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At least 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Precipitation Hardening in Ferroelectric Ceramics

Domain wall motion in ferroics, similar to dislocation motion in metals, can be tuned by well-concepted microstructural elements. In demanding high-power applications of piezoelectric materials, the domain wall motion is considered as a lossy hysteretic mechanism that should be restricted. Current applications for so-called hard piezoelectrics are abundant and hinge on the use of an acceptor-doping scheme. However, this mechanism features severe limitations due to enhanced mobility of oxygen vacancies at moderate temperatures. By analogy with metal technology, the authors present here a new solution for electroceramics, where precipitates are utilized to pin domain walls and improve piezoelectric properties. Through a sequence of sintering, nucleation, and precipitate growth, intragranular precipitates leading to a fine domain structure are developed as shown by transmission electron microscopy, piezoresponse force microscopy, and phase-field simulation. This structure impedes the domain wall motion as elucidated by electromechanical characterization. As a result, the mechanical quality factor is increased by ≈50% and the hysteresis in electrostrain is suppressed considerably. This is even achieved with slightly increased piezoelectric coefficient and electromechanical coupling factor. This novel process can be smoothly implemented in industrial production processes and is accessible to simple laboratory experimentation for microstructure optimization and implementation in various ferroelectric systems.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Dynamic Triple-Mode Sorption and Outgassing in Materials

Moisture uptake and outgassing can be detrimental to a system by altering the chemical and mechanical properties of materials within the system over time. In this work, we conducted isotherm experiments to investigate dynamic moisture sorption and desorption in markedly different materials, i.e., a polymeric material, Sylgard-184 and a ceramic aluminosilicate material, Zircar RS-1200, at different temperatures (30 °C–70 °C) by varying the water activity (0.0–0.90). Sylgard-184 showed a linear sorption and outgassing behavior with no-hysteresis over the entire temperature and water activity range considered here. Whereas, the sorption and outgassing of Zircar RS-1200 was highly non-linear with significant hysteresis, especially at higher water activities, at all temperatures considered here. The type of hysteresis suggested the presence of mesopores in Zircar RS-1200, whereas the lack of hysteresis in Sylgard-184 indicates that it has a nonporous structure. A diffusion model coupled with a dynamic, triple-mode sorption (Langmuir, Henry, and pooling modes) model employed in this study matched our experimental data very well and provides mechanistic insight into the processes. Our triple-mode sorption model was adaptive enough to (1) model these distinctly different materials and (2) predict sorption and outgassing under conditions that are distinctly different from the parameterization experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Synthesis and flash sintering of (Hf 1-x Zr x )B 2 solid solution powders

(Hf 1-x Zr x )B 2 solid solution powders were synthesized by two methods. First, solution-based processing of HfCl 4 , ZrCl 4 , sucrose, and H 3 BO 3 was conducted followed by heat treatment in Argon to carry out the carbothermal reduction (CTR) reaction to form the diboride powders. Alternatively, in the so-called borohydride reduction (BHR) method, HfCl 4 , ZrCl 4 and NaBH 4 were mixed in an Argon glove box followed by heat treatment in Argon at 700-1500°C. The synthesized powders were characterized by XRD, SEM, TEM, EDS, and TGA, and the influence of different parameters such as starting composition, heat treatment temperature and time on products characteristics were revealed. Both CTR and BHR solid solution powders were then consolidated within ~5 min in a homemade flash sintering (FS) setup. Here, the composition, microstructure, hardness, and thermal-oxidation properties of flash sintered ceramics were characterized, and the implication of this study and directions for future research were discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Quantitative Three-Dimensional Imaging of Heterogeneous Materials by Thermal Tomography

