Ablation Properties Research Articles

Ablation behaviour of Cf–ZrC-SiC with and without rare earth metal oxide dopants

Continuous carbon fibre/carbon composites are candidates for ultra-high temperature applications due to their ability to retain their strength at elevated temperatures, however they easily oxidize and ablate in high temperature oxygen-based environments, a fact that seriously limits their applications in the aerospace industry. The introduction of ultra-high temperature ceramics (UHTCs) as a matrix in carbon fibre preforms effectively improves their oxyablation resistance at ultra-high temperatures in air atmospheres. In the present study, zirconium carbide-based ultra-high temperature ceramic matrix composites (UHTCMCs) simultaneously doped with silicon carbide and rare earth (RE) metal oxides were prepared by a slurry impregnation and pyrolysis method using phenolic resin as the bonding agent. The combination of injection and vacuum impregnation achieved a maximum density of up to 60% of theoretical. These composites were subsequently evaluated in terms of their ablation properties using an oxyacetylene (OAT) torch at temperatures of ∼2500 °C for 60 s. No significant surface damage was observed on any of the ablated samples. When ceria was used as the RE metal oxide dopant, the evidence suggests that cerium silicate was formed by the ceria dissolving in the molten silica; though this didn't appear to offer very much additional oxyablative protection. In contrast, when yttria was used, it improved the performance via stabilization of the cubic zirconia that formed on oxidation; this provided the greatest protection of all the samples tested. The combination of both ceria and yttria yielded the combined mechanism.

Mechanical and ablative properties improvement of HfC-SiC coatings upon introduction of TiC

A novel structural Hf-Ti-Si-C multiphase solid solution coating was designed and manufactured by chemical and solid solution reactions to improve the mechanical and ablation behavior of HfC-SiC coatings. Results show that, with TiC addition, the formed HfxTi1−xC and (Ti1−xHfx)3SiC2 solid solutions can significantly enhance the micro-mechanical and ablation properties of the coating. The improved hardness and modulus, as well as the reduced ablation rates are mainly attributed to the optimized structure and solid solution reinforcing effect of coating. Moreover, the Ti-additives are conducive to restrain the active oxidation of SiC. Furthermore, HfTiO2 can reduce the oxides cracking due to the inhibited crystal transformation of HfO2 and its good self-healing ability, forming a dense and stable oxide scale with superior thermal protection.

The influence of aluminum nanoparticles on the laser ablation characteristics of hydroxylamine nitrate-based liquid propellants

Hydroxylamine nitrate is a nontoxic green energetic propellant that has a high energy density and wide application prospects in the field of aerospace propulsion. Here, the laser ablation and propulsion properties of hydroxylamine nitrate-based propellants doped with aluminum nanoparticles were studied. The results showed a significant improvement in the laser absorption properties of hydroxylamine nitrate doped with aluminum nanoparticles. The maximum absorption rate increased by more than 80%, while the absorption depth decreased considerably with a minimum of 277 μm. The sputtering behavior also weakened during laser ablation, and the impulse of hydroxylamine nitrate could be enhanced by doping aluminum nanoparticles. With the 0.7wt% mass fraction of aluminum nanoparticles, a maximum impulse bit of 57.55 μN·s at 90 mJ laser energy. This is led to a maximum energy conversion efficiency of 218.1% and an enhancement of the kinetic energy of the hydroxylamine nitrate-based propellant of 56% with laser energy of 25 mJ. Compared with ordinary liquid propellants, doped samples have better propulsion performance.

Fiber-Optic Distributed Sensing Network for Thermal Mapping of Gold Nanoparticles-Mediated Radiofrequency Ablation.

In this work, we report the design of an optical fiber distributed sensing network for the 2-dimensional (2D) in situ thermal mapping of advanced methods for radiofrequency thermal ablation. The sensing system is based on six high-scattering MgO-doped optical fibers, interleaved by a scattering-level spatial multiplexing approach that allows simultaneous detection of each fiber location, in a 40 × 20 mm grid (7.8 mm2 pixel size). Radiofrequency ablation (RFA) was performed on bovine phantom, using a pristine approach and methods mediated by agarose and gold nanoparticles in order to enhance the ablation properties. The 2D sensors allow the detection of spatiotemporal patterns, evaluating the heating properties and investigating the repeatability. We observe that agarose-based ablation yields the widest ablated area in the best-case scenario, while gold nanoparticles-mediated ablation provides the best trade-off between the ablated area (53.0–65.1 mm2, 61.5 mm2 mean value) and repeatability.

