Research On Growth Of SiC Nano-whisker By Nd:yag Laser Irradiation

Laser processing which use laser as a heater, had been paid high attention in the field of nano-meterials' preparation,because of its high instant energy density and ultrafast heating efficiency.when laser irradiated the materials, it showed the gauss distribution in the space,and created its temperature field as gradient distribution which made materials' preparation also present gradient distribution.In-situ growth of SiC nano-whiskers by direct laser irradiation on SiC nano-particles was investigated in this paper.By compared with CO₂ laser and Nd:YAG laser, steady process parameters and growth mechanism of SiC nano-whiskers by laser irradiation were researched.The main work and conclusions were presented as follows:1. By compared with CO₂ laser and Nd:YAG laser, the two kinds of lasers' similarities and differences were researched in wavelength,spatial distribution,laser's working mode and the materials' absorptivity.2. Choose CO₂ laser for example, laser beam was simplified as fundamental gauss beam model. The model of SiC nano-particles by laser irradiation and temperature field of the irradiation layer were established and analyzed, which could be used as a guidance to select the laser parameter in the experiment.3. The experiment of laser irradiation was used Nd:YAG laser as a heater, and was made out with the method that the laser and surface irradiated are upright.The parameters combinations were optimized and the best combinations were confirmed.The various microstructures of samples got by laser irradiation and their formation mechanisms were studied with scanning electron microscopy and X-ray diffraction by compared with CO₂ laser irradiation test.4. The SiC whiskers' growth mechanisms were studied in detail according to 4 stages of whisker's growth(the formation of whiskers' crystal nucleus, the primary stage of whiskers' growth, the secondary thickening stage of whiskers' growth, the stopping stage of whiskers' growth).5. The effect of laser parameters from CO₂ laser or Nd:YAG laser and three binders which were PVA,PVB,CMC on the growth of SiC whiskers were deeply analyzed.