Tuning of iron vanadate by bismuth doping to improve galvanic zinc coatings for high corrosion resistance and NIR reflectance

Abstract

The possibility of FeVO4 to be explored as a simple, less toxic and environmentally benign NIR reflective cooling material by bismuth doping to meet the crisis of global warming and urban heat island effect was presented in this work. In this view, the present work involved the synthesis of bismuth doped iron vanadate through a simple, cost-effective co-precipitation method. A remarkable red shift has been achieved in the absorbance of iron vanadate, when doped with bismuth, by the effective tuning of impurity energy levels of bismuth dopant in between the band gap of iron vanadate resulting in the reduction of band gap energy from 2.6 eV to 1.64 eV. The diffraction peaks of the triclinic crystalline phase have been shifted to smaller angles by tuning the composition of the dopant, bismuth in FeVO4 for obtaining maximum NIR reflectance. About 36 % increase in NIR reflectance was obtained for 0.05 M bismuth doped iron vanadate, when compared to bare iron vanadate. The particle size of iron vanadate has been effectively reduced upon doping with bismuth, confirmed from SEM images so that these particles will definitely scatter the incident radiation at an elevated rate and results in enhanced NIR reflectance. Improved tribological properties like least wear rate and high coefficient of friction were exhibited by the coating with highest NIR reflectance. Electrochemical studies showed that the tuned coatings exhibited Ecorr as high as −1307.202 mV and icorr as low as 61.619 µA/cm2. The developed coatings proved to be suitable as an excellent anticorrosive NIR reflective coating with outstanding tribology.