Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “coating”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Infrared fluorescent coatings

The present invention provides for a composition comprising a pigment, wherein the composition is suitable for coating a surface that is, or is expected to be, exposed to the sun. The pigment comprises particles that fluoresce in sunlight, thereby remaining cooler in the sun than coatings pigmented with non-fluorescent particles. The particles comprise solids that fluoresce or glow in the visible or near infrared (NIR) spectra, or that fluoresce when doped. Suitable dopants include, but are not limited to, ions of rare earths and transition metals. A coating composition includes: (i) a film-forming resin; (ii) an infrared reflective pigment; and (iii) an infrared fluorescent pigment different from the infrared reflective pigment. When the coating composition is cured to form a coating and exposed to radiation comprising fluorescence-exciting radiation, the coating has a greater effective solar reflectance (ESR) compared to the same coating exposed to the radiation comprising fluorescence-exciting radiation except without the infrared fluorescent pigment. A multi-layer coating including the coating composition, and a substrate at least partially coated with the coating composition is also disclosed. A method of reducing temperature of an article includes applying the coating composition to at least a portion of the article.

Zalich, Michael Andrew↗
DOE OSTI2020

Characterization of Rare-earth Doped Thermal Barrier Coatings for Phosphor Thermometry

Thermal Barrier Coatings have been extensively used to protect and insulate the metallic components in turbine engines from extreme environments to achieve higher turbine inlet temperatures, resulting in an increase in combined engine cycle efficiency, lowering NOx emissions and fuel consumption. Additionally, as the major failure mechanisms determining lifetime are thermally activated during engine operation, uncertainty in temperature measurements affects lifetime prediction. Early detection of Thermal Barrier Coatings spallation symptoms, associated with local delamination induced temperature changes, can reduce forced engine outages. Further improvements are envisioned with the development of more reliable measurement techniques. For this purpose, Phosphor Thermometry has been considered a promising method for precision monitoring of turbine blade coatings that contain embedded phosphor dopants. In this work, a modified four-flux Kubelka-Munk model for luminescent rare-earth doped Thermal Barrier Coating configurations supported the design and the fabrication of viable sensing coatings for potential industrial implementation. Phosphor Thermometry instrumentation was developed with the objective of expanding capabilities of the technique, using a synchronized acquisition method on sensing coatings. Experiments on an innovative Erbium-Europium co-doped Yttria-Stabilized Zirconia coating have demonstrated the effectiveness of this advanced Phosphor Thermometry instrument with enhanced sensitivity and extended temperature range. Delamination progression monitoring was achieved for the first time using a Thermal Barrier Coating configuration subjected to indentation that includes a thin luminescent layer deposited on the surface and associating the multi-layer configuration with a predictive model that evaluates the advancement of the degradation of the coatings. To further ensure the integrity of the phosphor doped coatings, synchrotron X-ray diffraction was performed to characterize the specific residual strains and thermal expansion of the materials, determining mechanical robustness and compatibility with state-of-the-art Thermal Barrier Coatings. The outcomes of this work pave the way for in-situ temperature measurements on phosphor-doped turbine blade coatings with increased performance and accuracy.

Fouliard, Quentin↗
DOE OSTI2022

Mechanical and tribological properties of anodic Al coatings as a function of anodizing conditions

Enhanced wear and corrosion resistance properties are vital for numerous functional and decorative applications. Anodizing is a process frequently used to generate stable oxide coatings on metal surfaces, including aluminium (Al). In this work, we present an evaluation of process variables for optimized anodized coating properties using existing methods and as a baseline for novel coating development. A representative relatively pure Al alloy was chosen as a model system with a goal of finding conditions to achieve high wear coatings with retained ductility. AA5052 alloy coupons were anodized in two different electrolytes (sulfuric and phosphoric acid) to study the effects of anodizing conditions on the mechanical and tribological properties of the anodic coatings. Porosity was evaluated with microscopy, coating hardness was determined via nanoindentation, and tribological properties were characterized using a pin-on-disk tribometer. These measurements were correlated and a loading evaluation was performed to assess the optimum nanoindentation parameters for the use of representative coupons without the need for special processing prior to anodizing. The porosity and coating thickness were found to depend on the anodizing time and the type of electrolyte. Thicker and harder anodic coatings were generated in sulfuric acid compared to phosphoric acid. Porosity studies of the anodic coatings generated in phosphoric acid revealed that coating porosity decreased as the anodizing time increased. Both electrolytes generated anodic coatings with improved tribological properties (friction coefficient and dimensional wear rate), and an optimum processing time was identified for best wear properties.

