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C–Nb brazing joint
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β-LiAlSiO4 negative thermal expansion network interlayer for C/C–Nb brazing joint Jin Baa,1, Bin Wanga,1, Xu Jia, Hang Lia, Jinghuang Lina, Xiaohang Zhenga, Jian Caoa, Jicai Fenga, Zhengxiang Zhongb, Junlei Qia,∗ a
State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, China MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, China
b
A R T I C LE I N FO
A B S T R A C T
Keywords: β-LiAlSiO4 Network Negative thermal expansion Braze
A negative expansion LiAlSiO4 (LAS) network has been developed for C/C–Nb joints to modify the residual stress. LAS network was sintered elaborately obtaining high strut strength and smooth surface. AgCuTi brazing alloy had good wettability on LAS and infiltrated into network with faultless interfacial joining. The effect of stiff network structure on the stress dispersion of composite joints was investigated innovatively. The shear strength of joints modified with LAS network raised to 45.5 MPa, which was 2.6 times superior to the joints without this interlayer.
1. Introduction The joining of composites to alloy was the important manufacturing process to realize light-weight design [1]. Among numerous dissimilar materials joints, C/C–Nb brazing joint has been widely reported to apply in the load-supporting and heat-proof structure. Unfortunately, joining quality was undermined with high residual stress caused by huge properties difference of C/C and Nb, especially the coefficient of thermal expansion (CTE) [2]. Current methods focused on regulating properties of brazing seam to reduce the residual stress. One traditional way is adding low CTE reinforcing particles to reduce the CTE of brazing seam [3], but this method was always trouble with low addition and poor dispersion. The other is introducing the foil interlayer to modify stress via its low CTE (ceramic interlayer) or outstanding ductility (flexible alloy interlayer) [4]. Nonetheless, foil interlayer was still faced with the abrupt change of brazing seam properties caused by unevenly dispersion. Network interlayer combined the structure advantages of particles and foil interlayer, satisfying the uniform dispersion of reinforcements due to its 3D skeleton structure [2,5]. Compared with particles, network interlayer could increase the addition through regulating the porosity of interlayer without generating the voids and agglomeration. Several alloy networks have been reported in the stress modification of composites-alloy joints. However, high intrinsic CTE and easy collapse
limited the buffer capacity of reducing the residual stress. It is noted that network can change the interface from 2D plain to 3D structure, which spreads the application of ceramic interlayer. But the fabrication of ceramic network was difficult, only few kinds have been developed. β-LiAlSiO4 (LAS) possesses the negative thermal expansion, which is the optical reinforcements to reduce the residual stress [6]. To overcome the problems above, LAS network was fabricated successfully as interlayer to improve the joining quality of C/C–Nb joints. 2. Experiment LAS network was product through “polymeric sponge” process shown in Fig. 1a [7]. Commercial polyurethane (PU) sponges with 50 pores per inch (PPI) were adopted in this study. Step I was to soak PU sponges into 0.2 M NaOH solution at 60 °C for 0.5 h to eliminate oddment and keep high open cell rate. Step II was to immerse PU into slurry and swing to remove the superfluous slurry. Then repeat several circulations to cover the slurry homogenously. Step III was to heat slurry sponges to 700 °C for 0.5 h in muffle furnace to burn out PU, and then increase temperature to 1300 °C for 3 h to sinter the LAS network. The dimension of C/C and Nb was 5 mm × 5 mm × 5 mm and 10 mm × 10 mm × 4 mm, respectively. Ag26.7Cu4.5Ti (wt%) was adopted. Brazing assembly was shown in Fig. 1b. The brazing parameter was set as 880 °C for 10 min. Microstructure and component were
∗
Corresponding author. E-mail address: [email protected] (J. Qi). 1 These authors contributed equally. https://doi.org/10.1016/j.ceramint.2020.01.283 Received 24 December 2019; Received in revised form 30 January 2020; Accepted 30 January 2020 0272-8842/ © 2020 Published by Elsevier Ltd.
