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Abstract Coatings of carbon nanoparticles dispersed in SiO2, ZnO and NiO matrices on aluminium substrates have been fabricated by a sol&#8211;gel technique. Spectrophotometry was used to determine the solar absorptance and the thermal emittance of the composite coatings with a view to apply these as selective solar absorber surfaces in solar thermal collectors. Cross-sectional high resolution transmission electron microscopy (X-HRTEM) was used to study the fine structure of the samples. Raman spectroscopy was used to estimate the grain size and crystallite size of the carbon clusters of the composite coatings. X-HRTEM studies revealed a nanometric grain size for all types of samples. The C&#8211;SiO2, C&#8211;ZnO and C&#8211;NiO coatings contained amorphous carbon nanoparticles embedded in nanocrystalline SiO2, ZnO and NiO matrices, respectively. Selected area electron diffraction (SAED) showed that a small amount of Ni grains of 30 nm diameter also existed in the NiO matrix. The thermal emittances of the samples were 10% for C&#8211;SiO2, 6% for the C&#8211;ZnO and 4% for the C&#8211;NiO samples. The solar absorptances were 95%, 71% and 84% for the C&#8211;SiO2, C&#8211;ZnO and C&#8211;NiO samples, respectively. Based on these results, C&#8211;NiO samples proved to have the best solar selectivity behaviour followed by the C&#8211;ZnO, and last were the C&#8211;SiO2samples. Raman spectroscopy studies revealed that both the C&#8211;ZnO and C&#8211;NiO samples have grain sizes for the carbon clusters in the range 55&#8211;62 nm and a crystallite size of 6 nm.</p

FTIR and Raman Spectroscopy of Carbon Nanoparticles in SiO2, ZnO and NiO Matrices