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The CO 2 laser vaporization (LAVA) method was used to prepare titania nanopowders. Because this versatile method does not require special precursors, a coarse anatase raw powder was applied as starting material. Powder samples produced under varied process parameters were characterized by transmission electron microscopy (TEM), X-ray diffraction measurements, and Brunauer-Emmett-Teller surface area measurements. The laser-generated powders consist of spherical, single crystalline and pure anatase nanoparticles, merely softly agglomerated by weak van der Waals forces. Using TEM analysis, the influence of the process parameters on the resulting particle size distribution was investigated. The results are discussed with respect to the particle formation by gas phase condensation. The potential of a process integrated, i.e. in situ, coating procedure for the surface modification of the anatase nanoparticles is demonstrated. As an exemplary representative of organic layer materials stearic acid was chosen. The organic coating was characterized by TEM and Raman spectrometry. Because of the unavoidable soft agglomeration the coating covers entire agglomerates rather than individual primary particles. Thus, the influence of the LAVA process parameters on the agglomerate sizes was systematically studied using a scanning mobility particle sizer.

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In this article we report on the production of nanosized zirconia particles by CO2 laser evaporation. The radiation source was a transverse flow CO2 laser operating in the continuous or the pulsed mode. Pulses between 1 and 500 μs duration could be generated by two different Q-switching techniques. The evaporation rates as well as the diameter of the particles and their density distributions were investigated with regard to their dependence on the laser power, the pulse shape, and the properties of the carrier gas. By means of simple models the experimental results could be interpreted. Furthermore a kinetic rate equation has been derived for the formation and growth of small particles. Good agreement is found between the experiments and this theory.

For the efficient treatment of a broad variety of materials, pulsed CO2 laser radiation is well‐suited. But nevertheless, CO2 lasers are well established in industrial processes, a significant disadvantage of all previously basicavailable commercial systems, which are suitable for material processing, is their restricted pulsability. This is not caused by the amplification properties of the active medium, but by the wavelength of about 10 μm. In this region the spectrum of optical materials, which can be used for modulation, especially Q‐switching, is rather limited. In principle for acousto‐optic modulation only Ge and for electro‐optic modulation only CdTe are suitable materials. But both semiconductors are relatively power‐sensitive and therefore Q‐switching of conventional CO2 lasers is typically limited to less than 100 W of average power. This problem can be solved by the new resonator concept described below [1]. The aim is the optimum transformation of the potentially available power (cw up to the kW range) into average power of the pulsed radiation.

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