| Nanodiamonds and carbon nanotubes, which are nano carbon materials, possess great potential in a variety of application fields. However, they also have the poor thermal stability of carbon and the aggregation of nanopowder, significantly embarrassing their application. Modifying the surface of nanodiamonds and carbon nanotubes with proper deposition methods could effectively resolve the above problems. Besides, the nano-coating with new properties would also broaden the application of nanodiamonds and carbon nanotubes. In this thesis, quasi atomic layer deposition method has been used to coat nanodiamonds and carbon nanotubes with silicon and titanium. Titania and zirconia nano-coatings have also been acquired by oxidizing of titanium and hydrolyzing of ZrOCl2?8H2O, respectively.Silicon film was coated on nanodiamonds and carbon nanotubes by quasi atomic layer deposition from SiH4. With deposition temperature increasing from 400 to 500 ?C, the structure of the film changes from polycrystalline to amorphous. When the temperature continues to go up from 500 to 600 ?C, the film converts from amorphous to polycrystalline. At 500 ?C, the almost amorphous film is much more even and conformal. The thickness of the coating deposited per cycle is 1-2 nm on average. By repeating the deposition cycle, the thickness of the coating increases. Continuous silicon film could effectively protect nanodiamonds and carbon nanotubes from oxidation. After heating in air to 1300 ?C, the weight loss of 10 times Si-coated 5 nm diamonds and carbon nanotubes are only 1.23% and 6.68%.Quasi atomic layer deposition was also utilized to coat nanodiamonds and carbon nanotubes with titanium from gaseous H2 and TiCl4. The coating deposited at 650 ?C is mainly hexagonal phase Ti, consisting of stick-like nanoparticles. While the relatively smooth coating deposited at 750 ?C is almost cubic phase TiC, for higher temperature promotes the interface reaction. By repeating the deposition cycle, the thickness of the coating increases, but the structure and morphology of the coating does not change much. With titanium coating, the dispersible stability of nanodiamonds and carbon nanotubes in ethanol improves dramatically. By oxidizing Ti-coated (700 ?C, 5 cycles) nanodiamonds and carbon nanotubes in air for 20 min, titania coating was obtained on the surface. With the oxidizing temperature increasing from 500 to 900 ?C, the structure of the coating changes from anatase to more stable rutile. The entire surface of nanodiamonds and carbon nanotubes is covered by continuous titania coating, which is composed of spherical nanoparticles less than 10 nm.Extremely conformal zirconia coating was deposited on nanodiamonds and carbon nanotubes by long time isothermal hydrolyzing of ZrOCl2?8H2O at 90 ?C. Core-shell structural nanodiamonds (carbon nanotubes) / zirconia nanocomposites were successfully prepared. The thickness of the monoclinic phase zirconia coating increases with the hydrolyzing time.SiC and TiC bonded nanodiamond compacts were sintered at 1300 ?C, 5 GPa for 90 s from silicon and titanium coated nanodiamonds deposited by different cycles. The tensile strength of the compacts sintered from 10 times deposited samples is the highest for the proper thickness of the coating. The bonding phase formed in situ distributes homogeneously among the nanodiamond particles, which could not only prevent the nanoparticle from abnormal grain growth but also lead to the sintering of the compact.Coating nanodiamonds with titania or zirconia could improve the electrochemical activity of nanodiamond electrodes. Anatase coated nanodiamond powder electrode could catalyse the oxidation of NO2?, which would possess great potential in detecting and treating pollutant. Pt-ZrO2/ND electrode, more active and stable than Pt/ND electrode, could catalyse the oxidation of methanol, which would be candidate in direct methanol fuel cells.
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