Infrared thermal imaging based on active thermal excitations has been widely used for nondestructive evaluation ( NDE) of materials. While the experimental systems have remained essentially the same during the last few decades, development of advanced data-processing methods has significantly improved the capabilities of this technology. However, many limitations still exist. One fundamental limitation is the requirement, either explicitly or implicitly, of the tested material to be homogeneous such that detected thermal contrasts may be used to determine an average material property or attributed to flaws. In this paper, a new thermal tomography ( TT) method is introduced, which for the first time can evaluate heterogeneous materials by directly imaging their thermal-property variations with space. It utilizes one-sided flash thermal-imaging data to construct the three-dimensional ( 3D) distribution of thermal effusivity in the entire volume of a test sample. Theoretical analyses for single and multilayer material systems were conducted to validate its formulation and to demonstrate its performance. Experimental results for a ceramic composite plate and a thermal barrier coating ( TBC) sample are also presented. It was shown that thermal diffusion is the primary factor that degrades the spatial resolution with depth for TT; the spatial resolutions in the lateral and axial directions were quantitatively evaluated.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Formation mechanisms of boron oxide films fabricated by large-area electron beam-induced deposition of trimethyl borate [Formation Mechanisms of Boron Oxide Fillms Fabricated by Large Area Electron Beam-Induced Deposition of Trimethyl Borate]

Boron-containing materials are increasingly drawing interest for the use in electronics, optics, laser targets, neutron absorbers, and high-temperature and chemically resistant ceramics. In this article, the first investigation into the deposition of boron-based material via electron beam-induced deposition (EBID) is reported. Thin films were deposited using a novel, large-area EBID system that is shown to deposit material at rates comparable to conventional techniques such as laser-induced chemical vapor deposition. The deposition rate and stoichiometry of boron oxide fabricated by EBID using trimethyl borate (TMB) as precursor is found to be critically dependent on the substrate temperature. By comparing the deposition mechanisms of TMB to the conventional, alkoxide-based precursor tetraethyl orthosilicate it is revealed that ligand chemistry does not precisely predict the pathways leading to deposition of material via EBID. Lastly, the results demonstrate the first boron-containing material deposited by the EBID process and the potential for EBID as a scalable fabrication technique that could have a transformative effect on the athermal deposition of materials.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Spray Pyrolysis-Aerosol Deposition for the Production of Thick Yttria-Stabilized Zirconia Coatings

Aerosol deposition (AD) is a coating technique wherein particles are impacted onto a target substrate at reduced pressures, and supersonic particle impact velocities lead to coating consolidation. The limiting step in AD application is often not supersonic deposition operation, but aerosolization of powder particles with the proper size distribution; the translational impact velocity is strongly size-dependent. It is demonstrated that by directly synthesizing particles in the gas phase, size-controlled ceramic particles can be injected into AD systems. This in situ formation step obviates the need for particle aerosolization. Ultrasonic spray pyrolysis (USP) is applied to produce yttria-stabilized zirconia (YSZ), and USP is directly coupled with AD to produce consolidated, thick, YSZ coatings on metal substrates. USP-AD yields YSZ coatings on stainless steel and aluminum substrates with porosities <0.20, which grow to thicknesses beyond 100 μm. Aerodynamic particle spectrometry and electron microscopy reveal that the depositing particles are 200 nm–1.2 μm in diameter, though each particle is composed of nanocrystalline YSZ. Supporting computational fluid dynamics calculations demonstrate that the YSZ particle impact speeds are above 300 m s -1 . Thermal conductivity measurements demonstrate that USP-AD coatings have conductivities consistent with those produced from high-temperature processes.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Deconvolution of Water-Splitting on the Triple-Conducting Ruddlesden–Popper-Phase Anode for Protonic Ceramic Electrolysis Cells

Triple-conducting materials have been proved to improve the performance of popular protonic ceramic electrolysis cells. However, partially because of the complexity of the water splitting reaction involving three charge carriers, that is, oxygen (O 2– ), proton (H + ), and electron (e – ), the triple-conducting reaction mechanism was not clear, and the reaction conducting pathways have seldom been addressed. In this study, the triple conducting Ruddlesden–Popper phase Pr 1.75 Ba 0.25 NiO 4+δ as an anode on the BaCe 0.7 Zr 0.1 Y 0.1 Yb 0.1 O 3–δ electrolyte was fabricated and its electroresponses were characterized by electrochemical impedance spectroscopy with various atmospheres and temperatures. The impedance spectra are deconvoluted by means of the distribution of the relaxation time method. The surface exchange rate and chemical diffusivity of H + and O 2– are characterized by electrical conductivity relaxation. The physical locations of electrochemical processes are also identified by atomic layer deposition with a surface inhibitor. A microkinetics model is proposed toward conductivities, triple-conducting pathways, reactant dependency, surface exchange and bulk diffusion capabilities, and other relevant properties. Lastly, the rate-limiting steps and suggestions for further improvement of electrode performance are presented.

