During the production of the inner walls of ovens,pit defects were formed on the surface of the enamel layer that was enameled on the cold-rolled steel via electrostatic powder spraying and sintering.The paper elabora...During the production of the inner walls of ovens,pit defects were formed on the surface of the enamel layer that was enameled on the cold-rolled steel via electrostatic powder spraying and sintering.The paper elaborates on the microstructure and element distribution of the enamel-steel interface and the enamel layer.Optical microscopy,scanning electron microscopy,and energy-dispersive spectroscopy were adopted to investigate the microstructure of a longitudinal section of the defect,and the pit-forming causes were analyzed.The results show that rusty spots lead to pit defects.During high-temperature firing,there is an inadequate fusion and reaction between iron oxides of the rusty spots and the enamel glaze.The rusty spots are closely related to pretreatment process;thus,to avoid their occurrence,electrostatic powder spraying and sintering should be performed timely after forming,degreasing,and thorough drying of the metal sheets.展开更多
Surface potentials in the vicinity of V-pits(cone bottom) and U-pits(blunt bottom) on epitaxial GaN surface have been systematically studied using ultraviolet(UV) light-assisted Kelvin probe force microscopy(KPFM). Th...Surface potentials in the vicinity of V-pits(cone bottom) and U-pits(blunt bottom) on epitaxial GaN surface have been systematically studied using ultraviolet(UV) light-assisted Kelvin probe force microscopy(KPFM). The band structure models are established to understand variation of the surface potentials at the pits and planar surface with and without UV light. The photo-generated carrier behavior at the pit defects is studied. According to the surface potential results, it can be deduced that the carrier distributions around the V-and U-pits are uneven. In dark, the electron concentration at the bottom of V-pit(30 n_0) and Upit(15 n_0) are higher than that at planar surface(n_0). Under UV light, for V-pit, the electron concentration at the cone bottom(4.93×10^(11) n_0) is lower than that at the surrounding planar surface(5.68×10^(13) n_0). For U-pit, the electron concentration at the blunt bottom is 1.35×10^(12) n_0, which is lower than that at the surrounding planar surface(6.13×10^(13) n_0). The non-equilibrium electron concentrations at different locations are calculated. Based on the non-equilibrium electron concentration, it can be concluded that the carrier recombination rate at pit defects is higher than that at planar surface.展开更多
This paper employs micro-Raman technique for detailed analysis of the defects （both inside and outside） in bulk 4H-SiC. The main peaks of the first-order Raman spectrum obtained in the centre of defect agree well wi...This paper employs micro-Raman technique for detailed analysis of the defects （both inside and outside） in bulk 4H-SiC. The main peaks of the first-order Raman spectrum obtained in the centre of defect agree well with those of perfect bulk 4H-SiC, which indicate that there is no parasitic polytype in the round pit and the hexagonal defect. Four electronic Raman scattering peaks from nitrogen defect levels are observed in the round pit （395 cm^-1, 526 cm^-1, 572cm^-1, and 635cm^-1）, but cannot be found in the spectra of hexagonal defect. The theoretical analysis of the longitudinal optical plasmon-phonon coupled mode line shape indicates the nonuniformity of nitrogen distribution between the hexagonal defect and the outer area in 4H-SiC. The second-order Raman features of the defects in bulk 4H-SiC are well-defined using the selection rules for second-order scattering in wurtzite structure and compared with that in the free defect zone.展开更多
La2CuO4 and La1.86Sr0.14CuO4 single crystals were obtained by traveling solvent floating zone method. There were five kinds of defects in these single crystals: cracks, inclusions, gas bubbles, unhomogeneous distribut...La2CuO4 and La1.86Sr0.14CuO4 single crystals were obtained by traveling solvent floating zone method. There were five kinds of defects in these single crystals: cracks, inclusions, gas bubbles, unhomogeneous distribution of Sr2+, and substructures. CH3COOH aqueous solution was used to etch these single crystals, and the etch-pit density was calculated. The fort-nation mechanism of these defects was discussed. It is suggested that the good preparation of raw materials and the stringent growth conditions play an important role in growing high quality single crystals.展开更多
文摘During the production of the inner walls of ovens,pit defects were formed on the surface of the enamel layer that was enameled on the cold-rolled steel via electrostatic powder spraying and sintering.The paper elaborates on the microstructure and element distribution of the enamel-steel interface and the enamel layer.Optical microscopy,scanning electron microscopy,and energy-dispersive spectroscopy were adopted to investigate the microstructure of a longitudinal section of the defect,and the pit-forming causes were analyzed.The results show that rusty spots lead to pit defects.During high-temperature firing,there is an inadequate fusion and reaction between iron oxides of the rusty spots and the enamel glaze.The rusty spots are closely related to pretreatment process;thus,to avoid their occurrence,electrostatic powder spraying and sintering should be performed timely after forming,degreasing,and thorough drying of the metal sheets.
