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To protect carbon/carbon composites against oxidation and ablation, a Fe 2 O 3 modified ZrB 2 –SiC–Si coating was prepared by a two-step pack cementation. The microstructure, oxidation and ablation resistance of the Fe 2 O 3 modified ZrB 2 –SiC–Si coating were studied. The results showed that the Fe 2 O 3 modified ZrB 2 –SiC–Si coating had good oxidation and ablation resistance, and could effectively protect the carbon/carbon composites from oxidation at 1773 K for 150 h and ablation at 2573 K for 60 s. The excellent oxidation and ablation resistance of the coating were mainly attributed to its dense and large amount of ZrB 2 in the coating. [ABSTRACT FROM AUTHOR]

Abstract: ZrB2–SiC–Si/B-modified SiC coating was prepared on the surface of carbon/carbon (C/C) composites by two-step pack cementation. The coating could efficiently provide protection for C/C composites from oxidation and ablation. The improvement of oxidation resistance was attributed to the self-sealing property of the multilayer coating. A dense glassy oxide layer could afford the high temperature up to 2573K and efficiently protect C/C composites from ablation. [Copyright &y& Elsevier]

Abstract: A MoSi2–CrSi2–Si/B-modified SiC coating was prepared by two-step pack cementation. The coating could protect C/C composites from oxidation at 1173K for 600min and at 1873K for 300h and from erosion at 1873K for 50h, respectively. B2O3 oxidised from B-modified SiC layer could seal cracks at intermediate temperatures, resulting in improving the oxidation resistance of the coating. Large cracks caused by the bending of the coated specimens and excessive local stress resulted in the fracture of the tested specimens. [Copyright &y& Elsevier]

Abstract: To extend the oxidation protective temperature range of coating for carbon/carbon (C/C) composites, a SiC/ZrB2–SiC/SiC multilayer coating was prepared by a three-step method of pack cementation, slurry and chemical vapor deposition. The prepared coating is composed of three layers with about 150μm in thickness. It can protect C/C composites from oxidation for more than 300h at 1173K which is attributed to the oxidation ability of ZrB2. The coating can also effectively protect C/C composites from oxidation at 1773K for 217h which is due to the SiO2–ZrSiO4 compound glass during oxidation test. [Copyright &y& Elsevier]

Abstract: A MoSi2–CrSi2–SiC–Si multi-component coating was prepared on the surface of carbon/carbon (C/C) composites by a two-step pack cementation method. The microstructure, oxidation behavior and mechanical properties of the coating were studied. These results show that the multi-component coating could protect the C/C composites from oxidation in air at 1873K for 300h and withstand 30 thermal cycles between 1873K and room temperature, respectively. The mass loss and mechanical property loss of the coated C/C composites are considered due to the worse fluidity of SiO2 at intermediate temperatures and the thermal mismatch between the coating and C/C composites. [Copyright &y& Elsevier]

Abstract: To protect carbon/carbon (C/C) composites against oxidation, a Si–Mo coating was prepared on C/SiC-coated C/C composites by a simple slurry method. The microstructure of the coating was characterized by X-ray diffraction, scanning electron microscopy and Raman spectra. Results showed that the coating was mainly composed of SiC, MoSi2 and Si. It could protect C/C composites from oxidation at 1873K in air for 300h and withstand 13 thermal cycles between room temperature and 1873K. The excellent oxidation and thermal shock resistance of the coating was attributed to the formation of dense SiO2 glass at high temperature. The volatilization of MoO3 and SiO2 at 1873K was the main reason of the weight loss of the coated C/C composites. [Copyright &y& Elsevier]

Abstract: Multi-layer MoSi2–CrSi2–Si anti-oxidation coatings with different compositional ratios were prepared on the surface of SiC coated carbon/carbon (C/C) composites by a two-step pack cementation method. The microstructure and anti-oxidation performance of the coating were studied. The results show that the multi-layered coatings could protect the C/C composites from oxidation in air at 1773K for 1000h or 1873K for 750h, respectively. The anti-oxidation performance of the multi-layer MoSi2–CrSi2–Si coating is mainly attributed to their dense and microcrack-free structure, appropriate thermal expansion coefficient and the well dispersed MoSi2 and CrSi2 in the coating. [Copyright &y& Elsevier]

Abstract: To protect carbon/carbon (C/C) composites against oxidation, a SiC nanowire-toughened MoSi2–SiC coating was prepared on them using a two-step technique of chemical vapor deposition and pack cementation. SiC nanowires obtained by chemical vapor deposition were distributed random-orientedly on C/C substrates and MoSi2–SiC was filled in the holes of SiC nanowire layer to form a dense coating. After introduction of SiC nanowires, the size of the cracks in MoSi2–SiC coating decreased from 18±2.3 to 6±1.7μm, and the weight loss of the coated C/C samples decreased from 4.53% to 1.78% after oxidation in air at 1500°C for 110h. [Copyright &y& Elsevier]