Please cite this article as: Jin Ba, et al., Ceramics International, https://doi.org/10.1016/j.ceramint.2020.01.283
Ceramics International xxx (xxxx) xxx–xxx
J. Ba, et al.
Fig. 1. Schematic diagram of (a)LAS network sintering and (b)the brazing assembly.
Fig. 2. Morphology and surface of LAS network sintered at (a)1100 °C, (b)1200 °C and (c)1300 °C; (d) The effect of sintering temperature on network strength; (e) Morphology and (f)strength of LAS network with various porosity; (g)XRD patterns and (h)contact angle on sintered LAS.
sponge as shown in Fig. 2e. In Fig. 2f, compression strength was improved slightly with porosity increasing. The strut strength almost reached about 200 MPa with various porosity. It means that sintering parameter directly effects the strut strength. XRD pattern in Fig. 2g exhibited that the sintered LAS still maintains β structure, possessing the property of negative expansion [6]. The wettability of AgCuTi on LAS block was investigated in Fig. 2h. The contact angle of 14.5° indicated that AgCuTi could fill up with the void of network substantially. The sintered LAS network can be applied into brazing seam as interlayer. To investigate the effect of LAS network on the microstructure of joints, the width with 200 μm of LAS network has been adopted. To maintain the high LAS content, the network with 50 and 60 PPI was introduced into brazing seam. In Fig. 3a the joints were brazed with pure AgCuTi, and C/C was joined via the reaction of C and Ti. Ag based solid solution and Cu–Ti compounds made up with the brazing seam. High deformation of Ag maintained the intact joint under high residual stress. When 50 PPI network was introduced in Fig. 3b, network dispersed uniformly in three dimension and AgCuTi infiltrated into network sufficiently. No voids and crack can be found. As 60 PPI network was adopted in Fig. 3c, LAS was sintered continuously like a flake. It was because of the blocking of LAS slurry in PU sponge, causing abrupt change of property without interweaving of brazing alloy and LAS. Porosity higher than 50 PPI was not suitable for network interlayer. It is clear that the CTE between AgCuTi and LAS is still high, leading to high stress among the interface. From the inset in Fig. 3b, the typical double reaction layer can be observed between LAS and AgCuTi. Interfacial
characterized by scanning electron microscopy (SEM, NanoLab 600i) and X-ray diffraction (XRD, JDX-3530 M). The average shear strength was obtained with 5 samples following ASTM D905-03 test procedure. 3. Results and discussion Fig. 2a–c shows the effect of sintering temperature on molding of network with holding time of 3 h. These networks were sintered with 50 PPI PU sponge, possessing micro-pore diameter of about 200 μm and the strut with about 50 μm diameter. LAS will melt completely above 1400 °C. As temperature was below 1300 °C, crack and fragmentation can be easily found. The strut surface became smoother with the increase of temperature, indicating the good bonding between particles. It is noticed that strut and brazing alloy sustained stress together. The strut strength is more significant than overall strength. Strut strength can be expressed via equation (1) [8]: σfc/σfs = C(ρ/ρs)3/2
(1)
where σfc is the compressive strength of network, σfs is the strut strength, C is the geometric constant (for open cell is 0.65) [8], ρ is the bulk density of LAS and ρs is the density of struts. Fig. 2d shows that strut strength increased with temperature raising in accordance with the surface condition of network. Under 1300 °C sintering, the strut strength can be estimated as 192.8 MPa, close to the fracture strength of LAS (about 220 MPa [9]). Its high strength satisfied the stress transfer and CTE mismatch in the brazing seam. Various porosity of network can be fabricated via relevant PU 2
Ceramics International xxx (xxxx) xxx–xxx
J. Ba, et al.
Fig. 3. Microstructure of C/C–Nb joints brazed with (a)AgCuTi, (b)AgCuTi+50PPI LAS and (c)AgCuTi+60PPI LAS; (d)XRD pattern of AgCuTi-LAS interface; (e) Shear strength of joints with various interlayer; (f)Model of network interlayer; Residual stress distribution of joints brazed with (g)AgCuTi and (h) AgCuTi+50PPI LAS.
