<i>Ab initio</i> atomistic thermodynamics study on the oxidation mechanism of binary and ternary alloy surfaces

Liu, Shiyu; Liu, Shiyang; Li, Dejun; Wang, Sanwu; Guo, Jing; Shen, Y.G.

doi:10.1063/1.4907718

Cited by 18 publications

(6 citation statements)

References 48 publications

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“…Not all these elements are simultaneously or necessarily present in every alloy. However, Si and Ti are always present in the alloys, both tend to segregate to Nb ss grains in the surface and the segregation of Ti is more severe [ 58 , 59 ]. The latter was suggested to promote the selective oxidation of Ti and the early formation of TiO 2 in the scale [ 58 ].…”

Section: Objectives Results and Discussionmentioning

confidence: 99%

On Nb Silicide Based Alloys: Alloy Design and Selection

Tsakiropoulos

2018

Materials

279

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The development of Nb-silicide based alloys is frustrated by the lack of composition-process-microstructure-property data for the new alloys, and by the shortage of and/or disagreement between thermodynamic data for key binary and ternary systems that are essential for designing (selecting) alloys to meet property goals. Recent publications have discussed the importance of the parameters δ (related to atomic size), Δχ (related to electronegativity) and valence electron concentration (VEC) (number of valence electrons per atom filled into the valence band) for the alloying behavior of Nb-silicide based alloys (J Alloys Compd 748 (2018) 569), their solid solutions (J Alloys Compd 708 (2017) 961), the tetragonal Nb5Si3 (Materials 11 (2018) 69), and hexagonal C14-NbCr2 and cubic A15-Nb3X phases (Materials 11 (2018) 395) and eutectics with Nbss and Nb5Si3 (Materials 11 (2018) 592). The parameter values were calculated using actual compositions for alloys, their phases and eutectics. This paper is about the relationships that exist between the alloy parameters δ, Δχ and VEC, and creep rate and isothermal oxidation (weight gain) and the concentrations of solute elements in the alloys. Different approaches to alloy design (selection) that use property goals and these relationships for Nb-silicide based alloys are discussed and examples of selected alloy compositions and their predicted properties are given. The alloy design methodology, which has been called NICE (Niobium Intermetallic Composite Elaboration), enables one to design (select) new alloys and to predict their creep and oxidation properties and the macrosegregation of Si in cast alloys.

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Section: Objectives Results and Discussionmentioning

confidence: 99%

On Nb Silicide Based Alloys: Alloy Design and Selection

Tsakiropoulos

2018

Materials

279

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“…Ab initio calculations were based on density functional theory, the projector augmented wave (PAW) method, and plane-wave basis sets [28][29][30][31][32][33][34][35][36][37]. All the calculations were performed with the use of Vienna ab initio simulation package (the VASP code) [28][29][30].…”

Section: Ab Initio Calculationsmentioning

confidence: 99%

Hydrogenation of o-cresol on platinum catalyst: Catalytic experiments and first-principles calculations

Liu

Xue

et al. 2017

Applied Surface Science

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Catalytic experiments were performed for the hydrogenation of o-cresol in n-dodecane over a platinum catalyst. Batch reactions analyzed with an in-situ ATR IR probe suggest that the hydrogenation results in the formation of the final product, 2-methyl-cyclohexanol, with 2-methyl-cyclohexanone as the intermediate product. Ab initio density-functional theory was employed to investigate the atomic-scale mechanism of o-cresol hydrogenation on the Pt(111) surface. The formation of 2-methyl-cyclohexanone was found to involve two steps. The first step is a hydrogen abstraction, that is, the H atom in the hydroxyl group migrates to the Pt surface. The second step is hydrogenation, that is, the pre-existing H atoms on Pt react with the carbon atoms in the aromatic ring. On the other hand, 2-methyl-cyclohexanonol may be produced through two paths, with activation energies slightly greater than that for the formation of 2methyl-cyclohexanone. One path involves direct hydrogenation of the aromatic ring. Another path involves three steps, with the partial hydrogenation of the ring as the first step, hydrogen abstraction of the-OH group as the second, and hydrogenation of remaining C atoms and the O atom the last.

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“…For all the optimization calculations, the Pt atoms of the bottom two layers were fixed while the Pt atoms of the top three layers and all the atoms of the molecule were allowed to move until the forces on all the atoms that were allowed to relax were less than 0.05 eV/Å. Reaction pathways and the associated barriers were determined with DFT using the climbing image nudged elastic band method. , A plane-wave energy cutoff of 400 eV and two special k points in the irreducible part of the two-dimensional Brillouin zone of the 5 × 5 surface cell were used for all the calculations. − …”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

Hydrogenation of o-Cresol at the Water/Pt(111) Interface

Li¹,

Liu

Liu³

et al. 2019

J. Phys. Chem. C

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Catalytic experiments were performed to investigate the hydrogenation of o-cresol to 2-methylcyclohexanol on a platinum catalyst in water. It has been observed experimentally both here and in prior studies that intermediate ketones desorb from the catalyst surface in the vapor phase or in hydrocarbon solvents, but they are not observed when reactions are carried out in the aqueous phase. Density functional theory was employed to explore the atomic-scale mechanism of o-cresol hydrogenation at the water/Pt(111) interface. Here, we show that water plays a dual role of accelerating the rate of hydrogenation of these ketones by shuttling hydrogen from the surface while also decreasing the rate of desorption of the less polar ketone intermediate from the catalyst surface. These two effects, when combined, explain the lack of observation of these ketone intermediates when this hydrogenation reaction is carried out in the aqueous phase.

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Ab initio atomistic thermodynamics study on the oxidation mechanism of binary and ternary alloy surfaces

Cited by 18 publications

References 48 publications

On Nb Silicide Based Alloys: Alloy Design and Selection

On Nb Silicide Based Alloys: Alloy Design and Selection

Hydrogenation of o-cresol on platinum catalyst: Catalytic experiments and first-principles calculations

Hydrogenation of o-Cresol at the Water/Pt(111) Interface

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