基金supported by the National Key R&D Program of China(Grant No.2016YFB0400101)the National Science Fund for Distinguished Young Scholars(Grant No.61725403)+8 种基金the National Natural Science Foundation of China(Grant Nos.61574142,61322406,61704171,and11705206)the National Natural Science Foundation of China(Grant No.61774065)the Key Program of the International Partnership Program of Chinese Academy of Sciences(Grant No.181722KYSB20160015)the Special Project for Inter-government Collaboration of the State Key Research and Development Program(Grant No.2016YFE0118400)the Science and Technology Service Network Initiative of the Chinese Academy of Sciences,the Jilin Provincial Science&Technology Department(Grant No.20180201026GX)the CAS Interdisciplinary Innovation Team,and the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2015171)the support of King Abdullah University of Science and Technology(KAUST)Baseline(Grant No.BAS/1/1664-01-01)the Competitive Research(Grant No.URF/1/3437-01-01)Gulf Cooperation Council(GCC)Research Council(Grant No.REP/1/3189-01-01)
文摘Surface potentials in the vicinity of V-pits(cone bottom) and U-pits(blunt bottom) on epitaxial GaN surface have been systematically studied using ultraviolet(UV) light-assisted Kelvin probe force microscopy(KPFM). The band structure models are established to understand variation of the surface potentials at the pits and planar surface with and without UV light. The photo-generated carrier behavior at the pit defects is studied. According to the surface potential results, it can be deduced that the carrier distributions around the V-and U-pits are uneven. In dark, the electron concentration at the bottom of V-pit(30 n_0) and Upit(15 n_0) are higher than that at planar surface(n_0). Under UV light, for V-pit, the electron concentration at the cone bottom(4.93×10^(11) n_0) is lower than that at the surrounding planar surface(5.68×10^(13) n_0). For U-pit, the electron concentration at the blunt bottom is 1.35×10^(12) n_0, which is lower than that at the surrounding planar surface(6.13×10^(13) n_0). The non-equilibrium electron concentrations at different locations are calculated. Based on the non-equilibrium electron concentration, it can be concluded that the carrier recombination rate at pit defects is higher than that at planar surface.
基金supported by the National Defense Pre-Research Foundation of China (Grant Nos 51308030201 and 51323040118)
文摘This paper employs micro-Raman technique for detailed analysis of the defects （both inside and outside） in bulk 4H-SiC. The main peaks of the first-order Raman spectrum obtained in the centre of defect agree well with those of perfect bulk 4H-SiC, which indicate that there is no parasitic polytype in the round pit and the hexagonal defect. Four electronic Raman scattering peaks from nitrogen defect levels are observed in the round pit （395 cm^-1, 526 cm^-1, 572cm^-1, and 635cm^-1）, but cannot be found in the spectra of hexagonal defect. The theoretical analysis of the longitudinal optical plasmon-phonon coupled mode line shape indicates the nonuniformity of nitrogen distribution between the hexagonal defect and the outer area in 4H-SiC. The second-order Raman features of the defects in bulk 4H-SiC are well-defined using the selection rules for second-order scattering in wurtzite structure and compared with that in the free defect zone.
文摘La2CuO4 and La1.86Sr0.14CuO4 single crystals were obtained by traveling solvent floating zone method. There were five kinds of defects in these single crystals: cracks, inclusions, gas bubbles, unhomogeneous distribution of Sr2+, and substructures. CH3COOH aqueous solution was used to etch these single crystals, and the etch-pit density was calculated. The fort-nation mechanism of these defects was discussed. It is suggested that the good preparation of raw materials and the stringent growth conditions play an important role in growing high quality single crystals.
