Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiC_f/SiC composites in high-temperature combust...Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiC_f/SiC composites in high-temperature combustion environment. However, such kinds of interphase materials are not available yet. Herein,we report theoretically predicted properties of two promising interphase materials Y_5Si_3 C and Y_3Si_2C_2.Although crystallizing in different structures, they share the common features of layered structure,anisotropic chemical bonding, anisotropic electrical and mechanical properties, and low shear deformation resistance. The bulk moduli for Y_5Si_3C and Y_3Si_2C_2 are 78 and 93 GPa, respectively; while their shear moduli are 52 and 50GPa, respectively. The maximum to minimum Young's modulus ratios are1.44 for Y_5Si_3C and 3.27 for Y_3Si_2C_2. Based on the low shear deformation resistance and low Pugh's ratios(G/B = 0.666 forY_5Si_3C and 0.537 for Y_3Si_2C_2; G: shear modulus; B: bulk modulus), they are predicted as damage tolerant and soft ceramics with predicted Vickers hardness of 9.6 and 6.9 GPa, respectively.The cleavage plane and possible slip systems are(000 l) and(0001)[1120] and(1010)[0001] forY_5Si_3C,and those for Y_3Si_2C_2 are {h00} and(010)[101]. Since the oxidation products are water-vapor resistant Y2 Si2 O7, Y2 SiO5 and/or Y_2 O_3 upon oxidation, and the volume expansions are ca 140% and ca 26% for Y_5Si_3C and Y_3Si_2C_2, they are expected to seal the interfacial cracks in SiC_f/SiC composites. The unique combination of easy cleavage, low shear deformation resistance, volume expansions upon oxidation, and the resistance of the oxidation products to water vapor attack warrant them promising as interphase materials of SiC_f/SiC composites for water-vapor laden environment applications.展开更多
A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC...A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC)composites.The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600℃using an electric field-assisted sintering technique(FAST).During joining,a liquid phase was formed by the eutectic reaction among Y_(3)Si_(2)C_(2),γ(Y–C)phase,and SiC,followed by the precipitation of SiC particles.The presence of the liquid promoted the sintering of newly formed SiC particles,leading to their complete consolidation with the Cf/SiC matrix.On the other hand,the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa,leading to the formation of the near-seamless joints.The highest shear strength(Ä)of 17.2±2.9 MPa was obtained after being joined at 1600℃for 10 min.The failure of the joints occurred in the Cf/SiC matrix,indicating that the interface was stronger than that of the Cf/SiC matrix.The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling,suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites(CMCs)for extreme environmental applications.展开更多
基金supported financially by the National Natural Science Foundation of China (Nos. U1435206 and 51672064)the Beijing Municipal Science & Technology Commission (No. D161100002416001)
文摘Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiC_f/SiC composites in high-temperature combustion environment. However, such kinds of interphase materials are not available yet. Herein,we report theoretically predicted properties of two promising interphase materials Y_5Si_3 C and Y_3Si_2C_2.Although crystallizing in different structures, they share the common features of layered structure,anisotropic chemical bonding, anisotropic electrical and mechanical properties, and low shear deformation resistance. The bulk moduli for Y_5Si_3C and Y_3Si_2C_2 are 78 and 93 GPa, respectively; while their shear moduli are 52 and 50GPa, respectively. The maximum to minimum Young's modulus ratios are1.44 for Y_5Si_3C and 3.27 for Y_3Si_2C_2. Based on the low shear deformation resistance and low Pugh's ratios(G/B = 0.666 forY_5Si_3C and 0.537 for Y_3Si_2C_2; G: shear modulus; B: bulk modulus), they are predicted as damage tolerant and soft ceramics with predicted Vickers hardness of 9.6 and 6.9 GPa, respectively.The cleavage plane and possible slip systems are(000 l) and(0001)[1120] and(1010)[0001] forY_5Si_3C,and those for Y_3Si_2C_2 are {h00} and(010)[101]. Since the oxidation products are water-vapor resistant Y2 Si2 O7, Y2 SiO5 and/or Y_2 O_3 upon oxidation, and the volume expansions are ca 140% and ca 26% for Y_5Si_3C and Y_3Si_2C_2, they are expected to seal the interfacial cracks in SiC_f/SiC composites. The unique combination of easy cleavage, low shear deformation resistance, volume expansions upon oxidation, and the resistance of the oxidation products to water vapor attack warrant them promising as interphase materials of SiC_f/SiC composites for water-vapor laden environment applications.
基金This study was supported by the National Natural Science Foundation of China(Grant No.11975296)the Natural Science Foundation of Ningbo City(Grant No.2021J199)+3 种基金We would like to recognize the support from the Ningbo 3315 Innovative Teams Program,China(Grant No.2019A-14-C)Peter TATARKO gratefully acknowledges the financial support of the project APVV-17-0328this study was performed as part of the implementation of the project“Building-up Centre for advanced materials application of the Slovak Academy of Sciences”and ITMS project(Grant No.313021T081)supported by the Research&Innovation Operational Programme funded by the ERDF.
文摘A novel Y_(3)Si_(2)C_(2)material was synthesized at a relatively low temperature(900℃)using a molten salt method for the first time,and subsequently used as the joining material for carbon fiber reinforced SiC(Cf/SiC)composites.The sound near-seamless joints with no obvious remaining interlayer were obtained at 1600℃using an electric field-assisted sintering technique(FAST).During joining,a liquid phase was formed by the eutectic reaction among Y_(3)Si_(2)C_(2),γ(Y–C)phase,and SiC,followed by the precipitation of SiC particles.The presence of the liquid promoted the sintering of newly formed SiC particles,leading to their complete consolidation with the Cf/SiC matrix.On the other hand,the excess of the liquid was pushed away from the joining area under the effect of a uniaxial pressure of 30 MPa,leading to the formation of the near-seamless joints.The highest shear strength(Ä)of 17.2±2.9 MPa was obtained after being joined at 1600℃for 10 min.The failure of the joints occurred in the Cf/SiC matrix,indicating that the interface was stronger than that of the Cf/SiC matrix.The formation of a near-seamless joint minimizes the mismatch of thermal expansion coefficients and also irradiation-induced swelling,suggesting that the proposed joining strategy can be potentially applied to SiC-based ceramic matrix composites(CMCs)for extreme environmental applications.
