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
对Φ22 mm Q235-B圆钢进行了塔形试验、冷顶锻试验和轧制过程坯料低倍金相检验。结果表明:圆钢冷顶锻H/3级别的性能保证能力较差,但无缺陷碳结圆钢H/2级别的冷顶锻完好率有保证,有缺陷的碳结圆钢性能保证能力较差;轧制过程中各道次的不...对Φ22 mm Q235-B圆钢进行了塔形试验、冷顶锻试验和轧制过程坯料低倍金相检验。结果表明:圆钢冷顶锻H/3级别的性能保证能力较差,但无缺陷碳结圆钢H/2级别的冷顶锻完好率有保证,有缺陷的碳结圆钢性能保证能力较差;轧制过程中各道次的不均匀变形和挤压褶皱造成了圆钢表面的长条形缺陷,而表面和近表面缺陷是造成冷顶锻开裂的主要原因。展开更多
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.
文摘对Φ22 mm Q235-B圆钢进行了塔形试验、冷顶锻试验和轧制过程坯料低倍金相检验。结果表明:圆钢冷顶锻H/3级别的性能保证能力较差,但无缺陷碳结圆钢H/2级别的冷顶锻完好率有保证,有缺陷的碳结圆钢性能保证能力较差;轧制过程中各道次的不均匀变形和挤压褶皱造成了圆钢表面的长条形缺陷,而表面和近表面缺陷是造成冷顶锻开裂的主要原因。
