PALS study of point defects in Fe‐Al and Fe‐Al‐Cr alloys

Kansy, J.; Hanc, A.; Pająk, L.; Giebel, Dawid

doi:10.1002/pssc.200982107

Cited by 6 publications

(4 citation statements)

References 9 publications

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“…Positron lifetime spectra were deconvoluted and analyzed using the LT-9 program. 37 Electrode Preparation and Electrochemical Characterization. Electrochemical measurements were performed with a standard three-electrode setup (CH Instruments) using Ag/AgCl (in 3.5 M KCl solution) as the reference electrode, a graphite rod (Alfa Aesar, 99.9995%) as the counter electrode, and glassy carbon electrode (3 mm in diameter) coated with MoS 2 catalysts as the working electrode in a rotating disk electrode (RDE) operating at 2000 rpm.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

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Contributions of Phase, Sulfur Vacancies, and Edges to the Hydrogen Evolution Reaction Catalytic Activity of Porous Molybdenum Disulfide Nanosheets

Yin¹,

Han²,

Zhang³

et al. 2016

J. Am. Chem. Soc.

1,124

804

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Molybdenum disulfide (MoS2) is a promising nonprecious catalyst for the hydrogen evolution reaction (HER) that has been extensively studied due to its excellent performance, but the lack of understanding of the factors that impact its catalytic activity hinders further design and enhancement of MoS2-based electrocatalysts. Here, by using novel porous (holey) metallic 1T phase MoS2 nanosheets synthesized by a liquid-ammonia-assisted lithiation route, we systematically investigated the contributions of crystal structure (phase), edges, and sulfur vacancies (S-vacancies) to the catalytic activity toward HER from five representative MoS2 nanosheet samples, including 2H and 1T phase, porous 2H and 1T phase, and sulfur-compensated porous 2H phase. Superior HER catalytic activity was achieved in the porous 1T phase MoS2 nanosheets that have even more edges and S-vacancies than conventional 1T phase MoS2. A comparative study revealed that the phase serves as the key role in determining the HER performance, as 1T phase MoS2 always outperforms the corresponding 2H phase MoS2 samples, and that both edges and S-vacancies also contribute significantly to the catalytic activity in porous MoS2 samples. Then, using combined defect characterization techniques of electron spin resonance spectroscopy and positron annihilation lifetime spectroscopy to quantify the S-vacancies, the contributions of each factor were individually elucidated. This study presents new insights and opens up new avenues for designing electrocatalysts based on MoS2 or other layered materials with enhanced HER performance.

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Section: ■ Materials and Methodsmentioning

confidence: 99%

“…More than two million counts were accumulated for each spectrum to reduce the statistical error in the calculation of lifetimes. Positron lifetime spectra were deconvoluted and analyzed using the LT-9 program …”

Section: Methodsmentioning

confidence: 99%

Contributions of Phase, Sulfur Vacancies, and Edges to the Hydrogen Evolution Reaction Catalytic Activity of Porous Molybdenum Disulfide Nanosheets

Yin¹,

Han²,

Zhang³

et al. 2016

J. Am. Chem. Soc.

1,124

804

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“…In this work, positron lifetime spectroscopy (PALS) is employed to study quench-in vacancies in Fe28Al after various thermal treatments. Positron techniques have been often used for studies of defect behavior in Fe-Al system [2,[6][7][8][9][10][11][12]. Also an attempt to define the ordering degree based on the determined positron lifetime values in point defects will be carried out.…”

Section: Introductionmentioning

confidence: 99%

Point Defect Study in Fe<sub>72</sub>Al<sub>28</sub> Alloy as a Function of Thermal Treatment by Positron Lifetime Spectroscopy

Kansy

Hanc

Jabłońska

et al. 2010

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The defect structure of Fe28Al samples is examined with the Positron Annihilation Lifetime Spectroscopy. The studies are carried out for samples in as-cast state and after heat treatments: annealing for 24 hours at 900°C (or 1050°C) and either slow cooling with furnace or quenching to oil. The PALS spectra are analyzed using two-state trapping model. Only one type of defects is detected. The positron lifetime in these defects (V) suggests that they are quenched-in Fe-monovacancies (VFe). The vacancy concentration strongly depends on the rate of cooling. Besides, V also depends slightly on the rate of cooling of the material. This fact suggests, according to the predictions of latest theoretical calculations, that V is sensitive to the atomic configuration in the nearest neighborhood of VFe, which give hope to estimate the degree of atomic ordering in alloys by the PALS technique.

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“…Generally, as-measured lifetime spectra could be fitted into three exponential functions, representing three types of annihilation sites, respectively. Then, we de-convoluted and fit the lifetime spectra by using the program (LT-9) according to this rule [24]. After fitting, the ~ 2 ns long lifetime (τ 3 ) corresponding to annihilations at sample surface or voids is very small in its fraction and will be ignored in the following analysis.…”

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confidence: 99%

Vacancy defect complexes in silicon: Charges and spin order

et al. 2016

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We investigate the interaction between charges and spin order of the defect complex V6 in silicon. The first-principles calculations predict spin resolved band splitting incurred by a neutral V6 yet with no net spin. Therefore, any shift of Fermi level can trigger the spin polarization. Both s and p states contribute local moments in the positively charged V6. The ferromagnetic coupling is only obtained between a positively charged V6 and a neutral one. In silicon after neutron irradiation, magnetism is achieved even at room temperature. The 3s*3p* hybrid states of V6 are probably responsible for the observed long-range magnetic order. Our results unravel the role of charged V6 in inducing magnetism and will be useful in understanding and further manipulating the intrinsic properties of defect complexes in silicon and other semiconductors.

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PALS study of point defects in Fe‐Al and Fe‐Al‐Cr alloys

Cited by 6 publications

References 9 publications

Contributions of Phase, Sulfur Vacancies, and Edges to the Hydrogen Evolution Reaction Catalytic Activity of Porous Molybdenum Disulfide Nanosheets

Contributions of Phase, Sulfur Vacancies, and Edges to the Hydrogen Evolution Reaction Catalytic Activity of Porous Molybdenum Disulfide Nanosheets

Point Defect Study in Fe<sub>72</sub>Al<sub>28</sub> Alloy as a Function of Thermal Treatment by Positron Lifetime Spectroscopy

Vacancy defect complexes in silicon: Charges and spin order

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