Nanocrystalline diamond films fabricated by sol–gel technique

This study describes nanocrystalline diamond coating using sol–gel technique as an easy coating technique for nanocrystalline diamond films. To make a nanodiamond sol for coating, diamond nanoparticles (<10 nm) synthesized by a detonation method are put into distilled water and are dispersed by an ultrasonic wave, and then are mechanically milled with zirconia balls. The viscosity of the prepared nanodiamond sol increases with the content of the added diamond nanoparticles. The prepared nanodiamond sol is spin-coated at 3000 rpm on a quartz substrate. TEM observation shows that the obtained film consisting of the deposited diamond nanoparticles is approximately 500 nm in thickness. The obtained films are heated at <873 K in air atmosphere. The results of the XRD and Raman analysis indicate that all the fabricated nanocrystalline diamond films have the diamond (sp3) and amorphous carbon (sp2) structures. The indentation measurements are made for the nanocrystalline diamond films fabricated, and the indentation hardness of the film heated at 573 K indicates the maximum value of 367 MPa. This technique can fabricate nanocrystalline diamond films easily at a much lower processing temperature than the processing temperature of conventional diamond coating.