Slow neutrons (UCN, VCN, CN) are coherently scattered by nanoparticles that provides a powerful tool for VCN reflectors, for VCN storage in traps, for "quasi-specular" CN reflectors and for cooling VCN. Our recent X-rays measurements had shown that on heating a water nanocluster-gel sample above 4 K in He gas atmosphere, one can observe formation of highly-dispersed ice samples consisting of a mixture of amorphous and cubic ice (Ic), where the inner structure of the sample changes from amorphous to cubic Ic and then to commonly observed hexagonal ice Ih with increasing the temperature from 80 to 200 K. This observation openes up unique opportunities for improving reflecting properties of nano-structured reflectors by replacing diamond nanoparticles (with hardly-removable hydrogen contaminations) to nanoparticles from low-absorbing materials like pure D2 or D20 at reasonably high temperatures. We propose to perform a set of SANS experiments, using our specialized optical cryostat for in-situ preparation of the gel samples, for studies of nanostructured ice samples in the temperature range from 1.6 to 25 K (for deuterium ice) and from 1.6 to 200 K for heavy water ice samples.