based on tests conducted both at Stony Brook University as well as those carried out at ORNL it was determined that the NiCoCrAlYHfSi (Amdry) bond coats had considerable benefits over NiCoCrAlY bond coats. Since the studies were also conducted at different cycling frequencies, thereby addressing an associated need for performance under different loading conditions, the Amdry bond coat was selected as the material of choice going forward in the program. With initial investigations focused on the fabrication of HVOF bond coats and the performance of TBC under furnace cycle tests , several processing strategies were developed. Two-layered HVOF bond coats were developed to render optimal balance of density and surface roughness and resulted in improved TBC lifetimes. Processing based approaches of identifying optimal processing regimes deploying advanced in-situ coating property measurements and in-flight diagnostic tools were used to develop process maps for bond coats. Having established a framework for the bond coat processing using the HVOF process, effort were channeled towards fabrication of APS and VPS bond coats with the same material composition. Comparative evaluation of the three deposition processes with regard to their microstrcuture , surface profiles and TBC performance were carried out and provided valuable insights into factors that require concurrent consideration for the development of bond coats for advanced TBC systems. Over the course of this program several advancements were made on the development of durable thermal barrier coatings. Process optimization techniques were utilized to identify processing regimes for both conventional YSZ as well as other TBC compositions such as Gadolinium Zirconate and other Co-doped materials. Measurement of critical properties for these formed the initial stages of the program to identify potential challenges in their implementation as part of a TBC system. High temperature thermal conductivity measurements as well as sintering behavior of both YSZ and GDZ coatings were evaluated as part of initial efforts to undersand the influence of processing on coating properties. By effectively linking fundamental coating properties of fracture toughness and elastic modulus to the cyclic performance of coatings, a durability strategy for APS YSZ coatings was developed. In order to meet the goals of fabricating a multimaterial TBC system further research was carried out on the development of a gradient thermal conductivity model and the evaluation of sintering behavior of multimaterial coatings. Layer optimization for desired properties in the multimaterial TBC was achieved by an iterative feedback approach utilizing process maps and in-situ and ex-situ coating property sensors. Addressing the challenges pertaining to the integration of the two materials YSZ and GDZ led to one of most the critical outcomes of this program, the development of durable multimaterial, multifunctional TBC systems.

36 MATERIALS SCIENCE↗
NASA NTRS1981

Ceramic technology for solar thermal receivers

The high-temperature capability, resistance to corrosive environments and non-strategic nature of ceramics have prompted applications in the solar thermal field whose advantages over metallic devices of comparable performance may begin to be assessed. It is shown by a survey of point-focusing receiver designs employing a variety of ceramic compositions and fabrication methods that the state-of-the-art in structural ceramics is not sufficiently advanced to fully realize the promised benefits of higher temperature capabilities at lower cost than metallic alternatives. The ceramics considered include alumina, berylia, magnesia, stabilized zirconia, fused silica, silicon nitride, silicon carbide, mullite and cordierite, processed by such methods as isostatic pressing, dry pressing, slip casting, extrusion, calendaring and injection molding.

Kudirka, A. A.↗
NASA NTRS1992

Sol-Gel Synthesis Of Aluminoborosilicate Powders

Application of sol-gel process to synthesis of aluminoborosilicate powders shows potential for control of microstructures of materials. Development of materials having enhanced processing characteristics prove advantageous in extending high-temperature endurance of fibrous refractory composite insulation made from ceramic fibers.

Bull, Jeffrey↗