Mass Ablation Rate Research Articles

Preparation and properties of C/C−ZrB2−SiC composites by high-solid-loading slurry impregnation and polymer infiltration and pyrolysis (PIP)

Abstract Ultrahigh-temperature ceramics were added to C/C composites to meet their application requirement in a high-temperature oxidizing environment. C/C−ZrB2−SiC composites were fabricated by high-solid-loading slurry impregnation with polymer infiltration and pyrolysis. The dispersion and rheological behavior of ZrB2 slurry and the microstructural, mechanical, and ablation properties of the C/C−ZrB2−SiC composites were investigated. Results indicated that a well-dispersed and low-viscosity ZrB2 slurry was obtained using 0.40 wt.% polyethyleneimine as a dispersant at pH 5. Ceramics were uniformly distributed in the short-cut fiber layer and needle-punched area. The flexural strength of the C/C−ZrB2−SiC composites was 309.30 MPa. The composites exhibited satisfactory ablation resistance under the oxyacetylene flame of 2500 °C, and the mass and linear ablation rates were 0.40 mg/s and 0.91 μm/s, respectively. A continuous and compact ZrO2 layer, which could effectively reduce the diffusion rate of oxygen and protect the composites from being ablated, was formed.

Effects of ZrC/SiC ratios on mechanical and ablation behavior of C/C–ZrC–SiC composites prepared by carbothermal reaction of hydrothermal co-deposited oxides

C/C-ZrC-SiC composites were fabricated by carbothermal reaction of hydrothermal co-deposited oxides and resulted in homogeneous microstructure. The fracture behavior passed from pseudo-plastic to brittle fracture with the increase in ZrC/SiC molar ratios. The composites with a molar ratio of ZrC/SiC≈2:1 presented outstanding ablation resistance with a mass ablation rate of 0.06 mg cm−2 s−1 and a linear ablation rate of 0.13 μm s−1. The optimal ZrC/SiC molar ratio provided a suitable balance of viscosity and flowability of the oxides scale, which not only possessed enough solid ZrO2 to endure the scouring but also had moderate liquid-phase to seal the defects and limited the oxidation.

Mechanical, oxidation and ablation properties of C/(C-SiC)CVI-(ZrC-SiC)PIP composites

A joint chemical vapor infiltration-precursor infiltration and pyrolysis (CVI-PIP) process was used to fabricate C/C-SiC-ZrC composites with different volume ratio of CVI-derived C-SiC. The composite with a C-SiC volume ratio of 0.91 has a higher tensile and flexural strength of 181.7 MPa and 352.8 MPa, respectively, and also exhibits a better anti-oxidation property at 800∼1400 °C for 30 h. After an oxyacetylene ablation for 600 s at ∼2100 °C, the composite with a C-SiC volume ratio of 0.12 possesses a better anti-ablation performance with a linear and mass ablation rates of 0.94 um × s−1 and 0.13 mg × cm-2×s−1, respectively.

Ablation Behavior of the SiC-Coated Three-Dimensional Highly Thermal Conductive Mesophase-Pitch-Based Carbon-Fiber-Reinforced Carbon Matrix Composite under Plasma Flame.

This study is focused on a novel high-thermal-conductive C/C composite used in heat-redistribution thermal protection systems. The 3D mesophase pitch-based carbon fiber (CFMP) preform was prepared using CFMP in the X (Y) direction and polyacrylonitrile carbon fiber (CFPAN) in the Z direction. After the preform was densified by chemical vapor infiltration (CVI) and polymer infiltration and pyrolysis (PIP), the 3D high-thermal-conductive C/C (CMP/C) composite was obtained. The prepared CMP/C composite has higher thermal conduction in the X and Y directions. After an ablation test, the CFPAN becomes needle-shaped, while the CFMP shows a wedge shape. The fiber/matrix and matrix/matrix interfaces are preferentially oxidized and damaged during ablation. After being coated by SiC coating, the thermal conductivity plays a significant role in decreasing the hot-side temperature and protecting the SiC coating from erosion by flame. The SiC-coated CMP/C composite has better ablation resistance than the SiC-coated CPAN/C composite. The mass ablation rate of the sample is 0.19 mg·(cm−2·s−1), and the linear ablation rate is 0.52 μm·s−1.

