Mass Ablation Rate Research Articles

Novel low temperature derived Wf/W–ZrC–Cu composites by reactive infiltration with enhanced mechanical and thermal physical properties

Wf/W–ZrC–Cu composites with densities over 95% have been prepared by infiltrating Zr–Cu binary molten alloys into porous Wf/W + WC preforms at 1200−1400 °C. The hybrid strengthening of in-situ formed ZrC particles, and the addition of continuous Wf have made the composites improved flexure strength and fracture toughness of 612 MPa and 10.41 MPa m1/2, respectively. The residual Cu provided a moderate interface between Wf and W–ZrC matrix, which was beneficial to improved fracture energy of 2–3·103 J m−2 and thermal conductivity of over 80 W (m K)−1. The Wf impeded cracks and new surfaces to the ultra-high temperature air plasma torch. The composites thus possess superior thermal shock resistance, and the linear and mass ablation rates reduced to 0.40 mm s−1 and 0.0112 g s−1, respectively. This study provides a novel approach for the fabrication of refractory fiber reinforced refractory metal/carbide based composites with excellent comprehensive properties at relatively low temperatures.

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.

Oxidative Ablation Behavior of W‐Coated C/C Composites Prepared by Chemical Vapor Deposition with Heat Treatment

To improve the ablation resistance of C/C composites, tungsten (W) coating is applied by chemical vapor deposition (CVD) technology on C/C composites. Results show that the coatings are dense, with a thickness of about 400 μm. After heat treatment at a temperature of 1500 °C for 1 h, the main component of coating is W2C. Additionally, a dense WC layer forms on the surface of pyrolytic carbon (PyC). The sample subjected to heat treatment remains relatively intact after ablation at 3000 °C for 60 s, with a mass and linear ablation rate of 1.83 × 10−5 g s−1 and 3.03 × 10−5 cm s−1, respectively. The high‐temperature stability of WC formed on PyC and the filling of fiber gaps to prevent oxygen penetration are the main reasons for the improved ablation resistance of W‐coated C/C composites.

Synchronously constructing networked Si3N4 nanowires and interconnected graphene inside carbon fiber composites for enhancing mechanical, friction and anti-ablation properties

1 Binary reinforcements of networked Si 3 N 4 nws and interconnected GE in carbon fiber composites were constructed. 2 Networked Si 3 N 4 nws are uniformly distributed among the carbon fibers, while interconnected GE is firmly rooted on the surface of both networked Si 3 N 4 nws and carbon fiber. 3 Robust mechanical strength, excellent friction performances and outstanding anti-ablation properties of composites are realized. Carbon fiber (C f ) reinforced pyrolytic carbon (PyC) composites simultaneously possessing robust mechanical strength, excellent friction performances and outstanding anti-ablation properties are demanded for advanced aerospace applications. Efficient architecture design and optimization of composites are prominent yet remain high challenging for realizing the above requirements. Herein, binary reinforcements of networked silicon nitride nanowires (Si 3 N 4 nws) and interconnected graphene (GE) have been successfully constructed into C f /PyC by precursor impregnation-pyrolysis and chemical vapor deposition. Notably, networked Si 3 N 4 nws are uniformly distributed among the carbon fibers, while interconnected GE is firmly rooted on the surface of both networked Si 3 N 4 nws and carbon fibers. In the networked Si 3 N 4 nws and interconnected GE reinforced C f /PyC, networked Si 3 N 4 nws significantly boost the cohesion strength of PyC, while GE markedly improves the interface bonding of both Si 3 N 4 nws/PyC and fiber/PyC. Benefiting from the synergistic reinforcement effect of networked Si 3 N 4 nws and interconnected GE, the C f /PyC have a prominent enhancement in mechanical (shear and compressive strengths increased by 119.9% and 52.84%, respectively) and friction (friction coefficient and wear rate reduced by 25.40% and 60.10%, respectively) as well as anti-ablation (mass ablation rate and linear ablation rate decreased by 71.25% and 63.01%, respectively). This present strategy for networked Si 3 N 4 nws and interconnected GE reinforced C f /PyC provides a dominant route to produce mechanically robust, frictionally resisting and ablatively resistant materials for use in advanced aerospace applications.

