Precursor Infiltration And Pyrolysis Research Articles

Continuous Carbon Fiber Reinforced SiC Ceramic Matrix Composites by Vertical Fiber Laying Combined with Material Extrusion 3D Printing

3D printing is reported in the fabrication of continuous carbon fiber reinforced silicon carbide ceramic matrix composites (Cf/SiC CMCs), however, there are layer defects in the 3D printed materials, manifested as weak mechanical properties between layers. Therefore, it is essential and urgent to study how to improve the mechanical properties of 3D printed Cf/SiC CMCs at the layers. In this article, a novel processing technique which combined vertical fiber laying method with material extrusion (ME) 3D printing is proposed to manufacture Cf/SiC CMCs. A self‐developed 3D printing fixed‐axis rotating lifting synchronizer is adopted. The vertical fiber laying of continuous carbon fibers (Cf) in Z‐direction is introduced into the X−Y printing plane. Five cycles of precursor infiltration and pyrolysis (PIP) are performed to achieve the densification of Cf/SiC CMCs. The effects of Cf bundle numbers on the flexural strength and fracture work of Cf/SiC CMCs are studied. The best performing composite is Cf/SiC CMC with six bundles, and the maximum flexural strength and fracture work is 63.84 ± 6.62 MPa and 1291.99 ± 161.39 J m−3, respectively. Compared with pure SiC, the fracture work of Cf/SiC CMC with 6 bundles Cf is increased by 2.54 times.

Influence of polycarbosilane composition on the properties of SiC/SiC composite fabricated by precursor infiltration and pyrolysis process

AbstractA series of SiC/SiC composites were fabricated through the precursor infiltration and pyrolysis (PIP) process, using solid polycarbosilane (PCS) and liquid vinyl perhydrogen PCS (VHPCS) solutions as impregnating agents. The physicochemical characteristics of the SiC matrices derived from PCS and VHPCS were investigated and compared. The impact of the PCS composition on the microstructure, density, flexural strength, and modulus of the resulting SiC/SiC composites was also examined. As the VHPCS content increased to 60 wt%, the flexural strength of the composites gradually rose to a peak of 490.9 MPa before decreasing as the VHPCS proportion continued to increase. Meanwhile, the flexural modulus increased continually with the introduction of VHPCS. A possible mechanism is proposed to explain the different variations in flexural strength and modulus, taking into account the ceramic toughening principle and the distinct properties of PCS and VHPCS.

Optimizing the properties of vat photopolymerization 3D-printed SiC ceramics by multi-infiltration

ABSTRACT Digital Light Processing (DLP) technology is a highly effective molding method for creating complex structural parts. However, the low solid content of SiC stereolithography slurry has been found to diminish the mechanical properties of the ceramic, regardless of whether it is sintered by Reactive Melt Infiltration (RMI) or Precursor Infiltration and Pyrolysis (PIP). This poses a significant challenge in improving the mechanical properties of SiC ceramics manufactured through DLP additive manufacturing. In response to this challenge, a novel method of RMI combined with infiltration is proposed in this study. The process involves the filling of the pores of the green body with pyrolytic carbon from PR or pyrolytic SiC from LHBPCS through circular infiltration, effectively increasing the content of SiC in the ceramics after reaction. Notably, the elastic modulus of RM-P2 and RM-L2 samples increased by 37.39% and 33.91%, respectively, demonstrating the potential of this method for preparing ceramics with high SiC content through stereolithography additive manufacturing. This innovative approach holds promise for overcoming the limitations previously associated with SiC ceramics produced through DLP additive manufacturing, opening up new possibilities for the development of high-performance SiC-based components.

