The cubic polycrystal of SiC (3C-SiC) coating on the quartz glass (QG) surface was successfully prepared via a two-step chemical vapor deposition (CVD) by introducing a thin PyC coating as a buffer layer. Through combining the intake system of CVD PyC and CVD SiC, the SiC/PyC composite coating can be in-situ prepared on the QG without halfway in-and-out chamber. The results showed that the SiC/PyC composite coating possesses highly uniform, dense, and continuous features, while the pure SiC coating exhibits many cracks, implying that the internal stress between the SiC coating and the QG can be relieved by adding the PyC buffer coating. The average hardness of the SiC/PyC/QG is measured to be 46.8 GPa, and its calculated modulus is 416.3 GPa by using a nanoindentation technique. Compared to the pure QG, the friction coefficient of the SiC/PyC/QG is slightly increased to 1.47 vs. 1.45. Moreover, the SiC/PyC/QG displays the excellent anti-acid corrosion in the 5%HF and 5%HCl mixed solution with the weight loss of about 33% lower than the pure QG after 8 h acid test at 80°C.
Magnesium phosphosilicate cement (MPSC) is generally composed of magnesium oxide, phosphate and silicate, and the admixture is generally borax to extend the setting time. In the preparation of traditional magnesium phosphate cement (MPC), reburned magnesium oxide is generally used. In this study, light-burned powder calcinated with borax will be used instead of reburned magnesium oxide to prepare MPC. The calcination temperature range is 10001200°C and the holding time is 2 h. This paper explores the influence of magnesia reactivity at different calcination temperatures on the performance of MPSC, including setting time, electron microscope, heat of hydration, phase composition and strength development. The results show that borax can significantly reduce the reactivity of magnesia. Experimental data shows that as the reactivity of magnesia increases, the mechanical properties of MPSC cement become better, and the porosity will also decrease. However, when the reactivity is too high, the cement cannot be formed because of the early setting time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.