- Email: [email protected]
Preparation of ultralight glass foams via vacuum-assisted foaming
Materials Letters 166 (2016) 35–38
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation of ultralight glass foams via vacuum-assisted foaming Ya-Nan Qu, Zhen-Guo Su, Jie Xu, Wen-Long Huo, Kui-Cun Song, Ya-Li Wang, Jin-Long Yang n State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 3 August 2015 Received in revised form 18 October 2015 Accepted 5 December 2015 Available online 7 December 2015
We report a novel vacuum-assisted foaming technique for preparing ultralight glass foams using green spheres as raw material. The green spheres were sintered to form ultralight glass foams under vacuum pressure. The effect of sintering temperature and vacuum pressure on the preparation and properties of glass foams was investigated. The porosity and cell size increased with the decrease of vacuum pressure. Glass foams were fabricated at vacuum pressure of 30–70 kPa, with bulk density, porosity and compressive strength values of 0.081–0.122 g/cm3, 95.2–96.8% and 0.29–1.18 MPa, respectively. The ultralight glass foams have potential applications as thermal and acoustic insulation materials. & 2015 Published by Elsevier B.V.
Keywords: Porous materials Microstructure Mechanical strength Sintering Vacuum-assisted foaming
1. Introduction Glass foam is a heterophase system consisting of the solid and gaseous phase. As possessing properties including lightweight, thermally insulating, sound absorbing, compression-resistant and nonflammable, glass foam has been extensively applied in many fields such as lightweight ceramics, catalyst supports, structural materials, thermal and acoustic insulation materials [1–3]. Recently, preparation of glass foams using waste glass has raised a great practical interest due to the environmental pollution [4–7]. The most common method is to sinter waste glass powder admixed with suitable blowing agents. The blowing agents produce gaseous products during the sintering process, which may be caused by an oxidation effect of C-based blowing agents (carbon black, organic compounds, SiC, etc.) or by a decomposition process of minerals (MgCO3, CaCO3, etc.) [8–9]. In addition, glass foams can be synthesized from waste glasses using a facile green chemistry route that involves a low-temperature hydrothermal ion-exchange reaction [10]. While considerable progress has been made on the fabrication of glass foams from waste glass, glass foams with higher porosity and mechanical strength are highly desirable. Basically, a reduction of the pressure would increase the size of already existing pores keeping the surrounding parameters constant, according to the gas equation n
Corresponding author. E-mail address: [email protected] (J.-L. Yang).
http://dx.doi.org/10.1016/j.matlet.2015.12.027 0167-577X/& 2015 Published by Elsevier B.V.
PV = nRT
(1)
where P, V and n describe the gas pressure, volume and amount of gas, respectively. T is the temperature and R is the gas constant, which is 8.314 J/mol K. Based on this principle, the vacuum foaming technique has been used for the fabrication of magnesium foams [11]. And the vacuum-assisted foaming technique has been successfully used for foaming of ceramic suspensions [12–13]. Furthermore, high strength borosilicate foams have been fabricated by melting glass powder under high-pressure argon gas and subsequent heat treatment of the glass bulk at atmospheric pressure [14]. However, few attentions have been focused on preparation of glass foams using this superior method. Herein, we demonstrate a novel vacuum-assisted foaming process for the fabrication of ultralight glass foams using green spheres as raw materials. Vacuum condition enhances the growth of bubbles or cells during the foaming process. In this paper, the effects of sintering temperature, sintering procedure and vacuum pressure were investigated.
2. Experimental procedure Green spheres (Hebei YL-Bangda New Materials Limited Company, Handan, China), with size distribution of 30–200 μm, were used as raw material. The green spheres were prepared by the spray drying of particle-stabilized foam slurry composed of recycled soda-lime glass powder, dispersants (sodium hexametaphosphate), binders (polyvinyl alcohol), water and foaming agents
36
Y.-N. Qu et al. / Materials Letters 166 (2016) 35–38
Fig. 1. SEM images of (a) green spheres and (b) the glass foam sintered at 700 °C, the inset in (a) shows the inner microstructure of a single green sphere.
