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graphite composite nozzle-throats in a solid rocket motor environment
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Ablation behavior of Al20Si/graphite composite nozzle-throats in a solid rocket motor environment Hao Liu, Pengchao Kang∗, Wenshu Yang, Ningbo Zhang, Yue Sun, Gaohui Wu∗∗ School of Material Science and Engineering, Harbin Institute of Technology, Harbin, 150001, China
A R T I C LE I N FO
A B S T R A C T
Keywords: A. Pressure infiltration C. Ablation resistance D. Al20Si/Graphite composites E. Engine components
Small solid rocket motors (SRM) require low density, low ablation nozzle-throat materials. In the present study, Al20Si alloy was infiltrated into the porous graphite matrix to develop Al20Si/graphite composites by pressure infiltration method. The ablation behavior of the as-prepared composite was investigated in a small SRM testing system with an average pressure of 13.3 MPa and 5 wt% Al for 1.4 s. The results show that the linear ablation rate of the Al20Si/graphite throat decreased by 92% compared to that of the C/C composite throat. The increased anti-ablative properties are provided by Al20Si alloy fillers, which reduce the degree of thermochemical ablation of the graphite matrix through heat dissipation, oxygen dissipation, and thermal blockage. Furthermore, the Al4SiC4 generated from Al20Si alloy and graphite fills graphite pores, which contributes to the oxidation resistance of the composite.
1. Introduction Nozzles are one of the key components of solid rocket motor (SRM) as it maintains a certain pressure in the combustion chamber by controlling the flux of combustion gas plume [1,2]. The high temperature, high pressure and high-speed particle erosion conditions generated by the combustion of solid propellants will cause the size change of nozzles (especially the throat), which directly endangers the ballistic performance of rockets [3,4]. Recently, the graphite and C/C composite have found increasing applications in SRM nozzles because of their excellent thermal and physical properties, as well as low densities [4–6]. However, the high ablation rates have limited their further application in new SRM with high specific thrust and high chamber pressure. At present, the main way to improve the ablation resistance of graphite and carbon-carbon composite for nozzles is matrix modification. One effective method is adding ultra-high temperature ceramics [7]. Li et al. [8] prepared HfC-C/C composite throats with different HfC content by polymer impregnation and pyrolysis (PIP) and found that the overall ablation rate decreased with the increase of HfC content. Another method is to utilize the latent heat of melting and vaporization of metal additives to cool the matrix actively, thereby improving ablation resistance [9]. On this basis, we developed Al20Si/graphite composite by infiltrating Al20Si alloy into the graphite matrix.
Subsequent oxyacetylene flame ablation results indicated that the linear ablation rates of Al20Si/graphite composite decreased nearly by one order of magnitude compared to graphite, showing an exciting performance improvement [10]. However, the ablation environments, one of the most important factors, of SRM and oxyacetylene flame are significantly different in terms of gas composition, pressure, flow rate, etc. [11]. Therefore, in order to evaluate its practical performance, a study on the ablation performance and mechanism of Al20Si/graphite composite in the SRM ablation environment is urgent. In present work, the new developed Al20Si/graphite composites have been prepared by pressure infiltration method. After that, the ablation of nozzle-throats made of Al20Si/graphite composite and C/C composite (as a comparison) were performed in an SRM testing system. The ablation performance, morphology and microstructure of the Al20Si/graphite composite were investigated. Finally, ablation behavior and mechanism were further elucidated. 2. Experimental procedure 2.1. Material preparation The porous graphite KYD-40 with a density of 1.92 g/cm3 (supplied by Pingdingshan Kaiyuan Special Graphite Co., Ltd., China) and a
∗ Corresponding author. P. O. 3023, Science park, No. 2 Yikuang street, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150080, PR China. ∗∗ Corresponding author. P. O. 3023, Science park, No. 2 Yikuang street, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150080, PR China. E-mail addresses: [email protected] (P. Kang), [email protected] (G. Wu).
https://doi.org/10.1016/j.ceramint.2020.02.110 Received 6 December 2019; Received in revised form 16 January 2020; Accepted 12 February 2020 0272-8842/ © 2020 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Please cite this article as: Hao Liu, et al., Ceramics International, https://doi.org/10.1016/j.ceramint.2020.02.110
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before and after the ablation nozzle tomography, which was performed using a micro X-ray system [12]. The average linear ablation rate (Rl) was calculated according to Eq. (1): Rl = Δd / t
(1)
where Δd is the change of the throat radius before and after ablation; t is the ablation time. 2.3. Characterization Morphologies and chemical compositions of the prepared Al20Si/ graphite nozzle before and after ablation were investigated by scanning electron microscopy (SEM, Quanta 200FEG) equipped with energy dispersive spectroscopy (EDS). The phase analysis was conducted by Xray diffraction (XRD, X'Pert Pro MPD). The bulk density of the obtain composite and volume fraction of Al20Si alloy were measured and calculated by the Archimedes method and rule-of-mixture, respectively. 3. Results and discussion 3.1. Microstructure and composition of the Al20Si/graphite composite Fig. 3 shows the typical microstructure of the Al20Si/graphite composite. As can be seen, most of the pores in graphite preform (gray area) have been filled by Al20Si alloy (white area), except for a few closed pores. The density of the Al20Si/graphite composite and volume fraction of Al20Si alloy were 2.13 g/cm3 and 7.7%, respectively. The interconnected pores in the graphite could act as channels for the alloy inflow during infiltration and for alloy outflow during ablation heating. The XRD pattern of the Al20Si/graphite composite displayed in Fig. 4 shows the phases in the composite were graphite, Al, and Si and no detectable peak of reaction product phase (SiC and/or Al4C3) was found.
Fig. 1. Optical images and 3D reconstruction models of (a)(b) Al20Si/graphite nozzle and (c)(d) C/C nozzle.
named Al20Si alloy (supplied by Northeast Light Alloy Co., Ltd., China) have been used as raw materials to prepare Al20Si/graphite composites by pressure infiltration method in the present work. Before infiltration, the porous graphite preforms and Al20Si alloy were heated up to 500 °C and 850 °C in muffle furnaces, respectively. Then, liquid Al20Si alloy was forced into porous graphite preforms under a pressure of 12 MPa and maintained for 5 min. After that, the infiltrated graphite preforms were cooled to room temperature and the Al20Si/graphite composites were obtained. The Al20Si/graphite composites were machined into integrated nozzles with a throat diameter of 15.5 mm for testing, as showing in Fig. 1a and b. A commonly used 3D needled C/C composite was used as a comparative material in this study. T300 polyacrylonitrile-based carbon fibers were used to prepare preforms for C/C composites. The preforms were fabricated by repeatedly overlapping the layers of 0° weftless fabric, chopped fiber web, and 90° weftless fabric using needlepunching technique. Subsequently, the porous preforms were densified by methane gas through a thermal gradient chemical vapor infiltration process. C/C composites with a density of 1.81 g/cm3 were then obtained by graphitization in an argon atmosphere. A Φ50 × 50 C/C composite was inlaid in graphite as a throat inset material and then machined into a nozzle with a throat diameter of 15.5 mm, as showing in Fig. 1c and d. The axial orientation of nozzle was parallel to the Z direction of the preform, while the radial orientation was parallel to the XY plane of the preform.
