Low thermal conductivity and high porosity ZrC and HfC ceramics prepared by in-situ reduction reaction/partial sintering method for ultrahigh temperature applications

doi:10.1016/j.jmst.2019.05.044

Abstract

Abstract:

Porous ultra-high temperature ceramics (UHTCs) are potential candidates as high-temperature thermal insulation materials. However, high thermal conductivity is the main obstacle to the application of porous UHTCs. In order to address this problem, herein, a new method combining in-situ reaction and partial sintering has been developed for preparing porous ZrC and HfC with low conductivity. In this process, porous ZrC and HfC are directly obtained from ZrO₂/C and HfO₂/C green bodies without adding any pore-forming agents. The release of reaction gas can not only increase the porosity but also block the shrinkage. The as-prepared porous ZrC and HfC exhibit homogeneous porous microstructure with grain sizes in the range of 300-600?nm and 200-500?nm, high porosity of 68.74% and 77.82%, low room temperature thermal conductivity of 1.12 and 1.01?W·m^-1?K^-1, and compressive strength of 8.28 and 5.51?MPa, respectively. These features render porous ZrC and HfC promising as light-weight thermal insulation materials for ultrahigh temperature applications. Furthermore, the feasibility of this method has been demonstrated and porous NbC, TaC as well as TiC have been prepared by this method.

Key words: Ultrahigh temperature ceramics (UHTCs), Transition metal carbides, Porous ceramics, ZrC and HfC, Thermal conductivity, Mechanical properties

Heng Chen, Huimin Xiang, Fu-Zhi Dai, Jiachen Liu, Yanchun Zhou. Low thermal conductivity and high porosity ZrC and HfC ceramics prepared by in-situ reduction reaction/partial sintering method for ultrahigh temperature applications[J]. J. Mater. Sci. Technol., 2019, 35(12): 2778-2784.

Figures/Tables 8

Fig. 1. (a) Schematic illustration of the conventional method for manufacturing porous UHTCs, (b) schematic illustration of carbothermal reaction method for preparing ZrC and HfC nano powders, (c) schematic illustration of the novel method combining in-situ reaction and partial sintering process for preparing porous ZrC and HfC.

Fig. 2. (a) The linear shrinkage, linear shrinkage rate, TG and DTG curves recorded during the heating of ZrO2/C green body, (b) the linear shrinkage, linear shrinkage rate, TG and DTG curves recorded during the heating of HfO2/C green body.

Fig. 3. The linear shrinkage, linear shrinkage rate, TG and DTG curves recorded during the heating of (a) Nb2O5/C, (b) Ta2O5/C and (c) HfO2/C green bodies.

Fig. 4. Photographs and XRD patterns of as-prepared porous ZrC (a) and HfC (b).

Table 1 Porosity, sintered density, theoretical density, radical shrinkage and compressive strength of as-prepared porous ZrC and HfC UHTCs.

Sample	Porosity (%)	Sintered density (g·cm^-3)	Theoretical density [34] (g·cm^-3)	Radial shrinkage (%)	Compressive strength (MPa)
Porous ZrC ceramic	68.74	2.06	6.59	21.97	8.28
Porous HfC ceramic	77.82	2.82	12.67	20.30	5.51

Fig. 5. SEM micrographs of (a) and (b) porous ZrC ceramics with the sintered density of 2.06?g/cm3, (c) and (d) porous HfC with the sintered density of 2.82?g/cm3.

Fig. 6. SEM micrographs of (a) porous NbC ceramics with the sintered density of 1.62?g/cm3, (b) porous TaC ceramics with the sintered density of 2.88?g/cm3, (c) porous TiC ceramics with the sintered density of 1.03?g/cm3.

Fig. 7. Thermal conductivity (κ) and thermal diffusivity (α) of porous (a) ZrC and (b) HfC.

