Effect of Organic-inorganic Crosslinking Degree on the Mechanical and Thermal Properties of Aerogels

doi:10.15541/jim20190186

Abstract

Abstract:

In all kinds of aerogels, silicon-based aerogel possesses the most comprehensive mechanism of Sol-Gel process and maturest synthesis process. In this work, different types of silicon-based aerogels were prepared via different silicon precursors including tetraethoxysilane (TEOS), methyltrimethoxysilane (MTMS), vinylmethyldimethoxysilane (VMDMS) and the mixed precursor of MTMS and dimethyldimethoxysilane (DMDMS). All samples display high specific surface area and porous microstructure. Effect of the precursor structure on the mechanical and thermal properties of final samples was deeply investigated. The results show that elastic property of silicon-based aerogels depends greatly on the crosslinking degree of their skeleton. The lower the crosslinking degree of the sample is, the better the elastic property is. Furthermore, the elastic property can be further improved by introducing hydrocarbon chains into the skeleton. Thermal conductivity of the obtained aerogels is between 0.032 and 0.041 W/(m·K) at room temperature. Their weight loss increases with the increase of the organic component in the skeleton. Superior mechanical and thermal properties enable silicon-based aerogels to be promising candidates for thermal insulation and energy storage.

Key words: aerogel, skeleton structure, mechanical property, thermal property

CLC Number:

O648

ZHANG Ze,WANG Xiaodong,SHEN Jun. Effect of Organic-inorganic Crosslinking Degree on the Mechanical and Thermal Properties of Aerogels[J]. Journal of Inorganic Materials, 2020, 35(4): 454-460.

Figures/Tables 9

Fig. 1 Photograph of silicon-based aerogels Samples 1-4 are from left to right in sequence

Table 1 Physical properties of silicon-based aerogels

Sample	ρ^a/(g·cm^-3)	S_BET^b/(m²·g^-1)	d^c/nm	ε^d/(cm³·g^-1)	λ^e/(W·m^-1·K^-1)	R^f/%	Y^g/MPa
1	0.194	843	20.22	4.900	0.036	10%	0.71
2	0.192	1165	18.23	3.600	0.034	20%	0.82
3	0.156	34	1.72	0.025	0.041	27%	9.54×10^-3
4	0.188	1403	16.31	3.700	0.032	100%	4.51

Fig. 2 SEM images of silicon-based aerogels (a-d) represent samples 1-4, respectively

Fig. 3 N2 adsorption/desorption isotherms (a-b) and BJH pore size distribution (c-d) of silicon-based aerogels

Fig. 4 FT-IR spectra of silicon-based aerogels

Fig. 5 Skeleton structure of 4 silicon-based aerogels obtained from (a) TEOS, (b) MTMS, (c) mixed precursor of MTMS and DMDMS, and (d) VMDMS

Fig. 6 29Si MAS NMR spectra of silicon-based aerogels

Fig. 7 TG curves of silicon-based aerogels

Fig. 8 Stress-strain curves of silicon-based aerogels (a) Sample 1, (b) Sample 2, (c) Sample 3, (d) Sample 4. Insets in (a-d) show the skeleton structure of corresponding aerogels

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