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Abstract: This work proposes a multi-composition oxidation resistant coating for SiC-coated carbon/carbon (C/C) composites by slurry method using the mixture of Y2O3, ZrO2, Al2O3, Si and C. XRD analysis shows that the phases of the composite coating are composed of SiC, Al2O3, Y2O3, ZrO2, Al4SiC4 and Y3Al2(AlO4)3. SEM analysis of the cross section of the coating displays the microstructure with 500μm thickness which filled the porous SiC. Oxidation test shows that, after 19h oxidation in air at 1873K, the weight loss of the coated SiC-C/C is only 1.76%. The oxidation of the coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks and bubble holes in the coating. [Copyright &y& Elsevier]

Abstract: To prevent carbon/carbon (C/C) composites from oxidation, a multilayer coating based on molybdenum disilicide and titanium disilicide was formed using a two-step pack cementation technique in argon atmosphere. XRD and SEM analysis showed that the internal coating was a bond SiC layer that acts as a buffer layer, and that the external multilayer coating formed in the two-step pack cementation was composed of two MoSi2–TiSi2–SiC layers. This coating, which is characterized by excellent thermal shock resistance, could effectively protect the composites from exposure to an oxidizing atmosphere at 1773K for 79h. The oxidation of the coated C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating. [Copyright &y& Elsevier]

Abstract: To prevent carbon/carbon (C/C) composites from oxidation, a SiC–CrSi2 protective coating toughened with SiC whiskers (SiCw) has been prepared by a two-step technique of slurry and pack cementation. SEM and XRD analysis show that with the SiCw content increasing from 0 to 20wt.%, the coating thickness is reduced from 420 to 100μm, and the CrSi2 proportion in the coating first increases and then decreases. Oxidation tests in the range 1473–1773K shows that the coating toughened with 15wt.% SiCw possesses a better oxidation protective ability because of its more suitable thickness and microstructure. As the oxidation temperature increases from 1473 to 1773K, the oxidation protective ability of the coating improves gradually. The weight loss of the coated samples is primarily due to the reaction of C/C matrix and oxygen diffusing through the cracks in the coating. [Copyright &y& Elsevier]

To improve the bonding properties of the interface between carbon/carbon (C/C) composites and a Ti-Ni-Si interlayer, an interlocking interface structure was obtained by a two-step technique involving pre-oxidation and hot-pressing. The results show that a porous layer could be obtained on the surface of C/C composites by pre-oxidation treatment at 1173 K in air and that an interlocking C/C-Ti-Ni-Si interface was formed after hot-pressing. With increasing pre-oxidation time, the average shear strength of the Ti-Ni-Si joint initially increased and then decreased. After a pre-oxidation time for 3 min, the shear strength of the joint reached a maximum of 29.81±1.76 MPa, which is 20.1% higher than the joint strength obtained without pre-oxidation. The improvement in the shear strength is primarily attributed to the ‘pinning effect’ generated by the interlocking interface, which could play a positive role in extending the crack propagation path by inducing crack deflection. [ABSTRACT FROM AUTHOR]