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Yang, Ying

Publications and source records attributed to Yang, Ying.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Design and screening of nanoprecipitates-strengthened advanced ferritic alloys

Advanced nuclear reactors as well as the life extension of light water reactors require advanced alloys capable of satisfactory operation up to neutron damage levels approaching 200 displacements per atom (dpa). Extensive studies, including fundamental theories, have demonstrated the superior resistance to radiation-induced swelling in ferritic steels, primarily inherited from their body-centered cubic (bcc) structure. This study aims at developing nanoprecipitates strengthened advanced ferritic alloys for advanced nuclear reactor applications. To be more specific, this study aims at enhancing the amorphization ability of some precipitates, such as Laves phase and other types of intermetallic phases, through smart alloying strategy, and thereby promote the crystalline®amorphous transformation of these precipitates under irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Development of Computational Tools for Predicting Thermal- and Radiation-Induced Solute Segregation at Grain Boundaries in Fe-based Alloys

Radiation-induced segregation (RIS) has been frequently reported in structural materials such as austenitic, ferritic, and ferritic-martensitic stainless steels (SS) that have been widely used in light water reactors (LWRs). RIS has been linked to secondary degradation effects in SS including irradiation-induced stress corrosion cracking (IASCC). Earlier studies on thermal segregation in Fe-based alloys found that metalloids elements such as P, S, Si, Ge, Sn, etc., embrittle the materials when enrichment was observed at grain boundaries (GBs). RIS of Fe-Cr-Ni-based austenitic steels has been modeled in the U.S. 2015 fiscal year (FY2015), which identified the pre-enrichment due to thermal segregation can have an important role on the subsequent RIS. The goal of this work is to develop thermal segregation models for alloying elements in steels for future integration with RIS modeling.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2016

Fabrication of ultrafine manganese oxide-decorated carbon nanofibers for high-performance electrochemical capacitors

Ultrafine manganese oxide-decorated carbon nanofibers (MnOn-CNF) as a new type of electrode materials are facilely fabricated by direct conversion of Mn, Zn-trimesic acid (H3BTC) metal organic framework fibers (Mn-ZnBTC). The construction and evolution of Mn-ZnBTC precursors are investigated by SEM and in situ high-energy XRD. The manganese oxides are highly dispersed onto the porous carbon nanofibers formed simultaneously, verified by TEM, X-ray absorption fine structure (XAFS), Raman, ICP-AES and N2 adsorption techniques. As expected, the resulting MnOn-CNF composites are highly stable, and can be cycled up to 5000 times with a high capacitance retention ratio of 98% in electrochemical capacitor measurements. They show a high capacitance of up to 179 F g–1 per mass of the composite electrode, and a remarkable capacitance of up to 18290 F g–1 per active mass of the manganese(IV) oxide, significantly exceeding the theoretical specific capacitance of manganese(IV) oxide (1370 F g–1). The maximum energy density is up to 19.7 Wh kg–1 at the current density of 0.25 A g–1, even orders higher than those of reported electric double-layer capacitors and pseudocapacitors. The excellent capacitive performance can be ascribed to the joint effect of easy accessibility, high porosity, tight contact and superior conductivity integrated in final MnOn-CNF composites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Computational thermodynamics aided design of novel ferritic alloys

With the aid of computational thermodynamics, Ni was identified to suppress the liquidus temperature of Fe 2 Zr and four Fe-Cr-Ni-Zr alloys were designed to study the Ni effect on the phase stability of Fe 2 Zr laves_phase. These alloys were fabricated through traditional arc-metling, followed by annealing at 1000 C for 336 hours and 700 C for 1275 hours. The microstructure were examined and characterized by SEM BSE image, EDS compositional mapping and point scan, XRD and TEM analysis. The major results were summarized below: 1)For investigated alloys with 12wt% Cr, 3~6wt% Zr and 3~9 wt%Ni, the phases in equilibrium with the BCC phase are C15_Laves phase, Fe 23 Zr 6 phase. The volume fraction of intermetallic phases increases with Ni and Zr contents. 2)Instead of (Fe,Cr) 2 Zr C14_Laves phase, Ni stabilizes the C15_Laves structure in Fe-Cr-Ni-Zr alloys by substituting Fe and Cr atoms with Ni atoms in the first sublattice. 3)Fe 23 Zr 6 , that is metastable in the Fe-Cr-Zr ternary, is also stabilized by Ni addition. 4)Ni 7 Zr 2 phase was observed in samples with high Ni/Zr ratio. Extensive solubility of Fe was identified in the phase. The microstructural and composition results obtained from this study will be incorportated into the the Fe-Cr-Ni-Zr database. The current samples will be subjected to ion irradiaition to be compared with those results for Fe-Cr-Zr alloys. Additional alloys will be designed to form (Fe,Cr,Ni) 2 Zr nanoprecipitates for further studies.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Thermal Aging Degradation of Cast Stainless Steels in LWR Systems

