Ⅰa型褐色金刚石高温高压改色研究进展

Research Progress in Color Treatment of Ⅰa Type Brown Diamond under High Temperature and High Pressure Conditions

Ⅰa型金刚石是世界上最重要的金刚石种类,约占金刚石总量的98%。利用大腔体压机通过优化温度、压力和时间等因素改善工业用途的Ⅰa型褐色金刚石的体色,是提高其经济价值并满足日益加剧的彩色金刚石市场需求的重要技术手段。但由于受金刚石原料的来源及实验技术条件的限制导致国内高温高压环境下对褐色金刚石的改色处理进展缓慢,并且改色后的金刚石很难达到宝石级别。本文对自20世纪60年代以来国内外对Ⅰa型金刚石高温高压(HTHP)改色处理的研究及所取得的成果进行了总结。已有的研究显示,在伴有塑性变形的基础上,不同结构的杂质氮是主要的致色元素。根据高温高压环境下Ⅰa型褐色金刚石内部杂质氮反应原理以及动力学机理,提出只要设计合理的样品组装方式以及恰当的改色处理所需的温压条件,我国普遍使用的六面顶压机同样具备对Ⅰa型褐色金刚石进行商业化改色处理的潜力。

Type Ⅰa diamonds are the most important diamonds in the world, accounting for approximate 98% of the natural diamonds. The body color of type I a brown diamonds can be enhanced through optimizing the operational factors of large-volume press such as temperature, pressure and time. Thus, high temperature and high pressure （HTHP） treatment is an important technical approach for obtaining colored diamonds to increase their economic value and meet the needs of the market. However, only slow progress has been made in the HTHP research of brown diamonds in China, because of the limited sources and experimental conditions. Few diamonds of type Ⅰa can reach the gem grade after HTHP treatment. In this paper, the domestic and international achievements of type Ⅰa diamonds under HTHP treatment are reviewed since the 1960s. Previous researches showed that the plastic deformation and the different structure of nitrogen impurity in diamonds are the major factors affecting colour alteration process of the type Ⅰa diamonds. According to the reaction principle and kinetic mechanism of intemal nitrogen impurity in the type Ⅰa diamonds under HTHP conditions, with reasonable design for assembly and proper temperature-pressure conditions, the widely used cubic-anvil apparatus in china should have the potential to improve the color of type Ⅰa diamonds.