Mass Ablation Rate Research Articles

Microstructure dependent ablation behaviour of precursor derived SiOC ceramic foam for high temperature applications

Ablation behaviour of poly(hydridomethylsiloxane) derived open and closed porous structured SiOC ceramic foams was evaluated using oxy-acetylene flame at 1500 °C for various time durations. X-ray diffraction and scanning electron microscopy analyses of ablated SiOC ceramic foams revealed the formation of a thin protective SiO2 layer inhibiting further oxidation. The closed porous structured SiOC ceramic foams exhibited very low mass ablation rate in contrast to open porous structured SiOC ceramic foams owing to the differences in thermal energy dissipation mechanism. The feasibility of the plausible foam reduction reactions pertaining to the ablation mechanism was further investigated by computing the Gibbs energy and HR-TEM analysis. The study corroborated the significance of tailoring the microporous structured SiOC ceramic foams as potential thermal protection material for high temperature applications.

Study on the Ablation Properties of Nano-graphite Modified EPDM Insulators

To improve the anti-ablative property of EPDM-based composites, nano-graphite powder as anti-ablation filler was introduced to optimize the EPDM insulation material formulas. Characterization of anti-ablation performance showed that the composite at the nano-graphite content of 10phr exhibited the best anti-ablation and mechanical performances, such as: a linear ablation rate of 0.062 mm/s, a mass ablation rate of 0.048 g/s, tensile strength of 5.69 MPa and Elongation at break of 391.2%. The nano-graphite was proven to be an effective material which is beneficial to improve the anti-ablation of the EPDM composites.

Ablation behavior and thermal conduction mechanism of 3D ZrC–SiC-modified carbon/carbon composite having high thermal conductivity using mesophase-pitch-based carbon fibers and pyrocarbon as heat transfer channels

A three-dimensional ZrC–SiC-modified Carbon/Carbon composite having high thermal conductivity is prepared to significantly reduce the ablation rate and improve dimensional stability of composites used in thermal protection systems. The mesophase-pitch-based carbon fibers/pyrocarbon skeleton is designed as the thermal diffusion channel using the intermediate state mesophase-pitch-based carbon fibers and chemical vapor infiltration method . After successive graphitization and polymer precursor impregnation and pyrolysis, the obtained ZrC–SiC-modified carbon/carbon composite exhibits a high thermal conductivity of 206.5 W m −1 K −1 in the X(Y) direction. The ablation results indicate that the composite exhibits a surface temperature of 241 °C, which is lower than that of the composite without mesophase-pitch-based carbon fibers, thus verifying the improved ablation resistance. The linear and mass ablation rates of the composite are found to be 0.33 μm s −1 and 0.56 mg cm −2 s −1 , respectively. The thermal conduction mechanism of the ZrC–SiC-modified carbon/carbon composite near the ablation center is investigated to show the combined phonon heat conduction and thermal radiation . This study provides a protocol for the design and construction of modified carbon/carbon composites having high thermal conductivity for application in hypersonic vehicles . • A C/C–ZrC–SiC composite with a thermal conductivity of 206.5 W m −1 K −1 in the ablation direction was fabricated. • The CF MP /C skeleton acted as the thermal diffusion channels during ablation. • The composite showed improved ablation resistance due to a reduction in surface temperature.

MoSi2-HfC/TaC-HfC multi-phase coatings synthesized by supersonic atmospheric plasma spraying for C/C composites against ablation

To improve the ablation resistance of C/C composites, MoSi2-HfC/TaC-HfC (MH/TH) bilayer coatings were synthesized on SiC coated C/C composites. Results showed that the mass and linear ablation rate of MH/TH coatings were 0.236 mg/s and 1.026 µm/s, respectively. The excellent performance of MH/TH coatings was attributed to the combination of TH and MH layers. The external TH layer could create Ta2O5 and Hf6Ta2O17 glassy phase to protect the internal layer and prevent the formation of destructive MoO3. Meanwhile, the decomposition of the internal MH layer to produce SiO2 diffusion outward could retard the destruction of the external coating.

