pH值对原位合成镍基SBA—15复合材料的结构和磁性影响

The Effect of pH on the Structural and Magnetic Properties of in-situ Synthesized Ni-incorporated SBA—15 Composites

通过调节强酸性介质溶液的pH值,水热法合成镍基SBA-15复合材料。样品的结构、形貌、比表面和孔径分布分别采用XRD,SEM,TEM和氮气吸脱附来表征。结果显示:当溶液的pH值调节为7时,样品仍然是六方孔道的介孔结构。除了长程有序性和表面积略有减少外,其结构与初始合成的SBA-15的结构非常相似。然而,样品晶胞和壁厚的增加表明更多的镍进入了SBA-15的骨架。当溶液的pH值调节为9时,样品的长程有序性遭到破坏,甚至出现一些堵孔现象。在室温下测量了样品的磁性行为,表明样品具有超顺磁性并且磁性参数Ms,Mr和Hc伴随着样品中镍含量的增加而增大,这是由于pH调节的效果。因此,pH值的调节方法对制备有序的Ni-SBA-15复合材料以及样品中镍含量起着重要的作用。

Nickel-incorporated SBA--15 sieve composites were hydrothermal synthesized through pH-adjusting method from initial strongly acidic media. The structure, morphology, specific surface area and pore size distribu- tion of the as-synthesized samples were characterized by XRD, SEM, TEM and N2 physical adsorption, respective- ly. In consequence, when the pH was adjusted to 7, the sample still exhibited hexagonal mesostructure, which were similar to that of the pristine SBA--15 except for the slightly reduced long-range ordering and specific surface area. However, an increase in the unit cell and wall thickness of samples suggested the incorporation of more Ni in- to the framework of SBA--15. Measurements taken with increasing applied field at room temperature revealed the samples to be superparamagnetic behavior, and magnetic parameters such as Ms, Mr and Hc increased with Ni con- tent in the samples due to the effect of pH-adjusting. Thus, pH-adjusting method played an important role in the preparation and amount of Ni incorporation for ordered Ni-SBA--15 sieve composite.