Felix Ott

Zusammenfassung

This study presents a simple and sustainable coating technology for the deposition of photocatalytic coatings based on titanium dioxide and geopolymers, which requires no thermal post-treatment. Titania powder P25, potassium silicate and a calcium aluminate-based hardener were dispersed in water and applied to aluminum substrates using a paintbrush, a roller and a spray gun. The coatings were air-dried for 12 h. The photocatalytic activities were tested via degradation of an aqueous methylene blue solution in a batch reactor under artificial UV-A light. The roller and the spray gun-based coatings yielded well-adhering coatings with high photocatalytic activity. Brushed coatings were inhomogeneous and unstable. The presented method of producing photocatalytic coatings is very simple to apply and does not require complex technologies or energy-intensive thermal treatments.

Zusammenfassung

In the field of metal matrix composites (MMC), spark plasma sintering (SPS) technique has been used so far for the manufacture of particle, whisker and short-fiber reinforced alloys. In this work, SPS technique is employed for the first time to produce continuous fiber reinforced light metals. For this purpose, metal matrix composite prepregs with aluminum as a surface coating on carbon fiber textiles are manufactured by twin arc wire spraying and subsequently consolidated by SPS in the semi-solid temperature range of the alloy. Shear thinning rheological behavior of the metal alloy at temperatures between solidus and liquidus enables the infiltration of fiber rovings under reduced forming loads. SPS offered a better controlled and more efficient heat transfer in the green body and faster consolidation cycles in comparison with alternative densification methods. Fully densified samples with no porosity proved the suitability of SPS for densification of MMC with a remarkable stiffness increase in comparison with samples densified by thixoforging, an alternative consolidation method. However, the pulse activated sintering process leads to a quite strong fiber/matrix adhesion with evidence of aluminum carbide formation.