Abstract: A MoSi2–CrSi2–Si multi-composition coating was prepared on the surface of SiC coated carbon/carbon (C/C) composites by pack cementation in argon. The crystalline structure of the multi-composition coating was measured by X-ray diffraction. The morphology and element distribution were analyzed by scanning electron microscopy and energy dispersive spectroscopy, respectively. The isothermal oxidation and erosion resistance of the multi-layer coating were investigated in electrical furnace and high temperature wind tunnel, respectively. These results indicated that the weight loss of the coated C/C composites was only 0.8% after oxidation in air at 1873K for 500h, and the sample was fractured after erosion at 1873K for 32h in wind tunnel. The weight loss of the coated C/C composites was considered due to the excessive depletion of the outer coating and the appearance of defects in the coating. The mismatch of thermal expansion coefficient between the multi-layer coating and C/C composites caused excessive local stress and resulted in the fracture of the coated C/C composites. [Copyright &y& Elsevier]

In order to protect carbon/carbon (C/C) composites against oxidation, a Si–Mo–W coating was prepared on the surface of SiC-coated C/C composites by a simple reaction method. The microstructures of the as-received coating were characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy analyses. The results show that the SiC/Si–Mo–W coating can protect C/C composites from oxidation in air at 1673 K for 220 h with a mass loss of 0.003%, and at 1773 K for 252 h with a mass gain of 1.56%. The excellent oxidation-resistant property of the SiC/Si–Mo–W coating at 1673–1773 K is attributed to the formation of SiO2 film on the coating surface. The mass loss of the coated C/C composites during the oxidation test at 1873 K in air primarily resulted from the reaction of C/C substrate and oxygen diffusing through the penetration cracks in the coating. [ABSTRACT FROM AUTHOR]

In order to protect carbon/carbon (C/C) composites from oxidation at 1700°C, a MoSi2–SiC–Si/MoSi2 coating was prepared on the surface of these composites by a simple and effective method. The MoSi2–SiC–Si inner layer was obtained by pack cementation, and the MoSi2 outer layer was prepared by slurry coating using silicon-sol as the caking agent. The microstructures of the as-prepared coating were examined by X-ray diffraction and scanning electron microscope. Oxidation test shows that, the as-received coating can protect C/C composites from oxidation for more than 107 h at 1700°C in air. The excellent anti-oxidation ability of this coating is attributed to its dense structure and the formation of the SiO2 film on the coating surface during oxidation. [ABSTRACT FROM AUTHOR]

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: Yttrium silicate coatings with an outer glass sealant for SiC pre-coated carbon/carbon (C/C) composites were prepared by a novel in situ formation method using Si and Y2O3 as starting materials in an oxidation atmosphere. The structures of the coatings were characterized by XRD and SEM analyses. Oxidation behavior of the multi-layer-coating-coated C/C composites was investigated. It showed that the as-prepared multi-layer coating could protect C/C composites from oxidation at 1600 °C in air for 202 h with a weight loss of 2.87×10−3g/cm2. The oxidation weight losses of the coated C/C with time accorded with linear and parabolic rule in the temperature range 400–800 and 1300–1600 °C, respectively, and the corresponding oxidation activation energy of the coated C/C composites are 99.6 and 112 kJ/mol, respectively. [Copyright &y& Elsevier]

Abstract: In order to improve the ablation resistance of carbon/carbon (C/C) composites, a ZrC nanostructured coating was prepared on C/C composites by chemical vapor deposition. Results show that the coating contains ZrC grains with the size of 20–30nm and the structure displays a high consistent orientation. This nanostructured coating has improvements in linear and mass ablation rates of 50.7% and 42.1% compared with those of the conventional ZrC coating. The good ablation resistance could be attributed to the efficient prevention of the coating cracking and the formation of the dense ZrO2 layer during ablation. [Copyright &y& Elsevier]

Abstract: A C/SiC/Mo–Si–Cr multilayer coating for carbon/carbon (C/C) composites against oxidation at high temperature was prepared by pack cementation and slurry method. Oxidation test results showed that the coating could protect C/C composites from oxidation at 1873K in air for 300h and withstand 40 thermal cycles between 1873K and room temperature. The coating remained intact during the two kinds of tests and no obvious failure was found. The good oxidation and thermal shock resistance of the coating is attributed mainly to the formation of dense glass film on the coating during the oxidation test. [Copyright &y& Elsevier]

