Silica spheres, characteristics

Although many (perhaps most) applications do not require the existence of a complete band gap, significant efforts to develop such structures have been undertaken. For a given symmetry, the characteristics of an induced band gap depend upon the refractive index contrast and filling factor of the two phases (e.g., silica spheres and air interstices). Inverse opals are negative replicates of the sterically packed structures that have been described above. In this case, one generally has... 

As indicated above the phase separation process can also be studied using optical microscopy as has been done by Verhaegh et al. [96]. They observed spinodal decomposition in a well-defined model colloid-polymer mixture of silica spheres in cyclohexane with dissolved polydimethyl siloxane chains of qr ss 1, and found similar results to those plotted in Fig. 4.16. Their findings agree with the picture sketched above and the characteristic length scale A follows the regimes of (4.41) and (4.42). 

For the nanoparticle surfaces, a similar mixed wetting state as described above is assumed [11, 17]. Only on silica sphere arrays decorated by gold nanoparticles we observe CA > 150°, reduced hysteresis and SA < 5°, which are characteristic for superhydrophobic substrates. Although a detailed characterization of the wetting mechanism on these hierarchical surfaces lies outside the scope of this work, we assume that the droplets on the substrates with hierarchical roughness are neither in the Wenzel nor Cassie-Baxter state. Most likely they reside in a mixed state as presented by... 

Chromatographic Silica. Silica particles used for liquid chromatographic supports are generally porous spheres in the diameter range 2-20 pm. Important properties of these particles bearing on chromatographic performance include mean size, size distribution, presence of aggregates and fines, and particle porosity. All these characteristics should be accessible to measurement by FFF most are described later. 

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