25 ENERGY STORAGE↗
DOE OSTI2019

Fracture Toughness Evaluation for Sandia Mock-up Stainless Steel Canister Weldment Using Spiral Notch Torsion Fracture Toughness Test

Many radioactive materials within the nuclear fuel cycle present a significant hazard. Such materials include spent nuclear fuel, high-level waste, legacy waste and other nuclear materials that have no current outlet than storage. These materials are often held in long-term storage as an interim stage within their lifecycle. Lifecycles can include reuse or disposal. Safety and security of spent nuclear fuel (SNF) interim storage installations are very important, due to a great concentration of fission products, actinides and activation products. Stress corrosion cracking of interim storage containers has been identified as a high priority data gap by the Department of Energy. However, little has been done with regards to the canister weld material properties, including the fracture toughness, and their impact on stress corrosion, until recently from Sandia National Laboratory canister mockup program. Furthermore, because no post-weld heat treatment was required, the associated high tensile residual stress within these canister welds can drive the initiation and growth of stress corrosion cracking (SCC) cracks. Thus, the fracture mechanical property, such as fracture toughness, is an essential information to understand the canister weldment fracture resistance behavior and to support mitigation protocol development to counter SCC. In this work, we carried out fracture toughness evaluation on the received mock-up canister weldments from Sandia, using spiral notch torsion fracture test technology. The details of the weldment fracture toughness evaluation program development at ORNL are presented in this progress report. The objective of this research is to collect fracture toughness data on the mock-up canister weldment from Sandia National Laboratory. Data will be collected under quasi-static fracture loading using the Oak Ridge National Laboratory (ORNL) developed Spiral Notch Torsion Test (SNTT) technology carried out on a biaxial tension/torsion tester. These data will be used to support the ongoing SNF dry storage canister modeling activities and to address regulatory issues associated with canister container integrity and the follow-on SNF system transport reliability. SNTT has been a recent breakthrough in measuring fracture toughness for different materials, including metals, ceramics, concrete and polymers composites. Due to its high geometry constraint and unique loading condition, SNTT can be used to measure the fracture toughness with smaller specimens without concern of size effects. The application of SNTT to brittle materials has been proved to be successful. The micro-cracks induced by original notches in brittle materials could ensure crack growth in SNTT samples. Therefore, no fatigue pre-cracks are needed. The application of SNTT to the ductile material to generate valid toughness data will require a test sample with sufficient crack length to increase the sample fracture tip localized constraint. Fatigue pre-crack growth techniques are employed to introduce sharp crack front into the sample. Previously, only rough calculations were applied to estimate the compliance evolution in the SNTT crack growth process; while accurate quantitative descriptions have never been attempted. This generates an urgent need to understand the crack evolution during the SNTT fracture testing process of ductile materials. The newly developed governing equations for SNTT crack growth estimate are used to control the fatigue crack growth to effectively reaching the target crack length. The detailed SNTT approach and its estimated fracture toughness for the as-received Sandia canister weldment and the associated baseline 304 stainless steel are presented in this report. In the past SNTT technology has also been successfully applied to investigate the fracture behavior of X52 and X80 steels and the X52 welded materials used for hydrogen infrastructures. The current study in supporting Sandia SNF Dry Storage Mock-up Canister Program is the first attempt of applying SNTT to the highly ductile stainless steel and the associated weld materials. The SNTT test results indicate that SNTT method is a reliable test approach with good repeatability in applying to SS304 steel and SS304/308 weld material. The estimate JQ upon fracture for the baseline SS304 steel is at 1618 lb/in. The estimate JQ upon fracture for the SS304/308 weld from HAZ and weld specimens are 720 lb/in and 850 lb/in, respectively.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

