Showing 2 results for Silicon.
M. Babashahi, M.h.enayati, M. Salehi, A. Monshi,
Volume 29, Issue 1 (6-2010)
Abstract
In the present study phase transformation of silicon and silica during milling in different atmospheres was investigated. The silicon powder was subjected to high energy ball milling in ammonia (25%) atmosphere. The milled powder was subsequently annealed at 1200 ◦C for 1 hour. In another test a mixture of AlN and amorphous silica (micro silica) was subjected to high energy ball milling. The milled powder mixture was subsequently annealed at 1200 ◦C for 2 hours. Phase analysis of the as milled and annealed powders was performed by X-ray diffractometery (XRD). Powder morphology was also examined using a scanning electron microscope (SEM). Results showed that ball milling of silicon in ammonia formed an amorphous phase which transformed to quartz on further milling. After annealing quartz, cristobalite and another oxide phase called O phases were developed on XRD patterns. Ball milling of AlN and amorphous silica led to the transformation of amorphous silica to stishovite phase. This process was completed after annealing..
M. Mahallati, M. Khosravi,
Volume 39, Issue 2 (8-2020)
Abstract
In this research, using phenolic resin as the precursor of carbon and various amounts of ethylene glycol as a pore former, porous samples of hard carbon were synthesized. Samples were characterized by x-ray diffraction (XRD) and N2 adsorption-desorption methods. Broad diffraction peaks represent the amorphous structure of samples. Moreover, the gas adsorption-desorption curves showed that the adsorption isotherms of samples were of type IV and all samples had meso-micro porous structure. Charge-discharge tests were performed on samples to obtain their capacities. The sample with higher capacity, broader XRD pattern and appropriate porosity, was selected for silicon incorporation. Silicon nanoparticles were obtained by mechanical milling of its micro particles. According to XRD patterns, silicon nanoparticles had a crystalline structure. Field emission scanning electron microscopy (FESEM) images approved uniform distribution of nanoparticles. XRD patterns of nanocomposites evidenced the existence of hard carbon and silicon. The electrochemical test results showed that the capacity, coulombic efficiency and cycle life of nanocomposites were improved by increasing the amount of silicon.
