Precursor Infiltration Pyrolysis Research Articles

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.

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.

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.

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

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

Carbon/carbon-silicon carbide (C/C-SiC) composites were prepared by impregnation, hot-pressing with curing, carbonization at 800 oC and high-temperature heat treatment (800-1600 oC) using a 2D laminated carbon cloth as the reinforcing filler, and furfurone resin mixed with silicon, carbon from furfurone resin and SiC powders as the matrix. The effects of the addition of the three powders as well as subsequent chemical vapor infiltration (CVI) by methane on the density, microstructure and bend strength of the composites were investigated by scanning electron microscopy, density measurements, X-ray diffraction and mechanical testing. Both the SiC powders formed by the reaction at 1 600 oC between the added Si and C particles and the added SiC powder, play a role in the reinforcement of the materials. In three-point bending, the composites had a pseudoplastic fracture mode and showed interlaminar cracking. After 10 h CVI with methane, pyrolytic carbon was formed at the interface between some of the carbon fibers and the resin carbon matrix, which produced maximum increases in the density and flexural strength of the composites of 4.98% and 38.86%, respectively.

Additive manufacturing of continuous carbon fiber-reinforced silicon carbide composite by fused filament fabrication and precursor infiltration pyrolysis

Continuous fiber reinforced silicon carbide composites (Cf/SiC) are known for their advantages such as high strength, high modulus, high thermal conductivity, and low density. In this paper, we propose an integrated Cf/SiC preparation and processing process. The continuous carbon fiber-reinforced resin matrix composite green parts were processed by fused filament fabrication, and then ceramicized by precursor infiltration pyrolysis process. The processing parameters of the green parts, the performance of the green-part specimens, the phase evolution in the post treatment, and the performance of Cf/SiC samples were investigated. The infill line distance (ILD) had a huge influence on the mechanical properties of green parts and Cf/SiC. The bending strength of the green parts and the Cf/SiC specimens increased with the decrease in ILD. The maximum bending strength of 169.48 MPa and 155.83 MPa was achieved for the carbon fiber/polyethylene terephthalate glycol (Cf/PETG) and polylactic acid (Cf/PLA) green parts, respectively. The highest bending strength of 47.73 MPa of the Cf/SiC material was obtained with the Cf/PLA green parts, while the bending strength of 93.79 MPa was obtained for the Cf/SiC with Cf/PETG green parts. The increase in mechanical properties was believed to result from the pyrolyzed carbon brought by PETG and the increase of the equivalent fiber density within the single layer after a larger nozzle size was used.

Using flexible hydrothermal carbon-coated continuous carbon fiber to fabricate Cf/ZrB2-SiC composites by fused deposition modeling and precursor infiltration pyrolysis

In additive manufacturing of continuous fiber reinforced ceramic composites, the carbon fiber is difficult to give full play to its toughening effect without interface, and the high-viscosity resin, ceramic precursors or slurry is hardly to fully infiltrate into fiber bundles, which are not conducive to obtain high-performance ceramic composites. In this work, sugar-derived carbon acts as interface was deposited on continuous carbon fiber by hydrothermal reaction. Flexible hydrothermal carbon-coated continuous carbon fiber is appropriate for 3D printing. Continuous carbon fiber/ZrB2-polycaprolactone(PCL) filaments used for fused deposition modeling (FDM) was prepared by pre-impregnation-coating process. Ultrasound significantly improves the impregnation effect of ceramic slurry into fiber bundles. Cf/ZrB2-PCL billets with different fiber orientations were fabricated by FDM of continuous Cf/ZrB2-PCL filaments. The Cf/ZrB2-PCL billets were further densified by infiltration and pyrolysis of SiC precursor. The flexural strength and fracture toughness of Cf/ZrB2-SiC composites could reach 218.1 ± 21.3 MPa and 9.40 ± 1.45 MPa m1/2, respectively.