of brazing.
structure was mainly composed of LAS/TiO2+TiSi/Cu3Ti3O/AgCuTi according to XRD pattern shown in Fig. 3d. Cu3Ti3O shows good plastic deformation with the twining behaviour [10], inducing the decrease of stress between LAS and AgCuTi. Moreover, network structure change the interface from plane into 3D structure comparing with foil interlayer. It can increase joining area, generate the interweaving between LAS and AgCuTi and modify the stress dispersion. All these contribute to the tough bonding of LAS and AgCuTi. That is the reason that no cracks can be found among the interface between AgCuTi and LAS. With the reinforcement of 50 PPI network, the joining strength reached 45.5 ± 3.4 MPa, which 2.6 times higher than that of the original joints (16.8 ± 2.1 MPa). Too continuity of 60 PPI network caused the decrease and instability of strength. Finite analysis was adopted to demonstrate the residual stress dispersion via ABAQUS. The structure of network model was simplified from practical size as shown in Fig. 3f. The joint brazed with AgCuTi shows that stress mostly concentrated among brazing alloy in Fig. 3g. Stress at C/C side also possessed high value, prompting the fracture of TiC reaction layer. When LAS network was introduced shown in Fig. 3h, the network undertook most stress. Stress among brazing alloy was modified slightly, and the dispersion of stress at C/C side was shrunk and reduced about 57.4 MPa. It is beneficial for the fragile TiC layer to support more loads. It is the main reason of shear strength improvement. LAS network exhibits the great advantage of modifying residual stress with the intact microstructure of joints.
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 support from the National Natural Science Foundation of China (Grant Nos 51575135, 51622503, U1537206 and 51621091) and Natural Science Foundation of Heilongjiang Province of China (YQ2019E023) is highly appreciated. References [1] S. Labruquère, X. Bourrat, R. Pailler, R. Naslain, Structure and oxidation of C/C composites: role of the interface, Carbon (N. Y.) 39 (2001) 971–984, https://doi.org/10. 1016/S0008-6223(00)00142-1. [2] Z. Wang, G. Wang, M. Li, J. Lin, Q. Ma, A. Zhang, Z. Zhong, J. Qi, J. Feng, Three-dimensional graphene-reinforced Cu foam interlayer for brazing C/C composites and Nb, Carbon (N. Y.) 118 (2017) 723–730, https://doi.org/10.1016/j.carbon.2017.03.099. [3] M. Yang, T. Lin, P. He, Microstructure evolution of Al2O3/Al2O3 joint brazed with Ag-CuTi+B+TiH2 composite filler, Ceram. Int. 38 (2012) 289–294, https://doi.org/10.1016/j. ceramint.2011.07.005. [4] T. Wang, T. Ivas, W. Lee, C. Leinenbach, J. Zhang, Relief of the residual stresses in Si3N4/ Invar joints by multi-layered braze structure – experiments and simulation, Ceram. Int. 42 (2016) 7080–7087, https://doi.org/10.1016/j.ceramint.2016.01.096. [5] W. Guo, H. Zhang, K. Ma, Y. Zhu, H. Zhang, B. Qi, F. Li, P. Peng, Reactive brazing of silicon nitride to Invar alloy using Ni foam and AgCuTi intermediate layers, Ceram. Int. 45 (2019) 13979–13987, https://doi.org/10.1016/j.ceramint.2019.04.097. [6] I.E. Reimanis, C. Seick, K. Fitzpatrick, E.R. Fuller, S. Landin, Spontaneous ejecta from βeucryptite composites, J. Am. Ceram. Soc. 90 (2007) 2497–2501, https://doi.org/10. 