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Growth characteristics of type IIa large single crystal diamond with Ti/Cu as nitrogen getter in FeNi–C system

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Chinese Physics B 2020年第1期29卷 457-462页

作者： Ming-Ming Guo Shang-Sheng Li Mei-Hua Hu Tai-Chao Su Jun-Zuo Wang Guang-Jin Gao Yue You Yuan Nie Henan Key Laboratory of Materials on Deep-Earth Engineering School of Materials Science and EngineeringHenan Polytechnic UniversityJiaozuo 454003China Jiaozuo Engineering Technology Research Center of Advanced Functional Materials Preparation under High Pressure Jiaozuo 454003China

High-quality type IIa large diamond crystals are synthesized with Ti/Cu as nitrogen getter doped in an FeNi–C system at temperature ranging from 1230℃to 1380℃and at pressure 5.3–5.9 GPa by temperature gradient *** ratios of Ti/Cu are added to the Fe Ni–C system to investigate the best ratio for high-quality type IIa ***,the different content of nitrogen getter Ti/Cu(Ti:Cu=4:3)is added to this synthesis system to explore the effect on diamond *** macro and micro morphologies of synthesized diamonds with Ti/Cu added,whose nitrogen concentration is determined by Fourier transform infrared(FTIR),are analyzed by optical microscopy(OM)and scanning electron microscopy(SEM),*** is found that the inclusions in the obtained crystals are minimal when the Ti/Cu ratio is 4:***,the temperature interval for diamond growth becomes narrower when using Ti as the nitrogen ***,the lower edge of the synthesis temperature of type IIa diamond is 25℃higher than that of type Ib *** the increase of the content of Ti/Cu(Ti:Cu=4:3),the color of the synthesized crystals changes from yellow and light yellow to *** the Ti/Cu content is 1.7 wt%,the nitrogen concentration of the crystal is less than 1 *** SEM results show that the synthesized crystals are mainly composed by(111)and(100)surfaces,including(311)surface,when the nitrogen getter is added into the synthesis *** the same time,there are triangular pits and dendritic growth stripes on the crystal *** work will contribute to the further research and development of high-quality type IIa diamond.

关键词： high temperature and high pressure temperature gradient method type IIa diamond

Effects of a carbon convection field on large diamond growth under high-pressure high-temperature conditions

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Chinese Physics B 2012年第9期21卷 525-530页

作者：胡美华李尚升马红安宿太超李小雷胡强贾晓鹏 School of Materials Science and Engineering Henan Polytechnic University State Key Laboratory of Superhard Materials Jilin University

Large diamond crystals were successfully synthesized by a FeNi C system using the temperature gradient method under high-pressure high-temperature conditions. The assembly of the growth cell was improved and the growth process of diamond was investigated. Effects of the symmetry of the carbon convection field around the growing diamond crystal were investigated systematically by adjusting the position of the seed crystal in the melted catalyst/solvent. The results indicate that the morphologies and metal inclusion distributions of the synthetic diamond crystals vary obviously in both symmetric and non-symmetric carbon convection fields with temperature. Moreover, the finite element method was applied to analyze the carbon convection mode of the melted catalyst/solvent around the diamond crystal. This work is helpful for understanding the growth mechanism of diamond.

关键词： diamond high pressure and high temperature temperature gradient method carbonconvection field

Growth of gem-grade nitrogen-doped diamond crystals heavily doped with the addition of Ba(N_3)_2

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Chinese Physics B 2011年第7期20卷 461-465页

作者：黄国锋贾晓鹏李勇胡美华李战厂颜丙敏马红安 National Laboratory of Superhard Materials Jilin University

