| Along with the advance of science and technology,new materials research gradually intends to the complex structure and functional comprehensive direction.At present,through regulating the fine structure of the ceramic,to improve the comprehensive performance of ceramics has become research hotspot.Nanometer oxide ceramic grain,grain boundary and the combination between them are in nanometer level,which makes ceramic strength,toughness and superplastic increased significantly.It overcomes many disadvantages of engineering ceramics,and has important influence on ceramic mechanical,electrical,thermal,magnetic and optical properties.However,the raw material must be high purity and good uniformity,low degree of reunion of the nano-scale powders in order to obtain high quality nanostructured oxide ceramic.In this paper,nano spinel powder and Y2O3-MgO nanocomposite powder were prepared by low temperature combustion synthesis using metal nitrate as raw material and sucrose or glucose as fuel combustion synthesis;And nano MgAl2O4 and Y2O3-MgO composite nano ceramics were sintered by spark plasma sintering(SPS),after being characterized of the powders and ceramics,the main conclusions obtained are as followed:With metal nitrate and sucrose as raw materials,to synthesize the nanometer spinel by low temperature combustion MgAl2O4 powder,Study the influence of factors,different calcination temperature,atmosphere and heating rate,on the nano MgAl2O4 powder properties.To prepare nano MgAl2O4 powder,it was found that with the calcination temperature increasing,the grain size of nano MgAl2O4 increased gradually with calcination precursor in 600 ℃一 1100℃ respectively;Meanwhile,it was found that calcining precursor in the O2 environment can decrease the temperature of the formation of MgAl2O4 phase,promote the reaction material diffusion,grain growth.Under the conditions of rapid heating,sucrose and nitrate molar ratio of 2:1 and in the O2 environment,the MgAl2O4 phase was prepared at 400℃,and the single phase MgAl2O4 nano powder was obtained at 700℃.The nanometer MgAl2O4 powder,prepared by low temperature combustion synthesis,has high crystallinity and fine grain size,which is a loose soft aggregation state,and beneficial to decrease the sintering temperature of MgAl2O4 ceramics.Magnesium aluminate spinel ceramics were preparied by discharge plasma sintering process using the nano MgAl2O4 powder as raw materials at sintering temperature of 1280 ℃-1400 ℃.The sample has high hardness;the Vickers hardness of sample values reached 14.5 GPa when the sintering temperature is 1340℃.LaF3 is added in the nano MgAl2O4 powder by adding quantity of 0.2 wt%,0.3 wt%,0.4 wt%and 0.5 wt%,and then MgAl2O4 ceramics were sintered at 1340℃,which resulted in abnormal grain growth,and lots of pores within the grain and grain boundary,reducing the density and the hardness of ceramics.The nanostructure Y2O3-MgO composite ceramic prepared by the spark plasma sintering has shown high infrared transmittance.Using powders with the same grain size,but with different organic impurity content of nano Y2O3-MgO powder to prepare Y2O3-MgO composite ceramic at 1350℃ found that the more pure of the powder,the smaller of the grain size and the higher infrared transmittance of the ceramics have.Using the nano powder with different grain size to prepare Y2O3-MgO composite ceramic at 1350℃,it is shown that as the powder grain size is getting smaller;the hardness and infrared transmittance is higher.When the sintering temperature is 1350℃,the hardness and infrared transmittance of ceramic is best,the sample infrared transmittance reaches 80%at 2-6 μm,and Vickers hardness value reached 10.5 GPa. |
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