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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Electrical and structural properties of ZnO synthesized via infiltration of lithographically defined polymer templates

We investigate the electrical and structural properties of infiltration-synthesized ZnO. In-plane ZnO nanowire arrays with prescribed positional registrations are generated by infiltrating diethlyzinc and water vapor into lithographically defined SU-8 polymer templates and removing organic matrix by oxygen plasma ashing. Transmission electron microscopy reveals that homogeneously amorphous as-infiltrated polymer templates transform into highly nanocrystalline ZnO upon removal of organic matrix. Field-effect transistor device measurements show that the synthesized ZnO after thermal annealing displays a typical n-type behavior, ~1019 cm -3 carrier density, and ~0.1 cm 2 V -1 s -1 electron mobility, reflecting highly nanocrystalline internal structure. The results demonstrate the potential application of infiltration synthesis in fabricating metal oxide electronic devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Co-infiltration of Nickel and Mixed Conducting Gd 0.1 Ce 0.9 O 2-δ and La 0.6 Sr 0.3 Ni 0.15 Cr 0.85 O 3-δ Phases in Ni-YSZ Anodes for Improved Stability and Performance

Liquid-phase infiltration of nickel (Ni) nanoparticles in Ni/yttria-stabilized-zirconia (YSZ) cermet anodes for solid oxide fuel cells can improve anode performance provided that the infiltrated nanoparticles on YSZ connect to form conducting pathways and the Ni nanoparticles do not coarsen significantly. This study explores liquid phase co-infiltration of Ni with mixed conducting oxides, the latter providing microstructural stability and conductive pathways between Ni nanoparticles. Two mixed conducting oxides have been studied: Gd 0.1 Ce 0.9 O 2-δ (GDC), a predominantly ionic conductor, and La 0.6 Sr 0.3 Ni 0.15 Cr 0.85 O 3-δ (LSNC), a predominantly electronic conductor. Experimental results show that both oxides improve the nickel nanoparticle stability and charge transfer kinetics. However, the electrochemical performance of the Ni-GDC-infiltrated electrode is much better than that of the Ni-LSNC-infiltrated electrode. This is attributed to the citrate–nitrate combustion reaction required to form LSNC, which fills the pores of the anode and inhibits gas diffusion, reducing the performance of the Ni-LSNC-infiltrated electrode.

25 ENERGY STORAGE↗
DOE OSTI2019

Shape retention and infiltration height in complex WC-Co parts made via binder jet of WC with subsequent Co melt infiltration

Additive manufacturing (AM) of complex tungsten carbide-cobalt (WC-Co) parts was achieved using binder jet additive manufacturing (BJAM) of WC powders followed by Co infiltration. The intent of the study is to explore the shape retention, infiltration height, and properties of parts made with this method. Using BJAM with infiltration of the metal phase can limit shrinkage and grain growth in ceramic-metal (cermet) composites compared to other additive manufacturing (AM) methods. Knowledge of previous infiltration studies was used to help process parts to imitate production of parts. The properties such as density, microstructure, grain size, and hardness of the parts are characterized along the infiltration height. Fracture toughness is measured where applicable. Furthermore, this approach has the potential to achieve highly dense WC-Co parts that are net-shaped with some ternary phase and z-direction distortion.

36 MATERIALS SCIENCE↗
DOE OSTI2017

A highly scalable spray coating technique for electrode infiltration: Barium carbonate infiltrated La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ perovskite structured electrocatalyst with demonstrated long term durability

Barium carbonate (BaCO 3 ) nanoparticles have demonstrated excellent catalytic activity for the oxygen reduction reaction by spray coating onto La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) and LSCF-SDC (Sm 0.2 Ce 0.8 O 2-δ ) cathode materials. In this work, barium acetate solutions were modified by a surfactant to lower the surface tension and decrease the contact angle on LSCF which is a benefit for the infiltration process. In the LSCF electrode, BaCO 3 nano-particles exhibited significant interfacial contact with LSCF particles by the spray coating technique. As a result, the polarization resistance of BaCO 3 infiltrated LSCF was reduced from 2.5 to 1.2 Ωcm 2 at 700 °C. In addition, commercial full cell SOFCs with BaCO 3 infiltrated LSCF-SDC cathodes also demonstrated higher performance due to the reduced cathode resistance. At 750 °C, the electrode overpotential of the BaCO3 infiltrated cell was much lower than that of baseline cell during long term testing (500 hours). The polarization resistance of the BaCO 3 infiltrated LSCF-SDC electrode only increased by 1.6% after 500 hours. This work demonstrated a highly scalable spray coating process of a promising electrocatalyst (BaCO 3 ) with excellent long-term stability for the oxygen reduction reaction.

