Precursor Infiltration Research Articles

High performance Csf/SiC ceramic matrix composites fabricated by material extrusion 3D printing and precursor infiltration and pyrolysis

Material extrusion (ME) 3D printing is an emerging technology to fabricate short carbon fiber reinforced SiC ceramic matrix composites (Csf/SiC CMCs) with highly oriented short carbon fibers. In this study, the Csf/SiC CMCs were fabricated by ME 3D printing combined with the following precursor infiltration and pyrolysis (PIP). The short carbon fibers could be well kept after the PIP process. The effects of solid loading and fiber content on the microstructure and mechanical properties of the Csf/SiC CMCs were also investigated. Higher solid loading was beneficial for obtaining the denser Csf/SiC CMCs with more oriented fibers. The introduction of short carbon fibers brought more pores. The bending strength and fracture toughness of Csf/SiC CMCs first increased and then decreased with the increase in fiber content. The pulling-out and breakage of short carbon fibers contributed to the improvement of mechanical properties. High performance Csf/SiC CMCs with a bending strength of 212.74 MPa and fracture toughness of 5.84 MPa m1/2 were simultaneously achieved when the solid content was 50 vol% and the fiber content was 20 vol%. It is believed that this study can provide some understanding of the 3D printing of fiber reinforced CMCs.

Using pyrolytic carbon-coated short carbon fiber to fabricate Csf/ZrB2–SiC composites by direct ink writing and precursor infiltration pyrolysis

Direct ink writing (DIW) offers significant advantages for efficient manufacturing of complex ceramic composite components. However, the mechanical properties of short carbon fiber-reinforced ceramic composites fabricated by DIW technology were not ideal, mainly be ascribed to the absence of a suitable coating on the fiber as an interface. In this work, Csf/ZrB2 green bodies were printed by an optimized extrusion process using pyrolytic carbon-coated short carbon fibers (Csf). High-performance Csf/ZrB2–SiC composites were obtained through the infiltration and pyrolysis of SiC precursor six times. With increasing Csf content, the dimensional deviations decreased and the mechanical properties increased. When the Csf content was 30 vol%, the dimensional deviation of the Csf/ZrB2–SiC composite was less than −0.5 % in the X and Y directions and about −2 % in the Z direction. A marked increase in the flexural strength and fracture toughness of the composite was also obtained, reaching 275.0 MPa and 5.26 MPa m1/2, respectively.

Flexible CNT-based composite films with amorphous SiBCN-inhibited ultrafine SiC grains for high-temperature electromagnetic shielding

Lightweight, flexible and highly conductive electromagnetic interference (EMI) shielding materials are of great importance for protecting flexible electronics and telecommunication devices under extremely high temperature conditions. A potential solution is to incorporate ceramic phases with highly conductive flexible carbon nanotube films to improve their thermal stability. However, the grain size of the ceramic phase generally increased significantly as the temperature increased which led to brittleness. In this work, a highly flexible carbon nanotube (CNT) film with controllable ceramic nanocrystals was prepared by precursor infiltration and pyrolysis. The silicon carbide (SiC) grain size in the nanocomposites was inhibited by the spatial confinement effects of CNT networks and a second amorphous SiBCN phase. The SiC grain size in the composite film decreased with the increase of the SiBCN content and the elongation at break of the nanocomposites improved significantly by 45 %. Moreover, the initial thermogravimetric temperature of the prepared films has been significantly improved to exceed 600 °C compared to the raw CNT film. Importantly, the nanocomposite film exhibited an average EMI shielding effectiveness of ∼40 dB from 8.2 to 12.4 GHz. Benefiting from the ultrafine grain size, the nanocomposite films could be folded and extended without micro-cracks over 1000 times. Combining the performance and mechanical properties of the nanocomposite film, this approach provides important guidance for designing high-performance CNT-based electromagnetic shielding materials with superior flexibility at elevated temperatures.

The antioxidative protection mechanism of the ultra-high temperature radome composite material BNf/SiBN

In the study, a BNf/SiBN composite was fabricated through precursor infiltration and pyrolysis (PIP) method. The oxidation resistance of the composite was investigated at different oxidation temperatures, focusing on the micro-structure evolution, the phase composition and oxidation kinetics of bare fibers versus fibers protected by the matrix under various oxidation states. The result indicates that the BNf/SiBN composite remains stable at 1100 °C in air atmosphere, while the fibers protected by matrix maintain their complete structure even at 1500 °C. Furthermore, we elucidated the oxidation mechanism of SiBN matrix: SiBN matrix undergoes a prior oxidation stage and transforms into amorphous SiO2 and B2O3 at high temperatures to impede the oxygen attachment to fibers while preserving the integrity of internal structure. The emergence of ultra-high temperature resistant BNf/SiBN composite and along with the exploration of oxidation behavior has opened up new approach for advancing radome material development.

