دکتر محمد اکبرزاده پاشا

In this research carbon nanotubes were produced by chemical vapor deposition of acetylene over a mixture of iron and cobalt catalysts supported on nanometric TiO2 and the influences of two synthesis parameters: growth temperature and catalyst composition ratio on properties of end-product carbon nanotubes were investigated. The catalytic basis was prepared by wet impregnation method with different wt% mass ratio of Fe-Co/TiO2=20-0/80, 15-5/80, 10-10/80, 5-15/80 and 0-20/80 wt%. The nanomaterials (catalysts and carbon nanotubes) were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray map of elemental distribution (Xmap) and Raman spectroscopy. The results confirmed that by increasing the growth temperature from 650°C to 800°C; the growth rate, the average diameter and the amount of impurities of grown carbon nanotubes increase and their length and density decrease. Furthermore, it was observed that in comparison with monometallic Fe or Co, bimetallic compositions of these metals exhibit better catalytic activity in growth of carbon nanotubes. The highest yield of carbon nanotubes possessing minimum average diameter was obtained on Fe-Co/TiO2 catalyst with a mass ratio of 10-10/80 wt%.

Bimetallic Fe-Co catalysts supported on nanometric SiC powder were prepared by wet impregnation method and were used to catalyze CNTs from decomposition of acetylene at 850ͦ C by TCVD. The effect of Fe and Co combination ratio in catalytic basis on properties of end product CNTs was investigated using XRD, SEM, TEM and Raman spectroscopy. The results revealed that iron and cobalt are in oxide and cobalt ferrite form.The best growth of CNTs on catalyst sample with wt% Fe:Co:SiC=10:10:80 was achieved. It was observed that the ratio of Fe:Co loading in catalyst-substrate composition is an important factor which can affect the activity of catalytic basis and the characteristics of grown CNTs such as the density and average diameter. Bimetallic Fe-Co catalysts supported on nanometric SiC powder were prepared by wet impregnation method and were used to catalyze CNTs from decomposition of acetylene at 850ͦC by TCVD. The effect of Fe and Co combination ratio in catalytic basis on properties of end product CNTs was investigated using XRD, SEM, TEM and Raman spectroscopy. The results revealed that iron and cobalt are in oxide and cobalt ferrite forms.The best growth of CNTs on catalyst sample with wt% Fe:Co:SiC=10:10:80 was achieved. It was observed that the ratio of Fe:Co loading in catalyst-substrate composition is an important factor which can affect the activity of catalytic basis and the characteristics of grown CNTs such as the density and average diameter.

Nanometric Carbid Silicon (SiC) supported monometallic and bimetallic catalysts containing Fe, Co, Ni transition metals were prepared by wet impregnation method. Multiwall carbon nanotubes (MWCNTs) were synthesized over the prepared catalysts from catalytic decomposition of acetylene at 850°C by thermal chemical vapor deposition (TCVD) technique. The synthesized nanomaterials (catalysts and CNTs) were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Raman spectroscopy. In this paper, using of nanometric SiC powder as catalyst support was examined and the effect of applied catalyst type on characteristics of grown CNTs was investigated. The results revealed that iron, cobalt and nickel are in oxide, cobalt ferrite (CoFe2O4) and nickel ferrite (NiFe2O4) forms and nanometric SiC powder can be applied as an appropriate catalyst support in CNT growth process. It was observed that the produced CNTs on bimetallic Fe-Co possess smaller average diameter, less amorphous carbon and denser morphology compared to other binary metallic combinations. It was found that the catalytic activity of bimetallic composition decreased in the order of Fe-Co> Fe-Ni> Co-Ni. Furthermore, the monometallic Fe catalyst has the most catalytic activity compared to monometallic Co and Ni catalysts.

Monometallic and bimetallic Ni and Co catalytic nanoparticles supported on Titanium dioxide (rutile phase) substrate were preparedby wet impregnation method. These nanoparicles were used as catalysts for synthesis of multiwalled carbon nanotubes (MWCNTs) from acetylene decomposition at 700°C by the catalytic chemical vapor deposition (CCVD) technique. The nanomaterials (catalyst and CNTs) were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman spectroscopy. In this paper, the usage of TiO2 powder as catalyst support was examined and the effect of applied catalyst type on characteristics of grown CNTs was investigated. The results showed that the rutile phase of TiO2 powder can be applied as a suitable catalyst support in CNT growth process. Furthermore, it was observed that the CNTs synthesized on Ni-Co bimetallic catalyst possess smaller average diameters, better quality and less amorphous carbon compared to Ni and Co monometallic catalyst types.