Document Type : Research Paper
School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran, Iran.
Silicon nanoparticles are the focus of attention thanks to their potentialities in advanced applications such as new batteries, photovoltaic cells and so on. The need to porous silicon is thus rising and will follow the same trend. In this work, highly porous nanostructured silicon is synthesized via Self-propagating high-temperature synthesis (SHS) route. Microstructural and phase analyses show that the employed technique is capable of producing a three-dimensional porous silicon which can act as a skeleton for embedding lithium ions and therefore, resisting large volume expansions arising during lithiation phase. Considering the fact that the wave front experiences high temperatures (above 1900°C) which can result in nanoparticles’ sintering, and in order to improve the porosity level, ammonium nitrate is used as a neutral additive at Mg/SiO2/NH4NO3 (2.4:1:0.1) molar ratio. The influence of nitrate addition on the final microstructure is studied through comparing salt-added samples with bare ones. Results show that ammonium nitrate can hinder the agglomeration of silicon nanoparticles during the progress of combustion wave thus affecting the specific surface area significantly (138.3 m2 g-1 as compared to for the 43.8 m2 g-1 for the reference sample which lacks NH4NO3). On the other hand, it was found that the added salt does not affect the product purity as examined through X-ray diffraction analysis.