36 MATERIALS SCIENCE↗
NASA NTRS2019

Fatigue Behavior of Coated Titanium Alloys

Advanced multi-component TiAlCrTaSiN-based multilayered coatings were developed and processed onto Ti-6Al-4V (Ti-6-4) and GammaMet PX (GMPX or TiAl) alloys by a magnetron-enhanced physical vapor deposition technique. The coatings have recently been in development with the goal of improving advanced titanium alloy, turbine engine component durability and oxidation-erosion resistance. In this work, the performance of the multi-component coating system (including the outer layer nitride based coating and inner TiAlCrSi oxidation barrier bond coat) was studied, and the coating's influence on the fatigue behavior of the titanium-based alloys were compared. Although the multi-component coating was initially optimized to improve the coating's high temperature oxidation and erosion resistance, the lower ductility nitride-based coating needs further work on microstructure or composition to improve its mechanical stress resistance and strain tolerance for use in cyclically loaded, turbine blade operating conditions. This is particularly true for GMPX and other γ-TiAl alloys because these intermetallic titanium alloys have limited ductility and are very sensitive to defects such as coating cracks. However, the inner layer TiAlCrSi-coating had better adhesion and ductility, and may be a suitable choice to improve the oxidation resistance of titanium alloys.

Oxidation Barrier Coatings↗
DOE OSTI2021

Long-term thermal aging of parylene conformal coating under high humidity and its effects on tin whisker mitigation

Usage of pure tin (Sn) or Sn-rich alloy in electronics industry is growing, which makes them more susceptible to the spontaneous growth of tin whiskers. The risk of having these whiskers can be dramatically mitigated by applying a conformal coating provided that it not only possesses excellent mechanical and adhesion properties but also maintains these properties throughout their service. Parylene C is commonly used as a conformal coating because of its favorable mechanical and physical properties, as well as superior conformal coverage. The purpose of this paper is to investigate the degradation of parylene C coating during the thermal aging in high humidity environment (85°C/85% relative humidity for up to 5000hrs) and its effect on the tin whisker mitigation capacity. It was observed that during aging at high temperature and high humidity (HTHH) environment, the oxidation occurs at early times, followed by bond scission, resulting in the loss of strength of the coating. Thinner parylene coating (12.5-μm-thick) had better coating adhesion on the silane-treated tin surface, so provided the better protection for tin whisker penetration than the thicker counterpart (25-μm-thick). After 2500hrs of aging, due to the degradation of the silane agent at the tin/parylene interface, the adhesion of the parylene coating was significantly weakened on the tin surface, which resulted in extensive corrosion of the tin solderpads. The loss of adhesion of the coating, along with the corrosion of the tin surface facilitated the tin whisker nucleation at the interface while the loss of mechanical strength and the brittleness made the coating easily penetrated by the growing whiskers. Tin whiskers with a smaller diameter were buckled and grew along the delaminated region while those with a larger diameter penetrated and continued to grow through the coating. Hence, the effectiveness of the parylene coatings on tin whisker mitigation is significantly reduced under long exposure to such high temperature and high humidity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stainless Steel Coating Test Report

