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.     

Ablation behavior of C/SiC with YSZ and ZrB2 coatings under high-energy laser irradiation

Carbon fiber-reinforced silicon carbide (C/SiC) composites are important candidates for laser protection materials. In this study, ablation mechanism of C/SiC coated with ZrO₂/Mo and ZrB₂–SiC/ZrO₂/Mo under laser irradiation was studied. ZrB₂–SiC multiphase ceramic and ZrO₂ ceramic were successfully coated on C/SiC composite by atmospheric plasma spraying technology with Mo as transition layer. Phase evolution and morphology of composite were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Moreover, ablation behavior of the composite was investigated by laser confocal microscopy. Results showed that ablation mechanism of C/SiC composite was controlled by phase transformation, thermal reaction, and thermal diffusion, with solid–liquid transition of ZrB₂ and ZrO₂ being dominant factor. Endothermic reaction and good thermal diffusivity of coatings were also important factors affecting ablation performance. Reflectivity effect of ZrO₂ coating was limited under high-energy laser irradiation. Compared with ZrO₂/Mo single-phase-monolayer coating, designed ZrB₂–SiC/ZrO₂/Mo coating showed better ablation performance, and breakdown time of C/SiC increased from 10 to 40 s. The depletion of liquid phase in molten pool was identified as an important factor responsible for rapid failure of C/SiC. The coating failed when the entire liquid phase was consumed within molten pool, followed by rapid damage of C/SiC substrate. Results of this study can provide theoretical guidance and research ideas for design and application of laser protective materials.     

Influence of ZrO2 Content on the Performances of BN‐ZrO2‐SiC Composites for Application in the Steel Industry

BN‐ZrO₂‐SiC composites were fabricated with different ZrO₂ contents ranging from 0 to 40 vol%. The mechanical properties and corrosion resistance against molten steel increase with increasing ZrO₂ content, while thermal shock resistance decreases gradually. When ZrO₂ content is 40 vol%, the flexural strength is 346 MPa and corrosion depth is 254 μm. The improved corrosion resistance is attributed that the corrosion layer formed by residual ZrO₂ hinders molten steel penetration. Nevertheless, composite with 40 vol% ZrO₂ shows a sharp decline in residual flexural strength when temperature difference is more than 400°C and critical temperature difference is 520°C.     

The effect of TIO2 filler content on the mechanical,thermal, and tribological properties of TiO2/PPS composites

In an attempt to overcome existing limited studies about the residual flexural properties of solid particle eroded particle reinforced thermoplastic composites, this study is aimed to determine particularly titanium dioxide (TiO₂) particle concentrations (0, 5, 10, 15, 20, and 25 wt %) effects on the flexural and solid particle erosive wear properties of TiO₂ particle reinforced polyphenylenesulphide (PPS) composites. In addition, thermal and viscoelastic properties of PPS composites were also studied by using Dynamic Mechanical Analysis (DMA) and Thermogravimetric Analysis (TGA) methods. TiO₂ reinforced PPS composite samples were prepared by using a twin screw extruder and injection molding machines. Subsequently, composite samples were eroded under various impingement angles in specially designed erosion test rig by using silica particles and then flexural tests were performed. It was found that increase of particle concentrations in PPS improves composite's stiffness. Besides, maximum flexural and residual flexural strength were obtained at 10 wt % particle concentrations for both uneroded and eroded composites. The erosion rate of composite was increased with augmentation in TiO₂ concentration. Moreover, TGA analysis indicated that remarkable results on thermal stability were obtained. The effects of TiO₂ reinforcement on the results of DMA were also discussed. POLYM. COMPOS., 34:1591–1599, 2013. © 2013 Society of Plastics Engineers     

Effect of zirconia on ablation mechanism of asbestos fiber/phenolic composites in oxyacetylene torch environment

Micron-size zirconium oxide (ZrO₂) was used to improve the thermal stability and ablation properties of asbestos fiber/phenolic composites and to reduce their final cost. ZrO₂/asbestos/phenolic composites were prepared in an autoclave by the curing cycle process. The densities of the composites were in the range of 1.64–1.82 g/cm³. The ablation properties of composites were determined by oxyacetylene torch environment and burn-through time, erosion rates and back surface temperature in the first required 20 s. To understand the ablation mechanism, the morphology and phase composition of the composites were studied by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Thermal stability of the produced materials was estimated by means of thermal gravimetric analysis, in air which consisted of dynamic scans at a heating rate of 10 °C/min from 30 to 1000 °C with bulk samples of about 23±2 mg. The thermal stability of the composites was enhanced by adding ZrO₂. The results showed that the linear and mass ablation rates of the composites after adding 14 wt% ZrO₂ decreased by 58% and 92%, respectively. The back surface temperature of a sample with 14% zirconia was 49% lower than that of pure composite. The SEM studies showed that, modified composites displayed much lower porosity than that of non-modified composite and the destruction of asbestos fibers was very low. On the other hand, it appeared that a thin melted layer of ZrO₂ covered the surfaces of zirconia-containing 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.     

