The dynamics and the spectral kinetic characteristics of the plume emerging in the vicinity of graphite targets, pressed
pellets consisting of zirconium oxide powder stabilized with yttrium (YSZ) and of garnet stock with neodymium
(YAG:Nd) are studied. The targets are irradiated in air at room temperature using a repetitively pulsed CO2 laser with a
wavelength of 10.6mm, a peak power of up to 9 kW, a pulse energy of up to 1.69 J, and a pulse duration of 330ms at a
level of 0.1. The plume propagates normally to the target surface at an angle of 45° relative to the laser radiation. The
spectral kinetic characteristics of the plume luminescence are discretely measured along the entire length. It is
demonstrated that the plumes of all targets represent the "ows of a weakly nonequilibrium gas plasma with a temperature
of 10 kK (graphite) and 3.1...4.7 kK (YSZ and YAG:Nd pressed pellets). The plume size is determined by the peak
power of the laser pulse. The luminescence of the two-atom radicals (C2 in graphite; ZrO and YO in YSZ; and YO, AlO,
and NdO in YAO:Nd) dominates in all of the plumes. A relatively high temperature of the graphite plume is maintained
owing to the energy of the exothermic reaction involving the association of carbon atoms and the energy of the
vibrationally excited molecules resulting from this reaction. The dynamics of plasma plume was studied by luminescence
imaging and shadowgraphy.
This report deals with the production and characteristics of Y2O3 -stabilized ZrO2 (YSZ), A12O3+YSZ, GDC, Nd:Y2O3 and Nd:YAG nanopowders prepared by evaporation of the materials with the help of a pulse-repetitive CO2 laser. The design of a setup for the nanopowders production, scheme and characteristics of the original CO2 laser excited by a pulse-periodic combined discharge are reported. For YSZ; Al2O3+YSZ, Nd:Y2O3, Nd:YAG the output rate was 15-25 g/h, for GDC ~ 50-75 g/hour, the energy consumption 30-40 (W*h)/g and 8-15 (W*h)/g, respectively. Data for the nanopowders specific surface, size distribution, the results of X-ray phase and structure analysis, as well as the results of luminescence analysis are discussed. The analysis of the obtained results showed that two main factors that determine the output rate of the nanopowders synthesis are the type of material evaporated and the mean laser radiation power. The mean size of the nanoparticles doesn't depend on the type of material.
The design and characteristics of a setup for producing oxide nanopowders are reported. Y2O3-stabilized Zr02 (YSZ), Al2O3+YSZ and CeGdO nanopowders are prepared by target evaporation with a pulse-periodic C02-laser. Average laser radiation power is 600 W, pulse power ~10 kW. The output rates of YSZ and Al2O3+YSZ nanopowders are 15-20g/h, and CeGdO nanopowder-55-6Og/h. The grain mean size in the powders is l5nm. Data for the powder characteristics, as well as results of X-ray phase and structure analysis, are reported. The results of investigation of unstable behavior of plasma plume produced by the long-pulse laser irradiation of the targets are reported as well. The mushroom-like shape of the glowing area is believed to be determined by the Richtmyer-Meshkov instability of the plasma-air interface and formation of nanoparticles in the plasma expanding into the buffer gas.
The paper reports about a new pulse-repetitive high-efficient technological CO2-laser and its applications. An original method of active medium excitation was used for laser pumping. Efficiency of the laser constructed on the basis of this method reached 12%, average radiation power 600 W, pulse power ~ 10 kW. The laser was used for YSZ powders production by successive evaporation and crystallization in the gas stream. The output rate was 15-20g/h, specific surface of the powder was up to 70m2/g. Evaporation of materials by CO2 laser was also used for ZrO2 and Al2O3 thin films deposition on stainless steel plates. The average thickness of the film was ~500nm, the deposition rate was ~10nm on the area ~1cm2 per pulse. The deposited films have high adhesion properties.
Our paper reports about YSZ powders by successive evaporation and crystallization in the gas stream. In the laser applied the original method of active medium excitation was used. Efficiency of the laser constructed on the basis of this method reached 22 percent and specific power output at approximately 1 W/cm3. Pulsed regime is proved to be more efficient for active medium excitation and target evaporation than continuous one. Targets made from coarse YSZ powder with Y2O3 content of 10.15 mol. percent were evaporated and crystallized in a stream of cleaned air. Cubic-structure YSZ particles were obtained which had a shape close to spherical. Particle size distribution was close to a lognormal distribution with dg equals 10 nm and (sigma) equals 1.75. Specific surface of the powder was up to 70 m2/g, while the Y2O3 content reduced to 9.8 mol. percent.
The development of high-efficient and scaleable CO2- lasers is important both for technology and for large-scale laser systems engineering. Our paper reports about original method of active medium excitation with no limits for its volume. Efficiency of the laser constructed on the basis of this method reached 22% and specific power output -1 W/cm3. Pulse regime is proved to be more efficient for active medium excitation then continuous one. Pulsed radiation is also more suitable for material processing.
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