Ablation behavior of a C/C-ZrC-SiC composite based on high-solid-loading slurry impregnation under oxyacetylene torch

A C/C-ZrC-SiC composite was successfully prepared by high-solid-loading slurry impregnation combined with polymer infiltration and pyrolysis. The microstructure and ablation behavior of the C/C–ZrC–SiC composite were investigated. ZrC particles were uniformly distributed in the matrix, and the obtained C/C–ZrC–SiC composite had a high density of 2.74 g/cm3. After exposure to oxyacetylene flame with a heat flux of 3.86 MW/m2 for 120 s, the mass and linear ablation rates of the composite were 0.72 ± 0.11 mg/s and 0.52 ± 0.09 µm/s, respectively. The excellent ablation properties of the composite were attributed to the protection of the matrix by a three-layered oxide scale consisting of ZrO2/SiO2-rich/ZrO2-SiO2.

Mechanical, Thermal, and Ablative Properties of Silica, Zirconia, and Titania Modified Carbon-Phenol Ablative Composites

The effect of nanozirconia, nanotitania, and fumed silica on the mechanical, thermal, and ablation behaviour of carbon-phenolic (C-Ph) composites is investigated. The inorganic nanofillers at different loading percentage are used to prepare nano-C-Ph panels by the compression moulding technique. The dispersion of nanofillers is confirmed through SEM analysis. After manufacturing of C-Ph laminates, the mechanical properties such as tensile strength and hardness are evaluated and the effect of these fillers is investigated. Thermal conductivity, thermal erosion, and back wall temperatures were measured to understand the thermal and ablation behaviour of nano-C-Ph laminates. Additionally, the ablation mechanism is analysed by performing SEM analysis of partially and fully burnt composite laminates. The erosion resistance and burnout time of zirconia-C-Ph panels significantly improved with increase in filler loading percentage; however, the back wall temperature rises with filler loading. Titania-filled C-Ph panels show a better control over the back wall temperature but with a poor erosion control. Silica-filled composite panels have shown a balance between decreased back wall temperature with a reasonable erosion rate and burnout time.

Ablation properties and mechanism of a novel La2Hf2O7 coating

Based on excellent thermal stability and high melting point, La2Hf2O7 coating was prepared on SiC coated C/C composites by SAPS. When exposed to a heat flux of 3.2 MW/m2 for 20 s, the maximum surface temperature reaches 2240 °C, and the linear and mass ablation rates are 0.0030 mm/s and 0.0001 g/s, respectively. The chemical composition of the ablated La2Hf2O7 coating remained unchanged, and the coarsening of La2Hf2O7 grains caused a denser surface morphology with some pinholes and microcracks, which was attributed to thermal accumulation and scouring of heat flux. Owing to the low thermal conductivity, most of the heat was concentrated on the superficial region, promoting the outer La2Hf2O7 coating to evolve into a dense block structure with some defects, and the inner La2Hf2O7 coating maintained the initial structure. Because of the dense structure and low oxygen permeability of LaHf2O7 coating, the inner SiC coating was well protected without oxidation. Moreover, the nano-indentation results show that the hardness of La2Hf2O7 coating increased from 6.39 to 15.67 Gpa, which was ascribed to the intense solid-state sintering of La2Hf2O7 coating.

The influence of heat treatment on the ablation behavior of the C/Cx-SiCy composites tested by thin-blade under oxyacetylene torch

C/Cx-SiCy composites are one of the most promising counterparts of C/C composites as they maintain the mechanical strength of C/C composites while providing excellent anti-ablation properties at the same time. This paper reports that the composites could exhibit even better anti ablation properties after heat treatment. The materials were heat-treated and then tested with a thin-blade oxyacetylene torch without the protection of any coatings. The 1600 °C heat-treated thin-blade specimen could sustain the ablation of the oxyacetylene torch with a temperature of 1776 °C (80 °C higher than the original material without heat treatment) and a lower liner ablation rate (1.31 μm/s) than the original material (1.66 μm/s). An extreme ablation test was also conducted at around 2400 °C, and the 1600 °C heat-treated specimen exhibited a lower linear ablation rate (13 μm/s) than the original specimen (47 μm/s). The influence of the heat treatment on the crystallinity of the matrix is studied with the additional help of Raman spectroscopy and XPS. The ablation mechanism is discussed in detail, and the fluent condition of the thin-blade specimen is simulated. The paper also reports a different ablation behavior of the 1600 °C heat-treated specimen from the material without heat treatment to explain their excellent ablation property.

