Amorphous SiO2 Shell Research Articles

Nanoprocesses in polymer‐derived Si–O–C ceramics: Electronmicroscopic observations and reaction kinetics

AbstractNickel acetate doped poly(methylphenylsilsesquioxane) with and without silicon filler loading was pyrolysed in argon atmosphere between 800 and 1500 °C. The ceramic residues were investigated with specific view of the nanoaggregates formed in pores during the polymer‐to‐ceramic conversion. After pyrolysis at 900 °C carbon nanotubes as well as nanowires with a crystalline SiC core and an amorphous SiO2 shell were found in Si filler‐free and Si filler‐loaded samples, respectively. The evolution of the microstructure and the composition of these carbon nanotubes and SiC/SiO2 nanowires were studied by HREM, SEM, EELS, EFTEM and evolved gas analysis. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Formation of ZnS/SiO2 nanocables

Nanometer-sized coaxial cables with a single-crystal ZnS core and a thin amorphous SiO2 shell were synthesized by simple thermal evaporation in vacuum. As-fabricated ZnS/SiO2 nanocables were studied using scanning electron microscopy, x-ray diffraction and transmission electron microscopy. The ZnS/SiO2 nanocables have diameters of ∼50nm, lengths of several tens of micrometers, and shell thickness of ∼4nm. The core of the nanocable has a wurtzite structure with a growth direction along [001]. The nanocables show strong photoluminescence with two peaks related to band gap and defect-related emission.

Helical nanocables with SiC core and SiO2 shell

A novel one-dimensional helical nanocable structure has been synthesized through the reaction of carbon fiber with SiO vapor. The crystalline SiC core typically has diameters of 10–20nm with a helical periodicity of 30–40nm and is covered by a uniform layer of 10–20nm thick amorphous SiO2. A growth mechanism is proposed on the basis of difference in the growth rate between crystalline SiC core and amorphous SiO2 shell.