Ablation behavior and mechanism of C/C–ZrC–SiC composites under an oxyacetylene torch at 3000 °C

C/C–ZrC–SiC composites with continuous ZrC–SiC ceramic matrix were prepared by a multistep technique of precursor infiltration and pyrolysis process. Ablation properties of the composites were tested under an oxyacetylene flame at 3000 °C for 120 s. The results show that the linear ablation rate of the composites was about an order lower than that of pure C/C and C/C–SiC composites as comparisons, and the mass of the C/C–ZrC–SiC composites increased after ablation. Three concentric ring regions with different coatings appeared on the surface of the ablated C/C–ZrC–SiC composites: (i) brim ablation region covered by a coating with layered structure including SiO₂ outer layer and ZrO₂–SiO₂ inner layer; (ii) transition ablation region, and (iii) center ablation region with molten ZrO₂ coating. Presence of these coatings which acted as an effective oxygen and heat barrier is the reason for the great ablation resistance of the composites.     

Fabrication and microstructure of 3D Cf /ZrC-SiC composites: through RMI method with ZrO2 powders as pore-making agent

3D C_f/ZrC–SiC composites were prepared by a combination process of slurry infiltration and reactive melt infiltration. ZrO₂ powders and ZrSi₂ alloy, both of which reacted with amorphous carbon, were used as pore-making agent and infiltrator, respectively. After carbothermal reduction at 1650 °C, X-ray diffraction analysis revealed that ZrO₂ powders were completely converted into ZrC by reacting with amorphous carbon, and an in-situ formed submicron porous configuration was observed at the areas containing ZrO₂. Results showed that the matrix in composites mainly consisted of SiC, ZrC and a small quantity of residual metal. SEM and TEM images revealed the formation of ZrC or SiC intergranular particles in the matrix and the characteristic around the residual resin carbon. The composites had a bending strength of 94.89±16.7 MPa, fracture toughness of 11.0±0.98 MPa m^1/2, bulk density of 3.36±0.01 g/cm³, and open porosity of 4.64±0.40%. The formation mechanisms of ZrC–SiC dual matrix and intrabundles׳ structure were discussed in the article.     

Preparation and ablation properties of SiC nanowire-reinforced ZrC–SiC coating-matrix integrated C/C composites

A modification of the precursor infiltration pyrolysis (PIP) method was explored to prepare the integrated doped ceramic matrix and coating by the added SiC nanowires layer and shape-stabilization process. The epitaxial layer of SiC nanowires provided surficial attachments for the precursor. And the shape-stabilization process aggregated loose ceramic particles into a coating. Then the SiC nanowire-reinforced ZrC–SiC coating-matrix integrated C/C (S/SZ-CZ/C) composite was simply prepared by the modified PIP method. The bonding strength between the coating and matrix of the S/SZ-CZ/C composite was improved. Through the ablation test, the mass and linear ablation rate of the S/SZ-CZ/C composite were 0.46 mg/s and 0.67 μm/s, which were 60.34 % and 74.91 % lower than those of the SiC nanowire-reinforced C/C–ZrC (S/CZ/C) composite, respectively. The integration of the coating and matrix enabled the formation of a continuous oxide layer of molten SiO₂ and ZrO₂ in the ablation process, which helped to block the oxygen and heat during the ablation test. Thus the ablation resistance of the materials was systematically and effectively improved.     

Ablative property and mechanism of SiC-CuxSiy modified C/C-ZrC composites prepared by a rapid method

A rapid method was developed to fabricate C/C-ZrC-SiC-Cu_xSi_y composites with low open porosity by precursor infiltration and pyrolysis combining with pressure assisted reactive melt infiltration. Dominant phases of ZrC and SiC with scattered Cu_xSi_y inclusions were present in continuous infiltrated matrix, in which the dimension of submicron ZrC particles displayed gradient change. At ablation test, the heat absorbing effect of Cu_xSi_y-phase and formation of protective ZrO₂-SiO₂ cover enhanced the ablative property of composites for short-time ablation, causing ablation rates of 30 s ablation reached 1.7 ± 0.1 µm/s and 1.3 ± 0.1 mg/s, respectively. As ablation time extends to 60 s, the massive consumption of Si-phase damaged the integrity of surface oxide cover, but the partial melted ZrO₂ improved the viscosity and self-healing ability of ZrO₂-SiO₂ mixture, protecting substrate from further erosion. Thus, ablation rates were increased and decreased to 3.8 ± 0.2 µm/s and 1.2 ± 0.1 mg/s, respectively.     