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.

Interfacial modulation of SiC/TiC hybrid nanofibers for fabricating flexible ceramic electromagnetic wave absorbers

Titanium Carbide (TiC), characterized by its hardness, conductivity and thermal stability, can serve as a suitable additive phase for SiC nanofibers. TiC phase can improve the flexibility and electromagnetic wave absorption property of SiC nanofibers without sacrificing its high-temperature thermal stability. Herein, flexible SiC/TiC hybrid nanofibers with different Ti contents were fabricated by electrospinning and precursor infiltration pyrolysis. The introduction of Ti can not only generate conductive TiC phase, but also act as a catalyst to regulate the growth of SiC grains, so as to adjust the flexibility and electromagnetic properties of the hybrid nanofibers. At the optimal Ti precursor content of 4 wt%, the SiC/TiC-4 hybrid nanofibers exhibit a broad effective absorption bandwidth of 4.5 GHz with the thickness of 1.6 mm. The flexible SiC/TiC hybrid nanofibers This work can provide a reference for the design of flexible ceramic nanofiber absorbers and is expected to enable practical application in high temperature conditions.

Superior ablation resistance of C/C–HfC[sbnd]SiC composite sharp leading edges above 2500 °C prepared by precursor infiltration and pyrolysis

HfCSiC-modified carbon/carbon composite (C/C–HfCSiC) sharp leading edges (SLEs) were prepared via precursor infiltration and pyrolysis for potential hypersonic applications. The effect of SiC proportion on the ablation behavior of the SLEs under oxyacetylene flames with 2.38 MW/m2 and 4.18 MW/m2 was investigated. The preferred sample with a volume ratio of HfC to SiC of 0.74 possessed almost zero degradation (linear recession rate 0.6 μm/s) up to a temperature of 2371 °C. As the temperature increases to 2527 °C in the latter condition, the SLE with less SiC (the volume ratio of HfC to SiC is 1.10) exhibited a linear recession rate of 1.03 μm/s during cyclic ablation of 3 × 40 s. Relatively more SiC addition is favorable under lower heat flux due to the better oxygen barrier performance of the scale. However, superior ablation resistance is available under higher heat flux with less SiC addition due to the higher thermal stability of the resulting oxide scale.

Preparation and ablation behavior analysis of non-equimolar Cf/(Hf1/2Zr1/3Ti1/6)C composites under oxyacetylene flame with different heat fluxes

In this study, the synthesis of Cf/(Hf1/2Zr1/3Ti1/6)C non-equimolar middle-entropy composites was reported through precursor infiltration and pyrolysis processing for the first time. The pyrolysis process of the (Hf1/2Zr1/3Ti1/6)C precursor was examined by XRD, while the resultant ceramic was characterized by SEM, EDS, and TEM. The results showed that precursor-derived (Hf1/2Zr1/3Ti1/6)C powders were characterized by single-phase and uniformly distributed elements from microscale to nanoscale. The Cf/(Hf1/2Zr1/3Ti1/6)C composites exhibited a density of 2.741 g/cm3 and a porosity of 11.49 vol%. The various elements were uniformly distributed throughout the material. It also demonstrated outstanding mechanical properties, with a flexural strength of 219.34 MPa and a modulus of 24.82 GPa. At the heat flux of 3 MW/m2, the oxides after ablation were inadequate to fully envelop the substrate. When the heat flux increased to 4 MW/m2, a dense Hf-Zr-Ti-O multiphase oxide layer was formed on the surface of the sample, providing the internal Cf/(Hf1/2Zr1/3Ti1/6)C composites against further ablation. At the heat flux of 5 MW/m2, (Hf, Zr)TiO4 was severely consumed. Our research expands the application scope of non-equimolar middle-entropy composites in the domain of ultra-high temperature ablation resistance.

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.

