Zn-Mg-Al型类水滑石纳米颗粒制备及晶体结构

采用液相非稳态共沉淀法合成了锌镁铝类水滑石(Zn-Mg-Al-HTlc)颗粒,考察了其化学组成、晶体结构、粒子形貌及原料配比的影响等.结果表明,Zn-Mg-Al-HTlc样品中的n(Zn)/n(Zn+Mg+Al)比原料配比低,而n(Mg)/n(Zn+Mg+Al)基本无变化.n(Al)/n(Zn+Mg+Al)(x)在0.22～0.40范围内是纯类水滑石相,超出此范围时出现异相;x<0.22时出现ZnO相;x>0.40时出现Al(OH)₃相.所制备的Zn-Mg-Al-HTlc颗粒的晶胞参数a=0.27～0.32nm,c=2.27～2.42nm,层间距在0.75～0.81nm之间,层间通道的高度约0.30nm.样品颗粒均为较规则的六边形片状粒子.XRD-Scherrer公式计算结果表明,粒子的平均晶粒度在30～45nm之间.TEM结果表明,平均颗粒度随x的值趋于减小,x<0.33时平均颗粒度基本小于100nm.x值相近,Zn含量增加,平均颗粒度有增大趋势;n(Zn)/n(Al)相近,Mg含量增加,平均颗粒度有减小趋势.

Studies on Preparation and Crystal Structure of Ultrafine Particles Zn-Mg-Al-Hydrotalcite-like Compound

The particles of zinc magnesium aluminum hydrotalcite like compound(Zn-Mg-Al-HTlc) were synthesized by nonsteady coprecipitation method. Their chemical composition, crystal structure, particle morphology and the influence of material ratio were studied. The results show that the molar ratio of (Zn+Mg) to (Zn+Mg+Al) in preparing Zn Mg Al HTlc samples is lower than that of the material, and so is the molar ratio of Zn to (Zn+Mg+Al). However, the molar ratio of Mg to (Zn+Mg+Al) has no changes basically. Pure HTlc phase forms when molar ratio of Al to (Zn+Mg+Al)(x) is between 0.22 and 0.40, and different phases will form beyond this range. When x is lower than 0.22 or higer than 0.40, ZnOor Al(OH)₃ will emerge respectively. The lattice parameters of Zn-Mg-Al-HTlc particles, a = 0.27 -0.32 nm; c =2.27-2.42 nm; basal spacing is in the range of 0.75-0.81 nm. The height of gallery is about 0.30 nm. It was found that the particles of prepared samples are comparatively complete hexagonal plate particles. The particle size is determined respectively by TEM, particle size instrument and XRD-Scherrer formula. It is proved by XRD-scherrer formula that the particle′s mean crystal grain is between 30- 45 nm . The TEM results show that the mean particle size decreases with the decreasing of x . That is, when the content of divalent metal cations increases, the mean particle size decreases. When x is lower than 0.33, the mean particle size is basically lower than 100 nm. Remaining constant x, the mean particle size has an increasing tendency with the increasing of Zn content; with the increasing of Mg content, the mean particle size has a decreasing tendency.