and size distribution
What is measured?
The measured quantity is the diameter of globular shaped particles and the related number- or volume-weighted size distribution. The quantitative analysis in terms of volume fraction or mass concentration is possible due to scattering intensities being normalized to absolute units.
Range of diameters accessible with SAXS measurements:
- 1 to 300 nm
- Up to 5 µm with the USAXS extension
- Applicable to multimodal distributions
Figure 1. Size distribution of dilute silver nanoparticles in aqueous suspension obtained from SAXS data acquired on the Nano-inXider. The data analysis was performed with XSACT software.
The availability of the scattering intensity in absolute units enables the accurate determination of volume fractions.
The histogram is normalized with respect to the bin size. The size distributions corresponding to two distinct bin definitions can therefore be compared directly.
Cumulated values are displayed to facilitate the readout.
Typical samples for this measurement are:
Dispersions and suspensions
Gels and pastes
Have a look at the following examples:
Methods & standards
Standards & methods used for particle size & size distribution:
- Size determination by Guinier analysis and model fitting
Ref: ISO 17867:2015 – Particle Size Analysis – Small-angle X-ray scattering
- Guinier analysis
Ref: A. Guinier, G. Fournet Small-Angle Scattering of X-rays. John Wiley, New York, 1955
- Expectation Maximization (EM)
Ref: F. Benvenuto, H. Haddar and B. Lantz, SIAM J. Appl. Math., 2016, 76(1), 276-292
XSACT analysis software implements the above methods and standards.
Advantages of SAXS
Why use SAXS for measurement of particle size & size distribution ?
Exceptional resolution power even for smallest nanoparticles and bimodal populations.
Reliable statistical properties due to ensemble averaging.
Minimal sample preparation is required. You can work with a wide range of concentrations and samples, even on opaque suspensions or dry powders. No dilution step is required.
With SAXS, you can do in situ and dynamics studies.
All these measurements are possible directly in your lab.
Smart nanoscale characterization
The Next Generation
(GI-)SAXS/WAXS/USAXS beamline for the laboratory