Papers by Author: Long Cheng Yin

Abstract: Boron doped diamond (BDD) films were deposited on porous Ti substrates by direct current plasma chemical vapor deposition (DC-PCVD) system. For improve adhesion between diamond and porous Ti, and shorten diamond nucleation period, appropriate pretreatments were carried out. Micro diamond particles were mechanical embedded in the holes of porous Ti substrates and then nanodiamond powders were seeded on substrates by ultrasound sonication prior to deposition. The samples were examined by scanning electron microscopy (SEM), micro-Raman spectroscopy, and cyclic voltammetry. It was found that BDD films covered the whole porous Ti substrate surface, and exhibited the good electrochemical property.

Abstract: In this study we report on the synthesis and characterization of thermally stable polycrystalline diamond (PCD) using Ni-based alloys catalyst as a sintering aid and the B-doped diamond powder in the infiltrating way. The samples were treated at 5.6 GPa and 1200–1480 °C for 10 min in China-type cubic high pressure apparatus. Scanning electron microscopy showed significant intergrowth of the diamond particles sintered in the presence of Ni-based alloy. X-ray diffraction showed the phase change of the samples sintered at the different temperature. Differential thermal analysis (DTA) and thermogravimetric analysis (TG) showed the sample was significantly more heat-resisting compared to conventional PCD. The results showed that the appropriate conditions of thermally stable PCD sintered were 5.6GPa and 1200–1480 °C.

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.