Porosity Analysis

Due to the inefficient packing of the rigid struts, CMPs have an open structure even after removal of all solvents. This open structure leads to high surface areas and pore volumes. Surface areas of CMPs are most often reported as Brunauer-Emmett-Teller (BET) surface areas, which takes into account the adsorption of multiple adsorbate layers. 

---

Dash RK, Yushin G, Gogotsi Y et al (2005) Synthesis, structure and porosity analysis of microporous and mesoporous carbon derived from zirconium carbide. Micropor Mesopor Mater 86(l-3) 50-57... 

As to the theoretical treatments, methods derived from the potential theory have been used These methods are the easiest way to perform porosity analysis from experimental data related to different adsorbates... 

Bai, M., and J-C. Roegiers. 1997. Triple-porosity analysis of solute transport. J. Contam. Hydrol. 28 247-266. 

Tovey, N.K., Kathleen A.D., 2002. Quantitative orientation and micro-porosity analysis of recent marine sediment microfabric. Quaternary Int. 92, 89-100. 

Special features The HTPl-V is most commonly used when the requirement is for both ideal and non-ideal gases and is therefore complanentary with the Hiden IGA-001. A typical application is the measurement of isothermal uptake of hydrogen in storage media combined with in situ surface area and porosity analysis... 

Out of other physical methods used for porosity analysis, mercury intrusion porosimetry is worth mentioning. This method can be tried at all levels of electrode development, i.e. from catalyst to matrix stage. Testing of a matrix is done at low pressures (upto 400 kPa) so that the soft structure of the matrix is not deformed. Fig. 11 shows a typical result of PAFC cathode developed by the author s laboratory. The matrix is also characterized by other simple tests, like water loading, rate of water migration when dry matrix is dipped in one end etc. (Caires et al., 1997). 

A typical micro-structural cross section of the CMC material is shown in Figure 1. As can be seen, there are large and medium size pores present in the matrix of the material as well as smaller pores within the fiber tows. A porosity analysis was done on material from several tab regions from various samples and the percent porosity from this effort is found in Table IV. This table shows that there is not a clear trend in lower porosity with increasing number of PIP cycles. 

Table IV. Micro-structural Porosity Analysis (from Cross Sections)...

A series of panels were made with differing number of PIP cycles with the expectation that this would result in different overall porosity levels. The optical and x-ray porosity analysis did not confirm this trend and some of the properties did not follow the expected trend with increasing number of infiltration cycles. It was found fiom fast fracture studies that the overall diffusivity is controlled by the microstructure and therefore the porosity correlates with tensile properties. No clear correlation between porosity and properties was observed from the durability testing done. Durability appears to be controlled by the location and distribution of the porosity. Additional testing and analysis is needed to shed insight on the material performance. 

---