Energy Materials 2017: Materials in Clean Power: Session I
Sponsored by: Chinese Society for Metals, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Sebastien Dryepondt, Oak Ridge National Laboratory; Zhengdong Liu, China Iron & Steel Research Institute Group; Jeffrey Fergus, Auburn University; Jeffrey Hawk, U.S. Department of Energy, National Energy Technology Laboratory; Ji Zhang, China Iron and Steel Research Institute Group

Monday 8:30 AM
February 27, 2017
Room: 15A
Location: San Diego Convention Ctr

8:30 AM  Invited
Creep-Fatigue-Oxidation Interactions under Fossil Energy Service Conditions: Sebastien Dryepondt1; Amit Shyam1; Sumit Bahl2; Charles Hawkins1; Dana McClurg1; 1Oak Ridge National Laboratory; 2Indian Institute of Science
    Increased deployment of intermittent renewable power generation requires fossil-fueled power plants to operate in cycling modes. Thermo-mechanical cycling will therefore be superimposed to creep loading and will lead to new creep-fatigue damages. Creep-fatigue tests were therefore conducted on Gr.91 steel, and showed a decrease of the number of cycles to failure with increasing hold time. Cyclic creep tests were also performed, with loading-unloading sequences every 10h. Load cycling resulted in an increase of the creep rate but had limited impact on the specimen lifetime. Finally, optical microscopy was used to measure crack growth during load-controlled fatigue testing at 550C. It was found that tensile hold times decreased the crack propagation rate. These results were used to improve modeling of Gr.91 lifetime under creep-fatigue conditions.

9:00 AM  
Microstructural Stability of High Cr Containing FeCrAl Alloys with Minor Alloying Additions: Yukinori Yamamoto1; Bruce Pint1; Benjamin Shassere2; Sudarsanam Babu2; 1Oak Ridge National Laboratory; 2University of Tennessee
    The effect of minor alloying additions on microstructural stability of Fe-30Cr-3Al-0.2Si-2Nb alloy was investigated. The additions of W, Mo, and Ti, substituting for Nb, were selected with guidance from thermodynamic calculations to control Fe2Nb Laves phase precipitation kinetics in the BCC-Fe matrix. These alloying additions lowered the solvus temperature to expand the process temperature window without decreasing the volume fraction of second-phase particles for precipitate strengthening at 700C. However, the alloying additions also resulted in coarsening the second-phase particles during aging at 700C. Optimization is required to balance the beneficial effects on the process window with the reduced particle size stability. The addition of Y stabilized the grain structure at elevated temperatures. This effect would aid in controlling grain size during hot-work processes, together with stabilizing the microstructure at the heat affected zone of weldments. Research sponsored by the Crosscutting Research Program, Office of Fossil Energy, U.S. Department of Energy.

9:20 AM  Invited
Effect of Pressure and Thermal Cycling on Compatibility in CO2 for Concentrated Solar Power Applications: Bruce Pint1; Robert Brese1; James Keiser1; 1Oak Ridge National Laboratory
    Initial experimental work at 700-800C is in progress to develop a lifetime model for supercritical CO2 compatibility for the 30 year duty life for high-efficiency concentrated solar power (CSP) applications at >700C. Nickel-base alloys 740H, 282 and 625 and Fe-base Sanicro 25 are being evaluated in 500-h cycles at 1 and 300 bar, and 10-h cycles in 1 bar industrial grade CO2. All of the alloys showed reasonably low reaction rates after 1000 h at 700, 750 and 800C and oxide thickness measurements were consistent with the mass change data. However, after ~1500 h of exposure in 10-h cycles, the Fe-base alloy has begun to show increased mass gain, particularly at 700C. Characterization of the internal attack as a function of gas pressure and temperature is in progress. Research sponsored by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Solar Energy Technology Program (SunShot Initiative).

9:50 AM  
The Composite Materials with Semiconductor and Ionic Conductor for Novel Low Temperature Solid Oxide Fuel Cells: Xunying Wang1; Bin Zhu1; 1Hubei University
    Solid oxide fuel cells (SOFCs) are currently attracting increased interest for their high energy conversion, fuel flexibility and cleanness. Conventional SOFCs employ yttria-stabilized zirconia (YSZ) as the electrolyte. The YSZ based SOFCs usually work at high temperature about 1000C to ensure the high ionic conductivity of YSZ. However, the high temperature condition leads to various problems including the high cost of materials, hardness in sealing, long start-up and shut-down time, which limits the commercialization of the SOFCs. Develop new electrolyte materials is an effective approach to reduce the operation temperature. In recent years, we have discovered that the composite materials with semiconductor and ionic conductor possess much better ionic conductivity than the pure ionic conductor when they were used as the electrolyte for the low temperature SOFCs. In this presentation, major study results about the composite materials based SOFCs will be discussed.