Effects of in situ formed nanostructures on the structure and properties of C/SiOC composites

AbstractIn this paper, Ni was introduced into the matrix of carbon fiber reinforced SiOC (C/SiOC) composites by the precursor infiltration and pyrolysis method to catalyze the generation of in situ formed nanostructures including carbon nanotubes (CNTs), turbostratic carbon, and SiC. The effect of in situ formed nanostructures catalyzed by Ni on the properties of the C/SiOC composites was investigated. The results demonstrated that the presence of in situ formed nanostructures in the matrix improved the densification and mechanical properties of C/SiOC composites. In addition, the incorporation of in situ formed nanostructures facilitated the formation of thermal conductivity pathways within the composites, thereby enhancing the thermal conductivity of C/SiOC composites. Furthermore, in situ formed nanostructures‐containing C/SiOC composites developed a carbon friction layer comprising CNTs and turbostratic carbon, which significantly enhanced the abrasion resistance, endowing C/SiOC composites stable friction coefficients, and lower levels of wear.

Vat photopolymerization of large-aperture high performance SiC mirror through multiphase carbon infiltration modification

Vat photopolymerization technique (VPP) shows advantages in rapidly preparation of complex structure silicon carbide matrix composites (Si/SiC). However, compared with traditional preparation technology, the properties of Si/SiC prepared via VPP are insufficient due to the presence of residual Si and carbon. Herein, the reaction mechanism of Si and carbon were systematically studied. Multiphase carbon was introduced into porous SiC preform via carbon precursor infiltration pyrolysis (CPIP) and graphitization methods. The content of residual Si was significantly decreased after reactive melt infiltration (RMI), and the residual carbon was eliminated through partial graphitization of the carbon. The influence mechanism of the carbon content and crystallinity on the reaction process of Si and carbon was studied. It suggested that the diameter of capillary channel and crystallinity of carbon are the main factors affecting residual carbon content in the final body after RMI. The sample with multiphase carbon achieved the best performance after RMI. The residual Si content, bulk density, flexural strength and elastic modulus are 11.58%, 3.04 g/cm3, 280.09 MPa and 355.48 GPa. In addition, the lowest coefficient of linear expansion was 2.39×10−6 K−1. Finally, a large-aperture SiC mirror with a diameter of 500 mm was prepared. Therefore, this research lays a foundation for promoting the application of large-aperture Si/SiC prepared via 3D printing.

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.

Ni-based PCS-derived adsorbent with superior electromagnetic absorption capacity and reduced radar cross section

Low-cost and high-efficiency electromagnetic wave absorption materials had extremely broad application prospects in the realms of military and civilian domains. A series of Ni-based PCS-derived adsorbents made from precursor infiltration pyrolysis at different pyrolysis temperatures were investigated in this research. The results showed that after being pyrolyzed at 1200 °C, the Ni-based PCS-derived adsorbent possessed the lowest reflection loss value of −59.52 dB, while it reached a peak effective absorption bandwidth of 2.84 GHz with 1000 °C treatment, of which the calculated electromagnetic absorption efficiency was meanwhile the best. Besides, the simulation results showed that the adsorbent after being pyrolyzed at 1000 °C could minimize the radar cross section of the target, of which the strongest radar cross section reduction value was 21.34 dB·m2, significantly enhancing its stealth performance. Therefore, the Ni-based PCS-derived adsorbent possessed great electromagnetic wave absorption performances under conditions of high-temperature pyrolysis, which provided a reference for future electromagnetic wave absorption material design.

Additive manufacturing of broadband electromagnetic wave absorbing materials: Polymer-derived SiC/Si3N4 composites with triply periodic minimal surface meta-structure

High temperature ceramic-based electromagnetic wave (EMW) absorbing materials has been widely studied as multifunctional materials for the application in various high-speed vehicle. However, current high temperature EMW absorbing materials are limited by narrow absorption bandwidths due to their inferior impedance matching characteristics across a wide frequency range. This study proposes a novel polymer-derived SiC (PDCs-SiC)/Si3N4 triple periodic minimal surface (TPMS) meta-structure inspired by the gyroid bionic structure. The presented design strategy integrates the material and meta-structure properties, which was inspired by the interaction mechanism between these properties on the EMW absorption performance of the prepared composites. The TPMS meta-structure were fabricated through three-dimensional (3D) printing combined with precursor infiltration pyrolysis technology, followed by annealing treatment and Al(H2PO4)3 sol infiltration. The results demonstrated that the dielectric constants of the composites were reduced through annealing treatment and Al(H2PO4)3 sol infiltration process, thereby improving impedance matching and enhancing the EMW absorption performance. The effective absorption bandwidth (EAB) of the prepared PDCs-SiC/Si3N4 composites reached 3.52 GHz at a thickness of 3.3 mm. Furthermore, TPMS meta-structure with DSM unit demonstrated the excellent absorbing properties with a wide absorption bandwidth of 11.12 GHz, as evidenced by simulations and experiments. This can be attributed that the fully connected porous TPMS meta-structure further improved the impedance matching and enhanced the transmission path of electromagnetic waves, while the discontinuous unit in the top layer of DSM induced electromagnetic wave resonance and interference cancellation, thereby enhancing the EMW absorption performance of composites. This study presents an innovative development strategy for designing and preparing high-temperature electromagnetic wave absorbing materials with broad bandwidth.