Silicone-grafted epoxy/carbon fiber composites with superior mechanical/ablation performance

Improving the ablation-resistance of carbon fiber/epoxy composites is essential for structural-thermal protection integrated materials. In this work, silicone-grafted epoxy resin with high char yield was synthesized, and carbon fiber (CF) reinforced composites with different silicone content are manufactured. The effect of the pyrolysis behavior of the silicone-grafted epoxy on the mechanical properties and ablation resistance of the composites has been systematically investigated. The high-temperature properties were characterized by Interlaminar shear strength (ILSS) of unidirectional composites treated at 400 °C and 600 °C respectively, while the ablation-resistance properties were assessed by the mass and linear ablation rate of laminated composites at 1, 2.5, and 4 MW/m2 ablative heat flow density. It was found that the ILSS was improved by 228.13% and 151.79% after pyrolysis. Meanwhile, the silicone-grafted epoxy/CF composites exhibit a better ablation performance especially in 1 MW/m2. These results show that silicone-grafted epoxy/CF composites are expected to achieve the integration of high strength and ablation resistance as well as the integration of structural-thermal protection materials.

Preparation and ablation behavior of HfC-SiC co-deposited coatings with different proportions

HfC-SiC coatings have promising applications in the field of ablation protection for carbon-carbon (C/C) composites. In this work, HfC-SiC coatings with different ratios were designed and successfully prepared by low pressure chemical vapor co-deposition using HfCl4-MTS-CH4-H2-Ar system under the guidance of thermodynamic calculations. The phase composition, microstructure, and ablation behavior of HfC-SiC coating with different phase proportions were investigated. The coating with HfC/SiC ratio of 1:1 showed the best ablation resistance after ablation for 90 s, and its mass and linear ablation rates of HfC-SiC coating was only 1.016 ± 0.12 mg/s and 0.998 ± 0.08 µm/s, respectively.

Effect of microstructure on the ablation behavior and mechanical properties of CVD-HfC coating

HfC coatings with different microstructure were successfully fabricated by chemical vapor deposition. The mechanical properties and ablation resistance of HfC coatings were evaluated, and the coefficient of thermal expansion (CTE) and ablation behavior of the as-prepared coatings were investigated in detail. Results showed that HfC coating with the dense coarse columnar structure exhibits good mechanical properties, and the equiaxed structure has a low CTE. The fine columnar structure coating has better ablation resistance compared with other microstructures, and the mass ablation rate and linear rate are only 2.02 mg/s and 1.25 µm/s after ablation for 90 s, respectively.

Effects of inorganic nanofibers and high char yield fillers on char layer structure and ablation resistance of ethylene propylene diene monomer composites

Influences of fillers [including multi-walled carbon nanotubes (MWCNTs), SiC nanowires, methyl-polyhedral oligomeric silsesquioxanes (methyl-POSS) and boron phenolic resin] on the characteristics of porous structure in char layers of ethylene propylene diene monomer (EPDM) composites were studied using experimental solid rocket motor (SRM). Comparing to basic formulation (Porosity: 78.25%), char layers of fillers formulation present lower porosity (Ranging from 64.03% to 67.69%) and showed significant trends of overall or local densification. Further analysis revealed different densification mechanisms: CNTs and SiC nanowires can promote chemical vapor deposition (CVD) reaction in char layers and reduce its porosity, which can be referred as “CVD-promotion densification”; boron phenolic resin is relatively high in char yield and char residue would densify the microstructure of char layers, which can be referred as “char residue densification”; methyl-POSS show a combination of both mechanisms, which lead to the lowest mass ablation rate [170.4 g/(m2·s)] and the best ablation performance.

Effect of Organo Montmorillonite Nanoclay on Mechanical Properties Thermal Stability and Ablative Rate of Carbon fiber Polybenzoxazine Resin Composites

Organo-Montmorillonite (o-MMT) nanoclay added polybenzoxazine resin (type I composites) were prepared with varying amounts of clay (0, 1, 2, 4 and 6 wt %). Clay dispersion, changes in curing behaviour and thermal stability were assessed in type I composites. Findings from these studies of type I composites were used to understand thermal stability, mechanical, and mass ablation rate behaviour of nanoclay added carbon fiber reinforced polybenzoxazine composites (type II). Interlaminar shear strength and flexural strength of type II composites increase by 25% and 27%, respectively at 2 wt% addition of clay. An oxy-acetylene torch test with a constant heat flux of 125 w/cm2 was used to investigate mass ablation rate of type II composites. The ablation rate has increased as the weight percentage of clay has increased. This is contradicting to type I composites with up to 6 wt% clay and type II composites with up to 4 wt% clay, which have improved thermal stability. The microstructure of the ablated composites was examined using scanning electron microscopy. Increased ablation rates are due to the reaction of charred matrix with nanoclay, which exposes bare fibers to the ablation front, resulting in higher mechanical erosion losses.

