Glass spheres, surface area

In contrast to many other nanomaterials, silica nanoparticles do not acquire any peculiar property from their submicrometric size, except for the corresponding increase of the surface area. As a matter of fact, they can simply be regarded as extremely small and highly porous glass spheres. What makes silica nanoparticles very interesting from the supramolecular point of view is the presence of a well-defined structure with compartments (bulk, surface, pores, shells, etc.) that can be rather... 

Pellicular or controlled surface porosity particles were introduced in the late 1960s these have a solid inert impervious spherical core with a thin outer layer of interactive stationary phase, 1-2 pm thick [13]. Originally, the inner sphere was a glass bead, 35-50 pm i.d., with a thin active polymer film or a layer of sintered modified silica particles on its surface. Such particles were not very stable, had very low sample load capacities because of low surface areas and are not used any more. Nowadays, this type of material is available as micropellicular silica or polymer-based particles of size 1.5 to 2.5 pm [14]. Micropellicular particles are usually packed in short columns and because of fast mass-transfer kinetics have outstanding efficiency for the separation of macromolecules. Because the solutes are eluted as very sharp narrow peaks, such columns require a chromatograph designed to minimise the extra-column contributions to band broadening. 

A composite material made of zinc oxide and polyvinyl alcohol was prepared by a sonochemical method [135]. Annealing of the composite under air removed the polymer, leaving porous spheres of ZnO. This change was accompanied by a change in the surface area from 2 to 34 m g k The porous ZnO particles were used as the electrode material for dye-sensitized solar cells (DSSCs). They were tested by forming a film of the doped porous ZnO on a conductive glass support. The performance of the solar cell is reported. 

Round-bottomed flasks were considered as simple spheres. The radius was calculated from the formula v = 4/3 irr3, and the surface area was calculated by the formula A = 4 irr2. No compensation was made for the thickness of the glass vessels. 

AT = Tg - T or T -Tg, where T and T are the beginning and the end of the glass transition regions, respectively, defined in Fig. 2.117. The value of AT increases sharply with the surface area of the microphase. For the transition of the phases surrounded by a surface that connects to a phase of lower glass transition, the glass transition starts at lower temperature (spheres of polystyrene in air and MS surrounded... 

The data in Figure (3.10-1) was the average of isotherms of 15 nonporous materials (such as zinc oxide, tungsten powder, glass sphere, precipitated silver), obtained by dividing the volume of nitrogen adsorbed by the BET surface area. This average thickness of the adsorbed layer is a function of P/Pq ... 

The agarose drop shown in Fig. 8 had been resting on glass spheres with a diameter of 30 jm. For surfaces with features of this scale it is easy to determine the wetting mode and is possible to estimate the area of contact, which provides qualitative information on the shape and curvature of the former liquid-gas interface. In the case of the drops resting on the printing plate surface (Fig. 7), where the features are in the scale of 100 jm quantitative analyses of the height maps are possible. 

Small amounts of inorganic fillers such as fumed silica, high surface area alumina, bentonites, glass spheres and ceramics are mixed with polyols such as propylene glycol to increase viscosity for printed electrodes. Proposed printed electrodes are carbon black, graphite, metallic or plated metaUic particles. 

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