Dimensional measurement of TiO₂ (Nano) particles by SAXS and SEM in powder form

The market for nano-additive materials has been growing exponentially since 2012, with almost 5040 consumer products containing nanoparticles in 2021. In parallel, the increasing recommendations, definitions and legislations underline the need for traceability of manufactured nanoparticles and for methods able to identify and quantify the "nano" dimensional character in manufactured product. From a multi-technic approach, this paper aims to compare the mesurands extracted from SAXS/BET (specific surface area) and SEM (diameter equivalent to a projected surface area) on different TiO₂ powder issued from referenced, synthesized materials, raw materials (additives) and extracted materials from manufactured products. The influence of various parameters such as the anisotropic factor, the interaction between particles, the size distribution and the extraction steps are discussed to illustrate their impact on the diameter values issued from two different measurands. These results illustrate the difficulties in (nano)particles characterization. SEM and SAXS are complementary techniques depending on the level of dimensional characterization required.