EFFECT OF ROUGH DIAMOND POLISHING ON THE CARBON CENTERED RADICALS

Diamonds contain stable carbon centered radicals in small concentrations (in the level of ~1x10¹² spins /mg). These species can help in elucidating the structure of nitrogen atoms as contaminants in the diamond crystal. However, if the diamond is exposed to high temperatures it may affect the concentration and structure of the carbon centered radicals.

Every diamond is exposed to high temperature during the process of diamonds polishing because of the friction in the process. The temperature is increased appreciably and the diamond emits light in the visible range and turns to orange color which is due to its behavior as a black body. The orange wavelength in the visible is typical to temperature of 900^oC or higher. Other processes in which diamonds are exposed to high temperatures are thermal treatments of treated color enhanced diamonds or the HPHT process in which bleaching of brown color due to plastic deformation is achieved.

The aim of the study is to examine how thermal treatment vs polishing influences the paramagnetic centers in the diamond. In order to establish this, four diamonds were studied: two diamonds underwent a polishing process and the other two diamonds underwent thermal treatment at 650 °C and then at 1,000 °C. The diamonds were measured pre and post treatments by EPR, FTIR, fluorescence and visual appearance.

The results of the study showed that the polishing process affects the concentration and possibly the structure of the paramagnetic centers. In addition, the thermal treatments showed a smaller decrease in the concentration of the paramagnetic center's vs the polished, but the thermal treatment seems to affect more the depth of the diamond and the overall arrangement of nitrogen atoms in the crystal.