Investigation of selectivity of crystal growth direction in layered double hydroxides is helpful to control their particle sizes in different directions. Mg-AI layered double hydroxides (LDHs) were synthesized using a coprecipitation method. The influences of aging temperature, aging time, and Mg/AI molar ratio on the crystal structure, the LDHs particle size, and the selectivity of crystal growth in different directions were investigated. The results show that the size of the crystallites in the a direction is larger than that in the c direction for all experimental conditions, indicating faster crystal growth in the a direction than in the c direction. The crystallite sizes in the a and c directions both increase with decreasing Mg/AI molar ratio but with less difference between the sizes in the two directions. Therefore, the crystal growth rate in the c direction increases more than that in the a direction as the Mg/AI molar ratio decreases. The influence of the aging time, aging temperature, and Mg/A Investigation of selectivity of crystal growth direction in layered double hydroxides is helpful to control their particle sizes in different directions. Mg-AI layered double hydroxides (LDHs) were synthesized using a coprecipitation method. The influences of aging temperature, aging time, and Mg / AI molar ratio on the crystal structure, the selectivity of crystal growth in different directions were investigated. The results show that the size of the crystallites in the a direction is larger than that in the c direction for all experimental conditions , 指示 速率 晶长 在 the a growth direction than in the c direction. The crystallite sizes in the a and c directions both increase with decreasing Mg / AI molar ratio but with less difference between the sizes in the two directions. rate in the c direction increases more than that in the a direction as the Mg / AI molar ratio decreases. The influence of the aging time, aging te mperature, and Mg / A