Controllable Preparation And Formation Mechanism Of Carbon Nanotube Multi-dimensional Multi-scale Hybrid Structures

Since their discovery by detailed observations, carbon nanotubes (CNTs) attracted worldwide attention due to unique structure, excellent physical and chemical properties, and many potential applications. In particular, using CNT as an advanced filler material in composites is one of the most realizable industry applications in the short term. The composites prepared by adding CNTs usually exhibit reinforced and multifunctional properties. However, it is difficult to well disperse and distribute CNTs in polymer matrix when fabricating CNTs-based composites, because CNTs are usually entangled and aggregated due to high aspect ratio and nanoscale interface. To well disperse CNTs in composites and retain intrinsic properties of CNTs, we designed some multi-scale and multi-dimension hybrid structures based on self-assembly CNTs, which can significantly improve CNT dispersion in composites and had many other advantages. The morphology and organization mode of CNTs in hybrid structures greatly influenced the properties of composites. Therefore, we studied the effect of experimental parameters and substrate nature on hybrid structures, and the formation mechanism of multi-form hybrid structures was also investigated in detail.In addition, some hybrid structures with special CNT organization were applied to enforce the properties of composites and the corresponding relationship of structure and property was discussed. The main contents of this paper are presented as follows:(a) The chemical vapor deposition (CVD) process of several hydrocarbons involved was investigated experimentally. The effect of experimental parameters on thermal decomposition and the function of catalyst and substrate in catalytic decomposition of hydrocarbons were studied, respectively. The results indicated that the effect of H2 and the formation mechanism of carbon for these hydrocarbons were different. However, the bezene ring (C6H6) seemed to be a necessary intermediate for carbon formation from hydrocarbons.(b) The controllable preparation and formation mechanism of multi-scale hybrid structures based on CNTs and Al2O3 spherical particles were studied. The influence of reaction conditions and surface properties of Al2O3 spherical particles on hybrid structures were investigated, respectively. Three special forms of CNTs/Al2O3 hybrid structures were prepared, and the formation mechanism for different hybrid structures was discussed. Stacked CNTs/Al2O3 hybrid structures were prepared to monitor the CNT growth quasi-in situ, and the formation process of the boundary between stacks was discussed. Hybrid structures were used in waterborne acrylic polyurethane (PU) paint to improve its properties (hardness, thermal and electrical conductivity, etc.), and this CNTs/Al2O3-PUS composite shows great potential in the field of aerospace.(c) The controllable preparation and formation mechanism of multi-scale hybrid structures based on CNTs and SiC plate-like particles were studied. The co-effect of experimental conditions and SiC surface nature on the CNTs/SiC hybrid structures was researched in detail. Two special forms of CNTs/SiC hybrid structures were prepared and the related formation mechanism was discussed. The prepared CNTs/SiC was used in Polyvinylidene Fluoride (PVDF) polymer matrix to fabricate CNTs/SiC-PVDF composites. The results showed that the thermal and electrical conductivities of composites were greatly reinforced and the conductivity was asymmetric in different directions. The direction-related difference can be tuned by the content of hybrid structures in composites. The corresponding the structure-property relationship was analyzed. Perfectly self-assembly CNT array on micro-particles can be arranged directionally in composites by facile fabrication process. As a result, different types of conductive networks were formed in parallel and perpendicular directions, which led to the direction-related property difference.(d) The controllable preparation and formation mechanism of multi-dimension hybrid structures based on CNTs and graphene nanosheets (GNs) were studied. The effects of surface area of GNs and experimental conditions on hybrid structures were investigated, and the optimal experimental parameters were acquired. This multi-dimension hybrid structure can effectively prevent GNs aggregating and restacking in composites and can be used in the fields of lithium-ion battery and multifunctional composites.