Abnormal compression behavior with unexpected negative linear compressibility of <i>γ</i>-AlOOH nanotubes

Due to their unique compositional, structural, and morphological characteristics, hydrogen bonded two-dimensional (2D) layered materials and their one-dimensional tubular derivatives are endowed with great importance in the fields of both fundamental sciences and potential applications. In this work, γ-AlOOH nanotubes have been synthesized via a template-free one-step solvothermal alcoholysis method. The pressure response of the samples under static compression is investigated by in situ high-pressure angle dispersive synchrotron x-ray diffraction techniques. The results indicate that the compression behavior of nanotubes is different from those of its counterparts in the bulk and the nanoflake form. At pressures below 9.4 GPa, the unit-cell parameters a, b, and c decrease monotonously with pressure. In the pressure range of 10.6–19.9 GPa, an unexpected negative linear compressibility along the c-axis is observed experimentally in the compression behavior. When the high pressure is gradually released, it is evidenced that the compression of the prepared γ-AlOOH nanotubes is irreversible. The observed abnormal compression behavior and the unexpected negative linear compressibility may be explained by inflation associated with incorporation of the pressure transmitting medium within the interior cavity of the tubular nanostructures. Such a counter-intuitive phenomenon may find potential applications under high pressures.