镁铁双羟基复合金属氧化物的可控合成及晶面生长特征研究

采用成核/晶化隔离法合成镁铁双羟基复合金属氧化物MgFe-LDH,考察了Mg ∶ Fe摩尔比对MgFe-LDH晶形的影响,探讨了晶化温度及晶化时间对晶面生长选择性及晶粒尺寸的影响规律.结果表明,随Mg ∶ Fe摩尔比增大,层板阳离子排列更为规整.晶化温度对晶粒尺寸的影响显著大于晶化时间的影响.晶化温度相同,随晶化时间延长, MgFe-LDH的晶体结构趋于完整,晶粒尺寸变化不大;晶化时间相同,随晶化温度升高,晶体结构趋于完整,晶粒尺寸明显增大.所得到的MgFe-LDH沿a轴方向的晶粒尺寸对晶化温度变化的敏感程度远大于对晶化时间变化的敏感程度,但总是沿a轴方向的晶粒尺寸大于沿c轴方向的尺寸,即110]晶面的生长速率比002]晶面的生长速率快.

Studies on Particle Size Controlled Synthesis and Selectivity of Crystal Growth Direction of MgFe Layered Double Hydroxides

MgFe layered double hydroxides (LDH) have been synthesized at high supersaturation using a new method, involving separate nucleation and aging steps. The influence of aging temperature and aging time on the selectivity of crystal growth in different directions and the particle size of MgFe-LDH have been systematically investigated. XRD analyses show that the arrangement of layered cation in MgFe-LDH becomes more complete with increasing Mg∶Fe molar ratio. It has been shown that with increasing aging time at the same temperature, the crystallinity of MgFe-LDH increased and the particle size became larger. The same effect was observed when samples were aged at an increasing temperature for a fixed period, but the particle size of MgFe-LDH increased dramatically with the increasing aging temperature. The rate of crystal growth inadirection 110 crystalline face was found to be greater than that incdirection 002 crystalline face and the size of the crystallites in the adirection was larger than that in thecdirection under all experimental conditions.