Low‐temperature synthesis of HfC/HfO2 nanocomposites from a commercial single‐source precursor

AbstractA liquid‐phase polymer‐to‐ceramic approach is reported for the synthesis of hafnium carbide (HfC)/hafnium oxide (HfO2) composite particles from a commercial precursor. Typically, HfC ceramics have been obtained by sintering of fine powders, which usually results in large particle size and high porosity during densification. In this study a single‐source liquid precursor was first cured at low temperature and then pyrolyzed at varying conditions to achieve HfC ceramics. The chemical structure of the liquid and cured precursors, and the resulting HfC ceramics was studied using various analytical techniques. The nuclear magnetic resonance and Fourier transform infrared spectroscopy indicated the presence of partially hydrated hafnium oxychloride (Hf–O–Cl·nH2O) in the precursor. Scanning electron microscopy of the resulting HfC crystals showed a size distribution in the range of approx. 600–700 nm. The X‐ray diffraction of the pyrolyzed samples confirmed the formation of crystalline HfC along with monoclinic‐HfO2 and free carbon phase. The formation of HfO2 in the ceramics was significantly reduced by controlling the low‐temperature curing temperature. Pyrolysis at various temperatures showed that HfC formation occurred even at 1000°C. These results show that the reported precursor could be promising for the direct synthesis of ultrahigh temperature HfC ceramics and for precursor infiltration pyrolysis of reinforced ceramic matrix composites.

Local anti-ablation modification of uneven-density C/C composites with the ZrC-SiC composite ceramics

To lower the cost and preparation period of C/C-ZrC-SiC composites, the uneven-density C/C composites (with a high density in the inner region and low density in the surface region) are designed and prepared by thermal gradient CVI process, followed by local modification of ZrC-SiC composite ceramics by precursor infiltration-pyrolysis (PIP) mothed to improve the anti-ablation performance. The ablation tests show that the SiC contents have a great influence on the microstructure of ZrO2 grains at the ablation center by adjusting the ablation temperature and the melting point of ZrO2 grains. Results prove that about 20 wt% SiC is optimum for the ZrC-SiC composite ceramics to perform best during the ablation and modify the uneven C/C composites prepared in this work. Besides, the dense C/C matrix would stop the liquid ZrO2-SiO2 phase from running off, and in return, the dense ZrO2-SiO2 phase would sink into the surface within the ablated region protecting the material beneath, which could protect the carbon fibers of the surface region and the dense C/C matrix beneath.

Fracture toughness and progressive damage mechanisms of 2.5D woven SiCf/SiC composites

This paper presents the effects of matrix and interface on the fracture toughness and progressive damage mechanisms of 2.5D woven SiCf/SiC composites. Third-generation SiC fibers were selected. 2.5D woven SiCf/SiC composites with four interfacial layers PyC, PyC/SiC, BN, BN/SiC and two matrix polycarbosilane (PCS) and liquid hyperbranched polycarbosilane with vinyl groups (VHPCS) were prepared by a combination of chemical vapour deposition (CVD), chemical vapor infiltration (CVI), and precursor infiltration pyrolysis (PIP) processes, respectively. Single edge notch bending (SENB) tests were carried out to investigate the fracture toughness. Moreover, acoustic emission (AE) and X-ray micro-computed tomography (Micro-CT) techniques were employed to analyze the progressive mechanical properties and failure mechanism. Results showed that the matrix and interface have significant effects on the fracture toughness. Moreover, 2.5D woven composites with PyC/SiC interfacial layers and VHPCS matrix have the highest fracture toughness (16.93 ± 1.20 Mpa • m1/2). Furthermore, during progressive damage, the pores can influence the crack expansion path, and effectively regulate the stress concentration and increase the toughness of the composites.

