# Strengthening Mechanism of Char in Thermal Reduction Process of Silicon Dioxide

## TL;DR

This study explores how different types of char affect the thermal reduction of silicon dioxide, identifying structural and temperature factors that improve efficiency and product quality in silicon production.

## Contribution

The study identifies microcrystalline ordering in char as the primary factor influencing reactivity in silicon dioxide reduction and proposes a two-stage ferrosilicon formation mechanism.

## Key findings

- HY1 char showed the best reactivity due to its highly ordered microcrystalline structure and low defect ratio.
- Optimal reaction performance was achieved at 1550 °C with the addition of Fe2O3 as a superior catalyst.
- A two-stage pathway was identified for ferrosilicon formation involving SiC and FeSi intermediates.

## Abstract

This study investigates the strengthening mechanisms of char in silicon dioxide thermal reduction through systematic high-temperature experiments using three char types (YQ1, CW1, HY1) characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and scanning electron microscopy. HY1 char demonstrated superior reactivity due to its highly ordered microcrystalline structure, characterized by the largest aromatic cluster size (La) and lowest defect ratio (ID/IG = 0.37), which directly correlated with enhanced reaction completeness. The carbon–silicon reaction reactivity increased progressively with temperature, achieving optimal performance at 1550 °C. Addition of Fe and Fe2O3 significantly accelerated the reduction process, with Fe2O3 exhibiting superior catalytic performance by reducing activation energy and optimizing reaction kinetics. The ferrosilicon formation mechanism proceeds through a two-stage pathway: initial char-SiO2 reaction producing SiC and CO, followed by SiC–iron interaction generating FeSi, which catalytically promotes further reduction. These findings establish critical structure–performance relationships for char selection in industrial silicon production, where microcrystalline ordering emerges as the primary performance determinant. The identification of optimal temperature and additive conditions provides practical pathways to enhance energy efficiency and product quality in silicon metallurgy, enabling informed raw material selection and process optimization to reduce energy consumption and improve operational stability.