Liu Ran, Liu Bo, Li Quan-Jun, Liu Bing-Bing
State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China.
Nanomaterials (Basel). 2020 Aug 21;10(9):1640. doi: 10.3390/nano10091640.
An in situ high-pressure X-ray diffraction study was performed on AgS nanosheets, with an average lateral size of 29 nm and a relatively thin thickness. Based on the experimental data, we demonstrated that under high pressure, the samples experienced two different high-pressure structural phase transitions up to 29.4 GPa: from monoclinic 2/ structure (phase I, -AgS) to orthorhombic 222 structure (phase II) at 8.9 GPa and then to monoclinic 2/ structure (phase III) at 12.4 GPa. The critical phase transition pressures for phase II and phase III are approximately 2-3 GPa higher than that of 30 nm AgS nanoparticles and bulk materials. Additionally, phase III was stable up to the highest pressure of 29.4 GPa. Bulk moduli of AgS nanosheets were obtained as 73(6) GPa for phase I and 141(4) GPa for phase III, which indicate that the samples are more difficult to compress than their bulk counterparts and some other reported AgS nanoparticles. Further analysis suggested that the nanosize effect arising from the smaller thickness of AgS nanosheets restricts the relative position slip of the interlayer atoms during the compression, which leads to the enhancing of phase stabilities and the elevating of bulk moduli.
对平均横向尺寸为29纳米且厚度相对较薄的AgS纳米片进行了原位高压X射线衍射研究。基于实验数据，我们证明在高压下，样品在高达29.4吉帕的压力下经历了两种不同的高压结构相变：在8.9吉帕时从单斜2/结构（相I，-AgS）转变为正交222结构（相II），然后在12.4吉帕时转变为单斜2/结构（相III）。相II和相III的临界相变压力比30纳米AgS纳米颗粒和块状材料的临界相变压力高约2 - 3吉帕。此外，相III在高达29.4吉帕的最高压力下是稳定的。AgS纳米片的体模量在相I时为73(6)吉帕，在相III时为141(4)吉帕，这表明样品比其块状对应物和其他一些报道的AgS纳米颗粒更难压缩。进一步分析表明，AgS纳米片较小的厚度所产生的纳米尺寸效应限制了压缩过程中层间原子的相对位置滑移，这导致了相稳定性的增强和体模量的提高。
