合成条件对Mg-Al-CO_3^(2-) LDHs的物相及组成的影响

Influence of synthesis conditions on the phase and composition of anionic layered material Mg-Al CO_3^(2-) LDHs

以Mg(NO3)2.6H2O为镁源,以Al(NO33).9H2O为铝源,采用共沉淀法制备了阴离子型层状材料Mg-Al-CO23-LDHs,并用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)和透射电镜(TEM)对产物进行了表征。探讨了加料方式、插层阴离子的用量以及沉淀反应温度对所形成产物物相等的影响。XRD分析结果显示不同加料方式所制备的产物均具有典型的层状结构特征,其中pH恒定法所合成的产物结晶度更高;红外光谱显示产物中存在插层阴离子CO32-;EDX元素分析结果表明产物组成中含有Mg和Al,且n(镁)∶n(铝)=2.6。上述表征结果说明:加料方式、插层阴离子的用量以及沉淀反应温度对产物的物相没有影响,但对产物的结晶度有一定的影响。当初始原料的配比为n(Mg)∶n(Al)∶n(OH-)∶n(CO32-)=6∶2∶20∶2时,在45℃下完成沉淀反应,再将沉淀于65℃下晶化18h可以得到具有典型层状结构的Mg-Al-CO32-LDHs。

The Mg-A1 CO2- anionic layered material has been prepared by precipitation method using Mg（NOa）2 6H20 as source of magnesium and Al（NO3）3 9H20 as source of aluminum. The prod ucts are characterized by means of X-ray diffraction（XRD）,infrared spectra（IR）, spectroscopy electron microscopy（SEM）as well as transmission electron microscope（TEM）. The effects of feeding method, the amount of intercalated anions and the precipiteion reaction temperature on the phase were investi gated. The result of XRD showed that the products prepared by different feeding method have the typ- ical layered structure,and crystal structure of the product prepared by the method of pH constant is more perfect. IR spectroscopy showed that CO^- anion has been intercalated into the layer of LDHs. EDX analysis indicated that magnesium and aluminum elements were contained in the layer board of the prepared products,and mole ratio of Mg to A1 is 2.6. The above characterization results demonstrated that the feeding method, the amount of intercalated anions and the pr perature have no effect on the phase of the product, but have effect on the crys ecipiteion reaction temtallinity. The proper ra- tio of starting materials is n（Mg） n（A1） n（OH） ： n（CO^-） =6： 2 ： 20 ： 2. Mg-A1-CO23- LDHs with a typical layered structure can be obtained by carrying out precipitation reaction at 45 °C, and then aged at 65 °C for 18 h.