Bond: aggregate-matrix mechanical

As-synthesized MWCNT and SWCNT exist as bundles or ropes and tend to agglomerate due to strong van der Waals forces (13) (Figure 7.1). Unless the CNTs are separated in to individual tubes and dispersed in the polymer matrix, the interactions of the nanotubes with the polymer will be weak. The mechanical failure of such composites will occur due to slippage of the tubes in the bundle that are not bonded to the matrix. In addition, the aggregates or bundles reduce the aspect ratio of the reinforcement which affects electrical properties as well (15). Because of these factors the first step will be to open up these bundles to separate individual tubes by using different techniques to increase the volume of interface between the CNT and the matrix (40). 

The role of additionally introduced metal (Mi) is many-sided. On the one hand M] (usually a non-transition metal) may serve as a trap for active centers, binding them more firmly with the support and preventing migration and aggregation. On the other hand these effects can be achieved as a result of the insertion of this metal ion between attached complexes (-M-M -M- type) promoting their matrix isolation. In addition, chemical interactions proceeding on the support (formation of weak M-Mi bonds, co-crystallization, formation of intermetallic compoimds and alloys, etc.) may promote an increase of catalyst productivity. Both types of active center should react with the substrate molecule, so that a complementary mechanism is realized and diffusional limitations are... 

---