+Model JECS-7698; No of Pages 8 ARTICLE IN PRESS H. Wu, w. Zhang/Journal of the European Ceramic Society rcx(2009)ccx-cox 1# ZrSio 10. Oum 1000u KEnt 3# 1# 2 0.6 3.00 1002003.00 Energy -keV Energy -kev Fig 8. Cross-sectional micrographs of Zs2 after oxidation at 1500C for 2h (b) During the temperature from 1100C to 1300C. Large it contains an appropriate amount of BN (30 vol%)com- mount of volatile B2O3 would form. And very important pared with the sample Zso, so more B203 was generated. the formation of sio derived from the oxidation of sic and more easily spread in the material surface for oxide film. becomes significant, reaction between SiO and B2O3 leads Moreover, the sample ZS2 contains a higher proportion of to a stable borosilicate glass. The borosilicates would act silicon carbide than Zso and ZSI. therefore more silicon Is a protective layer to reduce oxidation rate more effec oxide forms in ZS2 than that does in zso and ZsI. The ively than B2O3 due to lower volatility and smaller oxygen higher SiO2 content in borosilicate glass, the higher the vis- ffusivity.7-19The sample ZS3 gets the highest rate of spe cosity and melting point of borosilicate glass are, which can cific weight gain, which is attributed to the largest content more effectively cover and protect the surface of samples of BN (35 vol%). The formation of B2O3 from the oxidation Therefore. the oxidation resistance of Zs2 with a suitable of bn shows the obvious weight gain. For the sample ZS2, amount of bn additive is better than other samples Please cite this article in press as: Wu, H, Zhang, w, Fabrication and properties of ZrB2-SiC-BN machinable ceramics, J. Eur Ceram. Soc. (2009),doi:10.10l6/ eurceramsoc2009.09.02Please cite this article in press as: Wu, H., Zhang, W, Fabrication and properties of ZrB2–SiC–BN machinable ceramics, J. Eur. Ceram. Soc. (2009), doi:10.1016/j.jeurceramsoc.2009.09.022 ARTICLE IN PRESS +Model JECS-7698; No. of Pages 8 6 H. Wu, W. Zhang / Journal of the European Ceramic Society xxx (2009) xxx–xxx Fig. 8. Cross-sectional micrographs of ZS2 after oxidation at 1500 ◦C for 2 h. (b) During the temperature from 1100 ◦C to 1300 ◦C. Large amount of volatile B2O3 would form. And very important, the formation of SiO2 derived from the oxidation of SiC becomes significant, reaction between SiO2 and B2O3 leads to a stable borosilicate glass. The borosilicates would act as a protective layer to reduce oxidation rate more effec￾tively than B2O3 due to lower volatility and smaller oxygen diffusivity.17–19 The sample ZS3 gets the highest rate of spe￾cific weight gain, which is attributed to the largest content of BN (35 vol%). The formation of B2O3 from the oxidation of BN shows the obvious weight gain. For the sample ZS2, it contains an appropriate amount of BN (30 vol%) com￾pared with the sample ZS0, so more B2O3 was generated, and more easily spread in the material surface for oxide film. Moreover, the sample ZS2 contains a higher proportion of silicon carbide than ZS0 and ZS1, therefore more silicon oxide forms in ZS2 than that does in ZS0 and ZS1. The higher SiO2 content in borosilicate glass, the higher the vis￾cosity and melting point of borosilicate glass are, which can more effectively cover and protect the surface of samples. Therefore, the oxidation resistance of ZS2 with a suitable amount of BN additive is better than other samples