A process was developed to coat 316L stainless steel pieces having very low levels of fixed contamination on their surface (~100 dpm/100 cm²). The coating process served to significantly decrease the likelihood of any fixed contamination becoming loose contamination due to physical shocks. Prior to coating, the stainless steel was etched with a commercial methane sulfonic acid (MSA) solution in a heated ultrasonic bath, rinsed with deionized water, cleaned with a basic detergent solution, and then rinsed with deionized water. The MSA etched the surface of the stainless-steel pieces, creating a more favorable surface on which the coating could adhere. Due to the short timeline of the project, only commercially available clear coating products were considered. The clear coating had to be wear-resistant, shock resistant, radiation resistant, and have high adhesion to the surface of the stainless steel. Adhesion of coatings to stainless steel is notoriously difficult. A commercial, high molecular weight polymer coating was found that met these requirements. The adhesion properties of this coating to stainless steel are very good, and are significantly improved by the etching process. The etching process results in a higher surface area that is free of debris and other residues, making the surface much more wetable, and at the same time creating a favorable surface topography for adhesion. The polymer in its uncured form is a low viscosity liquid. It can be applied by brush or pipette, and it cures in air alone, but heat is required to speed up curing and attain the highest performance of the cured polymer. As the project progressed, the project team became interested in the composition of the selected commercial polymer coating, and in ways that this polymer coating could be made more wear resistant and potentially more radiation resistant. Nano-particle addition was chosen as the preferred way to achieve higher performance. Therefore, a series of tests were planned and performed. This report summarizes these tests, and presents the results.

36 MATERIALS SCIENCE↗
DOE OSTI2024

MODELING AND METHOD FOR OPTICAL PERFORMANCE OF A RECEIVER COATING AND ITS DEGRADATION DUE TO OPERATION

The optical properties of the coating used on a concentrated solar power (CSP)’s receiver directly impact the performance of the power plant. Receiver coatings are designed to absorb as much heat as possible and transfer it to the circulating fluid. Over time, the absorptivity of the receiver coating degrades due to environmental and operational conditions. This project aims to (1) create a test apparatus that allows coatings to undergo accelerated lifetime testing under conditions that mimic what the coating will experience on-tower; and (2) develop a mathematical model that based on the test data predicts absorptivity over time. To create the mathematical model, samples of BrightSource Energy’s Gen1 and Gen2 coatings were tested first looking at individual failure modes (such as high temperature cycling) and then for combined failure modes in the newly developed apparatus. In addition to taking optical measurements, the samples were destroyed to allow for metalogical evaluation to understand what was happening on a microscopic level. Pre-existing models from the literature that describe accelerated testing as well as individual phenomena observed in the coating were then combined to create the model. Additionally, the Gen2 and Gen3 coatings are being testing at the Plataforma Solar de Almería (PSA) facility in Almeria, Spain to confirm that the apparatus test results are similar to those received on-sun. (PSA’s facility closely mimics on-tower conditions). The goal is to enable industry players to test coatings using the new apparatus, gather absorptivity measurements (without needing to destroy samples), and input the information into the model to determine how the coating will perform over time, thus allowing the optical performance of coatings to be compared even before they are used on-tower. The model will be publicly available by the end of the project (currently projected as December 2024).

14 SOLAR ENERGY↗
DOE OSTI2021

CFD/FEA Co-Simulation Framework for Analysis of the Thermal Barrier Coating Design and Its Impact on the HD Diesel Engine Performance