42 ENGINEERING↗
DOE OSTI2020

Enhancement of Ni–(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 fuel electrode performance by infiltration of Ce 0.8 Gd 0.2 O 2–δ nanoparticles

This paper addresses the use of Ce 0.8 Gd 0.2 O 2–δ (GDC) infiltration into the Ni–(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 (YSZ) fuel electrode of solid oxide cells (SOCs) for improving their electrochemical performance in fuel cell and electrolysis operation. Although doped ceria infiltration into Ni–YSZ has recently been shown to improve the electrode performance and stability, the mechanisms defining how GDC impacts electrochemical characteristics are not fully delineated. Furthermore, the electrochemical characteristics have not yet been determined over the full range of conditions normally encountered in fuel cell and electrolysis operation. Here we present a study of both symmetric and full cells aimed at understanding the electrochemical mechanisms of GDC-modified Ni–YSZ over a wide range of fuel compositions and temperatures. Single-step GDC infiltration at an appropriate loading substantially reduced the polarization resistance of Ni–YSZ electrodes in electrolyte-supported cells, as measured using electrochemical impedance spectroscopy (EIS) at various temperatures (600–800 °C) in a range of H 2 O–H 2 mixtures (3–90 vol% H 2 O). Fuel-electrode-supported cells had significant concentration polarization due to the thick Ni–YSZ supports. Here, a distribution of relaxation times approach is used to develop a physically-based electrochemical model; the results show that GDC reduces the reaction resistance associated with three-phase boundaries, but also appears to improve oxygen transport in the electrode. Increasing the H 2 O fraction in the H 2 –H 2 O fuel mixture reduced both the three-phase boundary resistance and the gas diffusion resistance for Ni–YSZ; with GDC infiltration, the electrode resistance showed less variation with fuel composition. GDC infiltration improved the performance of fuel-electrode-supported full cells, which yielded a maximum power density of 2.28 W cm –2 in fuel cell mode and an electrolysis current density at 1.3 V of 2.22 A cm –2 , both at 800°C.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Design of functional composite and all-inorganic nanostructured materials via infiltration of polymer templates with inorganic precursors

Robust and efficient approaches for the synthesis of materials with structure, porosity, and composition controlled at the nanoscale are highly important for a wide range of applications. Polymer templates are promising platforms to achieve such control. The self-assembly process of polymers provides access to diverse structures that can serve as templates for the deposition of inorganic materials. By infiltrating metal precursors from gas or liquid phases, using sequential infiltration synthesis (SIS) or swelling-based infiltration (SBI), respectively, into the polymer templates, one can create finely-tuned texturing of the surface films and bulk materials. In this review, we outline the specifics and dynamics of the polymer infiltration process and characterize the structure and properties of the synthesized materials. Finally, we highlight recent progress in implementing polymer infiltration-based nanoporous ceramics for many applications, including sensors, antireflective coatings, oil-absorbing foams, nanolithographic patterns, and catalytic materials.

Berman, Diana↗
DOE OSTI2021

Effect of Pressurization on Solid Oxide Cell Oxygen Electrodes: the Role of PrO x Nanoparticle Infiltration