Microstructure and ablation behavior of SiC coated C/C–SiC–ZrC composites prepared by a hybrid infiltration process

In this study, C/C–SiC–ZrC composites coated with SiC were prepared by precursor infiltration pyrolysis combined with reactive melt infiltration. The pyrolysis behavior of the hybrid precursor was investigated using thermal gravimetric analysis-differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy techniques. The microstructure and ablation behavior of the composites were also investigated. The results indicate that the composites exhibit an interesting structure, wherein a ceramic coating composed of SiC and a small quantity of ZrC covers the exterior of the composites, and the SiC–ZrC hybrid ceramics are partially embedded in the matrix pores and distributed around the carbon fibers as well. The composites exhibit good ablation resistance with a surface temperature of over 2300 °C during ablation. After ablation for 120 s, the mass and linear ablation rates of the composites are 0.0026 g/s and 0.0037 mm/s, respectively. The great ablation resistance of the composites is attributed to the formation of a continuous phase of molten SiO₂ containing SiC and ZrO₂, which seals the pores of the composites during ablation.     

Laser ablation behaviors of vacuum plasma sprayed ZrC-based coatings

ZrC, ZrC-30 vol% SiC, and ZrC-30 vol% TiC coatings were fabricated by vacuum plasma spray and the laser ablation behaviors were evaluated by a CO₂ laser beam under two heat fluxes (15.9 and 25.5 MW/m²). The phase compositions and microstructures of the coatings after ablation were investigated and the effect of SiC and TiC additives was analyzed. The results showed that the ZrC–SiC coating displayed better ablation resistance compared with the ZrC and ZrC–TiC coatings under 15.9 MW/m² heat flux. While the ZrC–TiC coating exhibited the improved ablation resistance under 25.5 MW/m² heat flux. The continuous and integral ZrO₂–SiO₂ scale provided protective effect for the ZrC–SiC coating. A liquid ZrO₂–TiO₂ layer which owned self-healing ability was formed for the ZrC–TiC coating in both heat fluxes. However, the state of the formed liquid, like amount, viscosity, evaporation, and decomposition, was influenced by the environment and was vital for the ablation resistance. This work might give a clue for designing ultrahigh-temperature ceramics as potential laser ablation–resistant coating materials.     

Structural characteristics and ablative behavior of C/C–ZrC–SiC composites reinforced with “Z-pins like” Zr–Si–B–C multiphase ceramic rods

In order to improve the ablation and oxidation resistance of C/C–ZrC–SiC composites in wide temperature domain, “Z-pins like” Zr–Si–B–C multiphase ceramic rods are prepared in the matrix. The influence of different sintering temperatures on the microstructure of ceramic rods and the ablative behavior of heterogeneous composites are studied. The results showed that the ZrB₂ and SiC phases are formed in the sintered matrix, and the increase of sintering temperature is beneficial to improve the density of the ceramic rods. The ablation properties of samples have been greatly improved. The mass and linear ablation rate are 0.8 mg/s and 3.85 μm/s, respectively, at an ablation temperature of 3000 °C and an ablation time of 60 s. After ablation, the matrix surface is covered with SiO₂ and ZrO₂ mixed oxide films. This is due to the preferential oxidation of “Z-pins like” Zr–Si–B–C multiphase ceramic rods in the ablation process, and B₂O₃ melt, SiO₂ melt, borosilicate glass, ZrSiO₄ melt and ZrO₂ oxide film can be generated successively from the low-temperature segment to the ultra-high temperature segment. These oxidation products can be used as compensation oxide melts for the healing of cracks and holes on the matrix surface in different temperature ranges and effectively prevent the external heat from spreading into the matrix. Therefore, C/C–ZrC–SiC composites with “Z-pins like” Zr–Si–B–C multiphase ceramic rods achieve ablation resistance in wide temperature domain.     

Effects of porous C/C density on the densification behavior and ablation property of C/C–ZrC–SiC composites

C/C–ZrC–SiC composites were prepared by precursor infiltration and pyrolysis process using a mixture solution of organic zirconium-containing polymer and polycarbosilane as precursors. Porous carbon/carbon (C/C) composites with density of 0.92, 1.21 and 1.40 g/cm³ were used as preforms, and the effects of porous C/C density on the densification behavior and ablation resistance of C/C–ZrC–SiC composites were investigated. The results show that the C/C preforms with a lower density have a faster weight gain, and the obtained C/C–ZrC–SiC composites own higher bulk density and open porosity. The composites fabricated from the C/C preforms with a density of 1.21 g/cm³ exhibit better ablation resistance with a surface temperature of over 2400 °C during ablation. After ablation for 120 s, the linear and mass ablation rates of the composites are as low as 1.02 × 10⁻³ mm/s and −4.01 × 10⁻⁴ g/s, respectively, and the formation of a dense and continuous coating of molten ZrO₂ solid solution is the reason for their great ablation resistance.     