Thermal shock and ablation behavior of α-cordierite glass-ceramic coating on porous BN/Si2N2O ceramic

Thermal shock and ablation behavior of α-cordierite glass-ceramic coating on porous BN/Si2N2O ceramic substrate were investigated. The coated sample was fractured after 18 thermal shock cycles without peeling off of the coating, while the porous BN/Si2N2O ceramic was fractured after 3 thermal shock cycles. The coated sample has a balter thermal shock resistance than the substrate sample, which can be attributed to the strong interface bonding, the cracks self-healing and thermal barrier of the coating. The ablation surface temperature, mass and linear ablation rates of the porous BN/Si2N2O ceramic were all reduced by the coating, indicating that the substrate had a good ablation resistance under the protection of the coating. In the ablation atmosphere of high-temperature-speed oxyacalylene flame, thermochemical reactions, melting loss, and coupling balween them are the ablation mechanism of the coating/substrate composite.

Ablation characteristics of mosaic structure ZrC-SiC coatings on low-density, porous C/C composites

Mosaic structure ZrC-SiC coatings were fabricated on low-density, porous C/C composites via thermal evaporation and an in-situ method. ZrC was packed in a typical lamellar mode, and the mosaic structure was formed by the deposition of Zr and Si atoms on the shallow surface of the porous C/C composites. Ablation analysis showed that the defects in the coatings originate from the boundary between the ZrC and holes created by the consumption of SiC at 2500 °C. After ablation for 200 s at 3000 °C, a dense ZrO2 layer formed on the coating surface, and the defects were sealed owing to the continuous supply of ablative components. The mass and line ablation rates of the ZrC-SiC coatings were −0.46 ± 0.15 mg cm−2·s−1 and −1.00± 0.04 μm s−1, respectively.

Ablation behavior of boron-modified phenolic resin irradiated by high-energy continuous-wave laser and its evolution of carbon structure

Despite many years of use of boron-modified phenolic resin (BPF) in the aerospace and auto industry, it is still unknown if such resin can be used in extreme environments, especially under exposure to high energy continuous-wave (CW) laser that can totally destroy many traditional materials in several seconds. Compression molded BPF plates are tested with high energy CW laser to study the laser ablation behavior. Results reveal that the laser parameters including irradiation time and laser power density have a great effect on the ablation morphology and mass ablation rate. BPF keeps decomposing into residual char due to the high temperature caused by laser. The graphite structure of residual char is gradually improved during laser irradiation, resulting in improved thermal stability of residual char. In addition, the micro-morphologies reveal that the residual char possess porous structure which leads to the thermal insulation property and minimizes the ablation damage propagating into the BPF bulk. Both the improved thermal stability and the thermal insulation property of the residual char can mitigate the ablation damage caused by the high energy CW laser.

Ablation behaviors and mechanism of ultra‐thick anti‐oxidation layer coating on carbon‐bonded carbon fiber composites

AbstractTo enhance the oxidation resistance capability of the carbon‐bonded carbon fiber composites (CBCFs), a silicide ultra‐thick coating as high as 1.6 mm with gradient structure is designed and fabricated via a multi‐step rapid sintering method. Compared with other ceramic layers on carbon fiber‐based composites, ultra‐thick anti‐oxidation layer coated‐CBCFs have the lowest thermal conductivity. Additionally, ablation behaviors of the ultra‐thick ceramics layer coated‐CBCFs under the oxyacetylene torch are also investigated. After being exposed to oxyacetylene torch, the ultra‐thick ceramics layer coated‐CBCFs possess a linear rate range from 0.6 to 1.2 μm/s, while a mass ablation rate ranges from 4.95 × 10−5 g/m2 s to 1.45 × 10−3 g/m2 s.