Pressurization of solid oxide cells improves performance by reducing electrode polarization resistance (R P ) and facilitates system integration with balance of plant components such as pressurized storage tanks. However, there are few reports on pressurization effects for electrodes designed for low-temperature operation and utilizing infiltrated catalysts. Here we report an electrochemical impedance spectroscopy study of high performing oxygen electrode materials, SrTi 0.3 Fe 0.63 Co 0.07 O 3-∂ (STFC) and PrO x infiltrated STFC, for oxygen partial pressures ($p$ $o$ 2 ) from 0.1 to 8 atm and temperatures from 550 to 650 °C. decreases more with pressurization for STFC:PrO x , fitting well to with an exponent n~0.3, compared to n~0.25 for STFC. The combination of PrO x infiltration and pressurization yields a substantial R P decrease, e.g., at 600 °C by ~7 times from 0.36 Ω cm 2 at $p$ $o$ 2 = 0.2 atm for STFC to 0.055 Ω cm 2 at $p$ $o$ 2 = 4 atm for STFC:PrO x . Here, a transmission-line-based circuit model impedance fit reveals that the significant oxygen surface reaction (R surf ) resistance contribution decreases substantially with PrO x infiltration; and its $p$ $o$ 2 dependence become more pronounced, with n increasing from ~0.25 to ~0.5. R surf for STFC:PrO x decreases so much at elevated $p$ $o$ 2 that the electrode/electrolyte interface resistance dominates.

25 ENERGY STORAGE↗
DOE OSTI2016

Development of graphite foam infiltrated with MgCl 2 for a latent heat based thermal energy storage (LHTES) system

Thermal energy storage (TES) systems that are compatible with high temperature power cycles for concentrating solar power (CSP) require high temperature media for transporting and storing thermal energy. To that end, TES systems have been proposed based on the latent heat of fusion of the phase change materials (PCMs). However, PCMs have relatively low thermal conductivities. In this paper, use of high-thermal-conductivity graphite foam infiltrated with a PCM (MgCl2) has been investigated as a potential TES system. Graphite foams with two porosities were infiltrated with MgCl2. The infiltrated composites were evaluated for density, heat of fusion, melting/freezing temperatures, and thermal diffusivities. Estimated thermal conductivities of MgCl2/graphite foam composites were significantly higher than those of MgCl2 alone over the measured temperature range. Furthermore, heat of fusion, melting/freezing temperatures, and densities showed comparable values to those of pure MgCl2. Results of this study indicate that MgCl2/graphite foam composites show promise as storage media for a latent heat thermal energy storage system for CSP applications.

25 ENERGY STORAGE↗
DOE OSTI2020

Boosting solid oxide fuel cell performance via electrolyte thickness reduction and cathode infiltration

Increasing the power density and reducing the operating temperature of solid oxide fuel cells (SOFCs) is important for improving commercial viability. Here we discuss two strategies for achieving such improvements in Ni–YSZ supported SOFCs – electrolyte thickness reduction and cathode infiltration. Microstructural and electrochemical results are presented showing the effect of reducing YSZ/GDC electrolyte thickness from 8 to 2.5 μm, and the effect of PrO x infiltration into the LSCF–GDC cathode. Both of these measures are effective, particularly at lower temperatures, leading to an increase in the maximum power density at 650 °C from 0.4 to 0.95 W cm –2 , for example. Electrochemical impedance spectroscopy utilizing subtractive analysis shows that PrO x enhances the cathode charge transfer process. Reducing the electrolyte thickness reduces not only the cell ohmic resistance but also the electrode polarization resistance. Furthermore, the latter effect appears to be an artifact associated with a slight increase in the steam partial pressure at the anode due to minor gas leakage across the thinner electrolyte.

25 ENERGY STORAGE↗
DOE OSTI2021

Microstructural and infiltration properties of woven preforms during chemical vapor infiltration

Interface-resolved direct numerical simulations (DNSs) of chemical vapor infiltration (CVI) have been performed over a range of furnace-operating conditions (Thiele moduli) and for practical woven preform geometries. A level-set method is used to resolve the geometry of the initial preform at tow scale. The interface between the vapor and solid phase is then evolved in time through the entire CVI densification cycle, fully resolving the time-varying topology between the two phases. In contrast to previous level-set methods for CVI simulation, the physical reaction and diffusion processes govern the level-set movement in the current approach. The surface deposition kinetics is described by the usual one-step model. In this paper, the DNS data are used to study the evolving porosity, surface-to-volume ratio, and flow infiltration properties (permeability and effective diffusivities). Additionally, comparisons are made to popularly-assumed structure functions and the standard, Kozeny–Carmen porous media model commonly employed in modeled CFD simulations of CVI. The virtual DNS experiments reveal a Thiele modulus and preform geometry (fabric layup) dependence which the existing microstructural and infiltration models are not able to describe throughout the entire densification process. The DNS-based, woven geometry-specific correlations can be applied directly to mean-field, furnace-scale CFD simulations.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Acidity of surface-infiltrated binary oxides as a sensitive descriptor of oxygen exchange kinetics in mixed conducting oxides

