Preparation Of Zirconia With Various Morphologies By Hydrothermal Method And Its Photocatalytic Properties

As a kind of new functional material,zirconia?ZrO₂?has been widely used in oxygen detectors,fuel cells,catalysis and environmental protection fields.With the continuous expansion of ZrO₂ in many application fields,preparation of ZrO₂ powders with different morphologies has become one of the key topics.In recent years,photocatalytic degradation of industrial dyes by zirconia has become a research hotspot,but the morphology effect of ZrO₂ on its photocatalytic performance is still not clear.Therefore,it is necessary to deeply understand the relationship between the morphology of zirconia and its photocatalytic properties.In this paper,multi-morphological and monodisperse zirconia micro-nano powders were prepared by the hydrothermal method,with using Zr OCl₂·8H₂O as zirconium source,and NH₄F,H₃BO₃ and NaBF₄ as mineralizers.The morphology,luminescence and photocatalytic properties were studied with different mineralizer concentration,,and the growth process of different morphological powders was explored by adjusting the process parameters.The results are as follows:?1?ZrO₂ powders synthesized with hydrothermal method was performed on 200 ? for 12 h with NH₄F mineralizer.It was found that,with increaseing the NH₄F concentration,the phase structure of ZrO₂ powders changed from tetragonal to monoclinic.The particle size enlarged,and the spherical shaped powder changed into a spindle shape.The ZrO₂ powders prepared with0.015mol/L NH₄F have the highest photocatalytic property.The degradation rate of methyl orange solution reachd 91% under visible light in 60 min.?2?With H₃BO₃ as mineralize,the monoclinic phase structured and tetragonal shaped aggregates zirconia powders were formed.The adsorption process of zirconia on methyl orange solution fits well with the Largergen pseudo-second-order kinetic model.The absorptiondecolorization efficiency of 12 mg zirconia powders was 64% within 20 min.The photocatalytic behavior of zirconia to methyl orange fit with the first-order kinetic equation.The ZrO₂ powders prepared with 0.03 mol/L H₃BO₃ have the highest photocatalytic property,and the decolorization rate was 71% within 60 min.?3?Monoclinic phased ZrO₂ powders were synthesized with NaBF₄ mineralizerat 200 ? for 12 h.It was found that,with increasing the mineralizer concentration,the morphology had gone from spherical to long column to spindle and finally to disk,and the aspect ratio of zirconia increased first and then decreased.The ZrO₂ powders prepared with 0.01mol/L NaBF₄ have the highest photocatalytic property,and the decolorization rate of methyl orange was86% within 60 min.?4?The growth process of zirconia powder with different morphologies with NaBF₄ mineralizer was systematically studied.It was found that,the growth process of ZrO₂ powder did not meet the traditional Ostwald ripening theory,and it was more consistent with the oriented epiphysis and syntagnatic epiphysis growth mechanism.With increased the mineralizer content,tetragonal shaped particles grew rapidly along c-axis?00l?direction become a rod like particle;then the growth on c-axis was inhibited and b-axis?010?direction became the main growth orientation,at this point the crystal was in a spindle shape;finally the grain grew on the?011?direction and transforms into a disk shape.