PROCESSES OF FORMATION OF OXIDIZED ALUMINUM NANOPOWDERS WHEN ALUMINUM IS EXPOSED TO A SERIES OF DOUBLE LASER PULSES IN THE AIR

Abstract

We studied the effect of the pulse interval and the number of double laser pulses on the formation of the component and charge composition of laser plasma under the influence of these pulses on the AD1 aluminum alloy target (LSS-1 spectrometer). It is shown that when using the inter-pulse interval in the range 7—16 ms, the concentration of Al ions and their interaction products with oxygen and nitrogen in the air increases by several orders of magnitude compared to the zero interval. The dependence of the process of Al ions formation on the pulse energy is investigated for the case of the 10 ms inter-pulse interval. For the 53 mJ pulse energy, the largest intensity of the Al III ion lines is observed for small (about 15) number of consecutive double pulses in the series. When the number of pulses in the series increases above a certain level (10—20), the intensity of the Al III ion lines decreases by about 5 times, which is due to their active interaction with air molecules and atoms at the exit of the micro-nozzle when the channel shape is changed. The temperature in the plasma region with the maximum Al III content gave values equal to approximately 22000—30000 K. Al nanopowders coated with a layer of aluminum oxide obtained by irradiating an aluminum target with a series of 15 double pulses per point mainly have a size of 50—60 nm.