Physicists from Yekaterinburg received nanopowder

In the work, which will be published in the collection Letters to the Journal of Technical Physics in January, but is already available on the website of the publication, scientists describe the advantages of a laser for obtaining nanopowders of complex composition with a given stoichiometry.

The method of laser vaporization of a substance, also called laser ablation or laser spark, is based on the removal of a substance from a surface by laser irradiation. The method is divided into several stages: the evaporation of the material from the target, the development of a plasma torch from the particles of the irradiated substance, the deposition and growth of the crystalline material on the substrate. This process can be used for chemical analysis of substances, as well as in surface treatment technologies and for the creation of various nanostructures.

It is promising to create nanopowders with a given stoichiometry using a laser spark, that is, with a given ratio of the masses of chemical elements that make up the powder. The main problem of this technology is associated with excessive evaporation of the substance; therefore, it becomes necessary to select laser radiation with optimal characteristics. A laser for the production of nanopowder must have a high power and at the same time a short radiation pulse. Employees of the Institute of Electrophysics of the Ural Branch of the Russian Academy of Sciences proposed using a carbon dioxide laser for these purposes, the active medium of which is a gas mixture with a high CO2 content. Physicists Vladimir Osipov, Vasily Lisenkov and Vyacheslav Platonov developed a theoretical model of the processes of interaction of laser radiation with matter, which was then confirmed experimentally. To obtain a nanopowder, they used a laser complex consisting of a repetitively pulsed CO2 laser, an evaporation chamber, and a system for separating and capturing the nanopowder. The laser emitted pulses with a peak power of up to 10 kilowatts and a repetition rate of 500 Hertz. Powders of yttrium and aluminum oxides with particle sizes from one to ten microns served as the target for the pulses. As a result of ablation, the researchers obtained an amorphous powder of yttrium-aluminum oxide (also called yttrium-aluminum garnet, since a synthetic gemstone is made from this substance at the macro level). The size of these particles was 10 nanometers. The nanopowder production rate depends on the radiation energy. The use of a CO2 laser made it possible to obtain 24 grams of powder per hour.

To demonstrate the practical significance of the resulting nanopowder, the researchers created several samples of transparent optical ceramics from it. Such ceramics transmit 77 percent of the infrared radiation, which makes them promising for use in electronics for creating infrared windows (areas that are transparent to infrared radiation).