Application Of Carbon Nanotubes In Micro-Nano Devices And Composite Materials

Carbon nanotubes (CNTs) have a lot of unique physical and chemical properties. Taking the advantages of their electrical properties, CNTs can be integrated into the micro and nano electronic devices. CNTs can also be used to fabricate innovative composite materials, owing to their outstanding mechanical and thermal characteristics,.In the application of CNTs in micro and nano electronic devices, the integrated design is a rather critical issue. While fabricating new CNT reinforced composites, there still exists lots of challenges in order to enhance their mechanical and thermal properties especially at high temperature.To meet the challenges, this thesis studied the multi-scaling design and fabrication of the products based on CNTs, including electronic device, composite material and heat exchangers. The concerned work and main conclusions can be summarized as follows:(1) By using plasma enhanced chemical vapor deposition, vertically aligned CNTs (VACNTs) were obtained. The effects of substrate and barrier layer material, sizes of catalyst particles and thicknesses of underlayer to the CNT growth were studied. The results showed that when using substrate of HR Si/2/μm SiO2/50nm TiW, barrier layer of TiN, Ni catalyst size of100-200nm in diameter and Cu underlayer of20nm thick, CNTs growth results were acceptable.(2) By altering the processing parameters:increasing feeding gas of NH3from300sccm to360sccm and prolonging preheating time from3min to4.5min, VACNTs growth integrated in micro-nano electronic switch was improved, and it basically met the requests of design.(3) Tensile tests of CNT reinforced aluminum composite (CNT/Al) at high temperature were carried out. The tensile strength of CNT/Al is about150MPa which is2.5times higher than aluminum matrix at300℃, thanks to the reinforcing effect of CNTs added. Based on representative volume element (RVE) model, the elastic modulus of CNT/Al was calculated by finite element method (FEM) software, which was73.1GPa, matching well with the result got in test tests.(4) By using flash method, the thermal conductivity of CNT/Al was obtained, which is332.786W/(m·K) at room temperature. Also the simulated result was calculated through the RVE model in the FEM software, which met well with the test result.(5) By applying CNT/Al material into the design of micro heat exchanger at high temperature, the performance of heat transfer and resistance was calculated by computational fluid dynamics (CFD)simulation. The overall properties were compared with the stainless steel one at the exactly same working condition. The results indicated that CNT/Al could reduce the weight of the heat exchanger exceedingly while maintaining the heat properties.