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Laser synthesis of ultrafine particles.

1989; Laser Society of Japan; Volume: 17; Issue: 5 Linguagem: Inglês

10.2184/lsj.17.5_358

1349-6603

Tetsuro Majima,

Laser Design and Applications

Recent studies concerning laser synthesis of ultrafine particles are reviewed with respect to the applications of lasers in industry. Mainly a cw and a TEA CO2 lasers are used because of their high power and their easy operation. The synthetic methods are classified into (1) gas-evaporation by laser heating and (2) laser-induced reaction in the gas phase: pyrolysis, infrared multiplephoton decomposition, dielectric breakdown, and infrared photosensitized decomposition. Of these two methods, the method (2) using a CO2 laser has advantages in synthesizing ultrafine particles with high purity, small diameters, and a narrow distribution of diameters.The present review is focused on the synthesis of ultrafine γ-iron particles. Since γ-iron is stable at 911-1392°C, γ-iron has not been usually isolated at room temperature. However, γ-iron has been synthesized in a high yield by the SF6-sensitized infrared photodecomposition of Fe (C0) 5 with a TEA CO2 laser. γ-Iron has an average diameter of 76Å, a narrow distributiuon of diameters, the face-centered-cubic structure, and paramagnetism even at 4.2K.