1111/j.1551-2916.2007.01744.x. [7] F.F. Lange, K.T. Miller, Open-cell, low-density ceramics fabricated from reticulated polymer substrates, Adv. Ceram. Mater. 2 (1987) 827–831, https://doi.org/10.1111/j. 1551-2916.1987.tb00156.x. [8] M.F. Ashby, Mechanical properties of cellular solids, Metall. Trans. A, Phys. Metall. Mater. Sci. 14 A (1983) 1755–1769, https://doi.org/10.1007/BF02645546. [9] T. Ogiwara, Y. Noda, K. Shoji, O. Kimura, Low-temperature sintering of high-strength βeucryptite ceramics with low thermal expansion using Li2O-GeO2 as a sintering additive, J. Am. Ceram. Soc. 94 (2011) 1427–1433, https://doi.org/10.1111/j.1551-2916.2010. 04279.x. [10] G.P. Kelkar, A.H. Carim, Synthesis, properties, and ternary phase stability of M6X compounds in the Ti─Cu─O system, J. Am. Ceram. Soc. 76 (1993) 1815–1820, https://doi. org/10.1111/j.1151-2916.1993.tb06652.x.
4. Conclusions LiAlSiO4 can be fabricated as network with open cell and same crystal structure. Its strut strength of 192.8 MPa was high enough to support the interfacial stress. The network will possess good open cell rate no more than 50 PPI in porosity of PU sponge. Wettability of AgCuTi alloy on LAS was 14.5°, satisfying the interweaving of AgCuTi and LAS. Due to the good deformation of Ag and Cu3Ti3O, the faultless interface between LAS and brazing alloy can be obtained, profited by the interweaving structure as well. Residual stress was transferred to network, and stress at C/C side was reduced by 57.4 MPa. The shear strength can reach 45.5 MPa with 50 PPI network. Network will be a perfect way to extend the application of ceramic interlayer in the field 3
Contents lists available at ScienceDirect
Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Short communication
β-LiAlSiO4 negative thermal expansion network interlayer for C/C–Nb brazing joint Jin Baa,1, Bin Wanga,1, Xu Jia, Hang Lia, Jinghuang Lina, Xiaohang Zhenga, Jian Caoa, Jicai Fenga, Zhengxiang Zhongb, Junlei Qia,∗ a
State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, China MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, State Key Laboratory of Urban Water Resource and Environment, School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, China
b
A R T I C LE I N FO
A B S T R A C T
Keywords: β-LiAlSiO4 Network Negative thermal expansion Braze
A negative expansion LiAlSiO4 (LAS) network has been developed for C/C–Nb joints to modify the residual stress. LAS network was sintered elaborately obtaining high strut strength and smooth surface. AgCuTi brazing alloy had good wettability on LAS and infiltrated into network with faultless interfacial joining. The effect of stiff network structure on the stress dispersion of composite joints was investigated innovatively. The shear strength of joints modified with LAS network raised to 45.5 MPa, which was 2.6 times superior to the joints without this interlayer.