Effect of different nanostructured SiC on thermal, ablation and char layer mechanical properties of ethylene propylene diene monomer composites

AbstractSiC nanowire (SiC‐NW) and SiC nanopowder (SiC‐NP) were used to reinforce ethylene propylene diene monomer (EPDM) composites to improve their ablation and erosion resistance. The mechanical and thermal properties of the composites were investigated. The ablation resistance and thermal insulation performance of the composites were evaluated based on the oxyacetylene ablation and ablation motor experiments. In addition, the particle erosion resistance of the char layer was characterized. The test and experimental results show that, compared with the basic formulation, the ablation resistance of the formulations containing SiC‐NW and SiC‐NP increased by 85.54% and 71.08%, respectively. The particle erosion resistance of the char layer increased by 80.61% and 63.39%, respectively. Meanwhile, the SiC nanofiller reduced the thermal insulation performance of the EPDM composites. Compared with the basic formulation, the maximum back temperature of the SiC‐NW and SiC‐NP formulations increased by 39.23% and 13.08%, respectively. It inferred that during the ablation process, the SiC nanofiller can not only promote the deposition reaction of pyrolysis gas, but also react with oxidizing components and the char layer at different temperatures, thus improving the ablation resistance of the EPDM composites and the strength of the char layer. However, the high thermal conductivity of SiC nanofiller reduces the thermal insulation performance of the composites.

Silicon‐containing polyarylacetylene aerogel with heat resistance and ablative property for high‐temperature insulation

AbstractOwing to the high porosity and low thermal conductivity of organic aerogels, they have been widely used to develop lightweight heat insulation materials. However, their applications in high‐temperature environments such as in aerospace applications are usually limited by the heat resistance or ablative property of the organic matrix. In this study, we prepared a novel organic aerogel for high‐temperature insulation by the sol–gel method and freeze‐drying. The matrix is the thermosetting silicon‐containing polyarylacetylene (PSA) resin with excellent comprehensive properties, namely, high heat stability, low volatile component content, and high‐temperature ceramic performance. The obtained PSA aerogel retains the heat resistance (Td5 = 634.8°C) and ablative properties (Yr800 = 92.6%) of the PSA resin, and the internal regular macropores and high porosity (70%) result in an extremely low weight (0.1200 g cm−3), low thermal conductivity (0.039 W m−1 K−1)), and efficient heat insulation. Thus, this is an ideal material for high‐temperature insulation in the aerospace field.

Enhancing Thermal Insulation of EPDM Ablators via Constructing Alternating Planar Architectures.

Ethylene–propylene–diene monomer (EPDM) composites were usually enhanced with ablative additives to protect solid rocket motor (SRMs) casings. However, the poor thermal insulation caused by the high thermal conductive ablative fillers can lead to rocket motor failure. Herein, the novel EPDM composites containing alternating layers of ablative EPDM (AM) and heat-insulated EPDM (HM) were prepared through layer-multiplying extrusion. Compared with conventional EPDM ablative material, the multilayer composites showed enhanced thermal insulation and mechanical properties that could be further improved by tuning the number of layers. The ablation and thermal insulation properties possessing in AM and HM layers could be combined by forced assembly during co-extrusion, and the alternating multilayer composite was capable of showing the effect of each component. In particular, compared with AM, the maximum back-face temperature with 40 alternating layers of AM/HM decreased from 96.2 °C to 75.6 °C during oxyacetylene test, while the good ablation properties were preserved in the AM component. This significant improvement was attributed to the planar orientation and densification of ablative additives, and the interruption of conductive pathways in the through-plane direction of AM/HM alternating laminate. The anisotropic EPDM composites featuring mechanical robustness, good ablative resistance and thermal insulation suggest considerable potential application in the aerospace industry.

Synergetic effects of Kevlar fibers and polyimide powder fillers on performances of Poly(diaryloxyphosphazene) based elastomeric heat shielding materials

Poly(diaryloxyphosphazene) (PDPP) represent the state-of-the-art alternative and promising elastomeric heat shielding materials (EHSMs) for solid rocket motors due to its better ablative performance and unique charred layers. Kevlar fibers (KF) usually constitutes the common fibrous reinforcement for PDPP based formulations of EHSMs because KF is a kind of organic fiber with heat resisting available at a lower price, and there is strong interfacial bonding between fibers and PDPP matrix. To increase the mechanical and ablation properties of PDPP based KF composites, polyimide powders (PIP) is considered here in the material formulation because of good dispersion effects of PIP into matrix and its excellent thermal stability. In this work, dense and intact charred layers were constructed via the combination of KF and PIP into the PDPP based formulations of EHSMs. The results have showed that the tensile strength and ablation properties exhibited a significant increase with addition of PIP. At combination of 9 phr KF and 10 phr PIP in formulations, the mass ablation rate reduced to 0.044 g/s, which was 40.5% lower than that of insulation filled with only KF fillers. Furthermore, micro-computed tomography (micro-CT) was used for the first time to characterize morphology of charred layers of the ablative composites. It was indicated that no ply delamination and interfacial debonding were found between charred layers and beneath virgin materials. This study provides an effective approach to prepare a new EHSMs system, which can be applied in new potential aerospace vehicles.