Ordered graphitized ceramic layer induced by liquid crystal epoxy resin in silicone rubber composites with enhanced ablation resistance performance

In ablation-resistant silicone rubber composites, the strengths of the ceramic layers strongly affect the ablation rates of the materials, and the order of graphite carbon in the ceramic layers has an important impact on the strength of ceramic layers. In this study, a series of 4,4′-bis(3-(oxiran-2-ylmethoxy)benzyl)-1,1′-biphenyl(BER) modified silicone rubber composites were prepared to improve the order of graphite carbon in the ceramic layers of composites after ablation. The introduction of SiO 2 nanoparticles and carbon fibers as ablation fillers made the material ceramized and formed strong ceramic layers during the ablation process. Characterization of ablation performance shown that the 20BER composite exhibited the best ablation resistance performance: a linear ablation rate of 0.0464 mm/s and a mass ablation rate of 0.0500 g/s. Mechanical performance characterization shown that the 20BER sample also exhibited an excellent tensile strength of 2.013 MPa and a ceramic layer strength of 13.15 MPa. Raman measurement indicated that the addition of BER led to more orderly graphitic carbon structures during pyrolysis and increased the strength of ceramic layers. SEM, mercury intrusion and thermal conductivity measurements indicated that the pore volume, porosity and total pore area of ceramic layers with the BER component were all higher than the 0BER sample. The BER was proven to be an effective material which is beneficial to improve the ablation resistance and played an important role in the process of ceramization of the silicone rubber composites. These silicone rubber composites have the potential to be applied to the surface coating of aircraft. • The average ablation rate was reduced significantly. • The liquid crystal led to more orderly graphitic carbon structures during pyrolysis. • The liquid crystal component increased the strength of the ceramic layers. • More holes generated could prevent the flame from spreading to deeper layers of the sample.

Polymer-metal slurry reactive melt infiltration: A flexible and controllable ceramic modification strategy for irregular C/C components

Herein, we investigate the applicability of the polycarbosilane (PCS)–metal slurry reactive melt infiltration (RMI) process to various metals. The slurry exhibiting the best ceramized ability was used to examine the relationship between the ceramic thickness and reactive time, ceramic thickness and reactive temperature, and infiltration depth and slurry-coating thickness. The results show that the thickness of the ceramic layer increases with reactive time and temperature and the infiltration depth increases with the coating thickness. PCS–Si90Zr10 slurry RMI was selected to modify cylindrical nozzle C/C preforms, and dense C/C–SiC–ZrC composites with a density of ~2.05 g cm−3 were obtained. Owing to the good control of the PCS–Si90Zr10 slurry RMI on the interface, matrix, and carbon fiber of the as-received cylindrical composites, the bending strength of the C/C–SiC–ZrC composites was as high as 306.4 MPa, which is considerably higher than that of a C/C preforms (70.4 MPa). Considering the ablation resistance, the mass and linear ablation rates of the C/C–SiC–ZrC composite (~0.29 mg s−1 and ~2.48 × 10−3 mm s−1, respectively) were similar to those of the composites prepared using traditional RMI (~0.23 mg s−1 and ~2.29 × 10−3 mm s−1). The proposed polymer–metal RMI is more suitable for the modification of C/C preforms with thin-wall structures owing to its advantages including precise control of infiltration dose and flexible operation of slurry coating. Furthermore, it is suitable for the local modification of C/C components.

Effects of difunctional reactive polyhedral oligomeric silsesquioxane on the properties of EPDM

AbstractBifunctional reactive polyhedral oligomeric silsesquioxane (POSS) of 3, 13‐divinyl octyphenyl silsesquioxane (DV‐DDSQ) and 3, 13‐dihydro octyphenyl silsesquioxane (DH‐DDSQ) were used as additive to modify ethylene‐propylene‐diene rubber (EPDM), and double vinyl groups or active hydrogen groups of bifunctional reactive POSS (brPOSS) underwent a cross‐linking reaction with the active hydrogen groups and double bonds of EPDM, to investigate the effect of brPOSS regulating functional reaction group on the properties of EPDM. Crosslinking density, mechanical properties, thermal stability and ablation performance of brPOSS modified EPDM were investigated, and the pyrolysis behavior and surface structure of modified EPDM was analyzed by X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Furthermore, the ablation performance of brPOSS modified insulation based on EPDM was investigated. The results showed that the tensile strength of EPDM/DV‐DDSQ and EPDM/DH‐DDSQ increased by 35.8% and 55.3% respectively compared with EPDM; the tear strength increased by 6.4% and 5% than that of EPDM. Moreover, the 5% initial thermal decomposition temperature based on thermogravimetric analysis (TGA) and mass (or linear) ablation rate ablative performance of brPOSS modified EPDM were optimized to a certain extent, and the ablative performance of brPOSS modified insulation based on is significantly improved, the mass ablation rate of DV‐DDSQ/insulation and DH‐DDSQ/insulation decreased by 35.4% and 41.6% respectively, and linear ablation rate decreased by 38.2% and 39.4% respectively.