(propyl gallate) [15]. As shown in Fig. 1(a), the spheres are porous with many small holes between glass particles in the interior. The green spheres were stacked in porcelain crucibles coated with a thin layer of kaolin on the internal surface. The samples were heated up to the sintering temperature range between 660 °C and 720 °C at a rate of 3 °C/min and then held for 2 h. Different sintering procedure and vacuum pressure were used to prepare samples. The whole process of pumping air into vacuum state was finished in less than a minute. The microstructures of green spheres and samples were investigated using scanning electron microscope (Merlin VP Compact, Zeiss, Germany). Compressive strength was measured using a universal material testing machine (AG-IC 20 kN/50 kN, Shimadzu, Japan) at a loading rate of 1 mm/min. The carbon content measurements were performed using an elemental analyzer (EA3000, EuroVector, Italy). The mean cell diameter was determined by analyzing images using graphics software. The bulk density, ρb, was calculated with mass and volume of the test sample with regular shape. The total porosity, P, was determined with the following equation:
P = (1 −
ρb ρr
) × 100%
(2)
Where ρr (ρr ¼ 2.53 g/cm ) was the real density of glass powder. The volumetric water absorption, Wv, was calculated using Eq. (3): 3
Wv =
m1 − m0 × 100% ρw × V
(3)
where m0 and V were the mass and volume of the test sample. ρw was the density of water at room temperature. m1 was the mass of the test sample immersed in deionized water for 24 h at room temperature.
3. Results and discussion 3.1. Effect of sintering temperature The properties of samples are illustrated in Table 1. Samples were sintered at atmospheric pressure. Green spheres play an important role during the foaming process. Each green sphere forms a separate space for foaming and generates small and
Table 1 The properties of samples sintered at different temperatures. Sintering temperature (°C) Bulk density (g/cm3) Volumetric water absorption (%)
660 0.257 1.3
680 0.180 1.9
690 0.157 1.4
700 0.134 3.6
720 0.128 9.3
Table 2 The carbon contents of different samples. The sample
Carbon content (wt%)
Green spheres Green spheres heated up to 700 °C Sample sintered at 700 °C
1.34 0.48 0.33
uniform cells. Another unique advantage of using green spheres is that the spheres can prevent gaseous products from escaping. Table 2 shows the carbon contents of different samples. The carbon content decreases from 1.34 wt% to 0.48 wt% when the sample is heated up to 700 °C, which indicates the fact that the organic compounds used in the preparation process of green spheres transform into carbonaceous products on incomplete pyrolysis of the polymers during the heating procedure. And mixtures of CO2 and CO are commonly produced by the oxidation of carbonaceous products [8]. The carbon content decreases to 0.33 wt% after the foaming process at 700 °C. With the increase of sintering temperature, the gaseous products produced during the sintering process increase, contributing to the decrease of bulk density. The volumetric water absorption is less than 4.0% between 660 °C and 700 °C. However, the volumetric water absorption increases sharply at temperatures higher than 700 °C, which is attributed to the open-celled microstructure. The sample sintered at 700 °C shows good integrated performance, with a uniform microstructure as shown in Fig. 1(b).
3.2. Effect of sintering procedure The schematic diagram of sintering procedure is shown in Fig. 2 (a). The sintering temperature is 700 °C and the vacuum pressure is 50 kPa. Tn is the temperature at which air in the furnace is pumped into vacuum. Fig. 2(b) shows the effect of Tn value on microstructures and properties of glass foams. The bulk density decreases as Tn value increases, while the cell size is a positive function of Tn value. With the increase of Tn value, more gaseous products are enclosed in the cells before the vacuum condition, resulting in the increase of cell size and the decrease of bulk density. Another important reason for the increase of cell size is the coalescence of cells. The photographs in Fig. 2(b) demonstrate that the coalescence of cells ultimately leads to the uneven microstructure of the foams. The volumetric water absorption has great dependence on the open cells existing in the samples. The sample with the Tn value of 700 °C has higher volumetric water absorption, which is attributed to the open cells resulting from the coalescence of cells.