Enhanced ablation resistance of Divinyl‐POSS modified additional liquid silicone rubber and its fiber reinforced composite

AbstractTo further improve the ablation and thermal properties of silicon rubber composite materials, the 3, 13‐divinyloctaphenyl double‐decker polyhedral oligomeric silsesquioxane (DV‐DDSQ) modified additional vinyl‐terminated polydimethylsiloxane (VPDMS) was prepared, and the effect of high silica fiber reinforcement on the ablation properties of VPDMS was investigated. The results show that when 0.8phr DV‐DDSQ was added, the mass residual rate at 800°C of the composites increased from 40.6% to 51.0%. The linear ablation rate (LAR) as well as mass ablation rate (MAR) of the composites of the DV‐DDSQ modified VPDMS, the high silica fiber reinforced VPDMS composite (HSF/VPDMS composite) and the high silica fiber reinforced DV‐DDSQ modified VPDMS composite (HSF/DV‐DDSQ‐VPDMS composite) decreased dramatically compared with raw VPDMS, and it was 16.36%, 35.69%, and 37.17% bring down for LAR and 5.34%, 14.60% and 25.59% for MAR, respectively. The tensile strength and hardness of the DV‐DDSQ modified composites increased by 9.52% and 14.13%, respectively, while the elongation at break decreased by 5.99%, compared with the raw VPDMS.

Facile fabrication of lightweight carbon fiber/phenolic ablator with improved flexibility via natural rubber modification

The rigidity and low strain-to-failure of the phenolic impregnated carbon ablator seriously restrict the application of this state-of-the-art thermal protection material. In this study, to improve the flexibility of carbon fiber/phenolic ablator (CFPA), natural rubber (NR) was deposited homogeneously onto the surface of the carbon fibers through impregnation. Thus, a “bridge” was built between the carbon fiber reinforcement and the phenolic resin aerogel matrix, allowing the interface better connection and better deformation ability. Experimental results indicate that, compared with the unmodified, modified CFPA has lower flexural modulus and higher fracture strain, 6.3 MPa and 39.6% at the optimal NR latex mass fraction respectively, while maintains low density, good thermal insulation properties, and excellent ablation properties. The facile fabrication via natural rubber modification of CFPA improved its flexibility and could broaden the application scenarios of lightweight carbon/phenolic composite.

Ablation behavior of thin-blade co-deposited C/Cx-SiCy composites under the influence of the complex fluid conditions of the oxyacetylene torch

This paper offers a new way of testing the ablation property of material under an oxyacetylene torch using a thin-blade specimen, which costs much less time to reach the maximum temperature and provides a harsh turbulence fluid field that's closer to reality. The thin-blade specimen experiences a higher turbulent intensity than the traditional disk-like specimen, leading to more efficient heat exchange. The fluid field simulation agrees with the testing results. In addition, we manage to synthesize the C/Cx-SiCy composites with the co-deposition chemical vapor infiltration (CVI) method. The C/Cx-SiCy composites exhibit a similar anti-ablation property as C/C composites and consist of enough SiC phase simultaneously, combining the advantages of both C/C composites and C/SiC composites. The thin-blade C/Cx-SiCy composites show a lower linear ablation rate (1.6 μm/s) than C/C composites (4.1 μm/s) and C/SiC composites (19.6 μm/s) during the oxyacetylene test. The glass layer formed on the surface of C/Cx-SiCy could cling to the bulk material instead of peeling off due to the high PyC content in the matrix could protect the SiO2 from blowing away.

Investigations on the Morphological, Mechanical, Ablative, Physical, Thermal, and Electrical Properties of EPDM-Based Composites for the Exploration of Enhanced Thermal Insulation Potential.

