The Study of Graphene Oxide on the Regulations and Controls of the Sol-Gel Film Structure and Its Performance

A facile strategy to boost anticorrosion potency of graphene oxide/silica hybrid sol-gel coating is developed through fully exploiting the capabilities of graphene oxide (GO). Together with a barrier to corrosives and crack inhibitor, GO was further explored herein as a regulator to regulate the gelation process and provide robust coating films with stratified microstructures and ultimately extended diffusion paths. The sol-gel coating with stratified microstructure achieved on AA5052 aluminum alloy surface afforded greatly enhanced corrosion protection capability as assessed by electrochemical measurements and immersion tests. The corrosion current density of the sample of a hybrid GO sol-gel film was about 30 times less than that of sample of pure sol-gel film sample. The regulation mechanism of GO during the film formation process and the anticorrosive protection properties of the film were discussed.

2D Porous Nb4N5@Nb2C Heterojunctions for High-Performance Li-ion Batteries

Constructing transition metal nitrides (TMNs) with a 2D porous structure is an effective strategy to alleviate their volume expansion and self-aggregation issues, eventually enhancing their electrochemical performance. However, very few studies have been reported up to now. Herein, 2D porous Nb4N5@Nb2C heterojunctions are successfully synthesized from Nb2C MXene precursor by employing a two-step nitridation method in NH3 atmosphere. Owing to the abundant active sites, fast Li-ions diffusion paths, and sufficient buffer space for releasing volume expansion, 2D porous Nb4N5@Nb2C heterojunctions achieve high rate performance and excellent cycling stablility, maintaining 109.2 mAh g-1 at 2 A g-1 after 800 cycles. This work provides a facile strategy for building 2D porous TMNs and their heterojunctions with excellent electrochemical performances.

Effect of Bonding Strength on Electromigration Failure in Cu–Cu Bumps

In microelectronic packaging technology for three-dimensional integrated circuits (3D ICs), Cu-to-Cu direct bonding appears to be the solution to solve the problems of Joule heating and electromigration (EM) in solder microbumps under 10 μm in diameter. However, EM will occur in Cu–Cu bumps when the current density is over 106 A/cm2. The surface, grain boundary, and the interface between the Cu and TiW adhesion layer are the three major diffusion paths in EM tests, and which one may lead to early failure is of interest. This study showed that bonding strength affects the outcome. First, if the bonding strength is not strong enough to sustain the thermal mismatch of materials during EM tests, the bonding interface will fracture and lead to an open circuit of early failure. Second, if the bonding strength can sustain the bonding structure, voids will form at the passivation contact area between the Cu–Cu bump and redistribution layer (RDL) due to current crowding. When the void grows along the passivation interface and separates the Cu–Cu bump and RDL, an open circuit can occur, especially when the current density and temperature are severe. Third, under excellent bonding, when the voids at the contact area between the Cu–Cu bump and RDL do not merge together, the EM lifetime can be more than 5000 h.

Nitriding and Ferritic Nitrocarburizing of Quenched and Tempered Steels

A physics-based software model is being developed to predict the nitriding and ferritic nitrocarburizing (FNC) performance of quenched and tempered steels with tempered martensitic microstructure. The microstructure of the nitrided and FNC steels is comprised of a white compound layer of nitrides (ε and γ’) and carbides below the surface with a hardened diffusion zone (i.e., case) that is rich in nitrogen and carbon. The composition of the compound layer is predicted using computational thermodynamics to develop alloy specific nitriding potential KN and carburizing potential KC phase diagrams. The thickness of the compound layer is predicted using parabolic kinetics. The diffusion in the tempered martensite case is modeled using diffusion with a reaction. Diffusion paths are also developed on these potential diagrams. These model predictions are compared with experimental results.

Adsorption and Surface Diffusion of Metals on α-Al2O3 for Advanced Manufacturing Applications

The adsorption and diffusion of Mo and Nb adatoms on the $$\alpha$$ α -Al2O3 (0001) surface were explored using density functional theory-based methods. Adsorption energies of Mo and Nb adatoms at minima sites on the surface were determined. Mo and Nb adatoms prefer to adsorb to the same locations on the surface, and larger adsorption energies calculated for Nb compared to Mo indicate that Nb adatom-surface interactions are stronger than Mo. Using minima adsorption sites as initial and final locations for surface diffusion, energy barriers for diffusion were calculated using the nudged elastic band method. Overall, Mo and Nb follow roughly the same diffusion paths. The diffusion pre-factors for Mo and Nb are similar; however, Mo diffusion has a lower energy barrier and thus a larger diffusion coefficient compared with Nb. These results provide insight into the role of surface diffusion of Mo and Nb adatoms during advanced manufacturing processes.

Adsorption and diffusion of Li/Na atom on blue phosphorene with defects by first-principles calculations

Two-dimensional materials such as blue phosphorene (BlueP) as a substitute for conventional anode materials in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) have garnered significant attention recently because of their large surface areas, ultrafast intrinsic carrier mobilities, and shorter ion diffusion paths. In this study, the adsorption and diffusion properties of Li and Na ions on BlueP with defects are investigated through first-principles calculations. The calculations show that the binding energy increased from -0.64 to -1.50 eV for Li and from -0.72 to -1.61 eV for Na because of defects. Moreover, the defects resulted in middle bands in the density of states of BlueP, indicating enhanced electron localization. This may contribute to an increase in binding energies. However, it is discovered that Li and Na ion diffusion on the surface of BlueP with defects involves a larger migration energy barrier than Li and Na on pristine BlueP, which is disadvantageous to BlueP as a battery anode.

Structural, electrical characterization and oxygen-diffusion paths in LaSrGa1-xMgxO4-δ (x=0.0-0.2) layered perovskites: an impedance spectroscopy and neutron diffraction study

This work presents the results of the structural characterization of LaSrGa1-xMgxO4-δ oxides with x=0.0-0.2 (LSGM'); these oxides with layered K2NiF4-type structure are potential electrolytes of oxygen ions with applications in...

Bottleneck links, essential intermediaries, and competing paths of diffusion in networks

We investigate how information goods are priced and diffused over links in a network. A new equivalence relation between nodes captures the effects of network architecture and locations of sellers on the division of profits, and characterizes the topology of competing (and potentially overlapping) diffusion paths. Sellers indirectly appropriate profits over intermediation chains from buyers in their equivalence classes. Links within the same class constitute bottlenecks for information diffusion and confer monopoly power. Links that bridge distinct classes are redundant for diffusion and generate competition among sellers. In dense networks, competition limits the scope of indirect appropriability and intellectual property rights foster innovation.

Practical strategies for enhanced performance of anode materials in Na+/K+-ion batteries

In this review, the effects of different strategies, such as engineering heterojunctions or diffusion paths, and designing alloys or hollow structures, are discussed in order to address the problems faced by the anode materials for SIBs/PIBs.