Two birds with one stone: Construction of bifunctional-POSS hybridized boron-silicon ceramicized phenolic composites and its ablation behavior

To further enhance the ablation resistance properties of thermosetting phenolic resin matrix composites, in this work, bifunctional alkalic heptaphenyltrisilanol sodium salt polyhedral oligomeric silsesquioxane was utilized to catalyze the synthesis of boron phenolic resin and provide silicon source to obtain boron-silicon hybrid phenolic resin (BPOSSPR) with excellent ablative resistance. BPOSSPR possesses a low curing activation energy (101.4 kJ/mol) and excellent thermal properties (initial decomposition temperature was 453.0°C and char yield at 1000°C was 72.7%). The mechanical and thermal insulation properties of carbon fiber reinforced BPOSSPR composites (CF/BPOSSPR) and high silica fiber reinforced BPOSSPR composites (HSF/BPOSSPR) are significantly enhanced. The linear ablation rate and mass ablation rate of CF/BPOSSPR are as low as 0.003 mm/s and 0.0354 g/s; those of HSF/BPOSSPR are 0.119 mm/s and 0.0264 g/s. The ablation-resistance mechanism of BPOSSPR composites is mainly due to the formation of ceramic thermal barrier layers under high temperature conditions, such as B2O3, SiO2, borosilicate glass, SiC, which might play an effective role in protecting against heat flow erosion. As a result of these excellent properties, the innovative heat shielding BPOSSPR composites could offer the ability to tolerate harsher environment in future aerospace applications.

Rapid and low-cost carbon/carbon composites by using graphite slurry impregnated prepregs

A rapid and low-cost carbon/carbon (C/C) composites preparation method is proposed: graphite prepreg-coated carbon fiber fabric (CFF) is formed by hot pressing, followed by hot isostatic pressing and high temperature graphitization, to prepare C/C composite with low porosity and high crystallinity. In this method, the carbon fiber (CF) mass fraction can be precisely regulated in the range of 40–95% by the impregnation process conditions of CFF in graphite prepreg. The graphite particles in the preform were graphitized and bonded with CFF by high temperature graphitization. Finally, a ZrO2 anti-ablative layer was applied using sol-gel method. The results show that when the CF mass fraction is 50%, the C/C composite with a crystallinity of 92.21 and a porosity of 3.47% can be obtained, with mass ablation rate of 0.23 mg/s and density of 1.62 g/m3. The method can prepare C/C composites with uniform density and high ablation resistance.

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.

Enhanced ablation resistance of phenolic composites through the construction of a sea-island nanostructured char layer via in-situ catalytic graphitization of incorporated Salen-Ni complex

Phenolic resin (PR) are widely used as ablative thermal protection systems for aerospace applications. However, it remains a challenge to improve the ablation resistance of phenolic composites by designing the structures of char layer via a facile approach. In this paper, a Salen-Ni complex (CL) modified boron phenolic composite (CLBPR) was designed with low concentrations of Ni (0.05–0.45 wt%). The chemically incorporated Salen-Ni structures enabled the uniform distribution of Ni element, and the enhancement of graphitization degree of char layer through the significant catalytic effect. XPS, XRD, RAMAN and TEM analyses showed that the metallic Ni nanoparticles arising from Salen-Ni structures could effectively catalyze the ablated char layer to generate various type of graphitic nanostructures, and construct a sea-island nanostructured char layer during ablation. Furthermore, we found that the inlaid graphitic phases formed through Solid-Liquid-Solid mechanism in amorphous carbon (AC) can hinder the growth of defects, while improve the graphitization degree of char layer. The results demonstrated that the linear and mass ablation rates of CLBPR were reduced by 128.9% and 32.6% compared to the counterpart at 4 MW/m2. This research will provide some inspirations more or less for the development of more advanced polymer-matrix ablative composites in the future.

Microstructure and High-Temperature Ablation Behaviour of Hafnium-Doped Tungsten-Yttrium Alloys

W is a widely used refractory metal with ultra-high melting point up to 3410 °C. However, its applications are limited by poor ablation resistance under high-temperature flame and air flow, which is crucial for aerospace vehicles. To improve the ablation resistance of W under extreme conditions, W-Y alloys doped with different Hf mass fractions (0, 10, 20, and 30) were prepared using the fast hot pressing sintering method. Microstructure and ablation behaviours at 2000 °C were investigated. Results showed that adding an appropriate amount of Hf improved the properties of the W-Y alloy evidently. In particular, the hardness of the alloy increased with the increased content of Hf. The formation of the HfO2 layer on the surface during ablation decreased the mass and linear ablation rates, indicating enhanced ablation resistance. However, excessive Hf addition will result in crack behaviour during ablation. With a Hf content of 20 wt.%, the alloy exhibited high stability and an excellent ablation resistance.