3.2. Ablation properties Fig. 5 appears the curves of the chamber pressure versus time in the combustion chamber of the C/C and the Al20Si/graphite nozzles. It is clear that the chamber pressure remained almost constant during steady-state ablation. For C/C nozzle, the maximum chamber pressure, average chamber pressure, and duration were 13.5 MPa, 12.6 MPa, and 1.4 s, respectively. For Al20Si/graphite nozzle, pressure in the combustion chamber reached a maximum level of 13.3 MPa in 0.5 s, and then the pressure slightly decreased as the propellant burned. The average chamber pressure and duration of Al20Si/graphite nozzle were 12.4 MPa and 1.4 s, respectively. The difference in the initial pressure of the combustion chamber is mainly due to the deviation of throat diameter. Furthermore, the pressure curve versus time in the combustion chamber of the Al20Si/graphite nozzle had a larger increase in the first half and a lower decrease in the second half, compared with that of the C/C nozzle. The smaller decrease of the pressure in the combustion chamber of Al20Si/graphite nozzle in the second half indicates a smaller ablation. Besides, the increase of the chamber pressure in the early stages indicates that a decrease in the throat diameter of the Al20Si/graphite nozzle. This phenomenon may be caused by the following two reasons:
2.2. Ablation test A small SRM testing system with a combustion chamber diameter of 112 mm was employed to study the ablation of nozzles, as showing in Fig. 2. The composition of the hollow cylindrical composite propellant was a metalized ammonium perchlorate (AP)/hydroxyl-terminated polybutadiene (HTPB) composite propellant with 5 wt% Al. The nozzle was exposed to the combustion gases for 1–2 s and the theoretical temperature of the combustion gases from the composite propellant was about 3000–3200 °C. Furthermore, the chamber pressure was monitored using a pressure gauge during the hot firing test. The ablation rate was measured and calculated from the 3D reconstruction
(a) The metal components inside the Al20Si/graphite composite material precipitate on the throat surface. (b) The relatively low temperature due to the phase transition of the Al–Si alloy inside the Al20Si/graphite nozzle, resulting in the deposition of Al2O3 in the throat. The average linear ablation rates of the C/C and Al20Si/graphite throats in this work are presented in Fig. 6, which were 0.092 mm/s 2
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Fig. 2. Schematic and photographs of the small solid rocket testing system.
Fig. 3. SEM image of the Al20Si/graphite composite before ablation. Fig. 5. Pressure-time curve of the combustion chamber.
Fig. 6. Linear ablation rates of C/C and Al20Si/graphite composites in this work, as well as C/C [13,14] and C/C–ZrC [14]composites.
Fig. 4. XRD patterns of the Al20Si/graphite composite before ablation.
than the throat section. XRD patterns of the throat and divergent sections have been shown in Fig. 8. Only diffraction peaks of graphite and Al4SiC4 phases had been detected in the throat section, while the diffraction peaks of graphite, Si, Al, Al2O3, and Al4C3 were confirmed in the divergent section. The Al4C3 phases were formed due to the reaction between Al and graphite during ablation, and the Al4SiC4 was further obtained by the reaction among Al4C3, Si and graphite [10]. Combined with the photograph of the divergent section and the XRD pattern (Fig. 8), the main component of the white deposit was Al2O3. The amounts of alumina deposits are different because of the difference in the environments of the various nozzle sections. The deposit in the converging section was formed by the impingement of Al2O3 particles on the wall. Since the airflow erosion of the throat was severe, it is difficult for the deposit to adhere. As the temperature of the combustion gas rapidly decreased after passing through the throat [15,16], a large
and 0.007 mm/s, respectively, which revealed a remarkable increase in ablation resistance. For comparison, the average linear ablation rates of C/C [13,14] and C/C–ZrC [14] throats under SRM ablation with similar chamber pressure are also provided in Fig. 6. Despite differences in test conditions such as propellant composition and ablation time, the Al20Si/graphite composite demonstrates broad application prospects in small SRM nozzle-throat compared with the C/C composite in each ablation environment.
3.3. Ablation morphology Photographs of the inner surface of the C/C and Al20Si/graphite nozzles after the SRM test are shown in Fig. 7. The white deposits were distributed in the convergent and divergent sections of the nozzle rather 3
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Fig. 7. Photographs of the inner surface of C/C and Al20Si/graphite nozzles after test.
inside the nozzle in Fig. 10a. The micrograph of the area near the surface of the throat (the red point marked "A" in Fig. 10a) is shown in Fig. 10b, in which no filler was present in the pores of the graphite matrix below the throat surface (inside the green dashed box). After ablation, micron-sized pores also appeared in the pores of the graphite matrix that were once completely filled by the Al20Si alloy. It suggests that the alloy fillers had been partially evaporated, and the remainder reacted with graphite to form an interfacial product (Al4C3 and Al4SiC4) during ablation. It can be seen from Fig. 10c that the pores of the graphite matrix deep in the throat section (the brown point marked "B" in Fig. 10a) were still completely occupied, suggesting that the alloy here only underwent a melt phase transition without vaporization, and then solidified after the SRM test. 3.4. Ablation mechanisms Fig. 8. XRD patterns of the throat and divergent sections of Al20Si/graphite nozzle.