Preparation of (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C high‐entropy ceramic nanopowders via liquid‐phase precursor

AbstractUsing citric acid, ethylene glycol, ZrOCl2·8H2O, HfOCl2·8H2O, TiCl4, NbCl5, and TaCl5 as raw materials, the (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C high‐entropy ceramic precursor was prepared by Pechini coordination polymerization method. The precursor and pyrolysis products were analyzed and characterized by different methods. The results showed that the precursor formed a chelate structure, which greatly improved the stability of the precursor, and was clear and transparent with moderate viscosity (30–50 mPa·s). At a low pyrolysis temperature of 1600°C, single‐phase (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C high‐entropy ceramic nanopowders with a ceramic yield of 50.8% can be obtained. The high‐entropy ceramic powder has high purity, a particle size of about 140–200 nm, and uniform element distribution. It is suitable for introduction into fiber‐reinforced ceramic matrix composite by precursor infiltration and pyrolysis (PIP) process.

Microstructure and properties of SiBCN/SiBCN mini‐composites prepared by the precursor infiltration and the pyrolysis process

AbstractSiBCN fiber reinforced SiBCN matrix mini‐composites (SiBCN/SiBCN) as a new type of the ceramic matrix composite were fabricated by precursor infiltration and pyrolysis (PIP) process. Various degumming methods for continuous SiBCN fibers resulted in different properties and surface conditions, further affecting the interfacial bonding strength (IFBS) and mechanical properties of the composites. The relationship between fiber degumming modes, fiber states, and properties of composites was discussed and the strengthening mechanisms of the SiBCN/SiBCN mini‐composites were explored. With a degumming treatment of N,N‐dimethylformamide (DMF) soaking, the flexural strength and modulus of mini‐SiBCN/SiBCN composites achieved 508 ± 68 MPa and 79 ± 12 GPa, respectively. The novel strengthening mechanism of the microcrystalline SiBCN fiber reinforced microcrystalline SiBCN matrix composites will enrich and be helpful to understand the strengthening and toughening mechanisms of ceramic matrix composites.

Fiber-laying-assisted material extrusion additive manufacturing of continuous carbon fiber reinforced SiC ceramic matrix composites

A novel fiber-laying-assisted method for the additive manufacturing of continuous carbon fiber reinforced SiC (Cf/SiC) ceramic matrix composites was proposed. A fiber-laying-assisted material extrusion (ME) additive manufacturing system was developed to enable the introduction of continuous carbon fiber in ceramic components during the part fabrication. In this process, SiC slurry was extruded through a nozzle to build the SiC matrix layer-by-layer. In the case of continuous carbon fiber introduction, the fabrication process was halted after a certain layer was deposited; the continuous carbon fibers were placed in their predetermined locations by the fiber-laying system; and the remaining layers were deposited until the part fabrication was completed. Because the continuous carbon fibers were embedded during the fabrication process, they were fully integrated with the SiC matrix and the problems of traditional continuous fiber introduction could be eliminated. Then, the Cf/SiC green parts were densified by precursor infiltration and pyrolysis (PIP), and the final Cf/SiC composites were obtained. The effects of spacing between neighbor continuous carbon fibers on the microstructure and mechanical properties of Cf/SiC composites were also studied. When the spacing between neighbor continuous fibers was 5.0 mm, the Cf/SiC composite had a maximum bending strength of 217.16 MPa and a maximum fracture toughness of 13.55 MPa m1/2. The continuous carbon fibers improved the fracture toughness of Cf/SiC composites, which was about 3 times better than that of the SiC ceramics without fibers. This work unravels the potential of additive manufacturing of continuous carbon fibers into ceramics.

Cf/(CrZrHfNbTa)C–SiC high-entropy ceramic matrix composites for potential multi-functional applications

