Simulation on Influence of Wall Thickness and Probe Channel Numbers on the Examination Rate of Oxides Blocking Ratio in non-Ferromagnetic Tubes

Oxides accumulated in the inner bend of austenite heating tubes of super critical units may cause overheat and bursting. Traditional methods could not examine oxides blocking ratio. A magnetic field simulation of the boiler tube’s oxide skin blockage model has been set up in this paper. The influence of different wall thickness and different accumulation of oxide on the distribution of magnetic field was analyzed. It was demonstrated that the blockage oxide scale could be quantitatively measured by the amplitude and distribution of magnetic field.

Gallium Liquid Metal: The Devil's Elixir

Gallium is a metal that literally melts in your hand. It has low toxicity, near-zero vapor pressure, and a viscosity similar to water. Despite possessing a surface tension larger than any other liquid (near room temperature), gallium can form nonspherical shapes due to the thin, solid native oxide skin that forms rapidly in oxygen. These properties enable new ways to pattern metals (e.g., injection and printing) to create stretchable and soft devices with an unmatched combination of mechanical and electrical properties. The oxide skin can be transferred to other substrates and manipulated electrochemically to lower the interfacial tension to near zero. The reactivity of gallium can drive a wide range of reactions. Liquids are also easy to break into particles for making colloids and soft composites that have unusual properties due to the deformable nature of the filler. This review summarizes the truly unique and exciting properties of gallium liquid metals. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is August 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Smooth transportation of liquid metal droplets in a microchannel as detected by a serially arranged capacitive device

Gallium alloy liquid metals (Galinstan) possessing fluidity, electric conductivity, and low toxicity are attractive for use in flexible devices and microfluidic devices. However, the oxide skin of Galinstan in the atmosphere adheres to the microchannel surface, preventing the transportation of Galinstan in the channel. To tackle the problem of the adhesion of Galinstan to microchannel, we introduced liquid with Galinstan into a channel with a diameter of 1000 μm. Then, we found that the cylindrical shape of the channel enabled smooth transportation of Galinstan independently of both the liquid and the channel material. The liquid introduced with Galinstan not only prevents adhesion but also improves the spatial controllability of Galinstan in the channel. We can control the position of Galinstan with 100 μm resolution using highly viscous (> 10 cSt) liquid. In addition, we combined the microchannel with patterned electrodes, fabricating a serially arranged capacitive device. The local capacitance detected by the patterned electrodes changed by more than 6% via the smooth transportation of Galinstan. The analysis results based on an equivalent circuit quantitatively agree with our experimental results. We can modulate the serially arranged capacitors using the smooth transportation of Galinstan in the channel.

Smooth Transportation of Liquid Metal Droplets in a Microchannel as Detected by a Serially Arranged Capacitive Device

Gallium alloy liquid metals (Ga-LMs) possessing fluidity, electric conductivity, and low toxicity are attractive for use in flexible devices and microfluidic devices. However, the oxide skin of Ga-LMs in the atmosphere adheres to the microchannel surface, preventing the transportation of Ga-LMs in the channel. We introduced liquid with Ga-LMs into a channel with a radius of 500 µm to prevent the oxide skin of the Ga-LM from adhering to the channel. Then, we found that the cylindrical shape of the channel enabled smooth transportation of Ga-LMs independently of both the liquid and the channel material. The liquid introduced with Ga-LMs not only prevents adhesion but also improves the spatial controllability of Ga-LMs in the channel. We can control the position of Ga-LMs with 100 µ m resolution using highly viscous (> 10 cSt) liquid. In addition, we combined the microchannel with patterned electrodes, fabricating a serially arranged capacitive device. The local capacitance detected by the patterned electrodes changed by more than 6 % via the smooth transportation of Ga-LMs. The analysis results based on an equivalent circuit quantitatively agree with our experimental results. We can modulate the serially arranged capacitors using the smooth transportation of Ga-LMs in the channel.

Influence of Grain Refiners on the Wettability of Al2O3 Substrate by Aluminum Melt

It is well known that grain refiner additions in aluminum melts significantly reduce the filtration efficiency of ceramic foam filters (CFF). However, the mechanism remains unclear. In this work, the influence of grain refiners on the wettability of alumina substrate by aluminum melt was studied by both conventional sessile drop and improved sessile drop methods at different temperatures and vacuums. Commercial purity aluminum (CP-Al) and grain refiner master alloys Al-3Ti-1B, Al-5Ti-1B, Al-3Ti-0.15C were used. It is found that master alloy melts wet alumina substrate better than CP-Al. Generally, a lower temperature or lower vacuum results in a higher contact angle. The roles of grain refiner particles in improving the wettability were studied by analyzing the solidification structure of post wetting-test droplets using SEM. Strong sedimentation of grain refiner particles at the metal-substrate interface was observed, which is attributed to the higher density of grain refiner particles compared to the Al melt. Meanwhile, a large fraction of grain refiner particles agglomerates at the oxide skin of the aluminum droplets, showing a strong adhesion between the particles and oxide skin. Such adhering of grain refiner particles is proposed to enhance the rupture of the original oxide skin of the droplets and slow down the reoxidation process at the surface layer. Both adherence of grain refiner particles to surface oxide skin and sedimentation of particles at the metal-substrate interface are responsible for the wetting improvement.

Efficient hydrogen evolution reaction with platinum stannide PtSn4via surface oxidation

The outstanding performance of PtSn4 in HER is related to the presence of a sub-nanometric tin-oxide skin formed after surface oxidation.