Sintering boron carbide ceramics without grain growth by plastic deformation as the dominant densification mechanism.

Wei Ji,Fan Zhang,Sahibzada Shakir Rehman,Jinyong Zhang,Weimin Wang,Hao Wang,Yucheng Wang,Zhengyi Fu

doi:10.1038/srep15827

Abstract

A new ceramic sintering approach employing plastic deformation as the dominant mechanism is proposed, at low temperature close to the onset point of grain growth and under high pressure. Based on this route, fully dense boron carbide without grain growth can be prepared at 1,675–1,700 °C and under pressure of (≥) 80 MPa in 5 minutes. The dense boron carbide shows excellent mechanical properties, including Vickers hardness of 37.8 GPa, flexural strength of 445.3 MPa and fracture toughness of 4.7 MPa•m0.5. Such a process should also facilitate the cost-effective preparation of other advanced ceramics for practical applications.

Highlights

High resistance to grain boundary sliding and low surface tension– makes sintering the powder a difficult task[10]
By calculation of the grain-boundary mobility of polycrystalline, Holm and Foiles proved that there exists a characteristic temperature below which the smooth boundary from low mobility offers a mechanism for grain growth being stopped[22]
We propose to densify ceramic powders at a lower temperature, close to temperature for grain growth (Tg) in the temperature for densification (Td)–Tg region, to avoid the grain-boundary migration and grain growth, and at the same time, apply a relatively higher pressure to the compacted powder to attain full densification

Summary

Introduction

High resistance to grain boundary sliding and low surface tension– makes sintering the powder a difficult task[10]. Pure B4C can be fully densified by Pressure assisted sintering at 2,050–2,200 °C and under applied loads of 30–40 MPa for 15–45 min[7,16]. Such conditions are economically too demanding in terms of energy consumption, so scientists are committed to find better process parameters. Badica and co-workers suggested a high pressure (300 MPa) and low temperature (1,600 °C) SPS strategy and achieved dense B4C with relative density 95.6%. We propose to densify ceramic powders at a lower temperature, close to Tg in the Td–Tg region, to avoid the grain-boundary migration and grain growth, and at the same time, apply a relatively higher pressure to the compacted powder to attain full densification. We plan to sinter micro-size grain B4C, widely used in industry, by the new route in an SPS instrument and hope to provide an energy-efficient and high-performance technique for ceramics fabrication

Methods

Results

Conclusion