Ablation resistance of TaC-modified HfC coating prepared by supersonic plasma spraying for SiC-coated carbon/carbon composites

Abstract A HfC-TaC composite coating was prepared on SiC-coated C/C composites by supersonic atmosphere plasma spraying (SAPS) to improve their ablation resistance. The ablation resistance was evaluated under oxyacetylene torch with heat flux of 2.38 MW/m2 and 4.18 MW/m2 respectively, and the effect of TaC on microstructure and phase composition of the coating was investigated. Results showed that TaC-modified HfC coating exhibited good ablation resistance under the torch with heat flux of 2.38 MW/m2 and its mass and linear ablation rates were -0.35 mg/s and -1.05 μm/s separately, which is ascribed to the formation of continuous oxide film including phases like Hf6Ta2O17 and Ta2O5. Crack propagation in the coating was inhibited due to the phase transition restriction of HfO2 by Ta2O5, and cracks and holes in the oxide layer could be repaired by molten Ta2O5 and Hf6Ta2O17. However, the occurrence of ablation crater on the surface of HfC-TaC coating is mainly attributed to the unsatisfactory scouring resistance of the oxide film under heat flux of 4.18 MW/m2.

Multi-walled carbon nanotubes as secondary fibre fillers for property improvement of short carbon fibre-reinforced silicone rubber

To improve the properties of room temperature vulcanized (RTV) silicone rubber, functional multi-walled carbon nanotubes (MWCNTs) and short carbon fibres were added into the RTV silicone rubber as hybrid fibre fillers. The functionalized MWCNTs were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The mechanical, thermal and ablative properties of the fabricated RTV silicone rubber composites were investigated. Their properties were enhanced by adding the functionalized MWCNTs with appropriate contents. The tensile strength and tear strength of the composites are improved from 4.0 MPa and $$20.3\hbox { kN m}^{-1}$$ to 4.3 MPa and $$21.3\hbox { kN m}^{-1}$$, respectively, when the MWCNT content increased from 0 to 0.5 phr. In addition, the decomposition temperatures at the onset point and 50% mass loss increased from 493.4 and $$564.4{^{\circ }}\hbox {C}$$ to 498.8 and $$612.4{^{\circ }}\hbox {C}$$, respectively. The mass and line ablation rates also decreased from $$0.062\hbox { g s}^{-1}$$ and $$0.148\hbox { mm s}^{-1}$$ to $$0.059\hbox { g s}^{-1}$$ and $$0.145\hbox { mm s}^{-1}$$, respectively.

Implosion performance of subscale beryllium capsules on the NIF

Many inertial fusion designs use capsules made of beryllium, as its high mass ablation rate is advantageous. We present the first systematic experimental study of indirectly driven beryllium capsules with a cryogenic deuterium-tritium fuel layer. “Subscale” capsules, 80% of the nominal National Ignition Facility point design radius, show optimal performance with the remaining mass of ∼6–7%. A buoyancy-drag mix model explains the implosion performance, suggesting that fuel-ablator mix is the dominant degradation mechanism. Increasing the capsule scale is predicted to reduce the impact of fuel-ablator mix and achieve high performance.

Gel reactive melt infiltration: A new method for large-sized complex-shaped C/C components ceramic modification

Abstract To widen the applications of conventional reactive melt infiltration (RMI) in large-sized complex-shaped C/C components, an ingenious process of gel-RMI (GRMI) was proposed in this study. The arching C/C SiC composite was prepared successfully using GRMI method with polycarbosilane (PCS) Si90Zr10 (Si: 90 at.%; Zr:10 at.%) sol. The porosity rate of the C/C preform decreased from 18.5% to 2.9%, while the density was raised from 1.40 g·cm−3 to 2.05 g·cm−3 after GRMI. The reason why C/C preform has been significantly densified is as follow: the PCS in PCS-Si90Zr10 sol formed SiC aerogel skeleton after pyrolysis, and then the Si90Zr10 powders were melted and released from the SiC aerogel into the C/C preform body when the temperature reached the melting point of Si90Zr10 alloy. The obtained C/C SiC composite showed a pseudo-ductile rupture characteristic distinguished from that of the C/C preform, and its bending strength was significantly improved from 104.2 MPa of the C/C preform to 258.8 MPa. The C/C SiC composite had a far lower mass ablation rate of 0.75 mg·s−1 than that of C/C preform, 23.30 mg·s−1. Moreover, the GRMI was preliminarily applied in ceramic modifying nozzle-like C/C preform, and the result showed that the nozzle-like C/C preform was successfully densified from 1.3 g cm−3 to 1.96 g cm−3. The GRMI process has great potential in ceramic modifying large-sized complex-shaped C/C components.

