The green bodies were prepared by adding B4C （0. 5% , 1.5% , 2.5% and 3.5% in mass） or B2O3 （6% and 9% in mass） in fiLsed silica powders, respectivel）, and then were fired at I 150 ℃ for 4 h, 1 200 ℃ for 4 h, ...The green bodies were prepared by adding B4C （0. 5% , 1.5% , 2.5% and 3.5% in mass） or B2O3 （6% and 9% in mass） in fiLsed silica powders, respectivel）, and then were fired at I 150 ℃ for 4 h, 1 200 ℃ for 4 h, and 1 350 ℃ for 0. 5 h, respectively. The bulk density, apparent porosity, cold modulus of rupture and therm（d expansion coefficient of the fired .specimens were determined, and phase compositions and microstructure were researched. The results show that： （1） B4C promotes the sintering of fitsed silica ceramics, but many closed pores will form easily wilh B4 C increase; （2） .fused silica ceramics with 3. 5 mass% maC ha.re 1. 045 × 10-6 ℃ -1 of the lowest average thermal expansion coefficient bet：u,een 40 ℃ and 730 ℃; （3） B4C additive is more effective to restrain crystaUizatioa of fused silica than B2O3 with the same content of boron.展开更多
文摘The green bodies were prepared by adding B4C （0. 5% , 1.5% , 2.5% and 3.5% in mass） or B2O3 （6% and 9% in mass） in fiLsed silica powders, respectivel）, and then were fired at I 150 ℃ for 4 h, 1 200 ℃ for 4 h, and 1 350 ℃ for 0. 5 h, respectively. The bulk density, apparent porosity, cold modulus of rupture and therm（d expansion coefficient of the fired .specimens were determined, and phase compositions and microstructure were researched. The results show that： （1） B4C promotes the sintering of fitsed silica ceramics, but many closed pores will form easily wilh B4 C increase; （2） .fused silica ceramics with 3. 5 mass% maC ha.re 1. 045 × 10-6 ℃ -1 of the lowest average thermal expansion coefficient bet：u,een 40 ℃ and 730 ℃; （3） B4C additive is more effective to restrain crystaUizatioa of fused silica than B2O3 with the same content of boron.
