Growth Of Large High-quality Type â…¡a Diamond Crystals And Research Of The Mechanism Under HPHT

High-quality large diamond crystals have been synthesized by temperature gradient method (TGM) under high pressure and high temperature (HPHT) in China-made cubic anvil high-pressure apparatus in this paper. After ascertaining the stability assembly of the experiments, the new method of the adjusting temperature gradient was put forward. The growth traits of typeⅡa large diamonds, which have been synthesized in the NiMnCo or FeNiCo with the additive of Al or Ti (Cu) as a nitrogen getter on the basis of above works, were researched. The conclusions of the research are as follows:1. As to both assembly whose diameter of the bath areΦ14mm andΦ10mm, the assembly ofΦ10mm has been ascertained to grow typeⅡa large diamonds by the stability of long time under HPHT and the compare of the temperature in the high temperature of the pyrophyllite.2. The new method of the adjusting temperature gradient, which was the use of special shape graphite tube, was put forward firstly on the traditional methods of the adjusting temperature gradient.3. While Al as a nitrogen getter was added into the NiMnCo or FeNiCo. the growth traits of typeⅡa large diamonds in the both alloy solvent were investigated respectively. The decomposition of A1N in the alloy solvent under HPHT was firstly validated then the mechanism of Al for eliminating nitrogen in synthesizing large diamonds was analysed entirely by A1N added into FeNiCo solvent.4. While Ti (Cu) as a nitrogen getter was added into the NiMnCo or FeNiCo. the growth traits of typeⅡa large diamonds in the both alloy solvent were investigated respectively. The colorless high quality typeⅡa large diamond crystal whose size is 4.3mm was synthesized by optimizing the growth process.5. The effect of black micro-crystal graphite on the crystal growth and the producing mechanism of micro-crystal graphite, which was producing in the course of growing typeⅡa large diamonds, have been researched.6. While Ti (Cu) as a nitrogen getter was added into FeNiCo, the high quality typeⅡa large diamond crystals whose size is about 2mm were synthesized by multiple seeds method.