Measurement of inorganic particle size using dynamic light scattering method.

We would like to introduce a case of particle size measurement of positive electrode active materials using laser diffraction conducted by our company. In air or liquid, laser light is irradiated onto the particles, and the angular dependence of the intensity of the light scattered by the particles is measured. By measuring the angular dependence of the scattered light intensity, the particle size distribution (particle size distribution) is calculated from the data. Using commercially available reagents as samples, measurements were conducted in a dry state without dispersing in a solvent. The particle size measurement results for NMC oxide showed a monodisperse state with particle sizes below several tens of micrometers, and the median diameter was calculated to be 12 micrometers.

Dynamic light scattering allows for the measurement of particle size and size distribution of nanoparticles dispersed in a liquid without separating the particles. Here, we present examples of particle size measurement for silica and alumina particles in an aqueous medium. Particles in a solution exhibit Brownian motion that depends on their size, and the fluctuations in the scattered light caused by illuminating the particles are also size-dependent. By observing and analyzing these fluctuations, we can determine the particle size and size distribution. [Alumina Measurement Results and Discussion] - As alumina approaches neutrality from a strongly alkaline condition, it nears its isoelectric point. - The surface charge of the particles decreases. - The repulsion between particles diminishes. - It can be inferred that particle aggregation is occurring. [Silica Measurement Results and Discussion] - It is believed that the isoelectric point is on the strongly acidic side. - In the pH range of 3 to 10, particle aggregation does not occur. - Particle size is maintained below 50 nm.