Thermal barrier coatings (TBCs) have been investigated both experimentally and through simulation for mixing controlled combustion (MCC) concepts as a method for reducing heat transfer losses and increasing cycle efficiency, but it is still a very active research area. Early studies were inconclusive, with different groups discovering obstacles to realizing the theoretical potential. Nuanced papers have shown that coating material properties, thickness, microstructure, and surface morphology/roughness all can impact the efficacy of the thermal barrier coating and must be accounted for. Adding to the complexities, a strong spatial and temporal heat flux inhomogeneity exists for mixing controlled combustion (diesel) imposed onto the surfaces from the impinging flame jets. In support of the United States Department of Energy SuperTruck II program goal to achieve 55% brake thermal efficiency on a heavy-duty diesel engines, this study sought to develop a deeper insight into the inhomogeneous heat flux from mixing controlled combustion on thermal barrier coatings and to infer concrete guidance for designing coatings. To that end, a co-simulation approach was developed that couples high-fidelity computational fluid dynamics (CFD) modeling of in-cylinder processes and combustion, and finite element analysis (FEA) modeling of the thermal barrier-coated and metal engine components to resolve spatial and temporal thermal boundary conditions. The models interface at the surface of the combustion chamber; FEA modeling predicts the spatially resolved surface temperature profile, while CFD develops insights into the effect of the thermal barrier coating on the combustion process and the boundary conditions on the gas side. The paper demonstrates the capability of the framework to estimate cycle impacts of the temperature swing at the surface, as well as identify critical locations on the piston/thermal barrier coating that exhibit the highest charge temperature and highest heat fluxes. In addition, the FEA results include predictions of thermal stresses, thus enabling insight into factors affecting coating durability. An example of the capability of the framework is provided to illustrate its use for investigating novel coatings and provide deeper insights to guide future coating design.

42 ENGINEERING↗
DOE OSTI2022

Hydriding, Oxidation, and Ductility Evaluation of Cr-Coated Zircaloy-4 Tubing

Accident-tolerant fuel concepts have been developed recently in diverse research programs. Recent research has shown clear advantages of Cr-coated Zr cladding over bare cladding tubes regarding oxidation behavior under the design basis loss-of-coolant accident condition. However, limited data are available about the hydriding behavior of the Cr coating. For that purpose, Cr-coated Zricaloy-4 tubes were tested to investigate the effects of hydriding, oxidation, and postquench ductility behavior on coated Zr cladding. A high-power impulse magnetron sputtering (HiPIMS) process was used to produce a high-density coating on the Zircaloy-4 tube surface. Coated and uncoated Zircaloy-4 tube specimens underwent one-sided hydriding in a tube furnace filled with pure hydrogen gas at 425 °C. The tubing specimen ends were sealed with Swagelok plugs before the hydriding runs. For uncoated specimens, H analysis of the hydrided specimens indicated that the H content increased as the test time and initial pressure increased. However, almost no change was observed for the coated specimens that were hydrided under the same test conditions. After one-sided hydriding, the hydrided coated and uncoated specimens were exposed to steam at high temperatures for two-sided oxidation studies to simulate accident conditions. The coated specimens showed a slower oxidation: oxygen pickup was 50% lower than the uncoated specimens tested under the same conditions. Ring compression testing was performed to evaluate the embrittlement behavior of the Cr-coated specimens after hydriding and oxidation. The results indicated that the HiPIMS coating provides excellent protection from hydriding and oxidation at high temperatures.

36 MATERIALS SCIENCE↗
NASA NTRS2014

Black Molecular Adsorber Coatings for Spaceflight Applications

The molecular adsorber coating is a new technology that was developed to mitigate the risk of on-orbit molecular contamination on spaceflight missions. The application of this coating would be ideal near highly sensitive, interior surfaces and instruments that are negatively impacted by outgassed molecules from materials, such as plastics, adhesives, lubricants, epoxies, and other similar compounds. This current, sprayable paint technology is comprised of inorganic white materials made from highly porous zeolite. In addition to good adhesion performance, thermal stability, and adsorptive capability, the molecular adsorber coating offers favorable thermal control characteristics. However, low reflectivity properties, which are typically offered by black thermal control coatings, are desired for some spaceflight applications. For example, black coatings are used on interior surfaces, in particular, on instrument baffles for optical stray light control. Similarly, they are also used within light paths between optical systems, such as telescopes, to absorb light. Recent efforts have been made to transform the white molecular adsorber coating into a black coating with similar adsorptive properties. This result is achieved by optimizing the current formulation with black pigments, while still maintaining its adsorption capability for outgassing control. Different binder to pigment ratios, coating thicknesses, and spray application techniques were explored to develop a black version of the molecular adsorber coating. During the development process, coating performance and adsorption characteristics were studied. The preliminary work performed on black molecular adsorber coatings thus far is very promising. Continued development and testing is necessary for its use on future contamination sensitive spaceflight missions.

