Among candidates for chemical hydrogen storage in PEM fuel cell automotive applications, ammonia borane (AB, NH3BH3) is considered to be one of the most promising materials due to its high hydrogen content of 14-16 wt % and high volumetric density of similar to 146 g H-2/liter. To utilize the existing infrastructure, a fluid-phase hydrogen storage material is attractive, and thus, we investigated the materials' properties of AB in liquid carriers for a chemical hydrogen storage slurry system. Slurries composed of AB and high-boiling-point liquids were prepared by mechanical milling and sonication in order to obtain stable and fluidic properties. Kinetics of the H-2 release reactions of the AB slurry and neat AB was studied using a volumetric gas buret. Viscometry and microscopy were employed to further characterize the engineering properties of the slurries. Using a tip-sonication method, we have produced AB/silicone fluid slurries at solid loadings up to 40 wt % (6.5 wt % H-2) with viscosities less than 500 cP at 25 degrees C.