In this work, Cf/(CrZrHfNbTa)C–SiC high-entropy ceramic matrix composites with good load-bearing, electromagnetic shielding and ablation resistance were designed and reported for the first time. The composites were fabricated by an efficient combined processing of slurry infiltration lamination (SIL) and precursor infiltration and pyrolysis (PIP). Density and porosity of the as-fabricated composites are 2.72 g/cm3 and 12.44 vol.%, respectively, and the flexural strength is 185 ± 13 MPa. Due to the carbon fiber reinforcement with high conductivity and strong reflection, and high-entropy (CrZrHfNbTa)C ceramic matrix with strong absorbability, the total Electromagnetic interference shielding efficiency (SET) of the composites with a thickness of 3 mm are as high as 88.2 dB and 90 dB respectively in X-band and Ku-band. This means that higher than 99.999999 % electromagnetic shielding is achieved at 8–18 GHz, showing excellent electromagnetic shielding performance. The Cf/(CrZrHfNbTa)C–SiC composites also present excellent ablation resistance, with the linear and mass ablation rates of 0.9 µm/s and 1.82 mg/s after ablation at the heat flux of 5 MW/m2 for 300 s (∼2450 °C). This work opens a new insight for the synergistic design of structural and functional integrated materials with load-bearing, electromagnetic shielding and ablation resistance, etc.

Additive manufacturing Cf/SiC composites with high fiber content by stereolithography combined with precursor infiltration and pyrolysis

A photocurable ceramic precursor slurry with a carbon fiber content of up to 25 vol% was prepared and carbon fiber reinforced SiC ceramic matrix composites (Cf/SiC composites) were successfully fabricated by stereolithography (SLA) combined with precursor infiltration and pyrolysis (PIP). The photocuring ability of the precursor composite slurry was investigated. The calculated result showed that the penetration depth of the slurry prepared with polycarbosilane (PCS) powder and chopped carbon fiber was 59.98 μm, which was suitable for stereolithography. In addition, the bulk density, porosity, flexural strength and micromorphology of the green body, debinding body and final Cf/SiC composites were analyzed in detail. After eight cycles of PIP, the bulk density and flexural strength of final Cf/SiC composites were 2.03 ± 0.04 g/cm3, 109.99 ± 15.05 MPa, respectively. This work provides a reference for additive manufacturing of Cf/SiC composites by stereolithography.

Continuous basalt fibers into fireproof and thermal insulation architectures using an additive manufacturing manipulator

Continuous basalt fiber is an emerging high-performance foundational material that can be widely used in fields such as road construction, energy conservation and environmental protection, aerospace, military equipment, and marine ships. However, it is difficult for existing processing techniques to form continuous basalt architectures with three-dimensional (3D) complex shapes. In addition, the basalt fibers in the architectures are filled with polymers, which cannot fully utilize the performance of basalt fibers. Therefore, here, we report the fabrication of continuous basalt fibers with fireproof and thermal insulation performance through the combination of an Additive manufacturing (AM) manipulator, two-step precursor infiltration and pyrolysis (PIP) processes. Using SiOC ceramics to fill between continuous basalt fibers will help improve the architectures' fire and thermal insulation performance. The continuous basalt fibers coated with thermoplastic polyurethanes (TPU) were processed into 3D architectures under the action of the laser. Through the vacuum infiltration of the SiOC precursor and debinding process, TPU in the 3D architectures was removed. In order to reduce the structural defects generated by the first PIP process, the final part with fireproof and thermal insulation performance was fabricated through the second PIP process. We further demonstrated the final part with excellent fireproof and thermal insulation performance. The final part had a shell temperature of 788.8 ℃ and an internal temperature of about 50 ℃ under the flame spray gun for the 20 s. By replacing polymers with inorganic materials, our basalt architectures exhibit their potential applications in military, aviation, and civil fireproof and thermal insulation equipment.

Efficient fabrication and properties of 2D Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC high-entropy ceramic matrix composites via slurry infiltration lamination combined with precursor infiltration and pyrolysis

In this work, an efficient processing route was developed to fabricate Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composites via slurry infiltration lamination (SIL) combined with precursor infiltration and pyrolysis (PIP). The (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C powder was initially synthesized at 1900 °C. Then the 2D Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composites were obtained via SIL and PIP at temperatures no higher than 1100 °C. The as-fabricated composites show a density of 2.52 g/cm3 and an open porosity of 15.2 vol%, with a bending strength of 255 ± 15 MPa. The 2D Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composites also present excellent ablation resistance, with the linear and mass recession rates of 0.33 µm/s and 0.60 mg/s after ablation at 2000 °C/300 s. This work provides a route for the efficient fabrication of Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composites, and also inspires new strategies to develop high-entropy ceramic matrix composites with high performance.

