In-situ probing of thermal desorption of vapor molecules on a nanowire via work function variance

Prashanthi, K.; Hawk, J. E.; McGee, Ryan; Gaikwad, Ravi; Thundat, Thomas

doi:10.1007/s12274-016-1210-y

Cited by 6 publications

(6 citation statements)

References 57 publications

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“…Future work will include surface adsorption into the calculation, since that process may play an important role in changing the measured work function of metal surface. 36,41,45,46 Implications on micro-galvanic corrosion and corrosion potential.-We discuss next what practical implications our calculated data can have on predicting corrosion performance, i.e., to what extent the calculated Volta potential data can be used to predict the corrosion potential of a metal in a given electrolyte. In the pioneering experimental studies performed using both standard scanning Kelvin probe 10 and SKPFM, 12 a linear relationship was found between the corrosion potential and Volta potential for a number of metals measured.…”

Section: Theoretical and Experimental Volta Potentials Of Impsmentioning

confidence: 99%

First-Principle Calculation of Volta Potential of Intermetallic Particles in Aluminum Alloys and Practical Implications

Jin

Liu

Zhang

et al. 2017

J. Electrochem. Soc.

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This work presents a theoretical assessment of galvanic (relative) nobility of four intermetallic particles (IMPs), Al 2 Cu, Al 2 CuMg, Mg 2 Si and MgZn 2 , in aluminum alloys through work function calculation based on density functional theory (DFT). The concepts of work function, Volta potential and relative nobility are discussed with respect to the IMPs and aluminum matrix. The calculated Volta potentials are compared with reported experimental Volta potentials measured by scanning Kelvin probe force microscopy (SKPFM). Various crystal faces and terminal types are examined in the DFT calculation, showing that these two factors have a significant effect on the work function value. Considering the large divergence in the reported experimental data, the comparison shows a general agreement between the calculated and experimental Volta potential data for the investigated IMPs. The DFT calculations provide theoretical explanations for several experimental phenomena. The results demonstrate that DFT calculation is a valuable theoretical approach for assessment of the relative nobility of different phases in the alloys, providing complementary information to experimental data from SKFPM. Moreover, the implications of the calculated Volta potentials are discussed with respect to the corrosion potentials. The addition of various alloying elements into the aluminum (Al) matrix to improve mechanical performance of Al alloys may simultaneously increase their susceptibility to localized corrosion. This is mainly due formation of intermetallic particles (IMPs) that may trigger micro-galvanic corrosion along the interface between the IMPs and the alloy matrix.1 The potential differences between the IMPs and the matrix may result in localized dissolution of the matrix or dealloying of the IMP. 2The most common IMPs present in 2xxx and 7xxx series Al alloys include Al 2 CuMg (S-phase), Al 2 Cu (θ-phase), Al 7 Cu 2 Fe (β-phase), MgZn 2 (η-phase) and Mg 2 Si.3-5 IMPs containing Cu and Fe, such as Al 2 Cu. 6 and Al 7 Cu 2 Fe, 7 are considered to be cathodic with respect to the matrix, acting as local cathodes and thus promoting cathodic reactions such as oxygen reduction. In contrast, Mg-rich IMPs, such as Al 2 CuMg, are considered anodic relative to the matrix, resulting in selective dissolution and concomitant Cu-enrichment of the IMP.8 These localized corrosion events may eventually trigger other corrosion forms, such as stress corrosion cracking or intergranular corrosion.9 Therefore, micro-galvanic corrosion effects between IMPs and the Al matrix is considered to be of utmost importance for the overall service performance of Al alloys.In 1987, Stratmann started to use the Kelvin probe to investigate corrosion properties of metals under thin electrolyte films.10 His measurements revealed a linear relationship between Volta potential and corrosion potential of Cu, Zn, Fe and other metals. Later, the scanning Kelvin microprobe was developed and used for Volta potential measurements of several metals in humid atmospheres.11 Du...