Y.-N. Qu et al. / Materials Letters 166 (2016) 35–38
37
Fig. 2. (a) The schematic diagram of sintering procedure and (b) the effect of Tn value on microstructure, bulk density and volumetric water absorption of glass foams.
Fig. 3. (a) The effect of vacuum pressure on bulk density and porosity; (b) evolutions of mean cell diameter and volumetric water absorption as functions of vacuum pressure, the inset shows the photograph of sample sintered at vacuum pressure of 30 kPa; (c) relationship between compressive strength and bulk density.
3.3. Effect of vacuum pressure Samples are prepared at different vacuum pressures with the sintering temperature and Tn value of 700 °C and 680 °C, respectively. The vacuum pressure has significant influences on preparation and properties of the foams. Fig. 3(a–b) shows the evolutions of properties of glass foams as functions of vacuum pressure. The bulk density decreases with the reduction of vacuum pressure. While the mean cell diameter increases as the vacuum pressure reduces. Samples prepared under vacuum condition have lower bulk density and greater cell size, which is attributed to the fact that vacuum condition accelerates the growth of cells. Fig. 3 (b) illustrates lower volumetric absorption of the samples except for the sample sintered at vacuum pressure of 30 kPa. The high volumetric water absorption is precisely due to the open-celled microstructure resulting from the coalescence of cells. Based on
the above analyses, the vacuum pressure must be controlled to be higher than 30 kPa to obtain closed-cell foams. 3.4. Mechanical strength Fig. 3(c) illustrates the relationship between compressive strength and bulk density, indicating that the compressive strength is roughly proportional to the bulk density. The compressive strength is higher than that reported in pertinent literatures [8,16,17], resulting from the uniform microstructure. The error bars of compressive strength tend to increase with the decrease of bulk density. The main reason given for this is that the microstructure gradually becomes non-uniform with the decrease of bulk density. In addition, the influence of sample preparation becomes evident as the bulk density decreases, resulting from both the non-uniform microstructure and large cell size.
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Y.-N. Qu et al. / Materials Letters 166 (2016) 35–38
4. Conclusions
References
Glass foams with high porosity and mechanical strength were prepared by a novel vacuum-assisted foaming technique. Both the sintering temperature and sintering procedure have significant effects on the preparation and properties of glass foams. With the reduction of vacuum pressure, the bulk density decreases, while the cell size increases. Glass foams were fabricated at vacuum pressure of 30–70 kPa, with bulk density, porosity and compressive strength values of 0.081–0.122 g/cm3, 95.2–96.8% and 0.29– 1.18 MPa, respectively. Both closed-cell and open-celled glass foams are successfully fabricated. Such glass foams with high porosity have potential applications as thermal insulation materials and sound absorption materials.
