Ming-Yuan Lin

This study aims to investigate the wear and corrosion–wear behavior of 17-4PH stainless steel specimens, both fabricated via Selective Laser Melting (SLM) and conventional bulk material, after undergoing Solution Treatment (S.T.) in a seawater medium. Microstructural observations indicated that solution treatment contributed to a more uniform distribution of martensitic structures on the sample surface. Moreover, the solution-treated specimens exhibited improved microstructural uniformity and structural stability. SLM specimens exhibit the elimination of fine particles and scanning track traces. Based on the results of dynamic polarization tests, SLM specimens demonstrate superior corrosion resistance. However, in corrosion–wear conditions, the bulk material outperforms the SLM specimens, primarily due to the presence of pores in the latter, which are detrimental under such environments. XPS analysis of the passive film structure indicates that the passive layer is mainly composed of FeO, Cr₂O₃, and NiO, with the inner layer predominantly consisting of chromium oxide. The Cr₂O₃ layer, formed by the reaction between chromium and oxygen, significantly enhances the corrosion resistance of the material due to its extremely low chemical reactivity and high stability.

Through-mask electrochemical micromachining (TMEMM) is a kind of microfabrication. The major feature of through-mask electrochemical micromachining is that the tool is not limited by the shape, and can be processed in various shapes according to the pattern on the mask. This paper uses the finite element method to create a three-dimensional model to discuss the influence of flow direction, voltage, and electrolyte flow rate on the shape of the through-mask electrochemical micromachining. The simulation results show that processing shape is deeply affected by processing parameters, electrolyte flow rate affects processing temperature distribution, and temperature distribution at the bottom of aperture affects processing depth and flatness during processing, which in turn causes the difference in orifice size and roundness. At the same flow rate, the larger voltage, the larger average radius, flatness, and roundness. At the same voltage, the faster flow rate, the lower average depth, flatness, and average radius. Overall, it has best-processed aperture profile at a flow rate of 0.5 m/s. As a whole, the through-mask electrochemical micromachining is indeed suitable for array microfabrication of various shapes. In this study, experiments were added to verify the simulation results. At a fixed electrolyte flow rate, when the voltage, concentration, and mask aperture are changed, it will have an effect on the overall experimental results. From the experimental results, we know that the electrolyte flow rate and temperature distribution will indeed affect the overall processability.

In this study, sulfuric acid and potassium hydroxide are used as the electrolytes, separated by proton exchange membrane, to produce hydrogen. The effects of electrolyte concentrations, applied voltage, single or dual cells, and temperature on the hydrogen production rate and energy efficiency are investigated. Experimental results show that the amount of hydrogen production increases with voltage, and the dual electrolytes and cells can yield the best hydrogen production rate and energy efficiency. With 1-M KOH plus 1-M H₂SO₄ as electrolytes in separated cells, the highest hydrogen production rate is about 0.95 L/hr. Results also show that the rise of electrolyte temperature can significantly increase the hydrogen production rate up to 50%, and the energy efficiency up to 20%. Keeping a low PH value in cathodeand high anode PH value in anode indeed enhances the efficiency of hydrogen production rate.

The effect of magnetic force on the hydrogen production by multielectrode water electrolysis is experimentally investigated in this paper. Results show that the hydrogen production rate, power increase rate and energy efficiency are improved as the magnetic field is added during the electrolysis process. At conditions of interelectrode distance of 3 mm, electrode pair of 5, electrolyte concentration of 25 wt% and applied voltage of 3 V, the hydrogen production reaches maximum amount of 5300 ml/h. At applied voltage of 2.5 V, energy efficiency can reach 92.14% as the magnetic field is added. The increase rate of hydrogen production is 13.4%, while increase rate of power efficiency is 10.2%, higher than that without magnetic field added. It indicated that the external magnetic field during water electrolysis indeed improves the electrolysis procedure.

Hydrogen production by water electrolysis is one of the promising ways for sustainable energy. The influences of magnetic field on the covering ratio and the upward velocity of the bubbles during water electrolysis in different working conditions are investigated by the use of a high-speed camera. Results show that the upward moving velocities of bubbles are increased while the covering ratios of bubbles are increased, under different inter-electrode distances and current density under the magnetic effect. The bubbles are more uniformly distributed on the electrode and the corresponding averaged diameters are decreased. At an inter-electrode distance of 2 mm and current density of 0.3 A/cm², the bubble flow rate is increased by 67.8% as the magnetic field is added, while it is about 42.0% at an inter-electrode distance of 5 mm and current density of 0.3 A/cm². Without extra energy consumption, the addition of magnetic field to increase the efficiency of hydrogen production by water electrolysis is proved.

During a time of high energy consumption, water electrolysis is currently one of the alternative energy sources. At low voltages and low concentrations where activation and concentration polarizations are most dominant, the polarization effects are most significant and the electrolysis is most inefficient. Whereas at high voltages and high concentrations, the activation and concentration polarizations will quickly diminish, producing better electrolysis results. We can see from the empirical data that when the electrode distance is 2 mm and the electrolyte is 30 wt% KOH, a shorter electrode distance with an appropriate actual electrolysis voltage will produce lower polarization impedance values and hence the best efficiency in electrolysis. This study used electrochemical impedance spectroscopy (EIS) to detect relevant data on resistance. Applying it in the field of water electrolysis can provide another method to detect and clarify the phenomenon of polarization and impedance.