Cast austenitic stainless steels (CASSs) have been extensively used for the large components of light water reactor (LWR) power plants such as primary coolant piping and pump casing. Since a large number of massive CASS components are installed in every modern nuclear power plant, any significant degradation of CASS components will raise serious concerns on the integrity of the entire power plant. Upon the presumption that the replacement cost of such massive components is prohibitive, therefore, thorough scientific understanding and systematic monitoring the thermal aging degradation of CASS components should be essential requirements for assessing the plant safety. In the past few decades many researches have concluded that the formation of Cr-rich α-phase by Spinoidal decomposition of δ-ferrite phase, which is formed in high temperature region during cooling, is the primary mechanism for the thermal embrittlement. Cracking mechanism in the thermally-embrittled duplex stainless steels consists of cleavage initiation at ferrite and crack propagation via separation of ferrite-austenite interphase. It has been known, however, that such thermal aging embrittlement is observed only in accelerated aging conditions and the cast stainless steel grades used in nuclear plants have performed well without experiencing real embrittlement. It has been speculated that long-term thermal aging for ≥ 60 years could lead to further decomposition of designed phases and increase of precipitation. This will result in significantly increased susceptibility to embrittlement or other degradation due to thermal aging-radiation synergistic effect, irradiation-induced degradation, stress-corrosion cracking, and general corrosion. Currently, therefore, the thermal embrittlement of CASS components is one of the most serious concerns for extended operation of nuclear power plants. A scientific research is underway to address the issues related to the thermal aging degradation of CASS components. The research aims to provide knowledge-based conclusive prediction for the integrity of the CASS components of LWR power plants during extended operation up to and beyond 60 years. This presentation intends to provide an introductory overview on the thermal aging phenomena in LWR relevant conditions and discussion on the measurements of mechanical property degradation after accelerated and LWR relevant thermal aging treatments. First, the thermal aging effect on toughness is discussed in terms of the causes of embrittlement and influential parameters. Second, the talk will include a comprehensive discussion on the thermal aging effects in different CASS grades (i.e., CF3, CF3M, CF8, and CF8M), which will focus on the influence of alloying elements such as molybdenum and carbon. Third, approximate analysis on thermal reaction in CASS was carried out using Arrhenius equation to decide the effective temperature range for accelerated aging experiments to simulate 60 and 80 years of services in limited time frame. The results will provide valuable insights in the degree of thermal aging. Fourth, calculation on equilibrium precipitation was performed for model CASS alloys using the CALPHAD program, and the results will be used to describe the precipitation behaviors in association with the degradation in mechanical properties. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2016

Thermodynamic and Kinetic Modeling on Thermal Segregation of Phosphorus in Iron

Radiation induced segregation (RIS) has been frequently reported in structural materials such as austenitic, ferritic, and ferritic-martensitic stainless steels (SS) that have been widely used in light water reactors (LWRs). RIS has been linked to secondary degradation effects in SS including irradiation induced stress corrosion cracking (IASCC). Earlier studies on thermal segregation in Fe based alloys found that metalloids elements such as P, S, Si, Ge, Sn etc. embrittle the materials when enrichment was observed at grain boundaries. RIS of Fe-Cr-Ni based austenitic steels has been modeled in the U.S. 2015 fiscal year (FY2015), which identified the pre-enrichment due to thermal segregation can have an important role on the subsequent RIS. The goal of this work is to develop thermal segregation models for alloying elements in steels for future integration with RIS modeling.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Enhanced photoelectrochemical and photocatalytic activity in visible-light-driven Ag/BiVO{sub 4} inverse opals

BiVO{sub 4} photonic crystal inverse opals (io-BiVO{sub 4}) with highly dispersed Ag nanoparticles (NPs) were prepared by the nanosphere lithography method combining the pulsed current deposition method. The incorporation of the Ag NPs can significantly improve the photoelectrochemical and photocatalytic activity of BiVO{sub 4} inverse opals in the visible light region. The photocurrent density of the Ag/io-BiVO{sub 4} sample is 4.7 times higher than that of the disordered sample without the Ag NPs, while the enhancement factor of the corresponding kinetic constant in photocatalytic experiment is approximately 3. The improved photoelectrochemical and photocatalytic activity is benefited from two reasons: one is the enhanced light harvesting owing to the coupling between the slow light and localized surface plasmon resonance effect; the other is the efficient separation of charge carriers due to the Schottky barriers.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Roles of Vacancy/Interstitial Diffusion and Segregation in the Microchemistry at Grain Boundaries of Irradiated Fe-Cr-Ni alloys

