Particle assembly with localized bonding

The mean tensile strength of an agglomerate can be estimated from a model [1] based on Fig. 2.1 and the following assumptions  

Statistical-geometrical considerations yield [1] the following equation  

Equation (1) indicates the influence of the major parameters which determine the tensile strength of an agglomerate with bonding localized at the points of contact. It requires knowledge of the tensile strength of a single 

Particle diameter, d, is known from size analysis. 

The coordination number, fe, presents a greater problem. Although k is strictly a function not only of the void fraction but also of the packing arrangement [2], experimentally determined coordination numbers may be correlated directly with porosity as an approximation. Thus, Rumpf [1] used the expression 

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Recently, STS and STM have been applied to study the onset of the catalytic activity of Au particles grown on titania [238], which appeared to be correlated with the layer thickness of the particles on the surface and, as shown above, the bonding of CO with small gold clusters could be characterized in STM/STS experiments (Fig. 1.39 see Morphological Properties of Supported Clusters ) [190]. The above presentation of the spectroscopic results on deposited, size-selected clusters clearly shows that valuable information on these nanosystems can only be obtained by the application of an arsenal of local and nonlocal surface science analysis methods. Therefore, in the near future a much more intense employment of scanning probe techniques such as STM, STS, AFM, and others will beyond any doubt improve considerably assembly, characterization, and functionalization of size-selected clusters on solid surfaces. 

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