During the SRM test, the combustion gas temperature reaches over 3000 °C. The major species in combustion products in the free stream of the nozzle throat are H2, CO, HCl, H2O, Al2O3, N2 and CO2 [7,14]. Most of these species tend to oxidize graphite, where H2O and CO2 are considered to be the predominantly aggressive species in SRM nozzles [16]. As for Al20Si/graphite composite, the possible oxidation reactions are as follows:
number of molten particles in the combustion gas were deposited in the divergent section. It is worth noting that more Al2O3 deposited on the inner wall of the Al20Si/graphite nozzle than that of C/C nozzle. On the one hand, the Al20Si/graphite composite contains Al alloy, which could be oxidized to Al2O3. On the other hand, the endothermic phase transition of alloy reduced the wall temperature, which was beneficial to the deposition of Al2O3 in the SRM combustion gas. The surface micrographs and EDS patterns of the Al20Si/graphite nozzle throat have been shown in Fig. 9. It can be inspected from Fig. 9a that a lot of graphite particles and pores were distributed on the throat surface after ablation. In addition, the surface was evenly covered with some small white particles. Graphite is composed of graphite particles and pitch carbon, in which the pitch carbon is preferentially oxidized because of its low degree of graphitization, resulting in protrusion of the graphite particles and an increase in the size of pores. It can be noticed from Fig. 9b that the diameter of the white spherical particles was about 0.5–2 μm, and it was inferred to be Al2O3 according to the EDS spectrum (Fig. 9d). Due to its low content, it could not be detected by XRD (Fig. 8). The surface of the graphite particles was completely covered by granular substances of various sizes (Fig. 9c). The EDS spectrum of the graphite region (Area 2 in Fig. 9c) has been shown in Fig. 9e, which demonstrated that it contained C, O, Al, and Si elements. It can be inferred that the components are mainly graphite, Al4SiC4, and Al2O3 combining with the XRD patterns in Fig. 8. Among them, Al4SiC4 is a promising refractory material, which can be rapidly generated only when the temperature exceeds 1700 °C [17], thus it was only detected in the throat section by XRD. The melting points of Al4SiC4 and Al2O3 are 2037 °C and 2054 °C, respectively, thus they can adhere to the surface of the graphite matrix as a liquid ceramic layer to improve the anti-oxidation and mechanical erosion resistance. Fig. 10 presents the cross-sectional photograph and micrographs of the Al20Si/graphite nozzle throat. No visible cracks could be seen
C (s) + H2O (g) → CO (g) + H2 (g)
(2)
2/3 Al (l) + H2O (g) → 2/3 Al2O3 (l) + H2 (g)
(3)
Si (l) + H2O (g) → SiO (g) + H2 (g)
(4)
1/2 Si (l) + H2O (g) → 1/2 SiO2 (l) + H2 (g)
(5)
C (s) + CO2 (g) → CO (g)
(6)
2/3 Al (l) + CO2 (g) → 1/3 Al2O3 (l) + CO (g)
(7)
Si (l) + CO2 (g) → SiO (g) + CO (g)
(8)
1/2 Si (l) + CO2 (g) → 1/2 SiO2 (l) + CO (g)
(9)
Gibbs free energy changes (ΔG) of the above reaction are showing in Fig. 11, which relates that these oxidation reactions could occur when the temperature range of 800–3200 °C. When the propellant burned in the combustion chamber, a boundary layer was formed between the hot combustion gas stream and the throat surface. Oxidizing components (H2O, CO2, etc.) in the combustion gas diffuse through the boundary layer to the surface of the throat and react with the carbon matrix to form gaseous CO or H2 leaving the surface, resulting in thermochemical ablation [18]. Al and Si occur oxidation (Eq. (3), (5), (7) and (9)) to form Al2O3 and SiO2, which seal the diffusion path of oxidizing species into the composite and improve its oxidation resistance [19,20]. Furthermore, the Al20Si alloy inside the graphite matrix reacts with graphite to form Al4SiC4, which has excellent oxidation resistance and high chemical stability, thereby contributing to the oxidation resistance of the composite. However, when temperatures exceed about 1900 °C, Si 4
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Fig. 9. Surface micrographs and EDS results of the throat section of the Al20Si/graphite nozzle after ablation: (a)–(c) SEM images; (d) EDS patterns of spot 1 in (c) and (d) EDS patterns of area 2 in (c).
Fig. 10. The cross-sections (a) photograph and (b) (c) micrographs of the Al20Si/graphite throat.
Fig. 11. Temperature dependence of Gibbs free energy change (ΔG) in oxidation reactions between Al20Si/graphite and (a) H2O, (b) CO2 during ablation.
5
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Fig. 12. Schematic of the ablation process of Al20Si/graphite nozzle-throat.
Table 1 The melting point, boiling point and latent heat of Al and Si simple substance [22,23]. Elements
Melting point (oC)
Latent heat of fusion (kJ/mol)
Boiling point (oC)
Latent heat of vaporization (kJ/mol)
Al Si
660 1414
10.7 50.6
2447 2680
293.4 384.2
determined by the chemical reaction rate and the diffusion rate of oxidizing substances through the boundary layer [21], the thermal dissipation, oxygen dissipation, and thermal blockage provided by the Al20Si alloy fillers weaken the thermochemical ablation of the graphite matrix. These first results suggest that Al20Si/graphite composite with low density, low cost, short preparation period and excellent ablation resistance will have broad application prospects in small SRM nozzlethroat.
tends to be oxidized to gaseous specie SiO (Eq. (4) and (8)), resulting in a decrease of the protective efficiency. As the temperature increases, the Al2O3 and SiO2 evaporate rapidly, thus there was no significant diffraction peak in the XRD pattern of the throat section. Oxidation occurs preferentially at the interface with highly chemically active, causing the protrusion of graphite particles (Fig. 9b). The protruding graphite particles are further peeled off the surface by the airflow shearing force and alumina particle scouring, leading to mechanical ablation [9]. The schematic diagram of the ablation process of Al20Si/graphite composite throat is shown in Fig. 12. The throat was heated up rapidly by the convective and radiative heating of combustion gas. The melting point, boiling point, latent heat of fusion and latent heat of vaporization of simple substance Al and Si are shown in Table 1. When the temperature reaches the melting point, the Al20Si alloy begins to melt, which absorbs heat and inhibits the temperature rise of the throat. The expansion caused by melting phase transition forces the molten Al–Si alloy inside the nozzle to gush out. The liquid film formed by molten Al–Si alloy on the throat surface isolates the contact of the oxidizing gas with the graphite effectively (Fig. 12a). Once the surface temperature of throats exceeds the boiling points, part of molten Al–Si near the surface of the throat further absorbs heat and quickly evaporates. The gaseous Al and Si injected into the boundary layer oxidize to form a liquid ceramic layer, which increases thermal blockage and decreases the concentration of oxidizing gaseous species of the boundary layer (Fig. 12b). Since the oxidations of Al and Si consume partially oxidizing species, the graphite matrix is protected from oxidation. Additionally, the chemical reaction of gaseous Al–Si with H2O and CO2 in the boundary layer can further consume the oxidizing component. With the continuous input of heat and the consumption of Al–Si alloy, the solidliquid interface and vapor-liquid interface of the Al20Si alloy gradually move into the interior of the throat. Although the oxidation of Al and Si is exothermic, it occurs outside the surface of the throat and hence the heating effect on the throat is negligible. In summary, the anti-ablation mechanism of Al–Si alloy fillers mainly includes three aspects. Firstly, the melting and partial vaporization of the Al–Si alloy consumes heat, i.e. heat dissipation, thereby suppressing the temperature rise of the nozzle. Secondly, the oxidations of Al and Si consume oxidizing gaseous species (H2O, CO2, etc.), that is, oxygen dissipation, which reduces the concentration of oxidizing gaseous species near the graphite matrix. Finally, the liquid ceramic layer covering the surface of the throat insert composed of molten alloy and oxidation products (Al2O3 and SiO2) acts as a barrier to the diffusion of heat and oxidizing species into the graphite matrix. Heat dissipation and thermal blockage reduce the heat load of the nozzle, thereby reducing the chemical reaction rate. Since thermochemical ablation is
4. Conclusion In this study, the ablation of Al20Si/graphite composite and C/C nozzle-throats were investigated using a small SRM testing system. The ablation rate of Al20Si/graphite throat is lower than that of the C/C composite throat. Compared with the C/C nozzle, more alumina deposited on the surface of the Al20Si/graphite nozzle. Analysis suggests that the melting and partial evaporation of Al20Si alloy and its oxidation products dissipate heat, reducing the heat load of the throat. Furthermore, the liquid film formed by the molten alloy as well as the boundary layer containing the vaporized alloy hinder the transfer of heat and oxidizing components to the graphite matrix. In combination with the effect that the preferential oxidation of the Al20Si alloy could also reduce the consumption of the graphite matrix, the addition of the Al20Si alloy reduces the thermochemical corrosion of the graphite, thereby increasing the ablation resistance.
