Finnie S, Prasad K V, Sheen D B, Sherwood J N
Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, Scotland, UK.
Pharm Res. 2001 May;18(5):674-81. doi: 10.1023/a:1011093612868.
To study the mechanical behaviour of paracetamol single crystals.
Microhardness indentation techniques were used to study the hardness anisotropy of paracetamol. Solvent etching technique was used to define the range of plastic deformation and the orientation of the dislocation lines. The orientation dependence of Knoop hardness on the (001), (110) and (201) surfaces was compared with calculated values of the Effective Resolved Shear Stress (ERSS) for plastic deformation by specific dislocation types.
The principal habit faces of single crystals using both Vickers and Knoop indenters showed a range of hardness from 235 to 456 MPa depending on the type of indenter used and its orientation on the surface. Solvent etching of the plastically deformed region of the crystal around the Vickers/Knoop indentations confirmed that the slip plane was (010). ERSS analysis suggested that the deformation occurred by the slip of dislocations of the types (010)[001] and (010)[100]. Crystals doped with 0.08-0.8 w/w% p-acetoxyacetanilide showed hardness values similar to the pure material.
The low number of distinct dislocation slip systems (two) is characteristic of a brittle material and is consistent with the observation that paracetamol will tolerate only deformations of 1 part in 10(6) before fracture.
研究对乙酰氨基酚单晶的力学行为。
采用显微硬度压痕技术研究对乙酰氨基酚的硬度各向异性。利用溶剂蚀刻技术确定塑性变形范围和位错线的取向。将努氏硬度在（001）、（110）和（201）表面上的取向依赖性与特定位错类型塑性变形的有效分解切应力（ERSS）计算值进行比较。
使用维氏和努氏压头时，单晶的主要习性面显示出235至456兆帕的硬度范围，这取决于所使用压头的类型及其在表面上的取向。对维氏/努氏压痕周围晶体的塑性变形区域进行溶剂蚀刻，证实滑移面为（010）。ERSS分析表明，变形是由（010）[001]和（010）[100]类型的位错滑移引起的。掺杂0.08 - 0.8 w/w%对乙酰氧基乙酰苯胺的晶体显示出与纯材料相似的硬度值。
明显的位错滑移系统数量少（两个）是脆性材料的特征，这与对乙酰氨基酚在断裂前仅能承受10⁻⁶分之一变形的观察结果一致。
