Fe_(70)Ni_(30)粉末触媒中Ⅱa型金刚石大单晶的高温高压合成

Synthesis of Ⅱa Type Diamond Single Crystal in Fe_(70)Ni_(30) Powder Catalyst under High Temperature and High Pressure

在6.5 GPa高压条件下,使用Fe_(70)Ni_(30)粉末触媒研究了Ⅱa型金刚石大单晶的合成。实验结果表明,若不对晶种表面进行保护,高温高压条件下金刚石晶种将发生碳化,致使难以合成出金刚石。当合成腔体中除氮剂Ti/Cu添加量达到2.2wt%时,所合成的金刚石大单晶呈现为无色透明,利用傅里叶显微红外光谱仪(FTIR)对所合成的金刚石大单晶进行了测试,所合成的晶体中不含有氮杂质。然而,FTIR测试结果表明所合成的Ⅱa型金刚石大单晶中有碳-氢基团的存在,其对应的FTIR特征吸收峰分别位于2850 cm^(-1)和2920 cm^(-1)处。此外,所合成的Ⅱa型金刚石大单晶的Raman特征峰位于1132.13 cm^(-1)处,且其结晶度非常高。

The synthesis of Ⅱa type diamond single crystal was investigated at pressure of 6. 5 GPa by temperature gradient growth method,employing Fe70Ni30 powders as catalyst. The experimental results show that the growth of diamond crystal can not run if the diamond seed is not protected during the synthesis process under high pressure and high temperature（HPHT）,because of the carbonization of diamond seed crystal at HPHT conditions. The synthesized diamond exhibited colorless when the addition content of the nitrogen getter Ti/Cu achieve 2. 2 wt% in the synthesis system. It was characterized by FTIR and the result displayed that nitrogen was inexistence in the colorless diamond,indicating that it belongs to Ⅱa type diamond. However,the C-H groups were noticed in the FTIR spectra and the corresponding absorption peaks located at 2850 cm-1 and 2920 cm-1,respectively. Furthermore,the Raman peak of the obtained Ⅱa type diamond located at 1132. 13 cm-1 and the crystallization was perfect.