[1] C. Ohl, M. Kappa, V. Wilker, J. Am. Ceram. Soc. 94 (2011) 436–441. [2] R. Lebullenger, S. Chenu, J. Rocherullé, O. Merdrignac-Conanec, F. Cheviré, F. Tessier, et al., J. Non Cryst. Solids 356 (2010) 2562–2568. [3] V. Ducman, A. Mladenovič, J.S. Šuput, Cem. Concr. Res. 32 (2002) 223–226. [4] P. Colombo, G. Brusatin, E. Bernardo, G. Scarinci, Curr. Opin. Solid State Mater. Sci. 7 (2003) 225–239. [5] R. Taurino, I. Lancellotti, L. Barbieri, C. Leonelli, Int. J. Appl. Glass Sci. 5 (2014) 136–145. [6] R. Benzerga, V. Laur, R. Lebullenger, L.L. Gendre, S. Genty, A. Sharaiha, P. Queffelec, Mater. Res. Bull. 67 (2015) 261–265. [7] J. Bai, X. Yang, S. Xu, W. Jing, J. Yang, Mater. Lett. 136 (2014) 52–54. [8] G. Scarinci, G. Brusatin, E. Bernardo, in Cellular Ceramics: Structure, Manufacturing, Properties and Applications ed. by M. Scheffler, P. Colombo, WileyVCH, Weinheim. 2005, pp. 158-176. [9] J. König, R.R. Petersen, Y. Yue, J. Eur. Ceram. Soc. 34 (2014) 1591–1598. [10] C. Ji, D. He, L. Shen, X. Zhang, Y. Wang, A. Gupta, et al., Mater. Lett. 119 (2014) 60–63. [11] K. Renger, H. Kaufmann, Adv. Eng. Mater. 7 (2005) 117–123. [12] D. Yao, Y. Xia, K. Zuo, Y. Zeng, D. Jiang, J. Günster, J.G. Heinrich, Mater. Lett. 141 (2015) 138–140. [13] M.K. Ahn, Y.W. Moon, Y.H. Koh, H.E. Kim, J. Am. Ceram. Soc. 95 (2012) 3360–3362. [14] B. Wang, K. Matsumaru, J. Yang, Z. Fu, K. Ishizaki, Acta Mater. 60 (2012) 4185–4193. [15] J. Yang, K. Cai, X. Xi, G. Ge, Y. Huang, US Pat. 2014, p. 8845936. [16] Y. Attila, M. Güden, A. Taşdemirci, Ceram. Int. 39 (2013) 5869–5877. [17] E. Bernardo, F. Albertini, Ceram. Int. 32 (2006) 603–608.
Acknowledgments Our research work presented in this paper was supported by National Natural Science Foundation of China (51172120) and China Postdoctoral Science Foundation (2015M570094).
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Preparation of ultralight glass foams via vacuum-assisted foaming Ya-Nan Qu, Zhen-Guo Su, Jie Xu, Wen-Long Huo, Kui-Cun Song, Ya-Li Wang, Jin-Long Yang n State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, PR China
art ic l e i nf o
a b s t r a c t
Article history: Received 3 August 2015 Received in revised form 18 October 2015 Accepted 5 December 2015 Available online 7 December 2015
We report a novel vacuum-assisted foaming technique for preparing ultralight glass foams using green spheres as raw material. The green spheres were sintered to form ultralight glass foams under vacuum pressure. The effect of sintering temperature and vacuum pressure on the preparation and properties of glass foams was investigated. The porosity and cell size increased with the decrease of vacuum pressure. Glass foams were fabricated at vacuum pressure of 30–70 kPa, with bulk density, porosity and compressive strength values of 0.081–0.122 g/cm3, 95.2–96.8% and 0.29–1.18 MPa, respectively. The ultralight glass foams have potential applications as thermal and acoustic insulation materials. & 2015 Published by Elsevier B.V.
Keywords: Porous materials Microstructure Mechanical strength Sintering Vacuum-assisted foaming
1. Introduction Glass foam is a heterophase system consisting of the solid and gaseous phase. As possessing properties including lightweight, thermally insulating, sound absorbing, compression-resistant and nonflammable, glass foam has been extensively applied in many fields such as lightweight ceramics, catalyst supports, structural materials, thermal and acoustic insulation materials [1–3]. Recently, preparation of glass foams using waste glass has raised a great practical interest due to the environmental pollution [4–7]. The most common method is to sinter waste glass powder admixed with suitable blowing agents. The blowing agents produce gaseous products during the sintering process, which may be caused by an oxidation effect of C-based blowing agents (carbon black, organic compounds, SiC, etc.) or by a decomposition process of minerals (MgCO3, CaCO3, etc.) [8–9]. In addition, glass foams can be synthesized from waste glasses using a facile green chemistry route that involves a low-temperature hydrothermal ion-exchange reaction [10]. While considerable progress has been made on the fabrication of glass foams from waste glass, glass foams with higher porosity and mechanical strength are highly desirable. Basically, a reduction of the pressure would increase the size of already existing pores keeping the surrounding parameters constant, according to the gas equation n
Corresponding author. E-mail address: [email protected] (J.-L. Yang).
