Preparation and mechanism of nano antimony⁃doped tin oxide @ fly ash antistatic composite powder

Coal⁃based solid waste treatment and polymer material fire are two important problems to be solved urgently in our country. The study of economical coal⁃based antistatic composite powder has great value and practical signifi⁃ cance for realizing high⁃value utilization of coal⁃based solid waste and solving the fire problem caused by electrostatic accumulation of polymer materials. Fly ash，as one of the coal⁃based solid wastes with high output，has attracted more and more attention to realize high⁃value utilization as a filler，but the problem of fly ash with high resistivity when being filled in polymers has not been solved. Nano antimony doped tin oxide has good antistatic properties，but its disper⁃ sibility is poor and the cost is high. Based on this，according to the idea of “particle design”，nano antimony⁃doped tin oxide(ATO) was loaded on low⁃cost fly ash by heterogeneous nucleation method，and the core⁃shell structure composite powder was prepared to improve the dispersion of ATO and reduce the electrical resistivity of fly ash. The effects of different pH value，coating amount，SbCl3 to SnCl4 ·5H2 O molar ratio，calcination temperature and calcina⁃ tion time on the volume resistivity of composite powder were studied. Scanning electron microscope(SEM)，X⁃ray dif⁃ fraction(XRD)，Fourier transform infrared spectroscopy(FTIR)，Energy dispersive X⁃ray spectroscopy(EDS)，X⁃ray fluorescence spectrometer(XRF)，Zeta potential meter were used to analyze the physical and chemical properties of fly ash and the composite powder. The heterogeneous nucleation mechanism and antistatic mechanism of the composite powder were discussed. The results show that the volume resistivity of fly ash has decreased from 1. 724 × 1012 Ω·cm to 2.36×105 Ω·cm when the pH value is 4，the coating amount is 30%，calcined at 700 °C for 2 h， and the molar ratio of SbCl3 to SnCl4 ·5H2 O is 1 ∶ 6. The surface of fly ash is uniformly coated with nano ATO parti⁃ cles. There is electrostatic attraction between fly ash and ATO precursor at pH4. Sn(Sb)—OH condenses with Si— OH on the surface of fly ash to from Si—O—Sn(Sb) bonds. Nano-ATO is precipitated on the surface of fly ash in a heterogeneous nucleation manner，and after high temperature calcination，Sb-SnO2 with rutile structure with conduc⁃ tive function is formed. The conductive carriers of ATO mainly depend on the oxygen vacancies formed by Sb5+ and SnO2 ，resulting in a decrease in the volume resistivity of fly ash. The composite powder has good application pros⁃ pects as fillers in antistatic coatings and plastics.