Ablation behaviors of SiC nanowire-reinforced ZrC-SiC coating-matrix integrated C/C composites with different ratios of precursors

A novel method to prepare a coating on the C/C composite is discussed. The precursor infiltration pyrolysis method is usually applied to prepare interior ceramic matrix, thus SiC nanowires that can absorb the surficial precursor are added to prepare surficial ceramics. The method accomplishes the integration of the coating and the matrix so that no coating peels off after ablation. Moreover, the material with a ZrC/SiC precursor ratio of 5:1 (Z5S1), whose mass and linear rates are 0.47 mg/s and 0.95 µm/s, exhibits the highest overall resistance to ablation. The results demonstrate that higher ZrC content and more uniform phase distribution are beneficial to keep ZrO₂ in solid and form a denser and firmer oxide layer, which is more effective in improving the ablation resistance of the C/C composite.     

Synthesis of ZrC–SiC Powders by a Preceramic Solution Route

Homogenous liquid precursor for ZrC–SiC was prepared by blending of Zr(OC₄H₉)₄ and Poly[(methylsilylene)acetylene]. This precursor could be cured at 250°C and converted into binary ZrC–SiC composite ceramics upon heat treatment at 1700°C. The pyrolysis mechanism and optimal molar ratio of the precursor were investigated by XRD. The morphology and elements analyses were conducted by SEM and corresponding energy‐dispersive spectrometer. The evolution of carbon during ceramization was studied by Raman spectroscopy. The results showed that the precursor samples heat treated at 900°C consisted of t‐ZrO₂ (main phase) and m‐ZrO₂ (minor phase). The higher temperature induced phase transformation and t‐ZrO₂ converted into m‐ZrO₂. Further heating led to the formation of ZrC and SiC due to the carbothermal reduction, and the ceramic sample changed from compact to porous due to the generation of carbon oxides. With the increasing molar ratios of C/Zr, the residual oxides in 1700°C ceramic samples converted into ZrC and almost pure ZrC–SiC composite ceramics could be obtained in ZS‐3 sample. The Zr, Si, and C elements were well distributed in the obtained ceramics powders and particles with a distribution of 100 ~ 300 nm consisted of well‐crystallized ZrC and SiC phases.     

Fabrication and properties of 2D C/C–ZrB2–ZrC–SiC composites by hybrid precursor infiltration and pyrolysis

Abstract

Two dimensional C/C–ZrB₂–ZrC–SiC composites were fabricated through precursor infiltration and pyrolysis process using a mixture of polycarbosilane and ZrB₂ precursor and ZrC precursor as the impregnant. The microstructures, mechanical properties and ablation properties of the composites were investigated. The results showed that the homogeneity of the composite improved on using novel precursors that can dissolve with polycarbosilane through the formation of nanocomposite matrix. The flexural strength and fracture toughness first increased and then decreased on increasing the pyrocarbon content in the composite. Compared with the C/C–SiC composite, the ablation resistance of C/C–ZrB₂–ZrC–SiC composite was greatly enhanced. The mass loss rate and linear recession rate exposed to the plasma torch were 1?7 mg/s and 1?8 μm/s, respectively. The formation of a ZrO₂–SiO₂ glassy layer on the surface significantly contributed to the excellent ablative property of the composite.     

Architectural engineering inspired method of preparing Cf/ZrC–SiC with graceful mechanical responses

Inspired by grouting technique in architectural engineering, an innovative method of slurry injection and vacuum impregnation was put forward to introduce nanosized ZrC–SiC ceramics into PyC modified 3-D needle-punched carbon fiber preform homogeneously and continuously, followed by spark plasma sintering to prepare C_f/ZrC–SiC with graceful mechanical responses. The composite possessed improved fracture toughness and work of fracture at 5.37 ± 0.25 MPa∙m^1/2 and 951 ± 12 J/m², 50% and nearly one order of magnitude higher than those of ZrC–SiC composite, respectively, with rivaling flexural strength at 177 ± 8 MPa synchronously. A graceful fracture mode was embodied in an obviously extended yield plateau with increased failure displacement by 300%. This enhancement was attributed to the uniform and continuous combination of ZrC–SiC with carbon fiber preform as well as protection and interface tailoring from PyC coating. The study offered an easy and effective method of preparing 3-D fiber reinforced ceramic matrix composites.     

