低温燃烧合成MgAl_(2)O_(4)多孔陶瓷及其性能研究

Preparation and properties of porous MgAl_(2)O_(4) ceramics by low-temperature combustion

为降低MgAl_(2)O_(4)的合成温度,减少能耗,以硝酸铝、硝酸镁和硝酸铵作为氧化剂,甘氨酸、尿素(CH_(4)N_(2)O)作为还原剂,乙二胺四乙酸(EDTA)为燃料,低温燃烧合成MgAl_(2)O_(4)粉体,并分别用该粉体和800℃处理后粉体制备了MgAl_(2)O_(4)多孔陶瓷。研究了EDTA加入量(分别为还原剂物质的量的0、2.5%、5%、7.5%)对MgAl_(2)O_(4)粉体及其多孔陶瓷性能的影响。结果表明:1)随EDTA加入量的增大,MgAl_(2)O_(4)粉体的烧失率增加,比表面积显著增大;2)随EDTA加入量的增大,MgAl_(2)O_(4)多孔陶瓷的吸水率和显气孔率显著降低,体积密度明显增加,MgAl_(2)O_(4)晶粒尺寸有所减小;3)与800℃处理后MgAl_(2)O_(4)粉体相比,用未处理的合成MgAl_(2)O_(4)粉体制备的多孔陶瓷的吸水率和显气孔率相对较高,显微结构较均匀;4)当EDTA加入量为还原剂的2.5%(x)时,以未处理的合成MgAl_(2)O_(4)粉体制备的多孔陶瓷的吸水率为23.8%,显气孔率为46.9%,体积密度为1.9 g·cm^(-3),显微结构较均匀。

To lower the synthesis temperature of MgAl_(2)O_(4)and the energy consumption,MgAl_(2)O_(4)powders were synthesized via a low-temperature combustion route using Al(NO_(3))_(3)·9H_(2)O,Mg(NO 3)_(2)·6H_(2)O and NH_(4)NO_(3) as oxidizing agents,C_(2)H_(5)NO_(2) and CH_(4)N_(2)O as reducing agents,and EDTA as the fuel.Then porous MgAl_(2)O_(4)ceramics were prepared with the prepared powders or the prepared powders treated at 800℃.The effects of the EDTA addition(0,2.5%,5%,7.5%of the reducing agents,by mole)on the properties of the MgAl_(2)O_(4)powders and the porous MgAl_(2)O_(4)ceramics were studied.The experimental results show that:(1)with the increase of the EDTA addition in the precursors,the ignition loss increases and the specific surface area of the MgAl_(2)O_(4)powders rises significantly;(2)with the increase of the EDTA addition in the precursors,the water absorption and the apparent porosity of the porous MgAl_(2)O_(4)ceramics obviously decrease,the bulk density increases significantly,and the grain size of MgAl_(2)O_(4)decreases slightly;(3)compared with the ceramics prepared from the MgAl_(2)O_(4)powders treated at 800℃,the porous MgAl_(2)O_(4)ceramics prepared with the MgAl_(2)O_(4)powders have relatively higher water absorption and apparent porosity,and more uniform microstructure;(4)when the EDTA addition is 2.5%of the reducing agents,the porous ceramic sample prepared with the MgAl_(2)O_(4)powders has the water absorption of 23.8%,the apparent porosity of 46.9%,and the bulk density of 1.9 g·cm^(-3),presenting uniform microstructure.