A model of investment casting of a titanium alloy gearbox based on the ProCAST software was established in this work, and the simulated result was used to optimize the casting process. The flow and temperature field of casting were simulated based on an actual pouring process. Casting defects and the solidification process were analyzed. The results show that the defects can be predicted by the simulation result exactly, and the simulated temperature field is in accordance with the actual process. Shrinkage and porosity are observably alleviated by remodelling the casting mould. The casting temperature field and solidification simulation results show that the casting defects arise from hot spots and heat accumulation. The temperature-time curve of different representative location nodes of casting further confirms the defect simulation results. In addition, the use of low-cost alloy elements reduces raw material costs. Compared with TC4 alloy, the mechanical properties of the casting remain unchanged.
In this study, β-Ni(OH) 2 with a unique flower-like morphology was synthesized through a hydrothermal method. The doping of Rh in β-Ni(OH) 2 was achieved by a reduction method. The as-synthesized catalysts were characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy for the crystal structure, morphology, composition, and chemical state analysis. The electrochemical tests revealed that the doping of Rh can significantly increase the electrocatalytic performance of β-Ni(OH) 2 in 1.0 M KOH solution. The methanol oxidation peak current density of Rhdoped β-Ni(OH) 2 reached 95 mA cm −2 with a Tafel slope of 40 mV dec −1 . The reason for these improvements is that Rh can suppress the phase transformation of NiOOH from β to α. Meanwhile, the electronic structure change of nickel in β-Ni(OH) 2 and the defect ratio increase caused by Rh doping are beneficial to methanol oxidation reaction (MOR) catalytic activity. Furthermore, the synergistic effect between Rh and Ni(OH) 2 improved the surface activity of β-NiOOH. The doping of Rh in β-Ni(OH) 2 is initiative in this work, which provides a new strategy to design highly efficient and cost-effective MOR electrocatalysts for alkaline DMFCs.
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