Peeling of Nano-Particle (PNP) process for localized material removing on a silicon carbide (SiC) surface by controlling of magnetic field

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For the purpose of localized removing the material on a SiC surface by the Peeling of Nano-Particle (PNP) process, the controllability of the particles and the contact phenomenon on the surface were confirmed.Optical systems were developed applying an evanescent field microscopy for directly observing only the particle approaching the surface during generating a magnetic field under the surface. In this experiment, φ50-100 nm sized Fe3O4 particles in KOH solution (pH10 value) could evidently be magnetically pulled in and pulled out from the SiC surface. During generating the pulling magnetic field, we found that the particles were pulled close to the surface with decreased Brownian motion ranges that would be limited by the DLVO force. However, the particles would not yet completely contact the SiC surface due to the against electric double layer, which relates to the height z of the particle on the SiC surface. The height z of the particle on the surface was measured by applying the multi-wavelength evanescent fields. By our measuring method, the particles would be pulled close to the surface at the height z≒20-25 nm by the pulling magnetic field ≒40 mT, which calculated the pulling magnetic force ≒ 10-30 fN. To let those magnetic particles contact on the SiC surface to be peeled, the magnetic field should be stronger 1.5-2 times (60-80 mT) for generating the pulling magnetic force ≒40-80 fN. This measuring action forces technique by the PNP process would be an index to explain the material removal mechanism to other hard material machining processes.