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Section: Theoretical and Experimental Volta Potentials Of Impsmentioning

confidence: 99%

First-Principle Calculation of Volta Potential of Intermetallic Particles in Aluminum Alloys and Practical Implications

Jin

Liu

Zhang

et al. 2017

J. Electrochem. Soc.

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“…Work function modifications resulting from surface adsorption can be investigated using electronic structure methods 27,28 to solve the Helmholtz equation,…”

Section: Surface Dipolementioning

confidence: 99%

Metal Hexaboride Work Functions: Surface Configurations and the Electrical Double Layer from First‐Principles

Schmidt

Misture

Graeve

et al. 2018

Adv Elect Materials

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“…40 Additionally, measurements of the work function are proving to be a useful tool to investigate real-time adsorbate surface coverage for some materials. 41 The work functions are calculated for each of the clean and adsorbate-covered surfaces, and these are given in Table 5. Note that work functions for the 1 × 1 slabs are calculated for boron-terminated surfaces and presented to identify general trends.…”

Section: Resultsmentioning

confidence: 99%

“…In fact, the dipole created by metal-terminated MB 6 materials is one of the main reasons LaB 6 has such a low work function . Additionally, measurements of the work function are proving to be a useful tool to investigate real-time adsorbate surface coverage for some materials . The work functions are calculated for each of the clean and adsorbate-covered surfaces, and these are given in Table .…”

Section: Resultsmentioning

confidence: 99%

Interaction of Hydrogen with MB₆ (M = Ba, Ca, La, and Sr) Surfaces from First Principles

et al. 2019

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We show results of basic energetics and interacting behavior of hydrogen with metal hexaboride surfaces using a combination of self-consistent density functional calculations and dynamics based on the Car–Parrinello method. Our results show that hydrogen is strongly attracted to localized exposed boron atoms and interactions with the terminal cations are strictly repulsive. From these, preliminary local adsorption energy calculations suggest that a single hydrogen molecule per surface unit-cell is possible (one ML). Strongest bonds are found when hydrogen is above the terminal boron atoms affected by reduced coordination and dangling bonds. This location serves to restore the hexaboride unit to a more stable structure by providing electronic density to the deficient surface octahedra. Additionally, trajectories from dynamic simulations provide insight into how hydrogen recombination reactions occur on the surface through dissociative adsorption and the method of travel prior to recombination to be along the octahedral face and bridging sites connecting separate unit cells on the surface. Upon adsorption, a single hydrogen atom becomes localized at the dangling bond site while the second interacts with the surface along a weaker potential energy path. Desorption at lower temperatures occurs when migrating atoms from separate adsorption sites intersect to form a new pair.

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In-situ probing of thermal desorption of vapor molecules on a nanowire via work function variance

Cited by 6 publications

References 57 publications

First-Principle Calculation of Volta Potential of Intermetallic Particles in Aluminum Alloys and Practical Implications

First-Principle Calculation of Volta Potential of Intermetallic Particles in Aluminum Alloys and Practical Implications

Metal Hexaboride Work Functions: Surface Configurations and the Electrical Double Layer from First‐Principles

Interaction of Hydrogen with MB₆ (M = Ba, Ca, La, and Sr) Surfaces from First Principles

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In-situ probing of thermal desorption of vapor molecules on a nanowire via work function variance

Cited by 6 publications

References 57 publications

First-Principle Calculation of Volta Potential of Intermetallic Particles in Aluminum Alloys and Practical Implications

First-Principle Calculation of Volta Potential of Intermetallic Particles in Aluminum Alloys and Practical Implications

Metal Hexaboride Work Functions: Surface Configurations and the Electrical Double Layer from First‐Principles

Interaction of Hydrogen with MB6 (M = Ba, Ca, La, and Sr) Surfaces from First Principles

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Interaction of Hydrogen with MB₆ (M = Ba, Ca, La, and Sr) Surfaces from First Principles