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements The authors acknowledge Dr. Yang Liu and Dr. Lin Sun, National Key Laboratory of Combustion, Internal Flow and Thermo-Structure Laboratory, Northwestern Polytechnical University, for their help in the solid rocket motor nozzle-throat ablation test of this study.
Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.ceramint.2020.02.110. 6
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References [1] J. Yin, H.B. Zhang, X. Xiong, J.L. Zuo, B.Y. Huang, Ablation performance of carbon/ carbon composite throat after a solid rocket motor ground ignition test, Appl. Compos. Mater. 19 (2011) 237–245, https://doi.org/10.1007/s10443-011-9192-0. [2] D. Sciti, L. Zoli, L. Silvestroni, A. Cecere, G.D. Di Martino, R. Savino, Design, fabrication and high velocity oxy-fuel torch tests of a Cf-ZrB2- fiber nozzle to evaluate its potential in rocket motors, Mater. Des. 109 (2016) 709–717, https://doi.org/10. 1016/j.matdes.2016.07.090. [3] Y. Liu, J.Q. Pei, J. Li, G.Q. He, Ablation characteristics of a 4D carbon/carbon composite under a high flux of combustion products with a high content of particulate alumina in a solid rocket motor, N. Carbon Mater. 32 (2017) 143–150, https://doi.org/10.1016/s1872-5805(17)60112-4. [4] D. Bianchi, F. Nasuti, M. Onofri, E. Martelli, Thermochemical erosion analysis for ghraphite/carbon-carbon rocket nozzles, J. Propul. Power 27 (2011) 197–205, https://doi.org/10.2514/1.47754. [5] L.N. Peng, G.Q. He, J. Li, L. Wang, F. Qin, Effect of combustion gas mass flow rate on carbon/carbon composite nozzle ablation in a solid rocket motor, Carbon 50 (2012) 1554–1562, https://doi.org/10.1016/j.carbon.2011.11.034. [6] B. Evans, K. Kuo, P. Ferrara, J. Moore, P. Kutzler, E. Boyd, Nozzle throat erosion characterization study using a solid-propellant rocket motor simulator, 43rd AIAA/ ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2007, https://doi.org/ 10.2514/6.2007-5776. [7] X.T. Shen, K.Z. Li, H.J. Li, T. Feng, L.L. Zhang, B. Wang, Thermochemical erosion of hafnium carbide modified carbon/carbon composite throat in a small solid rocket motor, J. Inorg. Mater. 26 (2011) 427–432, https://doi.org/10.3724/sp.j.1077. 2011.00427. [8] S.Q. Li, K.Z. Li, H.Y. Du, S.Y. Zhang, X.T. Shen, Effect of hafnium carbide content on the ablative performance of carbon/carbon composites as rocket throats, Carbon 51 (2013) 437–438, https://doi.org/10.1016/j.carbon.2012.08.042. [9] M. Ahangarkani, The effect of contamination and skeleton fracture mode on ablation uniformity in W Cu composite, Int. J. Refract. Metals Hard Mater. 72 (2018) 15–20, https://doi.org/10.1016/j.ijrmhm.2017.12.002. [10] B.Q. Li, P.C. Kang, H.S. Gou, Q. Zhang, G.H. Wu, Ablation mechanisms of interpenetrating Al20Si/graphite composites, Ceram. Int. 39 (2013) 4819–4824, https:// doi.org/10.1016/j.ceramint.2012.11.072. [11] Y. Liu, Q.G. Fu, B.B. Wang, Y.W. Guan, Y. Liu, Ablation behavior of C/C-SiC-ZrB2 composites in simulated solid rocket motor plumes, J. Alloys Compd. 727 (2017) 135–145, https://doi.org/10.1016/j.jallcom.2017.08.114. [12] W.H. Hui, F.T. Bao, X.G. Wei, Y. Liu, Analysis of ablative performance of C/C
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
7
composite throat containing defects based on X-ray 3D reconstruction in a solid rocket motor, Int. J. Turbo Jet Engines 32 (2015), https://doi.org/10.1515/tjj2015-0021. K.Z. Li, X.T. Shen, H.J. Li, S.Y. Zhang, T. Feng, L.L. Zhang, Ablation of the carbon/ carbon composite nozzle-throats in a small solid rocket motor, Carbon 49 (2011) 1208–1215, https://doi.org/10.1016/j.carbon.2010.11.037. X.T. Shen, L. Liu, W. Li, K.Z. Li, Ablation behaviour of C/C–ZrC composites in a solid rocket motor environment, Ceram. Int. 41 (2015) 11793–11803, https://doi.org/ 10.1016/j.ceramint.2015.05.147. W.H. Hui, F.T. Bao, X.G. Wei, Y. Liu, Ablation performance of a 4D-braided C/C composite in a parameter-variable channel of a Laval nozzle in a solid rocket motor, N. Carbon Mater. 32 (2017) 365–373, https://doi.org/10.1016/s1872-5805(17) 60128-8. P. Thakre, V. Yang, Chemical erosion of carbon-carbon/graphite nozzles in solidpropellant rocket motors, J. Propul. Power 24 (2008) 822–833, https://doi.org/10. 2514/1.34946. A.V. Gubarevich, T. Watanabe, T. Nishimura, K. Yoshida, Combustion synthesis of single‐phase Al4SiC4 powder with assistance of induction heating, J. Am. Ceram. Soc. (2019) 1–6, https://doi.org/10.1111/jace.16846 0. F. Qin, L.N. Peng, J. Li, G.Q. He, Numerical simulations of multiscale Ablation of carbon/carbon throat with morphology effects, AIAA J. 55 (2017) 3476–3485, https://doi.org/10.2514/1.j055534. Y.B. Chang, W. Sun, X. Xiong, Z.K. Chen, Y.L. Wang, Z.H. Hao, Y.L. Xu, A novel design of Al-Cr alloy surface sealing for ablation resistant C/C-ZrC-SiC composite, J. Eur. Ceram. Soc. 37 (2017) 859–864, https://doi.org/10.1016/j.jeurceramsoc. 2016.09.002. C. Huo, L. Guo, C. Wang, G. Kou, H. Song, Microstructure and ablation mechanism of SiC-ZrC-Al2O3 coating for SiC coated C/C composites under oxyacetylene torch test, J. Alloys Compd. 735 (2018) 914–927, https://doi.org/10.1016/j.jallcom. 2017.11.215. K.K. Kuo, S.T. Keswani, A comprehensive theoretical model for carbon-carbon composite nozzle recession, Combust. Sci. Technol. 42 (2007) 145–164, https://doi. org/10.1080/00102208508960374. C.N. Pereira, G.C. Vebber, An innovative model for correlating surface tension, solubility parameters, molar volume and ratio of the coordination numbers of liquid metals, based on Stefan's rule, Surf. Interfaces 13 (2018) 51–57, https://doi.org/10. 1016/j.surfin.2018.07.004. A. Datas, A. Ramos, A. Martí, C. del Cañizo, A. Luque, Ultra high temperature latent heat energy storage and thermophotovoltaic energy conversion, Energy 107 (2016) 542–549, https://doi.org/10.1016/j.energy.2016.04.048.
