X-ray diffraction of electrodeposited nanocrystalline Ni under high-pressure

We studied the compressibility of monolithic fully-dense electrodeposited nanocrystalline Ni (29 nm grain size) under both quasi-hydrostatic and non-hydrostatic conditions up to a nominal pressure of 50 GPa using angle-dispersive x-ray diffraction. We obtained an equation of state consistently and unambiguously from each measured reflection. The apparent bulk modulus measured under non-hydrostatic conditions is larger than that of the corresponding coarse grained-material under either type of compression, but is nearly the same when measured under quasi-hydrostatic conditions. Our results suggest that the strength, but not the bulk modulus, of 29 nm nanocrystalline Ni is enhanced relative to its coarse-grained counterparts.