adsorption↗
NASA NTRS2014

Black Molecular Adsorber Coatings for Spaceflight Applications

The molecular adsorber coating is a new technology that was developed to mitigate the risk of on-orbit molecular contamination on spaceflight missions. The application of this coating would be ideal near highly sensitive, interior surfaces and instruments that are negatively impacted by outgassed molecules from materials, such as plastics, adhesives, lubricants, epoxies, and other similar compounds. This current, sprayable paint technology is comprised of inorganic white materials made from highly porous zeolite. In addition to good adhesion performance, thermal stability, and adsorptive capability, the molecular adsorber coating offers favorable thermal control characteristics. However, low reflectivity properties, which are typically offered by black thermal control coatings, are desired for some spaceflight applications. For example, black coatings are used on interior surfaces, in particular, on instrument baffles for optical stray light control. Similarly, they are also used within light paths between optical systems, such as telescopes, to absorb light. Recent efforts have been made to transform the white molecular adsorber coating into a black coating with similar adsorptive properties. This result is achieved by optimizing the current formulation with black pigments, while still maintaining its adsorption capability for outgassing control. Different binder to pigment ratios, coating thicknesses, and spray application techniques were explored to develop a black version of the molecular adsorber coating. During the development process, coating performance and adsorption characteristics were studied. The preliminary work performed on black molecular adsorber coatings thus far is very promising. Continued development and testing is necessary for its use on future contamination sensitive spaceflight missions.

adsorption↗
NASA NTRS2014

NASA's Advanced Environmental Barrier Coatings Development for SiC/SiC Ceramic Matrix Composites: Understanding Calcium Magnesium Alumino-Silicate (CMAS) Degradations and Resistance

Environmental barrier coatings (EBCs) and SiCSiC ceramic matrix composites (CMCs) systems will play a crucial role in next generation turbine engines for hot-section component applications because of their ability to significantly increase engine operating temperatures with improved efficiency, reduce engine weight and cooling requirements. The development of prime-reliant environmental barrier coatings is essential to the viability and reliability of the envisioned CMC engine component applications, ensuring integrated EBC-CMC system durability and designs are achievable for successful applications of the game-changing component technologies and lifing methodologies.This paper will emphasize recent NASA environmental barrier coating developments for SiCSiC turbine airfoil components, utilizing advanced coating compositions, state-of-the-art processing methods, and combined mechanical and environment testing and durability evaluations. The coating-CMC degradations in the engine fatigue-creep and operating environments are particularly complex; one of the important coating development aspects is to better understand engine environmental interactions and coating life debits, and we have particularly addressed the effect of Calcium-Magnesium-Alumino-Silicate (CMAS) from road sand or volcano-ash deposits on the durability of the environmental barrier coating systems, and how the temperature capability, stability and cyclic life of the candidate rare earth oxide and silicate coating systems will be impacted in the presence of the CMAS at high temperatures and under simulated heat flux conditions. Advanced environmental barrier coating systems, including HfO2-Si with rare earth dopant based bond coat systems, will be discussed for the performance improvements to achieve better temperature capability and CMAS resistance for future engine operating conditions.

Environmental barrier coatings↗
NASA NTRS2018

Fatigue Life of a NiCr-Coated Powder Metallurgy Disk Superalloy After Varied Processing and Exposures

A protective ductile NiCr coating has shown promise to mitigate oxidation and corrosion attack on superalloy disk alloys. The effects of this coating on fatigue life and failure modes of the disk superalloy are an important concern. The objective of this study was to investigate the fatigue life and failure modes of disk superalloy specimens protected by this coating, using varied pre-coating and post-coating processes. Cylindrical gage fatigue specimens of a powder metallurgy-processed disk superalloy were grit blast or wet blast before being coated with a ductile NiCrY coating, then shot peened at low or medium levels after coating. All were then heat treated, some exposed, and finally all were subjected to fatigue at high temperature. The effects of varied pre-coating treatment, post-coating shot peening, and oxidation plus hot corrosion exposures on fatigue life with the coating were compared.

