The advantages of diamonds include high wear resistance, high thermal conductivity and high hardness. They are often mixed with vitrified bonds to prepare abrasive tools for grinding hard brittle materials such as glass, ceramics, gemstones, stone and hard alloys [1–4]. With the advancement of science, the grinding of silicon wafers and other new materials now demand higher quality, higher precision and higher efficiency [5–7]. Due to the small size of ordinary diamonds, it is usually necessary to use a binder to combine them together to produce grinding tools with a certain size, shape and strength . However, the smooth diamond surface is chemically inert, and the bonding strength between diamonds and vitrified bonds is very low. The diamonds easily detach during grinding and the effective utilization rate of diamonds is very low, which greatly reduces the service life of abrasive tools [9, 10]. Moreover, ordinary diamonds often expose only one large cutting edge after being prepared into abrasive tool, and the self-sharpening property of diamonds is poor. During precision machining, the grinding stress of ordinary diamonds is concentrated, and the surface of the workpiece is severely scratched, which greatly reduces the grinding accuracy of the grinding tool [11–13].
In order to increase holding force of binder on diamonds and improve the self-sharpening property of diamonds, many researchers have carried out in-depth studies. The studies have shown that some coatings (Ti, Cr, TiO2, V2O5 etc.) chemically bonded with diamonds, which increased the wettability of the binder to the diamonds and improved the holding force of the binder on the diamonds [8, 14–16]. Some researchers have carried out metal catalytic hydrogenation corrosion and oxygen plasma corrosion studies on diamond surfaces, resulting in micro patterns (pits and bulges) on the diamond surfaces, which effectively increased the holding force of the binder on the diamonds [17, 18]. The above methods do improve the holding force of the binder on diamonds, but they do not change the self-sharpening property of diamonds and the machining efficiency has not been improved. Impressively, large size single particle porous diamonds were prepared on seed diamonds that were mixed with a micron/submicron-scale diamond powders and metal catalyst powders when combined using high-pressure and high-temperature techniques . This method produced a new type of diamond with a porous skeleton structure, which improved the self-sharpening property of the diamond. However, the synthesis conditions of this method were relatively high (at 5.5 Gpa and 1260°C).
In view of the above problems, if foam-like porous diamond can be prepared, it will be beneficial for improving the holding force of the binder on diamonds. Compared with the coarse cutting-edge of ordinary diamonds, there are numerous small cutting edges on surface of the porous diamonds, which can disperse grinding stress and refine grinding lines. Under relatively lower pressure, porous diamonds can produce new cutting edges via local crushing, thus stabilizing and maintaining the high-efficiency and high-quality machining of the tool.
In this study, Fe/Fe2O3 was used to corrode diamonds at 950°C, and the porous diamonds were prepared after corrosion and acid pickling (our published research ). The conditions required for synthetic production of porous diamonds are relatively simple, and industrial production of the single particle porous diamonds is possible following our study. We have carried out an in-depth and detailed investigation on the diamond with porous structure. The morphology of the diamonds after corrosion was analyzed by SEM (scanning electron microscope). The particle size, pore volume and specific surface area of the diamonds before and after corrosion treatment were analyzed by laser particle size analyzer and BET (Brunauer-Emmett-Teller). The wettability of vitrified bonds to diamonds was analyzed by SEM (scanning electron microscope), wetting angle, XPS (X-ray photoelectron spectroscopy), zeta potential and EDS (Energy dispersive spectroscopy). The properties of vitrified bonds/diamonds composites were analyzed by porosity, density, bending strength and hardness. The grinding performance of the grinding tool was analyzed by comparing the surface roughness of silicon wafers before and after grinding. The grinding mechanism of the grinding tool was analyzed by comparing the SEM images of the grinding tool surface before and after grinding. Up till now, there has not been any research studies performed on the bonding properties of vitrified bonds with porous diamonds nor on the grinding performance of porous diamond abrasive tools. Our study provides new ideas for the application of the innovative high-performance porous diamond abrasive tools.