I. de Francisco

Process-generated nanoparticles from ceramic tile sintering: Emissions, exposure and environmental release

The ceramic industry is an industrial sector in need of significant process changes, which may benefit from innovative technologies such as laser sintering of ceramic tiles. Such innovations result in a considerable research gap within exposure assessment studies for process-generated ultrafine and nanoparticles. This study addresses this issue aiming to characterise particle formation, release mechanisms and their impact on personal exposure during a tile sintering activity in an industrial-scale pilot plant, as a follow-up of a previous study in a laboratory-scale plant. In addition, possible particle transformations in the exhaust system, the potential for particle release to the outdoor environment, and the effectiveness of the filtration system were also assessed. For this purpose, a tiered measurement strategy was conducted. The main findings evidence that nanoparticle emission patterns were strongly linked to temperature and tile chemical composition, and mainly independent of the laser treatment. Also, new particle formation (from gaseous precursors) events were detected, with nanoparticles <30nm in diameter being formed during the thermal treatment. In addition, ultrafine and nano-sized airborne particles were generated and emitted into workplace air during sintering process on a statistically significant level. These results evidence the risk of occupational exposure to ultrafine and nanoparticles during tile sintering activity since workers would be exposed to concentrations above the nano reference value (NRV; 4×10(4)cm(-3)), with 8-hour time weighted average concentrations in the range of 1.4×10(5)cm(-3) and 5.3×10(5)cm(-3). A potential risk for nanoparticle and ultrafine particle release to the environment was also identified, despite the fact that the efficiency of the filtration system was successfully tested and evidenced a >87% efficiency in particle number concentrations removal.

In-situ laser synthesis of Nd–Al–O coatings: the role of sublattice cations in eutectic formation

Neodymium aluminate coatings have been prepared in-situ by the laser zone melting (LZM) method, using a CO2 SLAB-type laser emitting at 10.6 µm. Polycrystalline Al2O3 commercial plates have been used as substrates, and coatings were prepared from the corresponding mixtures of powdered neodymium and aluminium oxides as starting materials. Microstructure, studied by SEM and phase composition, studied by XRD, proved the in-situ formation of a NdAlO3/NdAl11O18 eutectic. As a result, a well integrated composite coating was formed. Nanoindentation tests are consistent with excellent integration between coating and substrate. Structural similarities between the eutectic components within the coating, as well as between these and the substrate, are consistent with the crystallographic concepts proposed by Vegas (Ramos-Gallardo & Vegas, 1997), where cation sub-arrays play an important role governing metal oxide structures. These structure sublattices are suggested as the driving force behind eutectic oxide formation.

Workplace Exposure to Process-Generated Ultrafine and Nanoparticles in Ceramic Processes Using Laser Technology

The ceramic industry is an industrial sector, which has been growing and including innovative technologies such as laser processes. However, there is a considerable research gap within exposure assessment studies for process-generated ultrafine and nanoparticles, especially as a result of such innovations in the manufacturing processes.

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 laser 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.