coating↗
DOE OSTI2021

PREPARATION OF CLAY-COATED GLASS SURFACES FOR MICROFLUIDICS-BASED STUDY ON CLAY-FLUID INTERACTIONS

Unique characteristics of clay, even though make any clay abundant shales a good source of adsorbed gas, make them equally difficult to produce. The clay-water interaction can cause significant swelling and fines migration in the shale formation, both of which can significantly impair the overall hydrocarbon recovery from shale. Geomaterial micromodels, developed by functionalizing traditional glass or PDMS surface with geomaterials (e.g., calcite, quartz, clay) can represent the physico-chemical properties of the natural porous media and have been used during the last few years to understand and evaluate the solid-fluid physicochemical interactions. This study focuses on developing a clay-coated geomaterial surface and investigates the effect of base fluid's salinity on clay adsorption to the glass surface. Glass capillary tubes and straight channel borosilicate glass micromodels are coated with Illite clay minerals to represent the pore-scale clay chemistry of Caney Shale, a Mississippian unconventional play in Southern Oklahoma, USA. 10 wt.% of Illite clay slurries made with brines of four different salinities are used to coat the glass-capillary tubes to understand the effect of salinity in clay adsorption on the glass surface and overall coating quality. To achieve a stable coating and evaluate the impact of heat treatment on coating's stability, straight channel glass flow cells coated with Illite clay are heat-treated at low (25 °C) and high temperature (125 °C). Dynamic flooding tests were carried out with brines on the coated surface to evaluate the stability of the coating. The experiments' outcome indicated a strong relationship between the brine's salinity and the adsorption of clay particles on the glass surface. An increase in brine concentration resulted in improved adsorption of clay particles on the glass surface. Experiments involving heat treating the glass surface following the coating demonstrated significant improvement in the stability of the coating.

02 PETROLEUM↗
DOE OSTI2022

Photovoltaic module antireflection coating degradation survey using color microscopy and spectral reflectance

Abstract Commercial antireflective coatings (ARCs) on photovoltaic (PV) module glass can improve module power by 2.5%–3.0%, but their long‐term field performance requires additional study. In this paper, we investigate ARC performance on fielded modules using two nondestructive techniques: reflectance spectroscopy and RGB microscopy, finding a large variation in coating durability and performance. For new coatings, the fleet average nominal power enhancement is 2.8%. This power enhancement is observed to degrade at approximately −0.05%/year absolute over the first 8 years of fielding in arrays that are not regularly cleaned. Interferometry and imaging results imply that coating loss for these modules is due to slow chemical thinning of the initial 125 nm thick coating by 1.4 to 5.0 nm/year. Due to the physics of interference coatings, the performance loss is projected to accelerate as the coating is further thinned, resulting in a coating lifetime (time to 80% of initial performance) of 7.5 to 25 years. At the higher 5.0 nm/year coating loss rates, we estimate that −0.14%/year power degradation of the module can be attributed solely to ARC degradation over the first 20 years. Extreme coating loss is observed on some modules where after 8 years fielding, the coating can be completely removed with a single wet wipe with a lens tissue. A case study is also presented comparing ARC and noncoated modules installed at a single site in 2013. We find that the ARC modules have a 2.6% higher soiling power loss than the noncoated modules; this exceeds the ARC power enhancement of 2.4% and leads to the surprising conclusion that the ARC lowers production for modules in this location due to increased soiling. These results demonstrate that RGB microscopy is a powerful, field‐capable, and quantitative characterization technique for assessing degradation of PV module ARCs.