Ablation behaviour of C/C-HfC-SiC composites prepared by joint route of precursor infiltration and pyrolysis and gaseous silicon infiltration

C/C-SiC-HfC composites were fabricated by using Precursor Infiltration and Pyrolysis (PIP) combined with Gaseous Silicon Infiltration (GSI) process. Different GSI temperatures (1900 ℃ and 2100 °C) were selected. The combination of PIP and GSI could significantly reduce the preparation time of the composites. The morphology displaying a rich-Si layer was formed on the surface of the composites prepared at GSI 2100 °C. Ablation performance of the composites was investigated by oxyacetylene torch. The results showed that after ablation for 120 s, compared to the composites prepared by PIP + 1900 °C GSI, the linear and mass ablation rates of the composites fabricated by PIP + 2100 °C GSI were decreased from 8.05 μm/s to 5.06 μm/s and from 1.61 mg/s to 1.03 mg/s, respectively. The coverage of the rich-Si surface layer promoted the generation of more SiO2 during ablation, which not only benefited for decreasing the surface temperature but also contributed to the formation of H-Si-O glass and the HfO2 skeleton, thus better resisting the denudation of the oxyacetylene torch.

Effect of mullite content on microstructure and ablation behavior of mullite modified C/C-SiC-HfC composites

Mullite modified C/C-SiC-HfC composites were prepared via precursor infiltration and pyrolysis (PIP). The effects of mullite modification with different contents on the composition, microstructure, and ablation behavior of the composites were investigated. Results showed that inadequate and excessive mullite limited the improvement of the ablation resistance. At 8.88 wt% mullite, the composites exhibited relatively good ablation resistance with mass and linear ablation rates of 0.44 mg/s·cm2 and 6.39 µm/s. The addition of moderate mullite content promoted the formation of a dense Hf-Si-O multiphase oxide layer on the ablated surface without causing an excessive increase in surface temperature.

Ablation behavior of La2O3 modified C/C–ZrC composites fabricated by precursor infiltration and pyrolysis

La2O3 modified C/C–ZrC composites were produced by precursor infiltration and pyrolysis (PIP) technique, and the ablation resistance was tested in plasma flame at 1700 and 2400 °C. Results displayed that the density of the composites was ∼1.90 g/cm3, and ZrC and La2O3 were uniformly distributed in them. At 2400 °C, the linear and mass ablation rates of La2O3 modified C/C–ZrC composites were 8.89 ± 0.82 μm/s and 0.21 ± 0.01 mg/s, respectively. The positive effect of La2O3 was to promote the liquid phase sintering of ZrO2, which was helpful to promote the formation of an inlaid La–Zr–O molten layer that acted as a protective barrier. At 1700 °C, the composites exhibited minimal linear and mass ablation rates of 0.41 ± 0.14 μm/s and 0.04 ± 0.01 mg/s, respectively. At this temperature, La2O3 promoted the solid phase sintering of ZrO2 to form an intact La–Zr–O particle-stacked layer, and the intact oxide layer positively protected the composites.

Structural Electromagnetic Absorber Based on MoS2 /PyC-Al2 O3 Ceramic Metamaterials.