MAGNETICALLY SUSPENDED CANNED ROTOR PUMPS FOR THE INTEGRAL MOLTEN SALT REACTOR

This project developed a molten salt pump design for small modular reactors, concentrated solar, and Gen IV nuclear reactors with a magnetically levitated rotor that can operate at temperatures of up to 700 °C. This eliminates the need for rotating seals and roller element bearings which require maintenance and are prone to failure. The pump design is also more compact than existing molten salt pump designs which require long shafts to thermally isolate the electric motor. The aims of the project are to: 1) design and test the molten salt pump, 2) develop and test a high temperature position sensor needed for magnetic bearing control, and 3) develop and test high temperature coil fabrication methods for electric motor and magnetic bearing fabrication. To develop the high temperature coils, conductor materials were analyzed for oxidation, diffusion, cladding, and resistivity. Of the candidate conductor materials that met the requirements, silver was chosen. The long-term impact of radiation on silver resistivity was analyzed by developing a model of a generic molten salt fast reactor to model the conductor irradiation in worst case scenarios. The analysis showed that increased resistivity due to transmutation of silver decreases exponentially with the reactor reflector thickness. Different electrical insulation materials were tested and the final high temperature coils developed were able to withstand conductor to ground voltages up to 1800 V before insulation breakdown. Magnetic bearings require high-precision high-speed measurements of the rotor position to operate. Current commercial position sensors can only operate up to 550 °C so a novel position sensor was developed that can operate up to 800 °C. These sensors were also designed to measure the position of the metallic rotor through a thin metallic corrosion barrier that protects that coils, insulation, and magnetic cores so that the salt containment barrier does not have any penetrations. The high-temperature sensor was tested and had comparable performance to commercially available inductive position sensors. The sensor design and signal processing has led to several invention disclosures. The magnetically levitated molten salt pump design was completed and analyzed. The chloride salt test loop at Oak Ridge National Laboratory was chosen to test the pump and the pump hydraulics and power were designed for the test loop flow and pressure requirements. Classes of motor designs that do not utilize permanent magnetic were considered for the high-temperature motor. After extensive analysis of their performance, a synchronous reluctance motor was chosen for the pump. The design was refined and analyzed to optimize performance. The magnetic bearings were designed to meet the force and frequency requirements necessary to levitate the rotor and reject disturbances from rotor imbalance, motor forces, and hydraulic forces. Compliant mounts for the position sensors were designed that would not damage the ceramic sensor components and maintain sensor alignment over a wide temperature range. A thermal hydraulic analysis of the molten salt coolant flow used to cool the rotor and stator was performed to ensure that the maximum temperature in the rotor and stator will not exceed 725 °C. The corrosion barrier and casing were designed to maintain the salt fluid boundary by using compliant features to absorb large expansion mismatches due to different coefficients of thermal expansion (CTE). Finally, the salt drain and fill systems were designed along with the pump support structure, integration with the test loop, and thermal insulation and heating. Corrosion barrier fabrication experiments were performed to assess using laser cladding to apply a sub-millimeter corrosion barrier to the surface of a Fe-Co-V magnetic core material. The cladding method showed minimal mixing between materials at their interface and withstood temperature cycling without damage to the cladding. The technology commercialization is focused on the high-temperature position sensors and there has been significant interest from the nuclear industry in utilizing these sensors along with some interest from the aerospace industry. The project also led to a research collaboration with a fusion energy industrial partner to study barriers to scaling the pump design from the kW size to the MW size. This research collaboration will also study methods to create high-temperature coils that have conductor to ground breakdown voltages above 5 kV. The successful development of high-temperature electromagnetic coils and high-temperature position sensors greatly increases the temperature limits for electromagnetic devices that don’t rely on permanent magnets. This includes electric motors, magnetic bearings, linear actuators, rotary position and velocity sensing, actuated valves, and generators to name a few. This will fill a current need in molten salt reactors, concentrated solar, and fusion energy for these critical peripheral devices needed for practical reactor designs that do not currently have commercial solutions.

