Papers by Keyword: Nanoscratch

Abstract: Precision grinding of a multilayered thin film solar panel is recognized as the bottleneck in its manufacturing process. A primary challenge is the significantly high stress induced at the thin film interfaces during grinding. Such stress concentration can result in interfacial delamination between two dissimilar materials and thus device malfunction. This study used a finite element modelling analysis to understand the stress evolution of the multilayer thin film structure during a single grit scratching that simulates the individual interaction between abrasive grits and work materials in grinding. The results demonstrated that significant tensile and shear stresses were formed at interfaces during scratching, which could be traced back to the experimental evidence obtained from the nanoscratching process. The maximum stresses undertaken by the interfaces were simulated.

Abstract: The deformation and removal mechanism of a multilayered thin film structure involved in nanoscratching and diamond lapping processes were investigated. The results obtained from the two processes were compared, in terms of deformation characteristics and surface finish. It was found that both nanoscratching and lapping demonstrated similar characteristics. This work provides insight into the deformation and removal of a thin film multilayered structure under mechanical loading, and thus the outcome is of value for developing the efficient machining process for such structures.

Abstract: The automatic scratch geometrical parameters analysis algorithms based on the images obtained by scanning probe microscopy have been developed. We provide a description of the technique to determine the contact area and the scratch volume with and without account of the pile-ups. The developed algorithms are applied to measure the dynamic hardness by sclerometry on the submicron and nanometer scale.

Abstract: Derived the approximate relationship between minimum cutting thickness and tip radius, ratio of vertical load and shear force, friction coefficient between tip and sample. Wire was being processed by changing the load size. The critical load of chip formation and machining thickness were found from atomic force scan picture. Contrast tests were done by transforming the specimen. The experimental results are basically consistent with the derived values.

Abstract: The failure characteristics of silicon nitride thin film deposited on GaAs substrate were investigated by use of nanoscratch. It was found that the film started to failvia delamination or buckling, which should beattributed to interfacial shear stress. The cracks were then formed and propagated around the edge of the delaminated film before it was chipped away by the moving tip. A normal load of 6.5 mN, corresponding to a depth of 150 nm, was found to be the critical threshold for theinterfacial failure. The fracture energy release rateof the film/substrate interface, or the work of adhesion, was calculated as 2.90 J/m2.

Abstract: This paper reports our recent results on the nanoindentation and nanoscratch of LiTaO3 single crystals. The elastic modulus and hardness of LiTaO3 obtained from nanoindentation were 251±3 GPa and 12.6±0.6 GPa, respectively. During indenting, pop-in events occurred when indentation load was in the range from 305 to 640 μN. Incipient kink bands (IKBs) were believed to be responsible for the pop-ins. Nanoscratching showed that there existed a threshold normal load of 2.5 mN, above which cracks were generated and the material removal was in the brittle regime. The knowledge gained is valuable to the design of an effective machining process for LiTaO3 crystals.

Abstract: Nanoscratch tests showing clear ploughing behavior and stable chip formation was conducted to investigate the influence of friction coefficient on the minimum thickness of cut. A theoretical model accounting for the minimum thickness of cut is used to analyze the effects of the friction coefficient and force ratio. Results show that the minimum thickness of cut is strongly dependent on both friction coefficient and force ratio. Theoretical minimum thickness of cut can be obtained when adhesion friction plays a dominant role in the cutting process. Appropriate adjustments of processing parameters are hereby suggested to result in stable micro-machining process without ploughing, not only forming fine-thin continuous chip, but also achieving high surface quality. The role of friction coefficient on the minimum thickness of cut with δ (cutting depth/edge radius) is also discussed.

Abstract: Chemical tempered glasses were prepared using glass slides as substrate and KNO₃ as melting agent by ion-exchange during 2h, 4h, 6h at 430°C,450°C and 500°C respectively. The surface composition of the glasses was analyzed by energy dispersive spectrometer (EDS), the mechanical properties and wear resistance were characterized by nanoindentation/nanoscratch tests. The results indicate that the ion- exchange method can be a good way to increase the strength and improve wear resistance of Na-Ca-Si glass. The chemical tempering has an optimal treating temperature and time.

Abstract: The effect of microstructure of cemented tungsten carbide materials on their mechanical properties and wear characteristics was investigated using nanoindentation and nanoscratch methods. The results indicated that the variation in grain size insignificantly affected the hardness, elastic modulus and friction coefficient of the work materials, but considerably influenced their removal rates. The carbide with coarser grains exhibited a much higher removal rate was obtained during scratching.

Abstract: This paper reports the effect of nanogrinding conditions on the formation of subsurface structures of monocrystalline silicon (100) substrates. It was found that the amorphization and the transformation of high pressure phases were related to the grit depth of cut employed in nanogrinding. The formation mechanisms were found to be different from those previously reported from the nanoindentation studies.