ZrB2 and ZrB2-SiC powders have been produced by reducing ZrO2 and ZrSiO4 with B4C without using any furnace.Magnesium was added to the mixtures of (ZrO2+B4C) and (ZrSiO4+B4C).The reaction has been assisted by a floral...ZrB2 and ZrB2-SiC powders have been produced by reducing ZrO2 and ZrSiO4 with B4C without using any furnace.Magnesium was added to the mixtures of (ZrO2+B4C) and (ZrSiO4+B4C).The reaction has been assisted by a floral thermite packed around the compacts.By introducing elemental Si into (ZrO2+B4C) mixture,composite powders of ZrB2-SiC formed.After leaching out MgO with suitable HCl water solution,the product was analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).The effect of Si,B4C,and Mg on the extent of formation of ZrB2,ZrB2-SiC,and other phases has been studied.Formation of nano-sized ZrB2 and ZrB2-SiC composite powders was identified.The adaptability of the process for bulk production was examined.展开更多
A SiC/ZrSiO4？SiO2 （SZS） coating was successfully fabricated on the carbon/carbon （C/C） composites by pack cementation, slurry painting and sintering to improve the anti-oxidation property and thermal shock r...A SiC/ZrSiO4？SiO2 （SZS） coating was successfully fabricated on the carbon/carbon （C/C） composites by pack cementation, slurry painting and sintering to improve the anti-oxidation property and thermal shock resistance. The anti-oxidation properties under different oxygen partial pressures （OPP） and thermal shock resistance of the SZS coating were investigated. The results show that the SZS coated sample under low OPP, corresponding to the ambient air, during isothermal oxidation was 0.54% in mass gain after 111 h oxidation at 1500 ° C and less than 0.03% in mass loss after 50 h oxidation in high OPP, corresponding to the air flow rate of 36 L/h. Additionally, the residual compressive strengths （RCS） of the SZS coated samples after oxidation for 50 h in high OPP and 80 h in low OPP remain about 70% and 72.5% of those of original C/C samples, respectively. Moreover, the mass loss of SZS coated samples subjected to the thermal cycle from 1500 ° C in high OPP to boiling water for 30 times was merely 1.61%.展开更多
虽然单纯形法在各领域应用已有很多报道,但大多抽象、难懂、不易掌握。本文主要简单介绍了单纯形的应用原理,以及在生产Zr Si O4粉体中采用单纯形法优化的好处。实验结果表明:单纯形法无须知道每个参数间函数关系,仅是寻找函数最陡的变...虽然单纯形法在各领域应用已有很多报道,但大多抽象、难懂、不易掌握。本文主要简单介绍了单纯形的应用原理,以及在生产Zr Si O4粉体中采用单纯形法优化的好处。实验结果表明:单纯形法无须知道每个参数间函数关系,仅是寻找函数最陡的变化方向。正如爬山,选最陡的坡攀爬才能较快到达山顶。单纯形法不管变量再多,一次仅作一次实验。随时依据实验情况增改因子,变化步长。在陡的方向可增大步长,缓的方向可减小步长,增加搜索速度和精度。因此,是一种非常高效的优化方法,值得推广应用。展开更多
文摘ZrB2 and ZrB2-SiC powders have been produced by reducing ZrO2 and ZrSiO4 with B4C without using any furnace.Magnesium was added to the mixtures of (ZrO2+B4C) and (ZrSiO4+B4C).The reaction has been assisted by a floral thermite packed around the compacts.By introducing elemental Si into (ZrO2+B4C) mixture,composite powders of ZrB2-SiC formed.After leaching out MgO with suitable HCl water solution,the product was analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).The effect of Si,B4C,and Mg on the extent of formation of ZrB2,ZrB2-SiC,and other phases has been studied.Formation of nano-sized ZrB2 and ZrB2-SiC composite powders was identified.The adaptability of the process for bulk production was examined.
基金Project supported by the Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center,ChinaProject(51205417)supported by the National Natural Science Foundation of China
文摘A SiC/ZrSiO4？SiO2 （SZS） coating was successfully fabricated on the carbon/carbon （C/C） composites by pack cementation, slurry painting and sintering to improve the anti-oxidation property and thermal shock resistance. The anti-oxidation properties under different oxygen partial pressures （OPP） and thermal shock resistance of the SZS coating were investigated. The results show that the SZS coated sample under low OPP, corresponding to the ambient air, during isothermal oxidation was 0.54% in mass gain after 111 h oxidation at 1500 ° C and less than 0.03% in mass loss after 50 h oxidation in high OPP, corresponding to the air flow rate of 36 L/h. Additionally, the residual compressive strengths （RCS） of the SZS coated samples after oxidation for 50 h in high OPP and 80 h in low OPP remain about 70% and 72.5% of those of original C/C samples, respectively. Moreover, the mass loss of SZS coated samples subjected to the thermal cycle from 1500 ° C in high OPP to boiling water for 30 times was merely 1.61%.
文摘虽然单纯形法在各领域应用已有很多报道,但大多抽象、难懂、不易掌握。本文主要简单介绍了单纯形的应用原理,以及在生产Zr Si O4粉体中采用单纯形法优化的好处。实验结果表明:单纯形法无须知道每个参数间函数关系,仅是寻找函数最陡的变化方向。正如爬山,选最陡的坡攀爬才能较快到达山顶。单纯形法不管变量再多,一次仅作一次实验。随时依据实验情况增改因子,变化步长。在陡的方向可增大步长,缓的方向可减小步长,增加搜索速度和精度。因此,是一种非常高效的优化方法,值得推广应用。