Hines, J Wesley↗
DOE OSTI2021

Gel composite electrolyte – an effective way to utilize ceramic fillers in lithium batteries

Achieving synergy between ion-conducting polymers and ceramics in a composite electrolyte has been proven to be difficult as the complicated ceramic/polymer interface presents challenges to understand and control. In this work, we report a strategy to utilize discrete ceramic fillers to form a gel composite electrolyte with enhanced transport properties for lithium metal batteries. The matrix of the composite membrane is crosslinked poly(ethylene oxide) with bis(trifluoromethane)sulfonimide lithium salt (LiTFSI). The membrane is plasticized with tetraethylene glycol dimethyl ether (TEGDME). The incorporation of doped-lithium aluminum titanium phosphate particles (LICGC™) into the membrane greatly improves the membrane's cycling characteristics against the lithium electrode, exhibiting lower interfacial impedance, lower overpotential and higher rate capability. The underpinnings of the superior performance of the gel composite electrolyte are discussed in depth. LICGC™ can immobilize the TFSI - anions in the polymer matrix and simultaneously promote Li+ transport by increasing the plasticizer to Li + ratio. Further, the transport enhancement is achieved without sacrificing mechanical properties. The composite membrane shows significantly improved handleability and processability. This work sheds light on the design strategy for a safe electrolyte towards stable Li metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2013

Engineered Nano-Scale Ceramic Supports for PEM Fuel Cells

Development of electronically conductive ceramic materials is of fundamental importance to a wide variety of applications. One application of particular interest is proton exchange membrane fuel cells (PEMFC), where strong oxidizing conditions exist, especially in the cathode. The reaction that takes place in the cathodic side of PEMFCs is the oxygen reduction reaction (ORR) which is considered to be kinetically sluggish and thus, it is catalyzed, usually by platinum nano-particles. Due to the high cost of such catalysts, and in order to maintain their optimized nano-crystallite structure, they are normally supported on a relatively cheap, electronically conductive, porous, high surface area support. Most of the electrode support materials used in fuel cells today are carbon based which are highly sensitive to corrosive conditions and thus corrode under normal fuel cell operating conditions. This leads to processes that can be detrimental to the fuel cell and is manifested in the form of loss of surface area, impediment of mass transport and loss of catalyst activity due to sintering or dissolution. The direct consequence of these effects is the loss of the overall fuel cell power output overtime and shortening their lifetime; both make this technology less attractive to industry. In order to make PEMFCs more viable, it is necessary to extend their lifetime and reliability by improving the catalyst support.

08 HYDROGEN↗
DOE OSTI2022

High-Temperature Ceramic-Carbonate Dual-Phase Membrane Reactor for Pre-combustion Carbon Dioxide Capture (Final Scientific/Technical Report)

Arizona State University, in collaboration with University of South Carolina, worked on a project aimed at development of a new high temperature, high pressure CO 2 perm-selective membrane reactor for water-gas-shift reaction (WGS) with simulated gasifier syngas to produce a high concentration H 2 stream with CO 2 capture. The membrane reactor is made of a CO 2 semi-permeable ceramic-carbonate dual-phase (CCDP) membrane with high CO 2 perm-selectivity/permeance and thermal/mechanical stability for application in WGS reaction. The objectives of this project were to (1) synthesize the chemically/thermally stable tubular CCDP membranes with CO 2 permeance and selectivity (with respect to H 2 , CO or H 2 O) larger than 6.5×10-7 mol/m2·s·Pa and 500, respectively; (2) establish CCDP membrane reactor setup and study high pressure CO 2 permeation and WGS reaction with CO 2 capture using the setup; and (3) identify conditions for WGS in the CCDP membrane reactor that produce CO 2 and H 2 streams with purity of >99% and >90% respectively at CO conversion >95% and overall carbon capture >90%. The work in this project included both membrane development and membrane reactor process study. The membrane development efforts were focused on investigating a H 2 S resistant and highly oxygen-ionic conducting metal oxide material and membrane for CO 2 separation, fabrication of tubular samaria-doped-ceria/molten-carbonate CCDP membrane with high mechanical strength, and experimental and modeling study of high-pressure CO 2 permeation of the CCDP membranes. Mathematical models were developed to describe WGS in the CCDP membrane reactor without a catalyst or packed with a commercial high temperature WGS catalyst. Experiments on WGS in the CCDP membrane reactor with the commercial WGS catalyst, guided by the model analysis, were performed to identify optimum conditions for achieving the CO conversion, carbon capture, and the purity of the H 2 and CO 2 streams mentioned above. At 30 atm feed pressure, 750°C operation temperature, space velocity of 250 h-1, and with steam sweep, a single-stage CCDP membrane reactor with average CO 2 permeation flux of 0.5 cm3(STP)/min.cm2 can achieve CO 2 conversion of 95% and overall carbon capture of 94%, and produce CO 2 and H 2 streams with dry-based purity of >99% and 92% respectively. The project also included process design and techno-economic analysis (TEA) for a CCDP membrane reactor process for WGS reaction with CO 2 capture for a 550 MW coal-fired IGCC power plant, and its comparison with the conventional fixed-bed reactor system for WGS with follow-up CO 2 capture by an amine absorption process. The target performance for the reactor for WGS with CO 2 capture includes CO conversion >95%, hydrogen stream purity >90%, CO 2 stream purity >95%, and total carbon capture >90%. The CCDP membrane developed in this project can achieve the performance target, without subsequent CO 2 capture process at the optimum conditions identified in this project. The outcome of the process design and TEA analysis shows that the membrane reactor for WGS with in-situ CO 2 capture has an operating cost about 40% lower than that for the conventional fixed-bed reactor with a separate amine absorption process for CO 2 capture. However, the capital cost of the membrane reactor process is about twice that of the conventional process because of the higher cost of the CCDP membrane. Modeling analysis shows that a membrane reactor using a CCDP membrane with higher CO 2 permeance (about three times the current value) can deliver the targeted performance for WGS reaction with CO 2 capture at a much higher space velocity and lower membrane surface area to catalyst volume ratio, leading to a smaller catalyst amount and/or membrane area and hence significantly reduced membrane reactor capital costs.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2017

