| Synthesis of Novel Al2O3-Mullite-cBN Composites from a
Mixture of Al2O3 with SiO2 Nanolayer Coated cBN by
Rotary CVD and Spark Plasma Sintering |
Xin Zhang, Jianfeng Zhang*, Takashi Goto1 and Yuping Wu
pages : 148-151
DOI : 10.1080/0371750X.2015.1051627 |
| Abstract |
| In the present study, novel Al2O3-mullite-cBN composites were synthesized from a mixture of Al2O3 and SiO2 coated
on cBN (cBN/SiO2) by spark plasma sintering. SiO2 nanolayer was coated on cBN powder (cBN/SiO2) by rotary CVD
using tetraethyl orthosilicate as a precursor and O2 as a reactive gas. The thickness of SiO2 nanolayer (TSSiO2)
increased from 32 to 52 nm with increasing FO2 from 0 to 0.4210–6 m3.s–1, and then decreased to 25 nm with
increasing FO2 to 0.4210–6 m3.s-1. The cBN/SiO2 powder was mixed with Al2O3 and consolidated by spark plasma
sintering at 1473-1873 K for 0.6 ks. A uniform mullite (Al6Si2O13) phase was formed at 1673 K by the reaction of SiO2
nanolayer with Al2O3. At a sintering temperature of 1573 K and TSSiO2 = 52 nm, the relative density and the hardness
of Al2O3-mullite-cBN was 97% and 24.9 GPa, respectively. The obtained hardness was about 3.9 GPa higher than
that of monolithic Al2O3, 12.4 GPa higher than that of SiO2-cBN, and 8.9 GPa higher than that of SiAlON-cBN and
mullite-cBN composites, suggesting that the as-obtained Al2O3-mullite-cBN composites could be possibly used for
cutting and wear resistant applications.
[Keywords: Rotary CVD, SiO2 nanolayer, Cubic boron nitride (cBN), Spark plasma sintering, Densification] |
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