TY - BOOK

T1 - Wetting and Interfacial Reaction Investigations of Iron-Based Alloys/Alumina Systems by Means of the Sessile Drop Shape Analysis Method

AU - Karasangabo, Augustin

N1 - no embargo

PY - 2009

Y1 - 2009

N2 - The wetting phenomenon plays a paramount role in many high technology applications ranging from microelectronics to steelmaking that involve the spreading of liquids on solid surfaces. The behaviour of a liquid partially wetting a smooth and inert solid surface is rather well understood. However, the case of rough solid surfaces is much less clear, even though roughness is a real-world problem and its value in technical applications is very high. Some theoretical studies suggest that the surface roughness of a non-planar substrate may enhance wetting, but a comprehensive study conducted using "real" substrates and Fe-based alloys at steelmaking temperatures is still lacking. In the present PhD work, the drop shape analysis approach has been used to determine the change of the wetting angle in the temperature range 1550 - 1620°C in purified Ar atmosphere for various Fe-based alloys on dense polycrystalline as-sintered and as-ground alumina substrates. A non-wetting behaviour was observed for Fe alloys containing very low concentrations of Ti, Al, or P on both substrate qualities regardless of ceramic surface topography or temperature changes. In contrast, for Fe alloys with high Ti, Al, or P contents a remarkable enhancement of wetting was registered with increasing solute concentration, temperature, and isothermal holding time. In the case of a simultaneous presence of Ti and P in the Fe alloy the contact angle continuously decreased with increasing contents of Ti and P for both alumina substrate qualities, whereas the surface roughness of the substrates had a negligible effect on the wettability, which was rather improved by the presence on the substrate surface of local defects. Finally, contact angles produced by Fe alloys with high contents of Ti and Al on as-ground alumina were consistently higher than those produced on the as-sintered substrates, and no significant improvement of the wettability was registered neither with increasing solute content nor holding time. This is attributable to two effects, viz.: the formation of a non-wettable hercynite layer at the interface for the Fe-Ti-P and Fe-Ti-Al alloys, and the presence of extensive cracks in the original substrate at the surface of the as-ground substrates. Both effects have adverse implications on wettability as they bring about an obstruction of the spreading process eventually terminating it, with the net result of a poor wetting.

AB - The wetting phenomenon plays a paramount role in many high technology applications ranging from microelectronics to steelmaking that involve the spreading of liquids on solid surfaces. The behaviour of a liquid partially wetting a smooth and inert solid surface is rather well understood. However, the case of rough solid surfaces is much less clear, even though roughness is a real-world problem and its value in technical applications is very high. Some theoretical studies suggest that the surface roughness of a non-planar substrate may enhance wetting, but a comprehensive study conducted using "real" substrates and Fe-based alloys at steelmaking temperatures is still lacking. In the present PhD work, the drop shape analysis approach has been used to determine the change of the wetting angle in the temperature range 1550 - 1620°C in purified Ar atmosphere for various Fe-based alloys on dense polycrystalline as-sintered and as-ground alumina substrates. A non-wetting behaviour was observed for Fe alloys containing very low concentrations of Ti, Al, or P on both substrate qualities regardless of ceramic surface topography or temperature changes. In contrast, for Fe alloys with high Ti, Al, or P contents a remarkable enhancement of wetting was registered with increasing solute concentration, temperature, and isothermal holding time. In the case of a simultaneous presence of Ti and P in the Fe alloy the contact angle continuously decreased with increasing contents of Ti and P for both alumina substrate qualities, whereas the surface roughness of the substrates had a negligible effect on the wettability, which was rather improved by the presence on the substrate surface of local defects. Finally, contact angles produced by Fe alloys with high contents of Ti and Al on as-ground alumina were consistently higher than those produced on the as-sintered substrates, and no significant improvement of the wettability was registered neither with increasing solute content nor holding time. This is attributable to two effects, viz.: the formation of a non-wettable hercynite layer at the interface for the Fe-Ti-P and Fe-Ti-Al alloys, and the presence of extensive cracks in the original substrate at the surface of the as-ground substrates. Both effects have adverse implications on wettability as they bring about an obstruction of the spreading process eventually terminating it, with the net result of a poor wetting.

KW - Benetzbarkeit

KW - Benetzung

KW - Benetzungswinkel

KW - Clogging

KW - Grenzflächenreaktion

KW - Kontaktwinkel

KW - Korrosion

KW - Oberflächenspannung

KW - Reaktive Benetzung

KW - Sessile Drop

KW - Tropfenkonturanalyse

KW - Wettability

KW - wetting

KW - reactive wetting

KW - contact angle

KW - interfacial properties

KW - drop shape analysis

KW - sessile drop method

KW - corrosion

KW - clogging

M3 - Doctoral Thesis

ER -