Abstract:Single crystal 6H-SiC wafers with 4° off-axis [0001] orientation were irradiated with carbon ions and then annealed at 900 °C for different time periods. The microstructure and surface morphology of these samples were investigated by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Ion irradiation induced SiC amorphization, but the surface was smooth and did not have special structures. During the annealing process, the amorphous SiC w… Show more
“…In experimental research of recent years, Jones [82,83] uncovered an interstitial type dislocation called end-of-range (EOR) damage through TEM micrographs, just below the crystalline / amorphous interface by Ge + -implanted silicon. Ye et al [84] illustrated recrystallization process of carbon irradiated 6H-SiC, and found the volume shrinkage and the anisotropy of the new born crystal during annealing process generated internal stress, which not only produced a large number of dislocation walls but also caused the initiation and propagation of cracks. Hence, the crack propagation or glide of pre-existing basal-plane dislocations can be suppressed by improving the temperature gradient inside the annealing furnace in actual processing [85].…”
Section: Structural Evolution During Annealing Recrystallizationmentioning
“…In experimental research of recent years, Jones [82,83] uncovered an interstitial type dislocation called end-of-range (EOR) damage through TEM micrographs, just below the crystalline / amorphous interface by Ge + -implanted silicon. Ye et al [84] illustrated recrystallization process of carbon irradiated 6H-SiC, and found the volume shrinkage and the anisotropy of the new born crystal during annealing process generated internal stress, which not only produced a large number of dislocation walls but also caused the initiation and propagation of cracks. Hence, the crack propagation or glide of pre-existing basal-plane dislocations can be suppressed by improving the temperature gradient inside the annealing furnace in actual processing [85].…”
Section: Structural Evolution During Annealing Recrystallizationmentioning
“…Owing to the advanced physical and chemical stability properties, silicon carbide (SiC) and SiC‐fiber‐reinforced SiC matrix composites, have been regarded as a promising material for advanced nuclear energy application . It has been extensively investigated irradiation effects in the high purity SiC and composite, including neutron, ion, and electron irradiation . In addition, the corrosion resistance of the SiC materials has been investigated in the high‐pressure and high‐temperature water and molten salt …”
The corrosion behavior of 4H-SiC in lead-bismuth (Pb-Bi) eutectic (LBE) at 550°C is investigated. To clarify the effect of irradiation damage on corrosion, samples with and without Si 5+ ion irradiation are contrastively evaluated. The main results show that dissolution corrosion occurs in both unirradiated and irradiated samples, while the irradiation damage can accelerate the corrosion rate. The corroded surface is characterized by the loss of C element and the formation of amorphous layers with a slight enrichment of Si atoms. The possible reasons are discussed. K E Y W O R D S corrosion, microstructure, nuclear materials, radiation damage, SiC
“…The kinetics of mold flux isothermal crystallization involving nucleation and growth are analyzed through the Johnson–Mehl–Avrami (JMA) model [27,28,29,30]. According to the JMA model, the volume fraction of crystals X ( t ) is given by:
where X ( t ) is the relative degree of crystallinity at a given time t , including the incubation time, n is the Avrami exponent, which is associated with the nucleation and growth mechanism, and k is the effective crystallization rate constant, which is dependent on the temperature and the rate of nucleation and crystal growth.…”
How to coordinate the contradiction between lubrication and heat transfer in the peritectic steel casting process is the key technical difficulty in preparing mold fluxes. The mold fluxes that are required for casting are subjected to the shear stress generated by mold oscillation and slab movement, which affects the crystallization performance of slags. The quantitative effect of slags’ crystallization performance by shear stress is studied to develop a low-basicity and high-crystallization mold flux to solve the above problem. The results show that the crystallization kinetic condition is promoted, and the crystallization activation energy is reduced by the shear stress, which leads to an increase in the crystallization temperature. Concurrently, the crystal size is reduced. However, the shear stress has no effect on the crystalline phase. The influence of different shear stresses on the crystallization ability of molten slags is related to the crystal nucleation and growth mechanisms. The crystalline fraction of the slag films at 300 rpm (69 s−1) is 44.7%, which is an increase of 17.7% compared with the crystalline fraction of the slag films at 200 rpm (46 s−1). Moreover, the shear stress has little effect on the lubricating properties of the mold fluxes, although the crystallization ability is promoted by the agitation.
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