Robust metal-ceramic coaxial cable sensors for distributed temperature monitoring in fossil energy power systems

The project aims to develop a new type of low cost, robust metal-ceramic coaxial cable (MCCC) Fabry-Pérot interferometer (FPI) sensor and demonstrate the capability of cascading a series of FPI sensing points in a single MCCC for real-time distributed monitoring of temperature up to 1000°C. The technical accomplishments of this project include: (i) development of metal and ceramic materials for fabricating the MCCC suitable for use in high temperature (up to 1000oC) fossil fuel, (ii) design, construction and test of single point MCCC-FPI sensors for high temperature measurement at deviation within ±2.7%, (iv) demonstration of the MCCC-FPI sensors for real-time distributed temperature measurement with desired sensitivity, spatial resolution, stability, and response speed that are important to practical applications, and (v) development of a novel MCCC-FPI sensor platform for measuring high frequency dielectric constants for solids and liquids as function of temperature. Single point MCCC-FPI sensors are fabricated based on the FPI parameters, including the relationship between reflector width and reflectance as well as the inter-reflector distance for a FPI, estimated by model calculations. MCCC-FPI sensors have been made using insulators of packed ceramic powders, ceramic tubes, and air or inert gases; outer conductors of various metal tubes; inner conductors of wires of the same metal materials as the tubes used; and reflectors of dense ceramic discs, casted ceramic discs and air gaps. The insulator, conductor and reflector materials are investigated for their thermal, chemical, and structural stabilities under temperatures up to 1000°C in simulated coal-derived syngas. Based on the experimental findings, alumina tube and discs, and stainless steel tube and wire are selected for reflector, insulator and outer and inner conductors, respectively. Air or inert gases are found to be useful for reflectors (in the form of narrow groves) or insulators (in the form of empty chamber cavity between ceramic discs) in construction of MCCC-FPI sensors. Single point MCCC-FPI sensors have been fabricated using stainless steel as conductors, dense α-alumina tubes as dielectric insulators, and two air gaps in the insulator as reflectors. The MCCC-FPI sensor with air gap reflectors has been demonstrated for measuring temperature between 200 and 500°C using microwave as sensing signal in a frequency range of 2 – 8 GHz. The temperature measurement is achieved by monitoring the frequency shift (Δƒ) of a selected resonant peak of the microwave interferogram reflected from the pair of air gap reflectors. The MCCC-FPI sensor exhibited excellent linear temperature-dependence for Δƒ, good accuracy (deviation ±2.7%), and reasonable response speed (<180 s for stabilization). Thermal drifting of the sensing signal was also rather minimal for the MCCC-FPI sensors after operating for more than one week at around 500oC. MCCC-FPI sensors with each containing 2 or 3 pairs of reflectors (i.e. 2 or 3 FPIs in a single cable) have been fabricated and demonstrated for distributed temperature measurement between 250 and 550°C in a microwave frequency range of 3-6 GHz. The measurement is achieved by monitoring the frequency shift of a selected resonant peak of the reflected microwave interferogram, which is obtained by the join-time-domain signal processing method. The results demonstrate that the FPI sensing points in both the three-point and two-point MCCC sensors can measure distributed high temperature with good reproducibility and consistency in multiple runs of measurement tests. The sensor signal displays excellent linear dependence between temperature and the corresponding frequency shift. The 2-point and 3-point MCCC-FPI sensors also exhibit fast response to environmental temperature changes. A three-point MCCC-FPI sensor has been further examined for temperature measurement up to 1000°C for multiple heating-cooling cycles and the results prove that the sensor is suitable for distributed temperature measurement up to 1000°C. MCCC-FPI sensors with more than 4 FPIs point in a single line are made in two structures: the first uses alumina tube as insulation and air gaps as reflectors; and the second uses air chamber as insulation and complete circular alumina discs (2 mm-thick) as reflectors. MCCC-FPIs in neither of the two structures are able to exceed four FPIs in a cable because the reflections from the FPIs are too strong for the microwave to transmit through >4 FPIs over a long distance. Specially shaped alumina discs made by removing parts of the circular discs are found to decrease the microwave reflectance because of reduced reflection areas. However, the smallest reflectance (in terms of percentage of the incident signal) obtained in this work is as high as 7.5%, which is still too large to construct more than 10 FPIs in a single MCCC. Nevertheless, the feasibility of the proposed multipoint MCCC-FPI has been demonstrated using air insulation and 2 mm-thick low-ε r Teflon discs as reflectors on a 2 m-long cable containing 10 FPIs (with reflectance <5% on each FPI). These results indicate that the contrast of dielectric constant between the insulation and reflector has a more significant impact on the reflectance. Thus, future research efforts should also be directed to developing ceramic materials (dense or porous) with low dielectric constant values which, when used as insulation or reflector, can realize large numbers of FPIs in a single cable over a long distance. To assist the development of high temperature dielectric materials, a novel MCCC-FPI sensor platform is developed and successfully demonstrated for measuring high frequency dielectric constants for fluids, packed dielectric solids, and ceramic tube materials and determining ε r dependencies on temperature and chemical composition, etc..

