DescriptionIn recent years, micro/nanoscale diamond cutting tools shaped by focused ion beam (FIB) has been developed to the deterministic fabrication of micro/nano-structures owing to its unprecedented merits of high throughput, one-step, and highly flexible precision capabilities. However, the exposure of a diamond tool to FIB will result in the implantation of ion source material and the irradiation damage in cutting edges, and thus affect the tool life. In this work, molecular dynamics (MD) simulation has been carried out to study the effects of FIB induced damage on the wear resistance of nanoscale multi-tip diamond tool under different cutting conditions. A novel nanoscale multi-tip diamond tool model was built with the implanted Ga+ and amorphous damaged layer around tool tips. A damage free tool model with the same tool geometry was built as a reference. The wear resistance of the cutting tool was characterized by the total number of defect atoms formed during nanometric cutting of single crystal copper. The results show that the FIB irradiation induced doping and defects significantly degrade the wear resistance of the diamond tool. For the damage free tool cutting, the sp2 bonded carbon atoms were formed and accumulated on the surface layers. However, the sp2 bonded carbon atoms were found both on the surface and the deep inside of tool when using the tool of predefined defects. The implanted gallium atoms were found to move to the tool surface and left vacuums inside diamond tool tip, which would further degrade the wear resistance of the tool. Moreover, the variation of the sp2-bonded carbon atoms against the depth of cut and the cutting speed has been further analysed. The research findings from this study inform the in-depth understanding of tool wear of FIB shaped multi-tip diamond tool observed in previous nanometric cutting experiment.
The results show that the proposed model can effectively track the impulse of each single ion leads to atomic displacements in diamond and finally to a U-shape residual damaged layer at the core irradiation area. The multi-timestep algorithm can increase the computing efficiency by 12 times while still holding high simulation accuracy in terms of the thickness of residual damaged layer and the range of incident gallium distribution. The simulation model was further used to study the ion-induced damage layer in diamond under various beam voltages (5 kV, 8 kV, and 16 kV) and incident angles (0˚, 15˚, 30˚, and 45˚). Less damage range were found under the beam energy of 5 kV with the ion incident angle of 45˚, which indicated that a post ion beam polishing process (low beam energy with large incident angle) would be an effective way in practice to remove/minimise the residual damage layer when shaping the diamond cutting tools.
|Period||30 May 2016|
|Event title||16th International Conference of the European Society for Precision Engineering and Nanotechnology|
|Location||Nottingham, United Kingdom|
|Degree of Recognition||International|