References

[1]	P. Colombo, Science, 322(2008), pp. 381-383.
[2]	G.L. Messing, A.J. Stevenson, Science, 322(2008), pp. 383-384.
[3]	D.J. Green, P. Colombo, MRS Bull., 28(2003), pp. 296-300.
[4]	J. Wu, C. Ruan, Y. Ma, Y. Wang, Y. Luo, J. Mater. Sci. Technol., 34(2018), pp. 503-507.
[5]	Y.G. Tong, S.X. Bai, K. Chen, Ceram. Int., 38(2012), pp. 5723-5730.
[6]	C. Nachiappan, L. Rangaraj, C. Divakar, V. Jayaram, J. Am. Ceram. Soc., 93(2010), pp. 1341-1346.
[7]	Y.C. Zhou, H.M. Xiang, Z.H. Feng, Z.P. Li, J. Am. Ceram. Soc., 99(2016), pp. 2110-2119.
[8]	A.I. Gusev, A.N. Zyryanova, Phys. Status Sol. A, 177(2000), pp. 419-437.
[9]	E. Wuchina, E. Opila, M. Opeka, W. Fahrenholtz, I. Talmy, Electrochem. Soc. Interface, 16(2007), p. 30.
[10]	K. Yada, H. Masaoka, Y. Shoji, T. Tanji, J. Electron. Microsc. Tech., 12(1989), pp. 252-261.
[11]	W.G. Fahrenholtz, E.J. Wuchina, W.E. Lee, Y.C. Zhou, Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications, John Wiley &Sons, Inc., New Jersey (2014), pp. 1-5.
[12]	Y.C. Zhou, H.M. Xiang, Z.H. Feng, Z.P. Li, J. Mater. Sci. Technol., 31(2015), pp. 285-294.
[13]	R. Savino, M.D.S. Fumo, L. Silvestroni, S. Diletta, J. Eur. Ceram. Soc., 28(2008), pp. 1899-1907.
[14]	E. Landi, D. Sciti, C. Melandri, V. Medri, J. Eur. Ceram. Soc., 33(2013), pp. 1599-1607.
[15]	J.M. Jiang, S. Wang, W. Li, Z.H. Chen, J. Alloys Compd., 695(2017), pp. 2295-2300.
[16]	H.P. Yuan, J.G. Li, Q. Shen, L.M. Zhang, Int. J. Refract. Met. Hard Mat., 36(2013), pp. 225-231.
[17]	E. Sani, L. Mercatelli, J.L. Sans, L. Silvestroni, D. Sciti, Opt. Mater., 36(2013), pp. 163-168.
[18]	X.F. Wang, H.M. Xiang, X. Sun, J.C. Liu, F. Hou, Y.C. Zhou, J. Am. Ceram. Soc., 98(2015), pp. 2234-2239.
[19]	Q.Q. Guo, H.M. Xiang, X. Sun, X.H. Wang, Y.C. Zhou, J. Eur. Ceram. Soc., 35(2015), pp. 3411-3418.
[20]	H. Chen, H.M. Xiang, F.Z. Dai, J.C. Liu, Y.C. Zhou, J. Mater. Sci. 10.1016/j.jmst.2018.09.071.
[21]	H.W. Russell, J. Am. Ceram. Soc., 18(1935), pp. 1-5.
[22]	A. Eucken, Forsch. Gebiete Ingenieurw., 19(1932), pp. 353-360.
[23]	A.L. Loeb, J. Am. Ceram. Soc., 37(1954), pp. 96-99.
[24]	J. Francl, W.D. Kingery, J. Am. Ceram. Soc., 37(1954), pp. 99-107.
[25]	G. Soyez, J.A. Eastman, L.J. Thompson, G.R. Bai, P.M. Baldo, A.W. McCormick, Appl.Phys. Lett., 77(2000), pp. 1155-1157.
[26]	G.H. Geiger, D.R. Poirier. MA, 1973. pp.190.
[27]	L.E. Toth ,Transition Metal Carbides and Nitrides, Academic Press, New York (1971).
[28]	J.X. Liu, Y.M. Kan, G.J. Zhang, J. Am. Ceram. Soc., 93(2010), pp. 980-986.
[29]	S.K. Sun, G.J. Zhang, W.W. Wu, J.X. Liu, T. Suzuki, Y. Sakka, Scr. Mater., 69(2013), pp. 139-142.
[30]	I. Barin, Thermochemical Data of Pure Substances, VCH(1989).
[31]	D.D. Jayaseelan, N. Kondo, M.E. Brito, T. Ohji, J. Am. Ceram. Soc., 85(2002), pp. 267-269
[32]	Y. Yang, Y. Wang, W. Tian, Z. Wang, C.G. Li, Y. Zhao, H.M. Bian, Scr. Mater., 60(2009), pp. 578-581.
[33]	V. Medri, M. Mazzocchi, A. Bellosi, Int. J. Appl. Ceram. Technol., 8(2011), pp. 815-823.
[34]	H.O. Pierson, Handbook of Refractory Carbides and Nitrides, Noyes publications, Westwood, NJ(1996), pp. 56