Certification of NIST SRM 1962: 3 μm Diameter Polystyrene Spheres

Area of Science:

• Materials Science
• Metrology
• Nanotechnology

Background:

• Accurate particle size characterization is crucial for various scientific and industrial applications.
• Standard Reference Materials (SRMs) provide essential traceability for measurements.
• Polystyrene spheres are commonly used as calibration standards due to their stability and uniformity.

Purpose of the Study:

• To certify NIST Standard Reference Material (SRM) 1962 for particle diameter.
• To establish a reliable standard for the calibration of particle sizing instruments.
• To provide a well-characterized material for inter-laboratory comparisons.

Main Methods:

• Certification involved two primary calibration techniques: optical microscopy and electron microscopy.
• Optical microscopy involved measuring a large number of spheres (4600) to determine the mean diameter and size distribution.
• Electron microscopy provided high-resolution measurements on a smaller subset of spheres (120).

Main Results:

• Optical microscopy yielded a mean diameter of 3.003 μm with a standard deviation of 0.020 μm.
• Electron microscopy provided a mean diameter of 3.001 μm.
• The certified value for SRM 1962 is 3.003 μm, with a maximum uncertainty of 0.016 μm and a standard deviation of 0.020 μm.

Conclusions:

• NIST SRM 1962 is a reliable standard for particle diameter measurements in the 3 μm range.
• The combined results from optical and electron microscopy ensure high accuracy and traceability.
• This certified material supports advancements in fields requiring precise particle size metrology.