Additive Ba（N3）2 as a source of nitrogen is heavily doped into the graphite-Fe-based alloy system to grow nitrogendoped diamond crystals under a relatively high pressure （about 6.0 GPa） by employing the temperature gradient method. Gem-grade diamond crystal with a size of around 5 mm and a nitrogen concentration of about 1173 ppm is successfully synthesised for the first time under high pressure and high temperature in a China-type cubic anvil highpressure apparatus. The growth habit of diamond crystal under the environment with high degree of nitrogen doping is investigated. It is found that the morphologies of heavily nitrogen-doped diamond crystals are all of octahedral shape dominated by {111} facets. The effects of temperature and duration on nitrogen concentration and form are explored by infrared absorption spectra. The results indicate that nitrogen impurity is present in diamond predominantly in the dispersed form accompanied by aggregated form, and the aggregated nitrogen concentration in diamond increases with temperature and duration. In addition, it is indicated that nitrogen donors are more easily incorporated into growing crystals at higher temperature. Strains in nitrogen-doped diamond crystal are characterized by micro-Raman spectroscopy. Measurement results demonstrate that the undoped diamond crystals exhibit the compressive stress, whereas diamond crystals heavily doped with the addition of Ba（N3）2 display the tensile stress.

关键词： temperature gradient method gem-grade nitrogen-doped diamond crystals high temperature and high pressure additive Ba(N3)2

Morphology Change of Metastable Regrown Graphite with Boron Additive under HPHT

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Journal of Materials Science & Technology 2009年第4期25卷 539-542页

作者： Chuanyi Zang Xiaozhou Chen Qiang Hu Wei Guo Guofeng Huang Xiaopeng Jia Intitute-of Material Science and Engineering Henan Polytechnic University Jiaozuo 454000 China State Key Laboratory for Superhard Materials Jilin University Changchun 130012 China

By temperature gradient method under high pressure and high temperature （HPHT）, with NiMnCo alloy as the solvent metal, at diamond-stable region of about 5.4 GPa and 1500 K, metastable regrown graphite crystals of different morphology were synthesized. With B as an additive incorporated into the NiMnCo-C system, metastable regrown graphite crystals of sphere-like shape were firstly obtained under HPHT. If the growth system does not contain B, sheet-like regrown graphite crystals, most with regular hexagonal morphology, are grown upwards and standing vertically in the metal solvent. When B additive of 1.0 wt pct was added into carbon source （graphite powder）, all metastable regrown graphite crystals took on the habit of regular sphere-like morphology, and were grown by a spiral layer growth mechanism.

关键词： Graphite High pressure and high temperature temperature gradient method Morphology

Effect of Seed Sizes on Growth of Large Synthetic Diamond Crystals

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Journal of Materials Science & Technology 2008年第2期24卷 153-156页

作者： Chuanyi ZANG Rui LI Hongan MA Shangsheng LI Xiaopeng JIA Institute of Material Science and Engineering Henan Polytechnic University Jiaozuo 454000 China State Key Laboratory for Superhard Materials Jilin University Changchun 130012 China

For the growth of large synthetic diamond crystals by temperature gradient method （TGM）, the grit sizes of seed crystals have great effects on the growth rate and quality of large grown crystals. Because of the limited area of seed surfaces, the maximum diffusion flux of carbon source, which could be absorbed by the seed, is related to the seed size. And with increasing the seed sizes, the growth rates also increase markedly. However, the seed sizes should be lower than a certain value, which determines the crystal quality directly. For example, with NiMnCo alloy as the metal solvent, when the seed size increases from 0.5 to 1.8 mm, the growth rate increases greatly from about 1.1 to 3.2 mg/h; when the size is beyond 2.0 mm, more and more metal inclusions would be incorporated into the grown crystals, and the crystal quality is destroyed heavily. Finite element analysis （FEA） shows that, due to the special assembly of growth cell, the diffusion of carbon source in the metal solvent is very inhomogeneous, which could be substantiated directly by the appearances and shapes of large grown crystals and the remains of carbon source. And this inhomogeneous diffusion of carbon source would be very harmful to the growth of large diamond crystals, especially when large-size seed crystals are used.

关键词： temperature gradient method Diamond Inhomogeneous diffusion Finite element analysis