Compression of silver in a diamond anvil cell: Pressure dependences of strength and grain size from X-ray diffraction data

Abstract

a b s t r a c tTwo silver samples, coarse grained (c-Ag, grain size 300 7 30 nm) and nanocrystalline (n-Ag, grain size 557 6 nm), are compressed in a diamond anvil cell in separate experiments. The pressure is increased in steps of $ 3 GPa and the diffraction pattern recorded at each pressure. The grain size and compressive strength are determined from the analysis of the diffraction line-widths. The grain size of c-Ag decreases rapidly from 300 7 30 nm at ambient pressure to 40 7 8 nm at 15 GPa, and then gradually to 20 7 3 nm at 40 GPa. After pressure release to ambient condition, the grain size is 25 7 4 nm. The strength at ambient pressure is 0.18 70.05 GPa and increases to 1.07 0.3 GPa at 40 GPa. The grain size of n-Ag decreases from 55 7 6 nm at ambient pressure to 17 7 4 nm at 15 GPa and to 14 7 3 nm at 55 GPa. After release of pressure to ambient condition, the grain size is 50 7 7 nm. The strength increases from 0.51 70.07 GPa at ambient pressure to 3.5 7 0.4 GPa at 55 GPa. The strength is found to vary as the inverse of the square-root of the grain size. The results of the present measurements agree well with the grain-size dependence of strength derived from the hardness versus grain size data at ambient pressure available in the literature.

The effect of crystallite size and stress condition on the equation of state of nanocrystalline MgO

“…10 2p max denotes the difference between the maximum and minimum stress applied to the crystallites. 10,11,22 A previous high-pressure x-ray diffraction study 13 suggests that 2p max derived from Eq. (1) is a reliable measure of compressive strength r. This conclusion was based on the good agreement between the compressive strength of gold derived by applying Eq.…”

“…However, most of these studies were conducted under strongly nonhydrostatic conditions to also reveal the interplay between crystallite size and compressive strength. [10][11][12][13] Unfortunately, these experiments are not well suited to quantify any crystallite-size effect on the elastic compressibility 11,14 and controversial results are reported in the literature. Some studies suggest that the compressibility of a nanocrystalline material significantly differs from its bulk counterpart, 4,8,9 whereas others do not observe any change.…”