10:10 AM Break

10:30 AM  Invited
The Impacts of Alternative Fuels and Associated High Water Vapor Content Environments on the Stability and Aging of Turbine Hot-Section Materials: Daniel Mumm1; 1University of California-Irvine
    This talk will focus on evaluating the impacts of alternative fuels (coal-derived syngas, high-hydrogen content fuels, etc.) on the degradation of turbine hot-section materials. A primary focus is the role of associated elevated water vapor levels on the evolution of TGO and TBC systems. In studies of oxide growth on select bond coat materials, it is shown that the transient oxidation behavior is highly dependent upon the pH2O in the exposure environment. Subsequently, this talk will discuss the role of high pH2O environments on TBC materials stability. High temperature aging was performed on thermal-sprayed YSZ coatings in varying water vapor content environments. The phase evolution in different exposure environments illustrates that there is a distinct acceleration of aging and development of undesirable phases in elevated pH2O environments. The mechanisms underpinning this behavior, and implications for the durability of TBC coatings in turbines using high-hydrogen content fuels, will be discussed.

11:00 AM  
Early Stage Oxidation of Alloy 617 in CO2 Power Cycle Environments: Richard Oleksak1; John Baltrus1; Casey Carney1; Jinichiro Nakano1; Anna Nakano1; Gordon Holcomb1; Omer Dogan1; 1National Energy Technology Laboratory
    Next-generation power cycles based on supercritical CO2 (sCO2) have gained significant interest due to the potential for improved conversion efficiency and reduced cost. A primary barrier to adoption of this technology is the unknown oxidation/corrosion behavior of alloy materials in sCO2 environments. In this study, we investigated the oxidation/corrosion resistance of a candidate solid-solution strengthened Ni-base superalloy. Alloy 617 coupons were exposed to CO2 at 700 C and 1 bar for times ranging from 5 minutes to 500 hours to gain insight into the early stages of oxidation. Additional coupons were exposed for 500 hours at 700 C and 250 bar to assess the effects of pressure and the supercritical phase. The exposed samples were characterized using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to evaluate the suitability of this class of alloys for high temperature CO2 power cycle environments.

11:20 AM  
Nickel-doped Titania Nanotube Arrays and Their Application in Hydrogen Production: Joaquin Tirano Vanegas1; Hugo Zea1; Claudia Luhrs2; 1Universidad Nacional de Colombia; 2Naval Postgraduate School
    Highly ordered titanate nanotube arrays (TNTs) have been widely used for photoelectrochemical applications due to their electronic structure, light absorption properties and capability to generate charge carriers. In this study, to further improve the photoelectrocatalysis activity of TNTs, noble-metal-free, Ni-TNTs were prepared. Controlled morphology TNTs were produced through anodic oxidation of Ti or Ti-Ni alloy foils, followed by annealing in air or reducing atmospheres. Titania nanotube arrays were also loaded with Ni using other approaches, such as wet impregnation or simultaneous electrodeposition methods. The morphology, crystalline components present and thermal behavior of bare TNTs and Ni-doped TNTs were characterized by XRD, SEM, EDS and TGA. The photoelectrocatalytic performance of Ni-TNTs specimens was evaluated for the hydrogen evolution reaction under UV–Visible conditions.

11:40 AM  
Phase Relation Prediction for AgxCu1-xGayIn1-ySe2 PV Absorber Layers: Zhi Li1; Christopher Muzzillo1; Shun-li Shang2; Jianyun Shen3; Po-Hsin Liao1; Zi-kui Liu2; Timothy Anderson1; 1University of Florida; 2Pennsylvania State University; 3General Research Institute For Nonferrous Metals
    The chalcopyrite alloy Cu(In,Ga)Se2 (CIGS) has achieved tremendous success as an absorber for thin film PV devices. The absorber composition of the current champion cell, however, is not at the optimal bandgap energy. Alloying CIGS with Ag to form AgxCu1-xGayIn1-ySe2 (ACGIS) can not only increases the bandgap, but also promises to reduce the processing temperature, improves the crystalline quality, and provides more opportunities for liquid phase assisted growth to attain greater power conversion efficiency. Thus understanding the phase chemistry of the Ag-Cu-Ga-In-Se system is of interest to improve the absorber synthesis process. In this work, an assessment of the thermochemistry and phase equilibria of the Ag-Cu-Ga-In-Se system was performed based on available experimental data and predictions of temperature dependence of the Gibbs energies of formation for the intermetallic compounds. With the complete thermodynamic database, the implications for selenization of metal precursors are explored.