Papers by Author: Yan Feng Liu

Abstract: The DC plasma chemical vapor deposition (DC-PCVD) method was a promising technique to fabricate CVD diamond coatings in industry, because it has many good properties, such as high grown rate of diamond films, big grown area, high qualities, and cost effective. In the present work, we synthesized diamond films on cemented carbide (YG6) substrates, and studied the different nitric acid aqueous solution treatment durations influence on diamond nucleation stage. The results indicated that well-chosen nitric acid aqueous solution treatment durations should be selected. For too short treatment times, the residual Co will promote the carbon transform from diamond metastable phase into graphite stable phase. On the other side, too long treatment times will consume too much Co, which will lead to the shortage of cohesive body, and finally the crackers in the bulk propagated and peeled off with the diamond films well grown on WC grains.

Abstract: Synthesis of Ⅱa industrial diamond with high quality at high temperature and high pressure (HTHP) was examined in this paper and Ⅱa industrial diamonds were synthesized successfully. The experimental results show that the lowest synthesis pressure of diamond changed significantly which goes down firstly, and then up with the increasing of Ti content. It is discovered by optical microscopy that the color of synthesizing diamond in nitrogen getter system is lighter than that in raw catalyst power system and most crystals are hexahedrons & octahedrons. The experiment results measured by IR analysis shows that nitrogen content in synthesizing diamond in nitrogen getter system is significantly lower than that in the raw catalyst power system. Surface morphology of diamond synthesized in two different systems is investigated by the aid of SEM.