Pre-oxidized mesophase pitch modified phenolic composites with mosaic-structured char layers and excellent ablation resistance

Currently, phenolic resin (PR) is widely used as a matrix for the polymer-based ablative materials in aerospace industry. In this paper, pre-oxidized mesophase pitch (OMP) modified boron phenolic composites (OMPBPR) and their fiber-reinforced composites were prepared. PLM and SEM analyses showed that the OMP can co-carbonize with resin matrix to construct a mosaic-structured char layer incorporated pitch-based graphitic carbon during ablation. Furthermore, mercury intrusion porosimeter, XRD, Raman and TEM analyses showed that the inlaid graphitic carbon can effectively hinder the growth of defects in amorphous carbon (AC) framework, while improve the graphitization degree of char layer. The results demonstrated that the linear and mass ablation rates of OMPBPR were optimally reduced by 109% and 27.1% compared to the counterpart, and the linear ablation rate of fiber-reinforced composite was also optimally reduced by 65.5%. The above results indicate that the novel OMPBPR-based composites are promising materials for application in thermal protection systems.

Flexible Thermal Protection Polymeric Materials with Self-Sensing and Self-Adaptation Deformation Abilities

Based on the strategy of killing two birds with one stone, we introduce thermally expandable microspheres into a silicone rubber matrix to fabricate temperature-responsive controllable deformation materials, which exhibit intelligent deformation properties as well as enhanced thermal protection performance, for dynamic thermal protection in the next-generation morphing aircrafts. The formation of hollow structures endows the material with intelligent thermal management ability and makes the thermal conductivity controllable, meeting the requirements of rapid deformation and excellent thermal insulation. The dimensions of the material adaptively expand with increasing temperature, and a constant 50N force can be provided to ensure reliable sealing. Moreover, benefiting from the synergistic effect of the hollow structure and zinc borate in the ceramization process of the silicone rubber, the 10 mm thick material can reduce the temperature from 2000 to 63 °C, and the mass ablation rate is only 4.8 mg/s. To broaden the application of our material, a sensor with a sandwich structure composed of different functional layers is designed. It is pleasantly surprising to observe that the sensor can provide real-time remote warning of fire and overheating sites with a response time as short as 1 s. This synergistic strategy opens a new possibility to fabricate intelligent thermal protection materials.

Preparation, mechanical properties and long-term ablation resistance of Cf/SiBCN–ZrB2 composites

The Cf/SiBCN–ZrB2 composites were prepared by dipping and winding combined with reactive hot pressing. The flexural strength and fracture toughness reached 261 MPa and 11.96 MPa • m1/2, respectively, through continuous carbon fibers debonding, pulling and bridging mechanisms. Excellent mechanical properties ensured that the Cf/SiBCN–ZrB2 composites remained intact after exposure to a plasma flame with a heat flux of 9.37 MW/m2 for 300 s, with the mass and linear ablation rates of 1.78 mg/s, 1.01 μm/s, respectively. The excellent ablation resistance was due to the formation of dense oxide layers separating the matrix from the plasma flame. The SiO2 formed in the low-temperature areas away from the center was the main ablation-resistant barrier, while the ZrO2/SiO2 double oxide layer formed in the high-temperature region at the center was the major ablation-resistant barrier.

Microstructure and Ablation Behavior of C/C-SiC-(ZrxHf1-x)C Composites Prepared by Reactive Melt Infiltration Method.

C/C-SiC-(ZrxHf1-x)C composites were prepared by the reactive melt infiltration method. The microstructure of the porous C/C skeleton and the C/C-SiC-(ZrxHf1-x)C composites, as well as the structural evolution and ablation behavior of the C/C-SiC-(ZrxHf1-x)C composites, were systematically investigated. The results show that the C/C-SiC-(ZrxHf1-x)C composites were mainly composed of carbon fiber, carbon matrix, SiC ceramic, (ZrxHf1-x)C and (ZrxHf1-x)Si2 solid solutions. The refinement of the pore structure is beneficial to promote the formation of (ZrxHf1-x)C ceramic. The C/C-SiC-(ZrxHf1-x)C composites exhibited outstanding ablation resistance under an air-plasma environment at around 2000 °C. After ablation for 60 s, CMC-1 appeared to possess the minimum mass and linear ablation rates of only 2.696 mg/s and -0.814 µm/s, respectively, which are lower than those of CMC-2 and CMC-3. During the ablation process, a Bi-liquid phase and a liquid-solid two-phase structure were formed on the ablation surface which could act as an oxygen diffusion barrier to retard further ablation, which is responsible for the excellent ablation resistance of the C/C-SiC-(ZrxHf1-x)C composites.

