The laser furnace: A revolution in ceramics and glass processing?

Summary form only given. Photothermal laser processing of ceramics and glass usually results in the appearance of microcracks and in the consequent severe devaluation of their mechanical properties. The former is due to extreme thermo-mechanical stress.This work presents a novel processing tool, which combines laser irradiation with a continuous roller furnace, with the aim of processing ceramics and glass products without thermo-mechanical damage. The Laser Furnace apparatus will be described, along with some of the most representative results obtained to date on ceramic tile and flat window glass processing. Microstructure and properties of the resulting laser treated products will be reviewed in order to evaluate this novel methodology. A recently patented [1] Laser Zone Melting (LZM) method has thus been employed to prepare several types of oxide coatings on different pure oxide or mixed complex oxide commercial substrates. This novel meltsolidification processing method allows synthesizing high melting solids with a simultaneous input from an external, auxiliary heat source. This is done by performing the synthesis procedure within the hot zone of a continuous roller kiln, where the laser beam is scanned over the surface of the pre-coated substrate in motion. Figure 1 illustrates the Laser Furnace apparatus used for such a purpose. It is composed of a continuous roller kiln (A), a CO2 Laser system (B) and a beam scanning unit (C). The LZM method has been applied successfully to prepare refractory Zirconia-type eutectics [2], high temperature superconductor oxide coatings on MgO substrates [3] and alkaline-earth titanate coatings on alumina substrates [4]. A particular example of the procedure will be also presented. Powdered rare-earth oxides, as well as mixtures of the latter with Al2O3 were used as starting materials. In-situ synthesis of the corresponding coatings was performed by irradiating the precursor, deposited onto an Al2O3 substrate, with a CO2 lase- emitting at 10.6 μm. Microstructure (SEM) and phase composition (XRD) demonstrated in-situ formation of oxide eutectic systems within the coating. The interaction with the substrate resulted in stable, 200-500 μm thick, composite coatings, whose microstructure will be discussed in terms of Laser processing parameters and the nature of the oxide materials and substrate. Examples of commercial ceramic tiles and soda-lime glass products obtained by Laser Furnace processing will be also shown and discussed.