Abstract
Sub-micron sized grains rapidly depletes due to dust growth in realistic weakly turbulent disks if dust disruption is not taken into account. This depletion of sub-micron sized grains makes the 10-micron silicate feature disapear in the model SED, which is inconsistent with disk observations. The collisional disruption of grains may produce sub-micron sized grains. In the present study, we propose the effect of ice evaporation as an alternative mechanism producing sufficient sub-micron grains. The ice component in grains evaporates at the disk surface because of its high temperature compared with the disk interior. Then, grains break up into silicate monomers. When the silicate monomers go back into the disk interior,H2O gas condenses onto the monomers and icy mantle forms.After that, such monomers grow though mutual collisions but they beak up again when they go up to the surface layer. This break-up mechanism would also have an important effect on the disk temperature and cofiguration as well as the 10-micron silicate feature.
