Gradient Porous Silicon Nitride by Slip Casting and Vacuum Foaming

doi:10.15541/jim20160077

Abstract

Abstract:

Gradient porous silicon nitride was fabricated by a combination method of slip casting and vacuum foaming. Firstly, foaming agent was added into Si₃N₄ aqueous slurry, then the uniformly stirred slurry was poured into the mold with plaster as base. Under low pressure and steady temperature, a green body with gradient pores was formed. Based on our research, the gradient structure and porosity were greatly influenced by the vacuum pressure. With the pressure decrease from 80 kPa to 9 kPa, the porosity increased from 59.01% to 80.85% and the gradient structure became more noticeable. When the pressure was 80 kPa, the sample obtained a uniform pore structure. After the pressure being decreased to 9 kPa, the sample obtained dispersed pore size distribution including values of 0.5, 20, 30, 40, 60, 100 and 200 μm measured through mercury intrusion method. Gradient porous ceramics with adjustable porosity and pore size distribution, as well as achievable complex shape and large scale, may fabricate through this simply and low cost method.

Key words: gradient, foaming, porous, silicon nitride

CLC Number:

TQ174

DENG Jian, YAO Dong-Xu, XIA Yong-Feng, ZUO Kai-Hui, YIN Jin-Wei, ZENG Yu-Ping. Gradient Porous Silicon Nitride by Slip Casting and Vacuum Foaming[J]. Journal of Inorganic Materials, 2016, 31(8): 865-868.

Figures/Tables 7

Fig. 1 Flow chart of slip casting and vacuum foaming method for gradient porous silicon nitride

Fig. 2 Process of forming gradient structure

Fig. 3 XRD patterns of green body (a) and sample prepared under 30 kPa atmosphere pressure (b)

Table 1 Densities and porosities of samples prepared under different atmosphere pressures

Samples	1	2	3	4
Pressure /kPa	80	50	30	9
Density /(g﹒cm^-3)	1.41	0.84	0.61	0.66
Porosity /%	59.01	75.50	82.20	80.85

Fig. 4 Optical microscopy morphologies of samples prepared under different atmosphere pressures(a) 80 kPa; (b) 50 kPa; (c) 30 kPa; (d) 9 kPa

Fig. 5 SEM images of different samples(a, b, c) Sample1; (d, e, f) Sample 4. The arrow in (e) shows the “window” forming on the foam surface

Fig. 6 Pore diameter distribution of samples prepared under different atmosphere pressures

References 16

[1]	PETZOW G., HERRMANN M.Silicon nitride ceramics.Structure and Bonding, 2002, 102(1): 47-167.
[2]	ZENG Y P, JIANG D L, WATANABLE T.Fabrication and properties of tape-cast laminated and functionally gradient alumina-titanium carbide materials.Journal of the American Ceramic Society, 2000, 83(12): 2999-3003.
[3]	XIA Y F, ZENG Y P, JIANG D L.Mechanical and dielectric properties of porous Si3N4 ceramics using PMMA as pore former.Ceramics International, 2011, 37(8): 3775-3779.
[4]	YAO D X, ZENG Y P, ZUO K H, et al.The effects of BN addition on the mechanical properties of porous Si3N4/BN ceramics prepared via nitridation of silicon powder.Journal of the American Ceramic Society, 2011, 94(3): 666-670.
[5]	ZHANG F, QI C X, WANG S, et al.A study on preparation of cordierite gradient pores porous ceramics from rectorite.Solid State Sciences, 2011, 13(5): 929-933.
[6]	BRETCANU O, SAMAILLE C, BOCCACCINI A R.Simple methods to fabricate Bioglass (R)-derived glass-ceramic scaffolds exhibiting porosity gradient.Journal of Materials Science, 2008, 43(12): 4127-4134.
[7]	KINEMUCHI Y, WATARI K, UCHIMURA S.Grading porous ceramics by centrifugal sintering.Acta Materialia, 2003, 51(11): 3225-3231.
[8]	XIANGMING L, PUTE W, DELAN Z.Fabrication and properties of porous Si3N4-SiO2 ceramics with dense surface and gradient pore distribution.Ceramics International, 2014, 40(3): 5079-5084.
[9]	ZHANG S X, ONG Z Y, LI T, et al.Ceramic composite components with gradient porosity by powder injection moulding.Materials & Design. 2010, 31(6): 2897-2903.
[10]	KATO M, GOTO Y, FUKASAWA T.Rheological characterization of beta-sialon and Si3N4 slips and fabrication of multilayered composites by slip casting.Journal of Materials Science Letters, 1997, 16(24): 2055-2057.
[11]	YAO D X, XIA Y F, ZUO K H, et al.Gradient porous silicon nitride prepared via vacuum foaming and freeze drying.Materials Letters, 2015, 141(1): 138-140.
[12]	GARRN I, REETZ C, BRANDES N, et al.Clot-forming: the use of proteins as binders for producing ceramic foams.Journal of the European Ceramic Society, 2004, 24(3): 579-587.
[13]	JUILLERAT F K, GONZENBACH U T, ELSER P, et al.Microstructural control of self-setting particle-stabilized ceramic foams.Journal of the American Ceramic Society, 2011, 94(1): 184-190.
[14]	SEPULVEDA P, BINNER J G P. Processing of cellular ceramics by foaming and in situ polymerization of organic monomers.Journal of the European Ceramic Society, 1999, 19(12): 2059-2066.
[15]	STUDART A R, GONZENBACH U T, TERVOORT E, et al.Processing routes to macroporous ceramics: a review.Journal of the American Ceramic Society, 2006, 89(6): 1771-1789.
[16]	YIN L Y, ZHOU X G, YU J S, et al.Protein foaming method to prepare Si3N4 foams by using a mixture of egg white protein and whey protein isolate.Ceramics International, 2014, 40(8): 11503-11509.