Podcast
Questions and Answers
What factors can cause elastic or permanent structural changes in highly porous materials?
Applied pressure
What concept helps explain hysteresis effects and the trapping of mercury inside a sample after depressurization?
Connected pore network and snap-off factor
What is the importance of ordered packed-sphere structures in studying porosity?
Well-defined pore sizes and connections between pores
What is the range of pore sizes covered by mercury porosimetry?
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What type of studies are needed to fully understand the effects of individual factors in model pore structures?
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Why is mercury porosimetry considered an extremely useful analysis technique?
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Study Notes
Contact Angle Effects
- The concept of contact angle hysteresis is referred to in the publications by Lowell et al and Salmas et al.
- The ink-bottle theory explains why mercury remains trapped inside the sample after depressurization, but it does not explain the pore size shift between intrusion and extrusion.
Mercury Porosimetry
- Mercury porosimetry is a useful analysis technique that provides important information about the porosity of samples, covering pore sizes from 0.4 mm to less than 4 nm.
- The technique is based on the principle that mercury will enter the pore cavity at a pressure determined by the entrance size, not the actual cavity size.
Pore Structure and Mercury Trapping
- Pores rarely have a uniform shape, with the "throat" or entrance opening being smaller than the actual cavity.
- Mercury will enter the pore cavity at a pressure determined by the entrance size, and during extrusion, the mercury network breaks at the narrower connections between pores, leaving mercury trapped inside.
- The ratio of inner pore size to throat size affects the amount of mercury remaining in the structure.
Model Structures and Pore Size
- Model structures, such as ordered packed-sphere structures, allow for comparison of measured and predicted pore sizes, providing insight into the intrusion and extrusion process.
- The sample in Figure 8 demonstrates the ink-bottle theory, with more mercury remaining in the structure as the ratio of inner pore size to throat size increases.
Limitations and Future Research Directions
- Contact angle hysteresis cannot explain why mercury remains trapped in the pore system after complete depressurization or other observed phenomena.
- Further research on model pore structures, theoretical calculations, and experimental data is needed to fully understand hysteresis effects and trapping of mercury.
- Additional studies on etched channels in glass will enhance understanding of "network effects".
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Description
Explore the concept of contact angle effects in materials science through theoretical and experimental observations. Learn about contact angle hysteresis, ink bottle theory, and intrusion experiments with mercury on silica samples.