1. Introduction The joining of composites to alloy was the important manufacturing process to realize light-weight design [1]. Among numerous dissimilar materials joints, C/C–Nb brazing joint has been widely reported to apply in the load-supporting and heat-proof structure. Unfortunately, joining quality was undermined with high residual stress caused by huge properties difference of C/C and Nb, especially the coefficient of thermal expansion (CTE) [2]. Current methods focused on regulating properties of brazing seam to reduce the residual stress. One traditional way is adding low CTE reinforcing particles to reduce the CTE of brazing seam [3], but this method was always trouble with low addition and poor dispersion. The other is introducing the foil interlayer to modify stress via its low CTE (ceramic interlayer) or outstanding ductility (flexible alloy interlayer) [4]. Nonetheless, foil interlayer was still faced with the abrupt change of brazing seam properties caused by unevenly dispersion. Network interlayer combined the structure advantages of particles and foil interlayer, satisfying the uniform dispersion of reinforcements due to its 3D skeleton structure [2,5]. Compared with particles, network interlayer could increase the addition through regulating the porosity of interlayer without generating the voids and agglomeration. Several alloy networks have been reported in the stress modification of composites-alloy joints. However, high intrinsic CTE and easy collapse
limited the buffer capacity of reducing the residual stress. It is noted that network can change the interface from 2D plain to 3D structure, which spreads the application of ceramic interlayer. But the fabrication of ceramic network was difficult, only few kinds have been developed. β-LiAlSiO4 (LAS) possesses the negative thermal expansion, which is the optical reinforcements to reduce the residual stress [6]. To overcome the problems above, LAS network was fabricated successfully as interlayer to improve the joining quality of C/C–Nb joints. 2. Experiment LAS network was product through “polymeric sponge” process shown in Fig. 1a [7]. Commercial polyurethane (PU) sponges with 50 pores per inch (PPI) were adopted in this study. Step I was to soak PU sponges into 0.2 M NaOH solution at 60 °C for 0.5 h to eliminate oddment and keep high open cell rate. Step II was to immerse PU into slurry and swing to remove the superfluous slurry. Then repeat several circulations to cover the slurry homogenously. Step III was to heat slurry sponges to 700 °C for 0.5 h in muffle furnace to burn out PU, and then increase temperature to 1300 °C for 3 h to sinter the LAS network. The dimension of C/C and Nb was 5 mm × 5 mm × 5 mm and 10 mm × 10 mm × 4 mm, respectively. Ag26.7Cu4.5Ti (wt%) was adopted. Brazing assembly was shown in Fig. 1b. The brazing parameter was set as 880 °C for 10 min. Microstructure and component were
∗
Corresponding author. E-mail address: [email protected] (J. Qi). 1 These authors contributed equally. https://doi.org/10.1016/j.ceramint.2020.01.283 Received 24 December 2019; Received in revised form 30 January 2020; Accepted 30 January 2020 0272-8842/ © 2020 Published by Elsevier Ltd.
Please cite this article as: Jin Ba, et al., Ceramics International, https://doi.org/10.1016/j.ceramint.2020.01.283
Ceramics International xxx (xxxx) xxx–xxx
J. Ba, et al.
Fig. 1. Schematic diagram of (a)LAS network sintering and (b)the brazing assembly.
Fig. 2. Morphology and surface of LAS network sintered at (a)1100 °C, (b)1200 °C and (c)1300 °C; (d) The effect of sintering temperature on network strength; (e) Morphology and (f)strength of LAS network with various porosity; (g)XRD patterns and (h)contact angle on sintered LAS.
sponge as shown in Fig. 2e. In Fig. 2f, compression strength was improved slightly with porosity increasing. The strut strength almost reached about 200 MPa with various porosity. It means that sintering parameter directly effects the strut strength. XRD pattern in Fig. 2g exhibited that the sintered LAS still maintains β structure, possessing the property of negative expansion [6]. The wettability of AgCuTi on LAS block was investigated in Fig. 2h. The contact angle of 14.5° indicated that AgCuTi could fill up with the void of network substantially. The sintered LAS network can be applied into brazing seam as interlayer. To investigate the effect of LAS network on the microstructure of joints, the width with 200 μm of LAS network has been adopted. To maintain the high LAS content, the network with 