Improved Adherence Strength between Diamond Grains and Electrolytic Nickel Bonds by Carbon Nanotube Coatings

概要

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New coating methods were proposed to improve the adherence strength between diamond grains and electrolytic nickel bonds on electroplating diamond tools. Diamond grains covered by nested carbon nanotubes (CNTs) were constructed using self-assembly techniques. The grains were first amino-functionalized by silane coupling or photochemical UV treatment. Acid-treated CNTs adsorbed automatically onto amino-terminated grains in N,N-dimethylformamide (DMF) solution by amino-CNT interactions. Subsequent drying and readsorption deposited CNT coatings onto the grains by CNT-CNT interactions due to van der Waals forces. Scanning electron microscope observations indicated that the thickness of CNT coatings on photochemical UV-treated grains was more uniform than that of coatings on grains treated by silane coupling. The adherence strength between the grain and electrolytic nickel bonds was evaluated by shear tests. The adherence strength of the CNT-coated grains was 200-250% of that of the uncoated grains. The photochemical UV treatment was more effective than silane coupling for improving adherence strength. It was surmised that this was due to the uniform thickness of the CNT coatings and the absence of high molecular weight layers contained in the silane coupling agents between CNTs and diamond grains.