Contact Angle Effects in Materials Science

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".