Scanning electron microscopy fluid

In contrast to many other surface analytical techniques, like e. g. scanning electron microscopy, AFM does not require vacuum. Therefore, it can be operated under ambient conditions which enables direct observation of processes at solid-gas and solid-liquid interfaces. The latter can be accomplished by means of a liquid cell which is schematically shown in Fig. 5.6. The cell is formed by the sample at the bottom, a glass cover - holding the cantilever - at the top, and a silicone o-ring seal between. Studies with such a liquid cell can also be performed under potential control which opens up valuable opportunities for electrochemistry [5.11, 5.12]. Moreover, imaging under liquids opens up the possibility to protect sensitive surfaces by in-situ preparation and imaging under an inert fluid [5.13]. 

In 1994, we reported the dispersion polymerization of MM A in supercritical C02 [103]. This work represents the first successful dispersion polymerization of a lipophilic monomer in a supercritical fluid continuous phase. In these experiments, we took advantage of the amphiphilic nature of the homopolymer PFOA to effect the polymerization of MMA to high conversions (>90%) and high degrees of polymerization (> 3000) in supercritical C02. These polymerizations were conducted in C02 at 65 °C and 207 bar, and AIBN or a fluorinated derivative of AIBN were employed as the initiators. The results from the AIBN initiated polymerizations are shown in Table 3. The spherical polymer particles which resulted from these dispersion polymerizations were isolated by simply venting the C02 from the reaction mixture. Scanning electron microscopy showed that the product consisted of spheres in the pm size range with a narrow particle size distribution (see Fig. 7). In contrast, reactions which were performed in the absence of PFOA resulted in relatively low conversion and molar masses. Moreover, the polymer which resulted from these precipitation... 

R. J. Albalak, Z. Tadmor, and Y. Talmon, Scanning Electron Microscopy Studies of Polymer Devolatilization J. Non-Newtonian Fluid Mech., 33, 808-818 (1987). 

Scanning electron microscopy/energy dispersive X-ray (SEM/EDX) analyses have been used to probe the migration of vanadium in model fluid cracking catalysts (FCC). At the experimental conditions used, vanadium can migrate either from a Eu3+-exchanged Y (EuY) zeolite to an AAA-alumina gel or vice versa, depending on the type of vanadium precursor used. 

Most drugs and proteins are not soluble in commonly used supercritical fluids, and therefore are processed instead by the SC antisolvent technique,the most popularized being the SEDS, process which is illustrated in Fig. 9. SEDS-produced crystals can have extremely smooth surfaces, as shown by scanning electron microscopy and atomic force microscopy, and the surface may be more hydrophobic and less wettable than crystals grown under more polar conditions.A scanning electron micrograph of acetominophen crystals produced by the SEDS process is shown in Fig. 10. 

Equilibrium fluid cracking catalysts were obtained from several U.S. refineries. Scanning electron microscopy (SEM) studies were performed on these materials by mounting all equilibrium FCC s onto indium foil without coating the samples in an AMRAY model 1810 D SEM. 

Figure 17.17 Scanning electron microscopy of sharkskin surface on HOPE (Source Dawn Arda, Polymer Fluids Group, Department of Chemical Engineering, University of Cambridge with permission).

Bulk densities were measured by the Archimedes principle using distilled water as the working fluid. X-ray analysis was used to confirm that the glasses were totally amorphous. Scanning electron microscopy allowed confirmation of this and assessment of homogeneity. 

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