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Ablation behavior of Al20Si/graphite composite nozzle-throats in a solid rocket motor environment Hao Liu, Pengchao Kang∗, Wenshu Yang, Ningbo Zhang, Yue Sun, Gaohui Wu∗∗ School of Material Science and Engineering, Harbin Institute of Technology, Harbin, 150001, China
A R T I C LE I N FO
A B S T R A C T
Keywords: A. Pressure infiltration C. Ablation resistance D. Al20Si/Graphite composites E. Engine components
Small solid rocket motors (SRM) require low density, low ablation nozzle-throat materials. In the present study, Al20Si alloy was infiltrated into the porous graphite matrix to develop Al20Si/graphite composites by pressure infiltration method. The ablation behavior of the as-prepared composite was investigated in a small SRM testing system with an average pressure of 13.3 MPa and 5 wt% Al for 1.4 s. The results show that the linear ablation rate of the Al20Si/graphite throat decreased by 92% compared to that of the C/C composite throat. The increased anti-ablative properties are provided by Al20Si alloy fillers, which reduce the degree of thermochemical ablation of the graphite matrix through heat dissipation, oxygen dissipation, and thermal blockage. Furthermore, the Al4SiC4 generated from Al20Si alloy and graphite fills graphite pores, which contributes to the oxidation resistance of the composite.
1. Introduction Nozzles are one of the key components of solid rocket motor (SRM) as it maintains a certain pressure in the combustion chamber by controlling the flux of combustion gas plume [1,2]. The high temperature, high pressure and high-speed particle erosion conditions generated by the combustion of solid propellants will cause the size change of nozzles (especially the throat), which directly endangers the ballistic performance of rockets [3,4]. Recently, the graphite and C/C composite have found increasing applications in SRM nozzles because of their excellent thermal and physical properties, as well as low densities [4–6]. However, the high ablation rates have limited their further application in new SRM with high specific thrust and high chamber pressure. At present, the main way to improve the ablation resistance of graphite and carbon-carbon composite for nozzles is matrix modification. One effective method is adding ultra-high temperature ceramics [7]. Li et al. [8] prepared HfC-C/C composite throats with different HfC content by polymer impregnation and pyrolysis (PIP) and found that the overall ablation rate decreased with the increase of HfC content. Another method is to utilize the latent heat of melting and vaporization of metal additives to cool the matrix actively, thereby improving ablation resistance [9]. On this basis, we developed Al20Si/graphite composite by infiltrating Al20Si alloy into the graphite matrix.
Subsequent oxyacetylene flame ablation results indicated that the linear ablation rates of Al20Si/graphite composite decreased nearly by one order of magnitude compared to graphite, showing an exciting performance improvement [10]. However, the ablation environments, one of the most important factors, of SRM and oxyacetylene flame are significantly different in terms of gas composition, pressure, flow rate, etc. [11]. Therefore, in order to evaluate its practical performance, a study on the ablation performance and mechanism of Al20Si/graphite composite in the SRM ablation environment is urgent. In present work, the new developed Al20Si/graphite composites have been prepared by pressure infiltration method. After that, the ablation of nozzle-throats made of Al20Si/graphite composite and C/C composite (as a comparison) were performed in an SRM testing system. The ablation performance, morphology and microstructure of the Al20Si/graphite composite were investigated. Finally, ablation behavior and mechanism were further elucidated. 2. Experimental procedure 2.1. Material preparation The porous graphite KYD-40 with a density of 1.92 g/cm3 (supplied by Pingdingshan Kaiyuan Special Graphite Co., Ltd., China) and a
∗ Corresponding author. P. O. 3023, Science park, No. 2 Yikuang street, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150080, PR China. ∗∗ Corresponding author. P. O. 3023, Science park, No. 2 Yikuang street, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150080, PR China. E-mail addresses: [email protected] (P. Kang), [email protected] (G. Wu).
https://doi.org/10.1016/j.ceramint.2020.02.110 Received 6 December 2019; Received in revised form 16 January 2020; Accepted 12 February 2020 0272-8842/ © 2020 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Please cite this article as: Hao Liu, et al., Ceramics International, https://doi.org/10.1016/j.ceramint.2020.02.110
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before and after the ablation nozzle tomography, which was performed using a micro X-ray system [12]. The average linear ablation rate (Rl) was calculated according to Eq. (1): Rl = Δd / t
(1)
where Δd is the change of the throat radius before and after ablation; t is the ablation time. 2.3. Characterization Morphologies and chemical compositions of the prepared Al20Si/ graphite nozzle before and after ablation were investigated by scanning electron microscopy (SEM, Quanta 200FEG) equipped with energy dispersive spectroscopy (EDS). The phase analysis was conducted by Xray diffraction (XRD, X'Pert Pro MPD). The bulk density of the obtain composite and volume fraction of Al20Si alloy were measured and calculated by the Archimedes method and rule-of-mixture, respectively. 3. Results and discussion 3.1. Microstructure and composition of the Al20Si/graphite composite Fig. 3 shows the typical microstructure of the Al20Si/graphite composite. As can be seen, most of the pores in graphite preform (gray area) have been filled by Al20Si alloy (white area), except for a few closed pores. The density of the Al20Si/graphite composite and volume fraction of Al20Si alloy were 2.13 g/cm3 and 7.7%, respectively. The interconnected pores in the graphite could act as channels for the alloy inflow during infiltration and for alloy outflow during ablation heating. The XRD pattern of the Al20Si/graphite composite displayed in Fig. 4 shows the phases in the composite were graphite, Al, and Si and no detectable peak of reaction product phase (SiC and/or Al4C3) was found.
Fig. 1. Optical images and 3D reconstruction models of (a)(b) Al20Si/graphite nozzle and (c)(d) C/C nozzle.
named Al20Si alloy (supplied by Northeast Light Alloy Co., Ltd., China) have been used as raw materials to prepare Al20Si/graphite composites by pressure infiltration method in the present work. Before infiltration, the porous graphite preforms and Al20Si alloy were heated up to 500 °C and 850 °C in muffle furnaces, respectively. Then, liquid Al20Si alloy was forced into porous graphite preforms under a pressure of 12 MPa and maintained for 5 min. After that, the infiltrated graphite preforms were cooled to room temperature and the Al20Si/graphite composites were obtained. The Al20Si/graphite composites were machined into integrated nozzles with a throat diameter of 15.5 mm for testing, as showing in Fig. 1a and b. A commonly used 3D needled C/C composite was used as a comparative material in this study. T300 polyacrylonitrile-based carbon fibers were used to prepare preforms for C/C composites. The preforms were fabricated by repeatedly overlapping the layers of 0° weftless fabric, chopped fiber web, and 90° weftless fabric using needlepunching technique. Subsequently, the porous preforms were densified by methane gas through a thermal gradient chemical vapor infiltration process. C/C composites with a density of 1.81 g/cm3 were then obtained by graphitization in an argon atmosphere. A Φ50 × 50 C/C composite was inlaid in graphite as a throat inset material and then machined into a nozzle with a throat diameter of 15.5 mm, as showing in Fig. 1c and d. The axial orientation of nozzle was parallel to the Z direction of the preform, while the radial orientation was parallel to the XY plane of the preform.
