แบบจำลองของการปรับปรุงคุณภาพพลอยคอรันดัมโดยใช้เทคนิคลำไอออน

Abstract

A gemstone treatment has been used to improve quality of a gemstone, and hence to increase the price of the gemstone. Several types of gemstone treatments include heat treatment, bleaching treatment, radiation treatment, and the recently developed ion beam treatment. When the ion beam technique is performed on a gemstone, molecules of a gas have been released and activated to a radical stage, i.e., ions. These radical ions are accelerated and hit the gemstone. The physical impact of these ions on the gemstone provides the treatment effect. Corundum is one the most expensive gemstones in today’s market. Hence, the corundum gemstone quality improvement via the ion beam technique is explored in this study. Past experiences have indicated that all corundum cannot be improved to reach the same level of quality. Sometimes, the treatment on a corundum can propagate micro cracks into larger cracks and devalue the corundum. An important research question is to find out which corundum should undergo the ion beam treatment and which one should be left out. The most important quality improvement of our interests is the color change. In this study, the colors of a corundum before and after the ion beam treatment have been measured. Other various available physical parameters of the corundum have also been recorded to find out the correlation between these parameters and the color change of the corundum. Specifically, the color changes in the corundum were expressed as functions of these parameters. The mathematical models were represented in the 1st, 2nd, and 3rd order polynomials. The estimation of color changes in the corundum with the 3rd order polynomial provided the most accurate result. The accuracy was measured against the root mean square error with the Leave-one-out cross validation technique. The computational results have shown that initial color of the corundum dictated by molecules such as Ferrous Oxide (FeO) and Chromium Oxide (Cr2O3) have the strongest influences on the corundum’s color changes after the ion beam treatment.