5. Conclusions

In this chapter, the optical properties and radiation stability of titanium dioxide powders before and after modification by nanopowders of various oxide compounds (Al2O3, ZrO2, SiO2, TiO2, ZnO, and MgO) are considered.

The reflectivity of modified powders can both increase, in comparison to the initial powders, and decrease. The reflection coefficient is determined by the grain sizes and, with their decrease, it increases, which occurs when nanopowders are added. The decrease in the reflection coefficient may be due to a large absorption by native point defects in the UV and visible ranges and by chemisorbed gases in the near-IR range of the spectrum, determined by the larger specific surface area of nanopowders.

Modification with nanopowders leads to an increase in the radiation stability of reflective powders, which is determined by the relaxation of electronic excitations on the surface of nanoparticles and by a smaller concentration of absorption centers formed upon irradiation. The maximum effect of increasing radiation stability is achieved by modification by nanopowders with a larger specific surface area and a smaller particle size. An additional factor affecting the increase in radiation stability is the heating during the modification, and the largest effect was obtained at T = 800C.