Abstract: In order to prevent carbon/carbon (C/C) composites from oxidation at 1773 K, a Si–W–Mo coating was prepared on the surface of SiC coated C/C composites by a simple pack cementation technique. The microstructures and phase composition of the as-received multi-coating were examined by SEM, XRD and EDS. It was seen that the compact multi-coating was composed of α-SiC, Si and (W x Mo1− x )Si2. Oxidation behaviour of the SiC/Si–W–Mo coated C/C composites was also studied. After 315 h oxidation in air at 1773 K and thermal cycling between 1773 K and room temperature for 17times, no weight loss of the as-coated C/C composites was measured. The excellent anti-oxidation ability of the multi-coating is attributed to its dense structure and the formation of the stable glassy SiO2 film on the coating surface during oxidation. [Copyright &y& Elsevier]

A new type of oxidation-protective multi-composition coating for carbon/carbon (C/C) composites has been produced by a pack cementation technique in an argon atmosphere. XRD analyses shows that the phases of the composite coating are composed of Al2O3, mullite, SiC and Al4SiC4, and the bonding layer between the coating and C/C composites are composed of Al4C3, SiC and Al4SiC4. It is found by SEM surface observation and EDS area scanning analyses that the coating has two kinds of surfaces that are distinctly different in element content of Si and C. In the meantime, cross-section SEM observation of the coating also displays a dense microstructure. Oxidation test shows that the as-prepared coating characterized by excellent thermal shock resistance on the surface of C/C composites during exposure to an oxidizing atmosphere at 1773 K could effectively protect the C/C composites from oxidation for 41 h. [Copyright &y& Elsevier]

To improve the bonding strength and thermal shock resistance of SiC coating for C/C–ZrC–SiC composites, a transition layer with mechanical interlocking structure was constructed at the interface by pre-oxidation treatment and chemical vapor deposition. For the coated specimens with pre-oxidation treatment at 1073 K for 5 min, the bonding strength increased from 2.0 to 4.0 N, and the mass loss percentage decreased by 52.5% after 12-time thermal cycling between 1773 K and room temperature in air. The transition interlocking structure can effectively alleviate the mismatch between the coefficients of thermal expansion of SiC coating and C/C–ZrC–SiC substrate, improving the bonding strength and thermal shock resistance. As the pre-oxidation time increases, a rugged and loose ZrO 2 –SiO 2 layer will be formed at the interface, which is disadvantageous to the bonding strength and thermal shock resistance of SiC coating for C/C–ZrC–SiC composites, and results in the debonding and collapse of the coating. [ABSTRACT FROM AUTHOR]

Abstract: A C/SiC oxidation resistance coating was prepared on carbon/carbon (C/C) composites by slurry and pack cementation. The microstructure, oxidation resistance and mechanical properties of C/SiC coating prepared from 1773 to 2573K were investigated. With the increase of the preparation temperature, the oxidation resistance of C/SiC coating increases, however, the flexure strength decreases gradually. The preparation of C/SiC coating on C/C composites results in the fracture behavior of C/C composites changing from pseudo-plastic to brittle failure model. The decrease of flexure strength is mainly attributed to the decrease of C/C matrix’ flexure strength at high temperature. [Copyright &y& Elsevier]

[Display omitted] • The damaged SiC coated C/C composites was repaired successfully. • A Mo-modified Si-SiC coating was prepared on C/C composites by laser-inducing. • The free Si of the Si-SiC coating was decreased significantly by Mo-modification. • The interface bonding of the coating modified with 10 wt% Mo was the best. • The oxidation resistance of the repaired coating was improved significantly. As the thermal structural component of aircraft, SiC coated C/C composites will fail and cause catastrophic consequences once the SiC anti-oxidation coating is damaged. Therefore, it is extremely important to develop a coating repair system with excellent oxidation protection performance. In this study, a Mo-modified Si-SiC coating was prepared by laser-inducing to repair the damaged SiC coated C/C composites. Thermal shock test between room temperature and 1773 K was conducted to study the interface bonding and 1773 K cyclic oxidation test was performed to examine the repair effect. With 10 wt% Mo-modification by laser-inducing, MoSi 2 precipitated at the interfaces while the interface bonding was not weaken. The decreased free Si, densified structure of coating and enhanced self-healing ability, which were obtained by modifying, contributed to reduce the mass loss after oxidation by ∼ 70% compared with the damaged sample without repairing. [ABSTRACT FROM AUTHOR]

Abstract: A hot-pressing reactive sintering (HPRS) technique was explored to prepare SiC coating for protecting carbon/carbon (C/C) composites against oxidation. The microstructures of the coatings were analyzed by X-ray diffraction and scanning electron microscopy. The results show that, SiC coating obtained by HPRS has a dense and crack-free structure, and the coated C/C lost mass by only 1.84wt.% after thermal cycles between 1773K and room temperature for 15 times. The flexural strength of the HPRS-SiC coated C/C is up to 140MPa, higher than those of the bare C/C and the C/C with a SiC coating by pressure-less reactive sintering. The fracture mode of the C/C composites changes from a pseudo-plastic behavior to a brittle one after being coated with a HPRS-SiC coating. [Copyright &y& Elsevier]