Improving the kinetics of O 2 reduction on oxide surfaces is critical in many energy and fuel conversion technologies. Here we show that the acidity scale for binary oxides is a powerful descriptor for tuning and predicting oxygen surface exchange kinetics on mixed conducting oxides. By infiltrating a selection of binary oxides from strongly basic (Li 2 O) to strongly acidic (SiO 2 ) onto the surface of Pr 0.1 Ce 0.9 O 2-δ samples, it was possible to vary the chemical surface exchange coefficient k chem by 6 orders of magnitude, with basic oxides such as Li 2 O increasing k chem by nearly 1,000 times, with surface concentrations as low as 50 ppm impacting k chem . Strikingly, although the pre-exponential of k chem scales linearly with the acidity of the infiltrated binary oxide, there is nearly no change in the activation energy. Here, the origin of these dramatic changes is proposed to arise from the systematic increase in electron concentration at the Pr 0.1 Ce 0.9 O 2-δ surface with the decreasing acidity of the infiltrated binary oxide.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2016

Amorphous MoS 3 Infiltrated with Carbon Nanotubes as an Advanced Anode Material of Sodium-Ion Batteries with Large Gravimetric, Areal, and Volumetric Capacities

The search for earth-abundant and high-performance electrode materials for sodium-ion batteries represents an important challenge to current battery research. 2D transition metal dichalcogenides, particularly MoS2, have attracted increasing attention recently, but few of them so far have been able to meet expectations. In this study, it is demonstrated that another phase of molybdenum sulfide—amorphous chain-like MoS3—can be a better choice as the anode material of sodium-ion batteries. Highly compact MoS3 particles infiltrated with carbon nanotubes are prepared via the facile acid precipitation method in ethylene glycol. Compared to crystalline MoS2, the resultant amorphous MoS3 not only exhibits impressive gravimetric performance—featuring excellent specific capacity (≈615 mA h g-1), rate capability (235 mA h g-1 at 20 A g-1), and cycling stability but also shows exceptional volumetric capacity of ≈1000 mA h cm-3 and an areal capacity of >6.0 mA h cm-2 at very high areal loadings of active materials (up to 12 mg cm-2). The experimental results are supported by density functional theory simulations showing that the 1D chains of MoS3 can facilitate the adsorption and diffusion of Na+ ions. At last, it is demonstrated that the MoS3 anode can be paired with an Na3V2(PO4)3 cathode to afford full cells with great capacity and cycling performance.

Ye, Hualin↗
DOE OSTI2017

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful, and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition, and selective swelling of the of the polymer template. We show that the refractive index of Al2O3 can be lowered from 1.76 down to 1.1 using this method. The thickness of the Al2O3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband antireflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.

Berman, Diana↗
DOE OSTI2016

Meteoric fluid infiltration in crustal-scale normal fault systems as indicated by δ 18 O and δ 2 H geochemistry and 40 Ar/ 39 Ar dating of neoformed clays in brittle fault rocks

Both the sources and pathways of fluid circulation are key factors to understanding the evolution of low-angle normal fault (LANF) systems and the distribution of mineral deposits in the upper crust. In recent years, several reports have shown the presence of meteoric waters in mylonitic LANF systems at mid-crustal conditions. However, a mechanism for meteoric water infiltration to these mid-crustal depths is not well understood. Here we report paired δ 18 O and δ 2 H isotopic values from dated, neoformed clays in fault gouge in major detachments of the southwest United States. Furthermore, these isotopic values demonstrate that brittle fault rocks formed from exchange with pristine to weakly evolved meteoric waters at multiple depths along the detachment. 40 Ar/ 39 Ar dating of these same neoformed clays constrains the Pliocene ages of fault-gouge formation in the Death Valley area. The infiltration of ancient meteoric fluids to multiple depths in LANFs indicates that crustal-scale normal fault systems are highly permeable on geologic timescales and that they are conduits for efficient, coupled flow of surface fluids to depths of the brittle-plastic transition.

58 GEOSCIENCES↗