Ultrasonic Treatment of Acid-Washed Diamond Powder Surface

Surface groups were evaluated to clarify the effects of sonochemical reactions on acid-washed diamond powder (5–12 μm) treated with high power ultrasound (18 W·cm−2) at 28 kHz in water under three different gas bubbling conditions; argon, oxygen and no bubbling gas. The raw and modified powder surfaces were analyzed by diffused reflectance infrared Fourier transform (DRIFT) spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The results show that ultrasound can modify the surface of acid-washed diamond. Active oxygen species, were formed during the sonochemical treatment, reacted with the diamond surface. DRIFT results show that ether (C–O–C), carbonyl (C=O) and small amounts of peroxy (C–O–O–C) functional groups were formed on the diamond surface after the ultrasonic treatment. XPS analysis confirmed that oxygen is bonded to the diamond surface carbon after the ultrasonic treatment. There is good agreement between DRIFT and XPS results, showing that using argon as bubbling gas produces the highest relative surface oxygen content on the acid-washed diamond surface. Argon gas as monoatomic gas has higher effects in diamond surface modification by ultrasonic treatment than oxygen even for oxidation reaction, due to higher γ (the ratio of the isobaric to isochoric heat capacities) for monoatomic gases and low thermal conductivity.