Search

Graphical abstract:

Spectroscopic ellipsometry is a powerful technique for determining optical properties of any thin surface. A method for characterizing optical properties of warm asphalt binder using spectroscopic ellipsometry along with associated results has been presented in this paper. Thin films of warm asphalt binders were produced using LEADCAP and Sasobit and characterized using a variable angle spectroscopic ellipsometry. Refractive index and extinction coefficient of each of the samples (original and aged) were extracted from model fitted spectra. Clear variation in refractive index and extinction coefficient was observed among the samples before and after aging. The samples were found to be highly reflective with refractive index ‘n’ in the range 1.55–1.62 and extinction coefficient ‘k’ in the range of 0.01–0.06, both before and after aging. Reflectivity of PG 64-22 with LEADCAP exhibited the highest refractive index and the lowest extinction coefficient in visible wavelength of light among the samples. The results indicated that the highest reflection of visible light can be observed from LEADCAP-modified binder. Cracking properties and absorption coefficient of the binders are observed to have a correlation. The method reported here can be applied to any type of asphalt binder to determine its light absorption and reflection characteristics for a wide range of wavelength.

The broadband optical absorption properties of silicon nanowire films fabricated by electroless metal deposition technique followed by HF/Fe(NO3)3solution-based chemical etching at room temperature on p-type silicon substrates have been measured and we have found higher absorption than that of the solid thin films of equivalent thickness. The observed behavior is effectively explained by light scattering and light trapping, though some of the observed absorption is due to a high density of surface states in the nanowire films. The synthesized structures absorbed more than 82% of incident radiation in case of Cu-deposited silicon nanowires, whereas for Ag it was a maximum of 83%, which is much greater than that of the bulk silicon as they absorbed a maximum of 43% of the radiation.