http://dx.doi.org/10.1016/j.matlet.2015.12.027 0167-577X/& 2015 Published by Elsevier B.V.
PV = nRT
(1)
where P, V and n describe the gas pressure, volume and amount of gas, respectively. T is the temperature and R is the gas constant, which is 8.314 J/mol K. Based on this principle, the vacuum foaming technique has been used for the fabrication of magnesium foams [11]. And the vacuum-assisted foaming technique has been successfully used for foaming of ceramic suspensions [12–13]. Furthermore, high strength borosilicate foams have been fabricated by melting glass powder under high-pressure argon gas and subsequent heat treatment of the glass bulk at atmospheric pressure [14]. However, few attentions have been focused on preparation of glass foams using this superior method. Herein, we demonstrate a novel vacuum-assisted foaming process for the fabrication of ultralight glass foams using green spheres as raw materials. Vacuum condition enhances the growth of bubbles or cells during the foaming process. In this paper, the effects of sintering temperature, sintering procedure and vacuum pressure were investigated.
2. Experimental procedure Green spheres (Hebei YL-Bangda New Materials Limited Company, Handan, China), with size distribution of 30–200 μm, were used as raw material. The green spheres were prepared by the spray drying of particle-stabilized foam slurry composed of recycled soda-lime glass powder, dispersants (sodium hexametaphosphate), binders (polyvinyl alcohol), water and foaming agents
36
Y.-N. Qu et al. / Materials Letters 166 (2016) 35–38
Fig. 1. SEM images of (a) green spheres and (b) the glass foam sintered at 700 °C, the inset in (a) shows the inner microstructure of a single green sphere.
(propyl gallate) [15]. As shown in Fig. 1(a), the spheres are porous with many small holes between glass particles in the interior. The green spheres were stacked in porcelain crucibles coated with a thin layer of kaolin on the internal surface. The samples were heated up to the sintering temperature range between 660 °C and 720 °C at a rate of 3 °C/min and then held for 2 h. Different sintering procedure and vacuum pressure were used to prepare samples. The whole process of pumping air into vacuum state was finished in less than a minute. The microstructures of green spheres and samples were investigated using scanning electron microscope (Merlin VP Compact, Zeiss, Germany). Compressive strength was measured using a universal material testing machine (AG-IC 20 kN/50 kN, Shimadzu, Japan) at a loading rate of 1 mm/min. The carbon content measurements were performed using an elemental analyzer (EA3000, EuroVector, Italy). The mean cell diameter was determined by analyzing images using graphics software. The bulk density, ρb, was calculated with mass and volume of the test sample with regular shape. The total porosity, P, was determined with the following equation:
P = (1 −
ρb ρr
) × 100%
(2)
Where ρr (ρr ¼ 2.53 g/cm ) was the real density of glass powder. The volumetric water absorption, Wv, was calculated using Eq. (3): 3
Wv =
m1 − m0 × 100% ρw × V
(3)
where m0 and V were the mass and volume of the test sample. ρw was the density of water at room temperature. m1 was the mass of the test sample immersed in deionized water for 24 h at room temperature.