Novel one-step formed composite reinforcement of "Spider web like" SiCnw networks and "Z-pins like" SiC rods for ablation resistance improvement of C/C-ZrC-SiC

A novel composite reinforcement with horizontal multilayer "Spider web like" SiC nanowire networks and vertical interconnected "Z-pins like" SiC rods was designed and prepared by facile one-step figuration. The linear ablation rate of "Spider web like" SiC nanowire networks and "Z-pins like" SiC rods collectively reinforced C/C-ZrC-SiC composites at 2610 ± 20 ℃ was 0.4 ± 0.03 μm/s with a 74.19 % reduction. The improved ablation resistance was attributed to a denser gradient oxide layer composed of central ZrO₂ layer, transitional ZrO₂-SiO₂ layer and marginal SiO₂ layer generated under the initial sticky net effect from SiCnw networks and subsequent oxide compensation from "Z-pins like" SiC rods.     

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.     

Zirconium nitride nano-particulate reinforced Alon composites: Fabrication, mechanical properties and toughening mechanisms

Aluminium oxynitride (Alon) exhibits excellent stability, high rigidity and good thermal shock resistance, but it has relatively low strength and poor fracture toughness. The aim of this investigation was to develop a new type of zirconium nitride (ZrN) nano-particulate reinforced Alon composites via a change of ZrO₂ nano-particles during sintering. A reduction of porosity and grain size was observed in the composite. With increasing amount of ZrN nano-particles up to 2.7%, the relative density, hardness, Young's modulus, flexural strength, and fracture toughness all increased. When the ZrN nano-particles exceeded 2.7%, while the flexural strength and fracture toughness decreased slightly, the density, hardness and Young's modulus continued to increase. Different toughening mechanisms including crack bridging, crack branching and crack deflection were observed, thus effectively increasing the crack propagation resistance and leading to a considerable improvement in the flexural strength and fracture toughness of the composites.     

Microstructure and ablation property of gradient ZrCSiC modified C/C composites prepared by chemical liquid vapor deposition

Chemical liquid vapor deposition was adopted to fabricate gradient ZrCSiC modified C/C composites, and the microstructure and ablation resistance were studied. Results displayed the content of SiC decreased from the composites edge to the center but that of ZrC increased, indicating SiC and ZrC ceramics have the gradient distribution in the composites. The gradient composites possessed a low CTE and high thermal conductivity. The low CTE restricted the formation and expansion of defects, which could slow the oxygen diffusion in the composites. The high thermal conductivity could transfer the heat quickly in ablation process, which reduced the heat accumulation on the ablation surface and weakened the thermal erosion. Therefore, the gradient composites possessed an outstanding anti-ablation property at two heat fluxes. Compared with the uniformed distribution composites, the linear and mass ablation rates of the gradient composites decreased by 60.9% and 66.7% at heat flux of 2.38 MW/m² and decreased by 55.9% and 67.2% at heat flux of 4.18 MW/m². Because of the gradient distribution, porous ZrO₂ coating, ZrO₂SiO₂ coating and SiO₂ coating with SiO₂ nanowires were generated on the ablation center, ablation transition zone and ablation edge, respectively. These coatings isolated the sample surface from the flame and inhibited the transport of oxygen into the sample inner.     

Application of SiO2-coated SiC powder in stereolithography and sintering densification of SiC ceramic composites

Stereolithography additive manufacturing of SiC ceramic composites has received much attention. However, the forming efficiency and mechanical properties of their products need to be improved. This study aimed to prepare SiC ceramic composites with complex shapes and high flexural strength using a combination of digital light processing (DLP) and reactive solution infiltration process (RMI). A low-absorbance SiO₂ cladding layer was formed on the surface of SiC powder through a non-homogeneous precipitation process. With the densification of the cladding layer at high temperatures, SiO₂-coated SiC composite powder was used to formulate a photosensitive ceramic slurry with a solid content of 44 vol%. The resulting slurry exhibited a considerable improvement in curing thickness and rate and was used to mold ceramic green body with a single-layer slicing thickness of 100 μm using DLP. The ceramic blanks were then sintered and densified using a carbon thermal reduction combined with liquid silica infiltration (LSI) process, resulting in SiC ceramic composites with a density of 2.87 g/cm³ and an average flexural strength of 267.52 ± 2.5 MPa. Therefore, the proposed approach can reduce the manufacturing cycle and cost of SiC ceramic composites.     