Effect of PyC interphase thickness on mechanical and ablation properties of 3D Cf/ZrC–SiC composite

Three-dimensional (3D) C_f/ZrC–SiC composites were successfully prepared by the polymer infiltration and pyrolysis (PIP) process using polycarbosilane (PCS) and a novel ZrC precursor. The effects of PyC interphase of different thicknesses on the mechanical and ablation properties were evaluated. The results indicate that the C_f/ZrC–SiC composites without and with a thin PyC interlayer of 0.15 µm possess much poor flexural strength and fracture toughness. The flexural strength grows with the increase of PyC layer thickness from 0.3 to 1.2 µm. However, the strength starts to decrease with the further increase of the PyC coating thickness to 2.2 µm. The highest flexural strength of 272.3±29.0 MPa and fracture toughness of 10.4±0.7 MPa m^1/2 were achieved for the composites with a 1.2 µm thick PyC coating. Moreover, the use of thicker PyC layer deteriorates the ablation properties of the C_f/ZrC–SiC composites slightly and the ZrO₂ scale acts as an anti-ablation component during the testing.     

Effect of CVI SiC content on ablation and mechanism of C/C-SiC-ZrC-Cu composites

C/C-SiC-ZrC-Cu composites were fabricated by chemical vapor infiltration, precursor infiltration-pyrolysis and vacuum-pressure infiltration methods. During Cu infiltration, the Cu_6·69Si and Cu₃Si new phases are generated through reaction between SiC and molten Cu. The formed Cu_6·69Si, Cu₃Si, ZrC and SiC phases can improve the wettability and interface combination between Cu and the doped carbon matrix. The ablation tests demonstrate that the CVI SiC content significantly affects the structure of protective oxide layer, and induces inverse effects in ablation center at 2500 ^°C and 3000 ^°C. The relatively high CVI SiC content enhances the ablation resistance of composites at 2500 ^°C, but increases the linear ablation rate at 3000 ^°C due to the excessive evaporation and mechanical denudation. During ablation, the formed Si-Zr-C-O layer underneath ablation center and the Si-Cu-C-O layer on transition or marginal areas can prevent carbon matrix from serious oxidation. After ablation for 20 s, the C/C-SiC-ZrC-Cu composites with high CVI SiC content display the best anti-ablation property at 2500 ^°C, and the ablation rates are 3.5 ± 0.1 μm/s and 3.4 ± 0.1 mg/s.     

C/C–ZrC composite prepared by chemical vapor infiltration combined with alloyed reactive melt infiltration

A high performance and low cost C/C–ZrC composite was prepared by chemical vapor infiltration combined with zirconium–silicon (Zr: 91.2 at.%; Si: 8.8 at.%) alloyed reactive melt infiltration. The density of the as-received composite is 2.46 g/cm³ and the open porosity is 5%. Due to the reaction between the pyrolytic carbon and Zr–Si alloy in the composite, ZrC and Zr₂Si phases were formed, the formation and distribution of which were investigated by thermodynamics and phase diagram. The as-received C/C–ZrC composite, with the flexural strength of 239.5 MPa, displayed a pseudo-ductile fracture behavior. Ablation properties of the C/C–ZrC composite were tested by a pulse laser. The linear ablation rate was 0.028 mm/s. A ZrO₂ barrier layer was formed on the ablation surface and the composite presented excellent ablation resistance.     

Effects of zirconium addition on microstructure and ablation resistance of carbon fibre reinforced carbon and SiC ceramic matrix composite prepared by reactive melt infiltration

Abstract

Carbon fibre reinforced C and SiC binary ceramic matrix composites (C/C–SiC) were fabricated by a quick and low cost reactive melt infiltration (RMI) method with Si–Zr25 and Si melts. Effects of zirconium addition in infiltrated Si melt on microstructure and ablation resistance of the composite were investigated. The composite by Si–Zr25 melt infiltration was composed of SiC, ZrC, C and a little amount of ZrSi₂ without residual silicon, overcoming the problem of residual silicon in C/C–SiC composite by Si RMI. Compared with the composite by Si melt infiltration, the ablation resistance of the composite by Si–Zr25 was greatly improved by zirconium addition due to ZrO₂ and SiO₂ protecting layer formed during ablation.     