A detailed analysis of the diffusion fluxes near and at grain boundaries of irradiated Fe–Cr–Ni alloys, induced by preferential atom-vacancy and atom-interstitial coupling, is presented. The diffusion flux equations were based on the Perks model formulated through the linear theory of the thermodynamics of irreversible processes. The preferential atom-vacancy coupling was described by the mobility model, whereas the preferential atom-interstitial coupling was described by the interstitial binding model. The composition dependence of the thermodynamic factor was modeled using the CALPHAD approach. The calculated fluxes up to 10 dpa suggested the dominant diffusion mechanism for chromium and iron is via vacancy, while that for nickel can swing from the vacancy to the interstitial dominant mechanism. The diffusion flux in the vicinity of a grain boundary was found to be greatly modified by the segregation induced by irradiation, leading to the oscillatory behavior of alloy compositions in this region.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Facile Fabrication of Composition-Tuned Ru-Ni Bimetallics in Ordered Mesoporous Carbon for Levulinic Acid Hydrogenation

Bimetallic catalysts are of great importance due to their unique catalytic properties. However, their conventional synthesis requires tedious multistep procedures and prolonged synthetic time, and the resulting bimetallics usually disperse unevenly and show poor stability. It is challenging to develop a facile and step-economic synthetic methodology for highly efficient bimetallic catalysts. In this study, we report an elegant metal complex-involved multicomponent assembly route to highly efficient Ru–Ni bimetallics in ordered mesoporous carbons (OMC). The fabrication of composition-tuned Ru–Ni bimetallics in OMC (Ru x Ni 1–x –OMC, x = 0.5–0.9) was facilely realized via in situ construction of CTAB-directed cubic Ia3d chitosan-ruthenium–nickel–silica mesophase before pyrolysis and silica removal. The resulting Ru x Ni 1–x –OMC materials are in-depth characterized with X-ray diffraction, N 2 adsorption–desorption, transmission electron microscopy, infrared spectrum, and X-ray absorption fine structure. This facile fabrication method renders homogeneously dispersed Ru–Ni bimetallics embedded in the mesoporous carbonaceous framework and creates a highly active and stable Ru 0.9 Ni 0.1 –OMC catalyst for the hydrogenation of levulinic acid (LA) to prepare γ-valerolactone (GVL), a biomass-derived platform molecule with wide application in the preparation of renewable chemicals and liquid transportation fuels. A high TOF (>2000 h –1 ) was obtained, and the Ru 0.9 Ni 0.1 –OMC catalyst could be used at least 15 times without obvious loss of its catalytic performance.

Yang, Ying↗
DOE OSTI2016

Facile fabrication of MnO x and N co-doped hierarchically porous carbon microspheres for high-performance supercapacitors

Facile fabrication of manganese oxide (MnO x , 0 < x < 2) and nitrogen (N) co-doped carbon microspheres (MnO x -N-CS) has been firstly developed by one-pot construction of Mn-functionalized melamine-formaldehyde (Mn-MF) resin spheres before pyrolysis. The resulting hybrids bear evenly dispersed MnO x and N moieties in situ anchored on hierarchically porous carbon microspheres formed simultaneously. The capacitive performance is greatly tailored by varying the Mn/melamine molar ratio in the synthetic mixture and pyrolysis temperature. It is found that the MnO x -N-CS hybrid (0.008 wt% Mn, pyrolyzed at 800 °C) exhibits the highest specific capacitance up to 258 F g –1 at a scan rate of 1 mV s –1 (in 6 M KOH), and keeps a high capacitance retention ratio of 98% after 5000 cycles. The synergism between MnO x , N moieties and carbon spheres proves to be responsible for the remarkably improved performance, as compared to the pure carbon sphere and MnO x (N)-doped carbon sphere. Lastly, the well-developed MnO x -N-CS hybrids highlight the great potentials for widespread supercapacitor applications.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A smart strategy to fabricate Ru nanoparticle inserted porous carbon nanofibers as highly efficient levulinic acid hydrogenation catalysts

Herein, we first put forward a smart strategy to in situ fabricate Ru nanoparticle (NP) inserted porous carbon nanofibers by one-pot conversion of Ru-functionalized metal organic framework fibers. Such fiber precursors are skillfully constructed by cooperative assembly of different proportional RuCl3 and Zn(Ac)2·2H2O along with trimesic acid (H3BTC) in the presence of N,N-dimethylformamide. The following high-temperature pyrolysis affords uniform and evenly dispersed Ru NPs (ca. 12-16 nm), which are firmly inserted into the hierarchically porous carbon nanofibers formed simultaneously. The resulting Ru-carbon nanofiber (Ru-CNF) catalysts prove to be active towards the liquid-phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL), a biomass-derived platform molecule with wide applications in the preparation of renewable chemicals and liquid transportation fuels. The optimal GVL yield of 96.0% is obtained, corresponding to a high activity of 9.23 molLAh–1gRu–1, 17 times of that using the commercial Ru/C catalyst. Moreover, the Ru-CNF catalyst is extremely stable, and can be cycled up to 7 times without significant loss of reactivity. Our strategy demonstrated here reveals new possibilities to make proficient metal catalysts, and provides a general way to fabricate metal-carbon nanofiber composites available for other applications.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Versatile nickel–tungsten bimetallics/carbon nanofiber catalysts for direct conversion of cellulose to ethylene glycol