Two-step method to deposit ZrO2 coating on carbon fiber: Preparation,characterization, and performance in SiC composites

Recently, ceramic matrix composites reinforced by short carbon fibers (CFs) attracted increasing attentions. To further improve mechanical properties and oxidation resistances, CFs were subjected to oxidation and acidification followed by sol-gel dip-coating to deposit ZrO₂ on their surfaces. ZrO₂-C_f/SiC composites were fabricated by joint hot compression molding and sintering, compared to C_f/SiC and SiC prepared by the same method. Microstructural analyses indicated that ZrO₂ coatings were successfully deposited on CF surfaces, formed strong bonding and interfaces between CF and the matrix. Meanwhile, CFs were found uniformly distributed in SiC matrix with random orientations. Flexural curves of ZrO₂-C_f/SiC and C_f/SiC revealed the presence of “false plasticity” regions after sharp drops, which were quite different from brittle flexural behavior of SiC ceramic. Compression strength of the three samples showed step-up growth. ZrO₂-C_f/SiC exhibited the highest value, indicating the introduction of CFs and ZrO₂ coatings do have great influence on mechanical performances. After heat treatment, ZrO₂-C_f/SiC exhibited better oxidation resistance than C_f/SiC, with weight loss ratios estimated to ??3.76% and ??6.43%, respectively. These improved properties indicated that ZrO₂-C_f/SiC would be excellent alternatives to other existence materials under ultra-high temperature environments.     

High-temperature flexural strength of I-CVI processed Cf/SiC composites with variable interphases

The effect of single-layer pyrocarbon (PyC) and multilayered (PyC/SiC)_n=4 interphases on the flexural strength of un-coated and SiC seal-coated stitched 2D carbon fiber reinforced silicon carbide (C_f/SiC) composites was investigated. The composites were prepared by I-CVI process. Flexural strength of the composites was measured at 1200 °C in air atmosphere. It was observed that irrespective of the type of interphase, the seal coated samples showed a higher value of flexural strength as compared to the uncoated samples. The flexural strength of 470 ± 12 MPa was observed for the seal coated C_f/SiC composite samples with multilayered interphase. The seal coated samples with single layer PyC interphase showed flexural strength of 370 ± 20 MPa. The fractured surfaces of tested samples were analyzed in detail to study the fracture phenomena. Based on microstructure-property relations, a mechanism has been proposed for the increase of flexural properties of C_f/SiC composites having multilayered interphase.     

Investigation of Characterization and Mechanical Performances of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and SiC Reinforced PA6 Hybrid Composites

In this study, the influence of different weight percentages of alumina oxide (Al₂O₃) and silicon carbide (SiC) reinforcement on the mechanical properties of Polyamide (PA6) composite is investigated. Test specimens of pure PA6, 85 wt% PA6 + 10 wt% Al₂O₃ + 5 wt% SiC and 85 wt% PA6 +10 wt% SiC + 5 wt% Al₂O₃ are prepared using an injection molding machine. To investigate the mechanical behaviors tensile test, impact test, flexural test, and hardness test were conducted in accordance with ASTM standards. Experimental results indicated that the mechanical properties, such as tensile, impact, hardness, and flexural strength were considerably higher than the pure PA6. The tensile fracture morphology and the characterization of PA6 hybrid composites were observed by scanning electron microscope and Fourier transform infrared spectroscopic method. Further, thermogravimetric analysis confirms the thermal stability of PA6 hybrid composites. The reinforcing effects of Al₂O₃ and SiC on the mechanical properties of PA6 hybrid composites were compared and interpreted in this paper. Improved mechanical and thermal characteristics were observed by the addition of small amount of Al₂O₃ and SiC simultaneously reinforced with the pure PA6.     

A novel B–Si–Zr hybridized ceramizable phenolic resin and the thermal insulation properties of its fiber-reinforced composites

A novel B–Si–Zr hybridized ceramicizable resin(BSZ-PR) was fabricated by chemical reaction of boric acid, zirconium hydroxyl-containing polyhedral oligomeric silsesquioxane(Zr-POSS) and phenolic. The incorporation of boric acid and Zr-POSS improved the thermal stability of the resin effectively, and the residual carbon rate increased to 72.63% at 800 °C under nitrogen atmosphere. The flexural strength of carbon fiber/BSZ-PR and high silica fiber/BSZ-PR composites were increased by 25.7% and 175.5%, and linear ablation rates were reduced by 37% and 44.75%, respectively. It was discovered that the ceramic structures such as SiO₂, ZrO₂ and SiC can be formed at high temperatures as well as under extreme ablative conditions from both BSZ-PR and its fiber-reinforced composites, which may be the key to the improved thermal, ablative properties.     