Preparation and ablation properties of SiC nanowire-reinforced ZrC–SiC coating-matrix integrated C/C composites

A modification of the precursor infiltration pyrolysis (PIP) method was explored to prepare the integrated doped ceramic matrix and coating by the added SiC nanowires layer and shape-stabilization process. The epitaxial layer of SiC nanowires provided surficial attachments for the precursor. And the shape-stabilization process aggregated loose ceramic particles into a coating. Then the SiC nanowire-reinforced ZrC–SiC coating-matrix integrated C/C (S/SZ-CZ/C) composite was simply prepared by the modified PIP method. The bonding strength between the coating and matrix of the S/SZ-CZ/C composite was improved. Through the ablation test, the mass and linear ablation rate of the S/SZ-CZ/C composite were 0.46 mg/s and 0.67 μm/s, which were 60.34 % and 74.91 % lower than those of the SiC nanowire-reinforced C/C–ZrC (S/CZ/C) composite, respectively. The integration of the coating and matrix enabled the formation of a continuous oxide layer of molten SiO2 and ZrO2 in the ablation process, which helped to block the oxygen and heat during the ablation test. Thus the ablation resistance of the materials was systematically and effectively improved.

Effect of magnetic field-dependent effective thermal conductivity of melted layer on nanosecond laser ablation of copper and formation of nanoparticles at atmospheric air pressure

For a nanosecond laser ablation of metals, the key physical phenomena involved are thermal evaporation, melt ejection, instability of the molten metal, etc., which depend on the initial temperature evolution in the metal. Understanding the evolution of temperature of the metal needs an effective simulation. In the present paper, we report on the finite element method-based simulation of nanosecond laser ablation of copper in the absence and presence of the magnetic field. Our studies showed that the effective thermal conductivity of the melted layer on the copper surface in the presence of the magnetic field affects the viscosity of the layer, mass ablation rate, instability, and then particle formation. The calculations showed that the condensed nuclei of large critical size are produced in the magnetic field. It is attributed to an increase in the collision rate of plasma particles in the magnetically confined plasma. The simulations are in good agreement with the experimentally measured values.

Ablation behavior and mechanisms of 3D Cf/ZrB2-SiC composite applied in long-term temperature up to 2400 °C

To evaluate the long-term ablation behavior and mechanism of carbon fiber reinforced ultra-high temperature ceramics, 3D Cf/ZrB2-SiC composite with homogeneous architecture was prepared via vibration-assisted slurry impregnation combined with precursor infiltration and pyrolysis. The intact structure of sample was remained owing to the triple oxide layers after ablation at Tmax = 2440 °C for 500 s, a dense ZrO2 layer owing to particle accumulation and sintering, followed by a dense SiO2+ZrO2 layer due to inhibition in diffusion of glassy SiO2 and next porous ZrO2 layer, leading to superior ablation resistance with linear and mass ablation rates of 1.8 × 10−4 mm/s and 1.08 × 10-5 g/mm2·s, respectively.

Mechanical and ablation properties of a C/C-HfB2-SiC composite prepared by high-solid-loading slurry impregnation combined with precursor infiltration and pyrolysis

An improved high-solid-loading slurry impregnation process was developed to introduce HfB2 particles into a low-density C/C preform efficiently, and precursor infiltration and pyrolysis process was used for densification to obtain a C/C-HfB2-SiC composite. The microstructure characterization revealed that HfB2 particles uniformly filled the pores in the C/C preform, and SiC well densified the interstices between HfB2 particles and the small pores in the carbon fiber bundles. After being tested, the C/C-HfB2-SiC composite had a density of 4.07 g/cm3 and a bending strength of 344.8 MPa, and exhibited a non-brittle fracture behavior. After ablation with oxyacetylene flame at 2500 ℃ for 120 s, the mass ablation rate and linear ablation rate of the C/C-HfB2-SiC composite were 0.5 mg/s and 0.415 μm/s, respectively. The good ablation performance is attributed to the hindering effect of the HfO2 scale on oxygen diffusion at high temperature.

