The effects of rare earth elements on the corrosion properties of low‐carbon steel and weathering steel were investigated. To elucidate the roles of rare earth elements (Ce and La) and the corrosion behavior of steels, salt spray tests, electrochemical techniques, X‐ray diffractometer, scanning electron microscopy, Electron Probe Micro Analysis (EPMA), and Auger Electron Spectroscopy (AES) were conducted. The results showed that the addition of rare earth elements enhances the corrosion resistance of both low‐carbon steels and weathering steels, indicated by lower corrosion current density and salt spray corrosion rate after rare earth alloying. On the one hand, rare earth elements modify the morphology of inclusions and thus slow down the micro‐area electrochemical corrosion, which improves the electrochemical corrosion resistance of these two steels. On the other hand, rare earth atoms tend to segregate toward the interface between the rust layer and the matrix. Hence, salt spray corrosion resistance is improved due to the enhancement of adhesion and compactness of the rust by the addition of rare earth elements.
Rare earth (RE) elements are beneficial to improving corrosion properties in low-carbon and low-alloy steels. In this paper, corrosion performance of Q235B steel and Q355B steel samples after RE alloying under wet-dry cycle immersion conditions were analyzed. Experimental results show that corrosion rate was significantly decreased. It was probably due to the grain refinement by RE alloying, which increased the density of protective rust layers and improved corrosion resistance. The formation of small-sized spherical RE inclusions also inhibited the precipitation of MnS and weakened micro galvanic corrosion. Additionally, RE atoms tended to segregate towards grain boundaries and a RE concentration region is formed between rust layers and matrix to impede the access from contacting corrosive ions. A corrosion resistance schematic of RE atom segregation was proposed based on microstructure morphology and element distribution results.
In order to investigate the optimization of the performance and structure of a tungsten crucible CVD reactor, the CFD simulation method was used in this paper to simulate the internal flow of the tungsten crucible CVD reactor. The velocity distribution and temperature distribution in the reactor were obtained. The simulation results show that the axial and radial heat convection will occur between the susceptor and the outer wall surface, but the axial heat convection is more intense. Moreover, it was found that the temperature distribution in the CVD reactor was more uniform and reasonable when the upper gas inlet was applied, which was beneficial to the reduction and deposition processes of tungsten. The molar ratio of H 2 to WF 6 has a great influence on the deposition rate of tungsten, and excess H 2 is not conducive to the deposition of tungsten. Thermal radiation has a great influence on the temperature distribution of CVD reactors. It cannot be neglected.
In the selection of materials for deep‐sea equipment, light weight and high strength are the most important criteria or requirements. In this paper, hollow glass microspheres (HGMS), expanded polystyrene (EPS), epoxy resin (EP) and curing agent were mixed to prepare hollow glass microspheres reinforced epoxy foam balls (HGMS‐EHS) by the rolling ball method. Glass fiber (GF) reinforced epoxy syntactic foam (GF‐ESF) was prepared by mixing HGMS‐EHS, HGMS, EP, GF, and curing agent using compression moulding method. By analyzing the mechanical properties and microscopic morphology of GF‐ESF, the results show that the addition of GF does enhance the compressive strength of epoxy syntactic foam. GF‐ESF has a density of 496 kg/m3, and its compressive strength is 30.48 MPa. By increasing the number of layers of HGMS‐EHS, the diameter of EPS, the density of HGMS and reducing the stacking volume of HGMS‐EHS, the density of ESF increased significantly thus subsequently increase the compressive strength. Therefore, the compressive strength and density should be considered comprehensively and find the best balance point in the process of preparing ESF. This paper could provide some suggestions for the preparation of deep‐sea epoxy composites.
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