Laser-synthesized silicon- and ferro-based nano powders

摘要

Abstract: Nano-powders of Si$-3$/N$-4$/, Si/N/C, SiC, $alpha@-Fe and $gamma@-Fe, 5 - 80 nm in mean diameter were synthesized via laser induced gas phase reactions. Amorphous Si$-3$/N$-4$/ powders (96 wt%) were obtained at 1000$DGR@C flow Hexamethyldisilazane $PLU MH$-3$/, $beta@-SiC (93 wt%) was formed at 1600$DGR@C with H$-2$/. Amorphous Si/N/C powders with N/C ratios (0.1 - 6) were synthesized at various temperatures. The main impurities in the powders were the organo-ligands such as NH$-x$/ and CH$-x$/ (x $EQ 1 - 3). Pure $gamma@-Fe nano-particle were prepared from cw CO$-2$/ laser induced pyrolysis of iron pentacabonyl $gamma@-Fe phase is stable at high temperature. In our method, rapid heating and cooling rate resulted from laser-induced pyrolytic reaction prevent the $gamma@-Fe from transforming to $alpha@-Fe on cooling. Eventually, at room temperature $gamma@-Fe nano particles were prepared with high yield. The $alpha@-Fe and $gamma@-Fe powders were characterized by transmission electron microscope, X-ray diffractometer.!8