Microstructure and ablation property of gradient ZrC SiC modified C/C composites prepared by chemical liquid vapor deposition

Chemical liquid vapor deposition was adopted to fabricate gradient ZrCSiC modified C/C composites, and the microstructure and ablation resistance were studied. Results displayed the content of SiC decreased from the composites edge to the center but that of ZrC increased, indicating SiC and ZrC ceramics have the gradient distribution in the composites. The gradient composites possessed a low CTE and high thermal conductivity. The low CTE restricted the formation and expansion of defects, which could slow the oxygen diffusion in the composites. The high thermal conductivity could transfer the heat quickly in ablation process, which reduced the heat accumulation on the ablation surface and weakened the thermal erosion. Therefore, the gradient composites possessed an outstanding anti-ablation property at two heat fluxes. Compared with the uniformed distribution composites, the linear and mass ablation rates of the gradient composites decreased by 60.9% and 66.7% at heat flux of 2.38 MW/m2 and decreased by 55.9% and 67.2% at heat flux of 4.18 MW/m2. Because of the gradient distribution, porous ZrO2 coating, ZrO2SiO2 coating and SiO2 coating with SiO2 nanowires were generated on the ablation center, ablation transition zone and ablation edge, respectively. These coatings isolated the sample surface from the flame and inhibited the transport of oxygen into the sample inner.

Enhanced Anti-ablation and Alkali Corrosion Resistance of Graphene Oxide Modified Urea-Melamine-Phenol Formaldehyde Composites Reinforced by R-Glass Fiber

Graphene oxide (GO) modified urea-melamine-phenol formaldehyde resin (UMPF) was reinforced by R-glass fiber woven. GO was reduced by UMPF to reduced graphene oxide (RGO). Transmission electron microscopy (TEM), atomic force microscope (AFM), and scanning electron microscopy (SEM) were used to analyze the morphology and dispersibility of RGO in UMPF. Compared with the pure R-glass fiber woven reinforced urea-melamine-phenol formaldehyde resin (RFW-UMPF), the thermal conductivity and carbon residual value (CRV) of R-glass fiber woven reinforced GO modified urea-melamine-phenol formaldehyde resin (RFW-GO/UMPF) (0.8 wt% RGO) at 800 °C were increased by 6.3% and 20%, respectively. Anti-ablation researches revealed that with 0.8 wt% RGO loading, the linear ablation rate (LAR) and mass ablation rate (MAR) of RFW-GO/UMPF deceased by 25.6% and 12.6%, respectively. Moreover, the enhancement mechanism of RGO on anti-ablation properties and alkali corrosion resistance (ACR) performances were systematically discussed.

Characteristics of ZrC Barrier Coating on SiC-Coated Carbon/Carbon Composite Developed by Thermal Spray Process.

A thick ZrC layer was successfully coated on top of a SiC buffer layer on carbon/carbon (C/C) composites by vacuum plasma spray (VPS) technology to improve the ablation resistance of the C/C composites. An optimal ZrC coating condition was determined by controlling the discharge current. The ZrC layers were more than 70 µm thick and were rapidly coated under all spraying conditions. The ablation resistance and the oxidation resistance of the coated layer were evaluated in supersonic flames at a temperature exceeding 2000 °C. The mass and linear ablation rate of the ZrC-coated C/C composites increased by 2.7% and 0.4%, respectively. During flame exposure, no recession was observed in the C/C composite. It was demonstrated that the ZrC coating layer can fully protect the C/C composites from oxidation and ablation.

The role of incidence angle in the laser ablation of a planar target

The effect of the laser ray incidence angle on the mass ablation rate and ablation pressure of planar inertial confinement fusion (ICF) targets is explored. In this work, a modified version of the textbook model of laser ablation [Manheimer et al., Phys. Fluids 25, 1644 (1982)] is used to demonstrate that the mass ablation rate and ablation pressure scale with the 4/3 and 2/3 power of the cosine of the laser ray incidence angle relative to the target normal. Using an idealized planar model of ablation, it is demonstrated that constant irradiance is insufficient to produce similar velocities of a target when comparing cases driven at different incidence angles. Additionally, the effect of the incidence angle on the absorption fraction is demonstrated and it is shown that a longer duration is needed to achieve maximum absorption for greater angles. This further affects the mass ablation rate and ablation pressure in the first nanosecond of ablation. These results, when extrapolated, may provide insight into the variation of drive conditions encountered due to incidence in polar direct drive ICF.

