Publication: Color enhancement of natural type la diamond using a neutron-irradiation and annealing method
Issued Date
2009-01-01
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ISSN
00755192
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2-s2.0-60849099072
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Mahidol University
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SCOPUS
Bibliographic Citation
Kasetsart Journal - Natural Science. Vol.43, No.1 (2009), 216-229
Suggested Citation
Siwaporn Sahavat, Areeratt Kornduangkaeo, Kanphot Thongcham, Siwaporn Meejoo, Wiwat Wongkokua, Suree Likittachai Color enhancement of natural type la diamond using a neutron-irradiation and annealing method. Kasetsart Journal - Natural Science. Vol.43, No.1 (2009), 216-229. Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/27073
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Title
Color enhancement of natural type la diamond using a neutron-irradiation and annealing method
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Abstract
Color in diamonds arises from defects or impurities such as nitrogen, boron or a lattice vacancy. Therefore, suitable types and quantities of defects will assist in creating the most desirable color in a diamond. In this research, ESR spectroscopy was used to find the optimal annealing temperature for color changing in a neutron-irradiated type la diamond. It was found that negative vacancies (V) became mobile above 600°C and were completely trapped by nitrogen to form color centers at 750°C. Therefore, the optimal temperature for color treatment of irradiated diamonds was 750°C. After annealing, yellow diamond was obtained. The optimal fluence of neutron irradiation to produce green diamond was then determined. This research showed that neutron irradiation could turn brown diamond into green diamond with the shading dependent on the fluence of irradiation. The optimal fluence to obtain green diamond was 1.58×1016n/cm2, while at higher levels the diamond became opaque. After annealing at approximately 750°C, irradiated diamond turned into yellow diamond. A higher fluence of neutron irradiation provided a relatively dark yellow color after annealing. The pale or dark shade of enhanced yellow diamond seemed to be independent of the annealing time.