Resumen de Doping & decoration of carbon based nanoparticles: applications in flame retardancy and catalysis
The present work involves two main parts that will be explained after the introduction. A brief introduction about history, properties, synthesis and characterization of carbon nanotubes, graphene and their nanocomposites and nanohybrids will be presented.
The first part of the thesis is focused on the synthesis of different types of nanotubes: pristine carbon nanotubes (CNT), oxygen doped carbon nanotubes (COx), and nitrogen doped carbon nanotubes (CNx) by CVD method. The structure of the nanotubes was confirmed by XRD, XPS, SEM, TEM, TGA and Raman spectroscopy (Chapter 2). The most important difference between the synthesized nanotubes was their aspect ratio which is calculated from 1500-3000 for CNx to COx. Pristine CNT shows the aspect ratio about < 2000.
Subsequently, the epoxy nanocomposites at 2 wt.% constant loading of carbon nanotubes (CNT, COx, and CNx) and Diglycidyl ether bisphenol-A (DGEBA) as a good example of thermosetting polymer were have been prepared by three roll milling and cured by 4,4′- Diamio diphenyl sulfone (DDS) as a hardener. The thermal degradation of epoxy nanocomposites, as well as glass transition temperatures and elastic moduli, were measured by TGA, DSC, and DMTA.
The flammability of epoxy nanocomposites was studied by microscale combustion calorimetry (MCC) and limiting oxygen index (LOI) determination. Results showed that the fire retardant properties of nanocomposites improved significantly especially for COx, which presented a very high LOI (35%) and a homogeneous and uniform surface after burning. This effect was attributed to the very high aspect ratio of COx tubes. The results showed that introduction of the nanofillers at 2 wt.% loading caused the earlier initial decomposition of the nanocomposites, an increased char yield, and a reduction of the degradation rate of in comparison with pure epoxy.
The influence of the addition of nanofillers on the relaxational and mechanical behavior of nanocomposites was evaluated by DSC and DMTA. No significant variations in Tg, storage modulus or loss tangent width were detected, indicating that the addition of nanofillers does not negatively affect the relaxational and mechanical response of the nanocomposites (Chapter4).
In the second part of our work, different copper nanocomponents were synthesized and decorated on graphene oxide by our microwave-assisted method. Copper hydroxyl nitrate double salt (DS) (Cu2(OH)3(NO3) and cuprous oxide (Cu2O) by changing the solvent in a very simple procedure were obtained from copper nitrate.
Copper nitrate (CuO) and metallic copper can be prepared from heating and reduction by ascorbic acid of DS, respectively.
The four copper salts have been decorated on graphene oxide GO following the same microwave-assisted method. (Chapter 3) The performance of copper salts/GO nanohybrids as photocatalyst in the degradation of one common dye (Rhodamine B) has been studied. As we expected, incorporation of copper oxides (copper with different oxidation number) onto GO via our method resulted in enhancing the properties of initial metal oxides and it was comparable with the CuO and Cu2O/GO hybrids produced of conventional methods Photocatalytic activity of DS alone and decorated on GO has been reported for the first time in this work.
In the last part of the thesis, we have checked the performance of decorated copper salts as a catalyst in some common organic reactions like C-C, C-N, and C-S coupling and oxidation of aldehyde (Chapter 6). The catalytic application of DS is introduced for the first time here. The results open up the possibility of a more thorough study of the catalytic performance of the supported copper double salt in other conditions which may be applied in the future for different catalytic and consecutive processes of organic synthesis.