Effect of an annealing treatment on the microstructure and EMW-absorbing properties of SiCw/Si3N4 ceramics fabricated by 3D printing

SiC whisker (SiCw)/Si3N4 ceramics were prepared via selective laser sintering (SLS) and precursor infiltration pyrolysis (PIP) to achieve good electromagnetic wave (EMW) absorption performance. The as-pyrolyzed composite ceramics were annealed at 1200–1600 °C in a N2 atmosphere. The microstructural variation, phase evolution, and EMW-absorbing properties of the SiCw/Si3N4 ceramics were subsequently studied. SiC whiskers were generated in the composite ceramics during pyrolysis, and their content increased as a function of the annealing temperature. An increase in the SiCw content of the annealed samples improved the reflection loss of the composite ceramics. The absorption properties of the SiCw/Si3N4 ceramics first degraded and then improved with increasing annealing temperature. Among all the samples tested, the composite ceramics annealed at 1600 °C showed the optimal EMW absorption performance in the range of 2–18 GHz due to the lower content of free carbon and higher content of SiCw. The ceramics annealed at 1600 °C exhibited a superior absorption loss of −14.1 dB and an effective absorption bandwidth of 2.16 GHz. These results demonstrate that the EMW-absorbing performance of the SiCw/Si3N4 ceramics was significantly improved after annealing at 1600 °C. Thus, SiCw/Si3N4 composite parts with complex shapes were successfully manufactured by combining the SLS and PIP processes.

Oxidation behavior and damage mechanism of SiCf/SiC minicomposites with multilayered (BN/SiC)n interfacial coatings at 1200 ℃

ABSTRACT SiCf/SiC minicomposites with multilayered (BN/SiC)n interfacial coatings were fabricated via chemical vapor infiltration and precursor infiltration pyrolysis methods. Oxidation behavior, mechanical properties, and interfacial self-healing mechanism of minicomposites at 1200°C were comparatively studied. In dry air, SiC matrix at edges of composites was oxidized to glassy SiO2, thereby sealing the pores between fibers and matrix, healing microcracks, and preventing the diffusion of oxygen into the material. Results of thermogravimetric–differential thermal analysis proved that glassy borosilicate formed at 910°C and 1050°C in minicomposites with BN/SiC and multilayered (BN/SiC)2 coatings. In water/oxygen atmosphere at 1200°C, there existed an equilibrium between the generation of SiO2 and gaseous Si(OH)4. Uncoated sample and minicomposite with single BN coatings were simultaneously eroded by oxidizing atmosphere in directions perpendicular and parallel to fiber axis. Microholes formed due to BN volatilization were gradually healed by glassy borosilicate in minicomposites containing SiC layers, improving interface self-healing capability of composites. After oxidation in water/oxygen atmosphere for 100 min, minicomposites with multilayered (BN/SiC)2 coatings retained relatively high fracture strength and strain, which were 499.0 MPa and 1.05%, respectively.

Effect of holding time on SiC whiskers growth of SiCw/SiC composites based on SLS technology and their mechanical properties

The in-situ SiC whisker and SiC particle composites were prepared by selective laser sintering (SLS) technology, and the longitudinal and transverse growth rates of crystal nuclei at the liquid-solid interface were calculated and analyzed under the traditional vapor-liquid-solid mechanism. A mathematical model of holding time on the number of in-Situ SiC whisker growth was established, and the prediction rate was 95%. The mechanical properties of in-situ SiC whisker and pure SiC samples with similar volume densities were calculated. The results showed that: The longitudinal growth rate of crystal nuclei at the liquid-solid interface was higher than the transverse growth rate. After precursor infiltration pyrolysis (PIP) four-cycle treatment, the fracture toughness per unit volume density of B-1, B-2, and B-3 specimens increased by 198.66%, 225.00%, and 221.05%, respectively, compared with pure SiC specimens, indicating that this method has a vital role in increasing the toughness of SiC ceramics.

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.

