Views
5 years ago

2 µm - eTheses Repository - University of Birmingham

2 µm - eTheses Repository - University of Birmingham

account the error in

account the error in contact angle measurements, the wetting angles in all three systems were similar with no significant variations within the holding time. The reliability of the measurement of the wetting angle θst during the holding time was demonstrated when the wetting angle measured on the liquid droplet in situ was compared with that measured on a section cut through the centre of the solidified droplet. This measurement, as shown in Figure 4.7, was performed using the spline method similar to that used for the in-process measurements. The wetting angle of IM on MO was 154° in both cases, indicating good agreement between the two methods. IM_droplet Substrate MO 97 2 200 2 200 µm µm Figure 4.7 Contact angle of IM on MO determined using a micrograph at the triple point on a cross-section through the centre of the solidified droplet. 4.2.3 Influence of substrate on interface formation Apart from the contact angle measurements, the microstructure of the contact area between the substrate and the metal alloy was investigated in order to detect interfacial reaction phases and irregularities. The ceramic substrates could not be made totally dense and contained residual closed porosity which was opened to the surface during the substrate polishing process. In metal-ceramic substrate couples, the bottle-neck shaped microporosity on the substrate surface was filled

with the metal alloy IM: examples are given in Figure 4.8 a) to c). The cavity inlet diameter was measured to be below 1.3 µm in titania (TF) and alumina (AF) substrates. Examination of the magnesia substrates showed that the main pore inlets had a diameter of about 3 µm. These pores and the smaller pore branches leading off them had inlet diameters in the sub-micron range and were generally filled with the metal phase, as shown in Figure 4.8 c). (a) (b) (c) C I M C 98 M 1.3 µm Figure 4.8 Optical micrographs of the interface after sessile drop test a) IM-AF; b) IM- TF and c) IM-MO. Light phase: metal (M), dark phase on the bottom: ceramic substrate (C) and an interfacial phase in IM-AF (I). Infiltration of the porous structure was further investigated by replacing the low porosity MO substrate with the porous preform MOPC20. After 1800 s, the metal could be easily removed from the substrate, indicating no significant infiltration of the open porosity. This was further confirmed as the surface of the substrate was flat, even after removal of the metal. The metal had similar microstructures when comparing IM-TF with IM-AF. The finely dispersed grey magnesium-rich phase in the metal alloy (M) in Figure 4.8 a) could not be detected clearly at the IM-MO interface. This was attributed to the over exposure necessary to visualize the ceramic phase. Without over exposure, the distribution of the alloying element in the metal region M of MO-IM was similar to that of AF-IM and TF-IM. In the case of TF and AF, a coarse plate-shaped phase developed at the metal-substrate interface. This phase and the interfacial delamination behaviour were investigated by I C M

PDF File 2 - University of Alabama at Birmingham
no· l'2-'1t1 - Repository - Texas A&M University
eTheses Repository - University of Birmingham
chapter 1 - eTheses Repository - University of Birmingham
eTheses Repository - University of Birmingham
eA - eTheses Repository - University of Birmingham
MODULE 2 - eTheses Repository - University of Birmingham
eTheses Repository - University of Birmingham
Caroline Winstanley - eTheses Repository - University of Birmingham
1 - eTheses Repository - University of Birmingham
pains of sin - eTheses Repository - University of Birmingham
Witch Shoes - eTheses Repository - University of Birmingham
epinician precepts - eTheses Repository - University of Birmingham
5% - eTheses Repository - University of Birmingham
Cymbeline - eTheses Repository - University of Birmingham
B - eTheses Repository - University of Birmingham
View - eTheses Repository - University of Birmingham
here - eTheses Repository - University of Birmingham
J - eTheses Repository - University of Birmingham
B - eTheses Repository - University of Birmingham
THE GOD–MAN - eTheses Repository - University of Birmingham
chapter 1 - eTheses Repository - University of Birmingham
Life on Wings - eTheses Repository - University of Birmingham
Engineering texts - eTheses Repository - University of Birmingham
ford madox brown - eTheses Repository - University of Birmingham
part i - eTheses Repository - University of Birmingham
soho depicted - eTheses Repository - University of Birmingham
PIERRE BOAISTUAU - eTheses Repository - University of Birmingham
Rewriting history - eTheses Repository - University of Birmingham
The Sins of the Sons - eTheses Repository - University of Birmingham