Limited by the types of suitable absorbents as well as the challenges in engineering the nanostructures (e.g., defects, dipoles, and hetero-interface) using state-of-the-art additive manufacturing (AM) techniques, the electromagnetic (EM) wave absorption performance of the current ceramic-based materials is still not satisfying. Moreover, because of the high residual porosity and the possible formation of cracks during sintering or pyrolysis, AM-formed ceramic components may in many cases exhibit low mechanical strength. In this work, semiconductive MoS2 and conductive PyC modified Al2 O3 (MoS2 /PyC-Al2 O3 ) ceramic-based structural EM metamaterials are developed by innovatively harnessing AM, precursor infiltration and pyrolysis (PIP), and hydrothermal methods. Three different meta-structures are successfully created, and the ceramic-based nanocomposite benefit from its optimization of EM parameters. Ultra-broad effective absorption bandwidth (EAB) of 35GHz is achieved by establishment of multi-loss mechanism via nanostructure engineering and fabrication of meta-structures via AM. Due to the strengthening by the PyC phase, the bending strength of the resulting ceramics can reach ≈327MPa, which is the highest value measured on 3D-printed ceramics of this type that has been reported so far. For the first time, the positive effect deriving from the engineering of the microscopic nano/microstructure and of the macroscopic meta-structure of the absorber on the permittivity and EM absorption performance is proposed. Integration of outstanding mechanical strength and ultra-broad EAB is innovatively realized through a multi-scale design route. This work provides new insights for the design of advanced ceramic-based metamaterials with outstanding performance under extreme environment.

Cyclic ablation behavior of mullite-modified C/C-HfC-SiC composites under an oxyacetylene flame at about 2400 °C

Mullite-modified C/C-HfC-SiC composites were prepared via precursor infiltration and pyrolysis (PIP). The phase composition, microstructure, and cyclic ablation behavior under oxyacetylene flame with a heat flux of 4.18 MW/m2 were investigated, and a comparison with the C/C-HfC-SiC composites showed that the mullite-modified composites have better ablation resistance. Results displayed a HfO2 skeleton structure wrapped by SiO2 and a dense layer of HfO2-SiO2 in the center and transition regions after the first ablation for 30 s, respectively. The structures transformed into HfSiO4-wrapped carbon fibers and "island" shape HfO2-HfSiO4-SiO2 layer after the second ablation for 30 s. Then both structures underwent severer peeling of HfSiO4 and consumption of SiO2 after the third ablation for 30 s. The modified composites exhibited better mass ablation rates after forming HfSiO4, which were 0.36 mg/s cm2 and 0.38 mg/s cm2, respectively.

Research on the thermal conductivity and ablation performance of gradient 3D woven carbon/carbon composite

This paper presents a method to manufacture gradient three-dimensional (3D) orthogonal preforms by controlling fiber tension in the flexible oriented 3D woven process (FO3DWP). The method was then adopted to fabricate three groups of gradient and uniform 3D woven preforms in order to conduct fiber volume fraction analysis. The precursors were simultaneously prepared into carbon/carbon (C/C) composites by means of the precursor infiltration and pyrolysis (PIP) process. The experimental results demonstrated that the outer interlayer distance of the gradient C/C composite was smaller than the inner interlayer distance, leading to the increase of the pore distribution diameter in gradient C/C composites. Thermal conductivity test and ablation properties test were conducted experimentally via oxyacetylene flame and transient hot-wire test, respectively. The out-of-plane thermal and ablation rate of the gradient composites were found to be lower than the ones of uniform composites. Furthermore, both the ablation resistance and the thermal conductivity increased with increasing fiber volume fraction. During the ablation test, carbon fibers in the x- and y-yarn area were shown to be able to protect the matrix and interface from further ablation, compared with the z-yarn area. Those results, successfully demonstrating the thermophysical property improvement, proved great potential of the gradient 3D woven C/C composites in aerospace applications.

