Helicity
of a carbon nanotube is determined by the pentagon distribution
in the nucleus-cap. In catalytic growth, the shape of the metal catalyst
could possibly affect the pentagon arrangementintuitively,
by matching the disclinations-pentagons to the vertices of underlying
solid metal. Here we explore this effect by atomistic simulations
of all possible nanotube caps of diameter d ≃
0.8 nm on a Ni icosahedron. Although the vertices of the polyhedral
particle result in energy differences between various cap configurations,
the interface energy of the cap on the metal catalyst is still the
dominant thermodynamic factor during nucleation. Further, a dynamic
“edge-etching” algorithm reveals that the nucleation
barrier can occur before cap completion. Although control of the nucleation
barrier positions of different caps may be achieved through the chemical
potential of the carbon feedstock, the barrier heights are found to
be comparable for all caps, suggesting limited ability for chiral
selectivity.
The modification methods of waste rubber powder(WRP) which contain mechanochemical, microwave, ultrasonic, devulcanization in supercritical material and microbial devulcanization method through cutting off three-dimensional network are described. More emphasis is put on devulcanization mechanism and the defects of each method as the devulcanization process is often accompanied with the main rubber chains degradation are also discussed. When modified WRP is added into rubber matrix, the mechanical properties of composite and compatibility between virgin rubber and WRP are improved. So the mode of core modification on WRP is built, through the broken three-dimensional network modification methods of WRP.
The effects of the ratios of natural rubber latex (NRL)and chloroprene rubber latex(CRL) and the type of compatibilizer on physical and mechanical properties of latex film were researched.The oil resistance of vulcanized latex film was tested. The compatibility of the latex blends was also analyzed by TG/DTG method.The results showed that properties of latex film were best when ratio of NRL/CRL was 75/25. As the CRL content increased, oil resistance of latex film was improved. Epoxidized natural rubber latex improved compatibility of NRL and CRL blends.
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