36 MATERIALS SCIENCE↗
DOE OSTI2020

Universal chemomechanical design rules for solid-ion conductors to prevent dendrite formation in lithium metal batteries

Dendrite formation during electrodeposition while charging lithium metal batteries compromises their safety. Although high-shear-modulus ( G s ) solid-ion conductors (SICs) have been prioritized to resolve the pressure-driven instabilities that lead to dendrite propagation and cell shorting, it is unclear whether these or alternatives are needed to guide uniform lithium electrodeposition, which is intrinsically density-driven. Here, we show that SICs can be designed within a universal chemomechanical paradigm to access either pressure-driven dendrite-blocking or density-driven dendrite-suppressing properties, but not both. This dichotomy reflects the competing influence of the SIC’s mechanical properties and the partial molar volume of Li + $(V_{\mathrm{Li}^+})$ relative to those of the lithium anode ( G Li and V Li ) on plating outcomes. Within this paradigm, we explore SICs in a previously unrecognized dendrite-suppressing regime that are concomitantly ‘soft’, as is typical of polymer electrolytes, but feature an atypically low $(V_{\mathrm{Li}^+})$ that is more reminiscent of ‘hard’ ceramics. Li plating (1 mA cm -2 ; T = 20 °C) mediated by these SICs is uniform, as revealed using synchrotron hard X-ray microtomography. As a result, cell cycle life is extended, even when assembled with thin Li anodes (~30 µm) and either high-voltage NMC-622 cathodes (1.44 mAh cm -2 ) or high-capacity sulfur cathodes (3.02 mAh cm -2 ).

