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
ZrO 2(Y 2O 3) powder and SiC nanopowder were prepared by carbothermal reduction of ZrSiO 4. With the existence of additive Y 2O 3 and other impurities, ZrSiO 4 was dissociated into ZrO 2 and SiO 2 in the condition of ...ZrO 2(Y 2O 3) powder and SiC nanopowder were prepared by carbothermal reduction of ZrSiO 4. With the existence of additive Y 2O 3 and other impurities, ZrSiO 4 was dissociated into ZrO 2 and SiO 2 in the condition of 1450—1550?℃. ZrO 2(Y 2O 3)powder was thus obtained via the removal of SiO 2 as silicon oxide (SiO) gas during carbothermal reduction process. SiC nanopowder and small amount of SiC whisker were synthesized form the gas-phase reaction between SiO vapor and supplied CH 4 gas.展开更多
采用两段式包埋法工艺可制得涂层结构合理的复合梯度涂层,从里到外涂层结构为:S iC过渡层→S iC致密层→M oS i2/S iC双相层→以M oS i2为主的外层。随着制备工艺中高温阶段保温时间的延长,涂层表面以M oS i2为主的薄层越连续。涂层与...采用两段式包埋法工艺可制得涂层结构合理的复合梯度涂层,从里到外涂层结构为:S iC过渡层→S iC致密层→M oS i2/S iC双相层→以M oS i2为主的外层。随着制备工艺中高温阶段保温时间的延长,涂层表面以M oS i2为主的薄层越连续。涂层与基体的结合以化学结合为主,并有机械结合,结合强度高。用正硅酸四乙酯对涂层表面进行封闭处理,凝胶形成的S iO2可充填涂层表面裂纹并覆盖在涂层表面。在1 500℃高温空气中氧化,未封闭处理的涂层试样表现为氧化失重,封闭处理后的试样氧化增重。展开更多
ZrSiO_4 bulk was prepared by pressureless sintering process and ZrSiO_4 coating was deposited on the SiC f/Si C substrate using air plasma method. The microstructures of ZrSiO_4 bulk and ZrSiO_4 coating are both dense...ZrSiO_4 bulk was prepared by pressureless sintering process and ZrSiO_4 coating was deposited on the SiC f/Si C substrate using air plasma method. The microstructures of ZrSiO_4 bulk and ZrSiO_4 coating are both dense. A preliminary study of a water vapor corrosion test for ZrSiO_4 bulk and ZrSiO_4 coating was performed under the conditions of 1.013×105 Pa, 90%H_2O/10%O_2, 1300 ℃, and low gas velocity. Results show that some pores appear on the surface of the ZrSiO_4 bulk. The main crystal phase is ZrO_2 and the weight loss of ZrSiO_4 bulk is only 0.236 mg/cm^2 after corrosion. The ZrSiO_4 coating peels off from the substrate after 109 h. The number and intensity of diffraction peaks of ZrO_2 in the coating increase, and the major crystal phase of the coating is still ZrSiO_4. A porous microstructure accompanied with cracks is observed on the surface of ZrSiO_4 coating after corrosion.展开更多
The properties and low and medium tem-perature bonding mechanisms of varied types of SiO2 ultrafine powder used in ceramic and refractory and the temperature at which SiO2 ultrafine powder began to react with Al2O3 we...The properties and low and medium tem-perature bonding mechanisms of varied types of SiO2 ultrafine powder used in ceramic and refractory and the temperature at which SiO2 ultrafine powder began to react with Al2O3 were studied,And initial researches on effects of ultrafine powders of Al2O3,SiC,3Al2o3·2SiO2,MgO·Al2O3 and ZrSiO4 on promoting sintering were made. The results indicated that among various types of SiO2 ultrafine powder ,non-crystal sil-ica ultrafine powder wa characterized by its structure and properties,It could yield consid-erable silica gel on its surface at low tempera-ture,which then dehydrated and formed Si-O-Si bond,thereby developing a netty structure that caused higher bond strength at low and medium temperature since the netty structure basically remperature since the netty structure basically reained as termperture rising.SiO2 ultrafine powder began to react with Al2O3 at 700℃, All of other types of ultrafine powder had effects on stimulating sintering ,but the effects were significant only when the particle size of ultrafine powder was less than 5μm。展开更多
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ZrO 2(Y 2O 3) powder and SiC nanopowder were prepared by carbothermal reduction of ZrSiO 4. With the existence of additive Y 2O 3 and other impurities, ZrSiO 4 was dissociated into ZrO 2 and SiO 2 in the condition of 1450—1550?℃. ZrO 2(Y 2O 3)powder was thus obtained via the removal of SiO 2 as silicon oxide (SiO) gas during carbothermal reduction process. SiC nanopowder and small amount of SiC whisker were synthesized form the gas-phase reaction between SiO vapor and supplied CH 4 gas.
文摘采用两段式包埋法工艺可制得涂层结构合理的复合梯度涂层,从里到外涂层结构为:S iC过渡层→S iC致密层→M oS i2/S iC双相层→以M oS i2为主的外层。随着制备工艺中高温阶段保温时间的延长,涂层表面以M oS i2为主的薄层越连续。涂层与基体的结合以化学结合为主,并有机械结合,结合强度高。用正硅酸四乙酯对涂层表面进行封闭处理,凝胶形成的S iO2可充填涂层表面裂纹并覆盖在涂层表面。在1 500℃高温空气中氧化,未封闭处理的涂层试样表现为氧化失重,封闭处理后的试样氧化增重。
基金supported by the National Natural Science Foundation of China under Grant No.51772027
文摘ZrSiO_4 bulk was prepared by pressureless sintering process and ZrSiO_4 coating was deposited on the SiC f/Si C substrate using air plasma method. The microstructures of ZrSiO_4 bulk and ZrSiO_4 coating are both dense. A preliminary study of a water vapor corrosion test for ZrSiO_4 bulk and ZrSiO_4 coating was performed under the conditions of 1.013×105 Pa, 90%H_2O/10%O_2, 1300 ℃, and low gas velocity. Results show that some pores appear on the surface of the ZrSiO_4 bulk. The main crystal phase is ZrO_2 and the weight loss of ZrSiO_4 bulk is only 0.236 mg/cm^2 after corrosion. The ZrSiO_4 coating peels off from the substrate after 109 h. The number and intensity of diffraction peaks of ZrO_2 in the coating increase, and the major crystal phase of the coating is still ZrSiO_4. A porous microstructure accompanied with cracks is observed on the surface of ZrSiO_4 coating after corrosion.
文摘The properties and low and medium tem-perature bonding mechanisms of varied types of SiO2 ultrafine powder used in ceramic and refractory and the temperature at which SiO2 ultrafine powder began to react with Al2O3 were studied,And initial researches on effects of ultrafine powders of Al2O3,SiC,3Al2o3·2SiO2,MgO·Al2O3 and ZrSiO4 on promoting sintering were made. The results indicated that among various types of SiO2 ultrafine powder ,non-crystal sil-ica ultrafine powder wa characterized by its structure and properties,It could yield consid-erable silica gel on its surface at low tempera-ture,which then dehydrated and formed Si-O-Si bond,thereby developing a netty structure that caused higher bond strength at low and medium temperature since the netty structure basically remperature since the netty structure basically reained as termperture rising.SiO2 ultrafine powder began to react with Al2O3 at 700℃, All of other types of ultrafine powder had effects on stimulating sintering ,but the effects were significant only when the particle size of ultrafine powder was less than 5μm。