Effect of impregnated phenolic resin on the properties of Si–SiC ceramic matrix composites fabricated by SLS-RMI

Selective laser sintering (SLS) combined with reaction melt infiltration was used to fabricate Si–SiC ceramic matrix composites, and the effects of different concentrations of phenolic resin (PF) on the properties of the SLS green body and carbonized and final Si–SiC samples were investigated. The results showed that the impregnation with PF can increase the bulk density, reduce the porosity of the samples at all stages, and improve the mechanical properties of the reactive bonded samples. The degree of densification and mechanical properties of the sample gradually enhanced with an increase in PF concentration. The main phases of the Si–SiC composites were free Si, α-SiC, β-SiC, plus an extremely small amount of Al–Si alloy, and the SiC and the Si phase contents increased and decreased, respectively, as the concentration of PF increased when measured using Rietveld refinement and image analysis software. The macroscopic properties of the samples improved greatly after precursor infiltration pyrolysis (PIP) treatment with 66.7%vol PF-ethanol solution twice. According to the crystal nucleation-growth theory, it was inferred that the infiltrated PF could provide a certain amount of pyrolytic carbon in the carbonized specimen. During the reaction bonded process, the carbon formed by carbonization pyrolysis first dissolves into the molten Si and reaches saturation. With the further dissolution of carbon, [C] and [Si] in the liquid phase contact each other to form β-SiC nuclei, the nuclei that precipitate at the pore wall position and gradually form a continuous interfacial layer of β-SiC. The β-SiC layer prevents the liquid Si from direct contact with C inside the prefabricated body, therefore, further reactants diffuse through the layer. Finally, the fine crystalline β-SiC grains were fabricated inside the specimen.

Effects of multilayer hydrothermal carbon interphases on mechanical properties and thermal shock resistance of CF/ZrB2-SiCBN

Multilayer hydrothermal carbon coatings (HTCCs) with various thicknesses were constructed on CFs using alternating hydrothermal carbonization and heat treatment approach. Well-established CF/ZrB2-SiCBN composites with distinct multilayer interphases were processed via slurry injection and precursor infiltration pyrolysis method. The multilayer HTCCs with suitable thickness would be pulled-out stepwise from the matrix, which could absorb the impact energy and toughen the composites effectively. Although the outer HTCC would still react with the matrix to form a strong interface, the moderate interfacial binding force between CF and inner HTCC could effectively transfer the load and assure the fiber debonding when the composites deformed drastically. Moreover, the increasing of coating thickness could alleviate the damage of fibers in oxidation environment and improve the critical thermal shock temperature difference of composites, while the excessive thick coating would weaken the fiber strength and limit toughening abilities of the CFs.

“Finger coral-like” ceramic fiber aerogels with enhanced high-temperature thermal insulation, anti-oxidation, and mechanical performance

Ceramic fiber aerogels are widely used in high temperature insulation. Thermal insulation under extreme conditions requires materials that can withstand sharp thermal shocks and extended high-temperature exposure. However, the oxidation resistance of traditional ceramic aerogels under a high temperature environment(above 1000 °C) is significantly reduced. Moreover, the strength degradation and structural collapse easily occurred, restricting their application. In this study, “Finger Coral” ceramic fibers aerogels were obtained using precursor infiltration pyrolysis (PIP) and electrospinning technology. The chemical composition, morphology, thermal insulation, mechanical properties and isothermal oxidation properties of SiCBN/SiC/disilicates nanoparticles (IP) ceramic aerogels were tested. The experimental results showed that the aerogel exhibited excellent mechanical and antioxidant properties over a wide range of temperatures. SiCBN/SiC/IP aerogel with a thickness of 2cm can achieve the heat insulation effect of the hot surface temperature from 1600 to 75 °C, and the thermal conductivity at 1600 °C was only 0.036 W·m−1·K−1. After 12 h of cyclic isothermal oxidation, the weight gain was only 5.17%. The material is expected to be used as a thermal insulation material in the hypersonic vehicles.