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147 results on '"Su, Yi Feng"'

8. Beneficial influence of Hf and Zr additions to Nb4at.%Ta on the vortex pinning of Nb$_{3}$Sn with and without an O source

Author

Balachandran, Shreyas, Tarantini, Chiara, Lee, Peter J., Kametani, Fumitake, Su, Yi-Feng, Walker, Benjamin, Starch, William L., and Larbalestier, David C.

Subjects
Condensed Matter - Superconductivity
Abstract

Here we show that addition of Hf to Nb4Ta can significantly improve the high field performance of Nb$_{3}$Sn, making it suitable for dipole magnets for Future Circular Collider (FCC). A big challenge for the FCC is that a realistic production target for FCC Nb3Sn requires ~30% improvement over current conductor performance. Recent success with internal oxidation(IO) of Nb-Zr precursor has shown significant improvement in the layer J$_{c}$ of Nb$_{3}$Sn wires, albeit the complication of providing an internal O$_{2}$ diffusion path and avoiding degradation of irreversibility field($_{irr}$). We compare Zr and Hf additions to the standard Nb4Ta alloy of maximum H$_{c2}$ and H$_{irr}$. Nb4Ta rods with 1Zr or 1Hf were made into monofilament wires with and without SnO$_{2}$ and their properties measured over the entire superconducting range up to 31 T. We found that group IV alloying of Nb4Ta raises H$_{irr}$, though adding O$_{2}$ still degrades this slightly. As noted in Nb1Zr studies, the pinning force density F$_{p}$ is strongly enhanced and its peak value shifted to higher field by IO. A surprising result of this work is that we found better properties in Nb4Ta1Hf without SnO$_{2}$, F$_{pmax}$ achieving 2.35 times that of the standard Nb4Ta alloy, while the oxidized Nb4Ta1Zr alloy achieved 1.54 times that of the Nb4Ta alloy. The highest layer J$_{c}$ (16 T, 4.2 K) of 3700 A/mm$^{2}$ was found in the SnO$_{2}$-free wire made with Nb4Ta1Hf alloy. Using a standard A15 cross-section fraction of 60% for modern PIT and RRP wires, we estimated that a non-Cu J$_{c}$ of 2200 A/mm$^{2}$ is obtainable in modern conductors, well above the 1500A/mm$^{2}$ FCC specification. Moreover, the best properties were obtained without SnO$_{2}$, the Nb4Ta1Hf alloy appears to open a straightforward route to enhanced properties in Nb$_{3}$Sn wires., Comment: 7 pages, 6 figures

Published
2018
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40. Formation of carbon and oxygen rich surface layer on high purity magnesium by atmospheric carbon dioxide plasma.

Author

Jang, Gyoung G., Yeom, Sinchul, Keum, Jong K., Yoon, Mina, Meyer, Harry III, Su, Yi-Feng, and Jun, Jiheon

Subjects
ATMOSPHERIC carbon dioxide, CARBON dioxide, WASTE minimization, WASTE treatment, MAGNESIUM
Abstract

Carbon and oxygen-rich corrosion barrier layer formed on Mg by a simple and scalable CO 2 atmospheric plasma (CO 2 -AP) process. The reactive CO 2 -AP interacts with the Mg surface and forms a unique layered structure with the top MgCO 3 /MgO-intermixed particulates pillars and the bottom dense layer. The surface features were simultaneously formed on the nano-/micro-structured MgO layer by carbonate molecules, plasma-active CO 2 molecules, and/or other volatile organic compounds on the nano-/micro-structured MgO particle layer. The resulting surfaces after CO 2 -AP were either hydrophobic or hydrophilic and exhibited lower anodic current or high resistance for Mg corrosion. For the hydrophobic surfaces of CO 2 -AP treated Mg, molecular dynamic simulations were performed to understand the origin of hydrophobicity and identified that the amorphous carbon layers formed on the Mg surface are the source. The environmentally benign abundant-gas-based process enables the cost reduction associated with waste treatment, generation of by-product, and supply of raw material. [ABSTRACT FROM AUTHOR]

Published
2023
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41. Steam oxidation and microstructural evolution of rare earth silicate environmental barrier coatings.

