温度对硝酸盐体系液相燃烧合成产物LiMn_2O_4的影响

以硝酸锂和硝酸锰为原料,尿素为燃料,用液相燃烧合成方法制备尖晶石型LiMn2O4物质,考察了焙烧温度(300-800℃)和焙烧时间(0-48h)对产物的组成结构和晶粒大小的影响.实验结果表明,未焙烧产物中主晶相为LiMn2O4,但含有大量Mn2O3;在300-800℃焙烧时,温度越高,所得尖晶石型LiMn2O4的纯度越高、晶粒越大、晶粒发育越完整,焙烧温度≤600℃时焙烧时间对提高产物中LiMn2O4的纯度影响不大,产物颗粒为纳米级,但焙烧温度大于700℃时影响较大,产物颗粒增大,产物中Mn2O3的含量随焙烧时间增加减少的幅度较大,制备LiMn2O4燃烧产物的最佳焙烧温度为800℃,保温6h左右.但焙烧温度为800℃焙烧时间大于8h时,LiMn2O4会分解生成Mn3O4.

Effect of Calcination Temperatures on Spinel LiMn_2O_4 Prepared by Solution Combustion Synthesis in Nitrate System

Spinel LiMn2O4 powders were prepared by solution combustion synthesis using nitrate lithiumand manganese as raw materials, and urea as fuel. The effects of calcination temperatures （300-800℃） and calcination times （0-48h） on the phase composition and grain size of products were studied. The results indicated that the product that was not calcinated had the main phase of LiMn2O4, and a mount of impurity of Mn2O3. At the calcination temperature of 300-800 ℃, the purity of LiMn2O4 increased, the grain size en- larged, and the crystallization was better, with the increasing temperatures. The effect of calcination time on the products was inconspicuous below 600℃, and notable above 700℃. Scanning electron microscope （SEM） images showed that nanocrystalline LiMn2O4 was obtained when the calcination temperature was lower than 600℃ and the grain size increased at higher temperatures. Above 700℃, the content of Mn2O3 in products decreased with increasing calcination times. The optimum calcination temperature was 800℃ for 6h. At 800℃, if the calcination time was greater than 8h, LiMn2O4 would be decomposed to Mn3O4.