Comparison of Two Measurement Methods for Scattering and Absorption Coefficients in Boron Carbide Nanodispersions

Nanoparticles suspended in a liquid alter the properties of the base liquid, expanding its fields of application. Nanodispersions can have several applications in solar energy, including serving as liquid sunlight absorbers, acting as optical filters in optics, or functioning as heat transfer fluids in solar thermal applications. However, for a precise evaluation of their use in a specific field, their properties must be carefully assessed. In this work, we use two different methods for the determination of the optical scattering and absorption coefficients of a nanodispersion of boron carbide (B₄C), and we compare the obtained results. Monochromatic measurements are performed at 635, 685, 730, and 830 nm, utilizing a technique that relies on the theory of optical scattering in an infinite medium. They are compared with spectrally resolved measurements of ballistic and total transmittance in the wavelength range of 400-850 nm, obtained using a spectrophotometer with an integrating sphere. The two methods are consistent and give results in good agreement. We also found that the mean radius of nanoparticles is higher than expected, confirming the non-negligible scattering.