Properties And Characteristics Of Transparent MgAl₂O₄ Spinel Ceramics Prepared By Freezing Granulation

Magnesium-aluminum spinel is a polycrystalline material with composite function.It has excellent mechanical properties and high light transmittance in a wide wavelength range and suitable for the protective window of military aviation.Spray freeze-drying combines the advantages of freeze drying and spray drying,and removes solvent water by sublimation to avoid component migration caused by capillary action and the granule have regular shape and uniform composition.Therefore,the spray-freeze-drying method was used to prepare magnesium-aluminum spinel transparent ceramics,and the influence of process conditions on the properties of ceramics was studied.The main contents of the paper are as follows:By optimizing the spray conditions,the granules with excellent flow properties were prepared under the condition(1.0:0.5 MPa,solid content 20 vol%,3 wt%PVA).It is also found that the yield stress of granules increases with the increase of solid content and addition of PVAThe effects of granules flowability and yield stress on the properties of ceramics were analyzed.It was found that the good flowability beneficial for the transmittance of ceramics at the 300 nm to 400 nm wavelength,the transmittance of ceramic with solid content 30 vol%was 72.33%at 400 nm wavelengthThe effect of different calcium doping methods on the properties of granules and ceramic was compared by doping solid CaCO3 and liquid Ca(NO3)2.It was found that the flowability and yield stress of granules are not affected by Ca doped form and amount.When calcined at 1510℃,the relative density of 0.1 wt%Ca(NO3)2 body is 99%and the 0.1 wt%CaCO3 body is 96.86%.At the same doping level,the transmittance of the doped Ca(NO3)2 sample is better than the CaCO3.When the HIPing temperature is 1600℃,the light transmittances of ceramics with 0.05 wt%CaCO3/Ca(NO3)2 are 51.02%and 53.87%,respectively.Figure 45;Table 11;Reference 77...