3.2. Ablation properties Fig. 5 appears the curves of the chamber pressure versus time in the combustion chamber of the C/C and the Al20Si/graphite nozzles. It is clear that the chamber pressure remained almost constant during steady-state ablation. For C/C nozzle, the maximum chamber pressure, average chamber pressure, and duration were 13.5 MPa, 12.6 MPa, and 1.4 s, respectively. For Al20Si/graphite nozzle, pressure in the combustion chamber reached a maximum level of 13.3 MPa in 0.5 s, and then the pressure slightly decreased as the propellant burned. The average chamber pressure and duration of Al20Si/graphite nozzle were 12.4 MPa and 1.4 s, respectively. The difference in the initial pressure of the combustion chamber is mainly due to the deviation of throat diameter. Furthermore, the pressure curve versus time in the combustion chamber of the Al20Si/graphite nozzle had a larger increase in the first half and a lower decrease in the second half, compared with that of the C/C nozzle. The smaller decrease of the pressure in the combustion chamber of Al20Si/graphite nozzle in the second half indicates a smaller ablation. Besides, the increase of the chamber pressure in the early stages indicates that a decrease in the throat diameter of the Al20Si/graphite nozzle. This phenomenon may be caused by the following two reasons:
2.2. Ablation test A small SRM testing system with a combustion chamber diameter of 112 mm was employed to study the ablation of nozzles, as showing in Fig. 2. The composition of the hollow cylindrical composite propellant was a metalized ammonium perchlorate (AP)/hydroxyl-terminated polybutadiene (HTPB) composite propellant with 5 wt% Al. The nozzle was exposed to the combustion gases for 1–2 s and the theoretical temperature of the combustion gases from the composite propellant was about 3000–3200 °C. Furthermore, the chamber pressure was monitored using a pressure gauge during the hot firing test. The ablation rate was measured and calculated from the 3D reconstruction
(a) The metal components inside the Al20Si/graphite composite material precipitate on the throat surface. (b) The relatively low temperature due to the phase transition of the Al–Si alloy inside the Al20Si/graphite nozzle, resulting in the deposition of Al2O3 in the throat. The average linear ablation rates of the C/C and Al20Si/graphite throats in this work are presented in Fig. 6, which were 0.092 mm/s 2
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Fig. 2. Schematic and photographs of the small solid rocket testing system.
Fig. 3. SEM image of the Al20Si/graphite composite before ablation. Fig. 5. Pressure-time curve of the combustion chamber.
Fig. 6. Linear ablation rates of C/C and Al20Si/graphite composites in this work, as well as C/C [13,14] and C/C–ZrC [14]composites.
Fig. 4. XRD patterns of the Al20Si/graphite composite before ablation.
than the throat section. XRD patterns of the throat and divergent sections have been shown in Fig. 8. Only diffraction peaks of graphite and Al4SiC4 phases had been detected in the throat section, while the diffraction peaks of graphite, Si, Al, Al2O3, and Al4C3 were confirmed in the divergent section. The Al4C3 phases were formed due to the reaction between Al and graphite during ablation, and the Al4SiC4 was further obtained by the reaction among Al4C3, Si and graphite [10]. Combined with the photograph of the divergent section and the XRD pattern (Fig. 8), the main component of the white deposit was Al2O3. The amounts of alumina deposits are different because of the difference in the environments of the various nozzle sections. The deposit in the converging section was formed by the impingement of Al2O3 particles on the wall. Since the airflow erosion of the throat was severe, it is difficult for the deposit to adhere. As the temperature of the combustion gas rapidly decreased after passing through the throat [15,16], a large
and 0.007 mm/s, respectively, which revealed a remarkable increase in ablation resistance. For comparison, the average linear ablation rates of C/C [13,14] and C/C–ZrC [14] throats under SRM ablation with similar chamber pressure are also provided in Fig. 6. Despite differences in test conditions such as propellant composition and ablation time, the Al20Si/graphite composite demonstrates broad application prospects in small SRM nozzle-throat compared with the C/C composite in each ablation environment.
3.3. Ablation morphology Photographs of the inner surface of the C/C and Al20Si/graphite nozzles after the SRM test are shown in Fig. 7. The white deposits were distributed in the convergent and divergent sections of the nozzle rather 3
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Fig. 7. Photographs of the inner surface of C/C and Al20Si/graphite nozzles after test.
inside the nozzle in Fig. 10a. The micrograph of the area near the surface of the throat (the red point marked "A" in Fig. 10a) is shown in Fig. 10b, in which no filler was present in the pores of the graphite matrix below the throat surface (inside the green dashed box). After ablation, micron-sized pores also appeared in the pores of the graphite matrix that were once completely filled by the Al20Si alloy. It suggests that the alloy fillers had been partially evaporated, and the remainder reacted with graphite to form an interfacial product (Al4C3 and Al4SiC4) during ablation. It can be seen from Fig. 10c that the pores of the graphite matrix deep in the throat section (the brown point marked "B" in Fig. 10a) were still completely occupied, suggesting that the alloy here only underwent a melt phase transition without vaporization, and then solidified after the SRM test. 3.4. Ablation mechanisms Fig. 8. XRD patterns of the throat and divergent sections of Al20Si/graphite nozzle.