3. Results and discussion 3.1. Effect of sintering temperature The properties of samples are illustrated in Table 1. Samples were sintered at atmospheric pressure. Green spheres play an important role during the foaming process. Each green sphere forms a separate space for foaming and generates small and
Table 1 The properties of samples sintered at different temperatures. Sintering temperature (°C) Bulk density (g/cm3) Volumetric water absorption (%)
660 0.257 1.3
680 0.180 1.9
690 0.157 1.4
700 0.134 3.6
720 0.128 9.3
Table 2 The carbon contents of different samples. The sample
Carbon content (wt%)
Green spheres Green spheres heated up to 700 °C Sample sintered at 700 °C
1.34 0.48 0.33
uniform cells. Another unique advantage of using green spheres is that the spheres can prevent gaseous products from escaping. Table 2 shows the carbon contents of different samples. The carbon content decreases from 1.34 wt% to 0.48 wt% when the sample is heated up to 700 °C, which indicates the fact that the organic compounds used in the preparation process of green spheres transform into carbonaceous products on incomplete pyrolysis of the polymers during the heating procedure. And mixtures of CO2 and CO are commonly produced by the oxidation of carbonaceous products [8]. The carbon content decreases to 0.33 wt% after the foaming process at 700 °C. With the increase of sintering temperature, the gaseous products produced during the sintering process increase, contributing to the decrease of bulk density. The volumetric water absorption is less than 4.0% between 660 °C and 700 °C. However, the volumetric water absorption increases sharply at temperatures higher than 700 °C, which is attributed to the open-celled microstructure. The sample sintered at 700 °C shows good integrated performance, with a uniform microstructure as shown in Fig. 1(b).
3.2. Effect of sintering procedure The schematic diagram of sintering procedure is shown in Fig. 2 (a). The sintering temperature is 700 °C and the vacuum pressure is 50 kPa. Tn is the temperature at which air in the furnace is pumped into vacuum. Fig. 2(b) shows the effect of Tn value on microstructures and properties of glass foams. The bulk density decreases as Tn value increases, while the cell size is a positive function of Tn value. With the increase of Tn value, more gaseous products are enclosed in the cells before the vacuum condition, resulting in the increase of cell size and the decrease of bulk density. Another important reason for the increase of cell size is the coalescence of cells. The photographs in Fig. 2(b) demonstrate that the coalescence of cells ultimately leads to the uneven microstructure of the foams. The volumetric water absorption has great dependence on the open cells existing in the samples. The sample with the Tn value of 700 °C has higher volumetric water absorption, which is attributed to the open cells resulting from the coalescence of cells.
Y.-N. Qu et al. / Materials Letters 166 (2016) 35–38
37
Fig. 2. (a) The schematic diagram of sintering procedure and (b) the effect of Tn value on microstructure, bulk density and volumetric water absorption of glass foams.
Fig. 3. (a) The effect of vacuum pressure on bulk density and porosity; (b) evolutions of mean cell diameter and volumetric water absorption as functions of vacuum pressure, the inset shows the photograph of sample sintered at vacuum pressure of 30 kPa; (c) relationship between compressive strength and bulk density.
3.3. Effect of vacuum pressure Samples are prepared at different vacuum pressures with the sintering temperature and Tn value of 700 °C and 680 °C, respectively. The vacuum pressure has significant influences on preparation and properties of the foams. Fig. 3(a–b) shows the evolutions of properties of glass foams as functions of vacuum pressure. The bulk density decreases with the reduction of vacuum pressure. While the mean cell diameter increases as the vacuum pressure reduces. Samples prepared under vacuum condition have lower bulk density and greater cell size, which is attributed to the fact that vacuum condition accelerates the growth of cells. Fig. 3 (b) illustrates lower volumetric absorption of the samples except for the sample sintered at vacuum pressure of 30 kPa. The high volumetric water absorption is precisely due to the open-celled microstructure resulting from the coalescence of cells. Based on
the above analyses, the vacuum pressure must be controlled to be higher than 30 kPa to obtain closed-cell foams. 3.4. Mechanical strength Fig. 3(c) illustrates the relationship between compressive strength and bulk density, indicating that the compressive strength is roughly proportional to the bulk density. The compressive strength is higher than that reported in pertinent literatures [8,16,17], resulting from the uniform microstructure. The error bars of compressive strength tend to increase with the decrease of bulk density. The main reason given for this is that the microstructure gradually becomes non-uniform with the decrease of bulk density. In addition, the influence of sample preparation becomes evident as the bulk density decreases, resulting from both the non-uniform microstructure and large cell size.
