Mechanochemical grinding with aluminium-coated nickel and diamond mixed abrasive vitrified bond wheel for reducing anisotropy in (100) surface single-crystal diamond processing

Abstract

While single-crystal diamond is a promising wide-bandgap semiconductor material, it is also the hardest material in nature and exhibits remarkable anisotropy, presenting a challenge for high-quality and efficient processing. To address this issue, this article introduces a method that utilises aluminium-coated nickel and diamond mixed abrasive vitrified bond grinding wheels for a mechanicochemical grinding process to reduce the anisotropic removal of diamond. Different cutting depths, abrasive ratios, grinding directions, and linear velocities were employed in the processing, with the material-removal mechanism studied through morphological characterisation, elemental content, and other detection methods. The experiment revealed that the catalytic effect of nickel metal occurred along the (111) crystal plane of the diamond. This catalytic process involves a transition from sp3 diamond to amorphous carbon, followed by graphitisation. The spin-rotating mechanicochemical grinding process mainly involves plastic removal in the soft direction and coupled chemical and mechanical removal in the hard direction. Employing this method reduced the surface roughness of the 7 × 7 mm as-grown crystal to Ra 0.467 nm, with a material removal rate of 4.73 μm/h, achieving a nearly damage-free machining surface.