Effect of sintering additives on the sintering and ablation resistance of novel HfO2-ThO2 high-temperature multiphase oxides

To explore the densification of HfO2-ThO2 multiphase oxides and their application prospects in high-temperature environments (over 2500 °C), the sintering promoting mechanism of HfO2-ThO2 multiphase oxides with different sintering additives was systematically studied. By means of XRD, SEM and EDS, the microstructure evolution of HfO2-ThO2 multiphase oxides during sintering was studied, and the sintering promoting effects of sintering additives on the multiphase oxides were systematically explored. The results showed that among the six sintering additives, the HfO2-ThO2 multiphase oxides prepared by using Al2O3 as a sintering additive at 1700 °C under atmospheric pressure had a relative density of nearly 97% and a porosity as low as 2%. By increasing the lattice activity of HfO2, the sintering driving force was increased, and the sintering densification of the multiphase oxides improved. After 30 s of ablation at 2610 °C, compared with HfO2-ThO2 multiphase oxides without sintering additives, the mass ablation rate of the sample with Al2O3 as a sintering additive was reduced by 47.1%. A stable compact structure in which low melting point sintering additives connected the grain boundary to seal the cracks and the high melting point ThO2 phase nailed the triaxial grain boundary was formed in the ablation central region, which has broad application prospects in the field of high temperature sintering.

Response mechanism study of alternate ZrC-10vol.% SiC/ZrC-70vol.% SiC coatings with various sublayer thicknesses for cyclic and long-term thermal exposure

• Alternate coatings with various sublayer numbers were prepared on SiC coated C/C composites using SAPS. • As the alternate number rises, the coating behaved better thermal shock resistance. • The coating with 6 sublayers could offer more than 240 s ablation retardation for the substrate with no visible flaws yielded. • The formed scale with alternate dense/porous structure was capable of not only resisting oxygen diffusion but also weakening the thermal stress. To explore the influence of sublayer numbers on the structure evolution and thermal stress level, an alternate coating consisting of ZrC-10 vol.% SiC and ZrC-70 vol.% SiC sublayers was designed in this work. With a basically consistent general thickness, three coatings constituted by 2, 4 and 6 sublayers were prepared by plasma spraying, which then were assessed using an oxyacetylene torch under cyclic and long-term exposure. The coating with 6 sublayers was supposed to be the one with the best ablation property, finite element analysis also evidenced its least thermal stress among all these samples. After being ablated for 240 s, the linear and mass ablation rates of the coating with 6 sublayers decreased by 51.27% and 14.41% as compared to that with 4 sublayers. Post-test analysis proved the existence of Si-based products, which help the outmost surface to develop a dense profile. Additionally, the yielded alternate dense/porous scale had a preferable toughness, allowing it to maintain a good integrity.

Simultaneous enhancement of mechanical and ablation properties of C/C composites modified by (Hf-Ta-Zr)C solid solution ceramics

In order to improve the mechanical and ablative resistance of C/C composites, (Hf-Ta-Zr)C single-phase solid solution ceramics were introduced into C/C composites by polymer infiltration and pyrolysis (PIP) to fabricate (Hf-Ta-Zr)C modified C/C composites (HTZ). Their mechanical property and ablation resistance were studied. The results showed that HTZ achieved simultaneous enhancement of mechanical property and ablative resistance. Their flexural strength and modulus could reach 219.34 MPa and 24.82 GPa, respectively. In addition, the mass and linear ablation rate of HTZ were 0.379 mg/s and 0.667 µm/s, respectively after the 90 s oxyacetylene ablation. A dense Hf-Ta-Zr-O multiphase oxide layer was formed on the surface of the HTZ during ablation process, which protected the interior modified C/C composites from ablation. Our work expands a rational design of modified C/C composites and broaden the application of solid solution ceramic in the field of ultra-high temperature ablation resistance for carbon or ceramic-based composites.