50 and 60 PPI was introduced into brazing seam. In Fig. 3a the joints were brazed with pure AgCuTi, and C/C was joined via the reaction of C and Ti. Ag based solid solution and Cu–Ti compounds made up with the brazing seam. High deformation of Ag maintained the intact joint under high residual stress. When 50 PPI network was introduced in Fig. 3b, network dispersed uniformly in three dimension and AgCuTi infiltrated into network sufficiently. No voids and crack can be found. As 60 PPI network was adopted in Fig. 3c, LAS was sintered continuously like a flake. It was because of the blocking of LAS slurry in PU sponge, causing abrupt change of property without interweaving of brazing alloy and LAS. Porosity higher than 50 PPI was not suitable for network interlayer. It is clear that the CTE between AgCuTi and LAS is still high, leading to high stress among the interface. From the inset in Fig. 3b, the typical double reaction layer can be observed between LAS and AgCuTi. Interfacial
characterized by scanning electron microscopy (SEM, NanoLab 600i) and X-ray diffraction (XRD, JDX-3530 M). The average shear strength was obtained with 5 samples following ASTM D905-03 test procedure. 3. Results and discussion Fig. 2a–c shows the effect of sintering temperature on molding of network with holding time of 3 h. These networks were sintered with 50 PPI PU sponge, possessing micro-pore diameter of about 200 μm and the strut with about 50 μm diameter. LAS will melt completely above 1400 °C. As temperature was below 1300 °C, crack and fragmentation can be easily found. The strut surface became smoother with the increase of temperature, indicating the good bonding between particles. It is noticed that strut and brazing alloy sustained stress together. The strut strength is more significant than overall strength. Strut strength can be expressed via equation (1) [8]: σfc/σfs = C(ρ/ρs)3/2
(1)
where σfc is the compressive strength of network, σfs is the strut strength, C is the geometric constant (for open cell is 0.65) [8], ρ is the bulk density of LAS and ρs is the density of struts. Fig. 2d shows that strut strength increased with temperature raising in accordance with the surface condition of network. Under 1300 °C sintering, the strut strength can be estimated as 192.8 MPa, close to the fracture strength of LAS (about 220 MPa [9]). Its high strength satisfied the stress transfer and CTE mismatch in the brazing seam. Various porosity of network can be fabricated via relevant PU 2
Ceramics International xxx (xxxx) xxx–xxx
J. Ba, et al.
Fig. 3. Microstructure of C/C–Nb joints brazed with (a)AgCuTi, (b)AgCuTi+50PPI LAS and (c)AgCuTi+60PPI LAS; (d)XRD pattern of AgCuTi-LAS interface; (e) Shear strength of joints with various interlayer; (f)Model of network interlayer; Residual stress distribution of joints brazed with (g)AgCuTi and (h) AgCuTi+50PPI LAS.
of brazing.
structure was mainly composed of LAS/TiO2+TiSi/Cu3Ti3O/AgCuTi according to XRD pattern shown in Fig. 3d. Cu3Ti3O shows good plastic deformation with the twining behaviour [10], inducing the decrease of stress between LAS and AgCuTi. Moreover, network structure change the interface from plane into 3D structure comparing with foil interlayer. It can increase joining area, generate the interweaving between LAS and AgCuTi and modify the stress dispersion. All these contribute to the tough bonding of LAS and AgCuTi. That is the reason that no cracks can be found among the interface between AgCuTi and LAS. With the reinforcement of 50 PPI network, the joining strength reached 45.5 ± 3.4 MPa, which 2.6 times higher than that of the original joints (16.8 ± 2.1 MPa). Too continuity of 60 PPI network caused the decrease and instability of strength. Finite analysis was adopted to demonstrate the residual stress dispersion via ABAQUS. The structure of network model was simplified from practical size as shown in Fig. 3f. The joint brazed with AgCuTi shows that stress mostly concentrated among brazing alloy in Fig. 3g. Stress at C/C side also possessed high value, prompting the fracture of TiC reaction layer. When LAS network was introduced shown in Fig. 3h, the network undertook most stress. Stress among brazing alloy was modified slightly, and the dispersion of stress at C/C side was shrunk and reduced about 57.4 MPa. It is beneficial for the fragile TiC layer to support more loads. It is the main reason of shear strength improvement. LAS network exhibits the great advantage of modifying residual stress with the intact microstructure of joints.