During the SRM test, the combustion gas temperature reaches over 3000 °C. The major species in combustion products in the free stream of the nozzle throat are H2, CO, HCl, H2O, Al2O3, N2 and CO2 [7,14]. Most of these species tend to oxidize graphite, where H2O and CO2 are considered to be the predominantly aggressive species in SRM nozzles [16]. As for Al20Si/graphite composite, the possible oxidation reactions are as follows:
number of molten particles in the combustion gas were deposited in the divergent section. It is worth noting that more Al2O3 deposited on the inner wall of the Al20Si/graphite nozzle than that of C/C nozzle. On the one hand, the Al20Si/graphite composite contains Al alloy, which could be oxidized to Al2O3. On the other hand, the endothermic phase transition of alloy reduced the wall temperature, which was beneficial to the deposition of Al2O3 in the SRM combustion gas. The surface micrographs and EDS patterns of the Al20Si/graphite nozzle throat have been shown in Fig. 9. It can be inspected from Fig. 9a that a lot of graphite particles and pores were distributed on the throat surface after ablation. In addition, the surface was evenly covered with some small white particles. Graphite is composed of graphite particles and pitch carbon, in which the pitch carbon is preferentially oxidized because of its low degree of graphitization, resulting in protrusion of the graphite particles and an increase in the size of pores. It can be noticed from Fig. 9b that the diameter of the white spherical particles was about 0.5–2 μm, and it was inferred to be Al2O3 according to the EDS spectrum (Fig. 9d). Due to its low content, it could not be detected by XRD (Fig. 8). The surface of the graphite particles was completely covered by granular substances of various sizes (Fig. 9c). The EDS spectrum of the graphite region (Area 2 in Fig. 9c) has been shown in Fig. 9e, which demonstrated that it contained C, O, Al, and Si elements. It can be inferred that the components are mainly graphite, Al4SiC4, and Al2O3 combining with the XRD patterns in Fig. 8. Among them, Al4SiC4 is a promising refractory material, which can be rapidly generated only when the temperature exceeds 1700 °C [17], thus it was only detected in the throat section by XRD. The melting points of Al4SiC4 and Al2O3 are 2037 °C and 2054 °C, respectively, thus they can adhere to the surface of the graphite matrix as a liquid ceramic layer to improve the anti-oxidation and mechanical erosion resistance. Fig. 10 presents the cross-sectional photograph and micrographs of the Al20Si/graphite nozzle throat. No visible cracks could be seen
C (s) + H2O (g) → CO (g) + H2 (g)
(2)
2/3 Al (l) + H2O (g) → 2/3 Al2O3 (l) + H2 (g)
(3)
Si (l) + H2O (g) → SiO (g) + H2 (g)
(4)
1/2 Si (l) + H2O (g) → 1/2 SiO2 (l) + H2 (g)
(5)
C (s) + CO2 (g) → CO (g)
(6)
2/3 Al (l) + CO2 (g) → 1/3 Al2O3 (l) + CO (g)
(7)
Si (l) + CO2 (g) → SiO (g) + CO (g)
(8)
1/2 Si (l) + CO2 (g) → 1/2 SiO2 (l) + CO (g)
(9)
Gibbs free energy changes (ΔG) of the above reaction are showing in Fig. 11, which relates that these oxidation reactions could occur when the temperature range of 800–3200 °C. When the propellant burned in the combustion chamber, a boundary layer was formed between the hot combustion gas stream and the throat surface. Oxidizing components (H2O, CO2, etc.) in the combustion gas diffuse through the boundary layer to the surface of the throat and react with the carbon matrix to form gaseous CO or H2 leaving the surface, resulting in thermochemical ablation [18]. Al and Si occur oxidation (Eq. (3), (5), (7) and (9)) to form Al2O3 and SiO2, which seal the diffusion path of oxidizing species into the composite and improve its oxidation resistance [19,20]. Furthermore, the Al20Si alloy inside the graphite matrix reacts with graphite to form Al4SiC4, which has excellent oxidation resistance and high chemical stability, thereby contributing to the oxidation resistance of the composite. However, when temperatures exceed about 1900 °C, Si 4
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Fig. 9. Surface micrographs and EDS results of the throat section of the Al20Si/graphite nozzle after ablation: (a)–(c) SEM images; (d) EDS patterns of spot 1 in (c) and (d) EDS patterns of area 2 in (c).
Fig. 10. The cross-sections (a) photograph and (b) (c) micrographs of the Al20Si/graphite throat.
Fig. 11. Temperature dependence of Gibbs free energy change (ΔG) in oxidation reactions between Al20Si/graphite and (a) H2O, (b) CO2 during ablation.
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Fig. 12. Schematic of the ablation process of Al20Si/graphite nozzle-throat.
Table 1 The melting point, boiling point and latent heat of Al and Si simple substance [22,23]. Elements
Melting point (oC)
Latent heat of fusion (kJ/mol)
Boiling point (oC)
Latent heat of vaporization (kJ/mol)
Al Si
660 1414
10.7 50.6
2447 2680
293.4 384.2
determined by the chemical reaction rate and the diffusion rate of oxidizing substances through the boundary layer [21], the thermal dissipation, oxygen dissipation, and thermal blockage provided by the Al20Si alloy fillers weaken the thermochemical ablation of the graphite matrix. These first results suggest that Al20Si/graphite composite with low density, low cost, short preparation period and excellent ablation resistance will have broad application prospects in small SRM nozzlethroat.
tends to be oxidized to gaseous specie SiO (Eq. (4) and (8)), resulting in a decrease of the protective efficiency. As the temperature increases, the Al2O3 and SiO2 evaporate rapidly, thus there was no significant diffraction peak in the XRD pattern of the throat section. Oxidation occurs preferentially at the interface with highly chemically active, causing the protrusion of graphite particles (Fig. 9b). The protruding graphite particles are further peeled off the surface by the airflow shearing force and alumina particle scouring, leading to mechanical ablation [9]. The schematic diagram of the ablation process of Al20Si/graphite composite throat is shown in Fig. 12. The throat was heated up rapidly by the convective and radiative heating of combustion gas. The melting point, boiling point, latent heat of fusion and latent heat of vaporization of simple substance Al and Si are shown in Table 1. When the temperature reaches the melting point, the Al20Si alloy begins to melt, which absorbs heat and inhibits the temperature rise of the throat. The expansion caused by melting phase transition forces the molten Al–Si alloy inside the nozzle to gush out. The liquid film formed by molten Al–Si alloy on the throat surface isolates the contact of the oxidizing gas with the graphite effectively (Fig. 12a). Once the surface temperature of throats exceeds the boiling points, part of molten Al–Si near the surface of the throat further absorbs heat and quickly evaporates. The gaseous Al and Si injected into the boundary layer oxidize to form a liquid ceramic layer, which increases thermal blockage and decreases the concentration of oxidizing gaseous species of the boundary layer (Fig. 12b). Since the oxidations of Al and Si consume partially oxidizing species, the graphite matrix is protected from oxidation. Additionally, the chemical reaction of gaseous Al–Si with H2O and CO2 in the boundary layer can further consume the oxidizing component. With the continuous input of heat and the consumption of Al–Si alloy, the solidliquid interface and vapor-liquid interface of the Al20Si alloy gradually move into the interior of the throat. Although the oxidation of Al and Si is exothermic, it occurs outside the surface of the throat and hence the heating effect on the throat is negligible. In summary, the anti-ablation mechanism of Al–Si alloy fillers mainly includes three aspects. Firstly, the melting and partial vaporization of the Al–Si alloy consumes heat, i.e. heat dissipation, thereby suppressing the temperature rise of the nozzle. Secondly, the oxidations of Al and Si consume oxidizing gaseous species (H2O, CO2, etc.), that is, oxygen dissipation, which reduces the concentration of oxidizing gaseous species near the graphite matrix. Finally, the liquid ceramic layer covering the surface of the throat insert composed of molten alloy and oxidation products (Al2O3 and SiO2) acts as a barrier to the diffusion of heat and oxidizing species into the graphite matrix. Heat dissipation and thermal blockage reduce the heat load of the nozzle, thereby reducing the chemical reaction rate. Since thermochemical ablation is
4. Conclusion In this study, the ablation of Al20Si/graphite composite and C/C nozzle-throats were investigated using a small SRM testing system. The ablation rate of Al20Si/graphite throat is lower than that of the C/C composite throat. Compared with the C/C nozzle, more alumina deposited on the surface of the Al20Si/graphite nozzle. Analysis suggests that the melting and partial evaporation of Al20Si alloy and its oxidation products dissipate heat, reducing the heat load of the throat. Furthermore, the liquid film formed by the molten alloy as well as the boundary layer containing the vaporized alloy hinder the transfer of heat and oxidizing components to the graphite matrix. In combination with the effect that the preferential oxidation of the Al20Si alloy could also reduce the consumption of the graphite matrix, the addition of the Al20Si alloy reduces the thermochemical corrosion of the graphite, thereby increasing the ablation resistance.