Dynamics of laser produced plasma from foam targets for future nanolithography devices and X-ray sources

Foam targets are expected to be more efficient candidates than solid targets for laser produced plasma (LPP) for extreme ultraviolet (EUV) and X-ray radiation sources due to the expected plasma conditions that can be optimized regarding plasma opacities, volumetrics heating effects, and the produced ions debris characteristics. In this paper, a comparison of ion dynamics between low-density foam and solid Ni plasma was systematically investigated at CMUXE. The foam Ni target (density 0.6 g/cm3) and solid Ni target (density 8.9 g/cm3) were irradiated with 1064 nm Nd:YAG laser in vacuum. A Faraday cup (FC) was used to record the ion flux and time-of-flight (TOF) signals. A lower and wider TOF signal was observed for foam Ni plasma on the time scale. The average ion energy and peak of the TOF signal of solid Ni plasma were much higher than that of the foam Ni plasma. However, the total charge values between foam and solid Ni plasma were comparable indicating a more volumetric absorption of laser energy for foam Ni. The average ion energy and peak of the TOF signal of solid Ni showed a stronger angular and laser energy dependence than that of foam Ni. The plume shape of the solid Ni plasma appeared as an oblong ellipse at each time, while that of foam Ni plasma tended to be more circular, especially at early times. The results of mass ablation rate were consistent with the FC signals and showed a more intense plasma shielding for solid Ni.

Investigation on the oxidation and ablation behaviors of HfB2-SiC-Si/SiC-Si coatings for carbon/carbon composites

Oxidation and ablation behaviors of HfB2-SiC-Si/SiC-Si coatings fabricated by dipping-carbonization joint gaseous silicon infiltration on cubic and nose-shaped carbon/carbon substrates were investigated. After 30 thermal cycles between 1500 °C and room temperature, the mass gain of the coated sample was 0.91 %, and the mass gain was 2.62 % after oxidation at 1500 °C for 870 h. The coated nose-shaped sample exhibited good anti-ablation properties at 1800 °C–2000 °C under oxyacetylene flame. Especially at 1800 °C, the mass ablation rate was −0.073 mg/s. Although the nose tip suffered the most serious corrosion, HfO2 scale surrounded by Hf-Si-O glass could withstand the oxyacetylene torch scouring.

Ablation behavior of SiC whisker and ZrB2 particle-filled ZrO2 sol-gel composite coating under high-intensity continuous laser irradiation

In this study, laser ablation-resistant composite coating consisting of zirconium diboride (ZrB2) particulate and silicon carbide (SiC) whisker with zirconia (ZrO2)-sol binder was prepared to meet requirements of anti-laser ablation ability. Laser ablation behavior of as-prepared coating was investigated under varying laser powers. Results revealed that the highest back-surface temperature of coated aluminum substrate was only 150 °C when irradiated at a power density of 6.3 kW/cm2 for 10 s, which is below the maximum allowable temperature of the aluminum alloy substrate (200 °C). After ablation for 10 s, the mass ablation rate of the composite coating was 4.45 mg/s. Apparently, the composite coating exhibited outstanding ablation resistance against high-intensity continuous laser irradiation. At initial stage of ablation, combination of self-healing effect of liquid ZrO2–SiO2 layer and volatilization of B2O3 provide effective joint protecting mechanism. With increasing ablation time, ZrO2 ceramic barrier layer, product of the pyrolysis of ZrO2 gel and ZrB2 filler, becomes progressively more important in maintaining excellent laser ablation resistance behavior, which is normally effective at around ablation pit.

Ablation and heat insulation performances of nose-shaped ZrC-C composites with gradient pore structure

Nose-shaped ZrC-C composites with gradient pore structure (ZrC-CGS) were successfully prepared by isothermal chemical vapor infiltration using ZrC skeleton as preform. Pyrolytic carbon with medium texture was deposited around ZrC skeleton. From the top to back, the porosity of the ZrC-CGS composites increased gradually from 0% to 62.9%. Compared with the ZrC-C composites with dense structure (ZrC-CDS), the mass ablation rate of the ZrC-CGS composites decreased by 15.3% and the heat resistance capacity increased by 45.6%, and their coefficients of thermal expansion decreased obviously in the temperature range of 200–1500 °C. The simulation results showed that the residual thermal stress and back temperature of the ZrC-CGS composites are lower than those of the ZrC-CDS composites. This work provides an effective strategy for designing and preparing ultra-high temperature composites having both ablation and heat insulation performances by controlling the pore structure and distribution.