Refractory nanoporous materials with high porosity could serve as efficient catchers for the fast release of unstable nuclei in rare isotope accelerators. The unique, self-limiting capability of atomic layer deposition (ALD) offers an attractive synthetic route for fabricating refractory nanoporous materials. Here we demonstrated a method using high surface area silica aerogel monoliths as templates for the growth of conformal thin films by ALD. Static mode ALD of W using Si2H6 and WF6 at 200oC was employed to coat the inner surfaces of the low density, nanoporous silica aerogel monoliths. To facilitate nucleation and improve adhesion of the ALD W, the aerogels were coated with 2Å Al2O3 using alternating exposures to Al(CH3)3 and H2O prior to the W ALD. After coating, scanning electron microscopy revealed a porous microstructure in which the ALD W completely encapsulates the silica aerogel. The porosity of the aerogels was preserved during the first ~10 W ALD cycles allowing the density to be controlled by adjusting the number of W ALD cycles and values as high as 5 g/cc were obtained. BET surface area measurements revealed a gradual decrease in the surface area of the silica aerogel with increasing numbers of W ALD cycles consistent with a gradual filling of the aerogel voids. Next, we heated the W-coated aerogels to 1500oC in an inert atmosphere and observed that they maintained their integrity and porosity with almost no loss in density. These results are very encouraging for the deployment of these materials as isotope catchers.