Ch. Kaps

IR-Laser Effects on Pigments and Paint Layers

Laser cleaning of polychrome surfaces is currently problematic due to the fact, that laser irradiation can cause discoloration of pigments in paint layers. A test program was worked out to analyse the chemical and physical background of typical “blackening effects” for different pigments. The analytical methods ESEM, XRD, DTA, FTIR and NMR were used to describe the reactions of historically relevant inorganic pigments and organic binding media caused by laser irradiation at 1064 nm. The discoloration of pigments and paint layers was documented by colour measurement. Further the determination of discoloration thresholds of energy density of pigments and paint layers was a main part of the research.

Influence of flue gas components on the chemical properties of the ceramic materials (Co-)Ce0,8Gd0,2−xPrxO2−δ

Materials in the system (Co-)Ce0.8Gd0.2−xPrxO2−δ are often used materials in the catalyst technology due to its oxygen storage capacity and are promising candidates for mixed conductive layer on membranes for oxygen separation in the Oxyfuel process. In both cases the material is exposed temperatures around 800°C and is in contact with aggressive gas species like CO2 and SO2, which may react with the ceramic material leading to a drop in their functional properties. In this work ceramic powder species with x = 0; 0.01; 0.03; 0.05; 0.1 and 0.2 were tested in two gas mixtures containing 99 vol.% CO2 and 1 vol.% SO2 on the one hand and 96.3 vol.% CO2, 3.6 vol.% O2 and 0.1 vol.% SO2 on the other hand. The ceramic powders were treated for 5 hours at 800°C. Before and after the treatment a phase analysis was done by XRD. X-ray amorphous sulphates and the belonging cations were quantified by a wet chemical route. Under CO2 gas the ceramic powders show a good chemical stability. The gassing with SO2 containing test gases causes a chemical expansion of the lattice in dependence of Pr content x due to a release of oxygen. Also small amounts of sulphate were found in the gassed samples. A small content of oxygen in the test gas (3.6 vol.-%) reduces the chemical expansion and the sulphate formation during the test significantly. An additional doping with 2 wt.-% Co inhibits the sulphate formation entirely.