YbSiOC ceramics with a multidimensional nanostructure for high-efficiency electromagnetic wave absorption

The controllable microstructure of a material plays a vital role in its electromagnetic (EM) wave absorption performance. Herein, a multidimensional nanostructure including a matchstick-like SiCnws network structure with a carbon nanocluster was grown in-situ in a porous Yb2Si2O7 ceramic by precursor infiltration and pyrolysis (PIP) to prepare YbSiOC ceramics. As the number of PIPs increased, the absorber (SiCnws and carbon) content increased to construct a multidimensional nanostructure, which also promoted conductivity loss, interfacial polarization loss and dipole polarization loss. The results showed that the YbSiOC ceramics (with an absorber content of 28.2 wt%) achieved a minimum reflection loss (RLmin) of − 50.0 dB at 9.39 GHz with 2.7 mm, and the effective absorption bandwidth (EAB) reached 4.2 GHz (in the X band) as the thickness increased from 2.1 to 3.5 mm. To conclude, the matchstick-like SiCnws and carbon nanoclusters build a multidimensional network structure that is capable of multiple reflections and scattering of EM waves in YbSiOC ceramics. This work proposes a feasible method to design rare earth silicates with EM absorbing performance, and it is expected to have durable applications in water-vapor environments.

Preparation and electromagnetic wave absorption properties of PDC–SiC/Si3N4 composites using selective laser sintering and infiltration technology

Polymer-derived silicon carbide/silicon nitride (PDC–SiC/Si3N4) composites were prepared by additive manufacturing and infiltration technology. The composite green bodies were prepared using selective laser sintering (SLS) three-dimensional (3D) printing technology. Carbon-rich PDC–SiC was generated via precursor infiltration and pyrolysis (PIP) to increase the dielectric constant and enhance the electromagnetic wave (EMW) attenuation ability of the composites. Low-dielectric materials, including Al2O3, TiO2, and AlPO4, were introduced by sol infiltration to improve the impedance-matching characteristics of the composites. The results showed that the EMW absorption ability of the PDC–SiC/Si3N4 composites enhanced after two and four PIP cycles, whereas it degraded with further increasing the PIP cycle number. Among all the samples, the PDC–SiC/Si3N4 composite after four PIP cycles displayed an excellent EMW absorption ability with the minimal reflection loss of −46.79 dB, whereas its effective absorption bandwidth was narrow. Comparing to the sample without infiltration, the effective absorption bandwidth of the samples after the infiltration treatment with TiO2 or Al(H2PO4)3 sol increased from 1.44 GHz to 4.08 GHz and 3.52 GHz, respectively. These results demonstrate that the PIP process and infiltration with TiO2 or Al(H2PO4)3 sol resulted in a 3D-printed PDC–SiC/Si3N4 ceramic that is a promising EMW absorption material suitable for high-temperature environments.

Tensile creep properties and damage mechanisms of 2D‐woven C/HfC–SiC composites in high temperature

Tensile creep properties and damage mechanisms of 2D‐woven C/HfC–SiC composites in high temperature

Effects of heating rate on mechanical and dielectric properties of the Si3N4f/BN/Si3N4 composites by PIP

The fabrication of silicon nitride (Si3N4) fiber-reinforced boron nitride (BN) and Si3N4 matrix (Si3N4f/BN/Si3N4) composites with BN interphase through precursor infiltration and pyrolysis (PIP) process is reported. The effects of heating rate during PIP process on mechanical and dielectric properties of composites are analyzed. When the heating rate is 5 °C/min, the overall performance of Si3N4f/BN/Si3N4 composites is optimal, and the flexural strength and fracture toughness attain 138 MPa and 5.7 MPa m1/2, and the dielectric constant and dielectric loss are 3.90 and 0.008, respectively. The composites achieve a synergy combining structural with functional properties. The influence mechanism of the heating rate during PIP process on the Si3N4f/BN/Si3N4 composites disclose the following. First, the heating rate makes an effect on the carbon content in the Si3N4 matrix, and consequently the dielectric properties of the composites are changed. Second, at 8 °C/min, the modulus of Si3N4 matrix is the lowest due to the existence of nanopores. At 2 °C/min, the strong axial tensile stress results in severe cracking of the Si3N4 matrix, so the matrix modulus decrease. Third, the heating rate strongly affects the radial stress state at the interphase, which affects the interfacial shear strength of the composites. The matrix modulus and interfacial shear strength can be optimized at 5 °C/min to improve the mechanical properties of the composites.