Electron work function-a promising guiding parameter for material design

Theoretical Analysis of Stacking Fault Energy, Elastic Properties, Electronic Properties, and Work Function of MnxCoCrFeNi High-Entropy Alloy

The effects of different Mn concentrations on the generalized stacking fault energies (GSFE) and elastic properties of MnxCoCrFeNi high-entropy alloys (HEAs) have been studied via first-principles, which are based on density functional theory. The relationship of different Mn concentrations with the chemical bond and surface activity of MnxCoCrFeNi HEAs are discussed from the perspectives of electronic structure and work function. The results show that the plastic deformation of MnxCoCrFeNi HEAs can be controlled via dislocation-mediated slip. But with the increase in Mn concentration, mechanical micro twinning can still be formed. The deformation resistance, shear resistance, and stiffness of MnxCoCrFeNi HEAs increase with the enhancement of Mn content. Accordingly, in the case of increased Mn concentration, the weakening of atomic bonds in MnxCoCrFeNi HEAs leads to the increase in alloy instability, which improves the possibility of dislocation.

Exploring the local work function of metallic materials at the nanoscale: the influence of neighboring phases

This paper investigates the local work function distribution of a multi-phase metal material at the nanoscale and examines how it is influenced by its surrounding components. A formula is derived to express the relationship between the local work function and neighboring phases, taking into account the solid angle they form. The study's findings indicate a positive correlation between the local work function and the neighboring phases. Experimental results, DFT calculations, and previous theories are all used to verify the study's conclusions. Additionally, this paper offers predictions for the local work functions of a second phase surrounded by a matrix. These findings have practical implications for materials research at the nanoscale and offer a bridge between DFT calculations and nanoscale experimentation.

Electrochemical Generation of Mesopores and Residual Oxygen for the Enhanced Activity of Silver Electrocatalysts

The development of stable and efficient electrocatalysts is of key importance for the establishment of a sustainable society. The activity of a metal electrocatalyst is determined by its electrochemically active surface area and intrinsic activity, which can be increased using highly porous structures and heteroatomic doping, respectively. Herein, we propose a general strategy of generating mesopores and residual oxygen in metal electrocatalysts by reduction of metastable metal oxides using Ag2O3 electrodeposited onto carbon paper as a model system and demonstrating that the obtained multipurpose porous Ag electrocatalyst has high activity for the electroreduction of O2 and CO2. The presence of mesopores and residual oxygen is confirmed by electrochemical and spectroscopic techniques, and quantum mechanical simulations prove the importance of residual oxygen for electrocatalytic activity enhancement. Thus, the adopted strategy is concluded to allow the synthesis of highly active metal catalysts with controlled mesoporosity and residual oxygen content.

Electron work function: an indicative parameter towards a novel material design methodology

Electron work function (EWF) has demonstrated its great promise in materials analysis and design, particularly for single-phase materials, e.g., solute selection for optimal solid-solution strengthening. Such promise is attributed to the correlation of EWF with the atomic bonding and stability, which largely determines material properties. However, engineering materials generally consist of multiple phases. Whether or not the overall EWF of a complex multi-phase material can reflect its properties is unclear. Through investigation on the relationships among EWF, microstructure, mechanical and electrochemical properties of low-carbon steel samples with two-level microstructural inhomogeneity, we demonstrate that the overall EWF does carry the information on integrated electron behavior and overall properties of multiphase alloys. This study makes it achievable to develop "electronic metallurgy"-an electronic based novel alternative methodology for materials design.

Hardening tungsten carbide by alloying elements with high work function

There is intensive searching for superhard materials in both theoretical and experimental studies. Refractory and transition metal carbides are typical materials with high hardness. In this study, first-principles calculations were performed first to analyze the electronic structures and mechanical properties of the tungsten-carbide-based compounds. The results indicated that tungsten carbide could be hardened by alloying elements with high work functions to tailor the Fermi level and electron density. Guided by the calculations, a new type of tungsten carbide alloyed with Re was synthesized. The Young's modulus and hardness of the Re-alloyed tungsten carbide are increased by 31% and 44%, respectively, as compared with those of tungsten carbide. This study provides a new methodology to design superhard materials on a feasible electronic base using work function as a simple guiding parameter.

Evaluation of interfacial stability and strength of cermets based on work function

A new method based on work function to analyze the interfacial stability and strength of ceramic-metal composites was proposed in this work. The interfacial work function gradient and interfacial elastic modulus were evaluated experimentally using WC-Co and TiC-Co as the examples. It found that a stable and strongly bonded interface had a gradually changing interfacial work function, while a weak interface exhibited a steep work function changing across the interface. The spatial resolution of the experimental analysis could be down to 10 nm with a high work function sensitivity. First-principles calculations were conducted to analyze the electronic configurations across the interfaces. They revealed the potential distribution across the interfaces in the sub-nano scale. They demonstrated that the interface with a smaller interfacial work function gradient had smaller interface energy and stronger interfacial bonds, and thus the interface was more stable and stronger. The calculation disclosed the mechanism of the experimental observations of the interfacial work function. Both the experimental and theoretical studies confirmed that the interfacial work function gradient could be a measure of the interactions across the interfaces. The effectiveness of the established model was demonstrated by analyzing the stability of thin films at WC/Co interfaces. This study provides a new method to evaluate the interfacial stability and bonding strength for cermets.

Crystallographic anisotropy in surface properties of brass and its dependence on the electron work function

The crystallographic anisotropy of the electric current or conductance, adhesive force, elastic modulus, and deformation magnitude of alpha brass were investigated through property mapping using an atomic force microscope. Surface electron work functions of differently oriented grains in the brass were also analyzed using atomic force microscopy. The mapped surface properties are closely related to the electron work function; the work function reflects the surface activity, which is itself dependent on the surface energy. The anisotropy of the properties is closely correlated to the in situ measured surface electron work function. It is demonstrated that crystallographic planes with higher electron work functions exhibit lower current, smaller adhesive forces, larger elastic moduli and smaller deformation magnitudes. Efforts are made to understand the relationships by connecting the properties with surface energy and electron work function. The dependence of the properties on crystallographic orientation can be elucidated by considering the surface electron behavior using electron work function as a novel probing parameter.

Electron work function - a probe for interfacial diagnosis

A poor interface or defected interfacial segment may trigger interfacial cracking, loss of physical and mechanical functions, and eventual failure of entire material system. Here we show a novel method to diagnose local interphase boundary based on interfacial electron work function (EWF) and its gradient across the interface, which can be analyzed using a nano-Kelvin probe with atomic force microscope. It is demonstrated that a strong interface has its electron work function gradually changed across the interface, while a weaker one shows a steeper change in EWF across the interface. Both experimental and theoretical analyses show that the interfacial work function gradient is a measure of the interaction between two sides of the interface. The effectiveness of this method is demonstrated by analyzing sample metal-metal and metal-ceramic interfaces.