25 ENERGY STORAGE↗
DOE OSTI2026

High hardness and oxidation-resistant Cr-containing medium entropy ZrTaW diboride

This study reports the successful synthesis of a Cr-containing (Zr 0.30 Ta 0.34 Cr 0.06 W 0.30 )B 2 medium-entropy boride (MEB) via an in-situ reactive borothermal reduction route from oxide precursors. High-energy ball milling was employed to homogenize the precursor mixture prior to reactive densification. X-ray diffraction confirmed the formation of a predominantly AlB₂-type hexagonal diboride structure together with a secondary (W X , M 1-X )B monoboride phase. Microstructural characterization revealed compositional heterogeneity and localized W-rich regions associated with the secondary phase. The synthesized medium-entropy boride exhibited enhanced mechanical properties, which are attributed to lattice distortion and solid-solution strengthening effects. Thermogravimetric analysis revealed complex multistage oxidation behavior, and the oxidation resistance was compared with conventional ultra-high-temperature diborides. The results demonstrate the strong relationship between oxide-derived processing, compositional complexity, phase evolution, and oxidation behavior, highlighting the potential of medium-entropy borides for high-temperature structural applications

36 MATERIALS SCIENCE↗
DOE OSTI2018

A highly active hybrid catalyst modified (La 0.60 Sr 0.40 ) 0.95 Co 0.20 Fe 0.80 O 3-δ cathode for proton conducting solid oxide fuel cells

The sluggish reaction kinetics in the cathode usually leads to considerable cathode polarization resistance, hindering the development of proton conducting solid oxide fuel cells (H-SOFCs) operated at intermediate temperatures (400–650 °C). In this paper, to address this problem, for the first time, a novel hybrid catalyst consisting of PrNi 0.5 Mn 0.5 O 3 and PrOx is impregnated in the (La 0.60 Sr 0.40 ) 0.95 Co 0.20 Fe 0.80 O 3-δ (LSCF) cathode of H-SOFCs, resulting in significant enhancement of the cathode reaction kinetics. Single cells with impregnated LSCF cathode and BaZr 0.8 Y 0.2 O 3 (BZY) electrolyte yield a maximum power density (MPD) of 0.198 W cm -2 at 600 °C, more than doubled of that with blank LSCF cathode (0.083 W cm -2 ). ECR and EIS studies reveal that the hybrid catalyst can substantially accelerate the oxygen-ion transfer and oxygen dissociation-absorption processes in the cathode, resulting in significantly lower polarization resistance and higher MPD. In addition, the hybrid catalyst possesses good chemical and microstructural stability at 600 °C. Consequently, the single cells with impregnated LSCF cathode show excellent durability. Finally, this study shows that the impregnation of this novel hybrid catalyst in the cathode could be a promising approach to improve the performance and stability of H-SOFCs.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Carbon-13 NMR spectra of lignin isolated from field grown transgenic poplar

Here we present a curated dataset of a series of 13C nuclear magnetic resonance (NMR) spectra of lignin isolated from transgenic monolignol 4-O-methyltransferase (MOMT4) engineered poplar. The transgenic poplar was collected from a 3-year field trial experiment. The poplar was Soxhlet-extracted with toluene/ethanol and the extractives-free poplar was then ball-milled in a Retsch PM100 planetary ball mill using a porcelain jar with ceramic balls at 600 rpm for 2 h. The ball-milled materials were then subjected to enzymatic hydrolysis for 48 h followed by centrifugation and washing with deionized water. The solid residue was extracted twice with 96:4 (v/v) 1,4-dioxane/water mixture at room temperature overnight. The extracts were combined, rotary evaporated, and freeze-dried to recover the lignin. The dry lignin samples were dissolved in deuterated dimethyl sulfoxide for NMR characterization. 13C experiments were performed in a Bruker Avance III HD 500 MHz NMR spectrometer operating at a frequency of 125.12 MHz for the 13C nucleus using a standard Bruker pulse sequence (zgpg) on a Prodigy platform cryoprobe. The NMR spectra were acquired under the following conditions: spectra width 229 ppm, 64k data points, 1s pulse delay, and 6k scans. All the data was processed using the Bruker’s TopSpin 3.6 software. Additional meta data is embedded in the raw spectra files.

13C NMR, lignin, poplar, field trial, MOMT4, CBI↗