Effects of polymerizable groups on aqueous phase behavior of monomeric and gemini surfactants have been studied on the basis of visual appearance, polarized optical microscopy (POM), and small angle X-ray scattering (SAXS) data. Three phases were observed for nonpolymerizable monomeric (UTAB), polymerizable monomeric (PC11), and non-polymerizable gemini (11-6-11) surfactants: micellar solution (Wm), hexagonal (H1), and lamellar gel (Lβ) phases. In the case of a polymerizable gemini surfactant (PC11-6-11), we saw a lamellar liquid crystal (Lα) phase between the H1 and Lβ phases (i.e., Wm-H1-Lα-Lβ phase transition). Polymerizable groups covalently bound to the terminal hydrocarbon chains resulted in an increased Wm-H1 phase transition concentration for both the monomeric and gemini surfactants. It seems that this is due to the loosely packed hydrocarbon chains of the polymerizable surfactants in their molecular aggregates. We also found that the gemini surfactants yield a lower Wm-H1 phase transition concentration (in mol/L) than the monomeric ones, as a result of an increased critical packing parameter and/or an increased hydrophobicity of the gemini surfactants.
Aluminum matrix composites (70vol%SiC/Al, 55vol%SiC/Al, 60vol%Al 2 O 3 /Al, 70vol%AlN/Al, and 30vol%SiC/Al) were prepared by the infiltration and the casting methods. The internal friction and the microplasticity of these composites were measured with a Föppel-Pertz torsion pendulum apparatus over the temperature range of 303 to 853 K and the strain range of 3×10-5 to 3×10-3. The internal friction of these composites increases with increasing temperature and increases rapidly over 600 to 800 K, while their shear modulus gradually decrease and rapidly decrease over 600 to 800 K. The internal friction of the composites at elevated temperatures is caused by relaxations due to the interfacial diffusion between a reinforcement phase and Al and due to the plastic flow at grain boundaries. The activation energy of the interfacial diffusion is 40.7-56.7 kJ/mol for SiC/Al, 62.1 kJ/mol for Al 2 O 3 /Al, and 27.7 kJ/mol for AlN/Al, respectively. The activation energy of the plastic flow is 42.3-119 kJ/mol. The internal friction of the infiltration composites remarkably depends on strain amplitude rather than that of the casting composites. The Granato-Lücke plots of the composites show a linear relationship, indicating that the increase in internal friction with increasing shear strain is caused by the vibration energy loss due to the dislocation damping mechanism. The dislocation mobility of the infiltration composites is larger than that of the casting composites. The specific damping capacity and Young's modulus of 70vol%SiC are higher than those of 70vol%AlN.
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