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 pr...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.展开更多
The accuracy of solid density primary standard is decided mainly by the accuracy of the diameter measurement of silicon sphere. With traditional five-interferogram algorithm to unwrap phase for di- ameter measurement,...The accuracy of solid density primary standard is decided mainly by the accuracy of the diameter measurement of silicon sphere. With traditional five-interferogram algorithm to unwrap phase for di- ameter measurement, the phase steps should be equal to π/2 exactly, but this is almost impossible to achieve in nanometer positioning technique. In order to overcome this defect, we have derived an im- proved five-interferogram algorithm, which not only keeps the high accuracy of traditional five-inter- ferogram algorithm, but also does not require absolute equal step to unwrap phase. Instead, the im- proved five-interferogram algorithm only needs measuring phase shifting. Based on the improved al- gorithm, we have developed a novel interferometer with special etalon, and the cavity length of this etalon can be changed by pressure from vertical direction to realize phase shifting. The accuracy of this interferometer is better than 3 nm and can be improved in future research.展开更多
文摘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.
文摘The accuracy of solid density primary standard is decided mainly by the accuracy of the diameter measurement of silicon sphere. With traditional five-interferogram algorithm to unwrap phase for di- ameter measurement, the phase steps should be equal to π/2 exactly, but this is almost impossible to achieve in nanometer positioning technique. In order to overcome this defect, we have derived an im- proved five-interferogram algorithm, which not only keeps the high accuracy of traditional five-inter- ferogram algorithm, but also does not require absolute equal step to unwrap phase. Instead, the im- proved five-interferogram algorithm only needs measuring phase shifting. Based on the improved al- gorithm, we have developed a novel interferometer with special etalon, and the cavity length of this etalon can be changed by pressure from vertical direction to realize phase shifting. The accuracy of this interferometer is better than 3 nm and can be improved in future research.