Author

Ridley, Mackenzie, Kane, Kenneth, Lance, Michael, Parker, Cory, Su, Yi‐Feng, Sampath, Sanjay, Garcia, Eugenio, Sweet, Marshall, O'Connor, Molly, and Pint, Bruce

Subjects
RARE earth oxides, OXIDATION kinetics, SURFACE coatings, YTTERBIUM, FAILURE mode & effects analysis, SILICATES
Abstract

A primary failure mode for environmental barrier coatings (EBCs) on SiC ceramic matrix composites (CMCs) is the oxidation of the intermediate Si‐bond coating, where the formation of SiO2 at the bond coating–EBC interface results in debonding and spallation. This work compares the microstructure evolution and steam oxidation kinetics of the Si‐bond coating beneath yttrium/ytterbium disilicate ((Y/Yb)DS) and ytterbium disilicate/monosilicate (YbDS/YbMS) EBCs to better understand the impact of EBC composition on oxidation kinetics. After 500 1‐h cycles at 1350°C, (Y/Yb)DS displayed a decreasing concentration of the monosilicate minor phase and increasing concentration of porosity as furnace cycling time increased, whereas the YbDS/YbMS EBC displayed negligible microstructural evolution. For both EBC systems, thermally grown oxide growth rates in steam were found to increase by approximately an order magnitude compared to dry air oxidation. The (Y/Yb)DS EBC displayed a reduced steam oxidation rate compared to YbDS/YbMS. [ABSTRACT FROM AUTHOR]

Published
2023
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42. Corrosion Compatibility of Stainless Steels and Nickel in Pyrolysis Biomass-Derived Oil at Elevated Storage Temperatures.

Author

Jun, Jiheon, Su, Yi-Feng, Keiser, James R., Wade IV, John E., Kass, Michael D., Ferrell III, Jack R., Christensen, Earl, Olarte, Mariefel V., and Sulejmanovic, Dino

Abstract

Corrosion compatibility of stainless steels and nickel (Ni200) was assessed in fast pyrolysis bio-oil produced from pyrolysis of high ash and high moisture forest residue biomass. Sample mass change, ICP-MS and post-exposure electron microscopy characterization was used to investigate the extent of corrosion. Among the tested samples, type 430F and type 316 stainless steels (SS430F and SS316) and Ni200 (~98.5% Ni) showed minimal mass changes (less than 2 mg∙cm−2) after the bio-oil exposures at 50 and 80 °C for up to 168 h. SS304 was also considered to be compatible in the bio-oil due to its relatively low mass change (1.6 mg∙cm−2 or lower). SS410 samples showed greater mass loss values even after exposures at a relatively low temperature of 35 °C. Fe/Cr values from ICP-MS data implied that Cr enrichment in stainless steels would result in a protective oxide layer associated with corrosion resistance against the bio-oil. Post exposure characterization showed continuous and uniform Cr distribution in the surface oxide layer of SS430F, which showed a minimal mass change, but no oxide layer on a SS430 sample, which exhibited a significant mass loss. [ABSTRACT FROM AUTHOR]

Published
2023
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49. Hollow metal halide perovskite nanocrystals with efficient blue emissions

Author

Worku, Michael, primary, Tian, Yu, additional, Zhou, Chenkun, additional, Lin, Haoran, additional, Chaaban, Maya, additional, Xu, Liang-jin, additional, He, Qingquan, additional, Beery, Drake, additional, Zhou, Yan, additional, Lin, Xinsong, additional, Su, Yi-feng, additional, Xin, Yan, additional, and Ma, Biwu, additional

Published
2020
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