Densification Behavior of Fused Silica: Effects of Particle Size, Compaction Pressure, Sintering Temperature/Time, and Boron Oxide Addition

Document Type : Research Paper

Authors

Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz, Iran

Abstract

This study systematically investigates the optimization of processing parameters for 400-mesh Chinese fused silica ceramics, focusing on milling, blending, and sintering strategies to achieve high-density components. Twenty-hour attrition milling with zirconia balls (40:1 ball-to-powder ratio) produces a homogeneous powder with an average particle size of ~ 5 µm, enhancing sinterability compared to unmilled powder. Excessive milling, however, reduces green density due to increased interparticle friction. A 70:30 blend of milled/unmilled powder provides an optimal balance between enhanced diffusion kinetics (from milled powder) and improved particle packing (from unmilled powder). This blend achieves 94% theoretical density after sintering at 1250 °C for 5 hours, while reducing milling energy by 30%. Prolonged sintering (> 5 h) promotes cristobalite formation, grain growth, and density reduction, underscoring the importance of precise thermal control.   B₂O₃ additions (0.5–3 wt.%) hinder densification by promoting premature crystallization and disrupting diffusion pathways, making it unsuitable as a sintering aid. SEM analysis confirms that the 70/30 blend yields uniform grains (1.5 ± 0.3 µm) with minimal porosity (< 6%), outperforming both fully milled and unmilled powders. These findings provide a practical framework for industrial production, emphasizing cost-effective blending and optimized sintering protocols to achieve high-performance fused silica ceramics.

Keywords

References

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Iranian Journal of Materials Forming
Volume 12, Issue 4
2025
Pages 44-53

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