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements The authors acknowledge Dr. Yang Liu and Dr. Lin Sun, National Key Laboratory of Combustion, Internal Flow and Thermo-Structure Laboratory, Northwestern Polytechnical University, for their help in the solid rocket motor nozzle-throat ablation test of this study.
Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.ceramint.2020.02.110. 6
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References [1] J. Yin, H.B. Zhang, X. Xiong, J.L. Zuo, B.Y. Huang, Ablation performance of carbon/ carbon composite throat after a solid rocket motor ground ignition test, Appl. Compos. Mater. 19 (2011) 237–245, https://doi.org/10.1007/s10443-011-9192-0. [2] D. Sciti, L. Zoli, L. Silvestroni, A. Cecere, G.D. Di Martino, R. Savino, Design, fabrication and high velocity oxy-fuel torch tests of a Cf-ZrB2- fiber nozzle to evaluate its potential in rocket motors, Mater. Des. 109 (2016) 709–717, https://doi.org/10. 1016/j.matdes.2016.07.090. [3] Y. Liu, J.Q. Pei, J. Li, G.Q. He, Ablation characteristics of a 4D carbon/carbon composite under a high flux of combustion products with a high content of particulate alumina in a solid rocket motor, N. Carbon Mater. 32 (2017) 143–150, https://doi.org/10.1016/s1872-5805(17)60112-4. [4] D. Bianchi, F. Nasuti, M. Onofri, E. Martelli, Thermochemical erosion analysis for ghraphite/carbon-carbon rocket nozzles, J. Propul. Power 27 (2011) 197–205, https://doi.org/10.2514/1.47754. [5] L.N. Peng, G.Q. He, J. Li, L. Wang, F. Qin, Effect of combustion gas mass flow rate on carbon/carbon composite nozzle ablation in a solid rocket motor, Carbon 50 (2012) 1554–1562, https://doi.org/10.1016/j.carbon.2011.11.034. [6] B. Evans, K. Kuo, P. Ferrara, J. Moore, P. Kutzler, E. Boyd, Nozzle throat erosion characterization study using a solid-propellant rocket motor simulator, 43rd AIAA/ ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2007, https://doi.org/ 10.2514/6.2007-5776. [7] X.T. Shen, K.Z. Li, H.J. Li, T. Feng, L.L. Zhang, B. Wang, Thermochemical erosion of hafnium carbide modified carbon/carbon composite throat in a small solid rocket motor, J. Inorg. Mater. 26 (2011) 427–432, https://doi.org/10.3724/sp.j.1077. 2011.00427. [8] S.Q. Li, K.Z. Li, H.Y. Du, S.Y. Zhang, X.T. Shen, Effect of hafnium carbide content on the ablative performance of carbon/carbon composites as rocket throats, Carbon 51 (2013) 437–438, https://doi.org/10.1016/j.carbon.2012.08.042. [9] M. Ahangarkani, The effect of contamination and skeleton fracture mode on ablation uniformity in W Cu composite, Int. J. Refract. Metals Hard Mater. 72 (2018) 15–20, https://doi.org/10.1016/j.ijrmhm.2017.12.002. [10] B.Q. Li, P.C. Kang, H.S. Gou, Q. Zhang, G.H. Wu, Ablation mechanisms of interpenetrating Al20Si/graphite composites, Ceram. Int. 39 (2013) 4819–4824, https:// doi.org/10.1016/j.ceramint.2012.11.072. [11] Y. Liu, Q.G. Fu, B.B. Wang, Y.W. Guan, Y. Liu, Ablation behavior of C/C-SiC-ZrB2 composites in simulated solid rocket motor plumes, J. Alloys Compd. 727 (2017) 135–145, https://doi.org/10.1016/j.jallcom.2017.08.114. [12] W.H. Hui, F.T. Bao, X.G. Wei, Y. Liu, Analysis of ablative performance of C/C
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
7
composite throat containing defects based on X-ray 3D reconstruction in a solid rocket motor, Int. J. Turbo Jet Engines 32 (2015), https://doi.org/10.1515/tjj2015-0021. K.Z. Li, X.T. Shen, H.J. Li, S.Y. Zhang, T. Feng, L.L. Zhang, Ablation of the carbon/ carbon composite nozzle-throats in a small solid rocket motor, Carbon 49 (2011) 1208–1215, https://doi.org/10.1016/j.carbon.2010.11.037. X.T. Shen, L. Liu, W. Li, K.Z. Li, Ablation behaviour of C/C–ZrC composites in a solid rocket motor environment, Ceram. Int. 41 (2015) 11793–11803, https://doi.org/ 10.1016/j.ceramint.2015.05.147. W.H. Hui, F.T. Bao, X.G. Wei, Y. Liu, Ablation performance of a 4D-braided C/C composite in a parameter-variable channel of a Laval nozzle in a solid rocket motor, N. Carbon Mater. 32 (2017) 365–373, https://doi.org/10.1016/s1872-5805(17) 60128-8. P. Thakre, V. Yang, Chemical erosion of carbon-carbon/graphite nozzles in solidpropellant rocket motors, J. Propul. Power 24 (2008) 822–833, https://doi.org/10. 2514/1.34946. A.V. Gubarevich, T. Watanabe, T. Nishimura, K. Yoshida, Combustion synthesis of single‐phase Al4SiC4 powder with assistance of induction heating, J. Am. Ceram. Soc. (2019) 1–6, https://doi.org/10.1111/jace.16846 0. F. Qin, L.N. Peng, J. Li, G.Q. He, Numerical simulations of multiscale Ablation of carbon/carbon throat with morphology effects, AIAA J. 55 (2017) 3476–3485, https://doi.org/10.2514/1.j055534. Y.B. Chang, W. Sun, X. Xiong, Z.K. Chen, Y.L. Wang, Z.H. Hao, Y.L. Xu, A novel design of Al-Cr alloy surface sealing for ablation resistant C/C-ZrC-SiC composite, J. Eur. Ceram. Soc. 37 (2017) 859–864, https://doi.org/10.1016/j.jeurceramsoc. 2016.09.002. C. Huo, L. Guo, C. Wang, G. Kou, H. Song, Microstructure and ablation mechanism of SiC-ZrC-Al2O3 coating for SiC coated C/C composites under oxyacetylene torch test, J. Alloys Compd. 735 (2018) 914–927, https://doi.org/10.1016/j.jallcom. 2017.11.215. K.K. Kuo, S.T. Keswani, A comprehensive theoretical model for carbon-carbon composite nozzle recession, Combust. Sci. Technol. 42 (2007) 145–164, https://doi. org/10.1080/00102208508960374. C.N. Pereira, G.C. Vebber, An innovative model for correlating surface tension, solubility parameters, molar volume and ratio of the coordination numbers of liquid metals, based on Stefan's rule, Surf. Interfaces 13 (2018) 51–57, https://doi.org/10. 1016/j.surfin.2018.07.004. A. Datas, A. Ramos, A. Martí, C. del Cañizo, A. Luque, Ultra high temperature latent heat energy storage and thermophotovoltaic energy conversion, Energy 107 (2016) 542–549, https://doi.org/10.1016/j.energy.2016.04.048.