NaBH₄ Precipitation Synthesis And Catalytic Properties Of ZrO₂

As an important structural and functional material,zirconia has aroused people's attention.At present,the research on the preparation of ZrO2 nano-powder by chemical precipitation mainly focuses on using ammonia as the precipitating agent.In this paper,by selecting and analyzing all kinds of chemical agents that can provide alkaline preparation environment,NaBH4 was chosen as the precipitating agent.NaBH4 is a strong base,not only can provide a strong alkaline environment during reaction,but also release H2 as a reducing gas,which is beneficial to the stability of the tetragonal phase structure.In this paper,ZrOCl2·8H2O was used as the zirconium source and NaBH4 as the precipitating agent,a certain amount of surfactant(CTAB)was added during the preparation of the precursors.Four influencing factors which can affect the phase structure,morphology and photo-catalytic properties of ZrO2 were studied systematically,such as the concentration of Zr4+,surfactant,alkali and precipitating orientation.And the best synthesis process was optimized.In the second stage,Mn?Fe doped ZrO2 were prepared based on the optimal preparation process.The relationship among the organization,structure,and performance with the doping element were studied.The stability mechanism of tetragonal ZrO2 and the formation mechanism of oxygen vacancy defects were also discussed.The main results were as follows:1.The optimum preparation conditions of pure ZrO2 powder were that the concentration of Zr4+,NaBH4,CTAB were 0.5 mol/L,lmol/L and 0.005 mol/L respectively.A reverse setting method was used until the titrated pH reached 9.5.Then the precursor was calcined at 600?for 2 h to obtain a tetragonal structure,sheet-like and dispersive powder.With the prepared ZrO2 as catalyst,the degradation rate of MB was reached 96%after ultraviolet light for 2 hours.2.Mn?Fe doped ZrO2 was prepared on the basis of the front optimal synthesis process.Pure tetragonal phased Mn?Fe doped zirconia was obtained when calcined at 600?,but tetragonal to monoclinic phase transformation would happen with higher temperatures.Zr0.8Mn0.2O2-? and Zr0.99Fe0.01O2-? powers showed a cross-sectional structure which deposited by platelet-like micro-structure.The doping element increased the crystallization temperature of ZrO2 significantly and the phase stability of tetragonal zirconia.The reason is that the oxygen vacancy defects formed with doping elements,played a important part in enhancing the stability of the high temperature phase,and improving the phase transition temperature;3.Mn?Fe-doped ZrO2 revealed unique luminescent properties.The PL emission peak was at 390 nm when excitated by 240 nm light,which due to its intrinsic excitation.With the increase of the doping concentration,the emission peak position is slightly blue-shifted.When excitated at 490 nm,the PL emission peak with different peak intensities located at 600 nm,which is due to oxygen vacancy defection.The PL emission peak intensity increases with the increase of defects in the system.4.The photocatalytic property of Mn/Fe doped ZrO2 was verified by the degradation of MO through visible light.The results showed that the doping of Mn/Fe ions could significantly increases the photocatalytic activity of ZrO2 powders.The catalytic property of Fe-doped ZrO2 was better than that of Mn-doped ZrO2.The catalytic of the Fe doping ZrO2 powders increased with adding the doping amount.The degradation rate of MO with Zr0.7Fe0.3O2-? as catalyst was 95.1%after visible light for 1h.