Fabrication and characterization of novel zirconia filled glass fiber reinforced polyester hybrid composites

Novel hybrid glass fiber reinforced polyester composites (GFRPCs) filled with 1‐5 wt % microsized zirconia (ZrO₂) particles, were fabricated by hand lay‐up process followed by compression molding and evaluated their physical, mechanical and thermal behaviors. The consumption of styrene in cured GFRPCs was confirmed by Fourier transform infrared spectroscopy. The potential implementation of ZrO₂ particles lessened the void contents marginally and substantially enhanced the mechanical and thermal properties in the resultant hybrid composites. The GFRPCs filled with 4 wt % ZrO₂ illustrated noteworthy improvement in tensile strength (66.672 MPa) and flexural strength (67.890 MPa) while with 5 wt % ZrO₂ showed 63.93% rise in hardness, respectively, as compared to unfilled GFRPCs. Physical nature of polyester matrix for composites and an improved glass transition temperature (T_g) from 103 to 112 °C was perceived by differential scanning calorimetry thermograms. Thermogravimetric analysis revealed that the thermal stability of GFRPCs was remarkably augmented with the addition of ZrO₂. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43615.     

A new route to fabricate SiB4 modified C/SiC composites

In order to improve the oxidation and thermal shock resistance of 2D C/SiC composites, dense SiB₄–SiC matrix was in situ formed in 2D C/SiC composites by a joint process of slurry infiltration and liquid silicon infiltration. The synthesis mechanism of SiB₄ was investigated by analyzing the reaction products of B₄C–Si system. Compared with the porous C/SiC composites, the density of C/SiC–SiB₄ composites increased from 1.63 to 2.23 g/cm³ and the flexural strength increased from 135 to 330 MPa. The thermal shock behaviors of C/SiC and C/SiC–SiB₄ composites protected with SiC coating were studied using the method of air quenching. C/SiC–SiB₄ composites displayed good resistance to thermal shock, and retained 95% of the original strength after being quenched in air from 1300 °C to room temperature for 60 cycles, which showed less weight loss than C/SiC composite.     

ZrO2f-coated Cf hybrid fibrous reinforcements and properties of their reinforced ceramicizable phenolic resin matrix composites

Carbon fiber-reinforced ceramicizable phenolic resin matrix composites have been widely used in the field of thermal protection materials. In this paper, the ZrO_2f-coated C_f (ZrO_2f/C_f) hybrid fibrous reinforcements were designed to improve oxidation resistance of carbon fiber and ceramicizable composites reinforced by ZrO_2f/C_f hybrid fibrous reinforcements were prepared to investigated oxidation resistance and mechanical properties of the composites at high temperature. The results show that ZrO_2f/C_f hybrid fibrous reinforcements have good thermal stability and high oxidation resistance, and its ceramicizable composites have good bending strength at high temperature. Weight loss rate of the composites is only 21 %, and bending strength can be as high as 39 MPa when ablation time was 12 min at 1400 °C.     

Thermal and Mechanical Properties of SiC–TiC0.5N0.5 Composites

SiC–TiC_0.5N_0.5 composites were fabricated from β‐SiC and TiN powders with 2 vol% equimolar Y₂O₃–Sc₂O₃ additives by conventional hot pressing. Thermal and mechanical properties of the SiC–TiC_0.5N_0.5 composites were investigated as a function of initial TiN content. Relative densities of ≥98.9% were achieved for all samples. The addition of a small amount of TiN increased thermal conductivity, flexural strength, and fracture toughness of SiC ceramics. However, further addition of TiN in excess of 10 and 20 vol% deteriorated both thermal conductivity and flexural strength of the composites, respectively. In contrast, the fracture toughness of the composites increased continuously from 4.2 to 6.2 MPa?m^1/2 with increasing initial TiN content from 0 to 35 vol%, due to crack deflection by TiC_0.5N_0.5. The maximum values of thermal conductivity and flexural strength were 224 W/m K for a 2 vol% TiC_0.5N_0.5 and 599 MPa for a 10 vol% TiC_0.5N_0.5 composite.     

Synergistic reinforcement effects of ZrB2 on the ultra-high temperature stability of Cf/SiC composite fabricated by liquid silicon infiltration

A carbon fiber-reinforced silicon carbide (C_f/SiC) composite was fabricated with ZrB₂ via the liquid silicon infiltration (LSI) method. A prepreg was prepared by impregnating the phenolic resin with the ZrB₂ powder. The as-LSIed composites were tested for 5 min with an oxyacetylene torch to evaluate their ablation and oxidation properties under an ultra-high temperature environment. The ZrB₂ powders and SiC matrix between carbon fiber bundles generated a dense ZrO₂-SiO₂ layer, which inhibited further oxygen diffusion into the composite and minimized the ablation and oxidation of the carbon fibers. Weight loss and linear ablation rate were further reduced with the addition of ZrB₂ to the C_f/SiC composite; moreover, the synergistic effect of ZrB₂ and SiC reinforced the ablation properties with increased ZrB₂ content. ZrB₂ also reduced the amount of residual silicon, which was detrimental to the mechanical properties of C_f/SiC composite.