高温高压下Fe-Ni-C-B系合成Ⅱb型金刚石单晶

Synthesizing Ⅱb type diamond single crystal from an Fe-Ni-C-B system at high temperature and high pressure

提出了一种在高温高压下利用粉末冶金方法制备的Fe-Ni-C-B系触媒合金生长Ⅱb型金刚石的新方法.由于硼元素的存在,Ⅱb型金刚石生长所需的温度和压力条件均高于普通的Ⅰb型金刚石,并且合成出的金刚石单晶粒度较粗,晶形稍差,表面结构比较复杂.通过晶体的颜色、X射线衍射以及Raman光谱可以初步断定合成出的金刚石晶体中确实含有硼元素.以金刚石在不同温度下的静压强度和冲击韧性以及差热分析和热重分析的结果来表征金刚石的热稳定性.实验发现,由于硼元素的进入使得Ⅱb型金刚石单晶的热稳定性与采用同种方法合成出的Ⅰb型金刚石相比有了较大程度的提高.采用自制的夹具通过检测金刚石的电阻温度特性,初步确定了在Fe-Ni-C-B系中生长的Ⅱb型金刚石具有半导体特性.大量的实验数据充分说明,采用这种方法生产Ⅱb型金刚石具有成本低廉、操作简单、产品质量稳定等优点,具有极高的工业化推广应用的价值.

A Ⅱ b type diamond has semiconductivity and superconductivity as well as better heat resistance, wear and chemical inertia than a common synthetic diamond because of the doping of boron. In order to change the condition of high cost and hard to industrialization on Ⅱb type diamond synthesizing, this paper put forward a new synthesizing method using an Fe-Ni-C-B catalyst alloy made by powder metallurgy at high temperature and high pressure. Because of the presence of boron, a Ⅱb type diamond needs a higher temperature and pressure than a common Ⅰb type diamond. Due to the action of boron, the diamond has rough grain size, bad crystal shape and complex surface structure. The presence of boron was primarily ascertained by the color of crystal, X-ray diffraction and Raman spectrum. In addition, the thermal stability of the diamond was characterized with the results of static compressive strength and impact toughness at different temperatures, as well as DSC and TGA analyses. The experimental results show that the thermal stability of the Ⅱb type diamond is improved rapidly. Resistance-temperature characteristics measurement with a self-made clamp proved the semiconductivity of the diamond crystal. Based on summarization and analysis of experimental data, it is obvious that synthesizing a Ⅱb type diamond by this method can be realized easily with low producing cost and is available for synthetic diamond industry.