基于CDC原理的纳米金刚石常压合成与机理研究

Due to its combined excellent behaviors arising from diamond and nano-material, nanodiamond shows great application potential in the fields of machinery, chemical engineering, electronic information and biomedicine, etc., and has become one of the research focuses in the world wide. However, the synthesis of nanodiamond is presently performed under relatively severe conditions, and the high energy circumstances (including high temperature and high pressure or high energy particle beam) are usually required. Up to now, the principle and the route for the synthesis of nanodiamond under moderate conditions are still under investigation. In the course of studying the microstructural evolution of carbide-derived carbon(CDC), we found that, when the CDC was prepared at ambient pressure from the carbide, which was pre-crashed by GCr15 steel-made grinding ball, the iron induced from the ball led to the catalytic formation of nanodiamond. However, when the catalysis results from only the component in the steel-made ball, the type of catalyst is single and the induced amount is uncontrollable. To address the drawback, we propose an embedding and cladding technique for the introduction of catalysts through exerting high stress in the present application. By means of this technique proposed in the application, we will systematically probe into the effect of the type and the introduced amount for the catalysts on the formation of nanodiamond, disclose the underlying synthesis mechanism of nanodiamond at ambient pressure based on the formation route of CDC, and, furthermore, master the scalable production technology at ambient pressure. The application focuses on the new principle and the novel technical route for the synthesis of nanodiamond at ambient pressure, thereby laying the foundation for the practical application of this synthesis technique of nanodiamond at ambient pressure in view of academic research.

纳米金刚石兼具金刚石与纳米材料的双重特性，在机械、化工、电子信息、生物医学等众多领域应用前景广阔，一直是各国科学家的研究热点之一。然而，目前纳米金刚石的合成条件大多比较苛刻，需借助外界高能量环境（如高温高压或者高能量束）来实现。至于如何在非苛刻条件下合成出纳米金刚石，其原理与方法迄今仍处于探索阶段。申请者在研究碳化物衍生碳（CDC）结构演化时发现：当采用由GCr15磨球破碎的碳化物常压下制备CDC时，自磨球引入的金属铁导致了纳米金刚石的催化形成。针对单纯利用钢质磨球自身组份催化所存在的催化剂类型单一、引入量不可控等不足，本申请提出了一种催化剂高应力嵌入包埋技术，并拟利用该技术系统研究催化剂类型、数量等对纳米金刚石形成的影响规律，揭示基于CDC原理的纳米金刚石常压合成机理，掌握其常压宏量制备技术。本申请聚焦纳米金刚石常压合成的新原理、新方法，相关工作的开展将会为推进该技术的实际应用奠定基础。

性能优异的纳米金刚石（ND）的合成条件通常非常苛刻。因此，有必要发展温和条件下合成ND的新原理与新技术。本项目基于碳化物衍生碳（CDC）合成原理，综合运用催化剂高应力嵌入碳化物前驱体与氯气蚀刻技术，以实现ND的常压催化合成。主要研究内容和重要结果如下：.(1) 研究了催化剂引入方式对ND常压催化合成的影响。结果发现：当采用机械混合方式在VC中引入催化剂Fe时，Fe只具有催化石墨化作用；而当催化剂Fe通过高应力嵌入模式引入时，Fe则可催化合成出ND，证实了基于CDC原理常压合成ND技术的可行性。.(2) 研究了碳化物前驱体类型与催化合成ND的种类及尺寸的相关性。结果表明：碳化物前驱体的化学键及ρc值（单位体积碳原子数）可能对催化合成ND有重要影响。对于共价键的β-SiC或ρc值低的NbC，没有或极少ND催化合成；当催化蚀刻ρc值较高的VC时，合成的ND多是尺寸较大的H型ND；而催化蚀刻ρc值较低的TiC时，所合成ND主要是尺寸较小的C型和R型ND。.(3) 探讨了催化剂种类对催化合成ND的影响。结果表明：催化剂类型对ND的类型和尺寸有重要影响。当Fe和Ni作为催化剂时，合成的ND多为3C型和R型ND，只能得到少量的H型ND；而使用Co作为催化剂，H型和小尺寸 ND结构的占比明显增加。.(4) 初步探讨了ND的常压催化合成机制。发现：合成的ND主要出现在距离催化剂较近的CDC颗粒边缘区域，并且，距离被包埋的催化剂越近，3C型及大尺寸的ND比例越高；距离催化剂越远，H型和R型及小尺寸的ND比例增多。.（5）初步探讨了ND的宏量制备及提纯技术。发现：以TiC为前驱体，采用FeNi50合金催化可大幅增加结构完整的ND形成，实现了ND的宏量制备；在550℃热空气环境处理5小时，可获高纯度的ND粉末；该ND粉末表现出出色的热稳定性和良好的导热性能。.本项目发展了一种常压合成ND的新原理与新技术。所合成的ND类型丰富，这也是区别于已有ND合成技术的重要特色之一，从而为研究特定类型ND的性质与应用，以及针对特定应用需求，开发调控ND类型的技术策略奠定了基础。