38
Y.-N. Qu et al. / Materials Letters 166 (2016) 35–38
4. Conclusions
References
Glass foams with high porosity and mechanical strength were prepared by a novel vacuum-assisted foaming technique. Both the sintering temperature and sintering procedure have significant effects on the preparation and properties of glass foams. With the reduction of vacuum pressure, the bulk density decreases, while the cell size increases. Glass foams were fabricated at vacuum pressure of 30–70 kPa, with bulk density, porosity and compressive strength values of 0.081–0.122 g/cm3, 95.2–96.8% and 0.29– 1.18 MPa, respectively. Both closed-cell and open-celled glass foams are successfully fabricated. Such glass foams with high porosity have potential applications as thermal insulation materials and sound absorption materials.
[1] C. Ohl, M. Kappa, V. Wilker, J. Am. Ceram. Soc. 94 (2011) 436–441. [2] R. Lebullenger, S. Chenu, J. Rocherullé, O. Merdrignac-Conanec, F. Cheviré, F. Tessier, et al., J. Non Cryst. Solids 356 (2010) 2562–2568. [3] V. Ducman, A. Mladenovič, J.S. Šuput, Cem. Concr. Res. 32 (2002) 223–226. [4] P. Colombo, G. Brusatin, E. Bernardo, G. Scarinci, Curr. Opin. Solid State Mater. Sci. 7 (2003) 225–239. [5] R. Taurino, I. Lancellotti, L. Barbieri, C. Leonelli, Int. J. Appl. Glass Sci. 5 (2014) 136–145. [6] R. Benzerga, V. Laur, R. Lebullenger, L.L. Gendre, S. Genty, A. Sharaiha, P. Queffelec, Mater. Res. Bull. 67 (2015) 261–265. [7] J. Bai, X. Yang, S. Xu, W. Jing, J. Yang, Mater. Lett. 136 (2014) 52–54. [8] G. Scarinci, G. Brusatin, E. Bernardo, in Cellular Ceramics: Structure, Manufacturing, Properties and Applications ed. by M. Scheffler, P. Colombo, WileyVCH, Weinheim. 2005, pp. 158-176. [9] J. König, R.R. Petersen, Y. Yue, J. Eur. Ceram. Soc. 34 (2014) 1591–1598. [10] C. Ji, D. He, L. Shen, X. Zhang, Y. Wang, A. Gupta, et al., Mater. Lett. 119 (2014) 60–63. [11] K. Renger, H. Kaufmann, Adv. Eng. Mater. 7 (2005) 117–123. [12] D. Yao, Y. Xia, K. Zuo, Y. Zeng, D. Jiang, J. Günster, J.G. Heinrich, Mater. Lett. 141 (2015) 138–140. [13] M.K. Ahn, Y.W. Moon, Y.H. Koh, H.E. Kim, J. Am. Ceram. Soc. 95 (2012) 3360–3362. [14] B. Wang, K. Matsumaru, J. Yang, Z. Fu, K. Ishizaki, Acta Mater. 60 (2012) 4185–4193. [15] J. Yang, K. Cai, X. Xi, G. Ge, Y. Huang, US Pat. 2014, p. 8845936. [16] Y. Attila, M. Güden, A. Taşdemirci, Ceram. Int. 39 (2013) 5869–5877. [17] E. Bernardo, F. Albertini, Ceram. Int. 32 (2006) 603–608.
Acknowledgments Our research work presented in this paper was supported by National Natural Science Foundation of China (51172120) and China Postdoctoral Science Foundation (2015M570094).