Ultra-high-temperature ablation behavior of SiC–ZrC–TiC modified carbon/carbon composites fabricated via reactive melt infiltration

To improve the ablation resistance under the ultra-high temperature, the matrix of the carbon/carbon (C/C) composite was modified with a ternary ceramic of SiC–ZrC–TiC via reactive melt infiltration. The obtained ceramic matrix was composed of Zr-rich and Ti-rich solid solution phases of Zr_1−xTi_xC and SiC. This composite exhibited an excellent ablation property at 2500 °C with low mass and linear ablation rates of 0.008 mg s⁻¹ cm⁻² and 0.000 μm s⁻¹, respectively. The ablation mechanism was revealed with various microstructure characterizations and compared with those of C/C–SiC and C/C–TiC composites. Results showed that the degradations of these composites were primarily caused by the loss of the protective oxide scale via volatilization under the ultra-high temperature and flushing by high-speed airflow. The high ablation resistance of the C/C–SiC–ZrC–TiC composite was attributed to the protection of a multiphase oxide scale with high viscosity and low volatility.     

Ablation behavior of a network interlacing ZrC-VC ceramic coating prepared by a pioneering spillover permeation

A novel network interlacing ZrC-VC ceramic coating was prepared by a pioneering spillover permeation. With the increase of Zr content in the blind vias, the content of ZrC in the coating and the density of the coating all decrease. The density of the coating on C/C–ZrC–SiC substrate is obviously higher than that on C/C substrate. The linear ablation rate of the novel ceramic coated C/C–ZrC–SiC composites was ?0.06 μm/s with about 20 and 1.56 times reduction than C/C composites and C/C–ZrC–SiC composites respectively. The improved ablation resistance was attributed to a dense honeycomb ZrO₂ layer filled with liquid vanadium oxide in the ablation center and the improved thermal radiation.     

Design and preparation of composite coatings with increased reflectivity under high-energy continuous wave laser ablation

High-energy continuous wave (CW) laser ablation can cause severe damage to structural materials in an extremely short time, which generates considerable concern in terms of material safety. For the purpose of reducing or even eliminating such laser-induced damage, a novel composite coating consisting of a boron-modified phenolic formaldehyde resin incorporating ZrC and SiC has been designed and prepared. The experimental results reveal that ZrC and SiC are rapidly oxidized to ZrO₂ and SiO₂ respectively, leading to the formation of a white ceramic layer consisting of ZrO₂ particles and melted SiO₂. After ablation at 1000 W/cm² for 50 s, elemental analysis indicates that no Si can be found in the central ablation zone because of gasification. A relatively compact ZrO₂ layer is formed through the sintering of adjacent ZrO₂ particles, which effectively improves the reflectivity of the coating from 7.3% (before ablation) to 63.5% (after ablation). The high reflectivity greatly reduces the absorption of laser energy. In addition, no obvious ablation defects are observed in the composite coating. The excellent anti-laser ablation performance of the coating makes it a promising system for protecting a material against the effects of long-term CW laser ablation.     

Synthesis,Characterization, and Microstructure of ZrC/SiC Composite Ceramics via Liquid Precursor Conversion Method

The ceramic precursor for ZrC/SiC was prepared via solution‐based processing using polyzirconoxane, polycarbosilane, and divinylbenzene. The precursor could be transformed into ZrC/SiC ceramic powders at relative low temperature (1500°C). The cross‐linking process of precursor was studied by FT–IR. The conversion from precursor into ceramic was investigated by TGA, XRD. The ceramic compositions and microstructures were identified by element analysis, Raman spectra, SEM, and corresponding EDS. The results indicated that the ceramic samples remained amorphous below 1000°C and t–ZrO₂ initially generated at 1200°C. Further heating to 1400°C led to the formation of ZrC and SiC with the phase transformation of ZrO₂ and almost pure ZrC/SiC could be obtained upon heat‐treatment at 1500°C. During heat treatments, the ceramic sample changed from compact to porous due to carbothermal reduction. The ceramic powders with particle size of 100 nm~400 nm consisted of high crystalline degree ZrC and SiC phases, and Zr, Si, C were well distributed at the different sites in ceramic powders. The free carbon content was lowered to 1.60 wt% in final ZrC/SiC composite ceramics.