Karin, Todd↗
DOE OSTI2020

High-efficiency, air-stable manganese–iron oxide nanoparticle-pigmented solar selective absorber coatings toward concentrating solar power systems operating at 750 °C

Solar selective absorber coating with long-term thermal stability at high temperatures ≥750 °C in air is an important component to reduce the levelized cost of energy (LCOE) of concentrating solar power (CSP) systems toward 50% power efficiency and dispatchable solar electricity. Conventionally, solar spectral selectivity requires multilayer-interference coatings implemented by stringently controlled vacuum deposition, and these coatings degrade significantly at >700 °C in air. Herein, we established a quantitative design approach and demonstrated a proof-of-concept air-stable, manganese–iron oxide nanoparticle (NP)-pigmented solar selective coatings with a high solar absorptance of ~93%, a relatively low thermal emittance of ~52%, and an optical-to-thermal energy conversion efficiency >89% under 1,000× solar concentration at 750 °C toward Generation 3 CSP systems. These coatings demonstrate spectral selectivity using cost-effective spray coating approach, a notable improvement over conventional vacuum-deposited, multilayer solar selective coatings for low-cost, high-efficiency solar thermal receivers. In contrast to the thermal degradation of spectrally non-selective benchmark Pyromark 2500 coatings at 750 °C in air, the solar absorptance of the MnFe 2 O 4 -pigmented coatings on stainless steel 310 (SS 310) substrates is increased to ~92.9% and the optical-to-thermal energy conversion efficiency is improved to 89.7% after serving at 750 °C in air for 700 h. X-ray diffraction results reveal that this improvement is due to the transformation of MnFe 2 O 4 NPs into more thermodynamically stable, non-stoichiometric manganese-rich manganese ferrite and iron-rich manganese–iron oxide phases after 500 h aging at 750 °C. For >1,000 h-endurance testing at 750 °C in air and the subsequent 19 day-night thermal cycling between 750 °C (12 h/cycle) and 25 °C (12 h/cycle) on SS 310 substrates, the thermal degradation is mainly due to the CrO x microflake formation from SS 310 substrates rather than the coatings, which can be suppressed by preoxidizing the surface of SS 310. With lower emittance matrix material and further optimization of pigment NP stoichiometry, concentration, and coating thickness, it is promising to achieve an optimized thermal efficiency ≥92.5% with long-term thermal stability at 750 °C for Generation 3 CSP systems.

14 SOLAR ENERGY↗
DOE OSTI2022

Graphene coating on silicon anodes enabled by thermal surface modification for high-energy lithium-ion batteries

Silicon is a high-energy density anode material for lithium-ion batteries, but it possesses shortcomings such as poor electronic conductivity, interfacial instability and mechanical fracturing that hinder its battery cycling. Carbon coating has been an important strategy for stabilizing silicon anodes, but the effects of the silicon surface properties on carbon coating morphology and the consequent silicon cycling stability have not been clearly elucidated. Herein, we find that thermal oxidation of the silicon anodes followed by chemical vapor deposition of carbonaceous precursors leads to a well-ordered graphene coating, whereas disordered graphite coating is formed on the native silicon surface. Graphene-coated silicon exhibits superior cycling performance, retaining a discharge capacity of ~1300 mAh g -1 after 300 cycles, whereas the disordered graphite-coated silicon suffers continuous degradation, retaining only~600 mAh g -1 after 300 cycles. Cryogenic electron microscopy reveals the mechanism behind the difference in cycling stabilities; graphene coated silicon is able to withstand the large mechanical strains induced during extended cycling, whereas disordered graphite coating is ruptured, exposing silicon surfaces to the electrolyte, leading to extensive buildup of SEI and poor cycling performance. Characterization of the silicon surface reveals that thermal treatment yields an oxygen-rich surface layer, which is hypothesized to play a decisive role in dictating the carbon coating. This work highlights the effect of silicon surface properties on carbon coating microstructure, and presents thermal treatment as a facile avenue to attain graphene coating on silicon anodes.

