| Performances of ceramics are closely related to the properties of feeding powders.The powders with excellent dispersity,uniform composition and controllable size and morphology are prerequisites for the preparation of ceramics with outstanding properties.In this paper,spherical-composite?TiO2-SiO2?and nano-composite?CaO-MgO-ZrO2?powders were prepared by Pickering emulsion method and chemical co-precipitation method,respectively.We expect that spherical-composite powder?TiO2-SiO2?and uniform-distributed nanocomposite powder?CaO-MgO-ZrO2?would be obtained.With titanium sulfate as titanium source and urea as the sedimentation agent,the effects of the amount of hydrophobic SiO2,the volume fraction of oil,the amount of urea,the time of water bath and the concentration of titanium sulfate on the microstructure,crystal type and particle size of the products were investigated via a Pickering emulsion method.By observing the retention rate of emulsion with optical microscope,we speculated the following conclusions.With the increase of the amount of nano-hydrophobic SiO2,the stability and viscosity of emulsion increase gradually.The amount of admixture that continues to increase the influence of SiO2 has no effect on the stability of emulsion.The additional amount of SiO2 has no effect on the stability of the emulsion when the amount of nano-hydrophobic SiO2 is 3.5%relative to the mass of liquid paraffin.The emulsification rate of the emulsion increases gradually with the increase of volume fraction of the oil phase.The increase of oil-phase volume fraction has no effect on the stability of the emulsion when the water volume ratio is 14:6.Scanning electron microscopy?SEM?demonstrates that the particle size of calcined product decreases and possesses a better sphericity with increasing the amount of urea.The particle size of calcined product increases first and then decreases with the gradual prolongation of water bath time.The spherical degree of the obtained product is better with the increase of titanium sulfate concentration.X-ray diffraction?XRD?shows that the crystallinity and the grain size of TiO2 decrease with the increasing of water bath time.By increasing the concentration of titanium sulfate,the crystallinity the grain size of TiO2 increase.Moreover,disappearance of SiO2 peaks in the XRD diagram indicates that the SiO2 is amorphous.Furthermore,LPS result shows that the addition of dispersant isopropyl alcohol has no significant effect on the microscopic morphology of calcined product.In addition,ZrO?NO3?2·x H2O?Mg?NO3?2·6H2O,and anhydrous CaCl2 were used as raw materials to dissolved in deionized water or absolute ethanol,the obtained solution was stirred at 500 r/min for 30 min,and added appropriate amount of precipitant?ammonia?to adjust pH of the solution so as to achieve the simultaneous precipitation of the above three metal ions Zr4+,Mg2+and Ca2+.After centrifugation and washing,the as-prepared mixture was dried at 60? for 12 h and calcined at high temperature for 2 h,respectively.X-ray diffraction?XRD?was used to analyze oxides and their crystal structure.Scanning electron microscope?SEM?was used to observe morphology of the composite powder.Laser particle size analysis?LPS?was used to count particle size distribution.Results of XRD show that there are all of the three oxides?CaO,MgO and ZrO2?in as-obtained composite powder.At the same time,oxide solid solutions were also obtained,and the type of oxide solid solution changes with temperature raise.The content of CaO or MgO dissolved in ZrO2 was also increased along with the increase of temperature,and metal oxide CaO or MgO is mainly distributed in the lattice space of ZrO2.Combined SEM observe with LPS result,the particle size of the composite powder?LPS?is in the micron range while SEM image is nanoscale,which demonstrates that the aggregation of the nanocomposite powder is serious. |
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