SPS densification and ablative performance of ZrB2–SiC–ZrC composites derived from the ternary powders by sol-gel

ZrB2–SiC–ZrC (ZSZ) composite ceramics were successfully prepared by sol-gel method combined with spark plasma sintering (SPS) technology. ZrB2–SiC–ZrC multiphase powders with a scale of about 100 nm were firstly synthesized by sol-gel method at 1500 °C. The sintering performance of the sol-gel powders was compared with compositionally similar commercial powders mixture by SPS. The relative densities of the corresponding target composite (ZSZ1) and reference composite (ZSZ2) were reached to 96.2% and 92% under 2000 °C/40 MPa, respectively. The densification curves indicated that the residual SiO2 and B2O3 oxides derived from the precursor triggered the liquid phase sintering mechanism of sol-gel powders above 750 °C. The removal of oxide impurities through carbothermal reduction, and the diffusion and attachment of the liquid phase at the grain boundary jointly promote the densification of ZSZ1. ZSZ1 presented better oxidation/ablation resistance than ZSZ2 during the oxyacetylene ablation tests for 200 s. The mass and line ablation rate of ZSZ1 were only −4.268 × 10−4 g/s and −8.32 × 10−3 mm/s, respectively, which is attributed to be the structure of ZrO2 fine particles uniform distributed in SiO2 melt.

Enhanced flexibility and ablative performance of silicone rubber by constructing an interpenetrating zirconium-containing polysiloxane double network

To achieve uniform distribution of heteroatoms in silicone rubber, further simultaneously improving the flexibility and ablation resistance, polydimethylsiloxane with an interpenetrating zirconium-containing double-network (Zr-PDMS) was prepared. Compared to pure PDMS, the tensile strength and elongation-at-break of Zr-PDMS with interpenetrating double-network were increased by 615.33% and 124.23%, respectively, exhibiting significantly enhanced flexibility. Ablation analysis indicated that Zr-PDMS showed excellent anti-ablation performance, exhibiting obviously decreased mass ablation rate and charring rate. Most importantly, different from the crisp charred layers of pure PDMS as well as ZrO2 blends, Zr-PDMS formed stable and coherent charred layers after ablation tests. The improvement correlated to the in-situ formation of tetragonal ZrO2 in the char layer of Zr-PDMS, which could avoid the generation of defects in the ZrO2 blends char layer were discussed in detail. This work provided a new strategy of high flexible silicon rubber with excellent ablative performance, which can be expected to be well applied in the hypersonic spacecrafts.

Ablation behavior and damage mechanisms of carbon/boron-modified phenolic 2.5D woven composite

2.5D woven structures are of interest in new thermal protection systems for their excellent interlayer properties and structural stability. This paper mainly presents the influence of the reinforcement structure and matrix microstructure on the ablation mechanism and tensile progressive failure of carbon/phenolic 2.5D woven composites. Two types of carbon/boron-modified phenolic 2.5D woven composites, named CDP (1.46 g/cm3) and CLP (1.23 g/cm3), were prepared by adjusting the resin concentration. The specimens were subjected to oxyacetylene flame ablation tests with different ablation times (30 s and 60 s), and the internal features were obtained by X-ray micro-computed tomography (Micro-CT). Tensile mechanical properties of 2.5D woven composites before and after ablation were characterized in combination with acoustic emission (AE). The results indicated that the microstructure of the matrix has an important influence on the ablative properties of the specimens. Specifically, CDP exhibited a better linear ablation rate (0.029 mm/s), while CLP indicated a lower mass ablation rate (0.019 g/s). Furthermore, the strength and modulus of the specimens were reduced after ablation, in which CLP retained higher post-ablation residual properties, 38.82% of the original strength and 68.31% of the original modulus, than CDP. More importantly, the final failure of CDP was controlled by mode I and mode II cracks, whereas that of CLP was only dominated by mode I crack.

Ablation and mechanical properties of ZrC-reinforced PBI resin matrix composites

With the rapid development of laser technology, there is an increasing demand for laser protective materials. Thus, the mechanical and ablation properties of composite materials need to be further enhanced. Herein, solution impregnation and hot-press molding were used to develop composites containing various mass ratios of ZrC to polybenzimidazole (PBI) resin (thickness = 3 mm) for laser ablation applications. The results showed that adding short carbon fiber (SCF) to ZrC/PBI composites improves the ablation and mechanical properties. The ZrC/PBI/SCF composites were ablated using a high-energy continuous laser (7 kW cm−2), and the composites did not burn through. The composites did not peel off or split as the ablation process progressed. With the increase in the ZrC content in the composites, dense oxide layers are formed, enhancing the ablation properties of the composites. The ZrC/PBI/SCF composite (the ZrC/PBI mass ratio = 2:1) exhibited the lowest mass loss (2.24%), mass ablation rate (0.119 mg s−1) and linear ablation rate (0.032 mm s−1). This indicates that ZrC/PBI/SCF composites can be used as protective materials in high-energy continuous laser applications.