The most widely used filler in EPDM-based thermal insulation materials is asbestos which is hazardous to health and environment. The main motivation of this study was to develop improved EPDM-based materials by partially or completely replacing asbestos with other fillers. EPDM-Esprene501A and EPDM-Keltan®4869DE were used and the effect of three fillers (vulkasil-C, asbestos, carbon fiber fabric) on mechanical, ablative, physical, thermal, and electrical performances have been investigated. Samples were divided into phase -1, -2, and -3 by compounding EPDM with various percentages of fillers and other necessary ingredients. It was observed that asbestos and carbon fiber in the absence of vulkasil-C did not import enough reinforcement to EPDM-matrix. Experimental evidence showed that presence of vulkasil-C has not only enhanced mechanical properties but also improved thermal and ablation performance of EPDM-based composites. The swelling index was found comparatively lower with vulkasil-C than that with other fillers. Among two EPDMs, EPDM-Esprene based composites have shown comparatively better performance. Among all (phase-1–3) samples, E100K0VA (phase-2) has shown greater mechanical (stress 3.89 MPa; strain 774%), ablative (linear 0.1 mm/s; mass 0.05 g/s), and thermal (material left 91.0%) properties. Overall findings indicated improved properties of EPDM in the presence of vulkasil-C and may help to develop better heat resistant materials.

Synergetic effect of O-POSS and T-POSS to enhance ablative resistant of phenolic-based silica fiber composites via strong interphase strength and ceramic formation

As a typical ablative material, silica fiber reinforced phenolic resin composites are widely used in thermal protection system. However, its ablative properties and interfacial strength need to be further improved to meet the growing requirements of aerospace. In this work, reactive octaepoxycyclohexylethyl POSS (O-POSS) and tetrasilanoloctaphenyl POSS (T-POSS) were synthesized to modified high silica fiber cloth (HSC) and phenolic resin (PR) respectively. The flexural strength and interlaminar shear strength of modified HSC reinforced modified PR (PK-HSC/T-PR) composites are 213.1 and 22.4 MPa, 63.6% and 59.5%, higher than those of pristine HSC/PR composites, respectively. Meantime, the obtained PK-HSC/T-PR composites also exhibit lower thermal conductivity (0.2461 W⋅(m K)−1) and ablative rate (liner ablative rate: 0.128 mm/s, decreased by 22.4%). Furthermore, the mechanism of the two POSS synergetic effect for ablative performance enhancement was explored from both the aspects of matrix ceramization and interface structure evolution during ablation process.

Understanding the Role of Carbon Fiber Skeletons in Silicone Rubber-Based Ablative Composites.

At present, silicone rubber-based ablative composites are usually enhanced by carbon fibers (CFs) to protect the case of solid rocket motors (SRMs). However, the effect of the CFs’ length on the microstructure and ablation properties of the silicone rubber-based ablative composites has been ignored. In this work, different lengths of CFs were introduced into silicone rubber-based ablative composites to explore the effect of fiber length, and ceramic layers of various morphologies were constructed after ablation. It was found that a complete and continuous skeleton in ceramic layers was formed by CFs over 3 mm in length. In addition, the oxyacetylene ablation results showed that the linear ablation rate declined from 0.233 to 0.089 mm/s, and the maximum back-face temperature decreased from 117.7 to 107.9 °C as the length of the CFs increased from 0.5 to 3 mm. This can be attributed to the fact that successive skeletons concatenated and consolidated the ceramic fillers as well as residues to form an integrated, robust, and dense ceramic layer.

Improved ablation resistance and thermal insulation performances of polyimide composites by introducing albite/glass powder composition

Polyimide is a class of resins with high heat resistance, and their composites have a wide range of applications in military and civilian. However, the application of polyimides as an ablation and thermal insulation material has always been a challenge due to their low char yield during ablation in the air. Herein, we described the first application of polyimide composites—albite/glass powder doped polyimide hybrid materials - as an ablation and thermal insulation material. The key to the success of this case is that the process of the ceramization of albite/glass powder can greatly reduce the carbon loss of polyimide during the ablation process in the air. Moreover, the mechanical properties, thermal stability, ablation and thermal insulation properties of these polyimide hybrid materials have been studied systematically. This work not only opens up a new application for polyimide, but also provides a new idea for the design of novel ablation and thermal insulation material.

Mechanical and ablation properties of laminated ZrB2-SiC ceramics with Si3N4 whisker interface

Laminated ZrB2-SiC/Si3N4w ceramics were prepared by using Si3N4 whiskers as interface layer. Toughness of the laminated ceramics was remarkable improved, because of the deflection and bifurcation of crack. Moreover, the laminated ZrB2-SiC/Si3N4w ceramics showed better ablation resistance than monolithic ZrB2-SiC ceramics, which was tested at 3000 °C for 100 s. Higher thermal conductivity of laminated ceramics than that of monolithic ceramics in both the in-plane direction and through-plane direction, leads to faster heat transfer in laminated ceramics during the ablation process.