以碳酸锰和碳酸锂为原料、淀粉为燃料,研究了温度(500, 600, 700 ℃)和燃料量(0～30%,质量分数)对固相燃烧合成尖晶石型LiMn_2O_4的影响.实验结果表明,通过固相燃烧合成方法在1 h可快速制备高纯度或单相的尖晶石型LiMn_2O_4产物.在500, 600, 700 ℃添加10%～30%淀粉时,可得到主晶相为LiMn_2O_4的产物,但600 ℃时最好.在600 ℃添加20%淀粉时,固相燃烧合成可得到单相尖晶石型LiMn_2O_4产物;在500和700 ℃淀粉量≤10%时,产物中杂相为Mn_2O_3,而淀粉量≥20%为Mn_3O_4.在600 ℃时,淀粉量达到30%产物中才有极少Mn_3O_4出现.温度较低时易生成Mn_2O_3,高温时易生成Mn_3O_4;加热温度相同时淀粉量对产物晶粒的结晶度影响不大,而淀粉量相同时,产物晶粒的结晶度随加热温度而增加.从化学热力学原理的角度探讨了不同温度和燃料量对固相燃烧合成产物组成的影响.
Spinel LiMn_2O_4 powders were prepared by solid-state combustion synthesis using the manganese carbonate and the lithium carbonate as raw materials and the starch as fuel. The effects of the temperature (500, 600, and 700 ℃) and fuel content (0～30%, mass fraction) on products were studied. The results indicated that high purity or single phase LiMn_2O_4 could be prepared quickly by solid state combustion method in 1 h. At 500, 600, and 700 ℃, products with the main phase of LiMn_2O_4 could be obtained. At 600 ℃, the products were better. Single phase LiMn_2O_4 could be prepared at 600 ℃ with the starch content of 20%. At 500 and 700 ℃, impurity phase was Mn_2O_3 when the starch content ≤10%, and was Mn_3O_4 when the starch content ≥20%. At 600 ℃, little impurity phase of Mn_3O_4 could appear when the starch content reached 30%. Mn_2O_3 could be generated easily at lower temperature, and Mn_3O_4 could be generated easily at higher temperature. At the same temperature, the effect of the starch content on the crystallinity of products was not obvious. With the same starch content, the crystallinity of products increased with the increasing temperature. The above experimental phenomena were explained through thermodynamic analysis.
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