25 ENERGY STORAGE↗
DOE OSTI2022

Removable, Sequestration Coatings for Mitigating Hazardous Contaminants Related to Deactivation and Decommissioning Activities

This project is a collaborative effort between InnoSense LLC (ISL) and Oak Ridge National Laboratory (ORNL) aimed at mitigating the mercury (Hg) contamination problem at the Y-12 National Security Complex (NSC). The report summarizes the research and technology development work of the Phase IIB Project, led by Dr. Uma Sampathkumaran at ISL for the period of July 31, 2017–October 31, 2021. The Y-12 site cleanup includes technologies for safe and cost-effective facility demolition, soil remediation, and on-site treatment and disposal of mercury bearing wastes. One of the technology demonstration goals was a reactive strippable coating for targeted pre-demolition and de-contamination to limit Hg mobilization and the volume of debris requiring treatment for disposal. Toward this, ISL has developed a water-based reactive strippable coating (Trap & See-Hg™) to sequester elemental Hg(0) and mercuric Hg(II) species in the coating. The coating provides multiple benefits including (1) Hg vapor suppression, (2) sealing in the hazardous contaminants, (3) visually locating the contaminant through color changes, and (4) remediating the contaminated surfaces upon coating removal. Through collaboration between ORNL and ISL in Phase II work, the team successfully demonstrated the Trap & See-Hg technology to (1) visually locate the presence of Hg on concrete, soil and drywall surfaces, (2) effectively sequester all mercury species (elemental, soluble and insoluble Hg) from lab-generated and ex-situ soil and brick/rubble samples collected from the Y 12 site with 80 to 95% efficiency to capture/reduce Hg vapor concentration, (3) be applied by manual and robotic spray applicators and cure at room ambient, (4) remain a cohesive and peelable coating upon drying, and (5) sequester Hg0 from walls in the alpha-2 building basement at Y-12 during a small scale in-situ field trial. In Phase IIB, ISL’s effort was focused on refining the coating formulations with additives containing passive and reactive sorbents, colorimetric indicator, and thixotropic agents to achieve the desired performance. The paints were then evaluated at ORNL for applicability to metal and concrete surfaces of different sizes and shapes, and soil rubble, Hg-sorption capacity and achieving sag-free coating on surfaces when applied by a manual spray applicator. Ambient cure of the coating resulted in a dry thickness of 16–20 mil. The coatings were removed from smooth or rough surfaces with low to moderate force. Both lab-generated Hg-contaminated samples and soil and brick/rubble samples containing a range of Hg concentrations (collected from the Y-12 site by UCOR) were used in this project. Optimized formulations were applied to these samples and evaluated for ability to suppress Hg vapors, sequester Hg 0 and Hg(II) species and color mapping of mercury species on the test surface. The ORNL team initially identified three to four potential sites at Y-12 and ORNL for potential demonstration. However, the pandemic closed any possible avenues for on-site demonstration of the robotic spray applicator. The metal and concrete samples with low to high Hg content provided by UCOR from an ongoing demolition were subsequently used for ex-situ sample characterization and analysis at ORNL over a period of 25 days. The coatings suppressed Hg vapors with an efficiency of 95–99% from heavily contaminated metal and 60% from concrete substrate. Analysis of total Hg in the peeled paints indicates sorption capacities ranging from 12 µg Hg/g of paint from concrete to 1.2 mg Hg/g of paint from the metal substrates while peeled paints from soil samples could capture a total Hg from 2.3 mg Hg/g to 66 mg/g paint. Toxicity characteristic leaching procedure (TCLP) tests recovered total mercury leached at 0.15±0.0008 µg/L for concrete to 126.81±0.67 µg/L and 377.25±5.67 µg/L for the two metal substrates, to allow for informed decisions on downstream disposal considerations. Together, this Phase IIB demonstrated the potential value of the Trap & See-Hg for Hg uptake, vapor suppression, and color mapping, and may thus be used to enhance worker safety during site cleanup, facility demolition, and downstream waste disposal at Y-12 NSC.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