การสร้างและการหาลักษณะเฉพาะของเครื่องไนโตรเจนไมโครเวฟ พลาสมาสำหรับปรับปรุงคุณภาพหินอัญมณี

Abstract

Low-cost gemstones treatment for the better quality and increasing market price has been interested since high-cost gemstones are currently rare. Nowadays, gemstones have been improved to be better quality by many treatment processes such as heat, irradiation, dyeing, diffusion, oil filling, assembly, cavity filling, coating, and bleaching. In this thesis, we study and investigate a nitrogen microwave plasma machine for treatment 4 types of gemstones including Rubellite, Aquamarine, Emerald and Tanzanite. The nitrogen plasma was introduced by nitrogen gas stimulated via using microwave. For the plasma characterization, the nitrogen plasma is pink-orange color. The temperature of tested material at the center of plasma was approximately around 400-420 C and the temperature decreases when the distance further from the plasma center. For the gemstone treatment by the nitrogen plasma, the color intensity of Rubellite decreased and turn to be naturally lighter pink while the optimal pressure of the system was set at 1.1 torr. The same behavior was also presented in Aquamarine and Tanzanite. The color tends to reduce light yellow and become to light bluish purple after Aquamarine and Tanzanite was treated by the nitrogen plasma, respectively. Meanwhile, the nitrogen plasma cannot affect to color of Emerald due to it was still naturally green color after plasma treatment. Overall, the gemstone treatment by using the nitrogen plasma is an alternative process which can change the intensive color of gemstones from dark color to lighter color.