A facile process to prepare crosslinked nano-graphites uniformly dispersed in titanium oxide films as solar selective absorbers

A composite film containing uniform nano-crystallized carbon (nc-C) embedded in titanium oxide (TiO2) matrix has been fabricated by a facile sol-gel technique as selective solar absorbers. The high-resolution transmission electron microscopy demonstrated the nc-C grains, whose size ranges from 2 nm to 10 nm, make up a crosslinked network. The structural template (polyethylene glycol) used in the present work could tune the carbon contents of the composite films. The optimized solar absorptance and thermal emittance of the single layer film on copper substrate were about 0.939 and 0.195, respectively. The little deterioration after aging test (at 500 °C for 30 h in vacuum) demonstrated an outstanding durability of nc-C/TiO2 nano-composite films. Further investigations on the structure and solar selective properties revealed that both excellent optical performance and structural stabilities benefit from nc-C and nano-composite effects. Therefore, this nc-C/TiO2 film has been proved to be a good candidate for solar selective absorbers.