Advance understanding of the synthesis process, special performance, and multidiscipline applications of SiC nanowires and the constructed composites

As research and development of nanocomposites receive more attention in today's fast-paced world. SiC nanowires (SiC NWs) and their composites exhibit numerous unique and exceptional properties. As a result, they are widely used in various fields such as the chemical industry, optoelectronic devices, electronic products, aerospace, and military applications. In this paper, we present a comprehensive summary of the synthesis technology, distinctive properties, and potential applications of SiC NWs and the composite constructed from them. The introduction begins with an overview of the basic concept and characteristics of SiC. It then provides a detailed list of common synthesis methods, including precursor infiltration pyrolysis, chemical vapor deposition, solvothermal synthesis, carbothermal reduction, template method, other methods of molten salt, controllable chemical etching, and self-assembly synthesis. The advantages and shortcomings of these methods are also discussed in the context of specific applications. Then, the special performance and multidisciplinary applications are displayed after summarizing the previous studies. Eventually, this review concludes with an outlook on future research regarding SiC NWs and their composite materials, highlighting major prospects, challenges to be addressed, and possible solutions in a wide range of areas. A systematic overview of the topic of interest actually helps to reveal patterns in research cognition, plays a potential role in fostering awareness of scientific innovation and cross-thinking, and also serves as a guide for scientific research and interest development.

Microstructure evolution and ablation mechanisms of Csf/ZrB2-SiC composites at different heat fluxes under air plasma flame

In this study, short carbon fibre (Csf) reinforced ZrB2-SiC composites were fabricated via direct ink writing followed by precursor infiltration and pyrolysis. The ablation behaviour of the composites was investigated at heat fluxes of 4–6 MW/m2 under an air plasma flame, which revealed excellent ablation resistance with negative linear ablation rates of − 0.1 to − 0.5 µm/s. The results showed that ZrO2-SiO2 oxide layer was formed on the ablation surface after ablation, which provided effective protection to the internal materials. With an increase in heat flux, ZrO2 precipitated from the SiO2 melt first in the form of nano-tetragonal ZrO2 (t-ZrO2), owing to the vaporisation of SiO2. During cooling, the nano t-ZrO2 particles were retained, and some of them reacted with SiO2 to form ZrSiO4, thus improving the thermal stability of the SiO2-ZrO2 oxide layer. In contrast, t-ZrO2 agglomerated and grew owing to capillary force and finally transformed into monoclinic ZrO2 (m-ZrO2). Moreover, a higher heat flux led to the size of precipitation ZrO2 increases, meanwhile increasing the content of t-ZrO2 and ZrSiO4 in the oxide layer.

Effect of BN interfacial layer on the mechanical behavior of SiC fiber reinforced SiC ceramic matrix composites

AbstractBoron nitride (BN) interfacial layer with controlled thickness and structure was prepared on the surface of near stoichiometric ratio SiC fiber preforms by a chemical vapor deposition process, and the SiC/SiC composites were obtained by polymer precursor infiltration and pyrolysis process. The microstructure of the BN interfacial layer and SiC/SiC composites was tested by scanning electron microscopy, and the mechanical behavior of SiC/SiC composites was characterized by a mechanical properties test. Results showed that BN interfacial layer was evenly distributed in the fiber preforms with excellent thickness consistency. As the thickness of the BN interfacial layer increased, the deflection path of the crack increased gradually, resulting in the flexural strength first increasing and then decreasing. The mechanical behavior mentioned above was mainly attributed to the dual effects of load transfer and crack propagation of the BN interfacial layer; that was, the crack propagation of ceramic matrix under external load lengthened the path of load transfer and formed a large number of fibers bridging and pulling out successively, which contributed to the energy dissipation mechanism.

Effect of chemical vapor infiltration on the flexural properties of C/C-SiC composites prepared by the precursor infiltration pyrolysis method

Effect of chemical vapor infiltration on the flexural properties of C/C-SiC composites prepared by the precursor infiltration pyrolysis method

Microstructure and Properties of C/HfC-SiC Composites Prepared by Slurry Impregnation Assisted Precursor Infiltration Pyrolysis

Microstructure and Properties of C/HfC-SiC Composites Prepared by Slurry Impregnation Assisted Precursor Infiltration Pyrolysis