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2 µm - eTheses Repository - University of Birmingham

2 µm - eTheses Repository - University of Birmingham

Compared to the

Compared to the incremental diagram, the cumulative expresses better the intrusion-extrusion behaviour. The intrusion-extrusion experiments are indicated by the pointers in Figure 4.25 b). The residual intruded porosity is referred to as the residual porosity after extrusion Φext.. In the AO preforms without a pore former, the Φext was 39% whereas about 25% still remained in the preform when a pore former was used (AOPC20). The incremental size distribution of AO showed a single distinct peak between pore diameters of 0.25 µm and 1.1 µm. In contrast, the pore size distribution of AOPC20 was broader, starting at 8 µm and going down to a minimum pore size of 0.25 µm. The maximum incremental value of 14.5% was at a pore diameter of 7.5µm. Relative pore pore volume volume () 0.9 0.8 0.2 0.1 0.0 10 -1 10 0 Pore diameter (µm) Pore diameter /µm Figure 4.26 Pore size distribution of the preforms without pore former additions: AO, TO and MO. The pore size distributions of the particulate preforms of different chemical compositions without pore forming additions (AO, TO and MO) are shown in Figure 4.26. As already shown in Figure 4.25 a), AO exhibited a distinct peak at a pore diameter of 0.8 µm. The MO preform had a distinctive peak with the highest relative incremental intrusion of 0.81 at a larger pore diameter of 1.8 µm. In contrast, TO exhibited a broader distribution: the first 119 AO TO MO 10 1

intrusions started at 4 µm and ended at 0.2 µm. One distinct peak at 0.2 µm was obvious and a second was indicated at 1.5 µm therefore indicating a bimodal pore size distribution. The pore size distribution curves of the preforms of different chemical composition fabricated with PC as pore forming additive are presented in Figure 4.27. The broad pore size distribution of AOPC20 in the range of 10 µm to 0.25 µm was also found with the AGPC15 and TOPC20 preforms. The distribution curve of AGPC15 started at lower diameters and exhibited a significantly increased fraction of small pores. The distribution of TOPC20 was similar to that of AOPC20. In contrast, MOPC20 showed a bimodal pore size distribution with a peak at a pore diameter of about 7 µm, attributed to the pore forming additive, and one peak at 0.9 µm representing the intergranular pores. Relative Relative pore pore volume volume () 0.3 0.2 0.1 0.0 10 -1 AOPC20 AGPC15 TOPC20 MOPC20 10 0 Pore diameter (µm) Pore diameter /µm Figure 4.27 Pore size distributions of AOPC20, AGPC15, TOPC20 and MOPC20. Figure 4.28 shows the pore size distributions of TOPC10 and TOPC20. In TOPC10 the coarsest pores were about 2.5 µm in diameter and the main concentration of pores had a diameter of 0.3 µm. In contrast, the higher PFA fraction in TOPC20 resulted in a larger 120 10 1

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