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 support from the National Natural Science Foundation of China (Grant Nos 51575135, 51622503, U1537206 and 51621091) and Natural Science Foundation of Heilongjiang Province of China (YQ2019E023) is highly appreciated. References [1] S. Labruquère, X. Bourrat, R. Pailler, R. Naslain, Structure and oxidation of C/C composites: role of the interface, Carbon (N. Y.) 39 (2001) 971–984, https://doi.org/10. 1016/S0008-6223(00)00142-1. [2] Z. Wang, G. Wang, M. Li, J. Lin, Q. Ma, A. Zhang, Z. Zhong, J. Qi, J. Feng, Three-dimensional graphene-reinforced Cu foam interlayer for brazing C/C composites and Nb, Carbon (N. Y.) 118 (2017) 723–730, https://doi.org/10.1016/j.carbon.2017.03.099. [3] M. Yang, T. Lin, P. He, Microstructure evolution of Al2O3/Al2O3 joint brazed with Ag-CuTi+B+TiH2 composite filler, Ceram. Int. 38 (2012) 289–294, https://doi.org/10.1016/j. ceramint.2011.07.005. [4] T. Wang, T. Ivas, W. Lee, C. Leinenbach, J. Zhang, Relief of the residual stresses in Si3N4/ Invar joints by multi-layered braze structure – experiments and simulation, Ceram. Int. 42 (2016) 7080–7087, https://doi.org/10.1016/j.ceramint.2016.01.096. [5] W. Guo, H. Zhang, K. Ma, Y. Zhu, H. Zhang, B. Qi, F. Li, P. Peng, Reactive brazing of silicon nitride to Invar alloy using Ni foam and AgCuTi intermediate layers, Ceram. Int. 45 (2019) 13979–13987, https://doi.org/10.1016/j.ceramint.2019.04.097. [6] I.E. Reimanis, C. Seick, K. Fitzpatrick, E.R. Fuller, S. Landin, Spontaneous ejecta from βeucryptite composites, J. Am. Ceram. Soc. 90 (2007) 2497–2501, https://doi.org/10. 1111/j.1551-2916.2007.01744.x. [7] F.F. Lange, K.T. Miller, Open-cell, low-density ceramics fabricated from reticulated polymer substrates, Adv. Ceram. Mater. 2 (1987) 827–831, https://doi.org/10.1111/j. 1551-2916.1987.tb00156.x. [8] M.F. Ashby, Mechanical properties of cellular solids, Metall. Trans. A, Phys. Metall. Mater. Sci. 14 A (1983) 1755–1769, https://doi.org/10.1007/BF02645546. [9] T. Ogiwara, Y. Noda, K. Shoji, O. Kimura, Low-temperature sintering of high-strength βeucryptite ceramics with low thermal expansion using Li2O-GeO2 as a sintering additive, J. Am. Ceram. Soc. 94 (2011) 1427–1433, https://doi.org/10.1111/j.1551-2916.2010. 04279.x. [10] G.P. Kelkar, A.H. Carim, Synthesis, properties, and ternary phase stability of M6X compounds in the Ti─Cu─O system, J. Am. Ceram. Soc. 76 (1993) 1815–1820, https://doi. org/10.1111/j.1151-2916.1993.tb06652.x.
4. Conclusions LiAlSiO4 can be fabricated as network with open cell and same crystal structure. Its strut strength of 192.8 MPa was high enough to support the interfacial stress. The network will possess good open cell rate no more than 50 PPI in porosity of PU sponge. Wettability of AgCuTi alloy on LAS was 14.5°, satisfying the interweaving of AgCuTi and LAS. Due to the good deformation of Ag and Cu3Ti3O, the faultless interface between LAS and brazing alloy can be obtained, profited by the interweaving structure as well. Residual stress was transferred to network, and stress at C/C side was reduced by 57.4 MPa. The shear strength can reach 45.5 MPa with 50 PPI network. Network will be a perfect way to extend the application of ceramic interlayer in the field 3