Abstract
In this paper, the acceleration effect of nickel (Ni) on the direct nitridation process of the diamond-wire saw powder (DWSP) was investigated. The DWSP doped with Ni additives were nitrided at different temperatures. To study the mechanism of accelerated nitridation, the thermodynamics of Si-O-N-Ni and nitridation processes were analyzed by FactSage 7.2 and single-crystal silicon blocks were also nitrided instead of the DWSP. The results revealed that Ni decreased the nitridation temperature at which the DWSP began to gain significant weight and exhibited an excellent accelerating effect on the nitridation of the DWSP. At 1300°C the DWSP containing 2.0 wt% Ni additives had been completely nitrided within 2 h, whereas the DWSP without Ni additives had not been nitrided yet. Based on the equivalent substitution experiment, it could be concluded that the presence of Ni additives accelerated the nitridation and promoted the formation of the α-Si3N4 nanorods through facilitating the generation of the SiO(g) and destructing the silica film on the surface of silicon at lower temperature. Meanwhile, Ni additives also played an important part in the growth of α-Si3N4 nanorods by forming liquid Ni-Si alloy in the product.
Highlights
The global energy crisis and environmental problems are becoming increasingly serious, due to the rapid growth of fossil energy consumption (Chen et al, 2016)
It could be found that the variation trend of both was similar, but the mass gain of the diamond-wire saw powder (DWSP) doped with Ni was obviously higher than that of the direct nitridation of the DWSP
The temperature corresponding to the inflection point of the mass gain curve of the DWSP doped with Ni was 1325°C, which was lower than the temperature (1408°C) corresponding to the inflection point of the TG curve without Ni
Summary
The global energy crisis and environmental problems are becoming increasingly serious, due to the rapid growth of fossil energy consumption (Chen et al, 2016). To solve the problems above mentioned, a lot of efforts on the recycle of high-purity silicon had been carried out (De Sousa et al, 2016; Kong et al, 2019; Lu et al, 2019; Tomono et al, 2013; Yang et al, 2019b). These studies had yielded remarkable results, there is still a long way to go for using as solar-grade feedstocks. Considering that the DWSP contains a small amount of metal impurities, if these metals can accelerate the nitridation process at low temperature, it will be of great significance for the recycling of the DWSP and energy saving. This work provides a scientific basis for the preparation of silicon nitride at low temperature by the nitridation of diamondwire saw powder
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