  The temperature dependence of the dynamics of water inside microporous
activated carbon fibers (ACF) is investigated by means of incoherent elastic
and quasi- elastic neutron scattering techniques. The aim is to evaluate the
effect of increasing pore size on the water dynamics in these primarily
hydrophobic slit-shaped channels. Using two different micropore sizes (\sim 12
and 18 {\AA}, denoted respectively ACF-10 and ACF-20), a clear suppression of
the mobility of the water molecules is observed as the pore gap or temperature
decreases. This suppression is accompanied by a systematic dependence of the
average translational diffusion coefficient Dr and relaxation time <{\tau}_0>
of the restricted water on pore size and temperature. The observed Dr values
are tested against a proposed scaling law, in which the translational diffusion
coefficient Dr of water within a nanoporous matrix was found to depend solely
on two single parameters, a temperature independent translational diffusion
coefficient Dc associated with the water bound to the pore walls and the ratio
{\theta} of this strictly confined water to the total water inside the pore,
yielding unique characteristic parameters for water transport in these carbon
channels across the investigated temperature range.
