Aluminum ablation by multiple femtosecond laser pulses is investigated via time-resolved shadowgraphs and scanning electron microscope （SEM） images of the ablation spot. The spatial distribution of the ejected mater...Aluminum ablation by multiple femtosecond laser pulses is investigated via time-resolved shadowgraphs and scanning electron microscope （SEM） images of the ablation spot. The spatial distribution of the ejected material and the radius of the shock wave generated during the ablation are found to vary with the increase in the number of pulses. In the initial two pulses, nearly concentric and semicircular stripes within the shock wave front are observed, unlike in subsequent pulses. Ablation by multiple femtosecond pulses exhibits different characteristics compared with the case induced by single femtosecond pulse because of the changes to the aluminum target surface induced by the preceding pulses.展开更多
We investigate the thermal expansion property of the Tb2Fe14Cr3 compound by means of The result shows that the Tb2Fe14Cr3 compound has a hexagonal Th2Ni17-type structure x-ray diffraction. Negative thermal expansion i...We investigate the thermal expansion property of the Tb2Fe14Cr3 compound by means of The result shows that the Tb2Fe14Cr3 compound has a hexagonal Th2Ni17-type structure x-ray diffraction. Negative thermal expansion is found in the Tb2Fe14Cr3 compound from 296 to 493K by x-ray dilatometry. The coefficient of the average thermal expansion is α^- = -2.82×10^-5 K^-1. In the temperature range 493-692K, the coefficient of the average thermal expansion is α^- = 1.59×10^-5 K^-1. The physical mechanism of thermal expansion anomaly of the Tb2Fe14Cr3 compound is discussed according to the temperature dependence of magnetization measured by a superconducting quantum interference device.展开更多
基金Project supported by the Science and Technology Development Fund Planning Project for the Universities of Tianjin,China(Grant No.20140902)the Natural Science Foundation of Tianjin City,China(Grant No.16JCQNJC01900)+1 种基金the National Natural Science Foundation of China(Grant Nos.51376136and 61474082)the Science and Technology Achievement Award Project for the Universities of Tianjin,China
文摘Aluminum ablation by multiple femtosecond laser pulses is investigated via time-resolved shadowgraphs and scanning electron microscope （SEM） images of the ablation spot. The spatial distribution of the ejected material and the radius of the shock wave generated during the ablation are found to vary with the increase in the number of pulses. In the initial two pulses, nearly concentric and semicircular stripes within the shock wave front are observed, unlike in subsequent pulses. Ablation by multiple femtosecond pulses exhibits different characteristics compared with the case induced by single femtosecond pulse because of the changes to the aluminum target surface induced by the preceding pulses.
基金Supported by the National Natural Science Foundation of China under Grant No 50271022.
文摘We investigate the thermal expansion property of the Tb2Fe14Cr3 compound by means of The result shows that the Tb2Fe14Cr3 compound has a hexagonal Th2Ni17-type structure x-ray diffraction. Negative thermal expansion is found in the Tb2Fe14Cr3 compound from 296 to 493K by x-ray dilatometry. The coefficient of the average thermal expansion is α^- = -2.82×10^-5 K^-1. In the temperature range 493-692K, the coefficient of the average thermal expansion is α^- = 1.59×10^-5 K^-1. The physical mechanism of thermal expansion anomaly of the Tb2Fe14Cr3 compound is discussed according to the temperature dependence of magnetization measured by a superconducting quantum interference device.
