包覆-热分解碳酸银前驱体制备球形银粉的研究

以碳酸铵为沉淀剂、硝酸银溶液为原料, 利用化学沉淀法制备得到碳酸银前驱体, 通过并流沉淀法包覆改性碳酸银前驱体, 并经热分解得到单分散的球形银粉。通过X射线衍射分析(X-raydiffraction, XRD)、粒度分布统计(particlesize distribution, PSD)、振实密度测量和扫描电子显微检查(scanning electron microscopy, SEM) 等表征手段研究了热分解银粉的结晶度、纯度、分散性、填充性及微观形貌; 讨论了硝酸银溶液浓度和甲醇添加对碳酸银前驱体颗粒分散性和粒径的影响, 并分析了碳酸镁与碳酸银包覆比例(摩尔比) 对银粉分散性的影响。结果显示, 使用包覆-热分解方法可以制备得到单分散的球形银粉, 该方法具有设备简单、投资少、产品分散性好且粒度分布集中的优点; 当硝酸银溶液浓度为0.2~0.5 mol/L时, 可以得到粒径为0.5~2.5μm的球形银粉; 碳酸银分散性可通过添加甲醇进行调整, 甲醇含量(甲醇在硝酸银溶液中的体积分数) 应控制在5%~10%;当硝酸银溶液浓度为0.5 mol/L、甲醇体积分数为5%时, 碳酸镁与碳酸银摩尔比2:1制备得到的球形银粉分散性最佳。

Study on spherical silver powders prepared by silver carbonate precursor modified by cladding-thermal decomposition

The silver carbonate precursor was prepared by chemical precipitation method using ammonium carbonate as precipitation agent and silver nitrate solution as raw material. The cladding silver carbonate precursor was modified by parallel flow precipitation, and the single dispersed spherical silver powders were obtained by the thermal decomposition of modified precursor. The crystallinity, purity, dispersibility, fallibility, and morphology of silver powders were characterized by X-ray diffraction (XRD), particle size distribution (PSD) statistics, tap density test, and scanning electron microscopy (SEM), the influences of silver nitrate solution concentration and methanol adding on the dispersibility and particle size distribution of silver carbonate precursor were discussed, and the effects of cladding ratio (by mole) of magnesium carbonate and silver carbonate on the dispersibility of silver powders were studied. In the results, the single dispersed spherical silver powders can be obtained by cladding-thermal decomposition, which has the advantages of simple equipment, less input, good dispersibility, and the concentrated particle size distribution of products; when the silver nitrate solution concentration is 0.2~0.5 mol/L, the particle size of spherical silver powders is 0.5~2.5 μm; the dispersibility of silver carbonate precursor can be adjusted by adding methanol, the methanol dosage (the volume fraction of methanol in silver nitrate solution) should be controlled as 5%~10%; when the silver nitrate solution concentration is 0.5 mol/L, the methanol dosage by volume is 5%, the optimum dispersibility of silver powders is obtained as the cladding ratio (by mole) of magnesium carbonate and silver carbonate is 2:1.