Scanning electron microscopy contrast

No two surfaces are absolutely identical and there will be some contact electrification. The electrostatic theory considers the two surfaces to be bonded as the two plates of an electrostatic condenser, and is due to Deryaguin [30]. According to this theory adhesion occurs due to the electrostatic forces formed by interaction between the substrates. This theory explains the pressure dependence of tack/autohesion very well but it does not explain why raw and compounded rubbers lose most tack/autohesion as they are cured and brought into molecular contact under pressure. Further this theory is also not successful in explaining the time and temperature dependence of the tack/autohesion. By using potential contrast scanning electron microscopy the existence of an electric double layer at the polymer interface has been demonstrated [31]. 

More recently, Possart has used potential contrast scanning electron microscopy to study electric double layer formation associated with the interface between a thin layer of solvent-cast low-density polyethylene and aluminum (Possart 1988). While arguing that the electrical discharge energy of the double layer makes a contribution to the fracture energy, this study... 

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... 

Atomic force microscopy (AFM) is a commonly employed imaging technique for the characterization of the topography of material surfaces. In contrast to other microscopy techniques (e.g., scanning electron microscopy), AFM provides additional quantitative surface depth information and therefore yields a 3D profile of the material surface. AFM is routinely applied for the nanoscale surface characterization of materials and has been previously applied to determine surface heterogeneity of alkylsilane thin films prepared on planar surfaces [74,75,138]. 

Fig. 4. CHO cells on a microcarrier a optical microscopy (contrast enhancement by Crystal Violet staining) and b scanning electron microscopy...

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