Effect of duty cycle on microstructure, composition and ablation resistance of tungsten-cobalt coatings prepared by electrodeposition

In order to explore the ablation resistance of the tungsten-cobalt coating, tungsten-cobalt coatings with different tungsten contents were prepared on the surfaces of PCrNi3MoVA steels by electrodeposition under different duty cycles. The results show that the tungsten content in the coating increases first and then decreases with the increase of the duty cycle. When the duty cycle is 30%, the tungsten content is the highest (43.37wt%). The grain size increases with the increase of the duty cycle. The sample prepared at the duty cycle of 30% has the best ablation resistance, and its relative mass ablation rate and relative line ablation rate are 0.08% and 0.89%, respectively. The effect of duty cycle on ablation resistance of the tungsten-cobalt coating is mainly achieved by affecting the tungsten content and the grain size in the coating. Higher tungsten content and denser crystal, the ablation resistance of tungsten-cobalt coating is better.

A Multilayer SiC/ZrB2/SiC Ablation Resistance Coating for Carbon/Carbon Composites

To improve the ablation resistance of carbon/carbon (C/C) composites, a new SiC/ZrB2/SiC multilayer coating is designed and fabricated by a three‐step method of pack cementation, supersonic plasma spraying, and low pressure chemical vapor deposition. In this study, ablation behavior of SiC/ZrB2/SiC coating is investigated under oxyacetylene torch environment. Oxyacetylene ablation testing results show that the linear ablation rate and mass ablation rate of SiC/ZrB2/SiC coated C/C composites are only −5.0 × 10−4 mm s−1 and −9.6 × 10−4 g s−1, respectively, for 20 s ablation under heat flux of 2400 kW m−2. However, the ablative linear rate of ZrB2/SiC coated C/C composites is 7.5 × 10−4 mm s−1 and the ablative mass rate is zero. The better ablation resistance is mainly attributed to a molten SiO2–ZrO2 hybrid glassy layer formed after ablation on the surface of the composites and acting as thermal barrier layer inhibiting inward diffusion of oxygen.

Effects of ZrN and W Particle Sizes on the Mechanical and Ablation Properties of ZrN/W Composites

Tungsten composites reinforced with 20 vol% of different particle sizes of ZrN and W powders were prepared by ball milling and spark plasma sintering. Correlations between the W and ZrN grain sizes, and the mechanical and ablation properties of the composites, were investigated. The improved mechanical properties of the ZrN/W composite containing fine ZrN and fine W grains is attributed to a W grain refinement effect and a ZrN particle strengthening effect. The mass ablation rate of the composites containing fine ZrN and coarse W grains significantly decreased, i.e., 36% lower that of the composite containing fine ZrN grains and fine W grains. The improved ablation resistance is attributed to better surface coverage of the ZrO2 oxide layer because of uniformly dispersed fine ZrN particles, and to less oxidation and sweeping away of the W matrix during ablation through grain boundary diffusion suppression caused by the large W grain size.

Microstructure and ablation properties of SiC/ZrB2–SiC/ZrB2/SiC multilayer coating on graphite

To improve ablation resistance of graphite, SiC/ZrB2-SiC/ZrB2/SiC coating was prepared by pack cementation and CVD. SiC/ZrB2–SiC/ZrB2/SiC coating showed excellent ablation resistance, its mass and linear ablation rate were only 0.27 mg/s and 0.57 μm/s after ablation under oxyacetylene flame for 298 s. CVD ZrB2/SiC layer significantly improved the ablation resistance of SiC/ZrB2–SiC/ZrB2/SiC coating. During ablation, the surface temperature gradually increased until it stabilized around 2220 °C. The surface temperature response in different stages was affected by layered microstructure evolution and emissivity of different layers.