Abstract:

A new idea for specific surface area standard reference materials (SRM) which are made of nonporous mono-disperse SiO₂ spheres and the true specific surface area can be calculated accurately from their diameters is presented.Firstly, the mono-disperse SiO₂ spheres were synthesized in bulk.Secondly, the spheres were modified to make them nonporous.Thirdly, the characteristic dimensions, such as the size, density of the spheres, were determined accurately.Finally, the specific surface areas were measured by using a static volumetric type Brunauer-Emmett-Teller (BET) (nitrogen gas) instrument.The experimental results showed that the micro-holes on the surface of mono-disperse SiO₂ spheres were almost be sealed by calcining at the temperature of 1000℃ for three hours.The BET surface area was larger than the geometric specific surface area and the values of the deviation were 1.2 m²·g^-1, 2.0 m²·g^-1 and 3.6 m²·g^-1 for mono-disperse SiO₂ spheres with diameters 1150 nm, 453 nm and 269 nm respectively.In this case, the theoretical value can be used as reference for the determination of the specific surface area of nonporous mono-disperse SiO₂ spheres SRMs.

Key words:

单分散SiO₂微球, 封孔, BET, 比表面积

摘要： 提出一种新型比表面积标准物质的研究思路，即用无孔的单分散SiO₂微球作为比表面积标准物质的材料，它的“真实”比表面积可以通过对其粒径的准确测量，用几何的方法计算出来。这种比表面积标准物质的研制首先要进行单分散SiO₂微球的批量合成；其次是对SiO₂微球进行表面修饰使其表面无孔；再次是对封孔后SiO₂微球的特征尺寸（如粒径、密度）进行测定；最后是进行比表面积的计算和BET测定。实验结果表明：经1000℃灼烧 3h可使SiO₂微球基本不含微孔。采用BET法测量的BET比表面积比它的理论计算比表面积值大，粒径为1150nm、453nm和269nm的SiO₂微球的BET比表面积比它们的理论计算比表面积分别大1.2m²·g^-1、 2.0 m²·g^-1和3.6 m²·g^-1。在这种情况下，计算比表面积值可以作为这类标准物质定值的参考数据。

关键词:

单分散SiO₂微球, 封孔, BET, 比表面积