Renato Bonadiman

Amorphous nanowires and crystalline thin films of SiO2?Li2O compounds obtained by combustion chemical vapour deposition

Amorphous silica films deposited by combustion chemical vapour deposition (CCVD) were modified by lithium addition in the precursor solution. The modified films were characterized by x-ray diffraction and scanning and transmission electron microscopy. The addition of lithium promoted the crystallization of Li2O–SiO2 compounds, mainly crystalline phases like Li2SiO3, Li2Si2O5, quartz and cristobalite. Besides this, the morphology of the film was modified, leading to the formation of acicular structures and nanowires. Selected area electron diffraction (SAED) and microprobe EDS analysis indicated that the nanowires are amorphous and probably constituted of silica.

Multiwalled carbon nanotubes catalytically grown from amorphous silica films deposited by combustion CVD

Homogeneous mixtures containing iron oxide and amorphous SiO2 were obtained through the co-deposition of these oxides via combustion chemical vapor deposition technique (CCVD). This technique allows the deposition of thin films with low-cost precursors and equipments. After deposition, the deposited samples were submitted to a heat treatment in an atmosphere composed of natural gas and H2 at 1000°C, in order to promote the growth of carbon nanotubes. Multiwalled carbon nanotubes, with diameters smaller than 15 nm, were obtained.