We herein propose a novel synthetic methodology for a series of nickel–tungsten bimetallics/carbon nanofiber catalysts (Ni, 0.37–2.08 wt%; W, 0.01–0.06 wt%) in situ fabricated by pyrolysis (950 °C) of Ni, W and Zn-containing metal organic framework (Ni0.6-x–Wx–ZnBTC, x = 0–0.6) fibers. The resulting catalysts (Ni0.6-x–Wx/CNF) have uniform particles (ca. 68 nm), evenly dispersed onto the hierarchically porous carbon nanofibers formed simultaneously. All of the Ni0.6-x–Wx/CNF catalysts prove to be highly active towards direct conversion of cellulose to ethylene glycol (EG). A large productivity ranging from 15.3 to 70.8 molEG h-1 gW-1 is shown, two orders of magnitude higher than those by using other W-based catalysts reported.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Microstructural evolution of type 304 and 316 stainless steels under neutron irradiation at LWR relevant conditions

Extension of light water reactors' useful life will expose austenitic internal core components to irradiation damage levels beyond 100 displacements per atom (dpa), which will lead to profound microstructural evolution and consequent degradation of macroscopic properties. Microstructural evolution, including Frank loops, cavities, precipitates, and segregation at boundaries and the resultant radiation hardening in type 304 and 316 stainless steel (SS) variants, were studied in this work via experimental characterization and multiple simulation methods. Experimental data for up to 40 heats of type 304SS and 316SS variants irradiated in different reactors to 0.6–120 dpa at 275–375°C were either generated from this work or collected from literature reports. These experimental data were then combined with models of Frank loop and cavity evolution, computational thermodynamics and precipitation, and ab initio and rate theory integrated radiation-induced segregation models to provide insights into microstructural evolution and degradation at higher radiation doses.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Accelerated development of Zr-containing new generation ferritic steels for advanced nuclear reactors

The mission of the Nuclear Energy Enabling Technologies (NEET) program is to develop crosscutting technologies for nuclear energy applications. Advanced structural materials with superior performance at elevated temperatures are always desired for nuclear reactors, which can improve reactor economics, safety margins, and design flexibility. They benefit not only new reactors, including advanced light water reactors (LWRs) and fast reactors such as the sodium-cooled fast reactor (SFR) that is primarily designed for management of high-level wastes, but also life extension of the existing fleet when component exchange is needed. Developing and utilizing the modern materials science tools (experimental, theoretical, and computational tools) is an important path to more efficient alloy development and process optimization. The ultimate goal of this project is, with the aid of computational modeling tools, to accelerate the development of Zr-bearing ferritic alloys that can be fabricated using conventional steelmaking methods. The new alloys are expected to have superior high-temperature creep performance and excellent radiation resistance as compared to Grade 91. The designed alloys were fabricated using arc-melting and drop-casting, followed by hot rolling and conventional heat treatments. Comprehensive experimental studies have been conducted on the developed alloys to evaluate their hardness, tensile properties, creep resistance, Charpy impact toughness, and aging resistance, as well as resistance to proton and heavy ion (Fe 2+ ) irradiation.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

Development and property evaluation of nuclear grade wrought FeCrAl fuel cladding for light water reactors

Development of nuclear grade, iron-based wrought FeCrAl alloys has been initiated for light water reactor (LWR) fuel cladding to serve as a substitute for zirconium-based alloys with enhanced accident tolerance. Ferritic alloys with sufficient chromium and aluminum additions can exhibit significantly improved oxidation kinetics in high-temperature steam environments when compared to zirconium-based alloys. In the first phase, a set of model FeCrAl alloys containing 10–20Cr, 3–5Al, and 0–0.12Y in weight percent, were prepared by conventional arc-melting and hot-working processes to explore the effect of composition on the properties of FeCrAlY alloys. It was found that the tensile properties were insensitive to the alloy compositions studied; however, the steam oxidation resistance strongly depended on both the chromium and the aluminum contents. The second phase development focused on strengthening Fe-13Cr-5Al with minor alloying additions of molybdenum, niobium, and silicon. Combined with an optimized thermo-mechanical treatment, a thermally stable microstructure was produced with improved tensile properties at temperatures up to 741°C.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